Plasma and Fusion Research

Volume 19, 1405015 (2024)

Regular Articles

Estimation and Measurement of Alpha Decay Pulses in Fission Detectors and Their Practical Application for Verifying Detector Health
Shigehiro KONO, Masao ISHIKAWA, Shuhei SUMIDA, Michinori YAMAUCHI1), Daijiro ITO2), Hiroyuki YAZAWA2), Masashi KUROSAKI2), Takashi KOBUCHI3), Kunihiro OGAWA3,4), Mitsutaka ISOBE3,4) and Yoshihiko NUNOYA
Naka Fusion Institute, National Institutes for Quantum Science and Technology, Naka 311-0193, Japan
1)
NAT Corporation, Tokai 319-1112, Japan
2)
Toshiba Energy Systems & Solutions Corporation, Fuchu 183-8511, Japan
3)
National Institute for Fusion Science, National Institutes of Natural Sciences, Toki 509-5292, Japan
4)
The Graduate University for Advanced Studies, SOKENDAI, Toki 509-5292, Japan
(Received 6 November 2023 / Accepted 30 January 2024 / Published 20 March 2024)

Abstract

Signals generated by spontaneous alpha decay of uranium in fission chambers are very small and are buried in background noise. These signals are often simply discriminated by amplitude as unwanted background noise. However, if these signals can be distinguished from white noise, they could function as a checking source that is electric-noise-free and is embedded in the detector itself. To confirm our hypothesis, we estimated and measured the pulse height of alpha decay signals in the fission chambers of the Large Helical Device (LHD) at the National Institute for Fusion Science (NIFS). When background noise was sufficiently low, the plateau curves of alpha decay signals could be measured by using the maintenance function of the neutron monitoring system. When background noise was high, instruments such as an oscilloscope and a multi-channel analyzer (MCA) successfully caught alpha decay signals by using their high-performance trigger functions. Measuring alpha decay pulses is also an indicator of the health of the detector and its preamplifier because if something were wrong with either component, the alpha decay signals would prove difficult to measure. This practical application of alpha decay signals to verify neutron instrumentation systems that use the noise-sensitive Campbelling method will be beneficial for fusion facilities and fission reactors and help meet ALARA policy because this method does not require an external checking source.

Keywords

alpha decay, fission chamber, Campbelling, neutron instrumentation, fission reactor, LHD, ITER, JT-60SA, BWR

DOI: 10.1585/pfr.19.1405015

Full Text

PDF format (1.9Mbytes) PDF Download

References

  • [1] M. Ishikawa et al., Fusion Eng. Des. 109-111, Part B, 1399 (2016).
  • [2] G.F. Knoll, Radiation Detection and Measurement, 4th ed., (Wiley, New York, 2010), p.134, p.538.
  • [3] M. Isobe et al., Rev. Sci. Instrum. 85, 11E114 (2014).
  • [4] M. Isobe et al., IEEE Trans. Nucl. Sci. 46, No.6, 2050 (2018).
  • [5] D. Ito et al., Plasma Fusion Res. 16, 1405018 (2021).
  • [6] J. Kinoshita et al., PNC-TJ201 73-02 (1973) [in Japanese].
  • [7] N. Wakayama, JAERI-M 85-193 (1985) [in Japanese].
  • [8] Radioisotope Pocket Data Book, 12th ed., JRIA, (Maruzen, Tokyo, 2020) [in Japanese].
  • [9] J.M. Alexander and M.F. Gazdik, Phys. Rev. 120, 874 (1960).
  • [10] Average Energy Required to Produce an Ion Pair, ICRU Report 31, (ICRU, Washington, DC, 1979).
  • [11] P. Filliatre et al., Nucl. Instrum. Methods Phys. A 817, 1 (2016).
  • [12] N. Wakayama et al., JAERI-12697 (1967) [in Japanese].
  • [13] H.A. Bethe, USAEC Doc. BNL-T-7 (1949).