JAEA photocathode DC-gun for an ERL injector

Nishitani, Tomohiro; Hajima, Ryoichi; Iijima, Hokuto; Nagai, Ryoji; Sawamura, Masaru; Kikuzawa, Nobuhiro ; Nishimori, Nobuyuki; Minehara, Eisuke; Tabuchi, Masao*; Noritake, Yosuke*; Hayashitani, Haruhiko*; Takeda, Yoshikazu*

ERL light source and FEL require an electron beam of large current and small emittance. In order to realize an electron gun satisfying such requirements,we started developments of a photocathode DC-gun and a new-type NEA-photocathode. The DC-gun consists of a chamber to activate NEA-surface, a 250 keV acceleration chamber, and a mode-locked Ti:Sapphire laser. Since extreme high vacuum is essential to obtain a long-life photocathode, we adopt a load-lock system for transporting a photocathode between the chambers, each of which is equipped with an NEG pump. Up to now, we fabricated an electrodes chamber and a high voltage terminal of 250 kV and we succeeded in a 250kV high voltage test. We also have suggested a superlattice photocathode as a new-type photocathode with higher performance than an existing technology. Up to now, we fabricated photocathode samples by molecular beam epitaxy and measured a quantum efficiency after NEA-surface activation.