The off-state conductance of a standard heat switch is approximately 37µW/K at a temperature of 4K. Heat switches are extremely delicate and cannot be used to provide mechanical support, indeed they MUST not be used in that way. For this reason we do not measure or specify the compressive and tensile strength. So far as
While it is possible to use different materials for the switch case, it can cause difficulties with the joining materials, thermal expansion and permeability to helium. These factors increase the expense of manufacture.
Activation (turning the switch ON) typically takes around 1.5 to 2.5mW of heater power, depending on the design requirements. This heat is usually dumped to the fixing point at 4K, as the transition temperature (ON/OFF) is around 15 to 20K.
Thermal conductivity in either the ON and OFF state of a heat switch is affected by temperature - the thermal conductivity of stainless steel and helium gas varies with temperature. Importantly, steel will determine the OFF-state conductivity, and helium gas the ON-state conductivity. Conductivity will also be affected by the switch's geometry. A typical standard
We make bespoke gas-gap switches as well as some standard types. The standard units are 2.5” (63.5mm) long and are usually mounted upright, but can operate in any orientation. Bespoke types vary in length depending on the application requirements. To design a bespoke switch, we need to know the customer's thermal requirements for the OFF-state
Our most recent iteration of the mini-dilutor, tested on a powerful single-shot He7 precooler, achieved a base temperature of around 65mK. We are currently testing whether this dilution module will run satisfactorily with a continuous CC7 precooler. We hope that it will run at 100mK under at least 3µW of applied power. There should be
Please watch our videos online to understand how our coolers work. Our continuous sub-Kelvin sorption coolers are designed to run from a PTC or GM type mechanical cryocooler. The continuous cooler has two sets of modules alongside a condenser module. A CC4 has two sets of GL4 modules, and a CC7 has two sets of
Click here to view "Work below 300mK", a video about how the GL7 works. The GL7 has a mainplate that interfaces to the cold head of a mechanical cryocooler. The GL4 has just one module, whereas the GL7 has two. The larger of the modules contains Helium-4, and the smaller module contains Helium-3. The GL7
Our sorption coolers are quite small and we are actively working to minimise the thermal load imposed on the 4K cryocooler stage. We aim to keep the cryocooler thermal demand to a minimum. An RDK101 with 100/160mW of cooling power is adequate for a GL4 or small GL7. For a CC4/7 a PT 405 or
There are a number of ways to interface a CRC cryocooler into your cryostat, depending on your experiment and cryostat design. The picture on the right below shows a cryostat with a GM cooler mounted to one side and the CRC cryocooler mounted through the 4K plate. The pumps are in the 40K space,