Studies in laser photo-cathode RF guns.

摘要

The emittance compensation mechanics of a "non-magnetized" (the magnetic field on cathode is zero) beam in a compact RF gun with a solenoid, a drift space and a booster linac system is presented. The chromaticity effect is included. The recipe of designing and optimizing the system is given.; A "magnetized" (the magnetic field on cathode is not zero) beam is used for some particular applications such as electron cooling of the ion beams. The emittance compensation of a magnetized beam is studied.; For the RHIC electron-cooling project, the charge per bunch (20nC) and the magnetization (380mm.mr) are very high. Following the rules of designing and optimizing the system, the beam dynamics of the RHIC e-cooling injector is simulated using PARMELA code. With the requirement of merging the low energy beam with the high energy beam, the transverse emittance epsilon M is as small as 35mm.mr, while the longitudinal emittance is as small as 100deg.keV. These results fulfill the RHIC e-cooling requirements.; The mechanism, physical properties and the electron beam qualities of the secondary emission enhanced photoinjector (SEEP) are presented. The studies indicate that the SEEP can generate high quality electron beam with many advantages: (1) Reduction of the number of primary electrons by the large SEY, i.e. a very low laser power requirement in the photocathode producing the primaries. (2) Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. (3) Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. (4) Production of high average currents, up to ampere class. (5) Expected long lifetime.; The RF field penetration through a thin metal film is studied and verified experimentally.; We measured the charge carrier (electron or hole) transmission in diamond samples. The experiments of the natural diamond provide a lot of information and most of the data are consistent with theory and previous measurements. With better quality diamond, we expect that the electron transmission through diamond will be appropriate for SEEP.