H. Iwase

Development of General-Purpose Particle and Heavy Ion Transport Monte Carlo Code

The high-energy particle transport code NMTC/JAM, which has been developed at JAERI, was improved for the high-energy heavy ion transport calculation by incorporating the JQMD code, the SPAR code and the Shen formula. The new NMTC/JAM named PHITS (Particle and Heavy-Ion Transport code System) is the first general-purpose heavy ion transport Monte Carlo code over the incident energies from several MeV/nucleon to several GeV/nucleon.

Development of heavy ion transport Monte Carlo code

Abstract We developed a heavy ion transport Monte Carlo code HETC-CYRIC which can treat the fragments produced by heavy ion reactions. The HETC-CYRIC code is made by incorporating a heavy ion reaction calculation routine, which consists of the HIC code, the SPAR code, and the Shen formula, into the hadron transport Monte Carlo code HETC-3-STEP. The results calculated with the HETC-CYRIC were compared with the experimental data, and the HETC-CYRIC gave good agreement with the experiment.

Measurement of deep penetration of neutrons produced by 800-MeV proton beam through concrete and iron at ISIS

Abstract A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory (RAL), UK. ISIS is an 800 MeV–200 μA proton accelerator facility. Neutrons are produced from a tantalum target, which is shielded with approximately 3-m thick iron and 1-m thick ordinary concrete in the upward direction. On the top of the shield, we measured the neutron flux attenuation through concrete and iron shields which were additionally placed up to 1.2-m and 0.6-m thicknesses, respectively, using the activation detectors of graphite, bismuth, aluminum and the multi-moderator spectrometer inserted indium. The attenuation lengths of concrete and iron for high-energy neutrons above 20 MeV produced at 90° to the proton beam were obtained from the 12 C ( n ,2 n ) 11 C reaction rates of graphite. The neutron spectra through concrete and iron were obtained by the unfolding analysis of the reaction rates of the 12 C ( n ,2 n ) 11 C , 27 Al ( n , α ) 24 Na , 209 Bi ( n ,x n ) 210−x Bi (x=4–10) and 115 In ( n , γ ) 116m In in the energy range of thermal to 400 MeV.

Secondary Neutron-Production Cross Sections from Heavy-Ion Interactions Between 230 and 600 MeV/Nucleon

Abstract Secondary neutron-production cross sections have been measured from interactions of 230 MeV/nucleon He, 400 MeV/nucleon N, 400 MeV/nucleon Kr, 400 MeV/nucleon Xe, 500 MeV/nucleon Fe, and 600 MeV/nucleon Ne interacting in a variety of elemental and composite targets. We report the double-differential production cross sections, angular distributions, energy spectra, and total cross sections from all systems. Neutron energies were measured using the time-of-flight technique and were measured at laboratory angles between 5 and 80 deg. The spectra exhibit behavior previously reported in other heavy-ion-induced neutron-production experiments, namely, a peak at forward angles near the energy corresponding to the beam velocity, with the remaining spectra generated by preequilibrium and equilibrium processes. The double-differential spectra are fitted with a moving-source parameterization. Observations on the dependence of the total cross sections on target and projectile mass are discussed.

Neutron Energy and Time-of-flight Spectra Behind the Lateral Shield of a High Energy Electron Accelerator Beam Dump,Part I: Measurements

Neutron energy and time-of-flight spectra were measured behind the lateral shield of the electron beam dump at the Final Focus Test Beam (FFTB) facility at the Stanford Linear Accelerator Center. The neutrons were produced by a 28.7 GeV electron beam hitting the aluminum beam dump of the FFTB which is housed inside a thick steel and concrete shield. The measurements were performed using a NE213 organic liquid scintillator behind different thicknesses of the concrete shield of 274 cm, 335 cm, and 396 cm, respectively. The neutron energy spectra between 6 and 800 MeV were obtained by unfolding the measured pulse height spectrum with the detector response function. The attenuation length of neutrons in concrete was then derived. The spectra of neutron time-of-flight between beam on dump and neutron detection by NE213 were also measured. The corresponding experimental results were simulated with the FLUKA Monte Carlo code. The experimental results show good agreement with the simulated results.

