This year of 2008 should be memorized as the historic year of the J-PARC opening, which has been a long dream for the Japanese neutron community for more than 3 decades. The history of the neutron science activity in Japan is briefly digested at this special occasion and then I emphasize that this world first class neutron science facility of JPARC is realized by enormous big efforts for many years. Though the road map for the world top class Japanese neutron science facility has not been completed yet at J-PARC, I strongly hope that future Japanese neutron science after the opening of J-PARC would march along the way we have drawn and walked.
The J-PARC Project started in 2001 as a joint project between two organizations, JAEA and KEK. This article describes a) an early history on how people struggled to construct high-intensity proton accelerators, b) a creation of a joint effort between JAEA and KEK, and c) the birth of the J-PARC.
The 3-GeV beam accelerated by J-PARC Rapid-Cycling Synchrotron (RCS) was successfully extracted to the beam dump located at the beam transport to the neutron production target. The present status of the J-PARC accelerator development, in particular, that of the RCS, is reported together with the overview and future plan of the J-PARC project. It is presented how the new accelerator technologies developed for the J-PARC will contribute a lot to the world-wide progress of the proton accelerator field.
Main components used at JSNS (Japan Spallation Neutron Source) have been installed at MLF (Materials and Life science experimental Facility) in J-PARC, which will be capable to reach the highest intensity of pulse neutron beam in the world. Commissioning tests are carried out to accept proton beam at JSNS in May 2008. The issues for future of JSNS are described to increase beam power and prolong the lifetime of each component.
As the J-PARC user operation is scheduled to start within one year, a system for the user program has been thoroughly discussed in the J-PARC team in terms of access policy, program review, beam-time fee, treatment of output, intellectual property protection policy, etc. This paper reports the general concept of the J-PARC user program system.
The Japanese Society for Neutron Science established a special committee to discuss how to organize the Materials and Life Science Facility (MLF) founded in Japan Proton Accelerator Research Complex (J-PARC) in viewpoint of users. The article describes the discussions and suggestions from the special committee.
Contrast variation small angle neutron scattering method is reviewed. Due to overlapping of the scattering signals from each component, the data analyses of scattering patterns from multicomponent systems are attended with much difficulty. We can overcome this problem with the aid of contrast variation.In this manuscript, experimental procedure of the contrast variation small angle neutron scattering as well as a theoretical basis for understanding of the partial scattering functions (both self-terms and cross-terms) are briefly described.
The concentration fluctuation of acetonitrile-water and acetonitrile-water-MCl (M=Li+, Na+, and K+) mixtures has been investigated by using small-angle neutron scattering (SANS) technique. At 298, the concentration fluctuation of acetonitrile-water mixtures is most enhanced at acetonitrile mole fraction of xAN=0.3-0.4. When the temperature decreases to 279, the concentration fluctuation of the mixtures at xAN=0.3-0.4 drastically increases. For acetonitrile-water-MCl mixtures, the concentration fluctuation more easily increases in the order of NaCl>KCl>LiCl. This order agrees with that of salt-induced phase separation of acetonitrile-water mixtures.