| title: | Study of magnetic lattice for a quasi-isochronous ring |
| journal: | Particle Accelerators |
| vol-pages: | 65-76 |
| year: | 1994 |
| authors: | A. Amiry,C. Pellegrini,E. Forest,D. Robin |
| abstract: | Quasi-isochronous rings (QIRs) have been considered for electron-positron colliders to obtain large luminosity with a small average beam current. This approach offers the advantage of minimizing vacuum and RF system problems, and multibunch instability effects. In this paper, we review the basic physics of a QIR, the condition for stable single-particle motion, and the dynamic aperture. The collider we discuss is a Phi( Phi ) factory with a single ring and beam energy of 510 MeV. This ring uses a very strong focusing of the electron and positron beams at the interaction point, i.e., a beta function in the millimeter range; and a momentum compaction variable over a large range, of -0.008 to +0.005, to control the bunch length. It has a luminosity of 10(33) cm(-2) s(-1), average current smaller than 1 A, and a perimeter of 32.7 meter. Its transverse chromaticities and second-order momentum compaction are set to zero by utilizing three families of the sextupoles. The QIR dynamic aperture is calculated using a new computer code, KRAKPOT, written explicitly for small rings. |
| title: | Two-beam operation of the 1.5 GeV electron-positron storage ring Adone |
| journal: | Lettere Al Nuovo Cimento |
| vol-pages: | 729-37 |
| year: | 1969 |
| authors: | F. Amman,R. Andreani,M. Bassetti,M. Bernardini,A. Cattoni,V. Chimenti,G. Corazza,D. Fabiani,E. Felenghi,A. Massarotti,C. Pellegrini,M. Placidi,M. Puglisi,F. Soso,S. Tazzari,F. Tazzioli,G. Vignola |
| abstract: | Two-beam operation has recently been successfully achieved at Adone, the 1.5 GeV electron-positron storage ring of the Laboratori Nazionali di Frascati del CNEN the first results, which are in good agreement with the design aim, are reported. Measurements of the luminosity (defined as the interaction rate in a crossing region for an event having unit cross-section) have been performed observing the interaction rate of events with known cross-section (e+ e- single bremsstrahlung and e+ e- scattering at small angles). The luminosity has also been computed from beam currents and transverse dimensions. |
| title: | Horizontal Phase-Space Distortions Arising from Magnetic Pulse Compression of an Intense, Relativistic Electron Beam |
| journal: | Physical Review Letters |
| vol-pages: | 074803 |
| year: | 2003 |
| authors: | S. Anderson,J. Rosenzweig,P. Musumeci,M. Thompson |
| abstract: | We report detailed measurements of the transverse phase space distortions induced by magnetic chicane compression of a high brightness, relativistic electron beam to subpicosecond length. A strong bifurcation in the phase space is observed when the beam is strongly compressed. This effect is analyzed using several computational models and is correlated to the folding of longitudinal phase space. The impact of these results on current research in collective beam effects in bending systems and implications for future short wavelength free-electron lasers and linear colliders are discussed. |
| title: | Nonequilibrium transverse motion and emittance growth in ultrarelativistic space-charge dominated beams |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 094201 |
| year: | 2000 |
| authors: | S. Anderson,J. Rosenzweig |
| abstract: | The transverse dynamics of space-charge dominated beams are investigated both analytically and computationally, in order to understand the mechanisms for emittance oscillations and growth due to nonlinear space-charge fields. This work explores the role of space-charge dominated equilibrium and its relationship to phase space wave breaking, which is responsible for the irreversible emittance growth in these systems. The physics of both coasting and accelerating beams are examined in order to illuminate the most effective approaches to beam handling during the emittance compensation process as well as during subsequent beam transport. These results are discussed within the context of recent ultrahigh brightness RF photoinjector designs. (20 References). |
| title: | Space-charge effects in high brightness electron beam emittance measurements |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 014201 |
| year: | 2002 |
| authors: | S. Anderson,J. Rosenzweig,G. Le Sage,J. Crane |
| abstract: | The measurement of emittance in space-charge dominated, high brightness beam systems is investigated from conceptual, computational, and experimental viewpoints. As the self-field-induced collective motion in the low energy, high brightness beams emitted from photoinjector rf guns are more important in determining the macroscopic beam evolution than thermal spreads in transverse velocity; traditional methods for phase space diagnosis fail in these systems. We discuss the role of space charge forces in a traditional measurement of transverse emittance, the quadrupole scan. The mitigation of these effects by use of multislit- or pepper-pot-based techniques is explained. The results of a direct experimental comparison between quadrupole scanning and slit-based determination of the emittance of a 5 MeV high brightness electron beam are presented. These data are interpreted with the aid of both envelope and multiparticle simulation codes. It is shown that the ratio of the beam's beta function to its transverse plasma wavelength plays a central role in the quadrupole scan results. Methods of determining the presence of systematic errors in quadrupole scan data are discussed. |
| title: | Propagation of short electron pulses in a plasma channel |
| journal: | Physical Review Letters |
| vol-pages: | 81-84 |
| year: | 1998 |
| authors: | N. Barov,M. Conde,W. Gai,J. Rosenzweig |
| abstract: | We report the near-steady-state propagation over long distance of a 25 psec, tightly focused relativistic electron beam which creates, by radial ejection of plasma electrons, a focusing ion channel in a plasma of electron density smaller than the beam. A dense beam core, close in radius to the injected beam, which was nearly matched to the ion focusing strength, is observed at the plasma exit. Time-resolved imaging confirms that this core is situated in the trailing half of the beam, as predicted by analytical and computer models. We discuss the impact of these results on plasma wake field acceleration schemes. (16 References). |
| title: | Propagation of short electron pulses in underdense plasmas |
| journal: | Physical Review E |
| vol-pages: | 4407-16 |
| year: | 1994 |
| authors: | N. Barov,J. Rosenzweig |
| abstract: | Dense relativistic electron beams traversing a plasma, in what is known as the underdense, or ion focusing, regime experience a strong, linear transverse restoring force. This force arises from the nearly immobile ions which form a channel of uncompensated positive charge when the plasma electrons are ejected in response to the introduction of the beam charge. This phenomenon can be used for focusing the electron beam to very high densities over long propagation distances. Several schemes have been proposed, including the nonlinear plasma wake-field accelerator, the adiabatic plasma lens, and the ion-channel laser, whose viability is based on this focusing effect for very short pulse, high current electron beams propagating in plasma. In this paper we examine, analytically and numerically, the self-consistent requirements on plasma density, beam current, length, and transverse emittance which must be satisfied in order for ion-channel formation and near equilibrium beam propagation to exist over the majority of the length of the electron beam. The dynamics of the beam-plasma system are modeled by a simultaneous solution of the plasma electron cold-fluid equations, and the Maxwell-Vlasov equation governing the beam's thermal equilibrium. The effects of introducing a strong axial magnetic field on the plasma response and beam equilibria are examined. In addition to developing criteria for self-consistent equilibrium focusing, a time-dependent analysis where the beam particles are treated as mobile particles in cells is developed in order to study the dynamical approach of this equilibrium. Inherently time-dependent phenomena, such as matching of the beam into the plasma and adiabatic lenses, are then examined with this method. |
| title: | Observation of plasma wakefield acceleration in the underdense regime |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 011301 |
| year: | 2000 |
| authors: | N. Barov,J. Rosenzweig,M. Conde,W. Gai,J. Power |
| abstract: | Initial experiments which have explored the physics of the underdense (blowout) regime of the plasma wakefield accelerator (PWFA) at the Argonne Wakefield Accelerator facility are reported. In this regime, the relativistic electron beam is denser than the plasma, causing the beam channel to completely rarefy, and leaving a high quality accelerating region which also contains a uniform ion column. This ion column in turn allows the drive and accelerating beams to be well guided over many initial beam beta-function lengths. The results of these experiments, which have taken place over several years, are reviewed. Notable achievements in the course of these studies include the creation and measurement of drive and witness beam generated in an rf photoinjector, as well as previously published studies on drive beam guiding in the underdense regime. In addition, these experiments allowed measurement of both beam energy loss and gain, at a maximum average rate of 25 MeV/m in this regime of the PWFA, which is consistent with a peak acceleration gradient of 62 MeV/m in the excited waves. Difficulties associated with this type of experiment are discussed, as are prospects for mitigating these difficulties and achieving high gradient acceleration in planned future experiments. |
| title: | Feasibility study of a storage ring for a high-power XUV free-electron laser |
| journal: | Particle Accelerators |
| vol-pages: | 223-66 |
| year: | 1986 |
| authors: | J. Bisognano,S. Chattopadhyay,M. Cornacchia,A. Garren,K. Halbach,A. Jackson,K. Kim,H. Lancaster,J. Peterson,M. Zisman,C. Pellegrini,G. Vignola |
| abstract: | A high-gain free-electron lase (FEL), operating in a special by-pass of a storage ring, can provide tens of megawatts of coherent power at wavelengths shorter than 1000 AA. The requirements on beam quality are demanding-a few hundred amperes of peak current in an emittance of about 10/sup -8/ m-rad with a relative energy spread of about 10/sup -3/. Designing an electron storage ring with the required characteristics involves a comprehensive analysis of the restrictions arising from, and relationships between, the FEL physics, the multiparticle beam phenomena, and the ring lattice structure. A summary of such a study is reported and some design examples are given. (39 References). |
| title: | Hamiltonian model of a free electron laser |
| journal: | Optics Communications |
| vol-pages: | 55-60 |
| year: | 1987 |
| authors: | R. Bonifacio,F. Casagrande,C. Pellegrini |
| abstract: | Both the Compton and the Raman regimes of a free electron laser are described by a relativistic Hamiltonian which originates the evolution equations for 2N+2 canonically conjugate electron and field variables, with the space coordinate as the independent variable. Space charge and field contribution to electron transverse velocity are included. Scaled variables are introduced which allow for a description of the behaviour of the system in terms of a single electron-beam parameter. (16 References). |
