Program - Brookhaven National Laboratory

PB 2 4:00 PM
Measurement of 100- and 290-MeV/u Carbon Incident Neutron Production Cross Sections
for Carbon, Nitrogen and Oxygen
N. Shigyo, Y. Uozumi, H. Uehara, T. Nishizawa, T. Mizuno
Kyushu University
D. Satoh
Japan Atomic Energy Agency
T. Sanami
High Energy Accelerator Research Organization
Y. Koba, M. Takada, N. Matsufuji
National Institute For Radiological Sciences
Heavy ion cancer therapy has been increased by reason of its clinical advantages. During the treatment, the
secondary particles such as neutrons and γ-rays are produced by nuclear reactions of heavy ions incident
on a nucleus in a patient’s body. Estimation of the secondary neutron yield data is essential for assessment
of radiation safety on both of workers and public in treatment facilities. Accurate data for neutrons with
energy around 1 MeV is required because neutrons in this energy region have large relative biological
effectiveness. We have measured the neutron yields from carbon ions incident on carbon, nitrogen and
oxygen targets for neutron energies below 1 MeV in wide angular range from 15 to 90 degrees with 100and
290-MeV/u. The experiment was performed at the PH2 course of Heavy Ion Medical Accelerator
in Chiba (HIMAC), National Institute of Radiological Sciences. The 100- and 290-MeV/u carbon ion
beams were delivered from the HIMAC synchrotron via a 0.5 mm thick NE102A plastic scintillator (beam
monitor) to a target in order to monitor the number of incident carbon ions. The average beam intensity
was 3- 5x10 5 ions/3.3sec. For carbon, an aluminum nitride and an aluminum oxide plates were used as
targets. The target thicknesses were chosen for an incident carbon to deposit its energy of 10 - 15 % in the
targets. Measurement using an aluminum plate as a target was also done to obtain components of neutron
from aluminum element in AlN and Al2O3 targets. Three NE213 organic scintillators 12.7 cm thick and
12.7 cm in diameters were adapted to measure higher energy neutrons. And three NE213 scintillators
5.08 cm thick and 5.08 cm in diameter were applied for lower energy neutron measurement. An NE102A
plastic scintillator was set in front of each NE213 scintillator to discriminate between charged and noncharged
particles as a veto counter. Both size detectors were placed at 15, 30, 45, 60, 75 and 90 degrees.
The neutron energy was measured by the time-of-flight (TOF) technique between the beam monitor and
an NE213 scintillator. A measurement with 100 cm long iron bars between the target and each NE213
scintillator was also carried out to evaluate neutron contribution from the floor and other items in the
experimental area. In data analysis, charged particle and γ-ray events were eliminated using light output
spectra of veto counters and pulse shape discrimination for light output of NE213 scintillators, respectively.
The light output spectrum of the beam monitor was analyzed to separate one carbon ion incident event
from ones with two and more incident ones. The SCINFUL-QMD code was used to obtain the detection
efficiencies of NE213 scintillators with consideration of neutron scattering effect by the aluminum case of
the scintillator. By using the experimental data, the validity of the calculation results by Particle and
Heavy ion Transport Code (PHITS) was examined. Application of the PHITS code for shielding design of
heavy ion therapy facilities will be also discussed with the verification in the presentation.
PB 3 4:20 PM
Deuteron Induced Reactions on Rare Earths: Experimental Excitation Functions and
Comparison with Code Results
223