Sheila, Terry, Nutsinee

This is a late alog of work done last Thursday afternoon.   The main message is that we don't think we are close to clipping with the squeezer beam in the interferometer alignment used for the squeezing injection test on Tuesday. 

Checking the range on SRM alignments:

• For our first test we ran the SRC alignment according to the way the initial alignment guardian does it: with SRY locked, feedback AS_C to SR2+SRM and AS WFS to SRM, then we misaligned SRM and ran and offloaded the DC centering loops from AS_A and AS_B to OM2+OM2.  We also tried moving SRM, OM1+OM2 to their positions during the squeezing test using the osem readbacks, this was a slightly different alignment.  We injected a seed beam and engaged the DC loops that Haocun commissioned to actuate on the ZMs and center on AS A and AS B diodes.  We then moved SRM sliders letting the servos follow with ZM1+2, and watched the sum on AS_A and AS_B for signs of clipping.  We were able to move SRM quiet far compared to the normal range that it moves from lock to lock without seeing clipping; the ZM actuators actually saturated before we saw clipping.  We were able to move SRM sliders from 2183 to 1370 for pit, and from -1975 to -3796 for yaw.  
• For the next test, we kept the servos running to ZM1 and ZM2 and left SRM at it's nominal position, and moved each OM in each direction until we saw signs of clipping.  We returned each OM to it's starting position before trying a different degree of freedom.  We were able to see clipping for ZM slider values of:

• 	ZM1	ZM2
  OM1 P -633	-790 P	-410 P
  positive OM1P saturated ZMs before clipping
  OM1 Y -1434	1532 Y	1337Y
  positive OM1 Y saturated ZMs before clipping
  OM2 P negative saturated ZMs before clipping
  OM2 P -705	-372P	-1690P
  OM2 Y -312	1912Y	2267Y
  OM2Y -1870	2912Y	747Y

  During the squeezing injection test our ZM sliders were at ZM1 P -198 Y 2499 ZM2 P -301 Y -8825

Due to the winter storms the site was closed on Saturday.  In an email on Saturday

All,

The LIGO Hanford site is closed until further notice. Adding to Bubba's earlier note about site conditions, the roads to the LHO site are now closed and/or experiencing blizzard conditions. In the interim, any personnel with a need for staff presence on site should contact Mike Landry or Jeff Jones. 

Best Regards,

Jeff Jones

Then Sunday night

All,

Given another winter storm warning for later this evening, the LIGO Hanford site remains closed until further notice. Personnel are not to report to work on site Monday morning. While this closure remains in effect, any personnel with a need for staff presence on site should contact Jeff Jones or Mike Landry. 

Best Regards,

Jeff Jones

It looks like h1iopsusb123 (SUSITM[X,Y],BS) had a timing error which resulted in a DACKILL, meaning all DAC outputs are 0.0V (and the 18bit-DAC AI chassis have disabled their outputs). A restart of all models on h1susb123  (/etc/startWorld.sh) is required to clear the problem.

[Rana, Jamie]

We spent the evening trying to get more measurements of the 9MHz RIN situation, basically redoing what was done in LHO log 46586.  We went to ITMY single-bounce and locked OMC on carrier, then went to PRMI and locked OMC on 9MHz.  I'll post plots tomorrow.

FYI the OMC and PRMI configurations might be a little bit funky.  We didn't get to reset everything yet to get back to low noise, just in case any one tries to brave the snow to get back out here.

Sheila, Keita, 

Summary:

We have switched DARM control back to ETMX for ESD, PUM and UIM, and we have reshaped the UIM filters to make the cross over of the UIM with the rest of the DARM loop more stable. 

Details:

We used ETMY L1+L2 + ETMX ESD as our DARM actuator for most of the fall, but in early January a scattering problem appeared in EY which caused us to move the DARM actuator to ETMX completely 46329.  Last Friday the ETMX configuration stopped working, 46751, so we have been using the split actuator this week.  We wanted to move the DARM actuator back to avoid possible scattering problems, because the calibration team has been working to calibrate EX, and we want to do this before retuning the LSC feedforwards. 

Last Friday when we were trying to switch from EY to EX, we measured the gain of the ESDs to DARM and the PUMs to DARM, and they were well matched between EX and EY.  The attached screenshot shows a comparison of the response of DARM to UIM drive for ETMX and ETMY that we made last night.  These were taken with a gain of 0.4 in L1LOCK L for ETMX and 0.6 for ETMY, which was based on an old measurement of the relative strengths (from before the ETMs were replaced).  This shows that with these old relative gains, we were using 25% too low a gain for the ETMX UIM offloading compared to ETMY.  Instead of 0.4 for ETMX we should have been using 0.53 as a L1 LOCK gain.  

