Just after completion of the 12-GeV proton synchrotron complex at KEK in 1976, medical use of rapid-cycling 500-MeV Booster beams were investigated. Prof. Herman Suit of Harvard University recommended proton beam therapy, and soon it became clear that it was most suitable for Tsukuba. University of Tsukuba built and operated a medical research center with support of KEK. It included three activities, fast neutron therapy, proton radiography and proton therapy. It was showed clinically that the proton beam therapy is effective for deep-seated tumors such as hepatoma.

Power supplies of thyristor–rectifier type for electric strings of magnets of HIMAC synchrotrons are characterized by high stability and nice reproducibility in addition to low noise. Excellent power supplies result in stable acceleration without beam feedback due to high performance of 2 ppm for dc without such an active filter as a series dropper and 0.3 ppm for ac with an active filter of reactor-transformer type. A special electrical configuration of both power supplies and electric strings of magnets is based on separation of normal mode and common mode, both of which were found in existing machines of other laboratories in Japan. In this way a static filter for common mode in addition to that for normal-mode is very effective in suppressing noise for both dc and ac.

This article presents basic properties of coherent synchrotron radiation (CSR) with numerical examples and introduces the reader to important aspects of CSR in future accelerators with short bunches. We show interesting features of the single bunch instability due to CSR in storage rings and discuss the longitudinal CSR field via the impedance representation.

Plasma type instabilities are serious issue in recent high intensity accelerators. Extra-particles, ions or electrons, are created by the beam due to ionization, photoemission, secondary emission and/or other mechanisms. The beam and the extraparticles form non-neutral plasma with different collective velocities. Two-stream instability is caused by the interaction between these two beams with different velocities. We discuss general picture of the two stream instability in accelerators, especially speaking three typical effects; e-p, ion, electron clouds.

Hiroshima University has been collaborating with Tomsk Polytechnic University, one of the major Technical Universities in Russia, since fifteen years ago. The main fields of joint research are radiation phenomena in periodic matter, e.g. parametric x rays and coherent pair creation, and R&D of small accelerators and their application.