III-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

Activation cross sections of alpha-particle-induced reactions on naturalcalcium
M. Aikawa,∗1,∗2 Y. Hanada,∗3,∗2 D. Ichinkhorloo,∗4,∗2 H. Haba,∗2 S. Takács,∗5 F. Ditrói,∗5 and Z. Szűcs∗5

∗1
∗2
∗3
∗4
∗5

Faculty of Science, Hokkaido University
RIKEN Nishina Center
Graduate School of Biomedical Science and Engineering,
Hokkaido UniversityNuclear Research Center, National University of Mongolia
Institute for Nuclear Research (ATOMKI)

6natCa(,x)47Sc5Cross section (mb)

We focused on the production of the therapeutic radionuclide 47 Sc (T1/2 = 3.3492 d) via alpha-particleinduced reactions on calcium. Owing to the relatively
small abundance of 46 Ca (0.004%) and 48 Ca (0.187%) in
natural calcium, the dominant route for 47 Sc productionis the reaction on 44 Ca (2.086%). Only one experimental study was found in a literature survey,1) and therefore, we performed an experiment to obtain the crosssections of the nat Ca(α, x)47 Sc reaction. The production cross sections of 46, 44m, 44g, 43 Sc and 47 Ca were alsodetermined.
The experiment was conducted with a 29-MeV alphaparticle beam at the RIKEN AVF cyclotron. Stackedfoil activation technique and high-resolution gamma-ray
spectrometry were used in the experiment. Calciumﬂuoride (CaF2 ) deposited on a high-purity 27 Al backing foil (99.999% purity, Goodfellow Co. Ltd., UK) wasused as the calcium target. In addition, two metallic
foils of nat Ti (99.5% purity) for the nat Ti(α, x)51 Cr monitor reaction and 27 Al (>99% purity) to catch recoiled
products were purchased from Nilaco Corp., Japan. The
measured average thicknesses of the 27 Al backing, 27 Al
catcher and nat Ti monitor foils were 2.57, 1.50 and2.30 mg/cm2 , respectively. The thickness of the CaF2layer was 0.135 mg/cm2 , as derived from the measured
deposited area and net weight of CaF2 . Thickness uncertainties were estimated to be 5% for the CaF2 layerand 1% for the other foils. All foils were cut into a size of
10 × 10 mm2 to ﬁt a target holder. Each calcium target
consisted of two CaF2 layers sandwiched with the 27 Al
backing foils. Twelve calcium targets and seven sets of
the nat Ti monitor and 27 Al catcher foils were stacked
together in the target holder.
The stacked target was irradiated for 30 min with analpha-particle beam. The measured average beam intensity and energy were 175 nA and 29.0 ± 0.2 MeV,respectively. The energy degradation in the stacked target was calculated using stopping powers obtained fromthe SRIM code.2)
The high-resolution gamma-ray spectrometry using ahigh-purity germanium detector was performed withoutchemical separation. The calcium targets were measured
ﬁve times with cooling times from 3.2 h to 77.0 d anddead times below 2.1%.
The derived cross sections of the nat Ti(α, x)51 Cr monitor reaction were compared with the IAEA recom-Levkovski (1991) (44Ca)TENDL-2019
This work

4
32
1
00

5

10

15

20

2530

Energy (MeV)

Fig. 1. Excitation function of the nat Ca(α, x)47 Sc reaction
in comparison with normalized data from the previous
study1) and TENDL-2019 values.4)

mended values.3) The comparison results indicated thatthe beam intensity and thicknesses of both 27 Al backing
and catcher foils were corrected within the uncertainties
by +5.6% and −1%, respectively. The measured thicknesses of the nat Ti monitor foil and the CaF2 layer wereadopted without any correction.
47
Sc can be produced directly from the 44 Ca(α, p)47 Sc
reaction and indirectly from the decay of the coproduced parents, 47 Ca and 47 K. The indirect contribution was negligible because the co-produced parents
can be formed only from the lower-abundant isotopes,
46
Ca and 48 Ca. The gamma line at 159.381 keV (Iγ =68.3%) from the 47 Sc decay was measured after coolingtimes of 1.2–2.8 d. The derived cross sections of thenatCa(α, x)47 Sc reaction are shown in Fig. 1 in comparison with the experimental data studied earlier3) andthe theoretical values provided in the TENDL-2019 library.4) The previous data of the 44 Ca(α, x)47 Sc reaction
are normalized to those using natural calcium targets.
The peak of the previous data shifts to the low-energy
region. The TENDL-2019 calculation largely overestimates the excitation function.
This work was supported by the Japan-Hungary Research Cooperative Program between JSPS and HUS,
Grant number JPJSBP120193808 and NKM-43/2019.
References
1) V. N. Levkovski, Cross Sections of Medium Mass Nuclide
Activation (A = 40–100 ) by medium energy protons andalpha particles (E = 10–50 MeV ) (Inter-Vesi, Moscow,USSR, 1991).
2) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res. B
268, 1818 (2010).
3) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).
4) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).

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