A note on possibly large thermocouple effects from copper instrumentation wires
✍ Scribed by J. Dawson; L.G. Hyman; J. Sheppard
- Book ID
- 103053777
- Publisher
- Elsevier Science
- Year
- 1980
- Tongue
- English
- Weight
- 250 KB
- Volume
- 20
- Category
- Article
- ISSN
- 0011-2275
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✦ Synopsis
has the advantages of a slight improvement in temperature stability together with significantly easier operation and a facility for rapid heating and cooling of the sample. The difficulty of operation of exchange gas inserts arises from the need, if optimum performance is required, to readjust the exchange gas pressure whenever the sample temperature is changed significantly.
A further advantage of the displacer type system is that it dispenses with the need for a vacuum pump during operation. On the other hand a continuous flow system requires a special flow pump to draw cryogen around the system, while an exchange gas system requires a pump for exchange gas pressure control.
All three types of insert may be used with liquid nitrogen for sample temperatures in the range 80 to 300 K. The temperature stabilities are similar to those obtained with liquid helium with the displacer insert again giving the best performance of the three.
Conclusions
The cryostat described allows sample temperatures to be held in the range 2 to 300 K. Its main advantages compared with cryostats containing continuous flow or exchange gas inserts are its ease of operation, low helium consumption at 4.2 K, good temperature stability throughout the whole temperature range, lower cost, and its facility for rapidly cooling or heating of samples if required. Its main disadvantage is that the PTFE displacer must be removed before pumping on the helium to obtain temperatures below 4.2 K.