First Name: R.
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Last Name: Zhang
Full Name: R. Zhang
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17 papers
| title: | Study of a novel compact standing wave RF linac |
| format: | unknown |
| year: | 1997 |
| 3 authors: | | | |
| abstract: | A novel, compact RF linac structure, the plane wave transformer (PWT), is studied. The PWT provides high accelerating field and high efficiency, and can be used to accelerate high-brightness beams. PWT linac prototypes with eight cells at S-band have been developed at UCLA and successfully used to accelerate an electron beam by more than 10 MeV in 40 cm. In this paper, we describe the principal properties of this structure, the electric parameters obtained from numerical simulation, and measurement results from microwave cold tests. The mechanical design for prototype linacs is also reported. (13 References). |
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| title: | Generation of sub-picosecond electron bunches from RF photoinjectors |
| format: | unknown |
| year: | 1997 |
| 3 authors: | | | |
| abstract: | In this paper we discuss the possibility to generate sub-picosecond electron bunches directly from a photoinjector by illuminating a photo-cathode in an RF cavity with a phase-locked sub-picosecond laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through a photoinjector. We provide analysis of the beam dynamics, as well as the comparison with numerical simulations. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi-cell RF gun structure based on the PWT linac presently in operation at UCLA. (23 References). |
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| title: | Electron micro-bunch generation from RF photoinjectors |
| format: | conference procceeding |
| conference: | Micro Bunches Workshop |
| year: | 1996 |
| 3 authors: | | | |
| abstract: | In this paper we discuss how the injector specifications of a 2nd-generation plasma beat wave accelerator (PBWA) experiment can be achieved by a photo-injector. Typical required bunch lengths (FWHM) are 50 microns with 15 pC bunch charge. We analyze the possibility of generating such short electron bunches directly from a photoinjector by illuminating a photocathode in an RF electron gun with a phase-locked 160-fs laser pulse. In particular, we address all de-bunching effects taking place during acceleration and transport through the photo-injector. We provide a set of analytical scaling laws, as well as a comparison with detailed simulations of the beam dynamics. The possible performances of the present SATURNUS linac setup are presented, as well as the anticipated capabilities of a multi-cell RF gun structure based on the PWT linac presently in operation at UCLA. (17 References). |
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| title: | An injector-prebuncher for a plasma electron accelerator |
| format: | conference procceeding |
| conference: | 1995 Particle Accelerator Conference |
| year: | 1995 |
| 5 authors: | | | | | |
| abstract: | Optimum operation of a plasma beat-wave or wakefield accelerator requires an injected beam consisting of a train of electron bunches separated by the plasma wavelength, with each bunch in the train having a length much shorter than the plasma wavelength, and the capability of controlling the relative phase of the electron bunches and plasma wave. The typical plasma wavelength is about 0.1 mm, requiring a bunch length of about 10 to 20 mu m, which is difficult to achieve with conventional RF based injectors. In this paper we describe an electron accelerator-buncher system based on a photoinjector and an FEL, which can satisfy the plasma accelerator requirements. (4 References). |
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| 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). |
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| 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). |
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| title: | 25 MeV Injector for the Plasma Beat Wave Accelerator |
| format: | preprint |
| year: | 1994 |
| 5 authors: | | | | | |
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| title: | A millimeter wave FEL driven by a photocathode RF linac |
| format: | conference procceeding |
| conference: | 15th International Free Electron Laser Conference |
| year: | 1994 |
| 11 authors: | | | | | | | | | | | |
| abstract: | We present the design of a millimeter wave FEL based on the UCLA photocathode RF linac. The linac energy can be varied between 5 and 18 MeV. The electron pulse duration is 2 ps FWHM, with a peak current exceeding 150 A. The FEL is designed to operate in the high-gain Compton regime, controlling the slippage with the propagating radiation in a waveguide. The design permits the exploration of the basic FEL physics in this regime, including the exploration of saturation and lethargy in the superradiant and steady state regime. (15 References). |
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| 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). |
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| title: | The plane wave transformer linac development at UCLA |
| format: | conference procceeding |
| conference: | 1993 Particle Accelerator Conference |
| year: | 1993 |
| 3 authors: | | | |
| abstract: | A plane wave transformer linac (PWT), offering advantages of high efficiency, compactness, fabrication simplicity and cost, is being developed at UCLA. The PWT prototype at UCLA is an 8-cell, pi -mode, S-band standing-wave linac. To fully understand its physical properties, numerical modeling of the PWT prototype has been carried out by using the 3-D code MAFIA. A microwave test-stand with a network analyzer has also been set up to test these properties. In this paper. We present the important physical features, such as mode structures, dispersion curves, wake field, from the computation and/or the experiment. The measurements show good agreement with the numerical computation. (7 References). |
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| title: | Memo: RF Power for the PWT LInac |
| format: | preprint |
| year: | 1993 |
| 1 author: | |
| abstract: | The plane-wave transformer (PWT) linac, proposed by Swenson, will be used in the Saturnus, the UCLA high gain infrared FEL project. The FEL's output wavelength is designed to match the 10.6 um radiation which CO2 lasers produce.... |
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| title: | Memo: Tentative Design of the Waveguide FEL at UCLA |
| format: | preprint |
| year: | 1993 |
| 1 author: | |
| abstract: | In order to investigate the slippage effects in FELs, we are going to design a millimeter FEL with the following parameters: .... |
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| title: | BPM Revisit: Summary of the Previous Test Results |
| format: | preprint |
| year: | 1993 |
| 5 authors: | | | | | |
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| 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). |
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| 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). |
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| 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. |
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| 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). |
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