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Message ID: 9816     Entry time: Wed Apr 16 01:51:16 2014
Author: Jenne 
Type: Update 
Category: LSC 
Subject: Scripts written for ALS acquisition, CARM and DARM transitions 

[Jenne, EricQ]

This evening, as part of locking activities, we threw together some handy scripts.


The first one, "Lock_ALS_CARM_and_DARM.py" (no judging of my naming style!!), lives in .../scripts/ALS/ . 

It acquires ALS lock in CARM and DARM mode, so we don't have to do it by hand anymore.

The first thing that it does is ask you to acknowledge that your beatnotes are in place, and they follow our new (newer than the last elog about conventions) beatnote convention.  You are reminded in the terminal window what that convention is:  When the temperature sliders for either arm is INCREASED, the beatnote frequency should INCREASE. 

After you acknowledge that the beatnotes are good, it sets the CARM and DARM servo gains to zero, enables the outputs, sets the input matrix elements, clears the phase tracker histories, and starts ramping up the gains (with +1,+1 for DARM, the darm servo gain is +positive.  with -1*ALSX,+1*ALSY for CARM, the carm servo gain is -negative).  At a gain of 3, it engages the integrators and the resonant gains.  At the final gain of 6, it engages the boosts.

We have used this script ~10 times tonight, and it's been great every time.


The next two scripts are for making the transition from ALS to IR signals.  They both live in ..../scripts/PRFPMI/

"Transition_CARM_ALS_to_TransSqrtInv.py" (again - no judging!) slowly blends the input matrix elements to swap CARM control from the ALS signals to the 1/sqrt(trans) signals.  It takes a few steps, and asks for a keyboard input between steps.  This is because if our 1/sqrt(trans) offsets aren't perfect, we can start to lose transmission power.  To mitigate this, we decrease the offset in the CARM servo filter bank to get more power back.  This script requires an input, which is what you want the final sqrtinv matrix elements to be.  It will fail without this.  For a CARM offset, both of the final sqrtinv matrix elements will have the same sign.

"Transition_DARM_ALS_to_AS55.py" (I can telepathically hear you judging me right now.)  does the same blending, except to swap DARM control from ALS signals to AS55Q.  For the same reason of imperfect offset-setting, it takes several steps, to allow you to adjust the CARM offset if needed. Although, after typing this, I realized that perhaps we should have been tweaking the DARM offset.  Either way, this transition required much less tweaking of offsets than the CARM transition did.  Again, the script requires an input, which is your final desired AS55Q->DARM matrix element value.

Both of these scripts should be run at a digital CARM offset of about 2 counts, although with the offset tweaking during the CARM transition, I usually end at about 1.5 counts. 

*  To determine the final gain value for the CARM sqrtinv matrix elements, we have been using a spare filter bank (ex. XARM), and having the input to that be the sum of the sqrtinv channels.  We then put in a CARM line, and look at the transfer function between the temporary filter bank's input, and the CARM_IN1. 

*  To determine the final gain value for the DARM AS55 matrix element, we have been doing a similar thing, looking at the transfer function between DARM_IN1 and AS55Q with a DARM line on.  We have been putting this DC gain into the static PD normalization (4th block from the left on the big LSC screen), although with the new script, it will be easier to just put that value into the matrix element.

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