III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Cross sections of alpha-particle-induced reactions on nat Ni: Productionof 67 Cu†
S. Takács,∗1 M. Aikawa,∗2,∗3,∗4 H. Haba,∗3 Y. Komori,∗3 F. Ditrói,∗1 Z. Szücs,∗1 M. Saito,∗2,∗3 T. Murata,∗2,∗3M. Sakaguchi,∗2,∗3 and N. Ukon∗5,∗3Cu is considered one of the most promising radioisotopes in targeted radio-immunotherapy. It is aβ − -emitter with a mean β − energy (Eβ− = 141 keV)that allows treating tumors of size up to approximately
4 mm. Its decay is followed by the emission of lowenergy gamma rays suitable for SPECT imaging. Its
half-life (T1/2 = 61.83 h) is optimal for human applications. Among the charged-particle-induced production
routes, the 64 Ni(α, p)67 Cu reaction requires much lessenriched (expensive) target material for providing a comparable amount of 67 Cu activity as compared to proton
or deuteron production routes. The available literature
data are very diﬀerent from each other in terms of bothshape and amplitude, and only one experiment provided
cross-section data above 25 MeV; therefore, we decided
to investigate this production route up to 51 MeV.
Experiments were performed at the RIKEN AVF cyclotron. The stacked-foil activation technique and highresolution γ-ray spectrometry were applied. Pure metallic foils of nat Ni and nat Ti from Nilaco Corp., Japan
with an average thickness of 5 µm were used. The foils
were paired (Ni-Ni, or Ti-Ti) in the stack to handle
the recoil eﬀect. Four irradiations were performed using
51.04, 49.42, 40.94, and 26.57 MeV alpha-particle beams.
The incident beam energy was measured by the time-ofﬂight method.1) The energy loss of the alpha particles
was calculated using the semi-empirical formula of Andersen and Ziegler.2) The average beam intensity measured using a Faraday cup was cross checked with thenatTi(α, x)51 Cr monitor reaction.3) After a small correction of the measured beam intensities, the re-measured
cross-sections for the nat Ti(α, x)51 Cr monitor reaction
agreed perfectly with their recommended value.3) Several
series of γ-ray spectra were recorded for each irradiatedfoil by using a high-resolution HPGe detector-based γspectrometer without chemical separation for increasing
cooling times to follow the decay of the reaction products. Q-values and decay data were taken from the Qvalue calculator4) and NuDat 2.7 database5) of National
Nuclear Data Center, respectively. On the nat Ni target,
67
Cu can be produced only in the 64 Ni(α, p)67 Cu reaction with an alpha-particle beam. The threshold energyof this reaction is Ethr = 4.93 MeV.
The deduced isotopic cross sections for the64
Ni(α, p)67 Cu reaction were normalized to 100% 64 Ni

67†∗1∗2∗3∗4∗5Condensed from the article in Nucl. Instrum. Methods Phys.
Res. B 479, 125 (2020)
Institute for Nuclear Research, ATOMKI
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Advanced Clinical Research Center, Fukushima Med. Univ.

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(QHUJ\ 0H9Fig. 1. Excitation function of the 64 Ni(α, p)67 Cu reaction incomparison with previously reported experimental data
and the result of the model calculation taken from theTENDL-2019 database.5)

isotopic abundance. Additionally, direct and/or cumulative “elemental” activation cross-sections were deduced
for the formation of 64, 61, 60 Cu, 63, 62 Zn, and 57, 56 Ni
radionuclides as possible radio-contaminants. The obtained experimental data were compared with the experimental data available in the literature and the resultsof the TALYS theoretical model calculation taken fromthe TENDL-20196) data library.
Thick target yields were calculated to estimate theexpected amount of 67 Cu and the possible radiocontamination level of the other co-produced copper radionuclides by using the spline-ﬁtted experimental datain the calculation. It was concluded that the production of 67 Cu is possible on a highly enriched 64 Ni target
for local use only. To reduce the amount of co-produced64Cu, the bombarding alpha-particle energy should bekept below 30 MeV. During a 24 h-long (30 MeV and30 µA) irradiation, the estimated end-of-bombardment(EOB) activity of 67 Cu is approximately 1 GBq, and the
expected activity of the co-produced 64 Cu is approximately 0.15%.
This work was conducted in the framework of a common research program between the JSPS and HAS (Contract No: FY2019-2020 and NKM-43/2019).
References

1) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC2014), (2014), p. 3566.
2) H. H. Andersen, J. F. Ziegler, Helium Stopping Powersand Ranges in all Elements (Pergamon, Oxford, 1997).
3) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
4) NNDC, Q-calc, https://www.nndc.bnl.gov/qcalc/ .
5) NNDC, NuDat 2.7 database, http://www.nndc.bnl.gov/
nudat2/ .
6) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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