First Name: G
Middle Name:
Last Name: Hairapetian
Full Name: G. Hairapetian
tags:
view citation format
22 papers
| title: | Underdense plasma lens experiment at the UCLA Neptune Laboratory |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 10 authors: | | | | | | | | | | |
| abstract: | An underdense plasma-lens experiment is planned at the UCLA Neptune Laboratory. For this experiment, a LaB/sub 6/-based discharge plasma source was developed and tested. Test results of the plasma source show that it can provide satisfactory Ar plasma parameters for underdense plasma lens experiments, i.e., a density in the low 10/sup 12/ cm/sup -3/ range and a thickness of a few cm. In the plasma chamber a YAG slab and a Cherenkov radiator are placed for electron beam diagnostics so that both time-integrated and time-resolved information will be obtained and compared with the MAGIC code (2 and 1/2 dimensional particle-in-cell) simulations. In this paper, the planned experiment including test results of the plasma source, diagnostics and MAGIC simulation results is presented. (5 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Status of UCLA IR FEL |
| format: | preprint |
| year: | 1996 |
| 21 authors: | | | | | | | | | | | | | | | | | | | | | |
| abstract: | |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | The UCLA compact high brightness electron accelerator |
| format: | conference procceeding |
| conference: | 1995 Particle Accelerator Conference |
| year: | 1995 |
| 10 authors: | | | | | | | | | | |
| abstract: | We report the characteristics and performance of the UCLA S-band compact electron accelerator, consisting of a high brightness, 8 cm long, photo-injector with a copper cathode, followed by a 42 cm long plane wave transformer accelerating structure, delivering a beam energy of 10 MeV. The photo-electrons are produced by a 266 nm laser pulse of less than 4 ps in duration. Over time the laser induced electron emission decreases and the emission from the cathode surface becomes structured. Measurements of the quantum efficiency for Cu before and after this degradation are presented along with images of the non uniform electron emission. (8 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Initial operation of the UCLA plane wave transformer (PWT) linac |
| format: | conference procceeding |
| conference: | 1995 Particle Accelerator Conference |
| year: | 1995 |
| 10 authors: | | | | | | | | | | |
| abstract: | We report on the initial operation of a novel compact rf linac-the plane wave transformer (PWT). The PWT is a 42 cm long, 8 cell standing-wave structure, operated at S-band, in a pi -mode. We present the properties of this linac at rf power levels from 4 MW to 8 MW and beam energy from 7 MeV to 10 MeV, measured initially using both dark current and photo-electrons. Some technical issues associated with the operation are discussed. Future improvements of the PWT, using a modified design, are also studied. (6 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Transverse dynamics of a short, relativistic electron bunch in a plasma lens |
| format: | conference procceeding |
| conference: | Annual Meeting of the Division of Plasma Physics of the APS |
| year: | 1995 |
| 6 authors: | | | | | | |
| abstract: | Dynamic focusing of a 3.8 MeV, 25 ps long, full width at half-maximum (FWHM), electron bunch by an overdense (n/sub p/[right angle bracket][right angle bracket]n/sub b/, where n/sub p/ and n/sub b/ are the plasma and bunch densities, respectively) plasma lens has been studied experimentally. The plasma focused the bunch from an initial transverse size of approximately 2.4 mm (FWHM) to about 0.5 mm, 21 cm downstream of the plasma. The sharp rise time (7 ps 10%-90%) of the electron bunch, excites a large-amplitude ([left angle bracket]1 MeV/m) plasma wave (plasma wake field). The peak focusing force of the lens is partly (60%) due to the beam-generated, azimuthal magnetic field and partly (40%) due to the radial component of the electrostatic wake field. (29 References). |
| keywords: | |
| Details | edit | delete | |
| 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: | Focusing of a Relativistic Electron Beam by an Underdense Plasma Lens |
| format: | preprint |
| year: | 1994 |
| 5 authors: | | | | | |
| abstract: | Plasma Lenses produce focusing gradients exceeding those of conventional quadrupole magnets by several orders of magnitude. We have recently observed dynamic focusing by an overdense plasma lens [G. Hairapetian, et al., Phys.Rev.Lett. 72, 2403 (1994)]. Theoretically, an underdense plasma lens could offer several advantages over the overdense lens: ... |
| keywords: | |
| 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: | Experimental demonstration of plasma lens focusing |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 7 authors: | | | | | | | |
| abstract: | The magnetic self-focusing of a relativistic electron beam propagating through a plasma is demonstrated. The plasma which is produced by an RF discharge in a glass tube with no externally applied magnetic field focuses a 3.5 MeV, 25 ps (FWHM) long electron beam from an initial size of 2.5 mm (FWHM) to about 0.5 mm (FWHM) at a focal length of 18 cm. (7 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | BPM Revisit: Summary of the Previous Test Results |
| format: | preprint |
| year: | 1993 |
| 5 authors: | | | | | |
| abstract: | |
| keywords: | |
| Details | edit | delete | |
| title: | Quantum efficiency measurements of a copper photocathode in an RF electron gun |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 8 authors: | | | | | | | | |
