3.7 The GEM Polycold

The Polycold is a device installed in the GEM sample tank which is used for achieving the best vacuums. Gases in the tank, such as water vapour, condense onto the Polycold's cold head, and in this way the pressure in the tank is lowered. The cold head must be warmed up to room temperature before the sample tank is let up to atmospheric pressure. This takes approximately 5 minutes and is part of the normal vent procedure controlled by the PLC.

If you do not need the best possible vacuum then you may prefer not to waste time waiting for the Polycold's cold head to warm up. In this case you can turn off the Polycold and then you can let the vacuum up more quickly by using the "Emergency vent" option on the PLC. The Polycold controller is located on GEM's ground floor level. If you want to turn the Polycold off, then it must be set to local (see picture). If you turn the Polycold off, then please note that you have done this in the GEM logbook.

Fig. The Polycold Controller

Fig. Polycold Controller Settings

Last updated on 28 Jul 2002 by Alex Hannon (a.c.hannon@rl.ac.uk)