First Name: S
Middle Name:
Last Name: Hartman
Full Name: S. C. Hartman
tags:
Potential Duplicate Authors:
view citation format
11 papers
| title: | Experimental demonstration of dynamic focusing of a relativistic electron bunch by an overdense plasma lens |
| format: | unknown |
| year: | 1994 |
| 7 authors: | | | | | | | |
| abstract: | Dynamic focusing of a 3.8 MeV electron bunch, a few collisionless skin depths long approximately 3c/ omega /sub p/, by an overdense, thick plasma lens has been demonstrated. Because of electron inertial effects, the head of the bunch is virtually unaffected by the lens while the rest is focused to varying degree. Time-resolved measurements performed 31 cm downstream of the plasma lens show that, in time, the bunch pinches from an initial size of 2.7 mm (FWHM) to about 0.57 mm and then expands, in reasonable agreement with theory. (20 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Initial measurements of the UCLA RF photoinjector |
| format: | conference procceeding |
| conference: | Conference on High Intensity Electron Sources |
| year: | 1994 |
| 14 authors: | | | | | | | | | | | | | | |
| abstract: | The 1.5 cell standing wave RF photoinjector has been operated for the past several months using a copper cathode. The photoinjector drive laser produces sub 2 ps pulses of UV ( lambda =256 nm) light with up to 200 mu J/pulse which generates up to 3 nC of charge, The emittance of the photoinjector was measured as a function of charge, RF launching phase, and peak accelerating field. Also, the quantum efficiency and pulse lengths of the laser beam and the electron beam were measured. (15 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Ponderomotive focusing in axisymmetric RF linacs |
| format: | unknown |
| year: | 1993 |
| 2 authors: | | |
| abstract: | In many present and planned compact electron sources and linacs, very large rf accelerating fields are present in the linac structures. A charged particle whose trajectory is parallel to the axis receives no net focusing from the periodic transverse forces arising from the axisymmetric rf wave. However, if the lowest-order periodic transverse motion of the particles is included, a net ponderomotive focusing force is obtained when the momentum transfer is averaged over a period of the motion. Since this force is second order in the electric-field amplitude, the resultant focusing can be non-negligible in high gradient structures. In order to produce and preserve high-brightness beams in rf linacs it is necessary to obtain a better understanding of all the forces acting on the beam and the subsequent beam dynamics. To this end we examine the lowest-order ponderomotive rf focusing of electrons in axisymmetric standing- and traveling-wave linac structures. We obtain a generalized paraxial envelope equation which includes the effects of the ponderomotive focusing and longitudinal acceleration to describe the transverse beam envelope evolution. The implications of our results on beam dynamics in electron linacs are examined, and extensions of the results to positron and proton linacs are discussed. |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Initial operation and beam characteristics of the UCLA S-band RF photo-injector |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 10 authors: | | | | | | | | | | |
| abstract: | The UCLA RF photo-injector system has been commissioned. All of the sub-components such as the high power RF, pico-second laser, RF photo-injector cavity, diagnostics, and supporting hardware have been tested and are operational. We briefly discuss the performance of the various components since the details of each subsystem are very lengthy. The laser delivers a sub 4 ps pulse containing 0-300 mu J of energy per pulse. The photo-injector produces 0-3 nC per bunch with an RF induced emittance of 1.5 pi (mm-mrad). (5 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Emittance measurements of the 4.5 MeV UCLA RF photoinjector |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 10 authors: | | | | | | | | | | |
| abstract: | The 1.5 cell RF photoinjector has been operated for the past several months using a copper cathode illuminated by 4 ps long pulses of UV (246 nm light, with a variable energy of between 0 to 300 mu J. This typically produces up to 3 nC of charge per bunch. Because space charge forces dominate the electron beam transport a pepper pot measurement system is used to measure the emittance. The emittance is measured as a function of charge, peak accelerating field, laser spot size and initial phase with respect to the RF field. This is accomplished with an automated control and data acquisition system which can measure single shot emittances at a rate of 5 Hz developed at UCLA. The experimental results obtained are then compared with theory and simulations. (4 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | The UCLA infrared free-electron laser |
| format: | conference procceeding |
| conference: | SPIE Conference on Intense Laser Beams |
