G1 guard slit alignment using 2D detector

Richard Gillilan and Detlef Smilgies
 
slit scatter from guard slit as lined up using I3 ion chamber
slit widths: s1 = s2 = 0.5mm x 0.5mm, 
guard slit: s3 = 0.6mm x 0.6mm
all images taken on a Q4 at about 0.5 m
from guard slit
opened guard slit to 0.7mm x 0.7mm:
horizontal blades are fine now;
top blade still touches the beam
moved s3 up to 0.2mm:
looking good
moved s3 up to 0.4mm:
still good
moved s3 up to 0.6mm:
now the bottom blade touches the beam
best position: s3z = 0.3mm;
(beam stop could still be optimized a bit heightwise)
(although the beamstop already had a diameter
of 4mm, there is still some diffuse scatter
passing by)