Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

First implementation of the new segmented implantation detector fordecay studies with BRIKEN array
R. Grzywacz,∗1∗2 M. Singh,∗1 T. King,∗1 R. Yokoyama,∗1 J. Agramunt,∗3 N. Brewer,∗2 S. Go,∗4J. Heideman,∗1 A. Keeler,∗1 J. Liu,∗4 S. Nishimura,∗4 V. Phong,∗4∗5 M. Rajabali,∗6 B. Rasco,∗2K. Rykaczewski,∗2 D. Stracener,∗2 J. L. Tain,∗3 A. Tolosa-Delgade,∗3 M. Wolinska-Cichocka,∗7
and the BRIKEN collaboration
A new implantation detector was developed at theUniversity of Tennessee and implemented for the ﬁrst
time during the October 2017 BRIKEN1) campaign.
The detector is an evolved version of the array proposed previously2) but uses YSO instead of a plastic
scintillator. The developments were driven primarily
by the need to have a fast trigger detector for the neutron time-of-ﬂight array VANDLE.3,4) The beneﬁts ofusing an inorganic-crystal scintillator such as YSO are
its high eﬀective atomic number (Z = 35) and density (4.4 g/cm3 ) which result in a short range of beta
particles. Both properties should enable a very highdetection eﬃciency and good spatial correlation between ions and decay, thereby providing a good alternative to DSSDs. The YSO scintillator is also very
fast and radiation hard, and therefore, it can be usedwith high rates. The disadvantage of using this highZ material is its relatively high absorption for the γrays, which has to be considered with measurements atenergies below Eγ = 100 keV. The detector unit consisted of a segmented YSO crystal and ﬂat-panel multianode photomultiplier (Hamamatsu H8500 or H12700series). The readout from the photomultiplier useda resistive-network scheme for event position determination. The signals were digitized and integrated
with the BRIKEN digital data acquisition system. TheYSO crystal was 5-mm thick and was assembled from1 × 1 mm2 segments arranged in a 48 × 48 array, as
shown in Fig. 1. The isolation among segments of thedetector, the cover of the detector face, and the sides
used ESR (3M) reﬂector material. The YSO array wasattached to the photomultiplier with a 2-mm quartz
diﬀuser glass. The detector unit was enclosed in a
3D printed light-tight enclosure with a thin front window. It was placed inside the BRIKEN matrix directly
behind the WAS3ABI5) detector array with the YSO
crystal centered between two clover detectors. During the DA17-02 experiment ions with Z < 30 werepartially implanted in the YSO detector enabling theability to test the ion-implantation correlation performance of the detectors. Light yield for heavy ions inthe YSO is unknown. It was critical to establish exper∗1
∗2
∗3
∗4
∗5
∗6
∗7

University of Tennessee
Oak Ridge National Laboratory (ORNL)
Instituto de Fisica Corpuscular, Valencia
RIKEN Nishina Center
VNU Hanoi University of ScienceTennessee Technological University
HIL University of Warsaw- 150 -imentally the optimum operating voltage that avoids
the saturation of the photomultiplier and enables thedetection of signals induced by ions and betas. The
explored range of voltages was from 550 V to 1200 V.
The electronic signals from the Anger logic and common dynode were split into two electronic tracks. One
set of signals was dedicated to measuring heavy ionsand was fed directly into electronics; the other signals
used fast ampliﬁers and were needed to record beta
particles. Owing to a very high light yield and very
eﬃcient light collection, the system had to be operated at a relatively low voltage of 575 V during theexperiment. Despite the resulting small ampliﬁcation,
we were able to detect signals induced by beta particles with a very high eﬃciency of at least 65%. We
observed moderate distortion of the image which will
be corrected by the selection of a more appropriate
voltage divider. The detector operation was very stable throughout the experiment. The advantages of thesimplicity of operation of this new detector were clearlydemonstrated.

Fig. 1. (Left) Segmented YSO scintillator before coupling
to the photomultiplier. (Right) Implantation profile
recorded by the segmented YSO detector.

References
1) A. Tarifeno-Saldivia et al., J. of Instrum 12, 1 (2017).
2) M. Alsudifat et al., Physics Procedia 66, 445 (2015).
3) W.A. Peters et al., Nucl. Instrum. Methods A 836, 122(2016).
4) M. Madurga et al., Phys. Rev. Lett. 117, 092502 (2016).
5) S. Nishimura et al., RIKEN Accel. Prog. Rep. 46, 182(2013).