| title: | Spectrum, temporal structure, and fluctuations in a high-gain free-electron laser starting from noise |
| journal: | Physical Review Letters |
| vol-pages: | 70-3 |
| year: | 1994 |
| authors: | R. Bonifacio,L. De Salvo,P. Pierini,N. Piovella,C. Pellegrini |
| abstract: | We study the time structure, the frequency composition, and the shot to shot fluctuations of the radiation emitted by a free-electron laser starting from shot noise in the electron beam longitudinal distribution, taking into account slippage and finite bunch length effects. We find a very different behavior when the bunch length, l/sub b/, is much longer than the cooperation length, l/sub c/, or of the order of a few l/sub c/. The field evolution is dominated by slippage effects in both cases, and shows the presence of superradiant spikes. (14 References). |
| title: | Collective instabilities and high-gain regime in a free electron laser |
| journal: | Optics Communications |
| vol-pages: | 373-8 |
| year: | 1984 |
| authors: | R. Bonifacio,C. Pellegrini,L. Narducci |
| abstract: | The authors study the behavior of a free electron laser in the high gain regime, and the conditions for the emergence of a collective instability in the electron beam-undulator-field system. The authors' equations, in the appropriate limit, yield the traditional small gain formula. In the nonlinear regime, numerical solutions of the coupled equations of motion support the correctness of their proposed empirical estimator for the build-up time of the pulses, and indicate the existence of optimum parameters for the production of high peak-power radiation. (11 References). |
| title: | The classical theory of the transverse optical klystron for a nonmonoenergetic beam |
| journal: | Journal of Applied Physics |
| vol-pages: | 18-26 |
| year: | 1985 |
| authors: | I. Boscolo,M. Leo,R. Leo,G. Soliani,V. Stagno,C. Pellegrini |
| abstract: | In this paper the classical theory of the transverse optical klystron is presented. The gain is obtained by solving analytically the Vlasov equation which governs the evolution of the electron beam along the undulator magnet. The initial energy distribution of the electron beam is assumed gaussian. Both the small signal and the saturation regime are investigated. (19 References). |
| title: | A study on the choice of parameters for a high energy electron ring accelerator |
| journal: | Particle Accelerators |
| vol-pages: | 45-56 |
| year: | 1971 |
| authors: | C. Bovet,C. Pellegrini |
| abstract: | The production of high energy (multi-GeV) proton beams by an electron ring accelerator is considered. Both the final energy and intensity of the proton beam depend on the choice of parameters for the electron ring. Possible sets of parameters, consistent with all the known requirements of ring stability, and which optimize the energy and (or) the intensity of the proton beam, are presented. (19 References). |
| title: | Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 122402 |
| year: | 2001 |
| authors: | R. Carr,M. Cornacchia,P. Emma,H. Nuhn,B. Poling,R. Ruland,E. Johnson,G. Rakowsky,J. Skaritka,S. Lidia,P. Duffy,M. Libkind,P. Frigola,A. Murokh,C. Pellegrini,J. Rosenzweig,A. Tremaine |
| abstract: | The visible-infrared self-amplified spontaneous emission amplifier (VISA) free electron laser (FEL) is an experimental device designed to show self-amplified spontaneous emission (SASE) to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800?600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70?85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than ±50 µm per field gain length. |
| title: | First observation of luminosity-driven extraction using channeling with a bent crystal |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 022801 |
| year: | 1998 |
| authors: | R. Carrigan,D. Chen,G. Jackson,N. Mokhov,C. Murphy,S. Baker,S. Bogacz,D. Cline,S. Ramachandran,J. Rhoades,J. Rosenzweig,A. Asseev,R. Biryukov,A. Taratin,J. Ellison,A. Khanzadeev,T. Prokofieva,V. Samsonov,G. Solodov,B. Newberger,E. Tsyganov,H. Shih,W. Gabella,B. Cox,V. Golovatyuk,A. McManus |
| abstract: | Luminosity-driven channeling extraction has been observed for the first time using a 900 GeV circulating proton beam at the superconducting Fermilab Tevatron. The extraction efficiency was found to be about 30%. A 150 kHz beam was obtained during luminosity-driven extraction with a tolerable background rate at the collider experiments. A 900 kHz beam was obtained when the background limits were doubled. This is the highest energy at which channeling has been observed. |
| title: | Beam extraction studies at 900 GeV using a channeling crystal |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 043501 |
| year: | 2002 |
| authors: | R. Carrigan,D. Chen,G. Jackson,N. Mokhov,C. Murphy,S. Baker,S. Bogacz,D. Cline,S. Ramachandran,J. Rhoades,J. Rosenzweig,A. Asseev,R. Biryukov,A. Taratin,J. Ellison,A. Khanzadeev,T. Prokofieva,V. Samsonov,G. Solodov,B. Newberger,E. Tsyganov,H. Shih,W. Gabella,B. Cox,V. Golovatyuk,A. McManus |
| abstract: | Luminosity-driven channeling extraction has been observed for the first time in a 900 GeV study at the Fermilab Tevatron. This experiment, Fermilab E853, demonstrated that useful TeV level beams can be extracted from a superconducting accelerator during high luminosity collider operations without unduly affecting the background at the collider detectors. Multipass extraction was found to increase the efficiency of the process significantly. The beam extraction efficiency was about 25%. Studies of time dependent effects found that the turn-to-turn structure was governed mainly by accelerator beam dynamics. Based on the results of this experiment, it is feasible to construct a parasitic 5?10 MHz proton beam from the Tevatron collider. |
| title: | Final focusing and enhanced disruption from an underdense plasma lens in a linear collider |
| journal: | Physical Review D |
| vol-pages: | 923?926 |
| year: | 1989 |
| authors: | P. Chen,S. Rajagopalan,J. Rosenzweig |
| abstract: | In this work we examine the viability of employing an underdense plasma lens as a final focusing method for a linear e+e- collider. The underdense plasma lens is superior to the overdense lens in that it improves focusing linearity and background event rate, but works well only for electrons. We thus consider the interaction of an e- beam which is smaller than the e+ beam at collision, a case we term "bootstrap disruption." The potential luminosity enhancement is determined by analysis of the lens optics and simulation of the bootstrap disruption. |
| title: | A high-luminosity BB factory linear collider using positron recirculation and recovery |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 297-302 |
| year: | 1990 |
| authors: | D. Cline,C. Pellegrini |
| abstract: | The authors describe an asymmetric linear collider BB factory scheme that offers a possible solution to most of the problems encountered in the design of BB factories to operate at the Upsilon (4S) energy. A key feature of this collider is the recirculation and recovery of the positrons and the asymmetric energy of the collider to better achieve the search for CP violation in the B system. (8 References). |
| title: | A study on the conditions required for the transverse stability of a coasting beam in proton storage rings |
| journal: | Particle Accelerators |
| vol-pages: | 147-68 |
| year: | 1982 |
| authors: | M. Cornacchia,C. Pellegrini |
| abstract: | A theory is developed that allows calculation of the threshold current of a coasting beam in a circular accelerator or storage ring for an arbitrary frequency versus momentum curve. This theory is applied to the simple case of a parabolic term in the curve, for which an analytical solution of the stability problem is obtained. The general case of an arbitrary frequency distribution is then solved numerically, and the solution used to study the stability of a coasting beam in a high-energy proton storage ring like ISABELLE during the stacking process and for a full-intensity beam. This is done for different momentum distribution curves and includes the effect of the nonlinear space-charge term and of up to sixteen independent magnetic multipoles. The algorithm allows calculation of both the number and the strength of the magnetic multipoles needed to provide a stable beam of the desired current. (8 References). |
| title: | High-energy inverse free-electron-laser accelerator |
| journal: | Physical Review A |
| vol-pages: | 2813-23 |
| year: | 1985 |
| authors: | E. Courant,C. Pellegrini,W. Zakowicz |
| abstract: | The authors study the inverse free-electron-laser (IFEL) accelerator and show that it can accelerate electrons to the few hundred GeV region with average acceleration rates of the order of 200 MeV/m. Several possible accelerating structures are analyzed, and the effect of synchrotron-radiation losses is studied. The longitudinal phase stability of accelerated particles is also analyzed. A Hamiltonian description, which takes into account the dissipative features of the IFEL accelerator, is introduced to study perturbations from the resonant acceleration. Adiabatic invariants are obtained and used to estimate the change of the electron phase-space density during the acceleration process. (22 References). |
| title: | Plasma electron fluid motion and wave breaking near a density transition |
| journal: | Physical Review E |
| vol-pages: | 016501 |
| year: | 2002 |
| authors: | R. England,J. Rosenzweig,N. Barov |
| abstract: | Recently, Suk, Barov, and Rosenzweig [Phys. Rev. Lett. 86, 1011 (2001)] proposed a scheme for trapping background electrons in a plasma wake field using a sudden downward transition in the background ion density, where the density transition length is small compared to the plasma skin depth. In the present paper we present a fluid dynamical description of this mechanism that is self-consistent up to the point of wave breaking. A one-dimensional nonlinear relativistic second-order differential equation is derived for the electron fluid velocity in Lagrangian coordinates. Numerical integrations of this equation are used to map out the regions of parameter space in which wave breaking occurs and to determine the extent of the downstream region of plasma involved in wave breaking. Comparisons with one-dimensional particle-in-cell (PIC) simulations show that the onset of trapping occurs at the parameter values where wave breaking begins in the fluid analysis, but that the downstream extent of plasma involved in wave breaking is not a reliable predictor of the number of trapped particles. The PIC simulations also reveal that particles initially located on the upstream side of the density transition may become trapped, although these particles do not participate in wave breaking in the fluid description. |
| title: | Experimental Demonstration of Wake-Field Effects in Dielectric Structures |
| journal: | Physical Review Letters |
| vol-pages: | 2756-58 |
| year: | 1988 |
| authors: | W. Gai,P. Schoessow,B. Cole,R. Konecny,J. Norem,J. Rosenzweig,J. Simpson |
| abstract: | We have measured the wake fields induced by short, intense relativistic electron bunches in a slow-wave structure consisting of a dielectric-lined tube, as a test of the dielectric wake-field acceleration mechanism. These fields were used to accelerate a second electron bunch which followed the driving bunch at a variable distance. Results are presented for different dielectrics and beam intensities, and are compared with theoretical predictions. |
| title: | Theory of a free-electron laser with a Gaussian optical undulator |
