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36 papers
| title: | Production of High Harmonic X-ray Radiation from Non-linear Thomson Scattering at LLNL PLEIADES |
| format: | conference procceeding |
| conference: | 2005 Particle Accelerator Conference |
| year: | 2005 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We describe an experiment for production of high harmonic x-ray radiation from Thomson backscattering of an ultra-short high power density laser by a relativistic electron beam at the PLEIADES facility at LLNL. In this scenario, electrons execute a ``figure-8'' motion under the influence of the high-intensity laser field, where the constant characterizing the field strength is expected to exceed unity: $a_{L}=eE_{L}/m_{e}c\omega_{L}\geq1$. With large $a_{L}$ this motion produces high harmonic x-ray radiation and significant broadening of the spectral peaks. This paper is intended to give a layout of the PLEIADES experiment, along with progress towards experimental goals. |
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| title: | Adjustable, short focal length permanent-magnet quadrupole based electron beam final focus system |
| format: | journal article |
| year: | 2005 |
| 9 authors: | | | | | | | | | |
| 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. |
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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: | Short-pulse, high-brightness X-ray production with the PLEIADES Thomson-scattering source |
| format: | unknown |
| year: | 2004 |
| 1 author: | |
| abstract: | PLEIADES is a compact, tunable, high-brightness, ultra-short-pulse, Thomson-scattering X-ray source. Picosecond pulses of hard X-rays (10 |
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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: | Generation of High Brightness X-Rays with the PLEIADES Thomson X-Ray Source |
| format: | conference procceeding |
| conference: | 2003 Particle Accelerator Conference |
| year: | 2003 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | The use of short laser pulses to generate high peak intensity, ultra-short x-ray pulses enables exciting new experimental capabilities, such as femtosecond pump-probe experiments used to temporally resolve material structural dynamics on atomic time scales. PLEIADES (Picosecond Laser Electron InterAction for the Dynamic Evaluation of Structures) is a next generation Thomson scattering x-ray source being developed at Lawrence Livermore National Laboratory (LLNL). Ultra-fast picosecond x-rays (10-200 keV) are generated by colliding an energetic electron beam (20-100 MeV) with a high intensity, sub-ps, 800 nm laser pulse. The peak brightness of the source is expected to exceed 1020 photons/s/0.1 bandwidth/mm2/mrad2. Simulations of the electron beam production, transport, and final focus are presented. Electron beam measurements, including emittance and final focus spot size are also presented and compared to simulation results. Measurements of x-ray production are also reported and compared to theoretical calculations. |
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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: | Ultrafast materials probing with the LLNL Thomson X-ray source |
| format: | conference procceeding |
| conference: | 2002 Linear Accelerator Conference |
| year: | 2002 |
| 24 authors: | | | | | | | | | | | | | | | | | | | | | | | | |
| abstract: | The use of short laser pulses to generate very high brightness, ultra short (fs to ps) x-ray pulses is a topic of great interest. In principle, femtosecond-scale pump-probe experiments can be used to temporally resolve structural dynamics of materials on the time scale of atomic motion. The development of sub?ps x-ray pulses will make possible a wide range of materials and plasma physics studies with unprecedented time resolution. PLEIADES (Picosecond Laser Electron Interaction for Dynamic Evaluation of Structures), the Thomson scattering project at LLNL, will provide such a novel x-ray source of high power using short laser pulses and a high brightness, relativistic electron bunch. The system is based on a 5 mm-mrad normalized emittance photoinjector, 100 MeV electron RF linac, and a 300 mJ, 35 fs solid-state laser system. PLEIADES will produce ultra fast pulses with x-ray energies (60 keV) capable of probing into high-Z metals. |
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| title: | Creation, Manipulation, and Diagnosis of Intense, Relativistic Picosecond Photo-electron Beams |
| format: | thesis |
| year: | 2002 |
| 1 author: | |
