J. Kissel, A. Pele (WP #5025)

We are to make the IFO's fast shutter functional within the next week, in order to prepare and protect the OMC DCPDs from the energy leaked from a FULL IFO lock lock. In its current design / implementation, this shutter is fast and loud as it closes and reopens, which sends large impulses to the optical table on which it sits (in this case H1 ISI HAM6). In order to prepare for this "toaster" being activated, I've increased the number of consecutive saturations (computer cycles above the user-predefined threshold) that are acceptable for the H1 ISI HAM6 GS13s and Actuators before its watchdog trips to 4096 [samples] / 4096 [Hz]= 1 [sec] and 8192 [samples] / 4096 [Hz] = 2 [sec], respectively (where it had previously been 10 [samples] / 4096 [Hz] = 0.0024 [sec] for these channels). See attached screenshot of the relevant WD block innards.

This has been done and in place at LLO for a few weeks with no obviously adverse affects, (see 16430 and 15998), we were merely replicating their change. As such, they've seen a drastic reduction in HAM6 ISI trips after lock-losses, and we hope to see the same benefits. 

Note, the change involves *unhooking* (disabling and breaking) the 
/opt/rtcds/userapps/release/isi/h1/models/h1isiham6.mdl 
model link to the generic HAM ISI model library part
/opt/rtcds/userapps/release/isi/common/models/isihammaster.mdl
and replacing the WD_SAFE_COUNT tag input to each GS13 and ACT blocks (inside the HAM6 WD block) with hard-coded constants of 4096 and 8192. 
I've committed the unhooked model to the repository.

For the restart, I
- Brought the OMC suspension to SAFE
- Turned off all output to OMs 1-3
- Asked the SEI_HAM6 manager to take the chamber to DAMPED
- Paused the SEI_HAM6 manager (to make sure ISI_HPI is left alone and happily running)
- Changed the ISI_HAM6 subordinate to exec
- Requested ISI_HAM6 subordinate to READY
- Turned OFF ISIHAM6's master switch 
- Recompiled, Reinstalled, Restarted h1isiham6 front end process on h1seih16 computer
- Requested ISI_HAM6 subordinate to DAMPED, confirmed IOP output
- Changed the ISI_HAM6 subordinate back to managed
- Changed the SEI_HAM6 manager back to exec (who came back, happily fooled that it never left the DAMPED state)
- Requested SEI_HAM6 manager to return to ISOLATED.
- Restored OMC suspension to ALIGNED
- Restored alignment and damping to OMs 1-3 (and a random Y offset of 2000 [ct] on the TEST filterbank).
Note, also, since I merely changed constants in the model, the change did NOT require a DAQ restart.
I also attach trends of the P and Y of the HAM6 suspensions (as measured by their local OSEM sensors), confirming that they've been restored to the same alignment.

Loaded the updated tidal code into iscex/y.

I will be doing some work on the connection between CDS and GC this morning which will result in some brief interruption to access to CDS from the outside world (and vice versa).  This includes any services hosted at lhocds.ligo-wa.caltech.edu.  A follow up entry will be posted when work is complete.

Zero'd the Match gains starting at 1549utc.  Jim reports the X leg of the sensor dropped by ~1/2 on 23 Dec when it appears the zero button was pressed.  We will press it again to see if that might bring it back.  I can't find a log of a button press but we had been struggling to get that STS2 signal down to reasonable levels.  We're not sure this will work but we'll see.

model restarts logged for Mon 26/Jan/2015
2015_01_26 00:02 h1fw0
2015_01_26 04:29 h1fw1
2015_01_26 05:28 h1fw1

all unexpected restarts. Conlog frequently changing channels report attached.

Switched to manual control at 1510utc.  Made one setpoint tweak at 1514.  It looks like it will probably run without further adjustment (maintaining the ~70psi differential pressure) for a hour or more.

Alexa, Elli, Sheila, Rana, Evan

Today we worked some more to make the sqrt(TRX+TRY) handoff more robust.

Now we can pretty reliably complete the transition by hand. We are working on implementing the transition in the guardian.