The first two PDFs show a model of the DARM loop and its crossovers as it has been, compared with measurements taken in the actuator configuration used this week (ETMX ESD, ETMY UIM and PUM).   These actuator models are taken from the CAL front end filters, Evan Goetz helped me to compare parts of this to pyDARM.

The crossover measurements are taken at L2 LOCK L IN1/IN2 and L1 lock in2/in1.  If you think of the loop as a common path C, slow path S and fast path F, these measurements are of CS/(1-CF) which is approximately -S/F We would like to avoid the situation where the two actuators are canceling each other's motion which is approximately the same as staying away from a unity gain point with 0 phase in this measurement. You can see in the open loop model that the gain of the UIM and PUM paths are nearly equal from about 0.5 Hz to almost 3 Hz, which is not ideal, and that they are close to being out of phase.  We have know that this wasn't ideal for a while, but until last Friday we weren't having much trouble with the stability of the DARM loop so we have left it alone. The second attached plot shows a comparison of the old UIM lock L filter to a new one that Keita and I made today.  We replaced the UIM filter with this filter, and increased it's gain by a factor of 2 so that the gain setting for the L1 lock is now 1.06.  The 3rd and 4th attached PDFs show the DARM model with the new filter and gain for the uim.  The UIM crossover is now more stable.  The model underestimated the gain of the UIM path when it was locked on ETMY and over estimates the gain on ETMX, which we don't understand, but there is room to increase the UIM gain.

The third attached screenshot shows the rms drive to the suspensions before and after this change; we have room to increase the UIM gain more.  

These changes are in the guardian now.  If there are any problems in the LOWNOISE_ESD_ETMX state, you can reset the use_EX_L1L2 flag back to False. 

Covering latter part of Jim's shift....

Commissioning Status:  H1's ASC Loops were taking forever to converge.  Gabriele is moving stuff around to help them converge & eventually went to NOMINAL_LOW_NOISE at 18:48.

• 18:25 Handed off from Jim
• 21:00 Stopping violin mode damping, she had mentioned doing this for a few hours prior (Kara)
• 21:27 (headed back out at 23:53) EX power supply noise & glitch hunting (Robert)
• After lunch:  Gerardo was at all out-buildings to pick up VAC equipment.
• 21:46 MY vacuum work (Kyle)

Increased the Dust Monitor Alarm Settings by x3 in the LVEA, EX, & EY since they were alarming most of the day with no activity in the buildings.  

• 0.3um taken from 70 -> 210
• 0.5um taken from 100 -> 300

(I'm thinking I should bump them up a little more since EY just alarmed at 480, but maybe that's OK to keep track of dust events which might come up?)

We are about to conduct a test of the H1 OBSERVATION bit behavior (see lho elog 46812).  The following bits will be flipped during this test:

• H1:GRD-IFO_READY
• H1:GRD-IFO_INTENT
• H1:GRD-IFO_OK

Will respond to this log when the test is complete.

May need this on again next week.

Lilli Sun,

This is for H1 reference model uncertainty test (see 43260 for L1).

The 20190118 model is a bit confusing. The model parameters are rescaled according to 46605, which are not consistent with MCMC results. Using the model file and the MCMC results leads to systematic errors. Need to further investigate if the systematic error seen in the attached uncertainty plot is caused by the inconsistency.

Fil, Dean, Richard, Rich

After removing the newly implemented revised piezo driver two days ago, some modifications were made to see if there was any improvement to the broadening of noise in DARM around 180Hz.  We put the revised chassis back in and the DARM noise is back at 180Hz.

Attached is a detailed description of the state of the changes including:
1.  Noise spectra of the bias HV driver as measured on the bench
2.  Power supply rejection vs frequency of the bias HV driver
3.  Simplified description of the topology used.

Koji reminded me that this type of power line harmonic noise associated with the OMC PZT driver has been seen at LLO, and mitigated by the addition of a ferrite toroid to the shutter trigger cable.  There was also mention of unplugging the Picomotor driver while it was in an unused state.  These changes apparently improved multiple lines in DARM.  It's a good read.  See:
https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=41374

This should be investigated at LHO prior to removing (again) the modified OMC Piezo driver.

Tweaked the alignment into the reference cavity.  Transmission went from ~1.3 to 4.1.

    whilst I was in the enclosure, the HEPA fans and AC tripped off.  Don't know why.  As a
result it may take the temperature inside the enclosure a while to settle.  The pre-modecleaner
heater drive voltage nearing zero was the tell-tale sign that gave it away.

    Attached is a plot of the room temperature around the time of the mishap.

