Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 50 (2017)

Gas circulation and puriﬁcation system for RIBF-PALIS experiment†
T. Sonoda,∗1 T. Tsubota,∗2 M. Wada,∗1 I. Katayama,∗1 T.M. Kojima∗1 and M. Reponen∗3

†
∗1
∗2
∗3

Condensed from the article in Rev. Sci. Instrum. 87, 065104(2016)RIKEN Nishina CenterTokyo KOATSU Co., Ltd.
Department of Physics,University of Jyvaskyla- 201 -Particularly, in the semiconductor production process,highly pure argon gas is indispensable for use as atomospheric gas, but the gas is usually used once andthen disposed of. The reduction of cost of highly pureargon gas is expected on implementing the gas circulation and puriﬁcation system.3)
Detail information on this work can be founded in a
published article.4)
Piezo valve

High-energy RI-beam Exit hole
Degrader2mm

Dew-point
transmitter(PURA)

Gas cellGas purifier 2T.M.P

Ceramic tube
Scroll pumpLong tube(5m)

BypassSection2

Section3

Q2

Q

F2

SPIG

Q1

Dry pump2(DRY2)

Dry pump1(DRY1)

VQ1

Low-energy
RI-beam

Differential pumping

Section1

high-dose radiation area

PT3

Ceramic tube

T.M.P

Scrollpump

Pressure gauge
Long tube (5m)
Gas purifier 1

A gas circulation and puriﬁcation system was developed for the parasitic low-energy RI-beam production
system (PALIS).1,2) The development was motivatedby the following three requirements; 1) to avoid pollution by radioactive Ar gas (41 Ar, T1/2 =109.61(4)min)
diﬀusing into the air, which is created by the reactionof 40 Ar and an intense neutron ﬂux; 2) to reduce consumption of the buﬀer gas, since the exhausted buﬀergas ejected from the gas cell was thus far disposed ofvia a diﬀerential pumping system; and 3) to enhance
the gas purity to avoid a loss in the low-energy RIbeam extraction eﬃciency.
An overview of the gas cell, diﬀerential pumping system, and the gas circulation and puriﬁcation system isshown in Fig. 1. The main part of the gas circulation system is located 5 m away from the BigRIPS
F2 room. The interfaces between the PALIS gas celland circulation system consist of several long gas tubes
and compressed air tubes for valve control. Duringon-line beam experiments, the radiation level in theF2 room increases by several hundred mSv, whereby
the main contribution to the radiation is the highintensity neutron ﬂux. Therefore, it is not possible
to access the F2 room during experiments, and all
devices should be controlled remotely. A high-ﬂowrate gas cell ﬁlled with 1 atm of buﬀer gas (argon orhelium) is used for the deceleration and thermalization of high-energy RI-beams in PALIS experiments.
The exhausted buﬀer gas is eﬃciently collected using
a compact dry pump and returned to the gas cell. Thebuﬀer gas is eﬃciently puriﬁed using two gas puriﬁers
as well as through collision cleaning, which eliminates
impurities including gas.
We have achieved a gas recovery eﬃciency of 97% for
Ar, when the pressure of the gas cell was set at 105 Pa.
This value falls within the permissible range considering the natural abundance of 41 Ar in air. In addition,
the consumption of the expensive, high-purity buﬀer
gas was drastically reduced. The replacement rate ofAr gas to a new bottle (47 L, 15 MPa) amounts tojust one bottle per week, even if a gas ﬂow rate of 15
L/min is spent continuously to maintain a pressure of 1
atm in the gas cell. Moreover, the achieved gas purity
was 99.9999999% (grade 9.0; impurity level: 1 part perbillion (ppb)), which was evaluated from the moisture
content in the gas using a dew-point transmitter.
This system can be extended to any application
based on a gas cell and is feasible for any type of gas.

PT2

PT1

Source gas(Ar/He)

VQ8

Buffer tank2
VQ2

Air operation valve
NA1

T-type branch valve
Needle valve

VB1

Clack valves

Buffer tank1
Back pressure valve
VQ11

Fan cooler

Activated carbon
Bellows typefilter
compressor
Evacuation line

T.M.PScroll pump
The main part of the circulation

Fig. 1. Overview of the gas cell and the gas circulation andpuriﬁcation system. The red arrows indicate the regular
direction of circulation, and the green arrows indicate
the direction of the evacuation line. The blue arrows
indicate the direction of gas ﬂow under some special
conditions.

References1) T. Sonoda et al., AIP Conf. Proc. 1104 132 (2009).
2) T. Sonoda et al., Nucl. Inst. and Meth. B 295 1 (2013).
3) Japan Chemical Daily, Aug. 23, (2016).
4) T. Sonoda, T. Tsubota et al., Rev. Sci. Instrum. 87,065104 (2016).