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Journal Articles

Measurement of neutron production double-differential cross-sections on carbon bombarded with 430 MeV/nucleon carbon ions

Itashiki, Yutaro*; Imabayashi, Yoichi*; Shigyo, Nobuhiro*; Uozumi, Yusuke*; Satoh, Daiki; Kajimoto, Tsuyoshi*; Sanami, Toshiya*; Koba, Yusuke*; Matsufuji, Naruhiro*

Journal of Radiation Protection and Research, 41(4), p.344 - 349, 2016/12

Carbon ion therapy has achieved satisfactory results because of high curability and minimally invasiveness. However, patients have a risk to get a secondary cancer. In order to estimate the risk, it is essential to understand particle transportation and nuclear reactions in the patient's body. The particle transport Monte Carlo simulation code is a useful tool to understand them. Since the code validation for heavy ion incident reactions is not enough, the experimental data of the elementary reaction processes is needed. We measured neutron production double-differential cross-sections (DDXs) on a carbon bombarded with 430 MeV/nucleon carbon beam which is a possible candidate of future therapy beam. The experiment was performed at PH2 beam line of the HIMAC of National Institute of Radiological Sciences. The 430 MeV/nucleon carbon beam was irradiated on a 5 cm $${times}$$ 5 cm $${times}$$ 1 cm graphite target rotated 45$$^{circ}$$ to the beam axis. The beam intensity was set to 10$$^{5}$$ particles / spill. A 0.5 mm thick NE102A plastic scintillator was placed to monitor the beam intensity. Neutrons produced in the target were measured with two sizes of NE213 liquid organic scintillators located at six angles of 15, 30, 45, 60, 75, and 90$$^{circ}$$. The 5.08 cm long one was used to obtain the neutron spectra from 1 MeV to 10 MeV and the 12.7 cm long one was used above 5 MeV. The 2 mm thick NE102A plastic scintillators to discriminate charged particles were set in front of the neutron detectors. The kinetic energies of neutrons were determined by the time-of-flight (TOF) method. Background neutrons were estimated by a measurement with iron shadow bars between the target and each neutron detector. An electronic circuit for data acquisition consisted of NIM and CAMAC modules. The experimental data was compared with calculated results obtained by Monte Carlo simulation codes as PHITS. The PHITS code reproduced the experimental data well.

Journal Articles

Distributions of neutron yields and doses around a water phantom bombarded with 290-MeV/nucleon and 430-MeV/nucleon carbon ions

Satoh, Daiki; Kajimoto, Tsuyoshi*; Shigyo, Nobuhiro*; Itashiki, Yutaro*; Imabayashi, Yoichi*; Koba, Yusuke*; Matsufuji, Naruhiro*; Sanami, Toshiya*; Nakao, Noriaki*; Uozumi, Yusuke*

Nuclear Instruments and Methods in Physics Research B, 387, p.10 - 19, 2016/11

 Times Cited Count:3 Percentile:28.38(Instruments & Instrumentation)

Double-differential neutron yields from a water phantom bombarded with 290-MeV/nucleon and 430-MeV/nucleon carbon ions were measured at emission angles of 15$$^{circ}$$, 30$$^{circ}$$, 45$$^{circ}$$, 60$$^{circ}$$, 75$$^{circ}$$, and 90$$^{circ}$$ using the neutron-detection system constituting of liquid organic scintillators. The angular distributions of neutron yields and effective doses around the phantom were obtained by integrating the double-differential neutron yields and applying the fluence-to-effective dose conversion coefficients. The experimental data were compared with results of the Monte-Carlo simulation code PHITS. The PHITS results showed good agreement with the measured data. From the results, we concluded that the PHITS simulation is applicable to the dose estimation at carbon-therapy facilities.

Journal Articles

Measurement of neutron production cross sections from heavy ion induced reaction

Shigyo, Nobuhiro*; Uozumi, Yusuke*; Imabayashi, Yoichi*; Itashiki, Yutaro*; Satoh, Daiki; Kajimoto, Tsuyoshi*; Sanami, Toshiya*; Koba, Yusuke*; Takada, Masashi*; Matsufuji, Naruhiro*; et al.