| year: | 1992 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | A compact 20 MeV linac with an RF laser-driven electron gun will drive a high-gain (10 cm gain length), 10.6 mu m wavelength FEL amplifier, operating in the SASE mode. FEL physics in the high-gain regime will be studied, including start-up from noise, optical guiding, sidebands, saturation, and superradiance, with emphasis on the effects important for future short wavelength operation of FELs. The hybrid undulator, designed and built at the Kurchatov Institute of Atomic Energy in the USSR has forty periods, each 1.5 cm long, the magnetic material is a hybrid combination of SmCo_5 blocks and Nd-Fe-B blocks, with vanadium-permendur yokes. The gap distance between pole-tips is fixed at 5 mm. On axis the peak value of the completed undulator's magnetic field was measured to be 7.3 kGauss (+/- 0.25%). Measurements during the conditioning phase of the RF gun for the electron beam's peak dark-current show 6 mA without the longitudinal magnetic focusing field in the gun and 34 mA with the focusing field active. The peak current from photoemission is calculated to be 200 A. |
| keywords: | |
| Details | edit | delete | |
| title: | Design and operation of a novel, compact 20 MeV linac at UCLA |
| format: | conference procceeding |
| conference: | Intense Microwave and Particle Beams II |
| year: | 1992 |
| 9 authors: | | | | | | | | | |
| abstract: | A novel, compact S-band linac has been designed and is currently under construction at UCLA. It is expected to deliver high brightness, 200 A, 20 MeV electron pulses, less than 4 ps in duration from a device that is about 1 meter long. It comprises: (a) a laser photocathode driven gun that produces 4.5 MeV electron bunches from a 1/sup 1///sub 2/ cell cavity operating in the pi -mode and (b) an accelerating structure known as a plane wave transformer (PWT) designed by Swenson (1988). The design considerations of the machine and initial operating experience of the gun are discussed. The linac will be used for free electron laser, advanced accelerator research and beam-plasma experiments. (8 References). |
| keywords: | |
| Details | edit | delete | |
| title: | The UCLA compact infrared free-electron laser |
| format: | conference procceeding |
| conference: | 13th International Free Electron Laser Conference |
| year: | 1992 |
| 16 authors: | | | | | | | | | | | | | | | | |
| abstract: | The authors present the status of a compact infrared free-electron laser, driven by a 20 MeV, S-band linac with a photoinjector. The 60 cm long hybrid undulator has a 1.5 cm period and a field on axis of 7.3 kG. The FEL will operate at 10.6 mu m as a high-gain amplifier, to study the high-gain FEL regime including the effects of self amplified spontaneous emission, optical guiding and saturation. The linac is the prototype of the plane-wave transformer. TDA simulation of the FEL shows a gain length of 10 cm, and a saturation power of 50 MW. (18 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Saturnus: the UCLA infrared free-electron laser project |
| format: | conference procceeding |
| conference: | 1991 Particle Accelerator Conference |
| year: | 1991 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | A compact 20-MeV linac with an RF laser-driven electron gun will be used to drive a high-gain (10-cm gain length), 10.6- mu m wavelength FEL (free-electron laser) amplifier, operating in the SASE mode. Saturnus will mainly be used to study FEL physics in the high-gain regime, including start-up from noise, optical guiding, sidebands, saturation, and superradiance, with emphasis on the effects important for future short-wavelength operation of FELs. The primary magnetic flux is provided by C-shaped iron yokes, where between the poles thin blocks of neodymium-iron-boron magnets are placed to provide additional magnetic flux along the undulator axis. (9 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Saturnus: the UCLA compact infrared free-electron laser project |
| format: | conference procceeding |
| conference: | Intense Microwave and Particle Beams II |
| year: | 1991 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | Saturnus is an infrared FEL operating in the 10 mu m wavelength region, driven by a compact 20 MeV linac with a photoinjector, under construction at UCLA. The 1.5 cm period, 0.6 T peak field undulator is being built at the Kurchatov IAE. The FEL is designed to operate primarily in the self amplified spontaneous emission mode. The authors plan to study the start-up from noise, optical guiding, saturation, sidebands and superradiance, with emphasis on the effects important for future short wavelength operation of FEL's. The photoinjector follows closely the Brookhaven design. Electrons are injected into an accelerating section based on the plane-wave-transformer design developed by Swenson at SAIC. Simulation of the linac and FEL show a gain length of 10 cm, and a saturation power of 50 MW. (13 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Saturnus: the UCLA high-gain infrared FEL project |
| format: | conference procceeding |
| conference: | 12th International Free Electron Laser Conference |
| year: | 1991 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | The authors present the status of Saturnus: an infrared FEL operating in the 10 mu m wavelength region, driven by a compact 20 MeV linac with a photoinjector, under construction at UCLA. The 1.5 cm period, 0.5 T peak-field undulator is being built at the Kurchatov IAE. The FEL is being designed to operate primarily in the self-amplified spontaneous emission mode. They plan to study the startup from noise, optical guiding, saturation, sidebands and superradiance, with emphasis on the effects important for future short-wavelength operation of FELs. The photoinjector follows closely the Brookhaven design. Electrons are injected into an accelerating section based on the plane-wave transformer design developed by Swenson at SAIC. Simulation of the linac and FEL show a gain length of 10 cm, and saturation power of 50 MW. (10 References). |
| keywords: | |
| Download | View | Details | edit | delete | |