Multi-pixel Gamma-Ray Transition-Edge Sensor Covering Wide Energy Range

Nov. 29 17:00-17:25

*Takahiro Kikuchi1, Go Fujii1, Ryota Hayakawa1,2, Ryan Smith3, Fuminori Hirayama1, Yasushi Sato1, Satoshi Kohjiro1, Masahiro Ukibe1, Ohno Masashi3, Akira Sato1, Hirotake Yamamori1, Takumi Hamaguchi4, Takashi Yasumune4, Chikara Ito4, Koji Takasaki4
National Institute of Advanced Industrial Science and Technology (Japan)1
Tokyo Metropolitan University (Japan)2
University of Tokyo (Japan)3
Japan Atomic Energy Agency (Japan)4

Gamma-ray spectroscopy is suitable for non-destructive analysis of nuclear materials important for nuclear fuel cycles and global security. Transition-edge sensors (TESs) exhibit typically 10 times higher energy resolution (ΔE) than that of popular High Purity Germanium (HPGe) detectors. In low-energy range (20 keV< E < 220 keV), TESs with 236 pixels show 40 eV< ΔE < 60 eV suitable for measuring isotopic composition of nuclear materials [1,2]. On the other hand, there is a demand in high-energy range (E > 220 keV), such as detection of cesium (137Cs) or positron-annihilation spectroscopy [3,4]. However, to our knowledge, there are no reports on multi-pixel TESs operating in this energy range.

 We have been developing multi-pixel TESs applicable for both energy range. A unique improvement in our fabrication is a 7-μm thick SiO2/SixNy/SiO2 membrane [5] with the same thermal conductance (≈1.5 nW/K) as conventional 1-μm thick silicon-nitride (SixNy) membranes [1,6]. We expect that this thick membrane is more robust to support the heavier-metal absorber required for stopping higher energy photons and converts them into heat. In the low-energy range, a TES with a 0.5-mm-cubic Sn absorber shows 40 eV < ΔE < 47 eV at 86.5 keV for 4 pixels read out by our microwave SQUID multiplexer (MW-Mux) [7, 8]. It clearly separates two lines of neptunium (237Np) at 86.5 keV and protoactinium (233Pa) at 86.6 keV that HPGe cannot distinguish [9]. Moreover, their peak ratio agrees with the expectation based on the radio-active equilibrium between the two nuclides. In the high-energy range, another TES with a 0.8-mm-cubic Sn absorber shows 182 eV < ΔE < 290 eV at 320 keV for 6 pixels. Their ΔE are expected to be high enough for applications introduced above. These results are a milestone for gamma-ray spectrometers equipped with the large number of pixels. We will realize it, incorporating several TES and MW-Mux chips in the same measurement module [10].

[1] D. A. Bennet et al., Rev. Sci. Instrum, 83, 093113, 2012
[2] J. A. Ullom et al., Supercond. Sci. Technol. 28, 084003, 2015
[3] M. Ohno et al., IEICE Trans. Electron., 100, 283, 2017
[4] S. W. Leman et al., J. Low Temp. Phys., 151, 784, 2008
[5] T. Kikuchi et al., Appl. Phys. Lett., 119, 222602, 2021
[6] H. F. C. Hoevers et al., Appl. Phys. Lett., 86, 251903, 2005
[7] Y. Nakashima et al., IEEE Trans. Appl. Supercond. 29, 2100705, 2019
[8] Y. Nakashima et al., Appl. Phys. Lett., 117, 122601, 2020
[9] T. Kikuchi et al., J. Low Temp. Phys., Accepted.
[10] J. A. B. Mates et al., Appl. Phys. Lett., 111, 062601, 2017

Keywords: Transition Edge Sensor, Gamma ray, Trilayer Membrane, Spectroscopy