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Entry  Mon Jan 16 21:03:47 2017, rana, Summary, IOO, MCL / MCF / Calibration c1ioo_zoom_MCLF.pngMCL.pdf
    Reply  Wed Jan 18 12:34:21 2017, ericq, Summary, IOO, MCL / MCF / Calibration 
       Reply  Wed Jan 25 18:18:08 2017, Koji, Summary, IOO, MCL / MCF / Calibration 
    Reply  Fri Mar 24 12:21:27 2017, gautam, Summary, IOO, MCL / MCF / Calibration 6x
       Reply  Mon Mar 27 12:48:36 2017, rana, Summary, IOO, MCL / MCF / Calibration 
          Reply  Mon Mar 27 22:40:44 2017, Koji, Summary, IOO, MCL / MCF / Calibration 
Message ID: 12723     Entry time: Mon Jan 16 21:03:47 2017     Reply to this: 12732   12905
Author: rana 
Type: Summary 
Category: IOO 
Subject: MCL / MCF / Calibration 

Oot on the streets and in the chat rooms, people often ask, "What is up with the MC_F calibration?".

Not being sure of the wiring in the c1ioo model, I have formed this screencap of today's model and put it here. The MC_LENGTH and MC_FREQ are the filter banks which would calibrate these channels. In the filter banks there were various version of a 'dewhite' filter. They were all approximately z=150, p=15, g =1 @ DC, but with ~1% differences. I don't trust their provenance and so I've enforced symmetry and fixed their names to reflect what they are (150:15). I have also turned on one filter in MC_FREQ so that now the whitening of the Pentek Interface board is compensated.

Why is this TF 1/f? It should be -20 dB/decade if MC_F is in units of Hz* and MCL is a pendulum response. Perhaps its because the combination of the Koji summing box, the Thorlabs HV driver, and the Pomona box forms an additional 1/f ? IF so, this would explain the TF we see. Once we get confirmation from Koji, we can load the TF into the MC_FREQ filter bank and then MC_F will be in units of Hz (as will the summary pages).

(along the way I've also turned off the craaaazzzy servo input enable tickling that gets put in the MC AutoLocker every April Fool's leap year - resist the temptation)

Since we have a frequency counter system here and some oscillators, I wonder if we can just calibrate the MC_L and MC_F directly using a mixer lashed up to one of the counters. If so, and we can get the stabilized laser frequency noise down below 10 mHz/rHz, maybe this is a viable alternative method to the photon calibrators. Counting zero crossings is more honest than counting photons.

Attachment 1: c1ioo_zoom_MCLF.png  249 kB  | Hide | Hide all
Attachment 2: MCL.pdf  7 kB  | Hide | Hide all
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