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de la Cruz, F., and O. J. Bressan. "Sensitive Hot Wire Level Detector for Cryogenic Liquids." Review of Scientific Instruments 40, no. 3 (1969): 483–486.
Abstract: A very simple and highly sensitive ``hot wire'' type level detector to be used with cryogenic liquids is described. The hot filament is made of tungsten wire of about 4 µ diam. The tests on the sensor were made moving the filament in and out of the quiescent surfaces of liquid helium and nitrogen. The results showed 0.006 mm sensitivity in the determination of liquid helium level and 0.002 mm sensitivity in the case of liquid nitrogen level. The sensor is assembled in such a way that it can be used without special precautions during indefinite periods of time. For the case when the full capabilities of the sensor are not necessary, a simple circuit is presented.
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de la Cruz, F., M. D. Maloney, and M. Cardona. "Variation of the Ratio Hc3/Hc2 in the Immediate Vicinity of ${T}_{c}$." Physical Review 187, no. 2 (1969): 766–767.
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Mota, A. C., R. P. Platzeck, R. Rapp, and J. C. Wheatley. "Experimental Heat Capacity of Pure Liquid He3." Physical Review 177, no. 1 (1969): 266–271.
Abstract: Measurements of the heat capacity of pure He3 at 0.24 atm obtained by a differencing method are presented for the temperature range from 20-150 m°K. The temperature scale T* used is that valid for powdered cerium magnesium nitrate in the form of a right circular cylinder with diameter equal to height. There is excellent agreement between the present and earlier measurements. Considering all low-pressure difference data we find that from 6-125 m°K the ratio of heat capacity to magnetic temperature decreases linearly with increasing temperature. The relationship of the measurements to the temperature scale and to theories of spin fluctuations in He3 is also discussed.
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