Came in to find the laser had tripped, presumably because of the site-wide power glitch.
Brought laser back.  Everything seems to be okay.  However both the reflected power and
the power sum measurement reported by the MEDM screen are out of whack.  It might be that
the power glitch fried the reflected power power meter similar to what happened the last
time power to the site went out - it took out the power meter in the external shutter.
The power sum might be a problem with the photodiode.

    Both might require restoration of the calibration factors from the snap files.

There was a power glitch on site this morning causing all the systems to go down.  Dave Barker is on his way out to restart computers.  We should be back early afternoon.

Matt, Kiwamu

At around 0:30 local, I increased the ring heater power on ITMY from 1.5 W (0.75 W each segment) to 2.5 W (1.25 W each segment) (see 29557 for previous step). This has to be cancelled by applying approximately an additional 400 mW on CO2Y (e.g., pre-heat level of 800 or 900mW).  This step should allow us to better compensate the residual lens observed at 50W.

Matt, Stefan, Terra and Jamie commissioning

Almost 7 hour lock broke around 05:27 UTC in NOISE_TUNINGS. Matt, Stefan and I have not been able to get through ENGAGE_DRMI_ASC since. We are calling it a night.

23:44 UTC Chris driving ITMX at 18Hz
00:13 UTC Chris driving ITMX at 28Hz

Matt, Terra

We have some PLL settings that work for our PI damping.  I've attached a screenshot which shows all of the filter and gain settings for the PLLs.  Since the loop is all digital, the settings of all PLLs should be the same.  The settings shown are for "acqusition mode" where the PLL UGF is about 3Hz.  The PLLs are managed by the Guardian; the integrator (FM3 in FREQ_FILT2) will be engaged when the PLL has found something to follow, and bandwidth will then be lowered (FREQ_FILT2_GAIN = 0.3 from 3.0, and FM3 on... it is a 1Hz low pass filter).  If the PLL loses its line, the Guardian will revert to acquisition mode.

Stefan, Matt, Kiwamu,

This is a quick note. We started another TCS test in this afternoon with the new ring heater setting (RHX = 0.5 W and RHY = 1.5 W, 29557).

With a 20 W interferometer, the CO2 settings that balances the 45 MHz upper and lower sidebands were found to be at almost where we thought it should be. Then we increased the PSL power to 40 W to study the interferometer absorption as a function of the PSL power. With the sideband imbalance adjusted, the lock seems more stable at 40 W.

[good values that balances the 45 MHz sidebands]

• At 20 W
  • [CO2X, CO2Y] = [650 mW, 400 mW]
• At 40 W
  • [CO2X, CO2Y] = [650 mW, 400 mW]
  • [CO2X, CO2Y] = [500-600 mW, 200 mW]
  • [CO2X, CO2Y] = [400 mW, 0 mW]

These settings seem to give us a small imbalance within 10%. Also, lock acquisition was done with [CO2X, CO2Y] = [500 mW, 700 mW] in which I did not adjust the differential CO2 settings.

By the way, the attached trends show how the aberration changed when we went from 20 to 40 W. Notice that ITMY show relatively high aberration values (e.g. cylindrical, coma, spherical aberration) compared to the ones for ITMX. The last attachment is a StripTool showing the HWS outputs. A jump in the middle is due to us increasing the PSL from 20 to 40 W. After we sat on 40 W for approximately 1 hour, we started decreasing the common TCS and kept adjusting the differential CO2.

Robert, Nutsinee

Yesterday we had a nearly 30-min lock at 50W that broke around 20:00 UTC when a fire drill started (43 seconds after the alarm sounded to be exact). Right before the lockloss I observed a noise at high frequency (+1000Hz) creeped up on DARM spectrum before it lost lock. I was curious if the fire alarm were responsible so I investigated a little. The coupling seems to be the highest around 2000-5000 Hz region by about 3 orders of magnitudes. The DARM RMS up to 1000 Hz doesn't seem much different so I'm afraid we cannot blame the fire alarm for causing the lockloss. The timeseries shows OMC DC PD was already becoming unstable over time. The thermal drift is known to be a problem. So this lockloss *could* just be a coincidence with the fire drill.

