First Name: L
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Last Name: Serafini
Full Name: L. Serafini
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33 papers
| title: | Proposed continuous wave energy recovery operation of an x-ray free electron laser |
| format: | journal article |
| year: | 2005 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| 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. |
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| title: | Start to End Simulations for the SPARX Proposal |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 18 authors: | | | | | | | | | | | | | | | | | | |
| abstract: | The resource allocation in the Italian National Research Plan (PNR) for the development of a coherent ultra-brilliant X-ray source, based on a SASE Free Electron Laser, brought about the formation of a CNR-ENEA-INFN- University of Roma "Tor Vergata" study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated leading to the SPARX proposal. We report in this paper the results of start to end simulations concerning the option based on an S-band normal conducting linac. Saturation at 1-10 nm can be achieved in a 40 m long undulator provided the peak current delivered by the linac is 2.5 kA at 2.5 GeV with rms normalized slice emittance of the order of 1 _m and the energy spread less than 0.1%. One of the most critical systems is the bunch compressor. The effects on beam dynamics of a magnetic chicane system and a rectilinear RF compressor (based on velocity bunching), integrated in a high brightness photoinjector, are analyzed and compared in this paper. |
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| title: | The SPARC Project: A High Brightness Electron Beam Source at LNF to Drive a SASE-FEL Experiment |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 75 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The Project SPARC (Sorgente Pulsata e Amplificata di Radiazione Coerente), proposed by a collaboration among ENEA-INFN-CNR-Universita' di Roma "Tor Vergata" -INFM-ST, was recently approved by the Italian Government and will be built at LNF of INFN. The aim of the project is to promote an R&D activity oriented to the development of a coherent ultra-brilliant X-ray source in Italy. This collaboration has identified a program founded on two main issues: the generation of ultra-high peak brightness electron beams and of resonant higher harmonics in the SASE-FEL process. |
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| title: | Photoinjector design for the LCLS |
| format: | conference procceeding |
| conference: | 23rd International Free Electron Laser Conference |
| year: | 2002 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | The design of the Linac Coherent Light Source assumes that a low-emittance, 1 nC, 10 ps beam will be available for injection into the 15 GeV linac. The proposed RF photocathode injector that will meet this requirement is based on a 1.6-cell S-band RF gun equipped with an emittance-compensating solenoid. The booster accelerator with a gradient of 25 MV/m is positioned at the beam waist coinciding with the first emittance maximum, i.e., the "new working point." The UV pulses required for cathode excitation will be generated by tripling the output of a Ti:sapphire laser system. Details of the design and the supporting simulations are presented. (12 References). |
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| title: | New design study and related experimental program for the LCLS RF photoinjector |
| format: | conference procceeding |
| conference: | 2000 European Particle Accelerator Conference |
| year: | 2000 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that lead to the discovery of a new effective working point for a split RF photoinjector. We consider the emittance compensation regime of a space charge beam: by increasing the solenoid strength, the emittance evolution shows a double minimum behavior in the drifting region. If the booster is located where the relative emittance maximum and the envelope waist occur, the second emittance minimum can be shifted to the booster exit and frozen at a very low level (0.3 mm-mrad for a 1 nC flat top bunch), to the extent that the invariant envelope matching conditions are satisfied. Standing Wave Structures or alternatively Traveling Wave Structures embedded in a Long Solenoid are both candidates as booster linac. A careful measurement of the emittance evolution as a function of position in the drifting region is necessary to verify the computation and to determine experimentally the proper position of the booster cavities. The new design study and supporting experimental program under way at the SLAC Gun Test Facility are discussed. |
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| title: | First Observation of Self-Amplified Spontaneous Emission in a Free-Electron Laser at 109 nm Wavelength |
| format: | journal article |
| year: | 2000 |
| 145 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We present the first observation of self-amplified spontaneous emission (SASE) in a free-electron laser (FEL) in the vacuum ultraviolet regime at 109 nm wavelength (11 eV). The observed free-electron laser gain (approximately 3000) and the radiation characteristics, such as dependency on bunch charge, angular distribution, spectral width, and intensity fluctuations, are all consistent with the present models for SASE FELs. |
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| title: | HOMDYN study for the LCLS RF photo-injector |