We have tried to reduce the CARM offset while locked on sqrt(TRX+TRY), but we cannot seem to get beyond 2 or 3 times the single-arm power without blowing the lock. The next step is to go through the CARM reduction sequence more carefully and characterize the OLTF of the CARM loop in this state.

Gain redistribution

As discussed in LHO#16252 et seq., we suspect that the common-mode board has gain-dependent offsets. If this is true, it explains why the interferometer can be knocked out of lock while ramping down or turning off ALS COMM.

To boost the CARM loop's immunity to these offsets, we redistributed gains as follows:

• The gain of the ALS COMM input on the common-mode board was increased from −4 dB to +16 dB (LSC-REFL_SERVO_IN2GAIN). Correspondingly, the gain on the AO into the IMC board was reduced from +16 dB to −4 dB (IMC-REFL_SERVO_IN2GAIN).
• The input matrix gain for the slow path out of the IMC board (going into the digital CARM control) was decreased from 1 to 0.1 (LSC-PD_DOF_MTRX_5_26).
• The digital gain for sqrt(TRX+TRY) was increased by a factor of 10 (LSC-REFLBIAS_GAIN was increased from 0.8 to 8).

Even with these changes, success is not guaranteed. The gain steps can be heard very clearly when listening to LSC-CARM_IN1, and turning off ALS COMM on the summing board will blow the lock about half the time. We can get better results by using the gain slider on the common-mode board, but we can still hear the gain steps.

Modified handoff procedure

• In LSC-REFLBIAS, we engage FM3 (1 Hz pole, 40 Hz zero) and FM9 (1.6 Hz pole, 40 Hz zero). The gain is 8 ct/ct.
• In LSC-TR_CARM, we set the offset to −0.5 ct.
• We engage the sqrt(TRX+TRY) path on the common-mode board.
• We engage LSC-REFL_DC_BIAS with a gain of 30 ct/ct.
• Once the buildup has stabilized, we turn on FM6 (0 Hz pole, 1 Hz zero). Then we turn on FM4, which undoes FM3. Then we ramp the gain of LSC-REFL_DC_BIAS to 50 ct/ct.
• We ramp down ALS COMM using the common-mode board input gain slider. Then we turn off this input on the common-mode board.

A lockloss plot is attached for an unexplained lock loss during the CARM offset reduction after handing off to sqrt(TRX+TRY). Other lock loss times, all 2015-01-27 UTC: 03:56:53, 04:05:25, 05:36:16, 06:40:59, 07:56:02, 08:37:20. The last four are during CARM offset reduction after the handoff is complete.

For a sqrt(TRX+TRY) offset of −1.5 ct, the gain we need for REFL_DC_BIAS is 50 ct/ct. Our OLTF looks good here. However, when we reach an offset of −2, we seem to lose lock, even though there is no obvious nastiness in the CARM spectrum.

Mystery

Today, locking DRMI without arms was pretty painless. In contrast, DRMI+arms lock acquisition was very, very slow for most of the morning and afternoon. After about 5pm local, it became painless as well. This may have been correlated with our changing the trigger settings to be twice as high with arms (compared to no arms), since the POP18 buildup is twice as high. But we haven't investigated this systematically.

Similar to the HEPI's done last week, I took the text file generated by Barker, which is extracted from the Guardian logs, and removed the truncated channels from that list.  The MASTERSWITCH was also added to the list.  This I used for the do not monitor channel list.  I saved this file with the safe.snap files in /opt/rtcds/userapps/release/isi/h1/burtfiles.

Next the safe.snap is modified to include the monitor bit on all channels not RO and not fields.  This is then loaded into the FE with the LOAD TABLE ONLY button.

After confirming a successful load and noting the DIFF list, the safe.snap is then modified with the donotinclude list.  When theTABLE is LOADED again, most of the diffs go away and the remaining differences represent the differences we care about wrt most recent safe.snap file.  Either the channel is set wrong or the snap needs updating.

All HAM-ISI are good except HAM3, there remains some blend diffs as we test configs for the 0.6hz  peak issue.

