[en] A shielding experiment was performed at the HIMAC (Heavy Ion Medical Accelerator in Chiba), of National Institute of Radiological Sciences (NIRS), to measure neutron dose using a spherical TEPC (tissue-equivalent proportional counter) of 12.55 cm inner diameter. Neutrons are produced from a 5 cm thick stopping length Cu target bombarded by 400 MeV/nucleon C⁶⁺ ions and penetrate concrete or iron shields of various thickness at 0 degree to the beam direction. From this shielding experiment, y-distribution, mean lineal energy, absorbed dose, dose equivalent and mean-quality factor were obtained behind the shield as a function of shield thickness. The neutron dose attenuation lengths were also obtained as 126 g cm^-2 for concrete and 211 g cm^-2 for iron. The measured results were compared with the calculated results using the MARS Monte Carlo code. (author)

[en] Charge-changing and fragment production cross sections have been obtained for interactions of a 600 MeV/nucleon neon beam in H, C, Al, Cu, Sn, and Pb targets. The H target results were obtained using a polyethylene target and subtracting the cross sections obtained with the carbon target. At 600 MeV/nucleon, the angular distributions of the fragments are strongly forward-peaked, and consequently the spectra seen in the detectors with the largest angular acceptance - corresponding to a forward cone with half-angle 7 degrees - show obvious fragment peaks only for charges 5 through 9. No clear peaks are seen below charge 5 in the large-acceptance detectors, but spectra from detectors subtending smaller angular acceptances show peaks for all fragment species, and additional identifiable peaks from events with between two and four fragments in coincidence. Production cross sections for all fragment species, from the aforementioned targets, are reported here and, where possible are compared t o earlier measurements and to the predictions of the NUCFRG2 and QMSFRG models and an empirical parameterization that is tuned for higher-mass beams. The cross sections for fragments of charge 5 and below have not been previously reported. Also, the charge-changing cross sections are compared to earlier measurements and to NUCFRG2 and the Bradt-Peters model

[en] Charge-changing and fragment production cross sections have been obtained for interactions of a 600 MeV/nucleon neon beam in H, C, Al, Cu, Sn, Ta, and Pb targets. The H target results were obtained using a polyethylene target and subtracting the cross sections obtained with the carbon target. At 600 MeV/nucleon, the angular distributions of the fragments are strongly forward peaked, and consequently the spectra seen in the detectors with the largest angular acceptance -- corresponding to a forward cone with half angle 7^o -- show obvious fragment peaks only for charges 5 through 9. No clear peaks are seen below charge 5 in the large-acceptance detectors, but spectra from detectors subtending smaller angular acceptances show peaks for all fragment species, and additional identifiable peaks from events with between two and four fragments in coincidence. Production cross sections for all fragment species are reported here and, where possible, compared to earlier measurements and to the predictions of three model calculations (Nucfrg2, Qmsfrg, and an empirical parametrization that is tuned for higher-mass beams). The cross sections for fragments of charge 5 and below have not been previously reported. Also, the charge-changing cross sections are compared to earlier measurements and to Nucfrg2 and the Bradt-Peters model

[en] Charge-changing and fragment production cross sections at 0 circ have been obtained for interactions of 290 MeV/nucleon and 400 MeV/nucleon carbon beams with C, CH2, Al, Cu, Sn, and Pb targets. These beams are relevant to cancer therapy, space radiation, and the production of radioactive beams. We compare to previously published results using C and CH2 targets at similar beam energies. Due to ambiguities arising from the presence of multiple fragments on many events, previous publications have reported only cross sections for B and Be fragments. In this work we have extracted cross sections for all fragment species, using data obtained at three distinct values of angular acceptance, supplemented by data taken with the detector stack placed off the beam axis. A simulation of the experiment with the PHITS Monte Carlo code shows fair agreement with the data obtained with the large acceptance detectors, but agreement is poor at small acceptance. The measured cross sections are also compared to the predictions of the one-dimensional cross section models EPAX2 and NUCFRG2; the latter is presently used in NASA's space radiation transport calculations. Though PHITS and NUCFRG2 reproduce the charge-changing cross sections with reasonable accuracy, none of the models is able to accurately predict the fragment cross sections for all fragment species and target materials

[en] The neutron response functions of 12.7 cm diameter by 12.7 cm long NE213 organic liquid scintillator have been measured in the energy range from 50 to 800 MeV at the Heavy-Ion Medical Accelerator in Chiba (HIMAC). Neutrons were generated by the 800 MeV/nucleon Si ion and 400 MeV/nucleon C ion bombardment on a thick carbon target. Neutron energy was determined by the time-of-flight method with using the beam pick-up scintillator. The maximum light outputs were gradually increased with increasing incident neutron energy and the variation of the response functions have been observed up to 800 MeV. The experimental results show good agreement with other experimental results and the calculated values for incident neutron energy below about 200 MeV

