Development of Gamma-Ray Position-Sensitive Transition-Edge Sensor Microcalorimeters
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Development of Gamma‑Ray Position‑Sensitive Transition‑Edge Sensor Microcalorimeters N. Iyomoto1 · Y. Kurume1 · T. Kuroiwa1 · S. Asagawa1 · T. Tsuruta1 · Y. Nishida1 · Y. Hamamura1 · K. Maehata1 · T. Hayashi2 · H. Muramatsu2 · K. Mitsuda2 Received: 20 August 2019 / Accepted: 10 August 2020 / Published online: 1 September 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract We are developing position-sensitive transition-edge sensor (TES) microcalorimeters (PoSTs) to detect gamma rays up to a few MeV. Each gamma-ray PoST consists of a long absorber with a TES on each end and works as a 1D imaging spectrometer. We fabricated PoSTs with 0.5 × 0.5 × 18.8 mm lead absorbers. We irradiated two PoST devices with gamma rays from a Cs-137 source. Gamma-ray pulses of the PoSTs show a strong correlation between the pulse height and the rise time. We divided the pulses in the 662 keV line into 12 groups after sorting them by rise time to determine effective pixels. We modeled the PoST device and compared the average pulses of the 12 effective pixels to numerical simulations. The actual pulses and simulated pulses were in good agreement. Keywords Gamma-ray · Transition-edge sensor · Microcalorimeter · Spectroscopy
1 Introduction We are developing transition-edge sensor (TES) microcalorimeters [1] to detect gamma rays up to a few MeV. We propose position-sensitive TES microcalorimeters (PoSTs) [2–4] for such gamma rays. A gamma-ray PoST consists of a long gammaray absorber with a TES on each end. A comparison of the signals between the two TESs determines the position of the gamma-ray interaction; therefore, a PoST works as a 1D imaging spectrometer. Gamma-ray imaging is required in various fields, including medical applications, radioisotope security, and nuclear physics. In the future, we plan to align the 1D PoSTs horizontally and stack these 2D planes to develop a 3D TES array for Compton cameras.
* N. Iyomoto [email protected]‑u.ac.jp 1
Kyushu University, Fukuoka, Japan
2
ISAS/JAXA, Kanagawa, Japan
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Journal of Low Temperature Physics (2020) 200:233–238
PoSTs can also reduce the negative influence of Compton scattering in the silicon substrates of microcalorimeters [5]. This is because the volume of the substrates can be much smaller than the volume of the absorbers in PoSTs.
2 Devices Figure 1 shows a schematic and an image of a PoST. To fabricate mechanically robust detectors with fast responses, titanium/gold TESs were deposited on a thick (9 μm) membrane [5] made of silicon-on-insulator (SOI) wafers. The size of the TESs was 0.5 × 0.5 mm. The superconducting transition temperature of the TESs was 171 mK. The volume of the SOI substrate of each TES chip was 5.0 mm3. To fabricate a PoST, we attached two TES chips to a copper plate using GE varnish. For the gamma-ray absorber, we cut a 0.5 × 0.5 × 18.8 mm piece of lead out of a 0.5-mm-thick sheet and glued the TESs to each end of the absorber using STYCAST 2850-FT epoxy and 20-μm-thick spacers. We fa
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