Reports until 03:40, Tuesday 12 April 2016
H1 PSL (PSL)
peter.king@LIGO.ORG - posted 03:40, Tuesday 12 April 2016 (26538)
Pre-modecleaner status
The power incident on the pre-modecleaner was increased from ~30W to ~138W.
The power transmitted by the pre-modecleaner, as measured by a power meter
located right after the pre-modecleaner, was ~123W.  This is consistent with
the visibility measurement conducted last week.

The transfer function for the low and high power modes are similar.  In the
high power mode, the unity gain frequency was ~6 kHz with a phase margin of
~ 80 degrees.

There is a problem with the transmission photodiode.  Whilst the filter
file for the photodiode appears to be okay, the output of the photodiode is
not consistent with the amount of incident light.  For the factor of ~4
increase in light power we observed an increase of less than 1 in the
photodiode output.  This problem does not show up in the low power mode.
The photodiode was given a cursory inspection and appears to be okay.  The
signal cable was temporarily swapped but made no difference.

This is a 2mm InGaAs photodiode (D1002929).  I suspect one of the voltage
regulators is sporadic.  Perhaps the LM317S providing the bias voltage.
This will be checked later today.

Jason, Peter
Images attached to this report