The N0 couse is a neutron TOF facility with flight path length of 100 m at maximum, offering opportunities for high-precision experiments on nuclear reactions associated with neutron emissions and absorptions in the energy range from a few MeV up to 400 MeV. Anguler distribution measurements are available with use of a movable target system.

The N0 course is equipped with a neutron polarimeter NPOL3 for measurement of the nuclear polarization transfer observables in the (p,n) reactions with a spin polarized proton beam. NPOL3 consists of position-sensitive organic scintillators covering an area of 1 m × 1 m. The effective analyzing powers A_y(eff.) are typically 0.37-0.43 and 0.13-0.15 for (n,n) and (n,p) channels, respectively.

The N0 course is one of the world-brightest sources of quasi-monoenergetic MeV neutrons. It has been used for studies of the cross sections of neutron-induced nuclear reactions, neutron shieldings, responses of neutron detectors, and so on. Typical intensity and energy spread for the zero-degree component of the 387 MeV neutron beam are (0.9±0.15)×10¹⁰ /sr/μC and 0.75% (FWHM), respectively.

For more technial information, please refere to the following papers.

Continuous proton beams with energies of a few MeV to 392 MeV are delivered to the N0 course with beam current of up to 1 micro-A, and impinge upon targets for (p,n) reactions. Proton polarization of up to 70% is available. Pulsed beam with a time interval of up to 1 micro-sec can be generated by using a beam chopper at the cost of the beam intensity. The flight path length of the neutrons can be changed from 10 m to 100 m using a handcart for a detector support. The time resolution for neutrons is typically 0.7 ns (FWHM) including the time spread of the incident proton beam of 200 ps and the thickness effects of the neutron production target and the neutron detector. Angular distributions of the emitted neutrons can be measured at the angle from 0 to 25 degree with use of a movable target system. The neutron polarimeter NPOL3 is available for the measurement of the nuclear polarization transfer observables in the (p,n) reactions. NPOL3 consists of position-sensitive organic scintillators covering an area of 1 m × 1 m. The effective analyzing powers A_y(eff.) are typically 0.37-0.43 and 0.13-0.15 for (n,n) and (n,p) channels, respectively. The double scattering efficiencies are of the orders of 10^-4 and 10^-3 for (n,n) and (n,p) channels, respectively. Quasi-monoenergetic neutrons are produced via the 7Li(p,n)7Be reaction. Typical intensity and energy spread of the zero-degree component of the 387 MeV neutron beam are (0.95±-0.15)×10¹⁰ /sr/μC and 0.75% (FWHM), respectively.

For more technial information, please refere to the following papers.

The cross sections, analyzing powers and complete sets of polarization transfer observables for ²⁰⁸Pb(p,n) reaction were measured at a bombarding energy of 296 MeV. A multipole decomposition technique was applied to the data to extract the Gamow-Teller (GT) and spin-dipole (SD) components from the continuum. The polarization observables were also used, for the first time, to separate the SD components into different spin-parity transfer　(ΔJ^π=0^-, 1^-, and 2^-) contributions. A significant strength with ΔJ^π=1⁺ is identified in the continuum beyond the GT giant resonance, which is due to configuration mixing effects and the isovector spin monopole (IVSM) contribution. The SD strength distributions were clearly dependent on ΔJ^π,which is reasonably reproduced by Hartree-Fock (HF) plus random phase approximation (RPA) calculations that include the Skyrme interaction with tensor components.

Reference:

T. Wakasa et al., "Complete sets of polarization transfer observables for the ²⁰⁸Pb(p,n) reaction at 296 MeV and Gamow-Teller and spin-dipole strengths for ²⁰⁸Pb", Physical Review C85, 064606 (2012).

Reaction cross sections for Cr and Y induced by neutrons at 197 MeV were measured by using a quasi-monoenergetic neutron beam generated with the ⁷Li(p,n) reaction. Cr and Y samples were irradiated on the two angles of 0° and 25° relative to the axis of the primary proton beam. The measured cross section data in the ^natCr(n,x) and ⁸⁹Y(n,x) reactions are found to be consistent with the cross section data for the same target materials with 287 and 386 MeV neutrons in the previous work. The obtained results are compared to the JENDL high-energy file and the literature proton values, respectively, and it was suggested that the boundary energy where the calculation codes are replaced in the current JENDL-HE evaluations will shift to a new energy.

Reference:

S. Sekimoto et al., "Measurements of Cross Sections for Neutron-induced Reactions on Chromium and Yttrium Targets at 197 MeV", Nuclear Data Sheets 119, 197-200 (2014).

The neutron energy spectra of a quasi-monoenergetic ⁷Li(p,n) neutron source with 137, 200, 246 and 389 MeV protons were measured at seven angles (0°, 5°, 10°, 15°, 20°, 25° and 30°), using a time-of-flight (TOF) method employing organic scintillators NE213. The energy spectra of the source neutrons were precisely deduced down to 2 MeV at 0° and 10 MeV at other angles. Neutron energy spectra below 100 MeV at all angles were comparable, but the shapes of the continuum above 150 MeV changed considerably with the angle. It was found that subtracting the dose equivalent at larger angles (21° for 389 MeV, 25° for 246 MeV and 26° for 200 MeV) from the 0° data almost eliminates the continuum component. This method has potential to eliminate problems associated with continuum correction for high-energy neutron monitors.

Reference:

Y. Iwamoto, M. Hagiwara, H. Iwase, H. Yashima, D. Satoh, T. Matsumoto, A. Masuda, C. Pioch, V. Mares, T. Shima, A. Tamii, K. Hatanaka and T. Nakamura, "Characterization of quasi-monoenergetic neutron source using 137, 200, 246 and 389 MeV ⁷Li(p,n) reactions", Progress in Nuclear Science and Technology 4, 657-660 (2014).