| format: | conference procceeding |
| conference: | 2nd ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams |
| year: | 2000 |
| 5 authors: | | | | | |
| abstract: | We report the results of a recent beam dynamics study, motivated by the need to redesign the LCLS photoinjector, that led to the discovery of a new effective working point for a split RF photoinjector. The HOMDYN code, the main simulation tool adopted in this work, is described together with its recent improvements. The new working point and its LCLS application is discussed. Validation tests of the HOMDYN model and low emittance predictions, 0.3 mm-mrad for a 1 nC flat top bunch, are performed with respect to the multi-particle tracking codes ITACA and PARMELA. (26 References). |
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| title: | A Comparison Between the Performance of Split and Integrated RF Photoinjectors |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 4 authors: | | | | |
| abstract: | RF photoinjectors, the present source of choice for production of ultra-high brightness electron beams, have two basic design types: split, in which a short, high gradient rf gun is followed by a a drift and a booster linac, and a lower gradient integrated photoinjector, in which the linac acceleration is connected directly to the gun. The first type is represented at UCLA by the Neptune photoinjector, the second by the newly constructed S-band PWT photoinjector. We examine, through simulation and theory, the relative merits of each type of injector, both from the point of view of the beam physics (ability of the source to produce high currents and low emittances), and of relative technical advantages. |
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| title: | The design for the LCLS RF photoinjector |
| format: | conference procceeding |
| conference: | 20th International Free Electron Laser Conference |
| year: | 1999 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | We report on the design of the RF photoinjector of the Linac Coherent Light Source. The RF photoinjector is required to produce a single 150 MeV bunch of similar to 1 nC and similar to 100 A peak current at a repetition rate of 120 Hz with a normalized rms transverse emittance of similar to 1 pi mm-mrad. The design employs a 1.6-cell S-band RF gun with an optical spot size at the cathode of a radius of similar to 1 mm and a pulse duration with an rms sigma of similar to 3 ps. The peak RF field at the cathode is 150 MV/m with extraction 57 degrees ahead of the RF peak. A solenoidal field near the cathode allows the compensation of the initial emittance growth by the end of the injection linac. Spatial and temporal shaping of the laser pulse striking the cathode will reduce the compensated emittance even further. Also, to minimize the contribution of the thermal emittance from the cathode surface, while at the same time optimizing the quantum efficiency, the laser wavelength for a Cu cathode should be tunable around 260 nm. Following the injection linac the geometric emittance simply damps linearly with energy growth. PARMELA simulations show that this design will produce the desired normalized emittance, which is about a factor of two lower than has been achieved to date in other systems. In addition to low emittance, we also aim for laser amplitude stability of 1% in the UV and a timing jitter in the electron beam of 0.5 ps rms, which will lead to less than 10% beam intensity fluctuation after the electron bunch is compressed in the main linac. |
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| title: | A High Voltage Extractor with Photocathodes |
| format: | conference procceeding |
| conference: | 1998 European Particle Accelerator Conference |
| year: | 1999 |
| 7 authors: | | | | | | | |
| abstract: | We describe a system designed for photocathode testing and beam dynamics studies which is based on a high voltage extractor and a sub–ps drive laser. The system’s distinctive characteristics are the ability to run in the short bunch regime — where the dynamics are not governed by the Child–Langmuir law — and the anticipated availability of both transverse and longitudinal beam diagnostics to determine the full beam distribution. The system consists of a pseudo parallel plate 100 kV DC gun with a removable cathode and a cathode–anode gap of 8 mm, yielding a cathode field of up to 10 MV/m. The drive laser is a Nd:Glass system capable of producing over 200 μJ at 264 nm with a pulse length adjustable from approximately 250 fs to over 1 ps. The goals of the system, described in this paper, are to support ongoing photocathode studies, including measuring high current density extraction from prepared cathodes and investigating the effect of surface variation of the quantum efficiency. Additional studies foreseen include parameterizing the effect of surface variations on the transverse emittance, and exploring beam dynamics such as the short bunch blow out regime which has recently been proposed as a way to produce uniform ellipsoidal charge density distributions[1]. |
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| title: | Laminar flow in non-relativistic intense proton beams |
| format: | conference procceeding |
| conference: | 1998 European Particle Accelerator Conference |
| year: | 1998 |
| 2 authors: | | |