Sheila, Daniel, Terry, Nutsinee, Craig, Jenne, and others who were cheering in the control room

Today H1 saw (pre-O3) squeeze/anti-squeeze for the first time.

0.9 dB SQZ and 3.3 dB ASQZ at a non linear gain of 2.28.

We used the lowest amount of CLF we could reasonably operate at, 0.05mW into the coupler. 20.5 mW of pump was sent into the coupler on the ISCT6 (this corresponds to ~2.6-2.7 mW hitting the OPO, the nlg wasn't optimized before we injected the squeezing but that's about the best we've seen). We read -15dB of 3MHz demod signal from the Homodyne. The common gain at the LO common mode board was 7dB which gave us a UGF of 10kHz with plenty of gain margin. Boost 1 and 2 on the common path was turned on. 

Sheila has the sqz/asqz plot and the OMC DCPC traces. I have LO phase noise measurement. We will be posting these plot later.

Things we could optimize still is the alignment (which wasn't done at the beginning of the lock acquisition, we did try our best to optimize it while the LO was locked). A single bounce measurement with tonight's alignment should give us a loss estimate. 

Summary:

We've designed and ordered a custom mask for the ITMY CO2 projector. The purpose is to counteract the higher-order components of the thermal lenses in the recycling cavities that will predominantly affect the sidebands and lead to higher order differential lensing. Two big questions to be answered:

• How well does the mask have to be aligned (and how stable is the CO2 alignment)? Fine-tuning the alignment and the stability of the alignment will be important to monitor.
• What is the expected improvement in sideband imbalance/build-up versus just using the RHs (which is what we're doing right now)?

The installation and alignment of the mask is relatively low overhead. Once aligned, it will remain as an option for the commissioners to explore and further simulations can be performed on expected IFO performance.

Details

The mask is on the DCC at D1900030.

The procedure for finding the optimum mask is as follows:

1. Work out the steady-state thermal lens from a 4mm diameter, 10mW absorbing region. We're going to use this and rely on the fact that the thermal response is linear: i.e. the sum of the thermal lenses from absorber A and absorber B is the same as the thermal lens from "absorber A + absorberB": TL(A+B) = TL(A) + TL(B).
2. Create a function of N+1 parameters (we used N=317). For parameter a_i, (where i <= N), we add the above thermal lens centered around a point [x_i, y_i] and scaled by a_i. The N+1 parameter adds a quadratic thermal lens from the ring heater. This function is TL_fit(a).
   1. The points are spaced 10mm apart in rectilinear grid out to a radius of 100mm. Note that in the limit that the spacing is 4mm, we effectively recreate uniform absorption.
3. Create the total thermal lens using the data from the HWS (scaled to single-pass) TL_HWS, 
   1. TL_tot = TL_HWS + TL_fit(a)
4. Create a function that determines the RMS wavefront distortion of this total thermal lens weighted by the intensity of the TEM00 mode on the ITM
   1. = sum(TEM00*TL_tot)/sum(TEM00)
   2. F_RMS(TL_tot) = sqrt( sum(TEM00*(TL_tot - )^2) / sum(TEM00))
5. Use FMINCON to solve for the values of a that minimize F_RMS. (see aLOG 46127. )
   1. FMINCON allows us to be constraints on the parameters a.
   2. Each of the thermal points was limited to the range [0, 0.1]. The RH was limited 6W of power.
6. The solution to a yields the required distribution of heat across the test mass. Since we don't want to create a mask that is a regular series of holes (ie. a diffraction grating), we smooth this by a minimal amount to create large shapes of uniform heating and create an image from this. This image is used then used as the basis for a mask. The image is also made 9% larger in the horizontal direction to account for the fact that the AOI between the mask and the CO2 laser beam is 22.5 degrees.

Results from simulation:

Original heat distribution:

Mask for CO2 laser (at ITM scale):

Optical path distortion from CO2 laser projected through mask and imaged into ITM

Optical distortion from CO2 + Self/HWS OPD

OPD from RH + Self/HWS OPD

OPD from CO2 and RH and Self/HWS

Alignment

Alignment is a big issue - clearly this will need to be matched well to the existing thermal lens to be effective. A long term drift in the CO2 laser alignment to the test mass was noticed in Q4 last year (Approximately 12 months after the previous alignment). We need to be cognizant of this.

Fine tuning of the alignment will be accomplished by mounting the mask and flipper mirror on an X-Y translation stage that offers up to 3mm of travel in X and Y (corresponding to 63mm of displacement of the heat pattern in X and Y on the ITM with a magnification of 21x).

Magnification

The mask is set up for the nominal magnification of 21x. We should be cognizant of any variations in the actual magnification as this will create discrepancies between the required and actual heat patterns.