Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 49 (2016)

Circulation detector for Rare RI Ring
D. Nagae,∗1 Y. Abe,∗1 Y. Yamaguchi,∗1 F. Suzaki,∗1,∗2 S. Naimi,∗1 Z. Ge,∗1,∗2 H. Miura,∗2 S. Ohmika,∗2
Y. Takeuchi,∗2 T. Nishimura,∗2 N. Tadano,∗2 I. Kato,∗2 T. Yamaguchi,∗2 T. Suzuki,∗2 Y. Ichikawa,∗3 Y. Tajiri,∗3K. Hiraishi,∗3 T. Matsumoto,∗3 T. Moriguchi,∗3 S. Suzuki,∗3 A. Ozawa,∗3 Y. Yanagisawa,∗1 H. Suzuki,∗1H. Baba,∗1 S. Michimasa,∗4 S. Ota,∗4 H. Miya,∗4 T. Watanabe,∗1 M. Wakasugi,∗1 T. Uesaka,∗1 and Y. Yano∗135Counts [/100 ps]

Cl ions were circulated for approximately 40 turns
and 10 turns, respectively. The preliminary revolution
times of 378.32(6) ns and 386.3(1) ns were obtained for36
Ar and 35 Cl, respectively.
104

103

102

10
100.0

5.0

10.0

15.0

20.0

25.0

Time [µs]Counts [/ 1 ns]

Fig. 2. Circulation time spectrum of 78 Kr. Noise generated by the kicker magnet is observed at approximately
0.05 µs.
10 4(a) 36Ar

10 310 21010.0

Counts [ / 50 ps]

A circulation detector consisting of a carbon foil anda multichannel plate (MCP) has been developed forconfirming that particles can be stored and for evaluating the revolution time in the Rare RI Ring1) . Although the basic concept of the circulation detector isthe same as those developed at GARIS and Tsukuba2) ,and GSI3) , an enlargement of the sensitive area is required to cover a large beam profile in the Rare-RIRing. A schematic view of the detector is shown inFig. 1. A large and thin carbon foil (100 × 50 mm2and 60 µg/cm2 ) was developed at RIKEN4) . A stored
particle generates secondary electrons when passing
through the carbon foil. Secondary electrons are accelerated by an acceleration electric field Eacc applied
between the carbon foil and an acceleration grid, andthey are then deflected at 90 degree towards the MCP
by an electrostatic mirror field Emir applied between
two parallel grids. These grids are made of gold-plated
tungsten wires with a diameter of 40 µm. The acceleration field (Eacc ) and the mirror field (Emir ) are chosen
to satisfy the relation 2Eacc = Emir .
The circulation detector was used in the first commissioning experiment where the 78 K primary beam
was used. The detector was used in the same manner in the second commissioning experiment using thesecondary beam of 36 Ar and 35 Cl produced by the fragmentation reaction of a primary beam of 48 Ca at an energy of 345 MeV/nucleon on a 9 Be target with a thickness of 25 mm. A circulation time spectrum of 78 Kr
is shown in Fig. 2. Particles were successfully stored
approximately 60 turns. A revolution frequency wasestimated to be 2.639 MHz from the circulation timespectrum. Figures 3(a) and 3(b) are circulation time
spectra for 36 Ar and 35 Cl, respectively. 36 Ar ions and2.0

4.0

6.0

8.0

Time [µs]

10.0

12.0

14.0(b) 35Cl

10 3
10 2
101W+Au wire
(φ40 µm / 1 mm pitch)(Vacc)

0.0

W+Au wire(φ40 µm / 3 mm pitch)(Vmir)

1.0

1.5

2.0

2.5

3.0

Time [µs]

3.5

4.0

4.5

5.0

Fig. 3. Circulation time spectra of (a) 36 Ar and (b) 35 Cl.
Arrows indicate signals corresponding to particles.

Ion Beam

C-Foil (60 µg/cm2)(Vfoil)0.05

e-References
MCP

1) A. Ozawa et al., Prog. Theor. Exp. Phys. 03C009(2012).
2) T. Mizota et al., Nucl. Instr. and Meth. A 305, 125(1991).
3) F. Busch et al., Nucl. Instr. and Meth. 171, 71 (1980).
4) H. Hasebe et al., RIKEN Accel. Prog. Rep. 42, 133(2009).

Fig. 1. Schematic view of the circulation detector.
∗1
∗2
∗3
∗4

RIKEN Nishina Center
Department of Physics, Saitama University
Institute of Physics, University of Tsukuba
Center for Nuclear Study, University of Tokyo- 181 -