[Stefan, Chris, Kiwamu]

We spent some time today at ISCT1 to locate the forest-type noise at around 1 kHz which we saw in the ALS CARM signal (see alog 6900) and also did some hardware works.

We did find a couple of suspicious optics on the table although we are still studying how they pollute the ALS CARM signal. We have stick foam in the mount of every reflective optic on the table to help their mechanical damping ability. The work continues.

Noise hunting at ISCT1

To do noise hunting on ISCT1 we did a speaker technique --- we hooked up a small speaker at the output of the common mode servo while keeping the green beatnote within the PLL's readout range by ezcaservo acting on the ALS_COMM VCO. The ALS CARM noise sounded mostly high frequency-ish although we didn't confirm how exactly high the frequency was. Then we bought the speaker close to every optic to see if they resonate due to the acoustic (positive) feedback at exactly the same frequency as that of the ALS CARM noise. We found a couple of optics which do resonate with the CARM sound. They are :

• ALS-M9
• ALS-M10
• ALS-BS5
• ALS-BS3

We are suspicious about these optics. They may be the ones introducing the forest noise at around 1 kHz. We have stick foam in the mount of every reflective optic to damp unwanted mechanical vibration. We will take another noise spectrum tomorrow to see how this improves it.

SHG mystery

There has been a mystery that somehow the SHG efficiency dropped by  a factor of 4 or so at some point (approximately from 0.5 mW to 0.1 mW level) and it didn't come back to the high value. As a part of the ISCT1 works we inspected the doubling oven to see if there is an obvious clipping or something stupid. However we didn't find a thing. We did the following things:

• A knife edge measurement for measuring the beam sptial jitter of the frequency-doubled PSL light
  • We placed a knife-edge type object to partially block the beam and placed a PD in the downstream. We didn't see forest type structure around 1 kHz. Though it is possible that the electronics noise was so high that it covered possible noises around this region.
• Alignment of the SHG green power monitor PD
• Placement of a razer blade to dump a stray light
• Re-alignment of the SHG oven to maximize the power
  • This didn't help increasing the SHG power.
• Re-adjustment of the oven temperature set point.
  • We ended up a usual set point of 35 deg. No improvements in the SHG power.

After all these works we measured the SHG power again and it was measured to be 0.140 uW which is still low compared with the past. It is still unclear what happened and we are not quite sure how this can be related to the ALS CARM noise.

REFL alignment

To evaluate the residual noise in the PSL frequency we needed a length sensor of the Y arm, namely the interferometer reflection (REFL) RFPD. We started rearranging the optics to guide the REFL beam to the RFPD. The work is ongoing. Currently the REFL beam is dumped. To prevent a damage on the RFPD due to an accidental power increment we need the trigger function of the mechanical shutter working.

Attached are plots of dust counts requested from 5 PM June 26 to 5 PM June 27.

Attached are plots of dust counts requested from 5 PM June 25 to 5 PM June 26.

Attached are plots of dust counts requested from 5 PM June 24 to 5 PM June 25.

Attached are plots of dust counts requested from 5 PM June 23 to 5 PM June 24.

There is a camera on the IR transmission on ISCETY, and the PD is aligned.  

I turned the periscope by 90 degrees, and removed two unlabeled TCS optics that were on the periscope.  (part of the Hartman reference path).  There are still the other optics from that path that need to be removed, and a better beam dump is needed.  

I took the power for the camera from the Green refl camera (the second connector on that cable is a different connector) Filiberto connected the signal to the blue cable on CB7-050-0005, which is now connected to channel B on the lower of the monitors in the front of the control room. It would be good to add a longer focal length lens and an ND filter.  

The reason for adding the camera was that this morning we were locking on a first order mode, but could not tell from the control room.  

8:50 Pablo and Colin to H2 PSL laser enclosure
Corey informed me that he, Virginio and Keita would be working on and off in the end X transmon lab
10:00 Michael R. to H2 PSL laser enclosure
10:54 electric man-lift pickup
well sampling
CP6 filled
Dave rebooted the DAQ for Vincent
1:29 Pablo, Colin, Michael R. and Rick going into H2 PSL laser enclosure
Cyrus took down a network switch, which took down the H1 PSL Beckhoff, H1 PSL video cameras and communication to the dust monitor in the diode room. Switch was rebooted and restored.
all left the H2 PSL laser enclosure

Cyrus, Dave, Jim

Attached a new SSD RAID to h1fw0.  This RAID is to be used for storage of raw minute data that was formerly written to the SATAboy hard drive array in LDAS.  Reconfigured the h1fw0 daqd to write raw minute data to /trend/minute_raw instead of /frames/trend/minute_raw.  Reconfigured h1nds0 to read raw minute data from both /frames/trend/minute_raw and /trend/minute_raw.  The raw minute data in /frames/trend/minute_raw is now in two subdirectories of /frames/trend/minute_raw, and is considered archive data while still being available for viewing via h1nds0.

