Ⅲ-3. Radiochemistry & Nuclear Chemistry

RIKEN Accel. Prog. Rep. 52 (2019)

Cross-section measurement of α-induced reactions on nat Er for 169 Ybproduction
M. Saito,∗1,∗2 M. Aikawa,∗1,∗2,∗3 M. Sakaguchi,∗4,∗2 N. Ukon,∗5,∗2 Y. Komori,∗2 and H. Haba∗2

∗1
∗2
∗3
∗4
∗5

Graduate School of Biomedical Science and engineering,Hokkaido University
RIKEN Nishina Center
Faculty of Science, Hokkaido University
School of Science, Hokkaido University
Advanced Clinical Research Center, Fukushima MedicalUniversity- 191 -600natThis work
B. Kiraly (2008)
A. A. Sonzogni (1992)
A. Archenti (1985)
Y. Homma (1980)
TENDL-2017

169Er(α,x)

Yb

500
Cross section (mb)Radioisotopes (RIs) are widely used in the medicalﬁelds such as therapy and diagnosis. To develop such
medical treatments, the candidates of medical RIs need
to be studied further. Ytterbium-169 (169 Yb) is a typeof RI that has a half-life of 32.018 days and emits Auger
electrons, X and γ rays. The Auger electrons and Xrays can be used in brachytherapy as an alternative
RI to 125 I and 192 Ir.1) The γ rays at 177.21 keV (Iγ= 22.28%) and 197.96 keV (Iγ = 35.93%) provide theopportunity for diagnosis.2) Therefore, owing to thesecharacteristics, 169 Yb can be used in theranostics.
Various reactions can be used to produce 169 Yb suchas the neutron-capture reaction on 168 Yb and chargedparticle induced reactions on 169 Tm and nat Er. Amongthese, the best production route has not been determined yet. Therefore, we performed systematic studies on the charged-particle induced reactions to produce 169 Yb such as deuteron- and alpha-induced reactions on 169 Tm and alpha-induced reactions on nat Er.
In this report, we focus on the α-induced reaction onnatEr. The cross-sections for these reactions have already been experimentaly measured and reported.3–6)
However, these cross-sections are diﬀerent. Therefore,
we again measured them to ensure a higher accuracy.
The experiment was performed at the AVF cyclotronof the RIKEN RI Beam Factory using the activationstacked-foil method. Metallic foils of nat Er (purity:99%, Goodfellow Co., Ltd., UK) and nat Ti (purity:99.6%, Nilaco Corp., Japan) were stacked as the target.
The Ti foils were inserted for the nat Ti(α, x)51 Cr monitor reaction to assess the target thicknesses and beam
parameters. Their average thicknesses were 20.26 and2.24 mg/cm2 , which were derived from their measured
weights and areas. The stacked target was irradiatedfor 1 h by a 50-MeV α beam with an intensity of
100.1 pnA measured with a Faraday cup. The initial beam energy was determined by the time of ﬂight
measurement.8) The energy degradation in the stacked
target was calculated by the SRIM code.9) The irradiated foils were separated and subjected to the γ-ray
spectrometry using a HPGe detector. The nuclear decay data were taken from the NuDat 2.7 database.10)
The cross-sections of nat Ti(α, x)51 Cr monitor reaction were derived from the measurement of γ line at
320.08 keV (Iγ = 9.910%). The result was compared400300200
100010203040
Energy (MeV)

5060Fig. 1. Preliminary result of nat Er(α, x)169 Yb comparedwith previous data3–6) and TENDL-2017.7)

with the recommended values of IAEA and we conﬁrmed the accuracy of the foil thicknesses and beamparameters within the uncertainties.
The γ line at 177.21 keV (Iγ = 22.28%) was used
to derive the cross-sections of 169 Yb. The comparison
between our preliminary result, former experimental
data, and the TENDL-2017 data is shown in Fig. 1.
The peak position of our result is consistent with thedata obtained by B. Király et al. (2008).3) However,
the amplitude of their data is larger than our result.
Other experimental data4–6) are very diﬀerent from ourresult. The TENDL-2017 data show a peak at thesame energy as ours, although the ampulitude of thepeak is lower.
References
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165, 295 (1992).
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(2012).
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10) National Nuclear Data Center, The NuDat 2 database,
http://www.nndc.bnl.gov/nudat2/.