| abstract: | The radio frequency photoinjector is the pre-eminent source for advanced electron beam applications that require extremely high phase space density (high brightness) beams. Because of their high phase space density, the collective fields generated by photoinjector beams dominate their behavior. These space-charge fields influence every aspect of the beam's handling, including its acceleration, measurement, and transport. The effects of spece-charge must be carefully considered in all of these beam handling procedures in order to deliver the highest brightness beams possible. This dissertation investigates the space-charge dominated physical processes involved in the acceleration and propagation, emittance measurement, and magnetic compression fo photoinjector beams. In the analysis of the behavior of these beams, emphasis is placed on the techniques used to compensate for space-charge forces, and maximize beam brightness. The rectilinear motion of a space-charge cominated beam is analyzed, including both linear and nonlinear self forces, in order to determine the evolution of the beam's transverse emittance as it is accelerated and transported through the photoinjector. It is found that the emittance can be made to oscillate by judicious use of external forces, and that this oscillation can be manipulated to minimize the beam's emittance, compensating for the effects of both linear and nonlinear space-charge forces, at a given location of interest. The creation of a high brightness beam in the presence of emittance oscillations is critically dependent on phase space diagnosis. Thus the measurement of emittance of intense beams is investigated experimentally, theoretically, and in simulation, for quadrupole scanning and multi-slit based measurement techniques. The quadrupole scanning method is found to have systematic errors for space-charge dominated beams, and experimental measurements using this technique give consistently higher emittance values than both the slit-based measurements and simulations. Finally, the measurement of emittance growth and transverse phase space distortions induced by magnetic compression of the beam to sub-picosecond lengths is described. A clear bifurcation of the phase space is observed when the beam is strongly compressed. This effect is found to be correlated to the folding of the beam distribution in configuration space. |
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| title: | Space-charge effects in high brightness electron beam emittance measurements |
| format: | journal article |
| year: | 2002 |
| 4 authors: | | | | |
| 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. |
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| title: | Electron Beam Production and Characterization for the PLEIADES Thomson X-Ray Source |
| format: | conference procceeding |
| conference: | 10th Advanced Accelerator Concepts Workshop |
| year: | 2002 |
| 13 authors: | | | | | | | | | | | | | |
| abstract: | We report on the performance of an S-band RF photocathode electron gun and accelerator for operation with the PLEIADES Thomson x-ray source at LLNL. Simulations of beam production, transport, and focus are presented. It is shown that a 1 ps, 500 pC electron bunch with a normalized emittance of less than 5 Tcmm-mrad can be delivered to the interaction point. Initial electron measurements are presented. Calculations of expected x-ray flux are also performed, demonstrating an expected peak spectral brightness of 1020 photons/s/mm2/mrad2/0.1% bandwidth. Effects of RF phase jitter are also presented, and planned phase measurements and control methods are discussed. |
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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: | Emittance measurements of the space charge dominated Thomson source photoinjector |
| format: | conference procceeding |
| conference: | 2001 Particle Accelerator Conference |
| year: | 2001 |
| 4 authors: | | | | |
| abstract: | The photocathode rf gun test facility in Livermore National Laboratory's Thomson source is described. The quadrupole scan and slit based emittance measurement techniques are used to measure the emittance of the space charge dominated beam. Experimental results are compared with simulation and theoretical calculations. (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: | Nonequilibrium transverse motion and emittance growth in ultrarelativistic space-charge dominated beams |
| format: | journal article |
| year: | 2000 |
| 2 authors: | | |
| 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). |
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| title: | Non-equilibrium transverse motion and emittance growth in space-charge dominated beams |
| format: | conference procceeding |
| conference: | APS April Meeting |
| year: | 2000 |
| 2 authors: | | |
| abstract: | The transverse dynamics of space-charge dominated beams are investigated both analyitically 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. |
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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: | 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: | Single crystal copper photo-cathode in the BNL/SLAC/UCLA 1.6 cell RF gun |
| format: | conference procceeding |
| conference: | 2nd ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams |
| year: | 2000 |
| 3 authors: | | | |
