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53 papers
| title: | Experimental Generation and Characterization of Uniformly Filled Ellipsoidal Electron-Beam Distributions |
| format: | journal article |
| year: | 2008 |
| 5 authors: | | | | | |
| abstract: | For 40 years, uniformly filled ellipsoidal beam distributions have been studied theoretically, as they hold the promise of generating self-fields linear in the coordinate offset in all three directions. Recently, a scheme for producing such distributions, based on the strong longitudinal expansion of an initially very short beam under its own space-charge forces, has been proposed. In this Letter we present the experimental demonstration of this scheme, obtained by illuminating the cathode in a rf photogun with an ultrashort laser pulse ( |
| keywords: | pbpl prl |
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| title: | Optinum Beam Creation In Photoinjectors Using Space-Charge Expansion |
| format: | conference procceeding |
| conference: | |
| year: | 2006 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | It has recently been shown that by illuminating a photocathode 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 modern photoinjectors. It is seen that the two processes are compatible, with simulations indicating that a very high brightness beam can be obtained. The scheme has produced stimulus for a series of experiments at the SPARC injector at Frascati in 2006-2007. An initial time-resolved experiment has been performed involving Cerenkov radiation produced at an aerogel. We discuss the results of this preliminary experiment, as well as plans for future experiments to resolve the ellipsoidal bunch shape at low energy. Future measurements at high energy based on fs resolution RF sweepers are discussed. |
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| title: | EXPERIMENTAL TESTING OF DYNAMICALLY OPTIMIZED PHOTOELECTRON BEAMS |
| format: | conference procceeding |
| conference: | Erice 2005 |
| year: | 2006 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | We discuss the design of and initial results from an experiment in space-charge dominated beam dynamics which explores a new regime of high-brightness electron beam generation at the SPARC (located at INFN-LNF, Frascati) photoinjector. The scheme under study employs the natural tendency in intense electron beams to configure themselves to produce a uniform density, giving a nearly ideal beam from the viewpoint of space charge-induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation, We show that the existing infrastructure at SPARC is nearly ideal for the proposed tests, and that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time-dependent, aerogel-based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded. |
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| title: | High Energy Gain of Trapped Electrons in a Tapered, Diffraction-Dominated Inverse-Free-Electron Laser |
| format: | preprint |
| year: | 2005 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | Energy gain of trapped electrons in excess of 20 MeV has been demonstrated in an Inverse-Free- Electron-Laser (IFEL) accelerator experiment. A 14.5 MeV electron beam is copropagated with a 400 GW CO2 laser beam in a 50 cm long undulator strongly tapered in period and ¯eld amplitude. The Rayleigh range of the laser, » 1.8 cm, is much shorter than the undulator length yielding a di®raction-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 ¯rst 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. |
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| title: | Higher harmonic inverse free-electron laser interaction |
| format: | journal article |
| year: | 2005 |
| 3 authors: | | | |
| 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. |
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| title: | Velocity bunching of high-brightness electron beams |
| format: | journal article |
| year: | 2005 |
| 11 authors: | | | | | | | | | | | |
| 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. |
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| title: | Sextupole Correction of the Longitudinal Transport of Relativistic Beams in Dispersionless Translating Sections |
| format: | journal article |
| year: | |
| 6 authors: | | | | | | |
| abstract: | We examine the use of sextupole magnets to correct nonlinearities in the longitudinal phase space transformation of a relativistic beam of charged particles in a dispersionless translating section, or dogleg. Through heuristic analytical arguments and examples derived from recent experimental endeavors and augmented by simulations using the particle tracking codes PARMELA and ELEGANT, sextupole corrections are found to be potentially useful in facilitating the use of such structures for beam compression or for shaping the current profile of the beam, by manipulation of the second-order longitudinal dispersion (or T566). Recent experimental evidence of the use of sextupoles to manipulate second-order horizontal and longitudinal dispersion of the beam is presented. The theoretical and experimental results indicate that these manipulations could be used to create an electron bunch with a current profile having a long ramp followed by a sharp cut-off, which is optimal for driving large amplitude wake fields in a plasma wake field accelerator. |
