A methodology for the time-of-flight measurement of the neutron energy spectrum for a high-energy proton-beam-induced reaction was established at the Fermilab Test Beam Facility of the Fermi National Accelerator Laboratory. The 120-GeV proton beam with 3 × 10 5 protons/spill was prepared for event-by-event counting of incident protons and emitted neutrons for time-of-flight energy determination. An NE213 organic liquid scintillator (12.7 cm in diameter by 12.7 cm in length) was employed with a veto plastic scintillator and a pulse-shape discrimination technique to identify neutrons. Raw waveforms of NE213, veto and beam detectors were recorded to discriminate the effects of multi-proton beam events by considering different time windows. The neutron energy spectrum ranging from 10 to 800 MeV was obtained for a 60-cm-long copper target at 90 degrees with respect to the beam axis. The obtained spectrum was consistent with that deduced employing the conventional unfolding technique as well as that obtained in a 40-GeV/c thin-target experiment.
JASMIN -Japanese and American Study of Muon Interaction and Neutron detection -a program for studies of shielding and irradiation effect around high energy accelerators has been started since 2007 using high energy proton accelerators located in Fermi National Accelerator Laboratory (FNAL) as a collaboration of JAPAN and FNAL. The series of the presentations entitled "Shielding experiments at high energy accelerators of Fermilab" describes the part of the results of this collaboration regarding transport of secondary particles, neutron and muon, from 120 GeV proton induced reactions through experimental data and simulation. In this paper, behavior and associated radiation dose of high energy muons in tens of meter thick rock are measured using OSLs, CR39s, TLDs and an ionization chamber. The doses for the same geometrical condition of the experiment are calculated using multi-particle Monte Carlo simulation code, MARS, to check its predictive power for muon transport and the dose. From this comparison, consistency between the experiment and calculation is confirmed in 60 m thick rock. The calculation enables to separate contributions of each particle to the dose. The result shows considerable amount of the contribution to the dose from electrons, photons and neutrons from electro-magnetic cascade due to interaction of high energy muon.
Neutron energy spectra behind iron and concrete shields have been measured at the anti-proton production target station in Fermi National Accelerator Laboratory to provide shielding benchmark data of neutrons produced from 120-GeV proton induced reaction. To measure neutron spectra in the radiation bursts accompanied by the injection of intense pulsed proton beam into the target, we have developed a current readout technique of a multi-moderator spectrometer. We employed a pair of BF 3 proportional counters filled with different 10 B isotope enrichment gases, nat BF 3 (18% enrichment) and 10 BF 3 (96% enrichment) and used them as current readout ionization chambers to avoid signal pile-up problem. The spectrometer is aimed to discriminate neutrons from other particles such as -rays and muons incoming in short bursts by subtracting results of the nat BF 3 counter from that of the 10 BF 3 counter. The neutron spectrum obtained with the present technique is generally consistent with results of neutron-induced activation measurements.
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