II-9. Instrumentation

RIKEN Accel. Prog. Rep. 55 (2022)

RIKEN Accel. Prog. Rep. 55 (2022)

RI nuclides produced in stacked Si and Al plates by 135-MeV/nucleon
12C beam
T. Kambara∗1 and A. Yoshida∗1
On the basis of a fee-based facility sharing program,private companies in Japan use heavy-ion beams to simulate single-event eﬀects (SEE) on space-use semiconductor devices by cosmic rays.1) The clients have utilized
ion beams of Ar, Kr, and Xe from the RIKEN Ring Cyclotron (RRC) at the E5A beam line. The primary ion
beam is spread with a scatterer foil and wobbler magnets
and extracted to atmosphere. Then, it passes throughtransmission-type detectors for dose measurements andan energy degrader for linear energy transfer (LET) adjustments. The setup and irradiation procedures were
described previously.2)
The samples irradiated by the primary beam are also
impinged on by various secondary particles produced by
nuclear processes in the upstream materials. To evaluate the eﬀects of the nuclear processes, we irradiate test
samples in the same beam condition as the clients’ irradiation and measure RI nuclides by radiochemical analyses. Similar studies have been reported for a Kr beam3)
and a Xe beam.4)
Since clients expressed interest in the utilizationof a C beam, we studied the characteristics of a
135 MeV/nucleon 12 C beam. During the beamtime, weirradiated a stack of two Si plates (100-mm diameterand 0.5-mm thick) and two Al plates (3-mm thick) forradiochemical analyses. The irradiation setup is shownin Fig. 1. The primary beam passed through a 51.2-μmthick Kapton® window into the atmosphere and thenentered an ionization chamber (IC). From measurementwith the IC, the number of ions was estimated to beapproximately 1.08 × 1012 during 5 min of irradiation.
Then, the beam passed a 3-mm-thick plastic scintillator(not used) and an energy degrader of 18.42-mm-thick
Al. Its thickness was selected so that the primary ionsstopped in the second Si plate.
We measured the γ rays from each sample plate witha Ge detector from 13.4 min to 39.7 days after the irradiation for the Si plates and from 23.7 min to 6.49
days for the Al plates. Using the observed γ-ray spec-Fig. 2. Production probabilities of RI nuclides in the sample
plates.

tra, we identiﬁed 10 radionuclides from 7 Be to 34m Cl.
We extrapolated the decay curve of the radioactivity ofeach nuclide to the end of the irradiation to obtain thenumber of the nuclei identiﬁed in the sample. Then, wedivided it by the number of primary ions to obtain theproduction probability of the nuclide. The nuclides canbe produced by nuclear reactions either in the sample orin the upstream materials followed by transport to thesample.
The results are shown in Fig. 2, where the coloredbars indicate the probabilities in the sample plates. The
values of the probabilities in the Si plates are shown on
the left ordinate and those in the Al on the right so thatthe bar heights are scaled to the same number density ofthe sample atoms. Since the primary 12 C ions stopped
in the second Si plate, the nuclides in the Al plates were
either produced by secondary particles or transported
from the upstream. The γ rays of 28 Mg and 28 Al shownin Fig. 2(c) were measured only in the ﬁrst Si plate, andthose of 34m Cl in Fig. 2(b) were identiﬁed only in thesecond Si plate.
We are comparing the results with the simulationof nuclear processes using the Particle and Heavy Ion
Transport System (PHITS) code.5)
References

Fig. 1. Setup of the sample irradiation.
∗11) http://ribf.riken.jp/sisetu-kyoyo/ (Japanese).
2) A. Yoshida, T. Kambara, RIKEN Accel. Prog. Rep. 51,
185 (2018).
3) T. Kambara, A. Yoshida, Record of 2018 IEEE Radiation
Eﬀects Data Workshop (REDW), p. 94.
4) T. Kambara, A. Yoshida, RIKEN Accel. Prog. Rep. 52,
158 (2019).
5) https://phits.jaea.go.jp/index.html .

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