Undergraduate Research at Jefferson Lab

Electron Gun High Voltage Conditioning Data Analysis

Student: Francisco Valerio Lopez

School: Benemérita Universidad Autónoma de Puebla

Mentored By: Carlos Hernandez-Garcia

Field emission is a process in which a metal surface emits electrons due to the presence of a high electrostatic field and is the primary mechanism limiting maximum achievable bias voltage in direct current (DC) high voltage photoemission electron guns used at the Jefferson Lab. Gas high voltage conditioning eliminates field emission from electrode cathodes used in these guns. Several electrodes of various shapes have been high voltage conditioned over the past few years. In this work, thousands of data points collected for each conditioning run were analyzed to characterize each electrode shape. The results show that the field emission onset voltage is very similar for all three electrode shapes, unlike the cumulative time and maximum conditioning voltage. Three electrode shapes have been analyzed; Tee with no shield electrode at the ceramic-electrode interface, large shield electrode, and small shield electrode. Knowing the behav- ior of high voltage conditioning will serve as a baseline about expected behavior, as a guide in designing future electron guns and for planning the length of time required in their high voltage conditioning phase.

[Watch the presentation on YouTube]