[en] In planning for long-duration spaceflight, it will be important to accurately model the exposure of astronauts to heavy ions in the Galactic Cosmic Rays (GCR). As part of an ongoing effort to improve heavy-ion transport codes that will be used in designing future spacecraft and habitats, fragmentation cross sections of 28Si have been measured using beams with extracted energies from 290A MeV to 1200A MeV, spanning most of the peak region of the energy distribution of silicon ions in the GCR. Results were obtained for six elemental targets: hydrogen, carbon, aluminum, copper, tin, and lead. The charge-changing cross sections are found to be energy-independent within the experimental uncertainties, except for those on the hydrogen target. Cross sections for the heaviest fragments are found to decrease slightly with increasing energy for lighter targets, but increase with energy for tin and lead targets. The cross sections are compared to previous measurements at similar energies, and to predictions of the NUCFRG2 model used by NASA to evaluate radiation exposures in flight. For charge-changing cross-sections, reasonable agreement is found between the present experiment and those of Webber, et al. and Flesch, et al., and NUCFRG2 agrees with the data to within 3 percent in most cases. Fragment cross sections show less agreement between experiments, and there are substantial differences between NUCFRG2 predictions and the data

[en] Neutron energy spectra penetrated through iron shields were measured using the Self-TOF detector and an NE213 organic liquid scintillator which have been newly developed by our group at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) of National Institute of Radiological Sciences (NIRS), Japan. Neutrons were generated by bombarding 400 MeV/nucleon C ion on a thick (stopping-length) copper target. The neutron spectra in the energy range from 20 to 800 MeV were obtained through the FORIST unfolding code with their response functions and compared with the MCNPX calculations combined with the LA150 cross section library. The neutron fluence measured by the NE213 detector was simulated by the track length estimator in the MCNPX, and evaluated the contribution of the room-scattered neutrons. The calculations are in fairly good agreement with the measurements. Neutron fluence attenuation lengths were obtained from the experimental results and the calculation

[en] Recently, high-energy heavy ions have been used in various fields of nuclear physics, radiotherapy, material physics, and so on. Safety design consideration for heavy ion accelerator facilities requires nuclear reaction cross section data for high-energy ions to estimate the radioactivities induced in the accelerator components and in the shielding materials. We irradiated 230 and 100 MeV/nucleon Ar, Ne, C, He, p ions onto a Cu target to investigate the projectile dependency of induced radioactivities of spallation products. Irradiation experiments were performed at HIMAC (Heavy Ion Medical Accelerator in Chiba), National Institute of Radiological Sciences, Japan. The Cu target was composed of a stack of Cu plates, and C, Al, Cr, Fe, Ni, Cu, Pb samples were inserted between the Cu plates. The samples put on the front surface of Cu target are for measurement of reaction cross sections and the mass-yield distribution of produced nuclides. The samples inserted between the Cu plates are for measurement of the spatial distribution of the residual activities of produced nuclides in the Cu target. The thickness of Cu target is larger than the range of the projectile beam. After irradiation, we measured the gamma-ray spectra from samples with a HPGe detector. We obtained the spatial distribution of the residual activities of nuclides produced in these samples and the mass-yield distribution of nuclides produced on the surface of Cu target. For example, we could find the maximum number of 44 radioactive nuclides from ₆₅ Zn down to ₇Be in Cu sample. The results show that the dependence of the mass-yield distribution and the spatial distribution of the residual activities on the projectile mass varies with the mass number difference between the sample nuclide and the produced nuclide. These experimental results were compared with the Monte Carlo calculation

[en] A new type detector, called 'Self-TOF detector', has been developed for high energy neutron spectrometry behind a shield. The detector consists of a veto counter, a set of radiators with 20 thin detectors, a start counter and a stop counter of nine segments. The measurement of the detector response function for high energy neutrons and the concrete and iron shielding experiments were done at the Heavy-Ion Medical Accelerator in Chiba (HIMAC) of National Institute of Radiological Sciences (NIRS), Japan. By using the response functions, neutron spectra behind shield were obtained by unfolding and the results were compared with the LAHET Code System (LCS)

[en] Dosimetry of 70 MeV proton beams for radiotherapy was carried out using various ionization chambers. The beam irradiation conditions, dose estimation with an ionization chamber, measurement of dose distributions, and calculation of isodose curves for the proton beams will be discussed