J-PARC Project Research Articles

Current status of the J-PARC muon facility, MUSE

The muon science facility (MUSE), along with the neutron, hadron, and neutrino facilities, is one of the experimental areas of the J-PARC project. The MUSE facility is located in the Materials and Life Science Facility (MLF), which is a building integrated to include both neutron and muon science programs. Since the autumn of 2008, users operation is effective and making use of the pulsed muon beam particularly at the D-Line. Unfortunately, MUSE suffered severe damages from the earthquake on March 11, 2011, the so-called "Higashi-Nippon Dai-Shinsai". We managed to have a stable operation of the superconducting solenoid magnet with use of the on-line refrigerator on December, 2012, although we had to overcome a lot of difficulties against components not working properly. But we had to stop again the whole operations on May 2013, because of the radioactive materials leakage accident at the Hadron Hall Experimental Facility. Finally we restarted the users' runs on February 2014.

Study of Superconducting Curved Solenoids for a High Intensity Muon Beam Line

A study of superconducting curved solenoids have been carried out for a high intensity muon beamline at JPARC project at KEK. The curved solenoid is designed with 6 segmented short solenoids combined with tapered spacers in series. A pair of model coils were successfully developed and assembled with the tapered spacer to demonstrate the technical concept and the practical assembly. The cool down and excitation tests were successfully carried out. The design and test results are discussed.

J-PARC muon facility, MUSE

The muon science facility (MUSE, abbreviation of MUon Science Establishment), along with the neutron, hadron, and neutrino facilities, is one of the experimental areas of the J-PARC project, which was approved for construction in a period from 2001 to 2008. The MUSE facility is located in the Materials and Life Science Facility (MLF), which is a building integrated to include both neutron and muon science programs. Construction of the MLF building was started in the beginning of 2004, and was completed at the end of the 2006 fiscal year. For Phase 1, we managed to install one super-conducting decay/surface muon channel with a modest-acceptance (about 45 mSr) pion injector in the summer of 2008. Finally, on September 19th, 2008, the 20 mm thick edge-cooled, non-rotating graphite target, which is surrounded by a copper frame, was, for the first time, placed into the 3GeV proton beam obtained from the rapid cycling synchrotron (RCS). The nuclear reactions between the 3 GeV proton beam and the nucleus of carbon produce both positively (π+) and negatively (π−) charged pions. On September 26th, 2008, we finally succeeded to extract? surface muons (μ+), which are obtained from the decay of π+ near the surface of the pion production target in the proton beam line. First, we commissioned the secondary muon beam line optics by tuning the superconducting magnet, the quadrupole and bending magnets, and the DC separator in order to optimize the transport of the surface muon beam and to eliminate the e+ contamination. Then, on December 25th, 2008, we also succeeded in the extraction of the "decay muons (μ+/μ-)", which are obtained through the in-flight decay of π+/π−

Muon Science and the Muon Science Facility (MUSE)

The muon science facility (MUSE), along with the neutron, hadron, and neutrino facilities, is one of the experimental areas of the J-PARC project, which was approved for construction in a period from 2001 to 2008. The MUSE facility is located in the Materials and Life Science Facility (MLF), which is a building integrated to include both neutron and muon science programs. Construction of the MLF building was started in the beginning of 2004, and was completed at the end of the 2006 fiscal year. Then, we completed the installation of the primary 3 GeV proton beam-line (the so-called M2 tunnel) components in the beginning of 2007.

J-PARC AND THE PROSPECTS OF HADRON PHYSICS

The high intensity proton accelerator complex, J-PARC, is now near the completion at Tokai Japan. We describe the J-PARC project and report its present status and the coming experiments with an emphasis on the nuclear and hadronic physics.