| journal: | IEEE Journal of Quantum Electronics |
| vol-pages: | 1557-66 |
| year: | 1988 |
| authors: | J. Gallardo,R. Fernow,R. Palmer,C. Pellegrini |
| abstract: | A theoretical study of the possibility of a free-electron laser in the XUV and soft X-ray region of the spectrum, using a counterpropagaing CO/sub 2/ laser beam as an undulator, is presented. A one-dimensional model is used to evaluate the single-pass power gain of such a device. The detrimental effects due to the energy speed, emittance of the electron beam, and the diffraction of the electromagnetic undulator are explicitly incorporated in the formalism. An oscillator experiment is also considered. The solutions of the optical pulse evolution equation in the weak field, low gain, and long-electron-pulse regimes are all derived. (27 References). |
| title: | Optical klystron configuration for a high gain X-ray free-electron laser |
| journal: | Optics Communications |
| vol-pages: | 45-8 |
| year: | 1990 |
| authors: | J. Gallardo,C. Pellegrini |
| abstract: | The authors present theory and numerical simulations of the performance of an X-ray free-electron laser in the amplified spontaneous emission mode with an optical klystron undulator configuration. This device can produce picosecond pulses of high brightness with a significantly shorter undulator than a conventional FEL. (13 References). |
| title: | TREDI: fully 3D beam dynamics simulation of RF guns, bendings and FELs |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 443-4 |
| year: | 1999 |
| authors: | L. Giannessi,P. Musumeci,M. Quattromini |
| abstract: | We describe a three-dimensional code modelling the propagation of charged beams in accelerator devices. The inclusion of space charge fields is taken into account by means of the Lienard-Wiechert retarded potentials. As an illustration of the capabilities of the program, the results of a simulation are given that, describe the beam dynamics from the cathode to the undulator through the whole accelerating system. Evidence of bunching in the undulator, as an indication of SASE is observed. |
| title: | Time and frequency domain analysis of superradiant coherent synchrotron radiation in a waveguide free-electron laser |
| journal: | Physical Review Letters |
| vol-pages: | 1192-5 |
| year: | 1994 |
| authors: | A. Gover,F. Hartemann,G. Le Sage,N. Luhmann,R. Zhang,C. Pellegrini |
| abstract: | The coherent synchrotron radiation process in a waveguide is theoretically investigated. A single, short bunch propagating through a wiggler is considered. In a waveguide, two very distinct regimes are possible. At grazing, where the beam velocity matches the wave group velocity, the bunch emits a single, ultrashort chirped pulse whose duration is determined by the interaction bandwidth and the waveguide dispersion. Away from grazing, where slippage dominates, two distinct pulses are radiated at the Doppler upshifted and downshifted frequencies. Both the time and frequency domain expressions for the radiation characteristics are derived. (13 References). |
| title: | Experimental demonstration of dynamic focusing of a relativistic electron bunch by an overdense plasma lens |
| journal: | Physical Review Letters |
| vol-pages: | 2403-6 |
| year: | 1994 |
| authors: | G. Hairapetian,P. Davis,C. Clayton,C. Joshi,S. Hartman,C. Pellegrini,T. Katsouleas |
| abstract: | Dynamic focusing of a 3.8 MeV electron bunch, a few collisionless skin depths long approximately 3c/ omega /sub p/, by an overdense, thick plasma lens has been demonstrated. Because of electron inertial effects, the head of the bunch is virtually unaffected by the lens while the rest is focused to varying degree. Time-resolved measurements performed 31 cm downstream of the plasma lens show that, in time, the bunch pinches from an initial size of 2.7 mm (FWHM) to about 0.57 mm and then expands, in reasonable agreement with theory. (20 References). |
| title: | Ponderomotive focusing in axisymmetric RF linacs |
| journal: | Physical Review E |
| vol-pages: | 2031-7 |
| year: | 1993 |
| authors: | S. Hartman,J. Rosenzweig |
| abstract: | In many present and planned compact electron sources and linacs, very large rf accelerating fields are present in the linac structures. A charged particle whose trajectory is parallel to the axis receives no net focusing from the periodic transverse forces arising from the axisymmetric rf wave. However, if the lowest-order periodic transverse motion of the particles is included, a net ponderomotive focusing force is obtained when the momentum transfer is averaged over a period of the motion. Since this force is second order in the electric-field amplitude, the resultant focusing can be non-negligible in high gradient structures. In order to produce and preserve high-brightness beams in rf linacs it is necessary to obtain a better understanding of all the forces acting on the beam and the subsequent beam dynamics. To this end we examine the lowest-order ponderomotive rf focusing of electrons in axisymmetric standing- and traveling-wave linac structures. We obtain a generalized paraxial envelope equation which includes the effects of the ponderomotive focusing and longitudinal acceleration to describe the transverse beam envelope evolution. The implications of our results on beam dynamics in electron linacs are examined, and extensions of the results to positron and proton linacs are discussed. |
| title: | Measurements of High Gain and Intensity Fluctuations in a Self-Amplified, Spontaneous-Emission Free-Electron Laser |
| journal: | Physical Review Letters |
| vol-pages: | 289-92 |
| year: | 1998 |
| authors: | M. Hogan,C. Pellegrini,J. Rosenzweig,G. Travish,A. Varfolomeev,S. Anderson,K. Bishofberger,P. Frigola,A. Murokh,N. Osmanov,S. Reiche,A. Tremaine |
| abstract: | We report measurements of large gain for a single pass free-electron laser operating in self-amplified spontaneous emission (SASE) at 16 mm starting from noise. We also report the first observation and analysis of intensity fluctuations of the SASE radiation intensity in the high gain regime. The results are compared with theoretical predictions and simulations. |
| title: | Measurements of gain larger than 10(5) at 12 mu m in a self-amplified spontaneous-emission free-electron laser |
| journal: | Physical Review Letters |
| vol-pages: | 4867-70 |
| year: | 1998 |
| authors: | M. Hogan,C. Pellegrini,J. Rosenzweig,S. Anderson,P. Frigola,A. Tremaine,C. Fortgang,D. Nguyen,R. Sheffield,J. Kinross-Wright,A. Varfolomeev,A. Varfolomeev,S. Tolmachev,R. Carr |
| abstract: | We report measurements of very large output intensities corresponding to a gain larger than 10/sup 5/ for a single pass free-electron laser operating in the self-amplified spontaneous emission (SASE) mode at 12 mu m. We also report the observation and analysis of intensity fluctuations of the SASE radiation intensity in the high-gain regime. The results are compared with theoretical predictions and simulations. (18 References). |
| title: | Diffraction radiation defocussing of an electron ring |
| journal: | Nuclear Instruments & Methods |
| vol-pages: | 131-5 |
| year: | 1971 |
| authors: | E. Keil,C. Pellegrini,A. Sessler |
| abstract: | The influence upon axial stability in an electron ring of the diffraction radiation reaction force, generated by a ring moving in an acceleration column, is calculated theoretically. A stability criterion is obtained, and numerical examples show that the criterion is not an important constraint upon the choice of parameters or the operation of an electron ring accelerator. |
| title: | Beam-cavity interaction in electron storage rings |
| journal: | Nuclear Instruments & Methods |
| vol-pages: | 475-85 |
| year: | 1975 |
| authors: | E. Keil,C. Pellegrini,A. Turrin,M. Sessler |
| abstract: | A formal expression is obtained for the energy loss per turn, of a rigid bunch of electrons, to a closed cylindrical cavity with quality factor Q. The expression is valid provided the diameter of the entrance and exit ports for the beam are small compared to the bunch length. The effect of the ports is studied in an independent computational method. The energy loss is numerically evaluated for a range of parameters of interest to electron storage rings. (13 References). |
| title: | One-dimensional numerical simulation of a free electron laser-storage ring system |
| journal: | Journal of Applied Physics |
| vol-pages: | 670-7 |
| year: | 1984 |
| authors: | A. Luccio,C. Pellegrini |
| abstract: | A numerical simulation of a free electron laser oscillator-storage ring system is presented. The model describes the evolution of the system toward a steady state and gives information on the change of the laser power and of the electron and photon pulse shape during the transient. The steady-state laser power output and electron beam properties are compared with the existing theoretical model. (17 References). |
| title: | Exponential gain and saturation of a self-amplified spontaneous emission free-electron laser |
| journal: | Science |
| vol-pages: | 2037-41 |
| year: | 2001 |
| authors: | S. Milton,E. Gluskin,N. Arnold,C. Benson,W. Berg,S. Biedron,M. Borland,Y. Chae,R. Dejus,M. Den Hartog,B. Deriy,M. Erdmann,Y. Eidelman,M. Hahne,Z. Huang,K. Kim,J. Lewellen,Y. Li,A. Lumpkin,O. Makarov,E. Moog,A. Nassiri,V. Sajaev,R. Soliday,B. Tieman,E. Trakhtenberg,G. Travish,I. Vasserman,G. Wiemerslage,B. Yang,N. Vinokurov,X. Wang |
| abstract: | Self-amplified spontaneous emission in a free-electron laser has been proposed for the generation of very high brightness coherent X-rays. This process involves passing a high-energy, high-charge, short-pulse, low-energy-spread, and low-emittance electron beam through the periodic magnetic field of a long series of high-quality undulator magnets. The radiation produced grows exponentially in intensity until it reaches a saturation point. We report on the demonstration of self-amplified spontaneous emission gain, exponential growth, and saturation at visible (530 nanometers) and ultraviolet (385 nanometers) wavelengths. Good agreement between theory and simulation indicates that scaling to much shorter wavelengths may be possible. These results confirm the physics behind the self-amplified spontaneous emission process and forward the development of an operational X-ray free-electron laser. (30 References). |
| title: | Observation of self-amplified spontaneous emission and exponential growth at 530 nm |
| journal: | Physical Review Letters |
| vol-pages: | 988-91 |
| year: | 2000 |
| authors: | S. Milton,E. Gluskin,S. Biedron,R. Dejus,P. Den Hartog,J. Galayda,K. Kim,J. Lewellen,E. Moog,V. Sajaev,N. Sereno,G. Travish,N. Vinokurov,N. Arnold,C. Benson,W. Berg,J. Biggs,M. Borland,J. Carwardine,Y. Chae,G. Decker,B. Deriy,M. Erdmann,H. Friedsam,C. Gold,A. Grelick,M. Hahne,K. Harkay,Z. Huang,E. Lessner,R. Lill,A. Lumpkin,O. Makarov,G. Markovich,D. Meyer,A. Nassiri,J. Noonan,S. Pasky,G. Pile,T. Smith,R. Soliday,B. Tieman,E. Trakhtenberg,G. Trento,I. Vasserman,D. Walters,X. Wang,G. Wiemerslage,S. Xu,B. Yang |
| abstract: | Experimental evidence for self-amplified spontaneous emission (SASE) at 530 nm is reported. The measurements were made at the low-energy undulator test line facility at the Advanced Photon Source, Argonne National Laboratory. The experimental setup and details of the experimental results are presented, as well as preliminary analysis. This experiment extends to shorter wavelengths the operational knowledge of a linac-based SASE free-electron laser and explicitly shows the predicted exponential growth in intensity of the optical pulse as a function of length along the undulator. (20 References). |
