Ⅲ-3. Radiochemistry & Nuclear Chemistry
RIKEN
Accel. Prog. Rep. 56 (2023)

RIKEN Accel. Prog. Rep. 56 (2023)

Production cross sections of 198g Au in proton-induced reactions onnatPt†
G. Damdinsuren,∗1,∗2 M. Aikawa,∗1,∗2,∗3 Kh. Tegshjargal,∗4 N. Erdene,∗4 N. Ukon,∗5,∗2 and H. Haba∗2Gold-198 has two long-lived states, the ground stateAu (T1/2 = 2.6941 d, β − : 100%) and the excitedstate 198m Au (T1/2 = 2.272 d, IT: 100%). The groundstate 198g Au can be used in nuclear medicine, suchas brachytherapy1) and nanoparticles.2) The neutron
capture reaction on the monoisotopic element 197 Au
in a reactor can produce a considerable amount of198g
Au. However, this method yields only the low
speciﬁc activity of 198g Au owing to the diﬃculty encountered in separating 198g Au from the Au target.
The high speciﬁc activity 198g Au can be produced using charged-particle-induced reactions on platinum. In
this study, the proton-induced reactions on nat Pt targets were investigated. Moreover, the literature survey, only two experimental studies of cross sectionsof the nat Pt(p, x)198g Au reaction were found.3,4) The
literature data have large uncertainties and show discrepancy. Therefore, we conducted an experiment toprovide reliable cross sections of the nat Pt(p, x)198g Au
reaction. Thus, the results of this study were compared with the previous data and theoretical model
calculation in the TENDL-2019 library.5)
The stacked-foil activation technique and highresolution γ-ray spectrometry were used for cross section. Pure metallic foils of nat Pt (20-µm thick, 99.95%purity) and nat Ti (5-µm thick, 99.6% purity) were purchased from Nilaco Corp., Japan. The stacked target was composed of nat Pt and nat Ti foils. The nat Tifoils were used for the nat Ti(p, x)48 V monitor reaction
for assessment of the beam parameters and the targetthicknesses. Size and weight of the original foils weremeasured and the average foil thicknesses were derived. The derived average thicknesses of the nat Pt andnatTi foils were 39.2, and 2.24 mg/cm2 , respectively.
Both original foils were cut into a size of 10 × 10 mm.
Twenty-ﬁve sets of Pt-Pt-Ti-Ti foils were stacked in atarget holder served as a Faraday cup.
The stacked target was irradiated with a protonbeam. The irradiation lasted for 30 min. The primarybeam energy measured by the time-of-ﬂight method6)
was 30.1 ± 0.1 MeV. Consequently, the beam energy ateach foil was calculated using stopping powers derived

from the SRIM code.7) The average beam intensity was
101 nA, which was derived from irradiation period andcharge collected by the Faraday cup.
γ rays emitted from irradiated foils were measured by a high-resolution HPGe detector (ORTECGEM-25185-P) and analyzed using dedicated software(SEIKO EG&G Gamma Studio). Only the second
foil of the same element pairs was measured because
products recoiled from the second foil were assumed
to be compensated from the ﬁrst foil. The dead timethroughout the measurement was less than 4.7%.
Cross sections of the nat Ti(p, x)48 V monitor reaction were derived using the γ line at 983.5 keV (Iγ =99.98%) from the decay of 48 V (T1/2 = 15.9735 d). The
derived cross sections were consistent with the IAEArecommended values.8) Thus, the measured beam parameters and target thicknesses were adopted without
corrections for deduction of cross sections.
The cross sections of the nat Pt(p, x)198g Au reaction
were determined using the measurement of the γ line
at 411.80205 keV (Iγ = 95.62%) from the decay of198g
Au. The measurement was performed following
a cooling time of 13 d. The possible contribution
through decay of 198m Au (T1/2 = 2.272 d, IT: 100%)
was negligibly small because intense γ lines of 198m Au
could not be found in any spectra. Figure 1 shows thederived cross sections in comparison with the previous
experimental data3,4) and TENDL-2019 values.3) The
excitation function exhibited a smooth curve and wasconsistent with previous experimental data within theuncertainty; although certain data points of Tárkányiet al.3) were deviated. The peak amplitude and position of the TENDL-2019 values were slightly diﬀerent from the experimental cross sections although thetrend was similar.

198g

∗1∗2
∗3
∗4∗5Condensed from the article in Appl. Radiat. Isot. 192,110621 (2023)
Graduate School of Biomedical Science and Engineering,
Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
School of Engineering and Applied Sciences, National University of Mongolia
Advanced Clinical Research Center, Fukushima MedicalUniversitynatPt(p,x)198gAu

8Cross section [mb]†10- 183 -Tarkanyi (2004)
Showaimy (2019)TENDL-2019
This work

6420051015202530

Energy [MeV]Fig. 1. Excitation function of the nat Pt(p, x)198g Au reaction.

Ⅲ-3. Radiochemistry & Nuclear ChemistryRIKEN Accel. Prog. Rep. 56 (2023)

G. Damdinsuren was granted a scholarship by theM-JEED project (Mongolian-Japan Engineering Education Development Program, J11B16). This work
was partially supported by JSPS KAKENHI Grant No.
22H04961.
References
1) M. Konishi et al., J. Radiat. Res. 62, 871 (2021).
2) R. Chakravarty et al., Nucl. Med. Biol. 72, 1 (2019).
3) F. Tárkányi et al., Radiochim. Acta 92, 223 (2004).
4) H. Showaimy et al., Radiat. Phys. Chem. 157, 97(2019).
5) A. J. Koning et al., Nucl. Data Sheets 155, 1 (2019).
6) T. Watanabe et al., Proc. 5th Int. Part. Accel. Conf.
(IPAC 2014), (2014), p.3566.
7) J. F. Ziegler et al., Nucl. Instrum. Methods Phys. Res.
B 268, 1818 (2010).
8) F. Tárkányi et al., IAEA-TECDOC-1211 (2007).

2- 184 -