August 2000

In August, the JT-60U vacuum vessel was opened mainly for replacement of malfunctioned GDC electrodes. In the last week of August, tokamak experiments were resumed starting with TDCs and GDCs followed by wall conditioning tokamak discharges. The ratio of hydrogen to deuterium was well reduced and oxygen population was also reduced. Also tests of pellet injector was carried out. The injector was modified so as to inject pellets with injection velocity of as low as 100 m/s in order to avoid a pellet being crushed into peacies in the transfer tube especially for high field side-top injection. Operations of the injector at 100 m/s were confirmed, and increases of density were found to increase with decreasing injection velocity.