| title: | Self-amplified spontaneous emission saturation at the Advanced Photon Source free-electron laser |
| journal: | Review of Scientific Instruments |
| vol-pages: | 1407 |
| year: | 2002 |
| authors: | E. Moog,S. Milton,N. Arnold,C. Benson,W. Berg,S. Biedron,M. Borland,Y. Chae,R. Dejus,P. Den Hartog,B. Deriy,M. Erdmann,E. Gluskin,Z. Huang,K. Kim,J. Lewellen,Y. Li,A. Lumpkin,O. Makarov,A. Nassiri,V. Sajaev,R. Soliday,B. Tieman,E. Trakhtenberg,G. Travish,I. Vasserman,N. Vinokurov,G. Wiemerslage,B. Yang |
| abstract: | Today, many bright photon beams in the ultraviolet and x-ray wavelength range are produced by insertion devices installed in specially designed third-generation storage rings. There is the possibility of producing photon beams that are orders of magnitude brighter than presently achieved at synchrotron sources, by using self-amplified spontaneous emission (SASE). At the Advanced Photon Source (APS), the low-energy undulator test line (LEUTL) free-electron laser (FEL) project was built to explore the SASE process in the visible through vacuum ultraviolet wavelength range. While the understanding gained in these experiments will guide future work to extend SASE FELs to shorter wavelengths, the APS FEL itself will become a continuously tunable, bright light source. Measurements of the SASE process to saturation have been made at 530 and 385 nm. A number of quantities were measured to confirm our understanding of the SASE process and to verify that saturation was reached. The intensity of the FEL light was measured versus distance along the FEL, and was found to flatten out at saturation. The statistical variation of the light intensity was found to be wide in the exponential gain region where the intensity is expected to be noisy, and narrower once saturation was reached. Absolute power measurements compare well with GINGER simulations. The FEL light spectrum at different distances along the undulator line was measured with a high-resolution spectrometer, and the many sharp spectral spikes at the beginning of the SASE process coalesce into a single peak at saturation. The energy spread in the electron beam widens markedly after saturation due to the number of electrons that transfer a significant amount of energy to the photon beam. Coherent transition radiation measurements of the electron beam as it strikes a foil provide additional confirmation of the microbunching of the electron beam. The quantities measured confirm that saturation was indeed reached. Details are given in Milton et al., Science 292, 2037 (2001) (also online at www.sciencexpress.org as 10.1126/science. 1059955, 17 May 2001), and Lewellen et al., "Present Status and Recent Results from the APS SASE FEL," to be published in the Proceedings of the 23rd International Free-Electron Laser Conference, Darmstadt, Germany, 20?24 August 2001. |
| title: | Properties of the ultrashort gain length, self-amplified spontaneous emission free-electron laser in the linear regime and saturation |
| journal: | Physical Review E |
| vol-pages: | 066501 |
| year: | 2003 |
| authors: | A. Murokh,R. Agustsson,M. Babzien,I. Ben-Zvi,L. Bertolini,K. Van Bibber,R. Carr,M. Cornacchia,P. Frigola,J. Hill,E. Johnson,L. Klaisner,G. Le Sage,M. Libkind,R. Malone,H. Nuhn,C. Pellegrini,S. Reiche,G. Rakowsky,J. Rosenzweig,R. Ruland,J. Skaritka,A. Toor,A. Tremaine,X. Wang,V. Yakimenko |
| abstract: | VISA (Visible to Infrared SASE Amplifier) is a high-gain self-amplified spontaneous emission (SASE) free-electron laser (FEL), which achieved saturation at 840 nm within a single-pass 4-m undulator. The experiment was performed at the Accelerator Test Facility at BNL, using a high brightness 70-MeV electron beam. A gain length shorter than 18 cm has been obtained, yielding a total gain of 2x10(8) at saturation. The FEL performance, including the spectral, angular, and statistical properties of SASE radiation, has been characterized for different electron beam conditions. Results are compared to the three-dimensional SASE FEL theory and start-to-end numerical simulations of the entire injector, transport, and FEL systems. An agreement between simulations and experimental results has been obtained at an unprecedented level of detail. |
| title: | First results from bent crystal extraction at the Fermilab Tevatron |
| journal: | Nuclear Instruments & Methods B |
| vol-pages: | 231-238 |
| year: | 1996 |
| authors: | C. Murphy,R. Carrigan,D. Chen,G. Jackson,N. Mokhov,H. Shih,B. Cox,V. Golovatyuk,A. McManus,A. Bogacz,D. Cline,S. Ramachandran,J. Rhoades,J. Rosenzweig,B. Newberger,J. Ellison,S. Baker,C. Sun,W. Gabella,E. Tsyganov,A. Taratin,A. Asseev,V. Biryukov,A. Khanzadeev,T. Prokofieva,V. Samsonov,G. Solodov |
| abstract: | First results from Fermilab Experiment 853 are presented. E853 is an experiment to test the feasibility and efficiency of extracting a low-intensity beam from the halo of the Tevatron using channeling in a bent silicon crystal. The motivation of the experiment is to apply crystal extraction to trans-TeV accelerators like the LHC. Extensive simulation work has been carried out. Two accelerator operating modes have been developed for crystal studies, ''kick'' mode and diffusion mode. Results from the first successful extraction in kick mode are presented. |
| title: | Generation of high-intensity coherent radiation in the soft-X-ray and vacuum-ultraviolet region |
| journal: | Journal of the Optical Society of America B-Optical Physics |
| vol-pages: | 259-64 |
| year: | 1985 |
| authors: | J. Murphy,C. Pellegrini |
| abstract: | An electron beam can be made to interact with an undulator magnet so that a collective unstable mode is excited. In this mode, the beam generates coherent radiation whose wavelength is determined by the undulator period and the electron energy. By proper choice of the electron-beam energy, energy dispersion, and density, one can obtain coherent radiation in the soft-X-ray region with peak and average power of the order of hundreds of megawatts and hundreds of milliwatts, respectively. Larger peak powers, of the order of a gigawatt, can be expected for UV radiation with lambda in the range of 500-2000 AA. The authors discuss the physical principles of these systems and give examples of how they might be built. (14 References). |
| title: | Collective Instability of a Free-Electron Laser Including Space-Charge and Harmonics |
| journal: | Optics Communications |
| vol-pages: | 197-202 |
| year: | 1985 |
| authors: | J. Murphy,C. Pellegrini,R. Bonifacio |
| abstract: | The effects of harmonics, space charge and electron energy spread on the collective instability regime of an electron beam coupled to a planar undulator are analyzed. Both analytical and numerical results are presented. |
| title: | On a new instability in electron-positron storage rings (the head- tail effect) |
| journal: | Nuovo Cimento A |
| vol-pages: | 447-73 |
| year: | 1969 |
| authors: | C. Pellegrini |
| abstract: | It is shown that a bunched electron or positron beam of a storage ring can become unstable because of an effect not previously considered; the instability is due to the regenerative effect introduced by synchrotron oscillations, which enhances the action on the beam of rapidly decaying electromagnetic signals excited by the beam itself on its surrounding media. The results obtained show that the effect can produce instabilities for small beam currents (in the milliampere range), and that it can be influenced and reduced by properly choosing some parameters of the storage ring. |
| title: | Quasi-isochronous storage ring |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 27-36 |
| year: | 1991 |
| authors: | C. Pellegrini,D. Robin |
| abstract: | The authors study the single particle and collective dynamics of a storage ring where the momentum compaction is made small to make it nearly isochronous, to reduce the bunch length and increase the peak current. They find that a quasi-isochronous ring makes it possible to obtain a bunch length in the millimeter range and to increase the beam longitudinal brilliance by more than one order of magnitude. (16 References). |
| title: | Isochronous storage-rings and high-luminosity electron-positron colliders |
| journal: | Annals of the NY Academy of Sciences |
| vol-pages: | 163-71 |
| year: | 1991 |
| authors: | C. Pellegrini,D. Robin |
| abstract: |
| title: | Crossing of an incoherent integral resonance in the electron ring accelerator |
| journal: | Nuclear Instruments & Methods |
| vol-pages: | 109-16 |
| year: | 1970 |
| authors: | C. Pellegrini,A. Sessler |
| abstract: | In one mode of operation of an electron ring accelerator (ERA), at the end of compression rings are slowly moved through the radial integral betatron resonance Q_r=1. Although the coherent radial oscillation frequency of the ring as a whole remains below unity, the oscillation frequencies of individual electron are (incoherently) caused to pass through the resonance because of the additional focusing from ions trapped in the ring. In this paper the effect of field errors on ring major and minor radii is evaluated-theoretically-for the cases in which the spread in the square of the electron oscillation frequency ( Delta(2)) is (a) much smaller and (b) much larger than the contribution to the square of the oscillation frequency from the ions ( Lambda(2)). |
| title: | Physics with and physics of colliding electron beams |
| journal: | Comments on Nuclear & Particle Physics |
| vol-pages: | 55-68 |
| year: | 1970 |
| authors: | C. Pellegrini,A. Sessler |
| abstract: | The first section of this article deals with the physics that can be done with colliding beams. Experiments which have been already performed and those planned for the future are reviewed. The second section discusses the physics of colliding electron ring devices. |
| title: | The equilibrium length of high-current bunches in electron storage rings |
| journal: | Nuovo Cimento A |
| vol-pages: | 116-34 |
| year: | 1971 |
| authors: | C. Pellegrini,A. Sessler |
| abstract: | The consequence of electrical interaction with various resonant structures is expressed in terms of quadratures over the impedance of the structures, and impedance functions for a variety of elements are evaluated. It is shown that elements having resonances at high frequency can, above transition, cause bunches to increase in length with increasing current. The parametric dependence of the bunch lengthening is found to be in good agreement with observations, and numerical estimates, which are in substantial agreement with experiment are presented. (16 References). |
| title: | X-ray free-electron lasers- principles, properties and applications |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 33-40 |
| year: | 2003 |
| authors: | C. Pellegrini,J. Stoehr |
| abstract: | With advances in technology, it is now possible to realize the dream of fully coherent X-ray laser. |
| title: | Comparison of the coherent radiation-induced microbunching instability in a free-electron laser and a magnetic chicane |
| journal: | Physical Review Special Topics-Accelerators & Beams |
| vol-pages: | 040702 |
| year: | 2003 |
| authors: | S. Reiche,J. Rosenzweig |
