Hirofumi Hanaki

The KEKB injector linac

Abstract An 8-GeV electron/3.5-GeV positron injector for KEKB was completed in 1998 by upgrading the existing 2.5-GeV electron/positron linac. The main goals were to upgrade its accelerating energy from 2.5 to 8 GeV and to increase the positron intensity by about 20 times. This article describes not only the composition and features of the upgraded linac, but also how these goals were achieved, by focusing on an optics design and commissioning issues concerning especially high-intensity single-bunch acceleration to produce positron beams.

Stabilization of the rf system at the SPring-8 linac

Abstract Beam energy variation of the SPring-8 linac was 1% or more at the start of beam commissioning. Depending on fluctuation, beam transmission efficiency from the linac to the booster synchrotron was significantly affected, and beam intensity in the booster synchrotron changed 20–30%. This caused delay of optimization of the various parameters in the booster synchrotron. More problematic, the beam intensities stored in each rf (radio frequency) bucket of the storage ring at SPring-8 were all different from each other. The users utilizing synchrotron radiation requested that the beam intensity in each rf bucket be as uniform as possible. It was thus a pressing necessity to stabilize the beam energy in the linac. Investigation of the cause has clarified that the various apparatuses installed in the linac periodically changed depending on circumstances and utilities such as the air conditioner, cooling water and electric power. After various improvements, beam energy stability in the linac of

Status of R&D efforts toward the ERL-based future light source in Japan

The energy recovery linac is a very promising synchrotron light source in future. We are contemplating to realize a ERL_based next generation light source in Japan, under a collaboration between KEK, JAEA, ISSP, and other SR institutes. To this end, we started R&D efforts on its key technologies, including a low-emittance photocathode gun and superconducting cavities. We also plan to assemble these technologies into a small test ERL, and to demonstrate their operations. We report our R&D status.

Commissioning a cartridge-type photocathode RF gun system at university of Tokyo

We have developed a compact-sized cartridge-type photocathode system, which is able to replace a cathode without breaking the vacuum of RF gun to use a high quantum efficiency photocathode. The system consists of a BNL-GUN-IV RF gun, a cathode tube, a feed through and ultra-high vacuum system. The purpose of implementing the system is to increase beam charge for the applications such as pulse radiolysis experiment. We observed the charge of 9 nC from the Cs2Te cathode. The maximal quantum efficiency of 3.5% at the charge of 4 nC. It was simulated that the quantum efficiency is reduced by the space charge limit, which is caused by reducing electric field of the beam.

Beam tracking simulation for an rf gun apparatus in the SPring-8

A photo cathode rf gun has been studied in the SPring-8 Linac to obtain a lower emittance beam. In order to perform a comparison with the beam characteristics, a beam tracking simulation code for an rf gun test apparatus has also been developed. In this code, the electric and magnetic forces between all particles are calculated. Accordingly, a lot of time is required, but a high accuracy can be expected in the calculations in comparison with other codes like PIC. In this paper, we describe the above rf gun test apparatus in the SPring-8, the simulation code, and present some calculation results such as the emittance of the emitted beam compared with MAFIA’s data.