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It was success to develop the radiation resistant components using for beam collimator. Turbo molecular pump could be operated more than 15 MGy of gamma ray irradiation dose. Stepping motor developed at JAERI could be operated with good performance in the gamma ray dose of more than 70 MGy. PEEK sheathed cables and connector have kept good performance during gamma ray irradiation more than the dose of 10 MGy. It was cleared that the function of the heat pipe disappeared at 30 kGy gamma ray irradiation dose.

It was success to develop alumina ceramics vacuum ducts for the 3GeV-RCS of J-PARC at JAERI. This duct has titanium flanges and exterior RF shield to reduce duct impedance. The longitudinal duct impedance was sufficient small for stable beam acceleration from impedance measurement by coaxial method. The temperature of titanium flange became 45 Co due to eddy current heating under dipole magnet operation. This duct is usable for the 3GeV-RCS of J-PARC.

Fast pressure gauges were installed in the JT-60 (JAERI Tokamak-60) to monitor the pressure near a plasma. They are Penning configuration gauges. A Penning discharge in the cell is sustained by the magnetic field which confines the plasma. The gauges are controlled by a personal computer. The response time of the system is fast ( >

In JT-60U, the highest fusion product of 1.2/spl times/10/sup 21/ keV sm/sup -3/ was recorded in July 1994, and the confinement performance has been also improved in the quasi-steady states (duration time /spl sim/1.5 s). The JT-60U has various wall conditioning methods. In particular, the boronization system using decaborane and B/sub 4/C-converted CFC divertor tiles was effective for reduction of the oxygen impurity and particle recycling. In the latest boronization session, gas mixture of deuterium and helium was used in glow discharge instead of helium only to reduce the hydrogen content in the boron film. On the other hand, the B/sub 4/C-converted CFC tiles caused, so called, the real-time solid target boronization (STB) by plasma impact, and then low concentration level of impurities was achieved. Water cooling of the divertor tiles, which was carried out in October 1994, was also effective for the reduction of impurity production. The amount of neutron and tritium generated by the D-D reaction have also increased with the improved plasma performance. From the measurement of the tritium in the first wall tiles, it is expected that tritium of 1.6/spl times/10/sup 10/ Bq, which corresponds to approximately 50% of tritium generated until 1993, still remained in the first wall.