| abstract: | A self-amplified spontaneous emission free-electron laser (SASE FEL) is a device which is based on the creation of a very intense, relativistic electron beam which has very little temperature in all three phase planes. The beam in this system is described as having "high brightness,'' and when it is bent repetitively in a magnetic undulator, undergoes a radiation-mediated microbunching instability. This instability can amplify the original radiation amplitude at a particular, resonant wavelength by many orders of magnitude. In order to obtain high brightness beams, it is necessary to compress them to obtain higher currents than available from the electron source. Compression is accomplished by the use of magnetic chicanes, which are quite similar to, if much longer than, a single period of the undulator. It should not be surprising that such chicanes also support a radiation-mediated microbunching interaction, which has recently been investigated, and has been termed coherent synchrotron radiation (CSR) instability. The purpose of this paper is to compare and contrast the characteristics of the closely related FEL and CSR microbunching instabilities. We show that a high-gain regime of the CSR instability exists which is formally similar to the FEL instability. |
| title: | Experimental confirmation of transverse focusing and adiabatic damping in a standing wave linear accelerator |
| journal: | Physical Review E |
| vol-pages: | 3572-7 |
| year: | 1997 |
| authors: | S. Reiche,J. Rosenzweig,S. Anderson,P. Frigola,M. Hogan,A. Murokh,C. Pellegrini,L. Serafini,G. Travish,A. Tremaine |
| abstract: | The measurement of the transverse phase-space map, or transport matrix, of a relativistic electron in a high-gradient, radio-frequency linear accelerator (rf linac) at the UCLA photoinjector is reported. This matrix, which indicates the effects of acceleration (adiabatic damping), first-order transient focusing, and ponderomotive second-order focusing, is measured as a function of both rf field amplitude and phase in the linac. The elements of the matrix, determined by observation of centroid motion at a set of downstream diagnostics due to deflections induced by a set of upstream steering magnets, compare well with previously developed analytical theory [J. Rosenzweig and L. Serafini, Phys. Rev. E 49, 1599 (1994)]. The determinant of the matrix is obtained, yielding a direct confirmation of trace space adiabatic damping. Implications of these results on beam optics at moderate energy in high-gradient linear accelerators such as rf photoinjectors are discussed. |
| title: | Quasi-isochronous storage rings |
| journal: | Physical Review E |
| vol-pages: | 2149-56 |
| year: | 1993 |
| authors: | D. Robin,E. Forest,C. Pellegrini,A. Amiry |
| abstract: | A study is made of the single-particle dynamics of an electron-positron storage ring where the phase-slip factor is made small in order to make the ring nearly isochronous and reduce the bunch length. What is found is that a quasi-isochronous ring makes it possible to obtain a bunch length in the millimeter range, about one order of magnitude shorter than present values. In this study the authors have extended the work of others on isochronous storage rings by quantitatively including higher-order terms in the longitudinal equations of motion. Scaling laws are then derived relating the linear term with the next-highest-order term. These scaling laws, which are derived from a two-dimensional Hamiltonian (one dimension of position and one of momentum), establish criteria for stability. These scaling laws are then checked with full six-dimensional tracking on one particular lattice. (13 References). |
| title: | Nonlinear Plasma Dynamics in the Plasma Wakefield Accelerator |
| journal: | IEEE Transactions on Plasma Science |
| vol-pages: | 186-91 |
| year: | 1987 |
| authors: | J. Rosenzweig |
| abstract: |
| title: | A proposed dielectric-loaded resonant laser accelerator |
| journal: | Physical Review Letters |
| vol-pages: | 2467-70 |
| year: | 1995 |
| authors: | J. Rosenzweig,A. Murokh,C. Pellegrini |
| abstract: | A laser-pumped accelerator utilizing a resonant, periodic, dielectric structure is proposed. The electromagnetic fields due to a side-injected laser beam impinging on this structure are calculated in a two-dimensional standing-wave approximation, leading to an estimated accelerating field in excess of 1 GV/m for accessible experimental parameters. The longitudinal dynamics of injected electrons in the device are discussed, as are the first- and second-order transverse focusing effects inherent to this structure. Similarities and differences between this scheme and conventional and other advanced accelerators are examined. (15 References). |
| title: | Transverse particle motion in radio-frequency linear accelerators |
| journal: | Physical Review E |
| vol-pages: | 1599-1602 |
| year: | 1994 |
| authors: | J. Rosenzweig,L. Serafini |
| abstract: | The transverse motion of a relativistic charged particle in a radio-frequency linear accelerator (rf linac) is examined. The spatially averaged equations of motion are derived for a particle in a periodic accelerating cavity system, and solved exactly in the ultrarelativistic limit. These solutions, along with an impulse treatment of the transients at the entrance and exit of the linac cavities, allow derivation of a linear transport matrix through the cavity. This generalized matrix is improved over previously derived results in that it is applicable to both traveling- and standing-wave structures, allows for arbitrary injection phase and spatial-harmonic content of the rf fields, and is more accurate in approximating the exact charged-particle motion. |
| title: | Coherent transition radiation diagnosis of electron beam microbunching |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 255-9 |
| year: | 1995 |
| authors: | J. Rosenzweig,G. Travish,A. Tremaine |
| abstract: | The action of the free-electron laser instability (FEL) on an electron beam produces a longitudinal density modulation with a periodicity near the resonant radiation wavelength. This modulation, which can produce femtosecond or shorter microbunches inside of a macroscopic picosecond electron pulse, has been proposed for use as a prebunching injector for both higher harmonic FELs and short wavelength accelerators. Standard methods involving streak cameras or beam sweeping with dipole mode cavities will certainly fail to provide information about this longitudinal microstructure, however. In this paper we explore the use of coherent transition radiation generated from a foil at the exit of an FEL undulator to diagnose both the longitudinal and transverse electron microbunch structure. (12 References). |
| title: | Nonlinear plasma dynamics in the plasma wake-field accelerator |
| journal: | Physical Review Letters |
| vol-pages: | 555-8 |
| year: | 1987 |
| authors: | J. Rosenzweig |
| abstract: | Excitation of nonlinear plasma oscillations by an intense ultrarelativistic electron beam is considered. It is shown, by analytical solutions of the one-dimensional relativistic fluid equations, that under certain conditions on the relative electron-beam and plasma densities extremely large longitudinal electric fields can be generated in the beam's wake. This scheme is a nonlinear version of the plasma wake-field accelerator, and is predicted to have advantages over the linear regime. (9 References). |
| title: | Trapping, thermal effects, and wave breaking in the nonlinear plasma wake-field accelerator |
| journal: | Physical Review A |
| vol-pages: | 3634-42 |
| year: | 1988 |
| authors: | J. Rosenzweig |
| abstract: | In this paper the author discusses a variety of physical aspects of the nonlinear regime of the plasma wake-field accelerator: general nonlinear properties, thermal effects, particle trapping, and maximum acceleration. The unifying motivation for this investigation is to discover the limit on the size of the plasma waves, as the interesting characteristics of the nonlinear scheme depend strongly on amplitude. Implications for laboratory and cosmic-ray acceleration are discussed. (20 References). |
| title: | Multiple-fluid models for plasma wake-field phenomena |
| journal: | Physical Review A |
| vol-pages: | 5249-55 |
| year: | 1989 |
| authors: | J. Rosenzweig |
| abstract: | In this paper the author presents various treatments of plasma wake-field phenomena which employ multiple-fluid models. These models generalize the one-dimensional, nonlinear, relativistic single-fluid model which has been used extensively in previous plasma wake-field calculations. Using a two-fluid model, the author discusses the interaction of a low-energy continuous electron beam with wake-field-generated plasma waves. The phenomena of continuous-beam modulation and wave period shortening are discussed. The relationship between these effects and the two-stream instability is also examined. Also, using a three-fluid model, effects due to plasma electron temperature in nonlinear plasma wake-fields are examined and compared to previous work. Finally, the consequences of ion motion induced by large-amplitude electron plasma waves are calculated by including the fluid behavior of the ions. (20 References). |
| title: | Beam optics of a self-focusing plasma lens |
| journal: | Physical Review D |
| vol-pages: | 2039-45 |
| year: | 1989 |
| authors: | J. Rosenzweig,P. Chen |
| abstract: | In this paper the authors analyze the optics of a high-energy beam which is focused by its own wakefields in a plasma. They calculate the effects of lens aberrations on the focusing strength of the lens and on the dilution of the beam's phase space. From this they derive the minimum spot size achievable using a bi-Gaussian beam and, after inclusion of the beam-beam pinch effect, the luminosity enhancement that can be gained in principle. They estimate the luminosity enhancement in the case of SLAC Linear Collider beam design parameters, and discuss limitations and possible improvements in plasma-lens performance. (7 References). |
| title: | Experimental observation of plasma wake-field acceleration |
| journal: | Physical Review Letters |
| vol-pages: | 98-101 |
| year: | 1988 |
| authors: | J. Rosenzweig,D. Cline,B. Cole,H. Figueroa,W. Gai,R. Konecny,J. Norem,P. Schoessow,J. Simpson |
| abstract: | The authors report the first experimental test of the physics of plasma wake-field acceleration performed at the Argonne National Laboratory Advanced Accelerator Test Facility. Megavolt-per-meter plasma wake fields are excited by a intense 21-MeV, multipicosecond bunch of electrons in a plasma of density n/sub e/ approximately=10/sup 13/ cm/sup -3/, and probed by a low-intensity 15-MeV witness pulse with a variable delay time behind the intense bunch. Accelerating and deflecting wake-field measurements are presented, and the results compared to theoretical predictions. (8 References). |
| title: | Experimental studies of plasma wake-field acceleration and focusing |
| journal: | Physica Scripta |
| vol-pages: | 110-21 |
| year: | 1990 |
| authors: | J. Rosenzweig,B. Cole,C. Ho,W. Gai,R. Konecny,S. Mtingwa,J. Norem,M. Rosing,P. Schoessow,J. Simpson |
| abstract: | The Plasma Wake-field Accelerator (PWFA) continues to be the object of much investigation, due to the promise of the ultra-high accelerating gradients that can exist in relativistic plasma waves driven in the wake of charged particle beams. These large amplitude plasma wake-fields are of interest in the laboratory, both for the wealth of basic nonlinear plasma wave phenomena which can be studied, as well as for the applications of acceleration and focusing of electrons and positrons in linear colliders. Plasma wake-field waves are also of importance in nature, due to their possible role in direct cosmic ray acceleration. The purpose of the present work is to review the experimental advances made in PWFA research at Argonne National Laboratory, in which many interesting beam and plasma phenomena have been observed. Emphasis is given to discussion of the nonlinear aspects of the PWFA beam-plasma interaction. (29 References). |
