Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 48 (2015)

Low-pressure MWDC system for ESPRI experimentY. Matsuda,∗1,∗2 J. Zenihiro,∗2 W. Chao,∗2,∗3 H. Sakaguchi,∗2,∗4 J. Tanaka,∗4 M. Tsumura,∗2,∗5 and
N. Nakatsuka∗2,∗5

MWDC

310 mm

Beam

MWDC

(a)

1000 mm(c)(b)

Vacuum gauge
HV connectors
Gas in/out∗2∗3∗4∗5V5V9V8V6640B

V3

SS-4MG
V10SS-4L

V1V2

V11V12INFICON
VGC402

MWDC

Leak port
To dry pump

From gas cylinder

CDG025DGashandler

CDG025DV4Vacuum chamber

MWDCFig. 2. Schematic diagram of the gas handler system.

Efficiency [%]100 Total
W180W2C1C2604020400300500
High voltage [-V]600

Fig. 3. Detection eﬃciency for the 200 MeV/nucleon Xebeam. The beam intensity was 6×103 particles perpulse (pulse width 1 s). The threshold voltages of theASDs were -20 mV. Deﬁnition of the symbols is thesame as in Ref. 3.

ASD

MWDC

MWDC

X-X ′ -Y -Y ′ -X-X ′ -Y -Y ′77.5 mm(X) × 77.5 mm(Y )2.5 mm (Anode-Potential)
4.8+0.0−0.1 mm (Cathode-Cathode)
W-Re / Au (Diameter: 16 µm)
Al / Au (Diameter: 80 µm)
Kapton / Al (Thickness: 7.5 µm)
Aramid (Thickness: 4 µm)

Conﬁguration
Eﬀective area
Drift length
Gap
Anode wire
Potential wire
Cathode foil
Window foil

200Fig. 1. Schematic layout of the MWDC system: (a) verticalsectional, (b) cross sectional, (c) front views.
∗1

Table 1. Speciﬁcation of each MWDC. The design was
based on the MWDC for SAMURAI2) .

0Vacuum chamber

Beampurity of more than 99%. The eﬃciency reached 100%
without any electric discharge. In addition, position
resolution for each plane was about 60 µm (rms).
In summary, we constructed a low-pressure MWDC
system. By using the 132 Xe beam and the i-C4 H10gas, basic characteristics were evaluated for the beam
intensities of 103–4 pps. We will further study thesequantities for the beam intensities of 105–6 pps.

MKS 246C

Elastic scattering of protons with RI beams (ESPRI)
has been used to study the ground-state properties ofunstable nuclei1) . In order to achieve good energy resolution in the experiment, position and angular resolutions of 100 µm and 0.1 mrad are required at a positionof the solid hydrogen target. The typical energy andintensity of the beam are 200-300 MeV/nucleon and
105–6 particles per second (pps), respectively. This report describes a multi wire drift chamber (MWDC)
system newly constructed for this purpose.
Figure 1 shows a schematic layout of the system, andTable 1 shows the speciﬁcation of the MWDC. Two
MWDCs are installed inside a vacuum chamber at adistance of 1 m. Through the SHV connectors, negative potentials are applied to the cathode planes andthe potential wires against the anode wires. Signals
from the anode wires are converted into LVDS signals
by the ASDs (GND, GNA-210), and fed to multihit
TDCs.
The chamber including the MWDCs, with volumeof about 25 L, is ﬁlled with 100% quench gas (CH4 ,C2 H6 , i-C4 H10 ) at low pressures to reduce multiple
scattering of the beam. Figure 2 shows a schematic
diagram of the gas handler system. The pressure ofthe gas is controlled with a pressure controller (MKS,640B), and measured with two vacuum gauges (INFICON, CDG025D-X3). The ﬂow rate is adjusted witha metering valve (Swagelok, SS-4MG / SS-4L).
Basic characteristics of the system were evaluatedwith a 132 Xe beam at HIMAC. Figure 3 shows thedetection eﬃciency as a function of the bias voltage
when i-C4 H10 (99.5%) was used at 6666 Pa. Deﬁnitionof symbols in Fig. 3 is the same as in Ref. 3. The ﬂow
rate was about 100 cc/min at 1 atm to maintain theReferences
1) Y. Matsuda et al.: Phys. Rev. C 87, 034614 (2013).
2) T. Kobayashi et al.: Nucl. Instr. and Meth. B 317, 294(2013).
3) Y. Matsuda et al.: Nucl. Instr. and Meth. A 670, 25(2012).

Department of Physics, Konan University
RIKEN Nishina Center
Department of Physics, Peking University
RCNP, Osaka University
Department of Physics, Kyoto University- 211 -

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