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Hydrogen-Selective Pumping Performance of a Non-Evaporable Getter Pump Installed in QUEST

Gen MOTOJIMA^1,2), Yuya OTSUKA³⁾, Kazuaki HANADA⁴⁾, Takahiro NAGATA⁴⁾, Makoto HASEGAWA⁴⁾, Hiroshi IDEI⁴⁾, Takeshi IDO⁴⁾, Ryuya IKEZOE⁴⁾, Toshiki KINOSHITA⁴⁾, Yoshihiko NAGASHIMA⁴⁾, Takumi ONCHI⁴⁾

1)

National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan

2)

The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan

3)

Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580, Japan

4)

Research Institute for Applied Mechanics, Kyushu University, 6-1 Kasuga-kouen, Kasuga, Fukuoka 816-8580, Japan

(Received 13 March 2026 / Accepted 12 April 2026 / Published 18 June 2026)

Abstract

A non-evaporable getter (NEG) pump was experimentally installed in the QUEST spherical tokamak to enhance particle exhaust capability during long-pulse, high wall temperature operation (473 K). Activation and pumping performance tests were conducted using hydrogen gas injection and quadrupole mass spectrometry. During activation at 773 K, hydrogen desorption was clearly observed, whereas impurity species (mass number 18, 28, 32, 44) desorption remained strongly suppressed. Pumping tests at 473 K demonstrated hydrogen-selective exhaust with an effective pumping speed of approximately 150 L/s. These results demonstrate that NEG pumps can provide a controllable and impurity-compatible particle exhaust method in fusion-relevant environments. In particular, the suppression of impurity release during activation suggests the possibility of in situ regeneration without significant degradation of plasma conditions due to impurity contamination, enabling continuous operation without isolation. This operational flexibility highlights the potential of NEG pumps as assist tools for particle control in steady-state plasma operation.

Copyright (c) 2026 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

non-evaporable getter pump, NEG, activation, hydrogen-selective pumping

DOI: 10.1585/pfr.21.1202033

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References

• [1] M. Hasegawa et al., Plasma Fusion Res. 16, 2402034 (2021).
• [2] E. Sartori et al., J. Vac. Sci. Technol. B 41, 034202 (2023).
• [3] G. Motojima et al., Fusion Eng. Des. 143, 226 (2019).
• [4] https://www.saesgetters.com/highvacuum/solution/modules-hv/.