Development of High Precision Level Gauge for Helium II

1. 研制了一种超导体连续液位计。用锡（涂层）和哈氏合金或分子（衬底）的复合材料作为传感元件。采用溅射法在0.2[mm]的衬底上镀锡。我们研究了3个因素的影响。(1)锡涂层的最佳涂覆深度。(2)最佳工作电流，以消除膜沸腾或爬升超流体引起的误差。(3)给仪表提供工作电流的方式。为了提高测量精度，超导体在正常状态下的电阻要比哈氏合金或分子超导体的电阻大得多。通过对锡镀层深度和工作电流的适当选择，证实了所研制的液位计测量液位精度在1[mm]以内。当锡的表面电阻为3.89[ω /*]，工作电流为120[mA]时，获得最佳效果。精度在0.45[mm]以内。工作电流只在测量完成后才提供。在这些发现的基础上，制作了一个原型液位计。浮子式、超声波式和差压式液位计也进行了测试。浮子式测量仪由于灵敏度过高，重现性差。超声波式仪表需要昂贵的电子设备。没有找到适合差压表的低温、小压差条件的合适材料。

1. A continuous level gauge using superconductor for helium II has been developed. Composite of tin (coated film) and hastelloy or moleculoy(substrate) were used as sensing elements. Tin was coated on substrate of 0.2[mm] by spattering. We have examined the effects of 3 factors.(1)the optimum coating depth of tin coating.(2)the optimum operating current to eliminate the error caused by film boiling or by climbing superfluid.(3)the mode of suppling the operating current to the gauge.To raise the accuracy of measurement, the electric resistance of the superconductor in normal state was made very large compared to that of hastelloy or moleculoy. By appropriate selections of coating depth of tin and operating current, it has been confirmed that the liquid level was measured with accuracy within 1[mm] by the level gauge developed. The best result was obtained when surface resistance of tin was 3.89[OMEGA/*] and the operating current was 120[mA]. The accuracy was within 0.45[mm]. The operating current was supplied only when the measurement was done. A proto-type level gauge was fabricated on the basis of these findings.2. Float-,ultrasonic- and differential pressure-type level gauges have been tested too. The float-type gauge showed poor reproducibility because of too high sensitivity. The ultrasonic-type gauge required too expensive electronics. Any appropriate material matching the condition of low temperature and very small pressure difference for a differential pressure gauge was not found.