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| title: | Ultra-High Density Electron Beams for Beam Radiation and Beam Plasma Interaction |
| format: | conference procceeding |
| conference: | 2005 Particle Accelerator Conference |
| year: | |
| 11 authors: | | | | | | | | | | | |
| abstract: | Current and future applications of high brightness electron beams, which include advanced accelerators such as the plasma wake-field accelerator (PWFA) and beam radiation interactions such as inverse-Compton scattering (ICS), require both transverse and longitudinal beam sizes on the order of tens of microns. Ultra-high density beams may be produced at moderate energy (50 MeV) by compression and subsequent strong focusing of low emittance, photoinjector sources. We describe the implementation of this method used at the PLEIADES ICS x-ray source in which the photoinjector-generated beam has been compressed to 300 fsec duration using the velocity bunching technique and focused to 20 um rms size using an extremely high gradient, permanent magnet quadrupole (PMQ) focusing system. |
| keywords: | pbpl |
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| title: | Enhanced Acceleration of Injected Electrons in a Laser Beatwave Induced Plasma Channel |
| format: | preprint |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | Enhanced energy gain of externally injected electrons by a ~3-cm long, high-gradient relativistic plasma wave (RPW) is demonstrated. Using a CO2 laser-beatwave of duration longer than the ion motion time across the laser spot size, a laser self-guiding process is initiated in a plasma channel. Guiding compensates for ionization-induced defocusing (IID) creating a longer plasma, which extends the interaction length between electrons and the RPW. In contrast to a maximum energy gain of 10 MeV when IID is dominant, the electrons gain up to 38 MeV energy in a laser beatwave induced plasma channel. PACS: 52.35Mw, 52.38Hb, 52.38Kd |
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| title: | A Helical Undulator Wave-guide Inverse Free-Electron Laser |
| format: | conference procceeding |
| conference: | |
| year: | 2004 |
| 8 authors: | | | | | | | | |
| abstract: | With recent success in high gradient, high-energy gain IFEL experiments at the UCLA Neptune Laboratory, future experiments are now being contemplated. The Neptune IFEL was designed to use a tightly focused, highly diffracting, near-TW peak power 10 micron laser. This choice of laser focusing, driven by power-handling limitations of the optics near the interaction region, led to design and use of a very complex undulator, and to sensitivity to both laser misalignment and focusing errors. As these effects limited the performance of the IFEL experiment, a next generation experiment at Neptune has been studied which avoids the use of a highly diffractive laser beam through use of a waveguide. We discuss here the choice of low-loss waveguide, guided mode characteristics and likely power limitations. We also examine a preferred undulator design, which is chosen to be helical in order to maximize the acceleration achieved for a given power. With the limitations of these laser and undulator choices in mind, we show the expected performance of the IFEL using 1D simulations. Three-dimensional effects are examined, in the context of use of a solenoid for focusing and acceleration enhancement. |
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| title: | Non-Resonant Beat-Wave Excitation of Constant Phase-Velocity, Relativistic Plasma Waves for Charged-Particle Acceleration |
| format: | journal article |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | The nonresonant beat-wave excitation of relativistic plasma waves is studied in two-dimensional simulations and experiments. It is shown through simulations that, as opposed to the resonant case, the accelerating electric fields associated with the nonresonant plasmons are always in phase with the beat-pattern of the laser pulse. The excitation of such nonresonant relativistic plasma waves is shown to be possible for plasma densities as high as 14 times the resonant density. The density fluctuations and the fields associated with these waves have significant magnitudes, facts confirmed experimentally using collinear Thomson scattering and electron injection, respectively. The applicability of these results towards eventual phase-locked acceleration of prebunched and externally injected electrons is discussed. |
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| title: | Experiments on laser driven beatwave acceleration in a ponderomotively formed plasma channel |