| title: | Diamagnetic fields due to finite-dimension intense beams in high-gain free-electron lasers |
| journal: | Physical Review E |
| vol-pages: | R2737-40 |
| year: | 1998 |
| authors: | J. Rosenzweig,P. Musumeci |
| abstract: | High-gain, self-amplified spontaneous emission free-electron lasers (SASE FEL's), with proposed operation in wavelengths extending down to X-rays, require intense relativistic electron beams, which under certain conditions can generate large diamagnetic fields. The action of these fields has the potential to seriously degrade FEL performance. It is shown here by both analysis and simulation that the finite size of the electron beams diminishes this effect so that it is negligible for proposed SASE FEL's. . (12 References). |
| title: | Experimental measurement of nonlinear plasma wake fields |
| journal: | Physical Review A |
| vol-pages: | 1586-89 |
| year: | 1989 |
| authors: | J. Rosenzweig,P. Schoessow,B. Cole,W. Gai,R. Konecny,J. Norem,J. Simpson |
| abstract: | We report direct high-resolution observation of nonlinear steepened plasma waves excited in the wake of an intense, self-pinched electron beam. Oscillations in both accelerating and deflecting fields are measured, and analyzed in the context of linear and nonlinear plasma-wave theory. The degree of nonlinearity in the wake fields is shown to be consistent with analytical predictions of the beam self-pinching. The impact of these results on plasma acceleration and focusing schemes is discussed. |
| title: | Demonstration of Electron-Beam Self-Focusing in Plasma Wake Fields |
| journal: | Physics of Fluids B-Plasma Physics |
| vol-pages: | 1376-83 |
| year: | 1990 |
| authors: | J. Rosenzweig,P. Schoessow,B. Cole,C. Ho,W. Gai,R. Konecny,S. Mtingwa,J. Norem,M. Rosing,J. Simpson |
| abstract: |
| title: | Quantum effects in high-gain free-electron lasers |
| journal: | Physical Review E |
| vol-pages: | 056502 |
| year: | 2001 |
| authors: | C. Schroeder,C. Pellegrini,P. Chen |
| abstract: | A many-particle fully quantized theory for a free-electron laser which is valid in the high-gain regime is presented. We examine quantum corrections for the high-gain single-pass free-electron laser. It is shown that quantum effects become significant when the photon energy becomes comparable to the gain bandwidth. The initiation of the free-electron laser process from quantum fluctuations in the position and momentum of the electrons is considered, and the parameter regime for enhanced start-up is identified. Photon statistics of the free-electron laser radiation are discussed, and the photon number statistics for the self-amplified spontaneous emission are calculated. (21 References). |
| title: | Chirped-beam two-stage free-electron laser for high-power femtosecond x-ray pulse generation |
| journal: | Journal of the Optical Society of America B-Optical Physics |
| vol-pages: | 1782-89 |
| year: | 2002 |
| authors: | C. Schroeder,C. Pellegrini,S. Reiche,J. Arthur,P. Emma |
| abstract: | A method for generating femtosecond-duration x-ray pulses with a free-electron laser is presented. This method uses an energy-chirped electron beam propagating through an undulator to produce a frequency-chirped x-ray pulse by self-amplified spontaneous emission. A short temporal pulse is created by use of a monochromator to select a narrow radiation bandwidth. A second undulator is used to amplify the short-duration radiation. The radiation characteristics produced by a chirped-beam two-stage free-electron laser are calculated, and the performance of the chirped-beam two-stage option for the Linac Coherent Light Source is considered. |
| title: | Envelope analysis of intense relativistic quasilaminar beams in RF photoinjectors: a theory of emittance compensation |
| journal: | Physical Review E |
| vol-pages: | 7565-90 |
| year: | 1997 |
| authors: | L. Serafini,J. Rosenzweig |
| abstract: | In this paper we provide an analytical description for the transverse dynamics of relativistic, space-charge-dominated beams undergoing strong acceleration, such as those typically produced by RF photoinjectors. These beams are chiefly characterized by a fast transition, due to strong acceleration, from the nonrelativistic to the relativistic regime in which the initially strong collective plasma effects are greatly diminished. However, plasma oscillations in the transverse plane are still effective in significantly perturbing the evolution of the transverse phase space distribution, introducing distortions and longitudinal-transverse correlations that cause an increase in the rms transverse emittance of the beam as a whole. The beam envelope evolution is dominated by such effects and not by the thermal emittance, and so the beam flow can be considered quasilaminar. The model adopted is based on the rms envelope equation, for which we find an exact particular analytical solution taking into account the effects of linear space-charge forces, external focusing due to applied as well as ponderomotive RF forces, acceleration, and adiabatic damping, in the limit that the weak nonlaminarity due to the thermal emittance may be neglected. This solution represents a special mode for beam propagation that assures a secularly diminishing normalized rms emittance and it represents the fundamental operating condition of a space-charge-compensated RF photoinjector. The conditions for obtaining emittance compensation in a long, integrated photoinjector, in which the gun and linac sections are joined, as well as in the case of a short gun followed by a drift and a booster linace, are examined. |
| title: | Generation of sub-picosecond electron bunches from RF photoinjectors |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 305-14 |
| year: | 1997 |
| authors: | L. Serafini,R. Zhang,C. Pellegrini |
| abstract: | In this paper we discuss the possibility to generate sub-picosecond electron bunches directly from a photoinjector by illuminating a photo-cathode in an RF cavity with a phase-locked sub-picosecond laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through a photoinjector. We provide analysis of the beam dynamics, as well as the comparison with numerical simulations. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi-cell RF gun structure based on the PWT linac presently in operation at UCLA. (23 References). |
| title: | Report of the U.S. Department of Energy Fusion Energy Sciences Advisory Committee (FESAC) panel reviewing the theory and computing program |
| journal: | Journal of Fusion Energy |
| vol-pages: | 229-44 |
| year: | 2000 |
| authors: | J. Sheffield,T. Antonsen,L. Berry,M. Brown,J. Dahlburg,R. Davidson,M. Greenwald,C. Hegna,W. McCurdy,D. Newman,C. Pellegrini,C. Phillips,D. Post,M. Rosenbluth,T. Simonen,J. Van Dam |
| abstract: | This Panel was set up by the Fusion Energy Sciences Advisory Committee (FESAC) at its November 2000 meeting for the purpose of addressing questions from the Department of Energy concerning the theory and computing/simulation program of the Office of Fusion Energy Sciences. Although the Panel primarily addressed programmatic questions, it acknowledges that the theory and computing in fusion energy sciences has a stellar record of research successes. (A recent FESAC report entitled "Opportunities in the Fusion Energy Sciences Program" listed a number of theory and computing research highlights.) Last year the National Research Council performed an assessment of the quality of the fusion energy sciences program-including theory and computing-and concluded that the quality of its research is on a par with that of other leading areas of contemporary physical science. |
| title: | Plasma Electron Trapping and Acceleration in a Plasma Wake Field Using a Density Transition |
| journal: | Physical Review Letters |
| vol-pages: | 1011?1014 |
| year: | 2001 |
| authors: | J. Rosenzweig,E. Esarey |
| abstract: | A new scheme for plasma electron injection into an acceleration phase of a plasma wake field is presented. In this scheme, a single, short electron pulse travels through an underdense plasma with a sharp, localized, downward density transition. Near this transition, a number of background plasma electrons are trapped in the plasma wake field, due to the rapid wavelength increase of the induced wake wave in this region. The viability of this scheme is verified using two-dimensional particle-in-cell simulations. To investigate the trapping and acceleration mechanisms further, a 1D Hamiltonian analysis, as well as 1D simulations, has been performed, with the results presented and compared. |
| title: | Plasma source test and simulation results for the underdense plasma lens experiment at the UCLA Neptune Laboratory |
| journal: | IEEE Transactions on Plasma Science |
| vol-pages: | 271-7 |
| year: | 2000 |
| authors: | H. Suk,C. Clayton,C. Joshi,T. Katsouleas,P. Muggli,R. Narang,C. Pellegrini,J. Rosenzweig |
| abstract: | The planned plasma lens experiment at the UCLA Neptune Laboratory is described. In the experiment, electron beams with an energy of 16 MeV, a charge of 4 nC, and a pulse duration of 30 ps full-width at half-maximum (FWHM) are designed to be produced from the 1.625-cell photoinjector radio-frequency gun (f=2.856 GHz) and PWT linac in the Neptune. The generated beams are passed through a thin plasma with a density of low 10/sup 12/ cm/sup -3/ range and a thickness of a few centimeters. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. In this paper, the overview of the planned plasma lens experiment and the test results of the plasma source for various conditions are presented. In addition, computer simulations with a 2-1/2 dimensional particle-in-cell code (MAGIC) were performed and the simulation results are shown. (19 References). |
| title: | Electromagnetic wake fields and beam stability in slab-symmetric dielectric structures |
| journal: | Physical Review E |
| vol-pages: | 7204-16 |
| year: | 1997 |
| authors: | A. Tremaine,J. Rosenzweig,P. Schoessow |
| abstract: | Several promising schemes for high-gradient acceleration of charged particles in slab-symmetric electromagnetic structures have been recently proposed. In this paper we investigate, by both computer simulation and theoretical analysis, the longitudinal and transverse wake fields experienced by a relativistic charged particle beam in a planar structure. We show that in the limit of an infinitely wide beam the net deflecting wake fields vanishes. This result is verified in the limit of a large aspect ratio (sheet) beam by finite beam analysis based on a Fourier decomposition of the current profile, as well as a paraxial wave analysis of the wake fields driven by Gaussian profile beams. The Fourier analysis forms the basis of an examination of flute instability in the sheet beam system. Practical implications of this result for beam stability and enhanced current loading in short-wavelength advanced accelerators are discussed. |
| title: | Observation of Self-Amplified Spontaneous-Emission-Induced Electron-Beam Microbunching Using Coherent Transition Radiation |
| journal: | Physical Review Letters |
| vol-pages: | 5816?5819 |
| year: | 1998 |
| authors: | A. Tremaine,J. Rosenzweig,S. Anderson,P. Frigola,M. Hogan,A. Murokh,C. Pellegrini,D. Nguyen,R. Sheffield |
