Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 48 (2015)

Slow neutron detector WINDS for (p, n) reaction
in inverse kinematics with SAMURAIJ. Yasuda,∗1 M. Sasano,∗2 R.G.T. Zegers,∗3 H. Baba,∗2 W. Chao ,∗2 M. Dozono,∗2 N. Fukuda,∗2 N. Inabe,∗2T. Isobe,∗2 G. Jhang,∗2,∗13 D. Kameda,∗2 T. Kubo,∗2 M. Kurata-Nishimura,∗2 E. Milman,∗2 T. Motobayashi,∗2H. Otsu,∗2 V. Panin, ∗2 W. Powell, ∗2 M. Sako, ∗2 H. Sato,∗2 Y. Shimizu,∗2 L. Stuhl,∗2 H. Suzuki,∗2T. Suwat, ∗2 H. Takeda,∗2 T. Uesaka,∗2 K. Yoneda,∗2 J. Zenihiro,∗2 T. Kobayashi,∗4 T. Sumikama,∗4 T. Tako,∗4T. Nakamura,∗5 Y. Kondo,∗5 Y. Togano,∗5 M. Shikata,∗5 J. Tsubota,∗5 K. Yako,∗6 S. Shimoura,∗6S. Ota,∗6 S. Kawase,∗6 Y. Kubota,∗6 M. Takaki,∗6 S. Michimasa,∗6 K. Kisamori,∗6 C.S. Lee,∗6 H. Tokieda,∗6M. Kobayashi,∗6 S. Koyama,∗7 N. Kobayashi, ∗7 H. Sakai,∗8 T. Wakasa,∗1 S. Sakaguchi,∗1 A. Krasznahorkay,∗9T. Murakami, ∗10 N. Nakatsuka, ∗10 M. Kaneko, ∗10 Y. Matsuda, ∗11 D. Mucher, ∗12 S. Reichert, ∗12 D. Bazin,∗3and J.W. Lee∗13output in the scintillator was set to be 70 keV protonenergy.
The timing resolution of WINDS bar was estimatedby using prompt γ ray from the liquid hydrogen target.
The timing reference was taken from the plastic scintillators SBT1,2 whose timing resolution is typically 40
ps in FWHM. The observed peak width of the prompt
γ ray was 800 ps in FWHM which is most due to thetiming resolution of WINDS. This timing resolution
corresponds to energy resolution of ∆E/E = 11%.
The neutron-detection eﬃciency depends on the energy of neutrons as well as the threshold on light output. The typical eﬃciency with a threshold of 60
keVee was estimated by using the Monte Calro code ofMCNP4) , and it varied from 40% at 0.6 MeV neutron
to 20% at 4 MeV neutron. The eﬃciency calibration
was performed by locating a neutron source of 252 Cf
at the target position with a NE213 liquid scintillator
whose absolute eﬃciency as well as energy and threshold dependence are well known. The data analysis iscurrently in progress.
Topview

Sideview

WINDS

1200 mm120°
5° step0mmnbeam

Rightn74°

20°

residualto SAMURAI 22°
122°

Liq. HWINDSTopELENSLeft90In April 2014, we performed the SAMURAI17 experiment1) at RIKEN RIBF to study Gamow-Tellertransition on 132 Sn by using (p, n) reaction with theWide-angle Inverse-kinematics Neutron Detectors for
SHARAQ (WINDS)2) and the SAMURAI spectrometer.
Figure 1 shows a schematic view of the experimental setup around the target. The secondary beam wastransported to a 10 mm thick liquid hydrogen target,
which was surrounded by the WINDS to detect recoil neutrons. From the measured neutron time-ofﬂight (TOF) and recoil angle, the excitation energy
and center-of-mass scattering angle are determined.
The WINDS consists of 61 plastic scintillators withsizes of 600 × 100 × 30 mm3 . In this experiment 12
scintillators of the ELENS3) with sizes of 1000 × 45 ×10 mm3 were also installed. The left and right wallswith respect to the beam line covered the angular region from 20 to 122 degrees with 5 degree steps. Topand bottom walls covered the angular region from 16
to 74 degrees with 3.5 degree steps. Each detector isplaced such that the 30-mm-wide (WINDS) or 10-mmwide (ELENS) plane is oriented to the target direction
and placed at a distance of 900 mm (1200 mm) fromthe target for left and right (top and bottom) walls.
The charge signal from each PMT is digitized by a
CAEN V792 QDC. The timing signal is processed bya leading-edge discriminator (LeCroy 4413) and digitized by CAEN V1190 TDC. In order to maintain alow threshold of neutron detection, the PMT voltage
is kept to be as high as possible, typically -2700V and-2500V for H7195 and H7415. The threshold for light

beam14°
residualLiq. H to SAMURAI16°72°
4° step

Botttom∗1Department of Physics,Kyushu University
RIKEN Nishina Center∗3 NSCL Michigan State University∗4 Department of Physics, Tohoku University∗5 Tokyo Institute of Technology∗6 CNS, University of Tokyo∗7 University of Tokyo∗8 ULIC, RIKEN Nishina Center∗9 MTA, Atomki∗10 Kyoto University∗11 Konan University∗12 Technical University Munich∗13 Department of Physics, Korea University∗2Fig. 1. A schematic view of the WINDS setup.

References1) M. Sasano et al.,: in this report.
2) K. Yako et al., RIKEN Accel. Prog. Rep 45, 137 (2012).
3) L. Stuhl et al., Nucl. Instr. Meth. A 736, 1 (2014).
4) Monte Carlo NParticle Transport Code System,
MCNP5-1.60 and MCNPX-2.7.0.

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