| format: | journal article |
| year: | 2004 |
| 10 authors: | | | | | | | | | | |
| abstract: | A 10 ps long beam of 12 MeV electrons is externally injected into a ~3-cm long plasma beatwave excited in a laser ionized hydrogen gas. The electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that when the effective plasma wave amplitude-length product is limited by ionization-induced defocusing (IID), acceleration of electrons is significantly enhanced by using a laser pulse with a duration longer than the time required for ions to move across the laser spot size. Both experiments and two-dimensional simulations reveal that, in this case, self-guiding of the laser pulse in a ponderomotively formed plasma channel occurs. This compensates for IID and drives the beatwave over the longer length compared to when such a channel is not present. |
| keywords: | pbpl |
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| title: | Beam Shaping and Compression Scheme for the UCLA Neptune Laboratory |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 4 authors: | | | | |
| abstract: | We have recently added a dispersionless translating section to the UCLA Neptune linear accelerator beamline. This new section of beamline will serve as a venue for beam shaping and compression experiments using the 14MeV electron beam produced by the UCLA Neptune PWT linac and newly installed photoinjector. An examination of the first and second-order optics indicates that when certain nonlinear effects are minimized through the use of sextupole magnets, the longitudinal dispersion is dominated by a negative R56 which, for an appropriately chirped initial beam, can be used to create a ramped beam of a few picosecond duration that would be ideal for driving large amplitude wake fields in a plasma and producing high transformer ratios. The beamline is now in operation. Preliminary data indicate that the beamline optics are well-predicted by simulation and that sextupoles can be used successfully to eliminate nonlinear horizontal dispersion. Future experiments are planned for measuring beam compression (using CTR autocorrelation) and doing longitudinal phase space tomography (using a transverse deflecting cavity). |
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| title: | Horizontal Phase-Space Distortions Arising from Magnetic Pulse Compression of an Intense, Relativistic Electron Beam |
| format: | journal article |
| year: | 2003 |
| 4 authors: | | | | |
| 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. |
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| title: | Status of the Inverse Free Electron Laser Experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 10 authors: | | | | | | | | | | |
| abstract: | We report on the status of the Inverse Free Electron Laser accelerator experiment under construction at the UCLA Neptune Laboratory. This experiment will use a 400 GW CO2 laser to accelerate through a tapered undulator an electron beam from 14.5 MeV up to 55 MeV. The scheme proposed is the diffraction dominated IFEL interaction where the Rayleigh range of the laser beam is 3.5 cm, much shorter than the interaction length (the undulator length is 50 cm). The undulator is strongly tapered in both field and period. The present status of the experiment is reported. |
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| title: | Acceleration of Injected Electrons In A Laser Beatwave Experiment |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 10 authors: | | | | | | | | | | |
| abstract: | Plasma-based accelerators of particles are of great interest because plasmas can sustain very strong electric fields. They are utilizing a relativistic plasma wave with a phase velocity close to the speed of light driven by a high-power laser beam. The Neptune Laboratory at UCLA is being used for plasma beatwave acceleration of injected electrons. Here, a two-wavelength laser pulse (frequencies w1,w2) resonantly drives a longitudinal electron plasma wave of frequency equal to w1-w2, providing a field strength of GeV/m and, therefore, accelerates an injected electron beam at this very high gradient. A 10 ps beam of 12 MeV electrons is loaded in a 3-cm long plasma beatwave accelerator driven by a TW CO2 laser pulse. At the resonance condition, the electrons have been accelerated to 50 MeV with a gradient of ~1.3 GeV/m. It is shown that for large volume diffraction limited plasmas, when efficiency of the plasma wave excitation is restricted by ionization-induced refraction, acceleration of electrons is enhanced significantly by using asymmetric (fast front and slow fall) long pulses. 2D PIC simulations revealed that guiding of the laser pulse in a ponderomotive, self-induced ion channel, formed ~200 ps after the field ionization, allows compensation for the ionization-induced defocusing and efficient driving of the beatwave over the entire length. |
