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User name dalton
Log entry time 16:37:51 on October 24, 2009
Entry number 296461
This entry is a followup to: 296312
keyword=Compton laser polarisation fixed
From the quarter wave plate (the one in the analysis station) scan it was
possible to determine that the problem was with the quarter wave plate
before the cavity (the one that changes the helicity of the photon beam).
Presumably it was over or under rotating when changing from one helicity
to another, leaving a residual component of linear polarisation in the beam.
The most bizarre thing of all: an epics reboot fixed the problem. A
further QWP scan poduced the familiar output.