JAEA-Conf 2014-002, p.81 - 87, 2015/02

Cancer therapy using heavy ion beam has been adopted as highly advanced medical treatment by reason of its clinical advantages. It has become more important to estimate the risk of secondary cancer from recent survey. During treatment, secondary particles such as neutrons and -rays are producedby heavy ion induced nuclear reactions in a patient body as well as beam delivery apparatuses. For the risk assessment of secondary cancer, it is essential to know contribution of secondary neutrons by extra dose to organs in the vicinity of the irradiated tumor because the secondary neutron has a long flight path length and gives undesired dose to normal tissues in a wide volume. The experimental data of neutron energy spectra are required for dose estimations with high accuracy. Especially, precise data around neutron energy of 1 MeV is required because neutron of the energy region has a large relative biological eectiveness. Estimation of the secondary neutron yield data is important for estimation of radiation safety on both of workers and public in treatment facilities.

Oral presentation

Study on neutron yield and dose distributions around a water phantom bombarded by carbon ions with therapeutic energies

Satoh, Daiki; Kajimoto, Tsuyoshi*; Shigyo, Nobuhiro*; Itashiki, Yutaro*; Imabayashi, Yoichi*; Koba, Yusuke*; Matsufuji, Naruhiro*; Sanami, Toshiya*; Nakao, Noriaki*; Uozumi, Yusuke*

no journal, , 

For reasonable design of shields at heavy-ion therapy facilities, it is important to understand neutron yields and doses around a patient bombarded by heavy-ion beams. In the present study, we measured the neutrons emitted from a water phantom, which mimics a body of patient, bombarded by carbon ions with therapeutic energy of 290 MeV/nucleon. The neutron detectors composed of liquid organic scintillator were placed at the directions of 15$${^circ}$$, 30$${^circ}$$, 45$${^circ}$$, 60$${^circ}$$, 75$${^circ}$$ and 90$${^circ}$$ with respect to the beam axis. By applying conversion coefficients of effective dose for AP irradiation to the measured double-differential neutron yields and integrating them above 2 MeV which is the minimum energy of the experimental data, we obtained the effective-dose distribution around the water phantom. The experimental data were compared with the results of the Monte-Carlo simulation code PHITS. While PHITS can reproduce the neutron spectra in higher energy region well, it overestimates the spectra below about 10 MeV. The effective dose calculated by PHITS with the same integration period also gave a larger value compared with the experimental data. We adjusted the absolute values of the PHITS results to agree with the experimental data at 90$${^circ}$$, and deduced the effective-dose distribution for neutrons above thermal energy in the angular region from 0$${^circ}$$ to 180$${^circ}$$. Furthermore, a simple analytic function was proposed to give the dose distribution around a patient. It makes possible to assess the dose distribution quickly and easily with sufficient precisions. These results contribute to a sophistication of shielding design at heavy-ion therapy facilities.

Oral presentation

Measurement of 430-MeV/u carbon, nitrogen and oxygen incident neutron production cross sections for carbon

Shigyo, Nobuhiro*; Uozumi, Yusuke*; Itashiki, Yutaro*; Lee, J. E.*; Imatomi, Kosuke*; Kajimoto, Tsuyoshi*; Satoh, Daiki; Sanami, Toshiya*; Koba, Yusuke*; Matsufuji, Naruhiro*

no journal, , 

Heavy ion cancer therapy has been increased by reason of its clinical advantages. During the treatment, the secondary particles are produced by nuclear reactions of a heavy ion incidence on a nucleus in a patient body. The neutron cross section data is essential for assessment of secondary cancer of patients as a source term. Accurate data in neutron energy around 1 MeV is required because neutron in that energy region has large relative biological effectiveness. We have measured the neutron double differential cross sections from carbon, nitrogen and oxygen ion incidences on a carbon target of neutron energy above 1 MeV in wide angular range from 15 to 90 degrees with 430-MeV/u. The experiment was performed at the PH2 course of Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences. Experimental results of neutron double differential cross sections of carbon were obtained in energy range from 1 MeV to 600 MeV. From the comparison with the results calculated by PHITS code, it was found that PHITS reproduces the measured cross sections 100 MeV and slightly overestimates above the energy. The quantum molecular dynamics model, which is adopted in PHITS as a theoretical one for dynamical process of heavy ion induced nuclear reaction, would cause this disagreement. The results of the present work will help to improvement of the model.

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