Note that frame files written to /frames/full, /frames/trend/minute, and /frames/trend/second are not affected by this change.

The benefit of this change is a remarkable decrease in the amount of time required to write raw minute data, allowing it to be written much more often.  Hopefully this will help make h1fw0 more stable, as the daqd process was having difficulty writing files in the time allocated for the task.  The downside is the raw minute data will have to be copied to the archive as the SSD RAID fills up, which is a maintenance task to be performed a few times per year.

Valved-out YBM turbo @ 1600 hrs. -> 4.0 x 10-7 torr*l/sec indicated

I had to do an emergency reboot of sw-lvea-aux0 today at 14:51 local time, to correct some copy-paste induced errors in the config.  The reboot was (unfortunately) the quickest way to restore the working configuration.  It should be functioning normally now.

(Chris, Kiwamu, Stefan)

We roughly calibrated the IR transmitted light (still ASC Quad sum, since Sheila wasn't quite able to finish due to a short earthquake).

Method:

- We sit on the side of the fringe (peak/2) of the IR cavity fringe, which has a pole frequency of 82Hz, i.e. power is proportional to P0/( 1+( f/82Hz )^2 ) .

- This gives a slope  of dP/df = Po/(2*82Hz), i.e. the DC calibration (with P0=250cts) is 0.656Hz/ct (at DC)

- The cavity pole is now complex (since the two freq-mod side bands see different transfer function), but we were too lazy to do this math right, and just stuck in a real zero at 82Hz to compensate the cavity pole. This is good within a factor of 2 above the cavity pole.

The attached plot shows

- Green: Transmitted IR at peak/2, calibrated in Hz/rtHz

- Dashed-Green: RMS of previous one.

- Blue: MC_F, calibrated in Hz. above the x-over (~100Hz) this measures the laser frequency drive

- Mustard: Ey PLL noise, calibrated in Hz (free running Laser noise)

- Gold: EY PDH control signal (actually wong - should be ~10 times higher, due to the changed PDH control scheme - see previous elog for correct calibration)

Conclusion: we supress real motion down to ~40Hz, above that we are imprinting ALS sensing noise (probably from the corner setup) onto the IR light. The obvious strategy to lower the 34Hz RMS noise is to lower the UGH (turn the AO path off) and add some significant boost filters at low frequency. Our initial attempt for doing this ran into DAC saturation issues on MC2.

(Kiwamu, Alexa, Matt, Stefan, from yesterday)

As part of the ALS noise hunting, we revisited the PLL and PDH loops at EY.

- First we realigned the PDH diode that was intentionally misaligned the night before. We verified the the DC oscillations observed on that diode's read-back are not present in analog, so there must be some issue with the acquisition of that signal.
- Next, we looked at the PLL loop. With a UGF around maybe 20kHz it produced a lot of gain peaking around 30kHz. We turned the BOOST stage 1 on the PLL Sigg board off. That helped, but the loop was happiest at another 10dB lower gain.
- This suggested the idea of an "additive offset" like path, bypassing the PLL loop all together. We rigged this control scheme by using one additional BNC cable:
  - We moved the cable that runs to the VCO tune input from the PDH Sigg board fast output to the PDH Sigg board EXC B monitoring point (either 1 or 2 - they have opposite sign). We would like to use the slow path for this option, but it had additional undesired low-pass filtering.
  - We added a cable from the PDH Sigg board fast output to the PLL Sigg board EXC A input. This keeps a high-frequency roll-off as well as some PZT notches in the path.
  - The PDH Sigg board fast gain was lowered from 0dB to -22dB to set the AO gain. The PDH Sigg board input 1 gain was set to -4dB.
  - With this setting we got a nice, roughly 1/f total loop shape, and a UGF of 20kHz.


Our hope was that this configuration will change the noise seen at the end corner, but we had no luck - the corner noise was unchanged.

PS: Attached is a plot of the calibrated frequency noise in Hz/rtHz seen by 3 sensors:
 - Blue: PLL control signal: dominated by free-running laser noise
 - Purple: PDH control signal: above 2kHz this shows coherence with blue (not in figure), indication laser noise. But below 2kHz we seem to be limited by some other PLL sensing noise (electronics dark noise ?) Note that this noise was taken in the old control loop topology, because the control signal calibration was simpler.
 - Red: ALS in-loop common mode error signal from the corner beat node. Note that it is NOT coherent with any of the noise we see at the end.