| abstract: | An approach to the envelope description of laminar non-relativistic particle beams is presented, which describes a new kind of equilibrium flow for strongly space charge dominated proton beams subject to acceleration in RF Linacs. The analysis is based on the extension of the invariant envelope concept, recently introduced in the field of RF photo-injectors[1], to nonrelativistic particle beams whose envelope is dominated by coherent plasma oscillations instead of incoherent betatron motion associated to thermal rms emittance. An exact analytical solution of the rms envelope equation is presented, describing both the laminar regime and the transition to the thermal regime: the impact of this new beam equilibrium on the design of high intensity Linacs is discussed. |
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| title: | Beam dynamics in an integrated plane wave transformer photoinjector at S and X-band |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 6 authors: | | | | | | |
| abstract: | The beam dynamics of an integrated S-band RF photoinjector based on the plane wave transformer (PWT) concept, proposed as part of an SBIR collaboration between UCLA and DULY Research, are studied. The design, which calls for an 11.5 cell structure run at a peak accelerating field of 60 MV/m and uses a compact solenoid around the initial 2.5 cells, is based on a recently developed theory of emittance compensation. It calls for matching the beam onto a generalized equilibrium envelope, which produces a beam which diminishes in transverse size monotonically with acceleration. This condition minimizes the emittance, which is 1 mm-rad at Q=1 nC. This design is also scaled to produce nearly identical performance at X-band, giving an injector appropriate to running an FEL at the SLAC NLCTA. These designs are insensitive to RF emittance increase, allowing a wide choice of injection phase, and the option to compress the emitted pulse. (8 References). |
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| title: | Space charge dominated envelope dynamics of asymmetric beams in RF photoinjectors |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 3 authors: | | | |
| abstract: | While it has been proposed for several years that strongly asymmetric (sigma_x >> sigma_y) beams can be employed in RF photoinjectors to obtain asymmetric emittances for linear collider applications, it is known that the emittances obtained directly from RF photocathode guns are not suitably small for this purpose. Because of this, simulation work has been performed in an attempt to apply the principle of emittance compensation to recover the small and asymmetric emittances after suitable focusing and acceleration of photoinjector beams. In order to guide this difficult three-dimensional analysis, we present an extension of a previous theoretical model of the emittance compensation process in axisymmetric photoinjectors. In the extended model, we first analyze the general quadrupolar oscillations in a symmetric accelerating system, and then proceed to examine a propagation mode under asymmetric focusing. This mode is a generalization of the previously analyzed axisymmetric invariant envelope, allowing an optimization of the compensation process. Design philosophies, including rf cavity considerations, are included in the discussion. |
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| title: | Optimum operation of split RF photoinjectors |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 2 authors: | | |
| abstract: | We describe how to achieve minimum transverse emittance in RF photoinjectors by applying theoretical predictions from a fully analytical model of beam dynamics in a split injector. This device consists of a short two cell (full+partial) RF gun followed by a drift and a booster RF linac. Matching the beam in the booster to the invariant envelope, an equilibrium mode of laminar beam flow, is shown to be the basis of emittance correction. Analytical predictions are compared to numerical simulations, finding excellent agreement. We also show how a further improvement of the beam quality can be obtained by matching the beam out of the booster into a Brillouin flow with proper control of the envelope oscillations. If these are actually coherent plasma oscillations in the laminar regime, then the normalized RMS transverse emittance can be even further reduced. (7 References). |
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| title: | Experimental measurement of high-gradient standing wave accelerator transport matrix |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 3 authors: | | | |
| abstract: | This paper presents an experimental study of the transverse beam dynamics of an electron beam in a high-gradient, standing wave linear accelerator. A 3.6 MeV beam from the UCLA RF Photoinjector (SATURNUS) is injected at various phases and rf field amplitudes into the plane wave transformer (PWT) linac (peak acceleration 40 MeV/m), and its transverse dynamics measured by a corrector magnet sweeping method. This method allows us to reconstruct the transverse matrix elements, which are compared to analytical predictions (J.B. Rosenzweig and L. Serafini, Physical Review E 49, 1599 (1994)). The determinant of the experimentally derived matrix is found to be the ratio of the initial to final momentum, verifying the theory, and providing direct evidence of adiabatic damping of transverse trace space. (9 References). |
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| title: | Envelope analysis of intense relativistic quasilaminar beams in RF photoinjectors: a theory of emittance compensation |
