Automated Activation Procedure for GaAs Photocathodes at Photo-CATCH*

26 Sept 2022, 11:00
20m
HIM

HIM

Helmholtz Institute Mainz Staudingerweg 18 55128 Mainz

Speaker

Dr Maximilian Herbert (TU Darmstadt, Institut für Kernphysik)

Description

Photo-electron sources using GaAs-based photocathodes are used to provide high-brightness and high-current beams of (spin-polarized) electrons for accelerator applications such as free-electron lasers (FELs) and energy recovery linacs (ERLs). Such cathodes require a thin surface layer consisting of Cs and an oxidant in order to achieve negative electron affinity (NEA) for efficient photoemission. The layer is deposited during a so-called activation procedure, whose performance greatly influences the resulting quantum efficiency of the photocathode and robustness of the layer. It is therefore of great interest to optimize and standardize this process in order to provide easily reproducable high-performance GaAs-photocathodes. An automatization of the activation procedure could simplify and accelerate this process, indipendent from expert input, for operational use in an accelerator.
At the Institue for Nuclear Physics at Technische Universität Darmstadt, a dedicated test stand for Photo-Cathode Activation, Test and Cleaning using atomic-Hydrogen (Photo-CATCH) is available for GaAs photocathode research. The components of its activation chamber are remote-controlled using EPICS. This contribution will present recent proof-of-principle studies of a basic automated activation procedure at Photo-CATCH. Using a co-deposition scheme with Cs and O2, several automated activations have been performed. A good reproducibility of quantum efficiency has been observed, with a slight reduction in mean quantum efficiency compared to manual activation.

*Work supported by DFG (GRK 2128 “AccelencE”, project number 264883531) and BMBF (05H18RDRB1)

Category Polarized Sources

Primary author

Dr Maximilian Herbert (TU Darmstadt, Institut für Kernphysik)

Co-authors

Mr Tobias Eggert (TU Darmstadt, Institut für Kernphysik) Prof. Joachim Enders (TU Darmstadt, Institut für Kernphysik) Mr Markus Engart (TU Darmstadt, Institut für Kernphysik) Dr Yuliya Fritzsche (TU Darmstadt, Institut für Kernphysik) Mr Vincent Wende (TU Darmstadt, Institut für Kernphysik)

Presentation materials