| abstract: | A 4.5 MeV photocathode RF gun has been commissioned at UCLA. A photo-injector drive laser produces sub 2 ps pulses of UV ( lambda =266 nm) light with up to 200 mu J/pulse, and illuminates a copper cathode. The photoelectrons are accelerated to an energy of 3.5 MeV within the gun. The electron beam charge is measured as a function of laser energy using an integrating current transformer (ICT). We present measurements of quantum efficiency as a function of laser polarization for injection angles of 2 degrees and 70 degrees with respect to the cathode normal. At 70 degrees incidence a 50% enhancement in quantum efficiency (>10(-4)) is observed for p-polarized light over s-polarized light. (7 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Streak camera measurements of electron bunch length from a copper photocathode in an RF gun |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 8 authors: | | | | | | | | |
| abstract: | Short laser pulses (sub 2 ps) of UV ( lambda =266 nm) light with 200 mu J/pulse are used to produce electrons from a copper cathode in an RF gun. The electron bunch length is measured by streaking the Cerenkov radiation ( lambda =530 nm) from a thin (250 mu m) fused silica etalon. Streaks for both 0 degrees and 70 degrees laser incidence angles with respect to the cathode normal are presented with a temporal resolution of 3.6 ps. The shortest electron bunch length measured was 9 ps. (3 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: | 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: | The UCLA IR FEL project |
| format: | conference procceeding |
| conference: | 14th International Free Electron Laser Conference |
| year: | 1993 |
| 21 authors: | | | | | | | | | | | | | | | | | | | | | |
| abstract: | A 10.6 mu m free electron laser (FEL) operating in the high gain regime is under construction at UCLA. FEL physics significant to future short wavelength operation is emphasized including optical guiding, superradiance, saturation and self-amplified spontaneous emission (SASE). A 5 MeV RF photocathode gun illuminated by a UV laser supplies a high brightness electron beam which is injected into a plane wave transformer (PWT) linac for acceleration to 20 MeV. Recent measurements of the gun emittance as well as quantum efficiency are presented. The undulator is of a modified hybrid design producing approximately 7.5 kG peak field on axis with 5 mm gap spacing and 1.5 cm pole period. Simulation results which include three-dimensional effects are furnished. The present status and future plans of the project are summarized. (16 References). |
| keywords: | |
| Download | View | Details | edit | delete | |
| title: | Photoelectron beams from the UCLA RF gun |
| format: | conference procceeding |
| conference: | 3rd Advanced Accelerator Concepts Workshop |
| year: | 1993 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | A high brightness, low emittance photocathode rf gun is starting operation at UCLA as an injector to a 20 MeV linac. This linac will initially be used to drive FELs, plasma wakefield accelerators, and to test plasma lenses. The gun is a 1 1/2 cell pi-mode standing wave structure running at 2.856 GHz, and has a copper photocathode. In the initial commissioning of the gun, photoelectron beams of up to 2.5 nC at 4.5 MeV have been produced. We report on the current status of the system, experimental data taken with 50 ps UV laser pulses, and plans for the future. |
| 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 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: | Status of RF photoinjector and PWT linac at UCLA |
| format: | conference procceeding |
| conference: | 1992 Linear Accelerator Conference |
| year: | 1992 |
| 12 authors: | | | | | | | | | | | | |
| abstract: | The authors report the present status of RF photoinjector and plane wave transformer (PWT) linac for the production of 20 MeV/c electron beam. The photoinjector is a 1/sup 1///sub 2/ cell pi -mode standing wave structure operating at 2.856 GHz with photoelectrons generated on a copper cathode by 4 ps long laser pulse at 206 nm. Measurements of the beam of photoelectrons are underway at various experimental parameters. The PWT has been tested at low power to investigate its mode structure. An overview of the system, latest data, and future directions are presented. (5 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: | Photocathode driven linac at UCLA for FEL and plasma wakefield acceleration experiments |
| format: | conference procceeding |
| conference: | 1991 Particle Accelerator Conference |
| year: | 1991 |
| 17 authors: | | | | | | | | | | | | | | | | | |
| abstract: | The UCLA compact 20-MeV/c electron linear accelerators is designed to produce a single electron bunch with a peak current of 200 A, an RMS energy spread of 0.2% or less, and a short 1.2-ps RMS pulse duration. The linac is also designed to minimize emittance growth down the beamline so as to obtain emittances on the order of 8 pi mm-mrad in the experimental region. The linac will feed two beamlines, the first will run straight into the undulator for FEL experiments while the second will be used for diagnostics, longitudinal bunch compression and other electron beam experiments. A description is given of the considerations that went into the design of the accelerating structures and the transport to the experimental areas. (8 References). |
| keywords: | |
| Download | View | Details | edit | delete | |