On 16 - 20 January 2012, Tim Noakes and Julian McKenzie attended the USPAS (United States Particle Accelerator School) on Cathode Physics held in Austin, Texas. The course was an opportunity to delve into the theoretical aspects of photoemission from a variety of cathode sources as well as learn about the practical aspects of operating such devices. Tim followed that week with a further course of photoinjector beam dynamics.
Photoinjectors have been a key element in ASTeC's R&D activities since the first operation of the DC high voltage gun with ALICE in 2006. Since then, the photocathode programme has led to the successful development and operation of a dedicated GaAs photocathode preparation facility in the Cockcroft Institute in 2009. This allows photocathodes to be activated to quantum efficiencies as high as 20%, many times the best achieved in the ALICE gun.
Work on GaAs is continuing in collaboration with the Institute of Semiconductor Physics at Novisibirsk, with a high resolution device to measure the energy spread of the emitted electrons at both room and liquid nitrogen temperatures currently under construction. A test beamline to measure the intrinsic emittance and response time of photocathodes is also under development.
Photoinjectors are a critical component of future FEL-based light sources - the EBTF currently under construction at Daresbury Laboratory will contain a suite of diagnostics to accurately characterise RF photoguns, and will be our first experience with copper cathodes. ASTeC's photoinjector design skills have been necessary for completion of the Conceptual Design Reports of both the 4GLS and NLS projects, and have recently led to a collaborative work on the MAX-IV injector in Sweden.