Alignment and shields in the M2 primary proton beamline at J-PARC

In the J-PARC project, the 3-GeV 333-μA proton beam will be transported from the 3-GeV ring to the neutron source located in the Materials and Life Science Facility. In the M2 tunnel, where the muon target is situated, the radiation level is expected to reach up to 20 MGy/y. Therefore, beamline components will need to be installed and aligned remotely from the maintenance area, which is located 4 m above the floor level. We have adopted alignment plates with pivots to position each component precisely in the beamline. Then, by using the surrounding iron shields as guides, a beamline component can be smoothly inserted and precisely aligned onto its alignment plate. In this paper, the alignment strategy used in the M2 tunnel is described.

J-PARC muon source, MUSE

The muon science facility (MUSE), together with the neutron, hadron, and neutrino facilities, is one of the experimental areas of the J-PARC project, which was approved for construction in a period from 2001 to 2008. The MUSE facility is located in the Materials and Life Science Facility (MLF) built for both neutron and muon sciences. Construction of the MLF building began in the beginning of 2004, and was completed in the end of the 2006 fiscal year. We have been working on the installation of the decay/surface muon beam line, expecting first muon beam in the Autumn of 2008.

STUDY OF IN-MEDIUM PROPERTIES OF N*(1535) AND CHIRAL SYMMETRY FOR BARYONS THROUGH THE η-MESIC NUCLEI FORMATION AT J-PARC

We investigate the properties of η-nucleus interaction by postulating the N*(1535) dominance for η-N system. We evaluate the N*(1535) properties in the nuclear medium using two kinds of chiral models, and find that these two models provide qualitatively different η-nucleus optical potentials reflecting the quite distinct properties of N*(1535) in these chiral models. Especially, in the chiral doublet model, we can expect to have the level crossing between η and N*(1535)-hole which is expected to provide the characteristic features for the optical potential and the formation spectra. We find also that the difference of these models can be seen in the formation cross sections of the η mesic nuclei with (π+, p ) reaction expected to be performed at J-PARC project.

Status of the J-PARC Project

Status of the J-PARC Project

Reduction of hydrogen content in pure Ti

Pure Ti is adopted as a material for ducts and bellows at the proton accelerator 3 GeV-RCS in J-PARC project, because of its small residual radioactivity. In the particle accelerator, the H2 outgassing due to ion impact is often the dominant source of gas release. As the reduction of hydrogen content will probably suppress ion induced desorption, we attempted to reduce the hydrogen content in the Ti by in-situ vacuum baking. First, thermal desorption behavior and the change in hydrogen content after the heat treatment were investigated. Vacuum firing at temperatures higher than 550°C was effective in reducing the hydrogen content in the Ti. At the same time, the mechanical properties were monitored because grain growth leads to decrease in mechanical strength. Even after treatment at 750°C for 12 hr, the decreases in tensile and yield strength were so small (∼10%) that we have no anxiety about the reduction of mechanical strength. Based upon the results of this study, vacuum firing has been applied to reduce the hydrogen content in the Ti bellows and ducts of the RCS machine.

Ｊ‐ＰＡＲＣで迎える結晶学の新展開 ２．Ｊ‐ＰＡＲＣがもたらす結晶学の新展開 単結晶中性子回折を用いた物性物理研究について

The application to single crystal neutron structural analysis is overviewed. Special attention is paid to the pulse neutron method, which will be available soon under J-PARC project in Japan. New proposal and preliminary experiment using Sirius at KENS are described.

Ｊ‐ＰＡＲＣで迎える結晶学の新展開 １．Ｊ‐ＰＡＲＣで展開される中性子科学 大強度陽子加速器計画（Ｊ‐ＰＡＲＣ）および物質・生命科学実験施設（ＭＬＦ）の概要

The J-PARC project has been conducted jointly by JAERI and KEK since 2001. This paper reports an overview and current status of the project. The high intensity proton accelerator consists of a 400 MeV Linac, a 3 GeV synchrotron and 50 GeV synchrotron to deliver MW level pulsed proton beam to experimental facilities. The MW proton power will provide an advanced scientific experimental research complex aiming at making breakthroughs in materials and life science with neutron and muon, nuclear and elementary physics, etc. Regarding the project being close to its completion in 2008, this paper describes the overview of J-PARC project with emphasis of the Materials and Life Science Experimental Facility, in which the MW pulsed neutron and muon sources, are placed to provide high quality neutron and muon beams to the world wide users.

