Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

Development of beam trigger detector with compact geometry
N. Chiga,∗1 A. Hirayama,∗1,∗2 S. Takeuchi,∗1,∗2 T. Sumikama,∗1 K. Yoshida,∗1 D. Ahn,∗1 H. Suzuki,∗1 andH. Otsu∗1A new scintillation detector used as a focal plane
beam trigger detector was developed for the ImPACTexperiment. The beam is spread over a wide acceptance of the ZeroDegree spectrometer in the momentum dispersive mode used in this experiment. Thisscintillation detector was required to cover a large effective area of 240×150 mm2 , which is the same as thatof PPAC.1) The eﬀective area of the present scintillation detector2) is 120×100 mm2 , which is smaller thanthat of PPAC. Because the vacuum chamber at F11 of
ZeroDegree is not large enough to install a wide scintillator with the present PMT of H7195, the compact
PMT of R11265U-200 is used for the new detector.
The use of R11265U-200 has the following advantages
compared with H7195: the length of 32.5 mm of thisPMT is much smaller than that of 215 mm of H7195.
The PMT has a transit time of 5.8 ns, which is shorter
than that of 40 ns of H7195.
The speciﬁcations of the new beam line trigger detector are listed in Table 1. The new detector, which
satisﬁes the requirement of the eﬀective area, is smaller
than present detector of 670 mm×100 mm. The newdetector can be used at other focal planes on the beamline at BigRIPS, ZeroDegree, or SAMURAI.

for each side, was 43 ps as shown in Fig. 2.
This work was funded by ImPACT Program ofCouncil for Science, Technology and Innovation (Cabinet Oﬃce, Government of Japan).

Table 1. Speciﬁcations of the detector.

Fig. 1. Schematic 3D-CAD model of the new detector.

240 × 150 mm2EJ-200, 0.2 mmt
R11265U-200 ×4524 mm × 100 mm
less than 100 psCounts

Eﬀective area (H × V)
Scintillator
PMT
Size of detector (H × D)
Requirement of time resolution100

χ2 / ndf
4.284 / 8
Constant
101.6 ± 5.8
Mean−6.165 ± 0.002
Sigma
0.04271 ± 0.00141

8060

Figure 1 shows a schematic view of the new detector. Four PMTs of R11265U-200 were attached on theleft and right side of the new detector. To ensure thatlight from the scintillator is eﬀectively collected in thePMT, light guides are used as optical connection between them. The PMTs and light guides were bondedby an optical cement using a dedicated jig to provide
a position accuracy within 0.5 mm. The light guides
work as a support frame of a thin scintillator. The
scintillator was mounted on the light guides using optical grease. It can be easily replaced with a diﬀerent
scintillator. A scintillator with a thickness of 0.1 - 0.5mm can be mounted.
The new detector successfully worked in the ImPACT experiments in spring and autumn 2016. Thetime resolution of the diﬀerence between left and righttimings, which was the average of up and down PMTs
∗1
∗2

RIKEN Nishina Center
Department of Physics, Tokyo Institute of Technology- 163 -40

200−7−6.8

−6.6

−6.4

−6.2

−6−5.8
−5.6
−5.4
−5.2
Time difference between left and right (ns)Fig. 2. Time diﬀerence between the left and right timings
for the secondary beams in the vicinity of 93 Zr at 58
MeV/u. The timing average of two PMTs on each sidewas used.

References
1) H. Kumagai et al., Nucl. Instrum. Methods. B317, 717(2013).
2) T. Ohnishi et al., RIKEN Accel. Prog. Rep. 42, 159(2009).