Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 56 (2023)
RIKEN
Accel. Prog. Rep. 56 (2023)

Activation cross sections of α-particle-induced reactions on nat Ta
S. Takács,∗1,∗2 F. Ditrói,∗1,∗2 Z. Szücs,∗1,∗2 M. Aikawa,∗2,∗3,∗4 G. Damdinsuren,∗2,∗4 H. Haba,∗2 andS. Ebata∗2,∗5∗1
∗2
∗3
∗4
∗5

Institute for Nuclear Research (ATOMKI)
RIKEN Nishina Center
Faculty of Science, Hokkaido University
Graduate School of Biomedical Science and Engineering,
Hokkaido University
Graduate School of Science and Engineering, Saitama University- 178 -pairs, as well as of the Ti monitor foils were measured by a high-resolution HPGe detector (ORTECGEM-25185-P) and analyzed using dedicated software(SEIKO EG&G Gamma Studio and Genie2000). The
spectra of each foil were measured several times to follow the decay of the reaction products. To maintaina low dead time the detector to foil distance was adjusted.
The cross-sections of the nat Ti(α, x)51 Cr monitor reaction were derived using the γ-line at 320.08 keV (Iγ= 9.910%) from the decay of 51 Cr (T1/2 = 27.7025d) and were compared with the recommended values of IAEA.4) Based on the comparison, the incident
beam energy was increased by 0.13% to 50.6 MeV,and thickness of the nat Ta foil was reduced by 0.12%
to 14.36 mg/cm2 . Moreover, owing the escaping secondary electrons, the beam intensity was reduced by
3% to 197.2 nA. With these adopted changes, goodagreement was reached with the recommended values.
Activation cross-sections can be deduced for several
Re, W, Ta, Hf, and Lu reaction products. A preliminary result cross-section for the nat Ta(α, x)182g Re reaction is presented in Fig. 1 together with the previous experimental data and the TENDL-2021 values.1)
Data were assessed using the γ-line at 1427.3 keV (Iγ= 9.8%) emitted following the decay of 182g Re. Measurements were performed after a cooling time of 48
h. This gamma line can be considered as interference
free, because only decay of possible co-produced 176 Ta
may contribute above 38 MeV with a negligible, twoorders of magnitude lower intensity. The earlier experimental data were consistent in terms of position of themaximum; however, certain diﬀerences exist in the am1500
nat

182g

Ta(,x)Re

This work
Scott 1968
Hermes 1974
Ismail 1988
Singh 1994
Tárkányi 2003
TENDL-2021

1200

Cross section (mb)

Tantalum is a frequently used material in accelerator technology exploiting its proper physical characteristics. However, by irradiating it with energetic alphaparticles several longlived radionuclides are produced.
To estimate the possible activity produced during anirradiation, knowledge of the excitation functions of
the possible reactions is required. In a literature survey, several experimental studies were found reporting
data on diﬀerent reactions. As signiﬁcant diﬀerence
exists in the peak position and amplitude among thediﬀerent datasets, we decided to perform an experiment to investigate the nat Ta(α, x) reactions and todeduce more reliable cross-sections data of these reactions. Furthermore, the obtained results were compared with theoretical model prediction available inTENDL-2021 data library.1)
The experiment was performed at the AVF cyclotronof RIKEN RI Beam Factory employing the stackedfoil target, activation method and high-resolution γray spectrometry. The target comprised pure metallic
foils of nat Ta (nominal thickness 9 µm, 99.99% purity,from Goodfellow, UK) and nat Ti (nominal thickness
5 µm, 99.6% from Nilaco Co., Japan). The nat Ti
foils served as catcher foils to stop and collect therecoiled reaction products and also as monitor foils
for the nat Ti(α, x)51 Cr monitor reaction. The average foil thickness was determined from the measured
lateral size and weight of the original foils. The derived thicknesses of nat Ta and nat Ti foils were 14.37and 2.24 mg/cm2 , respectively. Subsequently, the original foils were cut into a size of 10×10 mm and stacked
into a target holder served as a Faraday cup to measure the incident beam intensity. Every Ta foil was
set together with a Ti catcher foil. The other Ti foils
were inserted into the stack at certain positions formonitoring, to obtain maximum information on thebeam parameters and the energy loss of the beam in
the target stack. The stacked target was irradiatedwith a 50.5 ± 0.2 MeV α-particle beam for 1 hour.
The primary beam energy was measured employing thetime-of-ﬂight method.2) Energy degradation in the target was calculated using stopping power data derived
from the SRIM code.3) The average beam intensity
measured on the Faraday cup was 203 nA.
The γ-ray spectra of the Ta and its Ti catcher foil

900600300

0203040Particle energy (MEV)

50Fig. 1. Experimental cross-sections of the nat Ta(α, x)182g Re
reaction in comparison with TENDL-2021 values.

Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 56 (2023)

plitude. The TENDL-2021 values disagreed with theexperimental data both in peak position and in amplitude. Preliminary results for the activation crosssections have already been deduced for several reactions; however, owing to the long half lives of several reaction products, the γ-ray spectrometry measurements
are still required and thus continued. Final results areexpected in the second half of the year 2023.
References
1) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
2) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC 2014), (2014), p. 3566.
3) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
4) A. Hermanne et al., Nucl. Data Sheets 148, 338 (2018).

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