Slow-positron beamline temperature rise reduction at Kyoto University Research Reactor

Abstract

Temperature rises of a reactor-based slow-positron beamline at Kyoto University Research Reactor (KUR) were measured during reactor operation and solenoid-coil excitation. During KUR operation at 5 MW, the temperature of the top of the beamline reached 300 °C. This temperature which is close to the melting point (321 °C) of Cd was used to enhance positron generation. On the other hand, the temperature of the flange supporting the beamline was approximately 50 °C and it was sufficiently low in terms of the strength of the beamline. The temperature of the top of the beamline was successfully reduced to 240 °C by introducing a He gas flow around the vacuum duct of the beamline. Beamline temperatures calculated using a finite element method were in agreement with measured temperatures. Such calculation is useful for future experiments with longer or irregular KUR operation.