Measurements of Neutron Attenuation through Iron and Concrete at ISIS

A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory. ISIS is an 800MeV-200 μ A proton accelerator facility. Neutrons are produced from a tantalum target, and are shielded with approximately 3m thick iron and 1 m thick ordinary concrete. On the top of the shield, we measured the neutron flux attenuation through concrete and iron shields which were additionally placed up to 1.2 m and 0.6 m thicknesses, respectively, using activation detectors of carbon, aluminum and bismuth, and also indium-loaded multi-moderator spectrometer. The dose attenuation was simultaneously measured with the neutron and photon survey meters. The attenuation lengths of concrete and iron for high energy neutrons above 20MeV were obtained from the 12C(n,2n) reaction of carbon, and the neutron spectra penetrated through the additional shield and on the target shield top were obtained from the 12C(n,2n), 27Al(n,α) and 209Bi(n, xn) reactions, and multi-moderator spectrometer. We are now analyzing the measured results to compare with the shielding calculation.

Measurements of attenuation lengths through concrete and iron for neutrons produced by 800-MeV proton on tantalum target at ISIS

Abstract A deep penetration experiment through a thick bulk shield was performed at an intense spallation neutron source facility, ISIS, of the Rutherford Appleton Laboratory (RAL), United Kingdom. ISIS is a 800xa0MeV–200xa0μA proton accelerator facility. Neutrons are produced from a tantalum target, and are shielded with approximately 3-m thick steel and 1-m thick ordinary concrete. On top of the shield, we measured the neutron flux attenuation through concrete and iron shields, which were additionally placed up to 120-cm and 60-cm thickness, respectively, using activation detectors of graphite and bismuth. The attenuation lengths of concrete and iron for high-energy neutrons above 20xa0MeV were obtained from the 12 C(n,xa02n) 11 C reaction of graphite.

Development of Heavy Ion Transport Monte Carlo Code

We are developing a heavy ion transport Monte Carlo code which can treat the fragments produced by heavy ion reactions. For this purpose, we planned to combine the two codes, the one is the HIC or ISABEL code, to calculate the heavy ion nuclear reaction cross section and the other is the hadron transport Monte Carlo code, HETC-3STEP. First, we investigated the calculational accuracy of the HIC and ISABEL codes by comparing the calculated results with the experimental data. The ISABEL gives better agreement with the experimental data than the HIC. For easier handling we first coupled the HIC code with the HETC-3STEP code for developing the heavy ion transport Monte Carlo code. We also made a simple version of a heavy ion transport Monte Carlo code for limited geometry using the HIC code. The results calculated with this version of the code were compared with the experimental data. We are trying to couple the ISABEL code with the HETC-3STEP code.

Shielding Benchmark Experiments Through Concrete and Iron with High-Energy Proton and Heavy Ion Accelerators

The deep penetration of neutrons through thick shield has become a very serious problem in the shielding design of high-energy, high-intensity accelerator facility. In the design calculation, the Monte Carlo transport calculation through thick shields has large statistical errors and the basic nuclear data and model used in the existing Monte Carlo codes are not well evaluated because of very few experimental data. It is therefore strongly needed to do the deep penetration experiment as shielding benchmark for investigating the calculation accuracy. Under this circumference, we performed the following two shielding experiments through concrete and iron, one with a 800 MeV proton accelerator of the Rutherford Appleton Laboratory (RAL), England and the other with a high energy heavy iron accelerator of the National Institute of Radiological Sciences (NIRS), Japan. Here these two shielding benchmark experiments are outlined.

Measurements and Calculations of Secondary Particle Yields from 100-to 800 MeV/Nucleon Heavy Ions

Recently, high-energy heavy ions have been used in various fields of nuclear physics, material physics and medical application, especially cancer therapy. At the National Institute of Radiological Sciences (NIRS) in Chiba, Japan, the HI- MAC (Heavy Ion Medical Accelerator in Chiba ) has been used for the heavy ion cancer therapy for the last three years, and the GSI (Gesellschaft fur Schwerionenforschung) in Germany has just started heavy ion cancer therapy. Several institutes in the world have started or planned to build the radioactive beam facility where high-energy radioactive heavy ions are used for investigating exotic nuclei, nuclear synthesis and so on.