| abstract: | Previous experimental measurements in the two dimensional (2D) variation of the quantum efficiency, QE, of a polycrystalline copper photo-cathode have measured a 25% variation in this quantity. Two possible causes of this 2D QE variation are contamination of the photo-emitting surface and the work function variation of copper due to crystal facet orientation. We report on the progress to eliminate the 2D QE variation due to the non-uniform crystal facet orientation of copper photo-emitters. This is accomplished by replacing the polycrystalline photo-emitter region of the cathode plane in a modified version of the BNL/SLAC/UCLA 1.6 cell rf gun with a thin disk of a single crystal copper Cu_100. In this paper we present a theoretical discussion on the effect that the crystal structure orientation of a photo-emitter has on the 2D QE. The manufacturing process used in the construction of the single crystal Cu_100 photo-cathode used in these photo-emission experiments are discussed. Preliminary experimental results are presented along with a discussion of our future experimental plans. |
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| title: | Nonequilibrium transverse motion and emittance growth in space-charge dominated beams |
| format: | conference procceeding |
| conference: | 2nd ICFA Advanced Accelerator Workshop on the Physics of High Brightness Beams |
| year: | 2000 |
| 2 authors: | | |
| 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. (13 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: | 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 effects of RF asymmetries on photoinjection beam quality |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 4 authors: | | | | |
| abstract: | A general multipole-based formalism to study the effects of RF asymmetries on the production of ultra-high brightness beam is presented, which employs both analytical and computational techniques. These field asymmetries can cause the degradation of beam emittance due to time dependent and nonlinear focusing effects. Two cases of interest are examined: the dipole asymmetry produced by a coupling slot in a standard high gradient RF gun, and the higher multipole content introduced by the support/cooling rods in a PWT structure. Practical implications of our results, as well as comparison to cold test and beam-based experimental tests, are discussed. (8 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: | Optimal scaled photoinjector designs for FEL applications |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 5 authors: | | | | | |
| abstract: | Much of the research and development surrounding the effort to create X-ray FELs based on the SASE process has centered on the creation of ultra-high brightness electron beam sources. The sources for existing short wavelength FEL designs, which employ RF photoinjector technology, have all been specified to contain 1 nC of charge. We show, by scaling existing designs, that this constraint causes the maximum beam brightness to be found when the RF wavelength is shortened to X-band. If, instead of holding the charge constant, we assume a certain RF wavelength device and then scale the charge, notable improvements in the beam brightness, and thus the FEL performance, are found. Charge scaling assumes that the density and aspect ratio of the beam stays constant as the charge is changed. If we relax the requirement of a constant aspect ratio in order to maximize the beam current and brightness by shortening the beam pulse, we find that the pulse lengthening due to space charge eventually brings this effort to a stop. The results of this investigation and their impact on SASE FEL design is discussed. |
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| title: | A measurement of high gain SASE FEL induced electron beam micro-bunching using coherent transition radiation |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 9 authors: | | | | | | | | | |
| abstract: | Coherent transition radiation (CTR) was used to study the longitudinal modulations of an electron beam exiting the UCLA/LANL high gain SASE FEL. The induced longitudinal micro-bunching of the electron beam at the exit of the undulator was measured with a frequency domain technique using the CTR emitted when this beam strikes a thin conducting foil. Formalisms for both CTR and SASE theories are related using the simulation code GINGER in which the SASE FEL gain of the output radiation and the micro-bunching of the electron beam are given. Experimental results from the CTR measurement will show the limit of standard transition radiation theory is being approached and new analysis is needed. (8 References). |
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| title: | Measured free-electron laser microbunching using coherent transition radiation |
| format: | conference procceeding |
| conference: | 20th International Free Electron Laser Conference |
| year: | 1999 |
| 9 authors: | | | | | | | | | |
