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Journal Articles

Neutron transport

Tamura, Itaru

Hamon, 28(4), p.204 - 207, 2018/11

https://doi.org/10.5611/hamon.28.4_204

A Neutron guide is one of the devices to transport neutron beam for long distance without sacrificing much neutrons; therefore, it can supply neutrons to many experimental instruments distributed in a large experimental hall. Also, by using a curved guide, only the neutrons in a required energy range can be transported, and rays and fast neutrons can be effectively eliminated, therefore the signal to background ratio is improved. In addition, a neutron beam can be branched by applying curved guides. Neutron guides are also used to control the divergence angle and intensity of the neutron beam supplied to the neutron instrument.

Journal Articles

Study of converging neutron guides for the cold neutron double-chopper spectrometer at J-PARC

Kajimoto, Ryoichi; Nakamura, Mitsutaka; Osakabe, Toyotaka; Sato, Taku*; Nakajima, Kenji; Arai, Masatoshi

Physica B; Condensed Matter, 385-386(2), p.1236 - 1239, 2006/11

https://doi.org/10.1016/j.physb.2006.05.419

Times Cited Count：9 Percentile：41.55(Physics, Condensed Matter)

Performance of a neutron guide has been studied for the Cold Neutron Double-Chopper Spectrometer (CNDCS) proposed for the spallation neutron source at J-PARC. This spectrometer is dedicated to inelastic neutron scattering studies in vast research fields in an energy range of $_{i}$ 80 meV. In order to detect weak inelastic signals, increasing neutron flux on sample with suppressing background at detector is very important. Installing a neutron guide is a well-known solution to these problems, because it can deliver much more neutrons to sample, and it can also cut off unwanted fast neutrons when installed in a curved layout. The performance of a neutron guide is much affected by its geometry. We have studied efficiency of the beam transport by a supermirror-coated guide designed for the CNDCS with conventional geometries such as straight, curved and tapered, as well as with advanced geometries such as ballistic, parabolic and elliptical. Energy dependence of gain in intensity, and beam distributions in space and angle obtained by Monte Carlo simulation will be discussed.

Journal Articles

Performance of upgraded thermal neutron guides with supermirrors at JRR-3

Tamura, Itaru; Suzuki, Masatoshi; Hazawa, Tomoya; Moriai, Atsushi; Hori, Naohiko; Sasajima, Fumio; Soyama, Kazuhiko

Nuclear Instruments and Methods in Physics Research A, 529(1-3), p.234 - 237, 2004/08

https://doi.org/10.1016/j.nima.2004.04.162

Times Cited Count：4 Percentile：30.89(Instruments & Instrumentation)

Thermal neutron guides at JRR-3 reactor have been upgraded from Nickel mirrors to Ni/Ti multilayer supermirrors. We performed the characteristics experiment of neutron beams transmitted through supermirror neutron guides. Neutron fluxes at the end of the thermal neutron guides were measured by the gold foil activation method on March 2003. We have confirmed that neutron fluxes at the end of thermal neutron guide increases by 6 times. The neutron spectra were also measured at the end of the thermal neutron guides by the time-of-flight method. The wavelength range for the neutron beam is extended and the shorter wavelength neutrons, which had been filtered by the characteristics of curved neutron guides before upgrade, were observed. In this paper, we have performed several Monte Carlo simulation codes using the McStas package in the consideration of the performance of fabricated supermirrors and its alignment errors for the purpose of estimation of instruments performance. We discuss the comparison of the experimental results with results of simulation.

Journal Articles

Water flow experiments and analyses on the cross-flow type mercury target model with the flow guide plates

Haga, Katsuhiro; Terada, Atsuhiko*; Kaminaga, Masanori; Hino, Ryutaro

Nuclear Engineering and Design, 210(1-3), p.157 - 168, 2001/12

https://doi.org/10.1016/S0029-5493(01)00413-7

Times Cited Count：3 Percentile：27.1(Nuclear Science & Technology)

The mercury target is used in the spallation neutron source driven by a high intensity proton accelerator. In this study the effectiveness of the cross-flow type mercury target structure was evaluated experimentally and analytically. Prior to the experiment, the mercury flow field and the temperature distribution in the target container were analyzed assuming the proton beam energy and power of 1.5GeV and 5MW. Then the average water flow velocity field in the target mock-up model, which was fabricated from plexiglass for a water experiment, was measured at room temperature using the PIV technique. Water flow analyses were also conducted. The experimental results showed that the cross-flow could be realized in most of the proton beam path area and the analytical result of the water flow velocity field showed good correspondence to the experimental result in the case of the Reynolds number of more than 4.83E5 at the model inlet. With these results, the effectiveness of the cross-flow type mercury target structure and the present analysis code system was demonstrated.

Journal Articles