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

doi:10.1109/IPMHVC.2014.7287246

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

Electrical and Computer Engineering

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

1 Scopus citations

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 language	English
Title of host publication	Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014
Editors	Allen L. Garner
Publisher	Institute of Electrical and Electronics Engineers Inc.
Pages	213-216
Number of pages	4
ISBN (Electronic)	9781467373234
DOIs	https://doi.org/10.1109/IPMHVC.2014.7287246
State	Published - Oct 1 2015
Event	IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014 - Santa Fe, United States Duration: Jun 1 2014 → Jun 5 2014

Publication series

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

Conference

Conference	IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014
Country/Territory	United States
City	Santa Fe
Period	06/1/14 → 06/5/14

Keywords

Gettering
High power microwave generation
Vacuum systems
cathodes

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10.1109/IPMHVC.2014.7287246

Cite this

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

Kelly, Patrick M. ; Parson, J. M. ; Lynn, C. et al. / Performance of St707 getter material in a rep-rated high power microwave sealed-tube vircator under UHV conditions. Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014. editor / Allen L. Garner. Institute of Electrical and Electronics Engineers Inc., 2015. pp. 213-216 (Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014).

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

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.",

keywords = "Gettering, High power microwave generation, Vacuum systems, cathodes",

author = "Kelly, {Patrick M.} and Parson, {J. M.} and C. Lynn and M. Taylor and Dickens, {J. C.} and A. Neuber and J. Mankowski and S. Calico and M. Scott",

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Kelly, PM, Parson, JM, Lynn, C, Taylor, M, Dickens, JC , 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 AL Garner (ed.), Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014., 7287246, Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014, Institute of Electrical and Electronics Engineers Inc., pp. 213-216, IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014, Santa Fe, United States, 06/1/14. https://doi.org/10.1109/IPMHVC.2014.7287246

Performance of St707 getter material in a rep-rated high power microwave sealed-tube vircator under UHV conditions. / Kelly, Patrick M.; Parson, J. M.; Lynn, C. et al.

Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014. ed. / Allen L. Garner. Institute of Electrical and Electronics Engineers Inc., 2015. p. 213-216 7287246 (Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014).

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution › peer-review

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AU - Kelly, Patrick M.

AU - Parson, J. M.

AU - Lynn, C.

AU - Taylor, M.

AU - Dickens, J. C.

AU - Neuber, A.

AU - Mankowski, J.

AU - Calico, S.

AU - Scott, M.

PY - 2015/10/1

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N2 - 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.

AB - 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.

KW - Gettering

KW - High power microwave generation

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KW - cathodes

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Kelly PM, Parson JM, Lynn C, Taylor M, Dickens JC , Neuber A et al. Performance of St707 getter material in a rep-rated high power microwave sealed-tube vircator under UHV conditions. In Garner AL, editor, Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014. Institute of Electrical and Electronics Engineers Inc. 2015. p. 213-216. 7287246. (Proceedings of the 2014 IEEE International Power Modulator and High Voltage Conference, IPMHVC 2014). doi: 10.1109/IPMHVC.2014.7287246

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

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