Status of tandetron II of Nagoya

The General Center for Age Measurement, Nagoya University, introduced an accelerator mass spectrometer of Model 4130-AMS made by HVEM Co., the Nether lands on 1996. We had spent almost 9 months from February to October 1999 for trouble shootings, repairs and adjustments. The followings are major troubles. Diode array were damaged after an acceptance test due to sparks. The 366 diodes were broken among total 1422 (24%). The 14 resistors were broken among total 158 (9%). HVEM Co. said there was the initial defect in manufacturing diodes. We replaced all diodes and resistors, after waiting 1 month. The insulation resistance of transformer coils went down by sooty contamination by sparks and coils were burned out. The 3 weeks were needed for replacement of coils. Perfect cleaning inside the tank vessel was very complicated. The phase detector of the magnet power supply was broken and resulted in sparks of the circuit breaker. Malfunction of vacuum valve appeared after long time shut down of facilities. We had to replace the vacuum valve due to elastic o-ring damage. The aluminum dust caused by target holder carousel caused short circuits. The nails and springs were deteriorated. After all, the modified new target holder was installed. Malfunction appeared in the slit stabilizer. We replaced two operational amplifiers and made optimization of capacitors. Some other troubles happened in cooling water system, cryogenic vacuum pumping system, air compressor, detector of Faraday cup and so on. After fixing many troubles, we had done age measurements on 805 samples. This means about 115 samples per a month. As examples of measurement, we show the results obtained from IAEA calibration standard samples. We will make further measurements with higher accuracy. Appropriate maintenance and management is the key for steady servicing. (Y. Tanaka)