Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 47 (2014)

Development of a silicon detector array with large dynamic range
M. Kurokawa,∗1 H. Baba,∗1 J. Blackmon,∗2 J. Elson,∗3 M. McCleskey,∗4 T. Motobayashi,∗1 H. Murakami,∗1T. Murakami,∗5 H. Otsu,∗1 C. Rasco,∗2 A. Saastamoinen,∗4 L. Sobotka,∗3 L. Trache,∗6 R. Tribble,∗4K. Yoneda,∗1 and J. Zenihiro∗1We have developed an array of strip silicon detectors
for the Coulomb beakup experiments with proton-richheavy nuclei at intermediate energies. The breakup
reaction, where the ﬁnal state consists of one or two
protons and the residual heavy charged particle, is aninverse reaction of the radiative proton capture and has
been considered one of the most promising methods toextract the reaction rate of the capture process. The
extracted rate gives us insight into the nucelosynthesis
through the rp process, consisting of sequential proton
captures on nuclei for producing heavier ones. The array measures the four momentum of each particle inthe ﬁnal state for specifying the excitation energy ofthe state along with the SAMURAI spectrometer. We
plan to build an experimental setup capable of measuring the rates involving nuclei with masses up to 100.
The heaviest case is the breakup of a 101 Sb nucleus.
The energy deposit of the breakup fragment 100 Sn is502 times that of a proton. The dynamic range of thearray must be larger than the diﬀerence in the energy
deposit. The design value for the upper and lower detection limits were set to 1 GeV and 200 keV, respectively, after taking into consideration the possibility ofthe pile-up of events.
The total number of signal channels becomes morethan one thousand for suﬃcient momentum resolution.
In order to eﬀectively treat such a large number ofsignal channels and to suppress the cost per channel,
we need to employ the Application Speciﬁc Integrated
Circuits (ASIC) technology for the array.
In view of the above requirements, we constructed
an array consisting of newly developed preampliﬁer
ASIC providing a large dynamic range by implementing high- and low-gain channels,1) another ASIC system called HINP for subsequent pulse shaping,2) andthe silicon detector developed for the GLAST mission.3) The items in the following list were examined
for the characterization of the array by irradiating thedetector directly at the HIMAC facility .
(1) Linearity in the range from 390 keV to 300 MeV(2) Cross talk between neighboring strips(3) Yields of δ rays for the irradiation of heavy
∗1
∗2
∗3
∗4
∗5
∗6

RIKEN Nishina Center
Department of Physics and Astronomy, Louisiana State University
Department of Chemistry, Washington University in St.
Louis
Cyclotron Institute, Texas A&M University
Department of Accelerator and Medical Physics, National
Institute of Radiological Sciences
IFIN-HHFig. 1. Energy peak at around 390 keV obtained from theirradiation of a 150-MeV proton beam.

Fig. 2. Measured energy as a function of calculated energy.
The slope of the line is 1.

charged particles
The smallest energy deposit 390 keV was made by
a 150-MeV proton beam(Fig. 1). For larger deposits,
56
Fe and 84 Kr ions were accelerated as primary beams
and we selected secondary beams having a mass-tocharge ratio of two. The linear response of the lowgain channel shown in Fig. 2 indicates that the dual
gain system of the preampliﬁer ASIC succeeded in extending the upper limit to higher than 100 MeV, whichis the limit of the high-gain channel. The results obtained for the last two items will be used for the estimation of the background rates for the proton detection.
The determination of the upper and lower limits is thesubject for the next irradiation.
References
1) M. Kurokawa et al.: RIKEN Acc. Prog. Rep. 44, 148(2011).
2) G. L. Engel et al.: Nucl. Instrum. Meth. A 573, 418(2007).
3) T. Ohsugi et al.: Nucl. Instrum. Meth. A 541, 29(2005).

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