3.6 GEM PLC

The PLC (Programmable Logic Controller) on GEM is used to control the vacuum system and to set the apertures.

GEM has two PLCs, one located in the electronics half of the GEM cabin, and the other located on the ground floor level near to the blockhouse door.

To use the PLC, you should press the buttons on either side of the monitor screen. These buttons will then perform the function currently indicated on the monitor screen. 

When changing the aperture sizes, use the arrow buttons to move the focus to the desired point, enter the required number, then finally press ENTER. When all values have been adjusted, then move the collimation. The beam size at the moderator is normally unchanged at its maximum extent of 84mm wide and 90mm high.

If the Polycold is off then it is completely safe and acceptable to do an Emergency Vent, which is much quicker. The standard vent procedure takes a few minutes to warm up the Polycold.

If the PLC screen is dark then press any button to waken it.

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