| format: | unknown |
| year: | 1997 |
| 2 authors: | | |
| 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. |
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| title: | Generation of sub-picosecond electron bunches from RF photoinjectors |
| format: | unknown |
| year: | 1997 |
| 3 authors: | | | |
| 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). |
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| title: | Experimental confirmation of transverse focusing and adiabatic damping in a standing wave linear accelerator |
| format: | journal article |
| year: | 1997 |
| 10 authors: | | | | | | | | | | |
| 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. |
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| title: | Space-charge oscillations in a self-modulated electron beam in multi-undulator free-electron lasers |
| format: | conference procceeding |
| conference: | 18th International Free-Electron Laser Conference |
| year: | 1997 |
| 5 authors: | | | | | |
| abstract: | We examine here the oscillation of electron-beam density perturbations (longitudinal plasma oscillations) produced at the exit of a high-gain free-electron laser (FEL) by the action of the FEL instability. These oscillations, which are analyzed in the case of both a free-space drift and a dispersive section, can degrade the bunching of the beam in the drift between undulator sections in multi-stage FELs. The impact of these oscillations on the gain of an FEL in an undulator following such a drift, as well as the case of an optical klystron is studied. (9 References). |
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| title: | Envelope description of quasi-laminar beams undergoing reversible emittance transformations |
| format: | conference procceeding |
| conference: | 1996 European Particle Accelerator Conference |
| year: | 1997 |
| 2 authors: | | |
| abstract: | A fully analytical description is presented for the envelope behavior of intense, space charge dominated beams which are relativistic and quasi-laminar. It is based on a particular solution of the envelope equation for an accelerated beam, which is invariant under reversible emittance transformations: this solution has been termed invariant envelope. The treatment presented in this paper is applicable both to bunched beams in transport lines and in linacs, whenever the beam is space charge dominated. The main interest is in maximizing the beam brightness achievable by Photo-Injectors and preserving the beam quality during the first stages of acceleration. Simple analytical formulae are provided to predict the performances of these devices, when they are operated in the space charge emittance correction regime. (7 References). |
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| title: | A plasma klystron for generating ultra-short electron bunches |
| format: | conference procceeding |
| conference: | Workshop on Second Generation Plasma Accelerators |
| year: | 1996 |
| 7 authors: | | | | | | | |
| abstract: | A technique for producing ultra-short electron bunches (e,g., less than or equal to 100 fs) from a continuous electron beam using a short plasma wave section and a drift space is explored. The bunches are a fraction of a plasma wavelength long and are spaced by a plasma wavelength, making them of interest for injection into plasma accelerators or for driving a klystron-like structure to produce infrared radiation. |
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| title: | Electron micro-bunch generation from RF photoinjectors |
| format: | conference procceeding |
| conference: | Micro Bunches Workshop |
| year: | 1996 |
| 3 authors: | | | |
| abstract: | In this paper we discuss how the injector specifications of a 2nd-generation plasma beat wave accelerator (PBWA) experiment can be achieved by a photo-injector. Typical required bunch lengths (FWHM) are 50 microns with 15 pC bunch charge. We analyze the possibility of generating such short electron bunches directly from a photoinjector by illuminating a photocathode in an RF electron gun with a phase-locked 160-fs laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through the photo-injector. We provide a set of analytical scaling laws, as well as a comparison with detailed simulations of the beam dynamics. 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. (17 References). |
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| title: | Analytical model for emittance compensation in RF photo-injectors |
| format: | conference procceeding |
| conference: | 1995 Particle Accelerator Conference |
| year: | 1995 |
| 2 authors: | | |
| abstract: | In this paper we present a new model to represent analytically the transverse beam dynamics in RF photo-injectors. It consists basically of an enhanced Kim's model, with incorporation of RF ponderomotive focusing effects, external magnetic focusing and a perturbative treatment of space charge along the beam envelope. Applying the resulting formulas it is possible to predict with high accuracy the transverse beam envelope behaviour in a multi-cell RF gun, as well as the operating conditions to achieve space charge emittance compensation according to Carlsten's scheme. The agreement with sophisticated numerical simulations is really quite satisfactory, as well as the match with experimental measurements of the predicted operating range for emittance compensation. (7 References). |
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| title: | Transverse particle motion in radio-frequency linear accelerators |
