1. Helium-4 or Helium-3 evaporation
1.1 Physical principle
Evaporative cooling is undoubtedly the most widespread technique: it's a universal method, practiced by all human beings and many animal species. In fact, it's the same physical mechanism that enables us to regulate our body temperature: perspiration. In this case, the passage of water from the liquid to the vapor state requires energy; in the absence of an external source, this energy is drawn directly from the thermal agitation of atoms and, consequently, this process induces cooling. This property extends to virtually all fluids and, when used with helium, enables temperatures below 1 K to be achieved. Obviously, to improve process efficiency, the evaporation rate is increased by pumping. The physics involved are linked to the states of the fluid, which in...
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Helium-4 or Helium-3 evaporation
Bibliography
Websites
DRTBT School online resources (CNRS/CEA) http://www-ecole-drtbt.grenoble.cnrs.fr
Patrick Pari's notes on dilution cryostats are particularly useful. They contain a wealth of information on the dimensioning and design of these systems.
Patents
Dilution Cryostat EP 0188976 B1
Portable helium 3 cryostat US 4136526 A
Cryocooling apparatus and process WO 2013021217 A2
Dilution refrigerator with sample holding device EP 0675330 B1
Refrigerator and process for producing very low temperature cold EP 2307823 B1
Directory
Manufacturers – Suppliers
Janis Research Company, Inc, United States https://www.lakeshore.com/
Leiden Cryogenics, The Netherlands http://www.leidencryogenics.com
Advanced Research Systems, Inc, United States
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