II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Development of the GAGG(Ce) calorimeter for the cluster knockout
reaction measurement
R. Tsuji,∗1 J. Zenihiro,∗1 T. Uesaka,∗2 J. Tanaka,∗2 K. Higuchi,∗2,∗5 S. Kurosawa,∗3 H. Baba,∗2 S. Takeshige,∗4and Y. Hijikata∗1,∗2A new project named “ONOKORO” was recently
launched to investigate the cluster formation phenomena in nuclei and nuclear matter with cluster knockout reactions.1) In this project, we plan to performsystematic measurements for various stable and unstable nuclei at the following accelerator facilities: RIBF,RIKEN, RCNP, Osaka University, and HIMAC at QST.
At RCNP, we will measure the knockout reactions fromﬁxed targets of stable nuclei with proton beams at 200–
400 MeV. The expeirmental technique is already established with double-arm high-resolution magnetic spectrometers. At RIBF and HIMAC, the knock-out reactions with inverse kinematics will be measured with stable and unstable heavy-ion beams on liquid or solid hydrogen targets. For this measurement, we have proposeda new detector telescope, named TOGAXSI,2) consisting of silicon strip detectors (SSD) and GAGG(Ce)calorimeters. In this paper, we report the results of theperformance test of the GAGG(Ce) calorimeters.
We chose the GAGG(Ce) scintillator to measure thekinetic energies of the recoil protons and knockout clusters (100–250 MeV/nucleon) because it has good scintillation properties compared to other standard scintillators such as NaI(Tl) and CsI(Tl). Figure 1 showsa photograph of the GAGG(Ce) crystal with a size of40 × 40 × 120 mm3 . In the ONOKORO experiments,
high counting rates up to 100 kcps are expected; therefore, a good time response is required as well as a goodenergy resolution. To detect the scintillation photons,
we prepared several photo sensors of PMT (R7600U,R11265U-20), APD (S8664-1010) and PD (S3584-08)
produced by Hamamatsu. The PMT has a fast time
response and a high gain, but low photo eﬃciency at∼500 nm compared to APD and PD. Because APD andFig. 1. The GAGG(Ce) crystal (40 × 40 × 120 mm3 ).
∗1∗2∗3∗4∗5Fig. 2. Position dependence of the light outputs of the right(blue) and left (red) sensors located at X = ±60 mm.

PD have small gains, we newly designed a fast ampliﬁer
circuit with a high-speed operational ampliﬁer (AnalogDevices, AD8000).
To check the performance of the GAGG(Ce) calorimeter for high-energy charged particles, we performed
a test experiment using p and α beams at 75–
230 MeV/nucleon at HIMAC. We tested several detector conﬁgurations, but we brieﬂy report the results of
one setup: two photo sensors (PMT/APD/PD) were attached on both sides of the crystal, and p and α beams
at 75 and 100 MeV/nucleon were impinged on the longside. The energy resolutions are <1% and <0.6% for the100 MeV/nucleon proton and α beams focused on thecenter of the crystal, respectively. We also used defocused beams to check the position dependence by tracking the beam trajectories with SSDs. Figure 2 shows
the correlation of the light outputs of the left and rightsensors versus the horizontal position of the beam (X).
On the far side from the sensor, attenuation eﬀects can
be clearly seen, but the signals are widely spread wherethe beam is close to the sensor. This is because the solid
angle of the sensor drastically changes depending on thevertical (Y ) positions as well as X. We applied a correction of the X and Y position dependences, and ﬁnally, agood energy resolution of 0.3–0.6% for 100 MeV/nucleon
α beams was obtained in the wide range of the crystal.
The result is good enough to achieve a separation energy
resolution of ∼2 MeV in rms.
References

Department of Physics, Kyoto University
RIKEN Nishina Center
NICHe, Tohoku University
Department of Physics, Rikkyo University
Department of Physics, Toho University

1) T. Uesaka et al., Grant-in-Aid for Specially Promoted Research, Grant Number 21H04975.
2) T. Uesaka et al., RIBF Construction Proposal, NP2112SAMURAI72 (2021).

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