| abstract: | We report the measurement of electron-beam microbunching at the exit of a self-amplified spontaneous-emission free-electron laser (SASE FEL), by observation of coherent transition radiation (CTR). The CTR was found to have an angular spectrum much narrower than spontaneous transition radiation and a narrow-band frequency spectrum. The central frequency of the fundamental CTR spectrum is found to differ slightly from that of the SASE, a finding in disagreement with previously invoked CTR theory. The CTR measurement establishes the uniformity of microbunching in the transverse dimension, indicating the SASE FEL operates in a dominant transverse mode. |
| title: | Fundamental and harmonic microbunching in a high-gain self-amplified spontaneous-emission free-electron laser |
| journal: | Physical Review E |
| vol-pages: | 036503 |
| year: | 2002 |
| authors: | A. Tremaine,X. Wang,M. Babzien,I. Ben-Zvi,M. Cornacchia,A. Murokh,H. Nuhn,R. Malone,C. Pellegrini,S. Reiche,J. Rosenzweig,J. Skaritka,V. Yakimenko |
| abstract: | Electron beam microbunching in both the fundamental and second harmonic in a high-gain self-amplified spontaneous emission free-electron laser (SASE FEL) was experimentally characterized using coherent transition radiation. The microbunching factors for both modes (b1 and b2) approach unity, an indication of FEL saturation. These measurements are compared to the predictions of FEL simulations. The simultaneous capture of the microbunching and SASE radiation for individual micropulses correlate the longitudinal electron beam structure with the FEL gain. |
| title: | Experimental characterization of nonlinear harmonic radiation from a visible self-amplified spontaneous emission free-electron laser at saturation |
| journal: | Physical Review Letters |
| vol-pages: | 204801 |
| year: | 2002 |
| authors: | A. Tremaine,X. Wang,M. Babzien,I. Ben-Zvi,M. Cornacchia,H. Nuhn,R. Malone,A. Murokh,C. Pellegrini,S. Reiche,J. Rosenzweig,V. Yakimenko |
| abstract: | Nonlinear harmonic radiation was observed using the VISA self-amplified, spontaneous emission (SASE) free-electron laser (FEL) at saturation. The gain lengths, spectra, and energies of the three lowest SASE FEL modes were experimentally characterized. The measured nonlinear harmonic gain lengths and center spectral wavelengths decrease with harmonic number, n, which is consistent with nonlinear harmonic theory. Both the second and third nonlinear harmonics energies are about 1% of the fundamental energy. These experimental results demonstrate for the first time the feasibility of using nonlinear harmonic SASE FEL radiation to produce coherent, femtosecond X-rays. (33 References). |
| title: | Study of a novel compact standing wave RF linac |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 295-304 |
| year: | 1997 |
| authors: | R. Zhang,C. Pellegrini,R. Cooper |
| abstract: | A novel, compact RF linac structure, the plane wave transformer (PWT), is studied. The PWT provides high accelerating field and high efficiency, and can be used to accelerate high-brightness beams. PWT linac prototypes with eight cells at S-band have been developed at UCLA and successfully used to accelerate an electron beam by more than 10 MeV in 40 cm. In this paper, we describe the principal properties of this structure, the electric parameters obtained from numerical simulation, and measurement results from microwave cold tests. The mechanical design for prototype linacs is also reported. (13 References). |
| title: | Envelope Instability in Low-Energy Proton Synchrotrons |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 24-30 |
| year: | 1990 |
| authors: | P. Zhou,J. Rosenzweig |
| abstract: | In this paper we investigate the limits on beam intensity in low-energy proton synchrotrons due to the instability of the beam envelope. This instability has been previously examined in the context of space charge dominated ion beams, in particular for inertial confinement fusion applications. We generalize the formalism of beam envelope evolution to include effects found in circular accelerators, i.e. curvature focusing and momentum dispersion. Several example lattices are analyzed to determine intensity limits imposed by onset of envelope instability; it is found that the instability can occur without depressing the phase advance below 90-degrees per cell. |
| title: | Plasma density transition trapping as a possible high-brightness electron beam source |
| journal: | PHYSICAL REVIEW SPECIAL TOPICS - ACCELERATORS AND BEAMS |
| vol-pages: | 7:011301 |
| year: | 2004 |
| authors: | M.C Thompson,J.B Rosenzweig,H. Suk |
| abstract: | Plasma density transition trapping is a recently proposed self-injection scheme for plasma wakefield accelerators. This technique uses a sharp downward plasma density transition to trap and accelerate background plasma electrons in a plasma wakefield. This paper examines the quality of electron beams captured using this scheme in terms of emittance, energy spread, and brightness. Two-dimensional particle-in-cell simulations show that these parameters can be optimized by manipulating the plasma density profile.We also develop, and support with simulations, a set of scaling laws that predicts how the brightness of transition trapping beams scales with the plasma density of the system. These scaling laws indicate that transition trapping can produce beams with brightness > 5 x 10^14 A/(mrad)^2. A proof-ofprinciple transition trapping experiment is planned for the near future. The proposed experiment is described in detail. |
| title: | Proposed continuous wave energy recovery operation of an x-ray free electron laser |
| journal: | Physical Review Special Topics - Accelerators and Beams |
| vol-pages: | 8: 010701 |
| year: | 2005 |
| authors: | J. Sekutowicz,S. Bogacz,D. Douglas,P. Kneisel,G. Williams,M. Ferrario,I. Ben-Zvi,J. Rose,J. Smedley,T. Srinivasan-Rao,L. Serafini,W.-D Moller,B. Petersen,D. Proch,S. Simrock,P. Colestock,J. Rosenzweig |
| abstract: | Commissioning of two large coherent light facilities (XFELs) at SLAC and DESY should begin in 2008 and 2011, respectively. In this paper we look further into the future, hoping to answer, in a very preliminary way, two questions. First: What will the next generation of XFEL facilities look like? Believing that superconducting technology offers advantages such as high quality beams with highly populated bunches, the possibility of energy recovery and higher overall efficiency than warm technology, we focus this preliminary study on the superconducting option. From this belief the second question arises: What modifications in superconducting technology and in the machine design are needed, as compared to the present DESY XFEL, and what kind of research and development program should be proposed to arrive in the next few years at a technically feasible solution with even higher brilliance and increased overall conversion of ac power to photon beam power? In this paper we will very often refer to and profit from the DESY XFEL design, acknowledging its many technically innovative solutions. |
| title: | Creation of plasma density transitions short compared to the plasma skin-depth |
| journal: | REVIEW OF SCIENTIFIC INSTRUMENTS |
| vol-pages: | 76:013303 |
| year: | 2005 |
| authors: | M. Thompson,J. Rosenzweig,G. Travish |
| abstract: | A plasma based electron beam source apparatus is described which creates a plasma with two distinct density regions separated by a transition which is shorter than the plasma skin depth kp^−1 of either region. This sharp density modulation is achieved by using a perforated stainless steel screen to filter half of a diffusing plasma column. A simple physical model predicts that the length of the plasma density transition will vary with the distance from the screen. For a weakly magnetized plasma, the transition length will be twice the distance, on a line normal to the screen plane, from the screen edge to the location where the transition is measured. The plasma column is generated using an argon discharge plasma source. It has a peak density of approximately 3.53 X 10^13 cm^−3 and a full width half maximum width of 5 cm. The discharge source utilizes a 7.5 cm diameter LaB6 disk cathode heated to 1300 °C using a graphite heater. The plasma column is filtered with a 78 mm thick stainless steel sheet with 152 mm holes and 21% open area. Plasma density transitions with lengths between 0.74 and 0.95 kp^−1 were measured. |
| title: | Velocity bunching of high-brightness electron beams |
| journal: | Physical Review Special Topics - Accelerators and Beams |
| vol-pages: | 8:014401 |
| year: | 2005 |
| authors: | S. Anderson,P. Musumeci,J. Rosenzweig,W. Brown,R. England,M. Ferrario,J. Jacob,M. Thompson,G. Travish,A. Tremaine,R. Yoder |
| abstract: | Velocity bunching has been recently proposed as a tool for compressing electron beam pulses in modernhigh brightness photoinjector sources. This tool is familiar from earlier schemes implemented for bunching dc electron sources, but presents peculiar challenges when applied to high current, low emittance beams from photoinjectors. The main difficulty foreseen is control of emittance oscillations in the beam in this scheme, which can be naturally considered as an extension of the emittance compensation process at moderate energies. This paper presents two scenarios in which velocity bunching, combined with emittance control, is to play a role in nascent projects. The first is termed ballistic bunching, where the changing of relative particle velocities and positions occur in distinct regions, a short high gradient linac, and a drift length. This scenario is discussed in the context of the proposed ORION photoinjector. Simulations are used to explore the relationship between the degree of bunching, and the emittance compensation process. Experimental measurements performed at the UCLA Neptune Laboratory of the surprisingly robust bunching process, as well as accompanying deleterious transverse effects, are presented. An unanticipated mechanism for emittance growth in bends for highly momentum chirped beam was identified and studied in these experiments. The second scenario may be designated as phase space rotation, and corresponds closely to the recent proposal of Ferrario and Serafini. Its implementation for the compression of the electron beam pulse length in the PLEIADES inverse Compton scattering (ICS) experiment at LLNL is discussed. It is shown in simulations that optimum compression may be obtained by manipulation of the phases in low gradient traveling wave accelerator sections. Measurements of the bunching and emittance control achieved in such an implementation at PLEIADES, as well as aspects of the use of velocity-bunched beam directly in ICS experiments, are presented. |
| title: | Development of X-ray Free-electron Lasers |
| journal: | IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS, |
| vol-pages: | VOL. 10, NO. 6, p. 1393-1404 |
| year: | 2004 |
| authors: | C. Pellegrini,S. Reiche |
| abstract: | We review and discuss the theoretical and experimental work that has led to the development of short wavelength free-electron lasers operating as single pass amplifiers, starting from the spontaneous undulator radiation, in the self amplified spontaneous emission mode. This work has led to several projects to build this type of free-electron lasers operating at a wavelength of about 0.1 nm, producing coherent X-ray pulses with an unprecedented brilliance and peak power, and pulse length in the femtosecond range. One such project, the LCLS, is presently under construction and is expected to be operational in 2008. |
| title: | Observation of Anomalously Large Spectral Bandwidth in a High-Gain Self-Amplified Spontaneous Emission Free Elctron Laser |
