Orientation of Quadrant Diode for Wave Front Sensing

Abstract:: In current LIGO I interferometers, quadrant diodes for wave front sensors (WFS)
are oriented in such a way that the lines (i.e. gaps) between the segments forms “X”
instead of “+” pattern. The segment 1 and 3 are used for YAW degree of freedom,
while the segment 2 and 4 are used for PIT. Though at a first glance it looks as if there
are no fundamental difference between “X” and “+” configuration, “X” is more prone
to the crosstalk between YAW and PIT. There are other things, like DC centering
annoyances for human operators. All in all, there’s no reason to prefer “X” to “+”,
and there are some reasons to hate “X”. We should not use “X” configuration for future
LIGO interferometers

Files in Document:

Notes and Changes:: Migrated document information from the old DCC:
- Full document number: LIGO-T060035-00-D
- Author(s): K. Kawabe
- Document date: 2006-04-04
- Document received date: 2006-05-01
- Document entry date: 2006-05-01

LIGO Document T060035-x0