Ⅱ-1. Nuclear Physics
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

The result of electron scattering with Xe isotopes
at SCRIT electron scattering facility
H. Wauke,∗1 D. Abe,∗1 Y. Abe,∗2 A. Enokizono,∗2 R. Danjo,∗1 T. Goke,∗1 Y. Honda,∗1,∗2 Y. Ishikura,∗1Y. Itou,∗3 K. Kurita,∗4 H. Ohnishi,∗2 C. Legris,∗1 Y. Maehara,∗3 Y. Nagano,∗5 R. Obara,∗1 R. Ogawara,∗3T. Suda,∗1,∗2 K. Tsukada,∗2,∗3 M. Watanabe,∗2 M. Wakasugi,∗2,∗3 and S. Yoshida∗3Self-Conﬁning Radioactive Ion Target (SCRIT) electron scattering facility1) was constructed to perform
electron scattering experiments for short-lived unstable nuclei. SCRIT is a unique technique to achieve aluminosity of 1027 cm−2 s−1 via the trapping of a few
target ion that is, 108 particles/pulse, along the electronbeam.
We have started a series of measurements of isotope(Z = 50) and isotone (N = 82) dependence of nuclear charge density distribution. These studies use thenuclei of Xe isotopes (138, 136, 134, 132, 130, 128, 126, 124 Xe)
and N = 82 isotones (138 Ba,2) 137 Cs,3) 136 Xe, 132 Sn)
including the 132 Sn and 137 Cs, unstable nuclei. TheXe isotope has the second most stable nuclei after Sn;
however, no electron scattering data is available, except
for 132 Xe,4) which was measured at the SCRIT facility.
These isotope and isotone dependencies should provide
invaluable information for theoretical development.5,6)
In 2022 July, we conducted the electron scattering experiment using 136, 134, 132, 130 Xe targets. The Xe target
was ionized with FEBIAD-type ion source by injecting
natural Xe gas directly into the ionization chamber inside the ERIS.7) The ionized Xe was mass-separated bya bending magnet installed after ERIS. After coolingand stacking inside the FRAC,8) almost 108 of massspeciﬁc Xe ions/pules were transported to the SCRITsystem at a frequency of 1 Hz. Experiments with 136 Xe
were performed at both 150 and 250 MeV, whereas theexperiments with 134, 132, 130 Xe were only performed at150 MeV. Further, the beam current was 250 mA at
the beginning of the data acquisition and reduced to150 mA at the end. Figure 1 shows the yield distributions of 136 Xe with momentum transfer following acceptance corrections. The solid lines represent the calculated ones using the theoretical charge density distribution of 136 Xe5) using the phase shift calculation codeDREPHA.9) The total experimental time and averageluminosity of each experiment is presented in Table 1.
Average luminosities were measured by a luminositymonitor.
The 124 Xe, which is scheduled to be launched soon,
has a smaller abundance ratio than other Xe, thus, wehave upgraded ERIS and have already achieved a production rate similar to that of 136 Xe. From 2023, we
∗1
∗2
∗3
∗4
∗5

Research Center for Electron Photon Science, Tohoku University
RIKEN Nishina Center
Institute for Chemical Research, Kyoto University
Department of Physics, Rikkyo University
Faculty of Science, Yamagata University- 19 -Fig. 1. Yield distributions of 136 Xe with momentum transfer following acceptance corrections. Filled and opened
circles indicate preliminary results from this study. The
solid lines are the phase-shift calculated values obtainedusing a theoretically calculated charge-density distribution of 136 Xe.5)

Table 1. Experimental situation.

Nuclei

136

Xe
Xe
134
Xe
132
Xe
130
Xe
total
136

BeamEnergy[MeV]

Total Exp.
time [s]Lumi. ave[× 1027cm−2 s−1 ]

150
250
150
150
150

1.94×105
4.28×105
1.18×105
0.90×105
1.29×105
9.59×105

1.55
2.08
1.66
1.69
1.33

will conduct experiments on the remaining Xe and proceed with further analysis.
References
1) M. Wakasugi et al., Phys. Rev. Lett. 100, 164801 (2008).
2) K. Tsukada et al., RIKEN Accel. Prog. Rep. 55, 24(2021).
3) K. Tsukada et al., Phy. Rev. Lett. 131, 092502 (2023)
4) K. Tsukada et al., Phys. Rev. Lett. 118, 262501 (2017).
5) T. Liang et al., Phys. Rev. C 98, 044310 (2018).
6) X. Roca-Maza et al., Phys. Rev. C 87, 014304 (2013).
7) T. Ohnishi et al., Nucl. Instrum. Methods Phys. Res. B
317, 357 (2013).
8) M. Wakasugi et al., Rev. Sci. Instrum. 89, 095107 (2018).
9) B. Drepher, A phase-shift calculation code for elastic electron scattering (private communication withJ. Friedrich).