Progress of High-intensity Proton Accelerator Project: J-PARC (Japan Proton Accelerator Research Complex)

摘要

In the field of nuclear physics, since the beginning of 20th century, development of an accelerator for use in the nuclear physics field has been ongoing. The first accelerator was developed by Cockcroft and Walton in 1932 to break Li nuclide into two He nuclei using a 700keV proton. Since then many kinds of accelerators for various purposes, from material science to high energy physics, have now been developed. Especially in particle physics, an accelerator with higher energy, of more than GeV (GeV=10~9eV) has been at the forefront of development, such as LHC at CERN, which aims at obtaining more than 10TeV (TeV=10~(12)eV) of proton energy. On the other hand, material scientists desire higher intensity rather than acceleration energy, for utilization of ion implantation and synchrotron radiation. For example, recently the Japan Atomic Energy Research Institute (JAERI) and the Institute of Physical and Chemical Research (RIKEN) constructed SPring-8 in Japan, where photons radiated from high energy electrons are used for probes required upon researching the structure of materials. When we consider quantum particles as a microscopic probe, various unstable particles can be utilized, e.g., neutrons, muons, meson, pion and also unstable nuclei. These unstable particles can be produced by a high energy nuclear reaction with the energy more than several hundred MeV (MeV=10~6eV), a so-called spallation reaction, as shown in Fig. 1.