Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 52 (2019)

Measurement of total kinetic energy using LaBr3 (Ce) crystal in
ZeroDegree spectrometer for two-step experiment
H. Suzuki,∗1 D. S. Ahn,∗1 N. Fukuda,∗1 H. Takeda,∗1 Y. Shimizu,∗1 R. Taniuchi,∗1 H. Wang,∗1 S. Takeuchi,∗2,∗1
and K. Yoshida∗1

Light output [ch]

8400
8300
8200
8100
8000
7900
7800
7700
7600
7500

12.6 12.8 13 13.2 13.4 13.6 13.8 14

Fig. 1. Relation between light output from LaBr3 (Ce) crystal
2
and calculated EZ by ATIMA.5)∗2RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo

12947+Ag102

10126Ag46+

2.7

A/Q

2.75

12.8

2.85

Fig. 2. Separation of Ag isotopes in A versus A/Q. 4.6σ
separation was achieved between 129 Ag47+ and 126 Ag46+ .

the light output and calculated energy-loss of RIs using
an energy-loss code ATIMA.5) Owing to the quenchingeﬀect, the light output was not proportional to the en2
ergy loss. In this experiment, EZ (E; energy loss in thecrystal) was found to be proportional to the light output,
as shown in Fig. 1. In previous studies by Kobayashi4)
2√E respectively, were proand Taniuchi et al.,6) EZ 2 andZ
posed as the proportional variables. It is unclear why
the quenching eﬀects are diﬀerent in these three cases.
It may be caused by the width of the Z range, which was41–50 in our case, 28–52 in Ref. 4), and 8–50 in Ref. 6).
The distribution of A in the two-step experiment was0.95 in RMS around 129 Ag47+ . Thus, the resolution ofA was 0.8% and 3σ separation was achieved between thefully-stripped 129 Ag47+ and H-like 126 Ag46+ in mass. InA/Q axis, 3.5σ separation was obtained between these
two isotopes. Thus, 4.6σ separation was achieved using
both A/Q and A separations. Figure 2 shows the separation of Ag isotopes in the two-step experiment in Aversus A/Q plot. The fully-stripped RIs are well separated from the H-like RIs. The charge number, Q, wasdeduced from A/Q and A. 2.5σ separation was achievedin the Q separation.
References

E 2/Z [GeV2] (calc. by ATIMA)∗1134132130
128
126
fully−
124 stripped ions122
H−like ions
120
118
116
2.55 2.6
2.65

Mass number (A )A LaBr3 (Ce) crystal was used as the total-kineticenergy (TKE) counter for particle identiﬁcation (PID)
in the ZeroDegree spectrometer in the two-step experiment.1) In this experiment, events of partially-strippedradioactive isotopes (RI) were not negligible, because themass numbers, A, of RIs produced at the target at theentrance of ZeroDegree were over 100 and their kinetic
energies were 200 MeV/nucleon. For the PID, the atomic
number, Z, and the mass-to-charge ratio, A/Q, were deduced based on a TOF-Bρ-∆E method. However, theA/Q resolution in ZeroDegree with Medium-ResolutionAchromatic mode2) was 0.061% in RMS and inadequate
to separate fully-stripped RIs from the partially-stripped
ones. Thus, the value of A was deduced from the velocity(β) and TKE of each RI and was used for the separation.
The LaBr3 (Ce) crystal3,4) was mounted at the endof ZeroDegree. It is cylindrical in shape with 3-inch
diameter and length, covered with a 0.5-mm thick Al
housing. Nine PIN-photodiodes were attached to theback of the crystal through a light-guide made of Lucite.
Five diodes with eﬀective areas of 18 mm2 (S3204-08;Hamamatsu Photonics K.K.) were arranged in the shapeof a cross and other four diodes of 10 mm2 (S3590-18;Hamamatsu) were placed at the four corners. The signal
from each diode was ampliﬁed by a pre-ampliﬁer (MSI8; mesytec GmbH & Co. KG) whose dynamic range
was set to be 1 GeV in Si energy-loss equivalent anda shaping ampliﬁer (MSCF-16; mesytec) whose shaping
time was set to be 2 µs.
The energy of the crystal was calibrated by comparing

1) H. Suzuki et al., RIKEN Accel. Prog. Rep. 52, (2019).
2) T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003(2012).
3) R. Kambayashi, Master’s thesis, Rikkyo Univ. (2011).
4) K. Kobayashi, Master’s thesis, Rikkyo Univ. (2012).
5) ATIMA web page, https://web-docs.gsi.de/~weick/atima.
6) R. Taniuchi et al., RIKEN Accel. Prog. Rep. 48, 210(2015).

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