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| title: | Pulse Compression via Velocity Bunching with the LLNL Thomson X-Ray Source Photoinjector |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 5 authors: | | | | | |
| abstract: | We report the compression of a high brightness, relativistic electron beam to rms lengths below 300 femtoseconds using the velocity compression technique in the LLNL Thomson X-ray source photoinjector. The results are consistent with analytical and computational models of this process. The emittance evolution of the beam during compression is investigated in simulation and found to be controllable with solenoid focusing. |
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| title: | Velocity Bunching Experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 3 authors: | | | |
| abstract: | In this paper we describe the rectilinear compression experiment at the Neptune photoinjector at UCLA. The electron bunches have been shortened to sub-ps pulse length by chirping the beam energy spectrum in a short S-band high gradient standing wave RF cavity and then letting the electrons undergo velocity compression in the following rectilinear drift. Using a standard Martin Puplett interferometer to characterize coherent transition radiation from the beam, we measured bunch lengths as short as 0.4 ps with compression ratio in excess of 10 for an electron beam of 7 MeV energy and charge up to 300 pC. |
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| title: | Inverse Free Electron Laser Experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 6 authors: | | | | | | |
| abstract: | We present an Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Laboratory. This experiment will use a 1 TW CO2 laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 5 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the |
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| title: | Velocity bunching experiment at the Neptune Laboratory |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 5 authors: | | | | | |
| abstract: | |
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| title: | Bunched Beam Injection in a Plasma Accelerator |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 6 authors: | | | | | | |
| abstract: | An experiment on phase-locked injection of ~ 100 fs electron bunches in a plasma beat wave accelerator is presented. We consider using an IFEL microbunching technique to produce ultrashort electron bunches prebunched at the exact wavelength of the plasma wave 340 Jim (~lTHz). It is proposed to generate 100 MW of 1 THz radiation by difference frequency generation in a nonlinear crystal, mixing the same two CC>2 lines as used to drive the plasma accelerator. |
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| title: | A THz radiation driven IFEL as a phaselocked prebuncher for a plasma beat-wave accelerator |
| format: | conference procceeding |
| conference: | International Conference on Lasers 2001 |
| year: | 2002 |
| 6 authors: | | | | | | |
| abstract: | To obtain a high quality electron beam with small energy spread in the laser driven plasma accelerator, the electrons have to be prebunched at the scale of the plasma wavelength. We study the feasibility of an experiment where an inverse free electron laser (IFEL) is used to bunch the electron beam before the injection into a plasma beatwave accelerator. It is suggested to drive the IFEL prebuncher by a THz seed radiation phase-locked to the electromagnetic beatwave through difference frequency generation process in a nonlinear crystal. Design and numerical simulations for this experiment are presented. |
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| title: | An undulator with nonadiabatic tapering for the IFEL project |
| format: | conference procceeding |
| conference: | 23rd International Free Electron Laser Conference |
| year: | 2002 |
| 6 authors: | | | | | | |
| abstract: | We describe the design of a planar undulator with unusually strong tapering, for the inverse FEL experiment (on the IFEL experiment at the UCLA Neptune Lab. Presented at the 2001 Particle Accelerator Conference, June 18-22, 2001, Chicago, Illinois) to be carried out in Neptune Lab. (Nucl. Instr. and Meth. A 410 (1998) 437) at UCLA. A powerful TW CO_2 laser will be used to accelerate electrons up to 50-60 MeV in 50 cm long undulator. A strong undulator tapering is needed because of the short Rayleigh length of the laser beam. Both the magnetic field and the undulator period are tapered to provide synchronicity of the laser beam interaction with a captured electron bunch along the whole undulator length. The most critical part of the undulator is the region near the laser focus. The main characteristics of the IFEL, such as the percentage of trapped electrons, energy of accelerated electrons and sensitivity to the laser focus transverse position, are given. The general principles of the design of this undulator construction can also be useful for high efficiency FEL amplifiers of intense laser modes. |