| journal: | Physical Review Letters |
| vol-pages: | 95:054801 |
| year: | 2005 |
| authors: | G. Andonian,A. Murokh,J. Rosenzweig,R. Agustsson,M. Babzien,I. Ben-Zvi,P. Frigola,J.Y Huang,L. Palumbo,C. Pellegrini,S. Reiche,G. Travish,C. Vicario,V. Yakimenko |
| abstract: | Observation of ultrawide bandwidth, up to 15% full-width, high-gain operation of a self-amplified spontaneous emission free-election laser (SASE FEL) is reported. This type of lasing is obtained with a strongly chirped beam (E=E 1:7%) emitted from the accelerator. Because of nonlinear pulse compression during transport, a short, high current bunch with strong mismatch errors is injected into the undulator, giving high FEL gain. Start-to-end simulations reproduce key features of the measurements and provide insight into mechanisms, such as angular spread in emitted photon and electron trajectory distributions, which yield novel features in the radiation spectrum. |
| title: | Adjustable, short focal length permanent-magnet quadrupole based electron beam final focus system |
| journal: | Physical Review Special Topics - Accelerators and Beams |
| vol-pages: | 8:072401 |
| year: | 2005 |
| authors: | J. Lim,P. Frigola,G. Travish,J. Rosenzweig,S. Anderson,W. Brown,J. Jacob,C. Robbins,A. Tremaine |
| abstract: | Advanced high-brightness beam applicaitons such as inverse-Compton scattering (ICS) depend on achieving of ultra-small spot sizes in high current beams. Modern injectors and compressors enable the production of high-brightness beams having needed short bunch lengths and small emittances. Along with these beam properties comes the need to produce tighter foci, using stronger, shorter focal length optics. An approach to creating such strong focusing-systems using high field, small-bore permanent-magnet quadrupoles (PMQs) is reported here. A final focus system employing three PMQs, each composed of 16 neodymium iron boride sectors in a Halbach geometry has been installed in the PLEIADES ICS experiment. The field gradient in these PMQs is 560 T/m, the highest ever reported in a magnetic optics system. As the magnets are of a fixed field-strength, the focusing system is tuned by adjusting the position of the three magnets along the beamline axis, in analogy to familiar camera optics. This paper discusses the details of the focusing system, simulation, design, fabrication and experimental procedure in creating ultra-small beams at PLEIADES. |
| title: | Higher harmonic inverse free-electron laser interaction |
| journal: | Physical Review E |
| vol-pages: | |
| year: | 2005 |
| authors: | P. Musumeci,C. Pellegrini,J. Rosenzweig |
| abstract: | We expand the theory of the inverse free electron laser IFEL interaction to include the possibility of energy exchange that takes place when relativistic particles traversing an undulator interact with an electromagnetic wave of a frequency that is a harmonic of the fundamental wiggler resonant frequency. We derive the coupling coefficients as a function of the IFEL parameters for all harmonics, both odd and even. The theory is supported by simulation results obtained with a three-dimensional Lorentz equation solver code. Comparisons are made between the results of theory and simulations, and the recent UCLA IFEL experimental results where higher harmonic IFEL interaction was observed. |
| title: | Effects of Ion Motion in Intense Beam-Driven Plasma Wakefield Accelerators |
| journal: | Physical Review Letters |
| vol-pages: | 95:195002 |
| year: | 2005 |
| authors: | J. Rosenzweig,A. Cook,A. Scott,M. Thompson,R. Yoder |
| abstract: | Recent proposals for using plasma wakefield accelerators (PWFA) as a component of a linear have included intense electron beams with densities many times in excess of the plasma beam’s electric fields expel the plasma electrons from the beam path to many beam radii in We analyze here the motion of plasma ions under the beam fields, and find for a proposed PWFA scenario that the ions completely collapse inside of the beam. Simulations of ion collapse are Implications of ion motion on the feasibility of the PWFA-based colliders are discussed. |
| title: | Pulsed-laser nonlinear Thomson scattering for general scattering geometries |
| journal: | Physical Review E |
| vol-pages: | 72:056502 |
| year: | 2005 |
| authors: | G. Krafft,A. Doyuran,J. Rosenzweig |
| abstract: | In a recent paper it has been shown that single electron Thomson backscatter calculations can be performed including the effects of pulsed high intensity lasers. In this paper we present a more detailed treatment of the problem and present results for more general scattering geometries. In particular, we present new results for 90° Thomson scattering. Such geometries have been increasingly studied as x-ray sources of short-pulse radiation. Also, we present a clearer physical basis for these different cases. |
| title: | High Energy Gain of Trapped Electrons in a Tapered, Diffraction-Dominated Inverse-Free-Electron Laser |
| journal: | Physical Review Letters |
| vol-pages: | 94:154801 |
| year: | |
| authors: | P. Musumeci,S.Ya Tochitsky,S. Boucher,C. Clayton,A. Doyuran,R. England,C. Joshi,C. Pellegrini,J. Ralph,J. Rosenzweig,C. Sung,S. Tolmachev,G. Travish,A. Varfolomeev,A. Jr.,T. Yarovoi,R. Yoder |
| abstract: | Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an inverse-freeelectron- laser (IFEL) accelerator experiment. A 14.5 MeVelectron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and field amplitude. The Rayleigh range of the laser, 1:8 cm, is much shorter than the undulator length yielding a diffraction-dominated interaction. Experimental results on the dependence of the acceleration on injection energy, laser focus position, and laser power are discussed. Simulations, in good agreement with the experimental data, show that most of the energy gain occurs in the first half of the undulator at a gradient of 70 MeV=m and that the structure in the measured energy spectrum arises because of higher harmonic IFEL interaction in the second half of the undulator. |
| title: | Side-coupled slab-symmetric structure for high-gradient acceleration using terahertz power |
| journal: | Physical Review Special Topics - Accelerators and Beams |
| vol-pages: | 8:111301 |
| year: | 2005 |
| authors: | R. Yoder,J. Rosenzweig |
| abstract: | A slab-symmetric dielectric-loaded accelerator structure, consisting of a vacuum gap between dielectric-lined conducting walls, is described. The device is resonantly excited by an external drive laser which is side coupled into the acceleration region; a novel coupling scheme, which consists of an array of narrow, equally spaced slots in the upper structure boundary, is presented and analyzed in detail. This structure partakes of the advantages of earlier slab-symmetric optical acceleration proposals, but will use a terahertz-frequency external radiation source ( 340 m), allowing realistic electron beams to be used in a proof-of-principle experiment. Two- and three-dimensional electromagnetic simulations are used to verify the mode patterns and study the effects of the couplers, including time-dependent calculations of the filling of the structure and particle-in-cell computations of the beam wakefields. Details of the resonance are found to be highly sensitive to the coupling slot geometry: the presence of the couplers can lead to frequency detuning, changes in the field breakdown limits and overall Q factor, and distortions of the field pattern. Beam wakefields are enhanced by the presence of the slots, but found to have no significant effect on the beam transport. The resonant accelerating fields, which are nearly constant along the short transverse direction, are found to have between 10 and 15 times the amplitude of the driving radiation, with only a small ( < 10%) admixture of other nonaccelerating modes. Field gradients are computed to be near 100 MV=m when the structure is driven with 100MWof terahertz laser power. Possible manufacturing methods for a prototype device are discussed. |
| title: | Emittance compensation with dynamically optimized photoelectron beam profiles |
| journal: | Nuclear Instruments and Methods in Physics Research A |
| vol-pages: | 57:87 |
| year: | 2005 |
| authors: | J. Rosenzweig,A. Cook,M. Dunning,M. Ferrario |
| abstract: | Much of the theory and experimentation concerning creation of a high-brightness electron beam from a photocathode, and then applying emittance compensation techniques, assumes that one must strive for a uniform density electron beam, having a cylindrical shape. On the other hand, this shape has large nonlinearities in the space-charge field profiles near the beam’s longitudinal extrema. These nonlinearities are known to produce both transverse and longitudinal emittance growth. On the other hand, it has recently been shown by Luiten that by illuminating the cathode with an ultra-short laser pulse of appropriate transverse profile, a uniform density, ellipsoidally shaped bunch is dynamically formed, which then has linear space-charge fields in all dimensions inside of the bunch. We study here this process, and its marriage to the standard emittance compensation scenario that is implemented in most recent photoinjectors. It is seen that the two processes are compatible, with simulations indicating a very high brightness beam can be obtained. The robustness of this scheme to systematic errors is examined. Prospects for experimental tests of this scheme are discussed. |
| title: | Beam amplitude behavior upon crossing a linear coupling resonance with damping in one dimension |
| journal: | IEEE Transactions on Nuclear Science |
| vol-pages: | 176-9 |
| year: | 1969 |
| authors: | M. Lee,E. Courant,C. Pellegrini,A. Sessler |
| abstract: | A study has been conducted to investigate theoretically the effects of vertical damping on the betatron oscillations for particles passing through a resonance. This report describes a calculation for a single-particle model and for the case of the upsilon /sub 1/+ upsilon /sub 2/=1 resonance. |
| title: | Strong sextupole focusing in planar undulators |
| journal: | Nuclear Instruments & Methods A |
| vol-pages: | 585-93 |
| year: | 1994 |
| authors: | G. Travish,J. Rosenzweig |
| abstract: | The range of parameters used in both working and proposed free electron lasers (FELs) has greatly expanded in recent years. Future machines are envisioned as fourth generation light sources providing researchers with high brightness, short wavelength, coherent radiation [see Ref. [1]: Report on the Workshop on Fourth Generation Light Source SLAC, Stanford CA, USA (February, 1992)] . Short wavelength operation, along with the long undulator required to produce high brightness photon beams in these devices, places tight requirements on the electron beam quality. In particular, the need to maintain a well focused beam is critical to successful operation of such an FEL. This paper examines the use of alternating gradient (AG) sextupole focusing in planar undulators . The equations of motion for an electron in an undulator field with a strong sextupole component are examined . Analytic as well as smooth approximation solutions are provided for AG sextupole focusing . It is shown that the mean electron longitudinal velocity can be kept constant through each focusing and defocusing section, but that the velocity differs between these sections . The effects of this stepwise velocity modulation as well as the beam size variation are explored computationally and compared to theory. Examples using the proposed SLAC 4 nm FEL, the UCLA 10.6 wm FEL as well as a Paladin based device are also given. |