| abstract: | The microbunch distribution of an electron beam exiting a SASE free-electron laser has been measured using the emitted coherent transition radiation (CTR) produced from a thin aluminum foil placed at the end of the undulator. The wavelength of the coherent transition radiation is shown to be the same as the FEL wavelength, and thus a measure of the beam microbunch spacing. Also, the study of the CTR linewidth and angular acceptance of the radiation captured are shown to be derived from this coherent radiative process. Scattering effects on the forward emitted transition radiation from the electron beam traversing an aluminum foil are also considered. (11 References). |
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| title: | Measurements of High Gain and Intensity Fluctuations in a Self-Amplified, Spontaneous-Emission Free-Electron Laser |
| format: | journal article |
| year: | 1998 |
| 12 authors: | | | | | | | | | | | | |
| 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. |
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| title: | Measurements of gain larger than 10(5) at 12 mu m in a self-amplified spontaneous-emission free-electron laser |
| format: | unknown |
| year: | 1998 |
| 14 authors: | | | | | | | | | | | | | | |
| 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). |
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| title: | Observation of Self-Amplified Spontaneous-Emission-Induced Electron-Beam Microbunching Using Coherent Transition Radiation |
| format: | unknown |
| year: | 1998 |
| 9 authors: | | | | | | | | | |
| 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. |
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| title: | The Neptune photoinjector |
| format: | conference procceeding |
| conference: | ICFA Second Generation Plasma Acceleration Workshop |
| year: | 1998 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | The RF photoinjector in the Neptune advanced accelerator laboratory, along with associated beam diagnostics, transport and phase-space manipulation techniques are described. This versatile injector has been designed to produce short-pulse electron beams for a variety of uses: ultra-short bunches for injection into a next-generation plasma beatwave acceleration experiment, space-charge dominated beam physics studies, plasma wake-field acceleration driver, plasma lensing, and free-electron laser microbunching techniques. The component parts of the photoinjector, the RF gun, photocathode drive laser systems, booster linac, RF system, chicane compressor, beam diagnostic systems, and control system, are discussed. The present status of photoinjector commissioning at Neptune is reviewed, and proposed experiments are detailed. (33 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: | Measurements of high gain and noise fluctuations in a SASE free electron laser |
| format: | conference procceeding |
| conference: | Workshop on Single Pass, High Gain FELs Starting from Noise Aiming at Coherent X-Rays |
| year: | 1997 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | We report measurements of large gain for a single pass Free Electron Laser operating in Self Amplified Spontaneous Emission (SASE) at 16 mu m 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. (11 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: | A high luminosity superconducting mini collider for phi meson production and particle beam physics |
| format: | conference procceeding |
| conference: | 1991 Particle Accelerator Conference |
| year: | 1991 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | A 510-MeV electron-positron collider has been proposed at the University of California at Los Angeles to study particle beam physics and phi-meson physics at luminosities larger than 1032 cm/sup -2/s/sup -1/. The collider consists of a single compact superconducting storage ring (SMC), with a bending field of 4 T and a current larger than 1 A. A discussion is presented of the main characteristics of this system and its major technical components: superconducting dipoles and the RF vacuum and injection systems. (6 References). |
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| title: | Progress in the Design of a DC FEL Power Source Using a Pelletron Driver |
| format: | conference procceeding |
| conference: | 1987 Particle Accelerator Conference |
| year: | 1987 |
| 7 authors: | | | | | | | |
| abstract: | We discuss progress in the design of a DC Free Electron Laser power source using a Pelletron electrostatic accelerator as a driver. Such a power source should deliver up to 200 kW DC power in wavelengths ranging from a few microns to a few centimeters. The advantages of this system for use as a power source for future acceleration techniques are its efficiency, tunability and high average power. In order to achieve DC operation of the system extremely high electron recovery efficiencies are required. It is also likely that FEL operation will result in a large spread of electron energies. These design constraints require the development of a highly efficient electron beam collector as well as beam optics capable of recirculating beams with a large energy spread. We present collector and beamline designs and include electron optics studies for the full range of operating conditions. |
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