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| title: | Commissioning of the Neptune photoinjector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 9 authors: | | | | | | | | | |
| abstract: | The status of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The components of the photoinjector: the RF gun and booster linac, chicane compressor, and beam diagnostic systems are described. Measurement techniques used to diagnose the short pulse length, high brightness beam are detailed and measurements of emittance and pulse compression are given. The effect of the pulse compressor on transverse emittance is explored. (11 References). |
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| title: | On the IFEL experiment at the UCLA Neptune Lab |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 6 authors: | | | | | | |
| abstract: | We present an inverse free electron laser accelerator proposed for construction at the UCLA Neptune Lab. This experiment will use a 1TW CO/sub 2/ laser to accelerate through two strongly tapered undulators an electron beam from 16 MeV up to 55 MeV. The scheme proposed is the diffraction dominated IFEL interaction. The Raleigh range of the laser beam is about 2 cm, much shorter than the interaction length (the undulator length is 50 cm). In this regime adiabatic capture is possible in the first part of the undulator. In the focus region, we propose a solution to the problem of the dephasing between electrons and photons due to the Guoy phase shift. Ponderomotive effects and implications for tolerances are also studied. (13 References). |
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| title: | Initial gain measurements of an 800 nm SASE FEL, VISA |
| format: | conference procceeding |
| conference: | 22nd International Free Electron Laser Conference |
| year: | 2001 |
| 26 authors: | | | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The visible to infrared SASE amplifier (VISA) FEL is designed to obtain high gain at a radiation wavelength of 800 nm. The FEL uses the high brightness electron beam of the accelerator test facility (ATF), with energy of 72 MeV. VISA uses a novel, 4 m long, strong focusing undulator with a gap of 6 mm and a period of 1.8 cm. To obtain large gain the beam and undulator axis have to be aligned to better than 5 mu m. Results from initial measurements on the alignment, gain, and spectrum will be presented and compared to theoretical calculations and simulations. (10 References). |
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| title: | Commissioning and measurements of the Neptune photo-injector |
| format: | conference procceeding |
| conference: | 9th Advanced Accelerator Concepts Workshop |
| year: | 2001 |
| 6 authors: | | | | | | |
| abstract: | The photo-injector for the Neptune Advanced Accelerator Laboratory is introduced. Its component parts, including the radio frequency gun, photo-cathode drive laser system, booster linac, RF system, chicane compressor, beam diagnostics, and control system are described. The injector is designed to produce high brightness, short pulse electron beams. Measurements of the photo-injector beams including quantum efficiency, emittance, pulse length, and pulse compression are presented. (21 References). |
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| title: | IFEL experiment at the Neptune Lab |
| format: | conference procceeding |
| conference: | 9th Advanced Accelerator Concepts Workshop |
| year: | 2001 |
| 2 authors: | | |
| abstract: | We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out successfully. This experiment is intended to achieve a 100 MeV energy gain, staging two IFEL modules. It will use a 16 MeV electron beam, a 1 TW CO/sub 2/ laser and two different tapered helical undulators. The problem of refocusing both laser and electron beam is analyzed in detail. A preliminary beam-line layout and numerical simulation are presented. (11 References). |
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| title: | Commissioning of the Neptune Photoinjector |
| format: | conference procceeding |
| conference: | APS April Meeting |
| year: | 2000 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | The status of the commissioning of the rf photoinjector in the Neptune advanced accelerator laboratory is discussed. The component parts of the photoinjector, the rf gun, photocathode drive laser system, booster linac, rf system, chicane compressor, beam diagnostics systems, and control system are described. Recent improvements in the rf gun, rf timing, and chicane compressor systems are detailed. This injector is designed to produce short pulse length, high brightness electron beams. Experiments planned for the immediate future are described. Initial measurements of various beam parameters are presented. |
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| title: | Electron Beam Photocathode Cleaning |
| format: | conference procceeding |
| conference: | APS April Meeting |
| year: | 2000 |
| 7 authors: | | | | | | | |
