Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

Development of high-resolution hard X-ray detector system by usingtransition-edge sensor for accelator-based experiments
T. Isobe,∗1 H. Kaori,∗2 T. Okumura,∗1 S. Okada,∗1 S. Yamada,∗3 H. Tatsuno,∗3 D. A. Bennett,∗4
J. A. B. Mates,∗4 D. Yang,∗4 D. S. Swetz,∗4 and T. Hashimoto∗5 for the HEATES collaboration
A transition-edge sensor (TES) is a type of lowtemperature microcalorimeter that provides a muchbetter energy resolution than semiconductor detectors by using a superconducting material as thetemperature sensor at the superconducting-to-normaltransition-edge. Recently, a detector system with TES
was employed for accelator-based experiments.1) For
instance, a high-resolution X-ray measurement of a
Kaonic atom was succesfully performed at J-PARC in
spring 2018.2) An energy resolution of 5.7 eV in FWHM
was shown for the Co Kα X-ray line (6.9257 keV)during the beam time, while a resolution of 5 eV in
FWHM can be achieved for the same line with thebeam oﬀ. As the next step of high-resolution X-ray
spectroscopy with a TES detector system for accelatorbased science, we are constructing a new system byindroducing a modern cryogenic system (HPD Co.
Ltd. model 107 adiabatic demagnetization refrigerator, ADR, cryostat) and novel microwave readout system for TES. The model 107 cryostat has a helium3-backed, single-stage ADR with an ADR base temperature of 30 mK and a 300-h no-load regulation at
100 mK. Figure 1(a) shows the inside of the new cryogenic system.
The sensitivity of the TES is expressed as ∆T =E/C, where ∆T is the temperature change, E the energy of X-rays, and C the heat capacity of the TES.
Thus, the size of the TES, which determines C, is limited for a target performance. Typically, the size of
one pixel is 100 × 100 µm2 . In order to enlarge the acceptance of the detector, it is necessary to increase thenumber of TES pixels (readout channel). However,the number of electric connections to the cryostat islimited to less than ∼100 due to the limitation in cooling power of the cryogenic system. Recently, a novel
readout technique using a microwave resonator was developed.3) By introducing such microwave readout, thenumber of readout channels is expected to be increased
up to ∼1000 per readout connection. Figures 1(b) and(c) show the transmitted power of the prototype resonator, which gives 64 tones, where one tone is used
for one TES pixel readout.
After ﬁnishing the construction of the new detector system, we plan to execute online experimental
projects for the precise measurement of hard X-ray
∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
National Institute of Advanced Industrial Science and Technology (AIST)
Graduate School of Science, Tokyo Metropolitan University
National Institute of Standards and Technology (NIST)
Japan Atomic Energy Agency (JAEA)- 124 -Fig. 1. (a) New cryogenic system to introduce the novel
TES detector. The top plate is used for vacuum sealing.
The other plates are used for shielding thermal radiation of 300 K, 3 K, and 300 mK from top to bottom.
The TES detector is supposed to be mounted on thebottom part indicated by dashed square. (b) Transmitted power of the prototype resonator. Each tone corresponds to one channel (TES pixel). (c) Enlarged viewof the X-axis of (b). (d) Prototype resonator mountedin model 107.

lines from atomic/nuclear excited states. For example,
X-rays from a muonic atom will be measured for thevalidation of quantum electromagnetics. Furthermore,
X-rays from the excited isomeric state of Th-229 are
proposed to be measured. Currently, a molybdenumgold bilayer TES microcalorimeter for X-rays in therange of 20 keV to 45 keV X-rays has been designed,
and its prototype has been tested.
This work is supported by the Japanese MEXT
KAKENHI under grant No. 18H05458 and No.
18H03713.
References

1) S. Okada et al., Prog. Theor. Exp. Phys. 2016, 091D01(2016).
2) T. Hashimoto et al., J. of Low Temp. Phys. 199, 1018
(2020).
3) J. A. B. Mates et al., Appl. Phys. Lett. 92, 023514 (2008).