The measurement head device null in the critical thermometry machine of the super-conductivity

摘要

PURPOSE:To eliminate the repetitive labor for changing a measuring head and to decrease generation of errors by mounting a Meissner effect detector and a 4-terminal method resistance measuring instrument oppositely to measuring stages above and below a cold head. CONSTITUTION:The 4-terminal method resistance measuring instrument is mounted to the lower stage 2 of the cold head 1 of a small-sized refrigerator utilizing the adiabatic expansion of helium and the Meissner effect detector 13 is fixed to the rear face of the upper measuring stage 10. The instrument and detector are connected to a switching device for external operation. A sample 8 is set in a measuring part and is cooled to a prescribed temp. at the time of measuring the critical temp. Current is then passed to the 4-terminal method resistance measuring instrument and the resistance value is determined. The device is then switched and AC is passed to the Meissner effect detector 13 to detect the Meissner effect. The second labor for replacing the head is thereby eliminated and the release of the cooling during the course of the measurement is eliminated, by which the errors are decreased.