| abstract: | We are experimenting with low energy electron beams as a means of cleaning and improving the quantum efficiency of metallic photocathodes. Electron beam surface cleaning has been used successfully in electron cooling devices at Fermilab (S. Nagaitsev) and Novosibirsk (A.N. Sharapa and A.V. Shemyakin). The cooling device data indicates that a 2 mA h/cm2 specific dose of 3 keV electrons on the surface of the photocathode will produce a surface with an outgas rate at least one order of magnitude lower than a 24 hour 400 |
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| title: | IFEL experiment at Neptune Lab |
| format: | conference procceeding |
| conference: | 2000 European Particle Accelerator Conference |
| year: | 2000 |
| 2 authors: | | |
| abstract: | We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out successfully. This experiment is intended to achieve a 100 MeV energy gain, staging two IFEL modules. It will use a 16 MeV electron beam, a 1 TW CO2 laser and two different tapered helical undulators. The problem of refocusing both laser and electron beam is analysed in detail. A preliminary beam-line layout and numerical simulations are presented. |
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| title: | A two stage IFEL accelerator |
| format: | conference procceeding |
| conference: | APS April Meeting |
| year: | 2000 |
| 2 authors: | | |
| abstract: | We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out succesfully. This experiment is intended to achieve a 100 Mev energy gain, staging two IFEL modules. It will use the 16 Mev electron beam produced by the Neptune linac, the 1 TW MARS CO2 laser and two different tapered undulators. The problem of refocusing both laser and electron beam is analyzed in detail. A preliminary beamline layout and numerical simulations are presented. |
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| title: | Status and initial commissioning of a high gain 800 nm SASE FEL |
| format: | conference procceeding |
| conference: | 21st International Free Electron Laser Conference |
| year: | 2000 |
| 22 authors: | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | We describe the status and initial commissioning of the visible to infrared SASE amplifier (VISA) experiment. VISA uses a strong focusing 4 m undulator, the Brookhaven National Laboratory ATF linac with an energy of 72 MeV, and a photoinjector electron source. The VISA fundamental radiation wavelength is near 800 nm and the power expected at saturation is near 60 MW. Power, angular and spectral measurements are planned for the VISA radiation and these results will be analyzed and compared with SASE FEL theory and computer simulation. In addition, the induced electron beam micro-bunching will be measured using coherent transition radiation. (12 References). |
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| title: | TREDI: fully 3D beam dynamics simulation of RF guns, bendings and FELs |
| format: | unknown |
| year: | 1999 |
| 3 authors: | | | |
| 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. |
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| title: | Photon beam diagnostics for VISA FEL |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | The VISA (Visible to Infrared SASE Amplifier) project is designed to be a SASE-FEL driven to saturation in the sub-micron wavelength region. Its goal is to test various aspects of the existing theory of self-amplified spontaneous emission, as well as numerical codes. Measurements include: angular and spectral distribution of the FEL light at the exit and inside of the undulator; electron beam micro-bunching using CTR; single-shot time resolved measurements of the pulse profile, using an auto-correlation technique and FROG algorithm. The diagnostics are designed to provide maximum information on the physics of the SASE-FEL process, to ensure a close comparison of the experimental results with theory and simulations. (9 References). |
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| title: | Commissioning of the Neptune photoinjector |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 21 authors: | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The status of the commissioning of the RF photoinjector in the Neptune advanced accelerator laboratory is discussed. The component parts of the photoinjector, the RF gun, photocathode drive laser system, booster linac, RF system, chicane compressor, beam diagnostics systems, and control system are described. This injector is designed to produce short pulse length, high brightness electron beams. Experiments planned for the immediate future are described. Initial measurements of various beam parameters are presented. (10 References). |
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| title: | Diamagnetic fields due to finite-dimension intense beams in high-gain free-electron lasers |
| format: | unknown |
| year: | 1998 |
| 2 authors: | | |
| 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). |
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