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Message ID: 5432     Entry time: Fri Sep 16 14:03:53 2011
Author: Paul 
Type: Update 
Category: SUS 
Subject: SRM oplev QPD noise measurement 

 I checked the dark and bright noise of the SRM oplev QPD. The SRM QPD has a rather high dark level for SUM of 478 counts. The dark noise for the SRM QPD looked a little high in the plot against the bright noise (see first attachment), so I plotted the dark noise with the ITMY QPD dark noise (see second attachment). It seems that the SRM QPD has a much higher dark noise level than the ITMY! In case anyone is wondering, to make these traces I record the data from the pitch and yaw test points, then multiply by the SUM (to correct for the fact that the test point signal has already been divided by SUM). I will check the individual quadrants of the SRM QPD to see if one in particular is very noisy. If so, we/I should probably fix it.

Attachment 1: SRM_oplev_dark_noise_vs_bright_noise.pdf  26 kB  | Hide | Hide all
Attachment 2: SRM_ITMY_QPD_dark_noise_comparison.pdf  26 kB  | Hide | Hide all
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