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.
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.
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.
Improvements to the Advanced Photon Source injector linac have been made to allow for the production and characterization of high-brightness beams in support of fourth-generation light source research. In particular, effort has been directed at generating beams suitable for use in the low-energy undulator test line (LEUTL) free-electron laser (FEL). We describe the enhancements to the linac operational and diagnostic capabilities that enabled self-amplified spontaneous emission (SASE) operation of the FEL at 530 nm. Electron beam measurement techniques and recent results will be discussed. Beam properties are measured under the same operational conditions as those used for FEL studies. The nominal FEL beam parameters are as follows: 217 MeV beam energy; less than 0.15 mm-mrad normalized emittance; 100 A peak current from a 0.7-nC charge at a 7-psec bunch.
We present a two stage Inverse Free Electron Laser accelerator proposed for construction at the UCLA Neptune Lab. Proof-of-principle experiments on the IFEL scheme have been carried out succesfully. This experiment is intended to achieve a 100 Mev energy gain, staging two IFEL modules. It will use the 16 Mev electron beam produced by the Neptune linac, the 1 TW MARS CO2 laser and two different tapered undulators. The problem of refocusing both laser and electron beam is analyzed in detail. A preliminary beamline layout and numerical simulations are presented.
We discuss the possibility of producing an electromagnetic field on the order of the Schwinger critical field by focusing the X-ray beam produced by the X-ray free-electron laser, LCLS, under development by a SLAC-ANL-BNL-LANL-UCLA collaboration. We also discuss an experiment which would use this very large field to test QED through the production of electron-positron pairs in vacuum, with no real particles being present in the initial state.
An X-ray free-electron laser, named the Linear Coherent Light Source (LCLS), will be built at SLAC using the SLAC linear accelerator. LCLS is being developed by a SLAC-ANL-BNL-LANL-UCLA collaboration. The LCLS will produce coherent radiation at 1.5 to 0.15 nm, with peak power as high as 10 GW in a 100fs pulse length, and a line width of about 0.01possibilities now being studied to manipulate the X-ray pulse to control the peak power between 1 and 10 GW, the line-width between 0.01between 100 and 10 fs.
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