aLIGO LHO Logbook

H1 ISC

sheila.dwyer@LIGO.ORG - posted 17:37, Friday 29 March 2013 - last comment - 10:56, Monday 01 April 2013(5936)

ALS PLL working

Richard cleaned the fiber this morning at the Y end patch panel, and after that we had 18-19uW at the table feed-through and I measured 14uW with the power meter in air on the table.  After realigning for the swapped beamsplitter, (and re-aligning the power monitor PD) the beatnote was -38dBm, around -20 dBm after the amplifier.  

A plot of the OLG will follow,  but the main message is that the ALS PLL is working.  It has been locked for almost hours now, based on looking at the striptool of the beat frequency and the control signals.  

The settings are: cg -15, fg 22, common compensation on, slow ugf set to -0.015Hz and slow pole set to 0.0001 Hz. 

The beatnote frequency has glitches that are not present in the channel for the VCO frequency, where the signal level is much higher.  It might be easier to write an autolocker if we could get rid of those glitches, perhaps by amplifying the signal.

Comments related to this report

sheila.dwyer@LIGO.ORG - 20:38, Sunday 31 March 2013 (5944)

Link

Chris, Max, Sheila-

Before Richard cleaned the fibers, Chris and I measured the power in the fibers at a few different places:
Input to fiber distribution box in R4: 1.2mW 
Y end output of fiber distribution box: 75 uW
Max's polarization box: 60uW
Output at Y end patch panel: 10uW
At ALS table feedthrough:10uW
on ALS table at fiber output-approx 10 uW

Also the OLG of the PLL with the settings above is attached.

Non-image files attached to this comment

OLG.fig

sheila.dwyer@LIGO.ORG - 10:56, Monday 01 April 2013 (5947)

Link

I changed the ALSLaser library, so that the polarity between the slow loop and fast loop is correct when the ugf setting for the slow loop is positive.  

Also, when I came in this morning the PLL was still locked and looked like it had been for the last 10 hours.