Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

Development of the gaseous Xe scintillation detector

Fig. 1. Raw signals of the Xe detector monitored by an oscilloscope. The left panel shows the signals when the Xegas pressure is 1 atm, while the right shows that at 4 atm.
One division of the horizontal axis is 100 ns, and that ofthe vertical axis is 50 mV for the left and 200 mV for theright.
∗1
∗2
∗3
∗4
∗5
∗6
∗7

RIKEN Nishina Center
School of Physics and Nuclear Energy Engineering, Beihang
University
CYRIC, Tohoku UniversityCenter for Nuclear Study, University of Tokyo
RCNP, Osaka University
Department of Physics, Toho University
National Institute of Radiological Science

1600

hEntries

99997

Mean x1400

287

Mean y

1078

RMS x

23.04

RMS y

241.2

Integral 5.64e+04
24

1200

16083 56396

3537027 6408

81000
800
600
400
100 150200

250300350

400 450
ToF [ch]Fig. 2. Particle identification plot of the secondary beam.
The x and y axes correspond to the energy loss for 4atm Xe in QDC channels and the time of flight in TDCchannels, respectively.
CountRIBF can provide very intense RI beams, but we cannot fully utilize this ability because of the radiation damages of the existing detectors for particle identification.
We need a new detector with a good radiation hardness
as well as a good energy and/or timing resolution.
For this purpose, we proposed a Xe gas scintillation
detector. Xe gas has a small work function (∼ 20 eV),
its time response for the scintillation process is relatively
fast, and the wavelength of the scintillation photons isapproximately 175 nm.1) The performance of the Xe gas
scintillation for high-energy heavy-ion particles has notbeen fully measured so far.
The detector consists of an Al chamber filled withhigh-pressure (1 ∼ 5 atm) and pure (99.999%) Xe gas,
two 5-mm-thick and 80-mm-ϕ synthetic silica glass windows, and two PMTs (Hamamatsu, R6041-406). Scintillation photons produced in the Xe gas go through thetwo silica glass windows on both sides of the chamberand finally reach the photo-cathode of the PMTs.
To study the performance of this new detector, wecarried out a test experiment at HIMAC in November
2017 (H390). A secondary beam with a mass-to-charge
ratio A/Z of approximately 2.28 at 300 MeV/nucleon
was produced by the fragmentation of a primary 132 Xebeam at 400 MeV/nucleon with a 9-mm-thick Be target.
The cocktail beam (1 k ∼ 100 k particles/spill) was delivered to the Xe detector through the SB2 beam line.2)
In addition to the Xe detector, a 100-µm-thick plastic
scintillator and a 300-µm-thick Si detector were used forreference.
Figure 1 shows the raw signals of the left (yellow) andright (green) PMTs from the Xe detector at 1 and 4 atmin the upper and lower panels, respectively. Two com-Energy loss @ Xe(4atm) [ch]J. Zenihiro,∗1 T. Harada,∗1,∗6 S. Terashima,∗1,∗2 Y. Matsuda,∗1,∗3 S. Ota,∗4 H. Sakaguchi,∗1,∗5 K. Kawata,∗4S. Ishida,∗1,∗3 Y. Kasamatsu,∗1,∗3 and E. Takada∗71800

Entries
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Underflow
Overflow
Integralχ2 / ndf

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Constant
Mean
Sigma

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h29999652.45
1.475
4.518e+04173.884e+04
27.51 / 71656 ± 22.8
52.99 ± 0.00
0.1908 ± 0.0020

800
600
400
20005051

5253545556
ZFig. 3. Atomic number spectrum around 50 deduced fromthe energy-loss information of the Xe detector.

ponents were found in the scintillation process. We also
checked the signals at 2, 3, and 5 atm, which shows thatthe ratio of the slow component decreases as a functionof pressure.
The energy resolutions at 1 and 4 atm for the 132 Xe
primary beam are approximately 1.2% and 0.8%, respectivley. The timing resolution is approximately 100 ps insigma and does not change between 1 and 4 atm. InFig. 2, the correlation between the mean QDC value ofthe Xe detector at 4 atm and the time of flight is plotted.
The secondary beam particles with Z up to 55 are clearly
identified. The Z spectrum around 50 was deduced fromthe energy-loss information of the Xe detector, as shownin Fig. 3. The root-mean-square resolution of ∆Z = 0.2(5σ separation) is achieved.
These results are very promising for the high-intensity
and heavy RI-beam experiments. A more detailed analysis is in progress.
References

1) M. Mimura et al., Jpn. J. Appl. Phys. 48, 076501 (2009).
2) M. Kanazawa et al., Nucl. Phys. 746, 393c (2004).

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