II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of novel semiconductor detector towards high-rate heavy
RI beam counting
T. Isobe,∗1 M. Togawa,∗2 M. Miyahara,∗2 J. Nishinaga,∗3 H. Okumura,∗4 M. Imura,∗5 and E. Takada∗6
The precise measurement of heavy ion track and energy loss is important for the identiﬁcation of projectile
fragments with a fragment separator such as BigRIPS atRIBF. As the intensity of the primary beam increases,a stronger radiation-resistant detector is required to realize a high-rate (≥1 MHz) RI beam experiment. A Si
detector has the characteristics of high-resolution energy
measurement, but it is weak in a high-radiation environment. In order to realize a radiation-resistant semiconductor detector, we have examined several types of novel
semiconductors that were developed for other purposes.
Table 1 lists the semiconductors we are testing. The
chalcopyrite compound Cu(In,Ga)Se2 (CIGS) is well investigated as it has potential for use as a semiconductorin thin-ﬁlm photovoltaic devices, such as solar cells.1)
CIGS can recover from radiation damage through the annealing of CIGS crystals. This characteristic is advantageous for a radiation detector since we often encountered
the damage to semiconductor detectors by high-rate ion
beams. GaN is one of the wide-bandgap semiconductorsthat are expected to be suitable for radiation detectors
with long-term stability due to a small intrinsic carrier
density and large threshold displacement energy.
We performed a detector test experiment at HIMAC
in Chiba, where a highly intense 400 MeV/nucleon Xebeam was irradiated on semiconductor samples: CIGSand GaN. Figure 1 shows the sample of the CIGS detector, the thickness and eﬀective area of which are 2 μmand 0.5 mm2 , respectively. This is thick enough to observe the signal with a 400 MeV/nucleon Xe ion, whichloses an energy of 3.5 MeV in the semiconductor. ThisFig. 1. CIGS samples (two pentagons shown at the center ofthe photograph) tested at HIMAC.

beam test was the ﬁrst time a heavy-ion signal was observed from those semiconductors.
In addition to checking the signal from CIGS and GaN,
we tested the hardness of each semiconductor against radiation damage by a Xe beam. Figure 2 shows the CIGS
pulse height as a function of the irradiated Xe beamyield. During the irradiation of a high-rate (106 pps) Xebeam on CIGS, the pulse height decreased down to 60%of the original pulse height. After annealing the CIGS
semiconductor (130◦ C, 5 h), we could observe the recovery of the pulse height to ∼85% of the original pulseheight.

Table 1. Speciﬁcations of modern semiconductor candidates
for radiation detection.
Normalized
Bandgap
Densitynumber of e-henergy
3(g/cm )pairs to Si(eV)
Si
1.1
2.33
1
CIGS
1.2
5.7
2.93
SiC
3.2
3.21
0.64
GaN
3.4
6.15
1.07
Diamond
5.5
3.50
0.45
AlN
6.1
3.26
0.33
∗1
∗2
∗3
∗4
∗5
∗6Fig. 2. CIGS negative pulse height as a function of irradiated
Xe beam yield. A 400 MeV/nucleon 106 pps Xe beam wasirradiated on a CIGS sample. After annealing the CIGS
sample, the recovery of the pulse height was observed asshown by the rightmost point.

RIKEN Nishina Center
Institute of Particle and Nuclear Studies, High Energy Accelerator Research Organization (KEK)
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology (AIST)
Faculty of Pure and Applied Sciences, University of Tsukuba
Research Center for Functional Materials, National Institutefor Materials Science (NIMS)
Quantum Life and Medical Science Directorate, National Institutes for Quantum Science and Technology (QST)

We will continue to develop the next generation ofsemiconductor detectors by employing a novel type ofsemiconductor.
Reference1) J. Nishinaga et al., Appl. Phys. Exp. 10, 092301 (2017).

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