| format: | unknown |
| year: | 1994 |
| 2 authors: | | |
| 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. |
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| title: | Transverse Particle Motion in Radio-Frequency Linear Accelerators |
| format: | preprint |
| year: | 1993 |
| 2 authors: | | |
| 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 derived for the motion in a periodic accelerating cavity system, and solved exactly in the ultra-relativistic limit. These soluction, along with an impulse treatment of the transients at the entrance and exit and exit of the linac cavities, allow derivation of a linear transport matrix throuigh the cavity. This generalized matrix is imporved over previously derived results in that it is applicable to both travelling 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. |
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| title: | Design of a High Brightness RF Photoinjector for the SLAC Linac Coherent Light Source |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 2 authors: | | |
| abstract: | The electron injector for the SLAC Linear Coherent Light Source[l] (LCLS) must produce a low jitter, high brightness beam. This beam must be accelerated and longitudinally compressed to yield a sub-picosecond beam which radiates a burst of self-amplified spontaneous emission xrays upon passing through a long undulator. As the gain of this amplifier is very sensitive to the emittance, energy spread and peak current the electron source and subsequent transport, acceleration, and compression systems must reproducibly give a very high quality beam. The conceptual design of an rf photocathode gun which satisfies the requirements of the LCLS is presented here. While the design peak current emitted by this gun is above 200 A, the requirements of gain length in the undulator are such that the beam must undergo longitudinal compression to raise the peak current by an order of magnitude. This compression is very much dependent on both the phase of the accelerating rf wave and the longitudinal wake-fields in the linac, and so the final bunch length will not be reproducible if the time of beam emission (laser beam injection) and/or the charge per bunch have large variations. Because of concerns on reliability and feasibility of the photoinjector, a design which takes maximum advantage of proven technology, and recent experience in photoinjector development has been explored, and is outlined below. |
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| title: | Recent results and future perspectives of the SPARC project |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | 2008 |
| 77 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive 500 nm FEL experiments in various configurations, a Thomson backscattering source and a plasma accelerator experiment (these last two ones jointly with the project PLASMONX). The SPARC photoinjector is also the test facility for the recently approved VUV FEL project named SPARX. As a first stage of the commissioning, a complete characterization of the photoinjector has been accomplished with a detailed study of the emittance compensation process downstream the gun-solenoid system: this lead to the first direct experimental demonstration of emittance oscillations in a drift. The second stage of the commissioning, that is currently underway, foresees a detailed analysis of the beam matching with the linac in order to confirm the theoretically prediction of emittance compensation based on the “invariant envelope” matching and the demonstration of the “velocity bunching” technique in the linac. SASE and SEEDING experiments are foreseen by the end of the current year. In this paper we report the experimental results obtained so far and the scientific program for the near future. |
| keywords: | pbpl_pub |
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| title: | High brightness electron beam emittance evolution measurements in an rf photoinjector |
| format: | journal article |
| year: | 2008 |
| 48 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The new generation of linac injectors driving free electron lasers in the self-amplified stimulated emission (SASE-FEL) regime requires high brightness electron beams to generate radiation in the wavelength range from UV to x rays. The choice of the injector working point and its matching to the linac structure are the key factors to meet this requirement. An emittance compensation scheme presently applied in several photoinjectors worldwide is known as the ‘‘Ferrario’’ working point. In spite of its great importance there was, so far, no direct measurement of the beam parameters, such as emittance, transverse envelope, and energy spread, in the region downstream the rf gun and the solenoid of a photoinjector to validate the effectiveness of this approach. In order to fully characterize the beam dynamics with this scheme, an innovative beam diagnostic device, the emittance meter, consisting of a movable emittance measurement system, has been designed and built. With the emittance meter, measurements of the main beam parameters in both transverse phase spaces can be performed in a wide range of positions downstream the photoinjector. These measurements help in tuning the injector to optimize the working point and provide an important benchmark for the validation of simulation codes. We report the results of these measurements in the SPARC photoinjector and, in particular, the first experimental evidence of the double minimum in the emittance oscillation, which provides the optimized matching to the SPARC linac. |
