[Daniel, Stefan, Kiwamu]

 For some reason we frequently failed handing the MC control off to the ALS CARM signal this time around. We checked several things to make sure we are back to the configuration we were in the past Friday. Also we aligned the in-vac picomotors to center the infrared beams on their trans QPDs on TMSY.

Also we took a new noise spectrum without the RGA pump running nearby HAM3, the noise spectrum didn't show a big improvement at around 60-70 Hz in which we thought it would improve.

Besides we did the following things :

• Stefan cleaned up the LSC_CARM filters and rearranged the order of the filters
  • The new filters were then double-checked by a filter archive and switch readbacks.
  • -40 dB gain in LSC_CARM was moved to FM2 of REFL_SERVO_SLOW
• We checked whether if the LSC-REFL_SERVO_COMFILTER was on or off.
  • Confirmed to be off
• We checked the UGFs of the ALS CARM loop both by analog and digital measurements without engaging the AO path in a couple of (slightly) different configuration.
  • The analog and digital measurements agreed with each other in every measurement. This is good.
  • The UGFs was measured in a couple of different settings as we proceed in the handing off script. The UGF could go to 300 Hz with a phase margin of 10 degrees.
  • We confirmed that once the AO path was introduced the phase margin got significantly improved so that it can be more than 30 degrees.
• We suspected that some sort of saturation made the loop instable
  • We monitored the feedback signals applied on the bottom two stages of MC2, but we didn't find an evidence of the saturation
  • When we didn't close the ALS CARM loop the individual loop seems running fine.
• There was a time band at around 21:30 PDT where we had periodical lock losses with a period of about 1-2 minutes.
  • According to the seismic striptool displayed in the control room, there was big disturbance in end Y and end X in a frequency band from 30 mHz to 100 Hz. This might be an earthquake.
  • After a couple of 10 minutes we became able to lock the ALS CARM
• We centered the beams on the infrared trans QPDs
  • There was an apparent improvements in the noise spectrum at around 1 Hz and all the mechanical structure we had had were gone.
  • However several hours later we found that these mechanical structure came back in the spectrum. Since the arm cavity alignment was good, this might be a usual angle to transmitted light coupling.
• Refcav became unable to capture a fringe for some reason
  • We tried tweaking some temperature scanning parameters, but this didn't help
  • After a couple of 10 minutes the refcav came back to normal operation by itself
• We found a sharp peak in the ALS_COMM VCo monitor analog channel at 171 kHz.
  • This is something Daniel unexpectedly found when he was checking out his electronics around the vertex electronics racks
  • The peak moves as we changes the frequency of the ALS_COMM. It is unclear where this signal comes from.
  • This sharp signal shows up only when the ALS beatnote signal presents.
• In the early evening the BS oplevs were found to be off by a lot (~ order of 10 urad)
  • This was found to be due to the BS HEPI. The BS HEPI was off.
  • We tried to turn the HEPI on by an automated command, but this didn't work --- this tends to trips the watchdogs for some reason.
  • We ended up manually turning each servo on --- we tuend on ISO_X, ISO_Y, ISO_RZ. ISO_HP, ISO_Z
  • This brought the IPS signals approximately to where they were in the last week.
  • A fine tuning of the green transmitted light path was done by tweaking the BS top stage bias.