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Nakamura, Mitsutaka; Nakajima, Kenji; Kajimoto, Ryoichi; Arai, Masatoshi
Journal of Neutron Research, 15(1), p.31 - 37, 2007/03
The efficiency of measurement on a chopper spectrometer will be significantly improved, if we can measure a number of inelastic scattering processes simultaneously. In such measurements we should deliver the multiple incident energy neutrons to the sample within a pulse period of the source. This method was proposed by Mezei and referred to as Repetition Rate Multiplication (RRM) measurement. Since optimizing the chopper spectrometer for monochromatic beam experiment is our first priority, the RRM measurement might be optional operation. However, even without replacing a chopper blade nor accepting very long flight path, a slight modification of the instrument design enables the RRM measurement in considerably excellent performance. In this talk, we will explain the instrument design to realize the RRM measurement on chopper spectrometers at J-PARC, and show its performance.
Kajimoto, Ryoichi; Yokoo, Tetsuya*; Nakajima, Kenji; Nakamura, Mitsutaka; Soyama, Kazuhiko; Ino, Takashi*; Shamoto, Shinichi; Fujita, Masaki*; Oyama, Kenji*; Hiraka, Haruhiro*; et al.
Journal of Neutron Research, 15(1), p.5 - 12, 2007/03
We are developing a new chopper-type neutron inelastic spectrometer 4SEASONS for the spallation neutron source at J-PARC. This spectrometer has middle energy resolution and two orders higher efficiency than the ones at ISIS for a single crystal measurement. With this spectrometer, we try to explore novel quantum phenomena, in particular, the mechanism of the high-
superconductivity. The high flux at a sample is achieved by incorporating the well designed transport devices in addition to the high flux of the source. The energy resolution is estimated to be 5-6% at 
= 0. Furthermore, the most distinguishing feature of 4SEASONS is the availability of the repetition rate multiplication (RRM) method. The RRM method enables us to utilize many 
's at the same time, which will increase the efficiency of the measurement more than five times and make the survey of 4D space of 
-
much easier.
Takahashi, Nobuaki; Shibata, Kaoru; Sato, Taku*; Arai, Masatoshi
Journal of Neutron Research, 15(1), p.61 - 67, 2007/03
The DIANA spectrometer is an indirect-geometry crystal-analyzer instrument which will be installed at the Materials and Life science experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). The available momentum transfer and energy ranges are from about 0.1 A
to 3.9 A and from about 2 
eV to 35 meV, respectively. Three analyzer-crystals, PG(002), Ge(311) and Si(111) are planed to put into place. The energy resolutions of each the former two analyzer-crystal setting are sufficiently high, which are about 15 eV and 40 eV, respectively. We are especially aiming very high energy resolution of about 2.5 eV by using the Si(111) analyzer-crystal together with another pulse-shaping mechanism, an optional setting for the DIANA spectrometer. This option can only be attained by using highly sophisticated silicone crystal, i.e. obtaining low mosaicness, and very sharp pulse-shaped incident neutron beam, which is obtained from counter-rotating 2-disk choppers with each rotation frequency of 300 Hz. Although one can attain such a high energy resolution, it is considerably inefficient to chop one very narrow incident neutron energy band from one frame (one pulse from a moderator). If several incident beam having different energy band from each other are available by chopping within one frame several times, the obtainable energy range substantially enlarge. We discuss the advantage and disadvantage of this multiplication, which is named Repetition Rate Multiplication (RRM), of the optional setting for DIANA spectrometer.
Nakajima, Kenji; Nakamura, Mitsutaka; Kajimoto, Ryoichi; Osakabe, Toyotaka; Kakurai, Kazuhisa; Matsuda, Masaaki; Metoki, Naoto; Wakimoto, Shuichi; Sato, Taku*; Ito, Shinichi*; et al.
Journal of Neutron Research, 15(1), p.13 - 21, 2007/03
no abstracts in English