A Road to J-PARC and the Future Beyond

This article is a personal view on historical efforts before realizing J-PARC pro ject. Prospective neutron sciences and a possible extension of J-PARC in the future are also outlined.

Toward the Start of Neutron Science at J-PARC

J-PARC is going to start its operation in the latter half of this fiscal year. It is one of the major topics among not only neutron science but also Japanese science and technology policy.This article describes a personal view on circumstances of the present neutron science and expectations of neutron science researchers to success the J-PARC project.

The Birth of the J-PARC

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.

Overview, Accelerator Development Status and Future of 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.

A high-resolution two-dimensional 3He neutron MSGC with pads for neutron scattering experiments

High-resolution neutron imaging detectors are required for future high-intensity neutron sources such as the J-PARC project in Japan. We are developing a high-resolution gaseous neutron detector by using the microstrip gas chamber (MSGC) with floating-pad readout method. In this paper, we describe the neutron detector performance obtained with this MSGC and the readout method. For a 3 cm×3 cm MSGC filled with 5 bar CF 4 and 0.5 bar 3He, we could achieve a measured position resolution of 0.6 mm (FWHM) including the beam size and the parallax error.

113 レーザ加工技術によるステンレス基板へのマイクロプリズムの作製(超塑性と材料および造形法)

An attempt has been made to manufacture a recursive mirror for the optical measurement of soundness of a mercury-target vessel that is to be installed in the J-PARC project at the JAEA. The mirror is comprised ofdozens of reentrant pyramids as large as about 100μm in length. In order to make such a micro shape directly on a stainless steel substrate, we modified a pulsed Nd:YAG laser with 1.06μm wavelength to achieve resolutions of 10μm in width and 1μm in depth for the laser ablation. Its feasibility has been confirmed by manufacturing a small triangle as large as about 50μm in width and about 1μm in depth under the conditions of a scanning speed of 1mm/min, a voltage of 272 V, and a hatching width of 2μm.

Reduction of Outgassing for Suppressing Electrical Breakdown in the Kicker Magnet of J-PARC RCS

Extraction kicker magnets in the RCS of the J-PARC project are now under construction. They are pulse magnets with high charging voltage of 60 kV, which are installed in vacuum chambers. They mainly consist of aluminum alloy for the electrode plates and ferrites for the magnetic cores. Some structures of the magnet were improved to suppress discharge, and we thoroughly reduced the rate of outgassing from the components. The surface of the aluminum alloy was finished by pit-free electropolishing. Aluminum alloy and ferrites cores were baked under vacuum before construction of the magnet. They were each baked until water, which is the main outgassing component, was reduced. As a result, their outgassing rates were reduced by two or three orders of magnitude. The effect of the excitation of the magnet was examined. Outgassing of certain components increased with application of the high voltage. These components were reduced by repeated periods of continuous excitation.

水素系物質の高圧科学と中性子への期待

Neutron is a complementary probe to X-ray for material sciences at high pressure, especially for hydrogen compounds for which X-ray is less powerful than for the heavier elements. In addition, using the neutron probe it is easy to distinguish neighboring elements in the periodic table which is also difficult with X-ray. A spallation neutron source of new generation is now being constructed in Tokai, Ibaraki Pref. as a part of the J-PARC project. A proposal to build a dedicated high-pressure beamline at J-PARC was submitted, which has been successfully accepted in 2005 after the peer-review. In this article, we review some examples of scientific targets on material sciences of hydrogen compounds at high pressure, which will be newly revealed with this powerful neutron source and beamline.