PPS: We also noted that we are able to grab an arm lock with the PLL input disabled (i.e. without relying on the fiber for per-stabilization). However we would need some more low frequency gain to keep the lock in this configuration.

 

h1lsc and h1iscey front ends were updated yesterday as follows.

LSC:

• Add/change sample rates of DAQ channels.
• Restore in-air IMC TRANS PD's IPC from h1ascimc.  (This is a local mod: at LLO the in-air PD is not installed, and the in-vac MC2 TRANS QPD sum was used instead.  Yet the in-air sensor still exists in the table layout and the ADC/DAC channel allocation.  Also, we won't have an IPC for the MC2 TRANS QPD available until we rebuild h1ascimc.)

ISCEY:

• Add/change sample rates of DAQ channels.
• Hook up the communication link to the Beckhoff/Ethercat slow controls.  The front end uses two bits received from the Beckhoff system to toggle the first two filters in H1:ALS-Y_ARM.  It sends one bit to tell the Beckhoff whether the input beam pointing is good or not.  The Beckhoff PDH autolocker still has to be updated to take advantage of its newly acquired knowledge and powers.

Attachments: (1) ISCEY top level; (2) ALS subsystem showing state/control logic.

For both systems, safe.snap files have been updated and committed to SVN.

Closing WP 4005.

(Betsy W, Gerardo M, Gerardo A. M)
Prism was removed today, finally. It took about 7 days of the common process of soaking the prism joint in acetone, then working on the joint by hand with a razor blade along with some acetone as a lubricant.
2 photos attached, one is where the prism used to be, second photo is the removed specimen.

Per a request of Jeff K, I made an additional update to the TMTS_MASTER.mdl, to add DAQ requests for the 6 ...M1_DAMP_*_IN2 channels. I then rebuilt and restarted h1sustmsy.mdl.

In the process I noticed that there were error messages being generated from the following lines in the safe.snap (these may have been there yesterday, see alog 6883, but I don't recall), so I manually edited the file and removed the second half of each line.

H1:SUS-TMSY_M1_DAMP_P_STATE_GOOD 1 H1:SUS-TMSY_M1_DAMP_P_STATE_GOOD 0
H1:SUS-TMSY_M1_DAMP_R_STATE_GOOD 1 H1:SUS-TMSY_M1_DAMP_R_STATE_GOOD 0
H1:SUS-TMSY_M1_DAMP_T_STATE_GOOD 1 H1:SUS-TMSY_M1_DAMP_T_STATE_GOOD 0
H1:SUS-TMSY_M1_DAMP_V_STATE_GOOD 1 H1:SUS-TMSY_M1_DAMP_V_STATE_GOOD 0
H1:SUS-TMSY_M1_DAMP_Y_STATE_GOOD 1 H1:SUS-TMSY_M1_DAMP_Y_STATE_GOOD 0

Chris Wipf then reported that sometime in the last few days, the setting for the alignment offset gains in the safe.snap had been reset to 1 (whereas they are supposed to be magic numbers that convert mrad of desired offset to counts of actuation). So I transplanted the following lines from an hourly backup from 6/20/13:

H1:SUS-TMSY_M1_OPTICALIGN_P_OFFSET 1 -8.950000000000000e+01
H1:SUS-TMSY_M1_OPTICALIGN_P_GAIN 1 1.583586000000000e+02
H1:SUS-TMSY_M1_OPTICALIGN_Y_OFFSET 1 1.899000000000000e+02
H1:SUS-TMSY_M1_OPTICALIGN_Y_GAIN 1 5.171050000000000e+01

The updated master model and safe.snap have been committed.

Giles report from yesterday's work:

(Travis, Mark, Jason, Doug, Giles)

After leaving the PUM hanging overnight there was no further development of the crack. We then proceeded to re-lock the PUM and hang the ETM to perform modal measurements. Using the autocollimator we measured the longitudinal, pitch and yaw modes. We then setup and optical lever to measure the transverse, bounce and roll modes. Finally we measured the 4 fundamental violin modes. The modal data gathered was:         

Longitudinal    0.656 Hz

Pitch  1.09 Hz

Yaw  1.09 Hz

Transverse 0.656 Hz

Bounce 6.75 Hz (this will be sqrt(2) higher when the PUM is free)

Roll 9.6 Hz (this will be sqrt(2) higher when the PUM is free)

FR  505 Hz

FL  506.5 Hz

BR  506.5 Hz

BL  505 Hz

We finally installed the fibre guards and covered the entire lower stage.