CryoTigers

We have had continuing problems with the CryoTigers, both warming up over a relatively short period of time and a bi-stable nature of the cold-head temperature. When the cold-head temperature is relatively high ($\sim$-160$^{\circ}$C in the case of FIES), the system has problems keeping the CCD at the normal operating temperature.

One way has been found to recover from the cold-head temperature being relatively high. If the CryoTiger has been on for at least a few hours, being stable at the high temperature, switch it off for approximately half hour then on again and the temperature usually drops to the correct operating temperature of $\sim$-199$^{\circ}$C. This trick has work for both the StanCam and the FIES systems, but it is not understood why.