I'll work on the BSC-ISI soon.

This exercise exposed a problem: if you have more than 40 diffs, it only shows 40 and it only lists 40.  It makes you think there is only 40 when there are more.  I've filed bug 796.

07:50 Cris to EX

08:00 Karen to EY

08:48 Bubba & Co to EX - no VEA

09:15 Karen leaving EY

09:21 Fil out to HAM 2 area for video work.

09:54 R Savage out to LVEA to look at viewports

10:00 Ron Carlson contractors on site for R McCarthy

10:02 Corey and Rick out of LVEA

10:29 McCarthy out to HAM6 area w/Daniel approval

11:03 McCarthy out of LVEA

11:09 Corey back out to squeezer bay to look for parts w/comm approval

13:40 Gary Traylor into the optics lab.

15:50 Gary out of optics lab

10:00AM Guidline in effect for Commissioning starting today.

SEI - work on installing blend filters from LLO on HAM3

SUS -  working on SDF

CDS - video work around HAM2. Microphone problem is fixed.

3IFO - no work in te LVEA this week and will be postponed for some time.

Corey moving things in Squeezer bay.

Beam Tube Cleaning to resume today on X arm - Apollo on site.

Sudarshan mentioned a desire to work on P-Cal at EX and EY

Nutsinee reporting to LHO for operator position

Thomas Abbott visiting. Will be helping with Drift monitor/ P-Cal etc

The ITMY OPLEV SUM has been oscillating with 10min-ish period for a while. Apparently YAW picks this up with 3urad pp amplitude, making it unusable as an angle monitor (first plot).

It's getting worse slowly. On Tuesday the oscillation was there but it was about 1urad pp (2nd plot).

Something happened  on  Wednesday afternoon and the SUM dropped by a factor of 2 (third plot), but it's not like the noise  didn't jump jumped up right after that event.

Though this is not blocking the locking activity, II asked Doug if he can swap the laser during maintenance. If not, he might try early morning on Wed. or Thu.

Elli, Sheila, Alexa, Rana, Evan

Since we haven't been able to reliably transition ALS COMM to sqrt(TRX+TRY), we decided we'd back off a bit and try the transition with a single arm only (i.e., no DRMI).

The sequence that we found worked for us is as follows:

• Adjust the ALS COMM VCO offset to −100 Hz_green.
• Engage the sqrt(TRX) path with a 1 Hz pole and a 40 Hz zero, an offset of −0.7 ct in TR_CARM, and an overall TR_CARM/REFLBIAS/REFLDCBIAS gain of 80 ct/ct. The common-mode board has an input gain of 0 dB (ALS COMM has an input gain of −4 dB). Addtionally, we have the usual filters engaged in TR_CARM/REFLBIAS/REFLDCBIAS:
  • a 1 kHz pole and a pair of complex zeros at 35 Hz (with a Q of 1) which are meant to make sqrt(TRX+TRY) fall off as 1/f out to high frequency
  • a 1.6 Hz pole and a 40 Hz zero which imitates the response of the ALS COMM VCO.
• Turn off the COMM VCO frequency servo. Tune the VCO voltage so that the sqrt(TRX) output (as monitored via REFLDCBIAS_OUT) is close to zero.
• Engage a 0 Hz pole and 1 Hz zero in the sqrt(TRX) path, so that sqrt(TRX) has a true integrator.
• Turn off the ALS COMM PLL boost (pole at 1.6 Hz, zero at 40 Hz).
• Ramp down the analog gain of ALS_COMM on the summing node board to −32 dB. Then switch off the input.

For most of this process we had a GPIB-controlled SR785 hooked up to the common mode and summing node boards in order to monitor the relative strengths of the ALS COMM and sqrt(TRX) signals. For the excitation we drove EXC A on the common-mode board; for ALS COMM we monitored TEST1 on SUM A, and for sqrt(TRX) we monitored TEST2 on SUM A. This was incredibly helpful for sorting out how to properly shape sqrt(TRX) and how to engineer a stable crossover during the transition.