Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 53

Purification of slowed-down RI beam
T. Sumikama,∗1 D. S. Ahn,∗1 N. Fukuda,∗1 N. Inabe,∗1 T. Komatsubara,∗1 K. Kusaka,∗1 M. Ohtake,∗1H. Sakurai,∗1 Y. Shimizu,∗1 H. Suzuki,∗1 H. Takeda,∗1 Y. Yanagisawa,∗1 K. Yoshida,∗1 M. Dozono,∗2 N. Imai,∗2S. Michimasa,∗2 R. Tsunoda,∗1,∗2 Y. X. Watanabe,∗3 M. Hausmann,∗4 and O. Tarasov∗1,∗5(1) purification of the RI beam using the two-stage
separation,(2) two-step momentum compression, and(3) transport of three charge states coupled withPID using a time-of-flight (TOF) measurement
after the purification.
In this report, we focus on the RI-beam purification.
An experiment to verify the HIPSER concept wasperformed using a 107 Pd beam produced with the BigRIPS separator at RIKEN RIBF. The 107 Pd beams
were separated at the first stage of BigRIPS using a6000
105

RuRh
107
Pd108
Ag
109
Cd106

5000

counts

4000
3000
2000
1000
040

30

20

10010203040x at F3 (mm)Fig. 1. Horizontal-position distributions of 107 Pd and itsisotones at F3. The results of 105 Ru, 106 Rh, 107 Pd,
108
Ag, and 109 Cd are shown by the green-dashed, blackdashed, red-solid, black-solid, and green-solid lines, respectively.
∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Center for Nuclear Study, University of Tokyo
Wako Nuclear Science Center, KEK
FRIB, MSU
NSCL, MSU

- 102 -700
105Ru
Rh
107
Pd108
Ag
109
Cd600

106500countsThe purity of a slowed-down RI beam at the second stage of the BigRIPS separator1) is important forparticle identification (PID) under the condition of atotal rate of 105 pps or higher.2) High-purity sloweddown RI beams are desirable for experiments at BigRIPS and the OEDO beamline.3) A high-intensity purified slowed-down exotic RI beam (HIPSER) concept
is proposed to obtain high-intensity and high-purity
RI beams using two-stage separation with two thickwedge degraders before measurement using beamline
detectors for PID. The HISPER concept consists ofthree technical components:

400300200100040

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20100x at F7 (mm)10203040Fig. 2. Same as Fig. 1 but for the positions at F7.

wedge degrader with a thickness of 4.5 mm at F1 andthe F2 slit with a ±5-mm setting. The thickness-torange ratio (d/R) was 0.47. The energy was slowed
down from 254 to 174 MeV/nucleon. The contaminants at F2 were isotones of 107 Pd, since the horizontal position xF2 of 107 Pd at F2 were the same as thoseof the isotones. Figure 1 shows xF3 distributions of105Ru, 106 Rh, 107 Pd, 108 Ag, and 109 Cd beams measured at F3. The positions at F2 and F3 show therelation, xF3 = −xF2 . The central values of the xF3
distribution for these RI beams were the same.
With a thicker wedge degrader at F5, the 107 Pd
beam could be separated from its isotones.1,2) The second wedge degrader at F5 had a thickness of 3.5 mm(d/R = 0.69). The F7 position xF7 of the 107 Pd beam
was separated from the isotones, as shown in Fig. 2.
By setting the F7 slit as −10 mm < xF7 < +5 mm, thepurity of 107 Pd was obtained as 32%. The beam energy
between F5 and F7 was 78 MeV/nucleon. The TOF
measurement for the three charge states was performedat the ZeroDegree spectrometer. The charge-state separation at the ZeroDegree spectrometer, influence ofhigher-order aberration, and beam-energy broadening
due to energy-loss straggling will be investigated in a
future analysis.
References

1) T. Kubo, Nucl. Instrum. Methods Phys. Res. B 204, 97(2003).
2) T. Sumikama et al., Nucl. Instrum. Methods Phys. Res.
B 376, 180 (2016).
3) S. Michimasa et al., Prog. Theor. Exp. Phys. 2019,043D01 (2019).