Challenges of Automating the Photocathode Fabrication Process at CERN

The CERN Photoemission Laboratory was founded in 1989 with the goal of studying laser-driven electron sources, for producing high-brightness electron beams within the framework of the Compact Linear Collider (CLIC) study. To produce these photocathodes, two processes run in parallel. The first process, which is slow and asynchronous, controls and monitors the evaporation of photoemissive material. For this first step several power supplies are controlled to evaporate different metals through the Joule effect, with the power maintained constant in time and the thickness deposited monitored. The second process is synchronized with a laser trigger ranging from 0.1 to 50Hz, where the photocurrent and laser energy are measured to calculate the Quantum Efficiency. The control system for these processes has recently been renovated to benefit from the modularity of a PXI-based real-time environment using the standard CERN MiddleWare communication layer (CMW). This paper describes the challenges of the fabrication process as well as the flexibility introduced by using a PXI system.