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12 papers
| title: | Initial operation of S-band plane wave transformer photoinjector |
| format: | conference procceeding |
| conference: | APS April Meeting |
| year: | 2000 |
| 4 authors: | | | | |
| abstract: | An integrated S-Band RF photoinjector based on the plane wave transformer (PWT) is being built and operated in the Particle Beam Physics Laboratory at UCLA. This novel structure integrates a photocathode directly into a PWT Linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20MeV, with emittance less than 1mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASE-FEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The initial operation of the PWT photoinjector with high RF power is described. A comparation of experimental result and theoretical design is also discussed. |
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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: | The development of S-band plane wave transformer photoinjector |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 11 authors: | | | | | | | | | | | |
| abstract: | An integrated S-band RF photoinjector based on the plane wave transformer (PWT) is being built in the Particle Beam Physics Laboratory at UCLA in collaboration with DULY Research. This novel structure integrates a photocathode directly into a PWT linac making the structure simple and compact. Due to the strong coupling between each adjacent cell, this structure is relatively easy to fabricate and operate. This photoinjector can provide high brightness beams at energies of 15 to 20 MeV, with emittance less than 1 mm-mrad at charge of 1 nC. These short-pulse beams can be used in various applications: space charge dominated beam physics studies, plasma lenses, plasma accelerators, free-electron laser microbunching techniques, and SASEFEL physics studies. It will also provide commercial opportunities in chemistry, biology and medicine. The present status of the PWT photoinjector including fabrication and cold test to characterise the structure is described. RF system and photocathode drive laser system are also discussed. |
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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 permanent-magnet focused X-band photoinjector |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 8 authors: | | | | | | | | |
| abstract: | A Plane-Wave-Transformer (PWT), integrated photoinjector operating at an X-band frequency (8.547GHz) is being developed by DULY Research Inc. in a DOE SBIR project, in collaboration with UCLA and UCD/ILSA. Upward frequency scaling from an S-band PWT photoinjector would result in a compact photoinjector with unprecedented brightness. Challenging technological innovations are required at X-band. In particular, water cooling capacity, mechanical support strength, and materials properties do not scale linearly with frequency. Instead of using large solenoids, we have successfully designed the required focusing for an X-band PWT using a compact, permanent magnet system. Also described in this paper is a system design of the X-band photoinjector, including the RF system and the cooling/support of the PWT structure. |
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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: | Output power control in an X-ray FEL |
| format: | conference procceeding |
| conference: | 1999 Particle Accelerator Conference |
| year: | 1999 |
| 3 authors: | | | |
| abstract: | Recent theoretical and experimental advances of the high gain self-amplified spontaneous emission free-electron laser (SASE-FEL), have demonstrated the feasibility of using this system as a 4/sup th/ generation light source. This source will produce diffraction-limited radiation in the 0.1 nm region of the spectrum, with peak power of tens of GW, subpicosecond pulse length, and very large brightness. The peak power density in such a system is very large, and in some experiments it might damage the optical systems or the samples, or it might be simply larger than what is needed for the particular experiment being considered. Some options to reduce the power level, for example by using a gas absorption cell to reduce the X-ray intensity, have been studied. In this paper we discuss another possibility to control the power output of an X-ray SASE-FEL by varying the charge from the electron source, and the longitudinal bunch compression during the acceleration in the linac. |
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| title: | Beam dynamics in an integrated plane wave transformer photoinjector at S and X-band |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 6 authors: | | | | | | |
| abstract: | The beam dynamics of an integrated S-band RF photoinjector based on the plane wave transformer (PWT) concept, proposed as part of an SBIR collaboration between UCLA and DULY Research, are studied. The design, which calls for an 11.5 cell structure run at a peak accelerating field of 60 MV/m and uses a compact solenoid around the initial 2.5 cells, is based on a recently developed theory of emittance compensation. It calls for matching the beam onto a generalized equilibrium envelope, which produces a beam which diminishes in transverse size monotonically with acceleration. This condition minimizes the emittance, which is 1 mm-rad at Q=1 nC. This design is also scaled to produce nearly identical performance at X-band, giving an injector appropriate to running an FEL at the SLAC NLCTA. These designs are insensitive to RF emittance increase, allowing a wide choice of injection phase, and the option to compress the emitted pulse. (8 References). |
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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: | A plane-wave-transformer photoelectron linac |
| format: | conference procceeding |
| conference: | 1997 Particle Accelerator Conference |
| year: | 1998 |
| 7 authors: | | | | | | | |
| abstract: | We develop a novel photoelectron linear accelerator using a plane wave transformer (PWT) design. In this design, the input RF power is coupled to the accelerating cavities via a large concentric manifold cavity. The scheme makes possible very strong coupling between the accelerating cells, and relaxes manufacturing tolerances. The compact photoelectron linac integrates a photocathode directly into a PWT linac structure, and eliminates the drift space between a photoinjector and the linac which would otherwise lengthen the electron bunches. Using an emittance compensation scheme, the PWT photoelectron linac produces a high-brightness beam. We have demonstrated by simulations the feasibility of a 20 MeV PWT photoelectron linac design with a set of eleven iris-loaded disks suspended and cooled by four water tubes inside a large cylindrical tank. (5 References). |
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