The CLASSE Seminar presents Dr. Russell Mammei of Jefferson Lab who will be discussing:

Title: Performance of a Bialkali Photocathode Inside the JLab DC High Voltage
Inverted Gun

ABSTRACT: Two photocathodes are frequently considered for generating high average current electron beams and/or beams with high brightness: GaAs:Cs and K_2CsSb. Each photocathode has advantages and disadvantages, although some attributes are based on assumptions and not demonstrated performance at “production” accelerator facilities. To make a well-informed choice for new accelerators applications, the performance of both photocathodes should be measured under identical conditions. To this end Brookhaven National Lab (BNL) and Jefferson Lab (JLab) groups have been collaborating to study the characteristics of K_2CsSb photocathodes in the same DC field that has been used to study GaAs:Cs. In March of 2011, a K_2CsSb photocathode was grown at BNL and successfully transported in vacuum to the Injector Test Stand electron gun at JLab where charge lifetime was evaluated with 440 and 532 nm wavelengths at 100 and 200 kV gun bias voltages while generating dc currents ranging from 1-20 mA. In total ~5000 C of charge has been extracted during these measurements. After beam evaluation, the photocathode was also studied with an SEM/EDS system.