Ⅱ-9. Instrumentation

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

Present operation status of ERIS at the SCRIT electron scattering
facility
T. Ohnishi,∗1 Y. Abe,∗1 D. Abe,∗2 R. Danjyo,∗2 A. Enokizono,∗1,∗3 T. Goke,∗2 M. Hara,∗1 Y. Honda,∗1,∗2T. Hori,∗1 S. Ichikawa,∗1 S. Iimura,∗1,∗3 Y. Ishikura,∗2 Y. Ito,∗4 K. Kurita,∗3 C. Legris,∗2 Y. Maehara,∗4Y. Nagano,∗5 R. Ogawara,∗1,∗4 R. Ohara,∗2 T. Suda,∗1,∗2 K. Tsukada,∗1,∗4 M. Wakasugi,∗1,∗4 M. Watanabe,∗1H. Wauke,∗1,∗2 and S. Yoshida∗4

∗1
∗2
∗3
∗4
∗5

RIKEN Nishina Center
Research Center for Electron-Photon Science, Tohoku University
Department of Physics, Rikkyo University
Institute of Chemical Research, Kyoto University
Department of Physics, Yamagata University- 88 -of the FEBIAD type ion source at ERIS are reportedin Ref. 5). The overall eﬃciency, estimated as 5%, waslower than the previous result of 14%.5) This is because
no magnetic ﬁeld of the FEBIAD type ion source wasused to reduce the ion-beam emittance. With the optimized magnetic ﬁeld, the overall eﬃciency became thesame as the previous value. Finally, stable xenon ion
beams over a wide mass range, from 124 Xe to 136 Xe,were supplied. For the supply of 124 Xe and 126 Xe, thegas supply volume was increased because the existing
supply volume was insuﬃcient owing to their low natural abundance ratio. An ion beam current, almost 1 nA,
was achieved in case of 124 Xe, while maintaining thepressure inside the ion source in the order of 10−4 Pawith careful control of the gas supply. Figure 1 shows
the mass spectrum. 124 Xe and 126 Xe were clearly separated and measured. After cooling and stacking inside
FRAC, 108 ions/pulse of each Xe isotopes, including
124, 126Xe, were transported to the SCRIT system.
0.6
128

0.5

Voltage [V]The electron-beam-driven radioactive isotope separator for SCRIT (ERIS)1) at the SCRIT electron scattering facility2) is an online isotope-separator system used
to produce low-energy radioactive isotope (RI) beams
using the photoﬁssion of uranium. The RI beam production at ERIS began in 2013 and has been vigorously
developed. This year, two full-scale ion beam operations were conducted for physics experiments. The ﬁrst
was the 137 Cs ion-beam production for electron scattering experiment with RI. The second was the ion beam
supply of Xe isotopes for the systematic study of nuclear structure using electron scattering. In this paper,
we report details of both these operations.
The 137 Cs ion-beam production was performed in thespring of 2022. 137 Cs nuclei were produced via photoﬁssion of uranium, and they were ionized and extractedwith the surface ionization technique. Details of the137
Cs beam production are reported in Ref. 3). In thisoperation, self-made 48 uranium carbide disks, withthickness and diameter of 0.8 and 18 mm, respectively,
were used as production targets and the total amountof uranium was approximately 28 g. A 150-MeV electron beam with beam power of approximately 15 W
irradiated to the production target heated to around2000◦ C using the resistive heating method. Ionized RIs
were stacked in the ionization chamber for 25 ms, extracted as a pulsed beam by the exit grid of the ionization chamber, and then accelerated to 6 keV. Following mass selection, the pulsed 137 Cs ion beam was
injected into a RFQ cooler and buncher, FRAC.4) Approximately 107 ions/pulse for 137 Cs, accumulated for
4 s inside FRAC, were transported to the SCRIT system for the electron scattering experiment. During themeasurement, which was approximately one month operation, the ERIS operation was very stable. Although
there were concerns regarding the lifetime of the production target, the amount of produced RI remained
almost constant because of the good quality of the target. It is important to establish a target-production
method that guarantees the quality.
The ion beams of Xe isotopes have been supplied
since this summver. The FEBIAD type ion source wasused for the ionization of Xe, and natural Xe gas wasinjected directly into the ionization chamber. Details

Xe

0.4
0.3
0.2
0.1
057.5

124

Xe58126

Xe

58.5

59

59.5

I [A]Fig. 1. Mass spectrum around 124 Xe and 126 Xe plotted withthe current value of the analyzing magnet.

Currently, the experiments with Xe isotopes are stillongoing. As the next research objective, further development of ERIS is planned to accommodate the upgrade of the electron beam power to a few kW. For
example, the radiation shield and the remote handlingsystem are being considered for updates.
References
1) T. Ohnishi et al., Nucl. Instrum. Methods Phys. Res. B
317, 357 (2013).
2) M. Wakasugi et al., Nucl. Instrum. Methods Phys. Res.
B 317, 668 (2013).
3) Y. Abe et al., RIKEN Accel. Prog. Rep. 55, S19 (2022).
4) M. Wakasugi et al., Rev. Sci. Instrum. 89, 095107 (2018).
5) T. Ohnishi et al., Nucl. Instrum. Methods Phys. Res. B
463, 290 (2020).