MEIS Studies of Oxygen Plasma Cleaning of Copper for Fast Response Time Photocathodes Used in Accelerator Application

Description

The performance of a fourth generation light source is to a greater extent reliant on the properties of the electron bunches, with the fundamental limit controlled by the photocathode where the electrons are emitted. Normally conducting RF guns often use metal photocathodes, mainly due to their fast response time that allows very short pulses to be generated. However, they typically have very low quantum efficiency (QE) compared to semiconductor alternatives (GaAs or Cs2Te). The drive to use higher QE metals is motivated by the need to minimize the laser power required to generate sufficient bunch charge for the downstream accelerator.
The use of Cu as the metal photocathode of choice is long standing. However, the preparation of an atomically clean surface is thought to be key to achieving a high enough QE to be used in an RF gun. At STFC Daresbury laboratory a preparation procedure has been developed that has allowed a QE of approximately 10-5 to be achieved. This coupled with a high power UV laser system has allowed electron bunches of up to 250 pC to be generated in the Versatile Electron Linear Accelerator (VELA) facility [1]. However, there is very little understanding of how the cleaning procedure leads to the required surface properties for electron emission and hence a detailed study has been initiated.

Period	9 Aug 2016
Event title	8th International Workshop on High-Resolution Depth Profiling
Event type	Conference
Conference number	8
Location	London, Canada, Ontario
Degree of Recognition	International