On the behaviour of a helium cryostat for the measurement of the magnetic susceptibility by the faraday method

Jan Vansummeren, Adolf Van den Bosch

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    A metallic helium cryostat has been constructed. It is adapted to an apparatus for the precise measurement of the magnetic susceptibility by the faraday method. Van de Bosch, Vacuum Microbalance Techniques 5, 77 (1966). Its refrigerant vessel has a capacity of 1.9 litre. When filled with liquid helium, a sample can be kept at 4.5K for 9 hours. The dewartail fits a 1-inch gap between the pole pieces of a 12-inch varian electromagnet. The copper sample tube is cooled bu the circulation of a cryogenic fluid (helium or nitrogen gas). Needle valves control the fluid stream so that any temperature between 3 and 300 K can be obtained. The sample tube temperature is measured with a calibrated platinum or germanium resistance thermometer. The temperature of the specimen is brought near that of the tube by heat conduction through helium gas, which is used at low pressure in order not to upset the accurate weighing with the microbalance. Different sample suspension configurations were tried. The compromise results for the force detection in a resolution about 3.10-4 dyne and for the Kelvin temperature of the sample in a reproducibility of 0.3% in the whole temperature region. The reference points are the critical temperatures of superconducting niobium, tantalum, indium, and pure lead, tin and thallium. The reference temperatures were sens on the samples by force measurements which were carried out in exactly the same way as those for the susceptibility measurements, with due allowance for the strength of the magnetic field.
    Original languageEnglish
    PublisherSCK CEN
    Number of pages29
    StatePublished - Sep 1972

    Publication series

    NameSCK CEN Reports
    PublisherSCK CEN

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