Development of a photocathode RF gun for an L-band electron linac

We conduct research on Free Electron Laser (FEL) in the infrared region and pulse radiolysis for radiation chemistry using the 40 MeV, 1.3 GHz L-band linac of Osaka University. At present, the linac is equipped with a thermionic electron gun. It can accelerate a high-intensity single-bunch beam with charge up to 91 nC but the normalized emittance is large. In order to advance the research, we have begun development of a photocathode RF gun for the L-band linac in collaboration with KEK and Hiroshima University. A new design of the L-band RF gun cavity that improves the cooling system for a long RF pulse operation is being developed and the ultra-precision machining is given to the fabrication of the RF gun cavity. The simulation is also performed for the case of a high charge electron beam. Before we install the new L-band RF gun into the L-band linac of Osaka University, we plan to commission the DESY type of L-band RF gun at the Superconducting RF Test Facility of KEK (KEK-STF). The DESY type of gun is fabricated at the Fermi National Accelerator Laboratory (FNAL), and the resonant frequency and field balance of the RF gun cavity have been adjusted using a tuning apparatus at KEK-STF. In this conference, we describe details of the L-band RF gun development.