Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 51 (2018)

The progress of on-line commissioning study on parasitic productionof low-energy RI-beam system (PALIS) at BigRIPS
T. Sonoda,∗1 M. Wada,∗2 M. Reponen,∗3 I. Katayama,∗1 V. Sonnenschein,∗4 M. Oohashi,∗4 H. Tomita,∗4S. Nishimura,∗1 H. Iimura,∗5 T. M. Kojima,∗1 A. Deuk Soon,∗1 N. Fukuda,∗1 T. Kubo,∗1 K. Kusaka,∗1N. Inabe,∗1 Y. Shimizu,∗1 H. Suzuki,∗1 H. Takeda,∗1 Y. Yanagisawa,∗1 K. Yoshida,∗1 F. Arai,∗1 S. Arai,∗1Y. Ito,∗1 M. Rosenbusch,∗1 K. Okada,∗6 P. Schury,∗2 and H. Wollnik∗7∗1∗2∗3∗4∗5∗6∗7123500Stopp. eff.
calc. result
by LISEIon signal(Exp. result)102500

82000
61500

41000

2500
0
3000

Stopping efficiency (%)

Ion Signal (arb.u.)

3000

4000
5000
6000
Degrader thickness ( )

7000

8000

0Fig. 1. The extracted ion signal (circle points scaled by theleft vertical axis) and the calculated stopping eﬃciency(square points scaled by the right vertical axis) versus
the degrader thickness.

tive Cu ion signal, we conﬁrmed the performance ofthe laser ionization, extraction and ion transportationby using stable copper atoms that were evaporated
from a ﬁlament. As shown in Fig. 2, photo-ionized
63–65
Cu ions were observed even when RI-beams wereimplanted into the gas cell. In the next beam time,
we will further investigate the stopping eﬃciency, optimum size of the gas cell and space charge eﬀect.
700
600

Ion Signal (arb. u.)

The progress of the on-line commissioning study
on parasitic production of low-energy RI-beam system (PALIS)1) is reported. The beam time was dedicated for 24 hours in FY2017. Although PALIS can operate in a parasitic manner during the BigRIPS mainexperiment, the present commissioning study was useda main beam. The main aim of this experiment, whichis the conﬁrmation of photo-ionized RI-ions after thermalization in the gas cell, was not achieved in this limited experimental period. However, the ion extraction
behaviors in terms of the degrader thickness and laser
wavelength were investigated during RI-beam implantation to the gas cell.
The main beam was chosen from Cu isotopes suchas 66 Cu (5 × 104 pps/pnA primary beam) and 68 Cu(2 × 104 pps/pnA primary beam), other isotope beams
such as 67 Ni (5 × 102 pps/pnA primary beam) werealso included. We adjusted the primary beam intensityfrom 0.01 pnA to 10 pnA. The RI-beams were ﬁrst decelerated by a copper degrader, where the energy wasreduced from around 280 to 10 MeV/nucleon, and thenthermalized in the gas cell. A part of the RI-beams arestopped within the ﬁnite gas cell. In the case of 68 Cu,
we estimated a stopping eﬃciency of about 10% by
LISE calculation, when the gas cell pressure is set at
one atmosphere of argon gas. When the high energy
RI-beams enter the gas cell, gas ionization occurs by
the beam itself. These ions comprise of mainly argon ions, and impurity ions included in the gas. We
detected these ions in the high-vacuum region, after
the ions were extracted from the gas cell and transported to the ion detector via SPIG and QMS in thediﬀerential pumping region. Figure 1 shows the ionintensity around mass 68 (a.m.u) when the degrader
thickness was varied (circle points scaled by the left
vertical axis). We remark that the behavior of thision signal is consistent with the calculated estimationfrom the stopping eﬃciency (square points scaled by
the right vertical axis). We conﬁrmed that the numberof ions produced by RI-beams is maximum, when thestopping eﬃciency is maximum.
As we could not ﬁnd the photo-ionized radioacRIKEN Nishina Center
High Energy Accelerator Research Organization (KEK)
Department of Physics, University of JyvaskylaFaculty of Engineering, Nagoya University
Japan Atomic Energy Agency
Department of Physics, Sophia University
Department of Physics,New Mexico State University

photo-ionized ionsAutoionizing state

500

Cu I

63

400

2'on2.dat'

287.9 nm

300
200
100
0
327.461

off-set ionsproduced by beam
327.47327.48327.49 nm
Ground state

The cyclotron beam dropped.
327.49327.5

first step wavelength (327.51)(nm)327.52

Fig. 2. The wavelength scan for the ﬁrst-step laser versus
the photo-ionized Cu ions, when the RI-beams enter thegas cell and Cu atoms are evaporated by a ﬁlament.

Reference1) T. Sonoda et al., AIP Conf. Proc. 1104, 132 (2009).

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