Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 48 (2015)

The oﬀ-line adjustment of the parasitic production of low-energy
RI-beam system for installation in BigRIPS
T. Sonoda,∗1 M. Wada,∗1 I. Katayama,∗1 N. Fukuda,∗1 H. Iimura,∗2 N. Inabe,∗1 T. Kubo,∗1 K. Kusaka,∗1H. Takeda,∗1 H. Suzuki,∗1 M. Reponen,∗1 M. Wakasugi,∗1 K. Yoshida∗1 and SLOWRI collaborations
The construction of a low-energy RI-beam facility
SLOWRI1) began in 2013. The parasitic low-energy
RI-beam production system (PALIS)2) in SLOWRI
was successfully manufactured in 2014. The preliminary installation of PALIS in the second focal planechamber (F2) in BigRIPS was demonstrated. The performance evaluation of PALIS by oﬀ-line experiments
is in progress.
We will restore unused RI-beams by installing asmall gas cell in the F2 chamber in BigRIPS. This will
provide parasitic low-energy RI-beams for various precision experiments whenever BigRIPS experiments arein operation. In order to realize the parasitic beam production, there should be no interference from PALIS
in terms of BigRIPS beam tuning, detector operationand replacement, vacuum level, etc. This year we conﬁrmed the following items whether there is no mechanical interference due to the installation of PALIS in theF2 chamber. The ﬁrst item was the ﬁtting check between the F2 chamber and PALIS which is integrated
with the F2 chamber’s roof3) . Position reproducibility was ensured by using locating guide pins equippedin PALIS. PALIS, whose weights approximately 1100kg, was carefully moved by a ﬂoor-operated crane andplaced on the F2 chamber within <1.0 mm reproducibility without any trouble. The second item wasthe applicability for the replacement of detectors usedfor BigRIPS beam tuning without taking PALIS away.
There are three detectors, i.e., two PPACs and one
plastic scintillator inside the F2 chamber, they need
to be occasionally replaced for maintenance. By using two maintenance windows equipped in PALIS, weconﬁrmed that these detectors were able to be put inor out. The third item was the vacuum level for theF2 chamber together with PALIS. After several hoursof pumping, the pressure in the F2 chamber was 10−4Pa, the same as in conventional operation. Fig. 1 shows
the photographs during the installation test of PALIS
in the F2 chamber in BigRIPS.
The oﬀ-line experiment was started for the performance evaluation of PALIS. A new diﬀerential pumping method was implemented in PALIS from the resultof a prototype system4) . The diﬀerential pumping region is devided into four sections. The capability ofdiﬀerential pumping was veriﬁed; a pressure diﬀerence
from approximately 105 Pa argon or helium in the gas
cell down to 10−4 Pa in the ﬁnal section was achieved,
while using a 2 mm diameter gas cell exit hole.
∗1∗2PALIS
PALIS

Gas
Gas cellcellSLITSLITBigRIPSBigRIPS F2
F2 chamberchamberFig. 1. The upper photo shows the entire PALIS integrated
with the F2 chamber’s roof. The lower photo is the gas
cell part in PALIS.
Pressure(Pa)Pressure (Pa)101055

Argongas
Argon gas101033

HeliumHelium gasgas

101011-11010-1-3
1010-3Differential
pumping region
region (70cm)(70cm)
Differential pumping

Section1
Section1

GascellGas cell(exit2mm)(exit holehole 2mm)

Section3
Section3Section2
Section2

Place
Place

Section4
Section4

Fig. 2. Capability of diﬀerential pumping in PALIS.

We plan to start on-line commissioning experiments
in 2015.
References
1) M. Wada et al., Hyp. Int. 199 (2011) 269.
2) T. Sonoda et al. APS Conf. Proc. 1104 (2009) 132.
3) T. Sonoda et al. ARIS2014 proceedings to be published.
4) T. Sonoda et al.: Nucl. Inst. and Meth. B295 1(2013).

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