ERA Research in Japan

An overall view of ERA research plan in Japan is given. The system has a field emission electron gun producing several kA driven by a Marx and a Blumlein during some tens of nsec and a large vacuum chamber made of stainless steel into which the electron beam is injected and captured. The coils for compression are placed inside the chamber and produce a fast rising magnetic field. The electron ring has a final radius of about 2 cm and the energy of electrons should be about 10 Mev. Special attention is given to the theoretical and the experimental studies of the collective phenomena related to the ring stability just after the injection, the possibility and the efficiency of the acceleration of a charged bunch with an RF cavity, and other problems of the instabilities that may arise.