Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

Measurement of 77, 79 Se(d, p)78, 80 Se reactions asa surrogate for 79 Se(n, γ)80 Se reaction
N. Imai,∗1 M. Dozono,∗1 S. Michimasa,∗1 T. Sumikama,∗2 S. Ota,∗1 S. Hayakawa,∗1 K. Iribe,∗3 C. Iwamoto,∗1S. Kawase,∗4 K. Kawata,∗1,∗2 N. Kitamura,∗1 S. Masuoka,∗1 K. Nakano,∗4 P. Schrock,∗1 D. Suzuki,∗2R. Tsunoda,∗1 K. Wimmer,∗5 D.S. Ahn,∗2 O. Beliuskina,∗1 N. Chiga,∗2 N. Fukuda,∗2 E. Ideguchi,∗6K. Kusaka,∗2 H. Miki,∗7 H. Miyatake,∗8 D. Nagae,∗2 M. Nakano,∗9 S. Ohmika,∗2 M. Ohtake,∗2 H. Otsu,∗2H.J Ong,∗6 S. Sato,∗9 H. Shimizu,∗1 Y. Shimizu,∗2 H. Sakurai,∗2,∗5 X. Sun,∗2 H. Suzuki,∗2 M. Takaki,∗1H. Takeda,∗2 S. Takeuchi,∗7 T. Teranishi,∗3 Y. Watanabe,∗4 Y.X. Watanabe,∗8 H. Yamada,∗7 H. Yamaguchi,∗1L. Yang,∗1 R. Yanagihara,∗6 K. Yoshida,∗2 Y. Yanagisawa,∗2 and S. Shimoura∗1∗1∗2∗3∗4∗5∗6∗7∗8∗9Counts [arb.unit]

To design a facility for decommissioning the spent
fuel from nuclear power plants containing long-lived
ﬁssion products (LLFPs), more nuclear reaction datais needed. Within the ImPACT program, thus far
several nuclear reactions of LLFPs produced by BigRIPS impinging on nuclear and proton targets havebeen measured.1) Because of the longer mean free path,the transmutation with neutrons can be applied more
eﬃciently. However, since both the neutron and theLLFPs are unstable, the measurement of the neutroninduced cross section requires a neutron facility, in addition to enriched radioactive targets. Instead, the reaction cross-section can be determined in an indirect
way employing a surrogate reaction.
It is generally assumed that the (n, γ) cross section separates into two parts: the formation of thecompound state and it’s subsequent decay. The ﬁrst
term can be calculated using the optical model potentials with global parameters. On the other hand,
the theoretical estimates of the second process areuncertain,and need to be validated by experiments.2)
The present work aims to determine the γ emission
probability from unbound states of 80 Se by using the(d , p) reaction as a surrogate for the 79 Se(n, γ)80 Sereaction. The method will be tested by measuring
the 77 Se(d,p)78 Se reaction, which is the surrogate for77
Se(n, γ)78 Se, which was previously measured.4)
The 77,79 Se beams were produced using the 238 U
beam impinging on a 3-mm-thick 9 Be target. By using
this relatively thin primary target and a thick 15-mm
Al degrader at F1, a purity of approximately 40% wasachieved. Since the total intensity at F3 was approximately 1 MHz, beam particles were identiﬁed by thetime-of-ﬂight between F3 and F5 measured with diamond detectors alone. The beam energy was furtherdegraded at F5 using a 3.5-mm-thick Al degrader, re-77

60

Se

33+

77

50

4077

SeSe

32+

34+

30

20

100
2.2

78
2.25

Se

34+
2.3

78

Se

2.35

33+

78
2.4

Se

34+

2.45

2.5

A/QFig. 1. A/Q spectrum measured at S1 focal plane for theevents coincident with the protons detected with TiNA.

sulting in a ﬁnal value of 26 MeV/nucleon. The OEDOfacility3) was employed to reduce the spatial spread of
the beam, resulting in a beam spot of 30 mm FWHM
on the secondary target.
The beam from OEDO impinged on a CD2 target of
4 mg/cm2 to induce the one-nucleon transfer reaction.
The recoiled particles were identiﬁed by employing theSSD-CsI(Tl) array, TiNA,5) which covered 100 to 150◦in the laboratory frame. The excitation energies of thestate populated in 78 Se (80 Se) were determined fromthe measured four-momenta of the protons and thedirection of the incident beam.
The outgoing beam-like particles were identiﬁed
with the dE-E-Bρ method, shown in Fig. 1, using themomentum determined by the horizontal position at
the S1 focal plane. This will allow for a determinationof the γ-ray emission probability as a function of excitation energy based on the fraction of (N+1,Z) nuclei
to (N,Z) residues detected in coincidence with protons
in TiNA. Further analysis is ongoing.
The work was funded by ImPACT Program of Council for Science, Technology, and Innovation (CabinetOﬃce, Government of Japan).

Center for Nuclear Study, University of Tokyo
RIKEN Nishina CenterDepartment of Physics, Kyushu Univ.
Department of Advanced Energy Engineering Science,Kyushu Univ.
Department of Physics, Univ. of Tokyo
RCNP, Osaka University
Department of Physics, Tokyo Insititute of Technology
WNSC, IPNS, KEK
Department of Physics, Rikkyo University

References
1) H. Wang et al., Phys. Lett. B 754, 104 (2016).
2) J. E. Escher et al., Rev. Mod. Phys. 84, 353 (2012).
3) S. Michimasa et al., in this report.
4) S. Kawada, M. Igashira, T. Katabuchi, M. Mizumoto,J. Nucl. Sci. Tech. 47, 643 (2010).
5) P. Schrock et al., in this report.

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