TECHNICAL STUDIES ON REPARATION AND CALIBRATION OF PKR251 VACUUM GAUGE ON EAST

In order to obtain real-time and accurate vacuum measurement，a large number of PKR251-type vacuum gauges have been installed on EAST tokamak with complex vacuum systems，but inaccurate，even wrong measured results were always observed after long and continuous run of EAST.This paper describes a technique for the repair and calibration of a PKR251 vacuum gauge to restore this gauges with inaccurate or wrong measurement by decontamination（replacement），cleaning and baking of key components，including internal electrodes，plates.To stimulate the EAST vacuum condition，a calibration platform was built which could adjust the vacuum pressure by changing the flow rate of high-purity nitrogen injection into the vessel of this system.After the accuracy of measurements is reported by comparing the readings of individual gauge and the standard，the gauge calibration is finished.It was found that the measurement of repaired gauge fitted well with the standard at different pressures and they could be used again by EAST.This repair and calibration technology can effectively extend the service life of PKR251 gauge，supplying the technical support for energy conservation and environmental protection in nuclear fusion experiments.