3.3 GEM Apertures

The beam size on GEM can be changed by moving the five motorised apertures. This is done by using the PLC.

The final sixth aperture, the 'beam-scraper', can be changed by using the LabView PC. 

The maximum beam size at the sample which can be set is 20mm wide and 40mm high.

The maximum area of the moderator which can be viewed is 90mm wide and 84mm high.

The GEM apertures are described more fully here.

Click here for a schematic of the GEM beamline.

Last updated on 22 Oct 2004 by Alex Hannon (a.c.hannon@rl.ac.uk)