Performance of St707 getter material in a rep-rated high power microwave sealed-tube vircator under UHV conditions

Patrick M. Kelly, J. M. Parson, C. Lynn, M. Taylor, J. C. Dickens, A. Neuber, J. Mankowski, S. Calico, M. Scott

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

This study focuses on the use of St707 non-evaporable getter (NEG) material in a high power microwave (HPM) sealed-tube virtual cathode oscillator (vircator) operated at repetition rates up to 200 Hz. High-current pulsed operation releases gases trapped within the bulk materials and gas monolayers on material surfaces, leading to localized plasma production between the A-K gap. This potentially leads to gap closure, shortens the duration of microwave production, and spoils low vacuum levels. A single current pulse may increase the chamber pressure to the low 10-6 Torr range from an initial background pressure in the low 10-9 Torr range, desorbing approximately 1014 particles. For single pulse operation, it is sufficient to maintain this background pressure (10-9 Torr) with a small ion pump rated at 20 L/s. However, at 200 Hz operation, a pumping speed of 1,000 L/s is needed to evacuate 1014 particles from the vircator volume between pulses. Rather than adding a bulky pump system with the required high pump speed, St707 getter material (70% Zr, 24.6% V, 5.4% Fe) has been used to maintain ultra-high vacuum (UHV) conditions during rep-rate operation. Characteristics of the St707 NEG pump in a repetitive, high-current pulse environment are presented. Diagnostic results obtained with an inverted magnetron cold cathode gauge for absolute pressure are utilized to analyze NEG performance in detail.

Original languageEnglish
Title of host publicationProceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014
EditorsAllen L. Garner
PublisherInstitute of Electrical and Electronics Engineers Inc.
Pages213-216
Number of pages4
ISBN (Electronic)9781467373234
DOIs
StatePublished - Oct 1 2015
EventIEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 - Santa Fe, United States
Duration: Jun 1 2014Jun 5 2014

Publication series

NameProceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014

Conference

ConferenceIEEE International Power Modulator and High Voltage Conference, IPMHVC 2014
CountryUnited States
CitySanta Fe
Period06/1/1406/5/14

Keywords

  • Gettering
  • High power microwave generation
  • Vacuum systems
  • cathodes

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    Kelly, P. M., Parson, J. M., Lynn, C., Taylor, M., Dickens, J. C., Neuber, A., Mankowski, J., Calico, S., & Scott, M. (2015). Performance of St707 getter material in a rep-rated high power microwave sealed-tube vircator under UHV conditions. In A. L. Garner (Ed.), Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 (pp. 213-216). [7287246] (Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/IPMHVC.2014.7287246