Improved helium cryostat for a vibrating sample magnetometer

Landee, Christopher P.; Greeney, R. E.; Lamas, A. C.

doi:10.1063/1.1139500

Cited by 14 publications

(1 citation statement)

References 4 publications

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“…Variable-temperature cryostats achieve a constant temperature sample environment by balancing cryogen flow with electrical resistance heating to achieve the desired cryogenic sample temperature. [7][8][9] A thermal exchange gas may be employed to ensure the sample temperature is uniform. The idea is to have the sample in thermal equilibrium with the exchange gas which in turn is in thermal equilibrium with the cryostat.…”

Section: Introductionmentioning

confidence: 99%

A Simple Dewar/Cryostat for Thermally Equilibrating Samples at Known Temperatures for Accurate Cryogenic Luminescence Measurements

Weaver

Jagow

Portune

et al. 2016

JoVE

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The design and operation of a simple liquid nitrogen Dewar/cryostat apparatus based upon a small fused silica optical Dewar, a thermocouple assembly, and a CCD spectrograph are described. The experiments for which this Dewar/cryostat is designed require fast sample loading, fast sample freezing, fast alignment of the sample, accurate and stable sample temperatures, and small size and portability of the Dewar/cryostat cryogenic unit. When coupled with the fast data acquisition rates of the CCD spectrograph, this Dewar/cryostat is capable of supporting cryogenic luminescence spectroscopic measurements on luminescent samples at a series of known, stable temperatures in the 77-300 K range. A temperature-dependent study of the oxygen quenching of luminescence in a rhodium(III) transition metal complex is presented as an example of the type of investigation possible with this Dewar/cryostat. In the context of this apparatus, a stable temperature for cryogenic spectroscopy means a luminescent sample that is thermally equilibrated with either liquid nitrogen or gaseous nitrogen at a known measureable temperature that does not vary (ΔT < 0.1 K) during the short time scale (~1-10 sec) of the spectroscopic measurement by the CCD. The Dewar/cryostat works by taking advantage of the positive thermal gradient dT/dh that develops above liquid nitrogen level in the Dewar where h is the height of the sample above the liquid nitrogen level. The slow evaporation of the liquid nitrogen results in a slow increase in h over several hours and a consequent slow increase in the sample temperature T over this time period. A quickly acquired luminescence spectrum effectively catches the sample at a constant, thermally equilibrated temperature.

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Section: Introductionmentioning

confidence: 99%