Status of the Booster Injector for the Duke FEL Storage Ring

This paper presents the current status of the booster synchrotron for the Duke Free Electron Laser Laboratory (DFELL) storage ring. The booster will provide full energy injection into the storage ring in a wide energy range from 0.27 to 1.2 GeV. When operating the DFELL storage ring as the High Intensity Gamma Source (HIGS) to produce gamma photons above 20 MeV with Compton scattering, continuous electron loss occurs. The top-off mode operation of the booster injector will enable the continuous operation of the HIGS facility by replenishing the lost electrons. The design requirement for a compact booster with the single bunch extraction capability remains a challenge for the machine development. Presently, the booster project is in the installation phase. The magnetic elements, vacuum chambers, injection and extraction kickers have been developed in collaboration with and fabricated at the Budker Institute of Nuclear Physics (BINP), Russia. The diagnostic and control system is being developed at DFELL. The commissioning of the booster synchrotron will start at the end of 2005. BOOSTER PARAMETERS The DFELL booster synchrotron is a compact 31.9 m circumference machine with race-track shape as shown if Figure 1. It is designed with the capability of delivering up to 4 nC/sec of electron beam into the storage ring in the top-off mode operation for high flux gamma-ray beam production. The booster parameters are listed in Table 1. The booster uses the existing linac as an injector at a beam energy of 270 MeV. It is designed primarily for single turn injection. The injection scheme is vertical using a horizontal Lamberson type septum magnet with a static magnetic field. With an existing photocathode gun, the linac allows injection of a single bunch with maximum current of 2 mA. A Linac modification is required to provide multi-bunch operation. The extraction energy of the booster can vary from 270 MeV to 1.2 GeV. The booster is optimized for single bunch extraction. The booster and the storage ring are fully synchronized for the extraction (6). The RF frequency of the booster may be tuned independently or be phase-locked to the master oscillator of the main ring. The odd ratio of the harmonic numbers of the booster and