Photoemission Properties of LaB6 and CeB6 Under Various Temperature and Incident Photon Energy Conditions

IPAC2016, Busan, KoreaPhotoemission properties of LaB₆ and CeB₆ were investigated at various cathode temperatures and different wavelengths of excitation laser to study for application of electron gun, especially for RF injector of infrared FEL facilities. It was found that the LaB₆ had higher photoemission property than CeB₆ at the same cathode temperature. In addition, LaB₆ can emit a measurable photoemission current being irradiated by laser with energy below work function at the cathode temperature higher than 1400 K. With increasing laser energy (over work function), a photoemission dependency on cathode temperature was getting lower. As the result, LaB₆ is revealed to have better properties than CeB₆ since LaB₆ has higher quantum efficiency than CeB₆ at same temperature

Beam Dynamics Investigation for the Compact Seeded THz-FEL Amplifier

CoE on Sustainable Energy System (Thai-Japan), Faculty of Engineering, Rajamangala University of Technology Thanyaburi (RMUTT), ThailandA compact seeded terahertz (THz) free-electron laser (FEL) amplifier is under development at the Institute of Advanced Energy, Kyoto University. The system consists of a 1.6-cell S-band BNL-type photocathode radio frequency (RF) gun, a focusing solenoid magnet, a magnetic bunch compressor, focusing quadrupoles, a short planar undulator and a THz parametric generator for seeding. The accelerator system will generate a high brightness ultra-short electron bunch injected to the short undulator. Since characteristics of the emitted radiation strongly depend on the electron beam properties, the beam dynamics of the system has been investigated. As the result, the system should be operated at the high accelerating voltage of 80 MV/m to avoid the space-charge effect which causes serious bunch lengthening. The laser with the uniform temporal distribution and the injection phase of 12 degree is suitable for the bunch compression in the chicane. This condition provides the electron beam injected to the undulator with the peak current of more than 300 A and the FWHM bunch length of 0.36 ps at the bunch charge of 200 pC

Thermally assisted photoemission effect on CeB

The thermally assisted photoemission (TAPE) effect was investigated for the hexaboride thermionic cathodes (LaB_{6} and CeB_{6}). It was found that the quantum efficiency of these cathodes can be increased by raising the cathode temperature along with the thermionic emission. In addition both materials can emit a measurable photoemission current by being irradiated with a laser having a photon energy below the work function at sufficiently high cathode temperatures. Our measurements indicate that this process is linear. These results show the significance of the TAPE effect. An additional effect of cathode heating is surface cleaning. This effect was detected as the hysteresis of the quantum efficiency which can be observed by heating up and cooling down the cathode. This effect slightly changes the quantum efficiency but not as much as the TAPE effect

Thermally assisted photoemission effect on CeB_{6} and LaB_{6} for application as photocathodes

The thermally assisted photoemission (TAPE) effect was investigated for the hexaboride thermionic cathodes (LaB_{6} and CeB_{6}). It was found that the quantum efficiency of these cathodes can be increased by raising the cathode temperature along with the thermionic emission. In addition both materials can emit a measurable photoemission current by being irradiated with a laser having a photon energy below the work function at sufficiently high cathode temperatures. Our measurements indicate that this process is linear. These results show the significance of the TAPE effect. An additional effect of cathode heating is surface cleaning. This effect was detected as the hysteresis of the quantum efficiency which can be observed by heating up and cooling down the cathode. This effect slightly changes the quantum efficiency but not as much as the TAPE effect