III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Measurement of production cross sections of 175 Hf in the nat Lu(p, x) andnatLu(d, x) reactions
Y. Komori,∗1 H. Haba,∗1 M. Aikawa,∗2 M. Saito,∗2 S. Takács,∗3 and F. Ditrói∗3200

Cross section [mb]natLu(p,x)175Hf

150

175Lu(p,n)175Hf

100
5000

This work (ATOMKI)
This work (RIKEN)
Bennett (2012)TENDL-2019

176Lu(p,2n)175Hf

51015
Proton energy [MeV]

20Fig. 1. Excitation function for the nat Lu(p, x)175 Hf reaction.
∗1
∗2
∗3

RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido University
Institute for Nuclear Research, ATOMKI

800

Cross section [mb]The chemical characterization of superheavy elements(SHEs) with atomic number ≤104 is one of the most important and challenging subjects in the ﬁeld of nuclear
chemistry. Prior to chemistry experiments on SHEs, it
is important to ﬁnd suitable chemical systems and experimental conditions using the no-carrier-added radiotracers of their lighter homologues. The long-lived Hfisotope, 175 Hf (T1/2 = 70 d), is useful for basic studies
on element 104, Rf. The 175 Hf isotope can be produced
in proton- and deuteron-induced reactions on nat Lu. Foreﬃcient and quantitative production of this isotope, excitation functions are necessary to know. However, data
are available only for the nat Lu(p, x)175 Hf reaction1) andnot for the nat Lu(d, x)175 Hf. In this work, we measured
the excitation functions for these reactions at RIKEN
and the Institute for Nuclear Research (ATOMKI).
The excitation functions were measured using thestacked foil technique. At RIKEN, a target stackthat consisted of 9 sets of a nat Lu foil (99% purity, 27.1 mg/cm2 thickness), a nat Ta foil (99.95%,17.0 mg/cm2 ), and 2 nat Ti foils (≤99.6%, 4.4 mg/cm2 )was irradiated with a 14-MeV proton beam supplied fromthe RIKEN AVF cyclotron. Another target stack thatconsisted of 17 sets of a nat Lu foil (99%, 27.6 mg/cm2 ),a nat Ta foil (99.95%, 17.1 mg/cm2 ), and a nat Ti foil(≤99.6%, 4.4 mg/cm2 ) was irradiated with a 24-MeV
deuteron beam. At ATOMKI, a target stack that consisted of 17 sets of a nat Lu foil (99%, 20.7 mg/cm2 ),a nat Ta foil (99.95%, 17.0 mg/cm2 ), and 2 nat Ti foils(≤99.6%, 5.4 mg/cm2 ) was irradiated with an 18-MeV
proton beam from the MGC-20E cyclotron. Anothertarget stack that consisted of 8 sets of a nat Lu foil (99%,20.7 mg/cm2 ) and a nat Ti foil (≤99.6%, 4.4 mg/cm2 )was irradiated with a 10-MeV deuteron beam. The nat Tafoils were used to determine the excitation functions fornatLu(d,x)175Hf

600

175Lu(d,2n)175Hf

400
20000

This work (RIKEN)This work (ATOMKI)TENDL-2019

176Lu(d,3n)175Hf

510152025
Deuteron energy [MeV]

30Fig. 2. Excitation function for the nat Lu(d, x)175 Hf reaction.

the nat Ta(p, x) and nat Ta(d, x) reactions. The nat Ti foils
were used to conﬁrm the beam energy and intensity
based on the monitor reactions of nat Ti(p, x)48 V andnatTi(d, x)48 V. All these target stacks were irradiatedwith 170–220 nA beam currents for 2 h. After the irradiation, each foil was subjected to γ-ray spectrometrywith Ge detectors.
The excitation functions were measured for thenatnatLu(p, x)173, 175 HfandLu(d, x)173, 175 Hf,173, 174m, 174g, 176m, 177m, 177g
Lu reactions. Figures 1 and2 show the excitation functions for the nat Lu(p, x)175 Hf
and nat Lu(d, x)175 Hf reactions, respectively. For both reactions, our data measured at RIKEN and ATOMKI areconsistent with each other. Data of the nat Lu(p, x)175 Hf
reaction are also consistent with the data previously published by Bennet et al.1) Theoretically predicted crosssections for the nat Lu(p, x)175 Hf reaction in the TENDL2019 library2) are lower than the experimental ones at
9–14 MeV. The peak energy of the excitation function inthe TENDL-2019 is approximately 1.5 MeV lower thanthe experimental one. For the nat Lu(d, x)175 Hf reaction, TENDL-2019 slightly overestimates the cross sections at 10–14 MeV and above 15 MeV. The peak energy in TENDL-2019 is approximately 1 MeV lower thanthe experimental one. Physical thick-target yields of175
Hf were deduced from the measured excitation functions. The yield of 175 Hf in the nat Lu(p, x)175 Hf reaction is 0.47 MBq/µA · h in the energy range of 4.2–
17.2 MeV, while that in the nat Lu(d, x)175 Hf reaction is2.0 MBq/µA · h in the range of 5.7–24.0 MeV. The yieldof the nat Lu(d, x)175 Hf reaction is 4 times larger thanthat of the nat Lu(p, x)175 Hf reaction in the energy ranges
investigated in this work.
References

1) M. E. Bennet et al., Nucl. Instrum. Methods Phys. Res.
B 276, 62 (2012).
2) A. J. Koning, D. Rochman, Nucl. Data Sheets 113, 2841
(2012).

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