The coupling information itself worth an alog post though. According to Robert we have never done any acoustic coupling injection this loud (4 order of magnitude higher than the noise floor). I wouldn't want to be in the PSL when the fire alarm goes off.

Below are spectrum of DARM and a PSL periscope accelerometer, before and during the fire drill. Uncalibrated.

Zoom in from 0-1000 Hz

We attempted to center the beam on the HAM2 ISS array PDs using the steering picomotors; we set the IMC at 50W for this. We started with HAM2 picomotor 8, which is upstream of the ISS diode array telescope. The PD 1-4 signals were centered at maxima when the beam on the ISS array QPD was centered (BTW, as Cheryl pointed out, pitch and yaw are reversed on this QPD screen). Two of the diodes had significant improvements.  We then scanned with picomotor 1, which is closest to the array, and again decided to leave the beam centered on the QPD. I have not yet seen evidence of an improvement in jitter coupling from this centering. I suggest sticking with PD4 if we use only one.

Robert, Cheryl

Kiwamu, Stefan

We looked at the optical gain change during the 80min lock at 50W (alog 29556) as measuired by the 331.9Hz cal line, see plot 1. The reduction between the beginning of the lock (8:10 UTC, blue) and the end (9:15 UTC, red) is about 22%.

Plot 2 plots ASAIR_45_Q for the the period from 8:10 UTC to 9:15 UTC, since it should be a measure of effective fringe offset. Its value drops by 41% (from -526 to -373 microcounts). Also it shows a significantly bigger variation in the DARM offset towards the end of the lock.

While qualitatively this would be consistent with a decreased contrast defect feeding carrier light through the OMC, the magnitude of the gain reduction doesn't quite add up  - the percent reduction ought to agree since both optical gain and AS_Q DC value are proportional to the DARM offset. Also, the AS_45_I DC offset remains rougly constant (not plotted).

at 22:15 UTS (15:15PDT) the h1iopoaf0 model detected both an ADC and a DAC error, resulting in zero'ed dac outputs. I restarted all the models within 10 minutes, which restored h1tcscs's control of the chiller setpoint DAC channels. The itmx laser temp had dropped from 23.25C to 21.5C in the 14 minutes which had elapsed, a rate of 0.14C/min

The IOPs STATE_WORD went from 512 (OVF) to 652 (ADC,DAC,DK,OVF)

We should schedule a complete power cycle of h1oaf0's IO Chassis to hard reset the 16bit DAC.

Over-filled CP3 with the exhaust bypass valve fully open and the LLCV bypass valve 1/2 turn open.

Flow was noted after 26 seconds, LLCV valve was closed immediately after, but the exhaust bypass valve was left open (per Kyle's aLOG)

Keita Daniel

With the most recent modifications we were finally able to engage the new outer loop ISS. The gain slider was at 10 dB with 2 W input power. We increased the power to 50 W, while running the feedforward correction for the AC coupling loop. This gave us an ISS with a ugf around 300 Hz. Increasing the gain further will require more loop shaping to avoid internal saturations.

The first attached plot shows the PSD at 50 W with the servo engaged, whereas the black reference trace is with the servo off.

The second attached plot shows the power up transition—indicating that the feedforward works pretty well.

Fil Keita Daniel

At 50 W input power we are now saturating the amplifier stage, since there is too much whitening upfront and the compensation is after the gain. We moved the 20 Hz/380 Hz compensation to the transimpedance board to give us more headroom. Continuing from alog 29527 and alog 29293 we changed:

1. C26 was changed to a 33nF in series to 10K on the transimpedance board (4x channels on 2x boards). This gives a pole at 21 Hz and a zero at 483 Hz. This also eliminated one of the 15.4 kHz poles.
2. R49 was removed from the servo board to disable the second compensation stage and make it unity gain.

Some changes were made to the front-end model to change the polarity of the 0.1 Hz switches and to add filter modules to the PD readbacks. This allows adding anti-whitening filters. Since the AC readbacks now have a DC gain of 1, we don't need the dedicated DC readouts anymore.

Attached is the transfer function of one of the transimpedance PD chains.