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| title: | Status of the SPARC-X Project |
| format: | journal article |
| year: | 2007 |
| 97 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | SPARC-X is a two branch project consisting in the SPARC test facility dedicated to the development and test of critical subsystems such as high brightness photoinjector and a modular expandable undulator for SASE-FEL experiments at 500 nm with seeding, and the SPARX facility aiming at generation of high brilliance coherent radiation in the 1.5-13 nm range, based on the achieved expertise. The projects are supported by MIUR (Research Department of Italian Government) and Regione Lazio. SPARC has completed the commissioning phase of the photoinjector in November 2006. The achieved experimental results are here summarized together with the status of the second phase commissioning plans. The SPARX project is based on the generation of ultra high peak brightness electron beams at the energy of 1 and 2 GeV generating radiation in the 1.5-13 nm range. The construction is at the moment planned in two steps starting with a 1 GeV Linac. The project layout including both RF-compression and magnetic chicane techniques has been studied. |
| keywords: | pbpl |
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| title: | Status of the SPARC Photoinjector |
| format: | journal article |
| year: | 2006 |
| 69 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The SPARC Project is starting the commissioning of its photo-injector. RF gun, RF sources, RF network and control, power supplies, emittance meter, beam diagnostics and control to measure the RF gun beam have been installed. The photocathode drive laser has been characterized in terms of pulse shape and quality. We will report also about first tests made on RF gun and on the emittance meter device. Additional R&D on X-band and S-band structures for velocity bunching are in progress, as well as studies on new photocathode materials. We will also discuss studies on solenoid field defects, beam based alignments and exotic electron bunch production via blow-out of short laser pulses. |
| keywords: | pbpl |
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| title: | Electron Beam-laser Interaction near the Cathode in a High Brightness Photoinjector |
| format: | journal article |
| year: | 2006 |
| 4 authors: | | | | |
| abstract: | The production of high charge short bunches in a high brightness photoinjector requires laser pulses driving the cathode with GW range peak power on a mm spot size. The resulting transverse electric field experienced by the electron beam near the cathode is of the order of 200-500 MV/m, well in excess of a typical RF accelerating field of 50-100 MV/m. We present here a preliminary study of the resultant beam dynamics. Simulations including the electron beam-laser interaction have been performed with the code HOMDYN taking into account the superposition of incident and reflected laser pulses as well as space charge fields. Under this conditions the emittance degradation is negligible, as predicted by analytical methods, but a longitudinal charge modulation occurs on the scale of the laser wavelength, in case of oblique incidence, driven by the longitudinal component of the laser field. Charge modulation is transformed into energy modulation via the space charge field, which may produce enhanced microbunching effects when the beam is further compressed in a magnetic chicane. |
| keywords: | pbpl |
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| title: | Status Report on SPARC Project |
| format: | journal article |
| year: | |
| 96 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We review the status of FEL source activity of the ongoing SPARC FEL experiment, developed within the framework of a collaboration among ENEA, CNR, INFN, INFM, Sincrotrone Trieste and University of Rome Tor Vergata. The project is aimed at realising a SASE-FEL source, operating in the visible (around 500 nm), with an extended range of tunability down to the VUV (100 nm) by the use of the mechanism of non-linear harmonic generation. The development of the relevant activities foresees the realisation of an advanced 150 MeV photo- injector source, aimed at producing a high brightness electron beams, needed to drive a SASE-FEL experiment, and a 14 m long undulator. We present the status of the design and construction of SPARC FEL device. In particular we discuss the choice of the project parameters, their optimisation and the sensitivity of the SPARC performance to any parameter variation. We will show, using start-to-end simulations, what is the impact of the e- beam and of the undulator parameters on the characteristics of the output laser field and in particular on the amount of the non-linearly generated power at higher harmonics. |
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| title: | Single spike operation in SPARC SASE-FEL |
| format: | conference procceeding |
| conference: | EPAC 2008 |
| year: | |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | The single spike operation regime has been analyzed in the case of the SPARC injector and freeelectron-laser. Four different beams at 50 pC are studied, with different production condition and performance. |
| keywords: | pbpl_pub |
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