| AVS 62nd International Symposium & Exhibition | |
| Vacuum Technology | Tuesday Sessions |
| Session VT-TuM |
| Session: | Vacuum Suitcases and Particulate Control |
| Presenter: | Paolo Michelato, Italian National Institute for Nuclear Physics (INFN), Italy |
| Correspondent: | Click to Email |
High quantum efficiency semiconductor photocathodes, as alkali telluride and antimonides, are used as high brightness electron sources in laser triggered radio frequency and high voltage guns. These materials are quite sensitive to gas contamination and UHV conditions must be guaranteed during preparation, storage and handling. Their photo emissive characteristics, as the quantum efficiency, are strongly affected by the exposition to reactive gases as oxygen, carbon dioxide and water vapor.
Photocathodes are commonly prepared and fully characterized in the preparation laboratory and then moved to the point of use, usually inside the tunnel of the accelerator facility. Different laboratories built custom designed UHV suitcases, which will be described and analyzed in this paper, for the transportation and manipulation of these sensitive materials.
INFN Milano – LASA produces, handles and transports Cesium Telluride photocathodes to different laboratories since 1990. Our suitcases are successfully used for transferring photocathode between production sites (INFN Milano, DESY-HH, Fermilab) to the accelerator facilities at DESY Hamburg (FLASH, XFEL), DESY Zeuthen, FERMILAB and LBNL. Up to now, seven suitcases transfer photocathodes between laboratories for preparation procedure, use in the gun, diagnostic and post-mortem investigation.
The transportation of other critical and delicate components might benefit from a similar suitcase design.
Generally, a sputter ion pump maintains the photocathodes in UHV during their transfer. This type of pump is heavy, and needs a HV power supply for continuous operation. These characteristics pose serious limitations for cathode air freight transportation due to present safety regulation. To overcome these limitations, we adopt a different strategy coupling a NEG pump with sputter ion pump. With this approach the NEG pump can preserve photocathode characteristics for a long time, even with the sputter ion pump switched off.
At present, we are testing a SAES Getters NEXTorr® pump that combines, in a synergic design, sintered NEG and sputter ion pump technologies. This would provide a more compact and lightweight system, with less residual magnetic fringe field, and an integrated pressure reading. The paper will discuss the results so far obtained, in terms of suitcase performances and reliability as well as photocathode properties preservation.