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6CCVD Research

High voltage performance of a dc photoemission electron gun with centrifugal barrel-polished electrodes

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2017-09-01
JournalReview of Scientific Instruments
AuthorsC. Hernandez-Garcia, D. Bullard, Fay Hannon, Y. Wang, Matt Poelker
InstitutionsThomas Jefferson National Accelerator Facility
Citations24

Abstract

Section titled ā€œAbstractā€

The design and fabrication of electrodes for direct current (dc) high voltage photoemission electron guns can significantly influence their performance, most notably in terms of maximum achievable bias voltage. Proper electrostatic design of the triple-point junction shield electrode minimizes the risk of electrical breakdown (arcing) along the insulator-cable plug interface, while the electrode shape is designed to maintain <10 MV/m at the desired operating voltage aiming at little or no field emission once conditioned. Typical electrode surface preparation involves diamond-paste polishing by skilled personnel, requiring several weeks of effort per electrode. In this work, we describe a centrifugal barrel-polishing technique commonly used for polishing the interior surface of superconducting radio frequency cavities but implemented here for the first time to polish electrodes for dc high voltage photoguns. The technique reduced polishing time from weeks to hours while providing surface roughness comparable to that obtained with diamond-paste polishing and with unprecedented consistency between different electrode samples. We present electrode design considerations and high voltage conditioning results to 360 kV (āˆ¼11 MV/m), comparing barrel-polished electrode performance to that of diamond-paste polished electrodes. Tests were performed using a dc high voltage photogun with an inverted-geometry ceramic insulator design.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
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  10. 2010 - Design considerations for a high voltage DC photoemission electron gun at Cornell university

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