Study of proton- and deuteron-induced reactions on the long-lived fissionproduct 93Zr at 30 MeV/u in inverse kinematics

K. Iribe, M. Dozonoa, N. Imaia, S. Michimasaa, T. Sumikamab, N. Chigab, S. Otaa, O. Beliuskinaa,

S. Hayakawaa, C. Iwamotoa, S. Kawasec, K. Kawataa, N. Kitamuraa, S. Masuokaa, K. Nakanoc,

P. Schrocka, D. Suzukib, R. Tsunodaa, K. Wimmerd, D. S. Ahnb, N. Fukudab, E. Ideguchie,

K. Kusakab, H. Mikif, H. Miyatakeg, D. Nagaeb, M. Nakanoh, S. Ohmikab, M. Ohtakeb, H. Otsub,

H. J. Onge, S. Satoh, H. Shimizua, Y. Shimizub, H. Sakuraib, X. Sunb, H. Suzukib, M. Takakia,

H. Takedab, S. Takeuchif, T. Teranishi, H. Wangb, Y. Watanabec, Y. X. Watanabeg, H. Yamadaf,

H. Yamaguchia, R. Yanagiharae, L. Yanga, Y. Yanagisawab, K. Yoshidab, and S. Shimouraa

Department of Physics, Kyushu UniversityaCenter for Nuclear Study, the University of Tokyo

bRIKEN Nishina CentercDepartment of Advanced Energy Engineering Science, Kyushu University

dDepartment of Physics, the University of TokyoeResearch Center for Nuclear Physics, Osaka University

fDepartment of Physics, Tokyo Institute of TechnologygWNSC, IPNS, KEK

hDepartment of Physics, Rikkyo University

The nuclear transmutation [1] of long-lived fission prod-

ucts (LLFPs), which are produced in nuclear reactors, is one

of the candidate techniques for the reduction and/or reuse

of LLFPs. To design optimum pathways of the transmu-

tation process, several nuclear reactions have been studied

by using LLFPs as secondary beams. The studies indicate

that proton- and/or deuteron-induced spallation reactions at

intermediate energy (100−200 MeV/u) are sufficiently ef-fective for the LLFP transmutation [2–4].

Measurements at lower reaction energies for both proton-

and deuteron-induced reactions would be highly desirable

to design an accelerator-driven transmutation system, be-

cause proton and deuteron beams lose their energies in the

waste materials. For this purpose, we performed an experi-

ment of proton- and deuteron-induced reactions on 107Pdand 93Zr at 20 − 30 MeV/u at RIKEN RI Beam Fac-tory (RIBF). The inverse kinematics technique was adopted

in the present work: radioactive isotope (RI) beams of107Pd and 93Zr were used and proton/deuteron-induced re-actions were conducted using proton and deuteron targets.

The technique allows us to identify unambiguously reac-

tion products for residue production cross section measure-

ments. In addition, the technique avoids the difficulties as-

sociated with using a highly radioactive target. The new

beamline OEDO [5] was employed to produce low-energy

LLFP beams. This was the first physics experiment with

OEDO. In this report, the current status of the analysis on93Zr data is described. The status of the 107Pd data analysisis reported by Dozono et al. [6].

The experimental setup is shown in Fig. 1. A secondary

beam was produced by the in-flight fission of a 238U pri-mary beam at 345 MeV/u on a 5-mm-thick 9Be target lo-cated at the object point F0 of the BigRIPS fragment sep-

Figure 1. Schematic of the experimental setup.

arator. The beam was selected and purified at the focus

F1 by placing an aluminum wedge and setting a momen-

tum slit to ±0.15%. Figure 2 shows the mass-to-chargeratio A/Q distribution for the beam, which was deducedfrom the time-of-flight (TOF) between F3 and F5 measured

with CVD diamond detectors [7]. The A/Q resolution wasσ(A/Q) = 3 × 10−3. We can see that the beam containsonly N = 53 isotones and the 93Zr particle is clearly sepa-rated from other particles. The purity of 93Zr was 33.9%.

The beam was further decelerated at F5 by using an alu-

minum energy degrader, and focused employing the OEDO

device [5], which consists of a radio-frequency deflec-

tor and two superconducting triplet quadrupole magnets.

The beam energy was measured with the TOF between F5

and FE12, and its image was measured with parallel-plate

avalanche counters (PPACs) [8] located at FE12. The re-

sulting 93Zr beam had an energy of 32 MeV/u and a spatialspread of 45 mm (FWHM) at the secondary target position

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A/Q for secondary beam2.1 2.15 2.2 2.25 2.3 2.35 2.4 2.45 2.5 2.55

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Figure 2. mass-to-charge ratio A/Q distribution for secondary

beam.

S0. The typical beam intensity was 104 pps.H2 and D2 gas targets were prepared at S0 to induce the

secondary reactions. The targets were operated at a temper-

ature of 40 K and a pressure of 2.2 atm, resulting in a thick-ness of 7.5(15) mg/cm

2for H2 (D2). The gas cell windows

were made of 10-µm-thick Harvar foil. Empty-target mea-surements were also carried out to obtain the contributions

from both the Harvar foils and the PPACs at FE12.

Reaction residues were momentum analyzed and iden-

tified by the first half (QQD; which consists of two

quadrupole magnets and one dipole magnet) of the

SHARAQ spectrometer [9, 10]. The full momentum accep-

tance is 8% and the angular acceptance is ±30 mrad forboth horizontal and vertical directions. The particles were

detected by two PPACs and an ionization chamber [11] lo-

cated at the focal plane S1. The magnetic rigidity (Bρ) andTOF, which were deduced from the position and timing in-

formation of the PPACs at S0 and S1, provided the mass-

to-charge ratio A/Q. The ionization chamber measured theBragg curve along the beam axis, which helped determine

the atomic number Z and mass number A. In order to covera broad range of reaction products, several different Bρ set-tings were applied. The analysis of the detector system and

the particle identification is now in progress.

This work was funded by the ImPACT Program of the

Council for Science, Technology and Innovation (Cabinet

Office, Government of Japan).

References

[1] Implication of Partitioning and Transmutation in Ra-

dioactive Waste Management, IAEA Technical Reports

Series No. 435, 2004.

[2] H. Wang et al., Phys. Lett. B754 (2016) 104.

[3] H. Wang et al., Prog. Theor. Exp. Phys. 2017 (2017)

021D01.

[4] S. Kawase et al., Prog. Theor. Exp. Phys. 2017 (2017)

093D03.

[5] S. Michimasa et al., in this report.

[6] M. Dozono et al., in this report.

[7] S. Michimasa et al., Nucl. Instrum. Methods Phys. Res.

B 317 (2013) 710.

[8] H. Kumagai et al., Nucl. Instrum. Methods Phys. Res.

B 317 (2013) 717.

[9] T. Uesaka et al., Prog. Theor. Exp. Phys. 2012 (2012)

03C007.

[10]M. Dozono et al., Nucl. Instrum. Methods Phys. Res. A

830 (2016) 233.

[11]N. Chiga et al., RIKEN Accel. Prog. Rep. 50 (2017)

164.

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