Neutron-production double-differential cross sections were measured for the spallation reaction induced by 0.8, 1.5 and 3.0 GeV protons on C, Al, Fe, In and Pb targets. The experiments were performed by time-of-flight technique with a typical flight path length of 1 m, and the cross sections were obtained with energy resolutions better than 8% at neutron energies below 100MeV. The experimental data were compared with the results of calculation codes based on an intranuclear-cascadeevaporation model. Adoption of the in-medium effect on nucleon-nucleon cross section in the cascade calculation improves the agreement between the calculated results and experimental data particularly in the case of 0.8-GeV proton incidence. For protons above 1 GeV, however, the calculations typically twice overestimate the cross sections in the emitted neutron energy region of 10 to 30MeV.
Abstract:At the Japan Proton Accelerator Research Complex (J-PARC), a pulsed spallation neutron source provides neutrons with high intensity and narrow pulse width pulse to promote researches on a variety of science in the Materials and Life Science Experimental Facility (MLF). It was designed to be driven by a proton beam with an energy of 3 GeV, a power of 1 MW at a repetition rate of 25 Hz, that is world's highest power level. It is still on the way towards the goal to accomplish the operation with a 1 MW proton beam. In this review, distinctive features of the target-moderator-reflector system of the pulsed spallation neutron source are presented.
The Japan Spallation Neutron Source (JSNS) is one of the major experimental facilities in the Japan Proton Accelerator Research Complex (J-PARC). JSNS operates with 3 GeV and 1 MW pulsed proton beams, and has the highest-class neutron intensity in the world. In the design stage, aiming for the best neutronic performance, the PHITS code was fully applied in the JSNS neutronics design, and calculations for several thousand cases were performed using complicated models. Not only optimization of neutronic performance, but also shielding calculation, nuclear heat estimation for the engineering design, residual radioactivity estimation for the cask design, and radiation damage estimation for the life and maintenance design were also done with the PHITS code. JSNS is one of the first facilities in the world to fully adapt such a simulation code to the neutronics design. In these calculations, note the change in particle energy from GeV to meV (12 decades), and that neutron fluxes are reduced by 10 decades or more. To confirm their reliability, these calculations were validated by measurement data for neutron spectral intensities, pulse shape, nuclear heat generation, and radioactivity. The results showed that the calculated values were in good agreement with the measured values. We confirmed that the PHITS code was reliable for such design calculations. At the same time, this indicates that the PHITS code is a powerful tool for neutronic design in other radiation source facilities and accelerator facilities.
The Materials and Life Science Experimental Facility (MLF) in J-PARC is a facility which generates neutron and muon beams by injecting highly intense pulsed proton beams into targets and supplies them to user experimental instruments. In the MLF, an interlock system (MLF-IL) is running to keep safety operations of the facility in various situations such as beam irradiations and target maintenances. Since the first proton beam injection in 2008, the MLF-IL has been operated stably without any serious troubles in spite of the device upgrades in the target systems and the increase of user instruments. This paper describes the design concept, the operation and the modification of the MLF-IL.
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