Development of Iridium Cerium Photocathode for the Generation of High-Charge Electron Beam

We developed an iridium cerium cathode material made by new production method for multi-purpose electron source. For multi-purpose electron source, we focused on the Ir5Ce compound which has a high melting point (> 2100 K) and a low work function (2.57 eV). This material has some excellent properties as both a thermionic cathode and a photocathode. For example, Ir5Ce thermionic cathode can generate one-order higher electrical current than a LaB6 cathode at the same temperature. Another advantage is that an Ir5Ce thermionic cathode has a lifetime two orders longer than that of a LaB6 thermionic cathode under the same conditions. Moreover, we discovered that this material has a reasonably high quantum efficiency (2.70 × 10−3 @213nm at 1000°C) and long-lifetime (> LaB6) as a photocathode. Our research shows that Ir5Ce compound is optimum material for a thermionic cathode and photocathode. We focused on this good emission properties under the high temperature and we tried to develop a backside electron beam heating system and demonstrate a laser pre-pulse heating for a high current thermionic gun system or high charge photocathode gun.