Caused lockloss from jitter injection

1435343011

It will probably register as an IMC lockloss, just wanted to make sure people know it was caused by an injection.

A super simple script to walk the uncontrolled IMC alignment DOF

Craig mentioned yesterday that we might want to walk our IMC uncontrolled degree of freedom: the spot position on MC1 and MC3. I made a short script which should step the sliders of MC1 and MC3 in the correct configuration (differential step in pit, common step in yaw). If you want to run it is in

/ligo/gitcommon/labutils/imc_walk

To step both mirrors by eg 0.1 microradians, run python walk_imc_dof_4.py P 0.1

This might not end up being used since Robert suspects much of our jitter could be caused by the multiple roughing pumps running in the LVEA.

Measuring input beam height above HAM1 table

Jennie W, Camilla,

This morning Camilla and I went into HAM1 on the +Y side and measured the beam height of the beam from the PSL above the table. This is to aid in the design for the JAC periscope.

First we measured the beam height near the septum window to HAM2. We had to use a metre stick that had been wiped down as the beam height was slightly too high for the 12 inch class-B ruler from the tool pan. This ruler had to be bent at the top as it reaches the sloping part of the edge of the chamber roof. Camilla and I took several measurements in case the bottom of the ruler was not straight up from the table.

+X (HAM2 side)

My measurements of this height are here and here - loks about 315mm above the table.

Camilla's measurements are here and here with three zoom outs so the bolt hole we lined the ruler up with and the surrounding components can be seen. Hers suggets 313 -314mm above the table.

We were both measuring in the same spot along the beam.

-X (PSL side)

My measurement on the -Y side suggests 317 mm above the table. The two following pictures are where I had the ruler in front of the balance mass.

This is another measurement with the ruler behind the balance mass but its too hard to see the numbers, I think it is still about 320 mm high here.

There are Camilla's measurements on the same side. The first looks like 317mm above the table, 311mm above the table. The third image shows Camilla had the ruler behind the balance mass (so in a different place from my first -X measurement).

Found PSL beam through IMC trans and refl viewports on HAM2

[Betsy, Keita, Camilla, Richard M., Elenna]

After the power outage, we wanted to get some confirmation of PZT pointing out of the PSL. Betsy, Keita and Camilla went in the cleanroom with the IR viewer and indicator cards and took the covers off the IMC refl and trans viewports on HAM2. Keita found the beam out of the IMC REFL viewport, and I adjusted the IMC PZT in pitch and yaw under direction from Keita. I accidentally moved the pitch slider a bit at the beginning due to user error. Then, we took large steps of 1000 or 2000 counts to move the offsets in pitch and yaw.

Start values: pitch: 22721, yaw: 5488

End values: pitch: 21192, yaw: 6488

Then, Betsy found the beam out of the IMC TRANS viewport and Richard marked the beam spot approximately on the outside of the cleanroom curtain with a red sharpie. This is super rough but gives us a general location of the beam. We think this is a good enough pointing recovery to proceed with vent activities.

 

Opened a new ISS PD array

Jennie Siva Keita Mayank

Following our previous attempt  here .  We opened a new ISS PD array (S.N. 1202965).
This unit is in great condition. i.e. 

1) No sign of contamination.
2) All the optics are intact (No chipping)

We tried interfacing the QPD-cable S1203257 with the QPD but it turned out that they are not compatible.
We will look for the updated version of the QPD cable.   

Partially disassembled ISS array

Jennie W, Rick S, Mayank C, Keita K

 

We went into the optics lab today with the intent for Rick to review the ISS array assembly we unboxed the other day (LHO alog #82731) on which we found some particulate contaminsation and some detached parts.. Rick and Keita are unsure how the support rods (first picture) were bent during transit and they appear to have bent at the top and deformed the cover piece (D1300717) they were attached to as they came unfixed at the other end and so were just resting on the top of the QPD mount plate (D1300719). They appear to have moved around and scored the surface of this platform. Maybe this happened in transit or storage but it seems like it would have had to be a large force and Rick says the storage containers were packed in form during transit.

 

1st package: Base piece (D1101074-v2 S/N 004) is double-bagged in my office and I have put in a clean and bake order as this spacer is site specific in height and some of our ISS spares will have a spacer set to the L1 beam height instead so we may need to swap it out.

2nd package: Cover piece D1300717 with the spacing posts attached is not bagged properly as we probably do not want to reuse this and so it is in Keita's office.

3rd package: Array and mirror assembly with PDs still attached was wrapped in foil with dry sealed clean room wipes protecting top optic in periscope, then double-bagged. Shown in center left of this image. This will need re-cleaned if we want ot scavenge parts form it.

4th package: All the other parts from assembl y shown in this image ( apart from PD assembly, baseplate, tool pan and top cover) have been packaged up in foil and double bagged in one package. These will also need recleaned if reused.

These last two packages are stored in the cabinet that the spare ISS array units are in, situated in the vacuum bake prep area next to the PCal lab. The shipping cover and base plate for the array are also back in this cupboard.

For reference the assembly drawing can be found here.

The assembly we worked on has the dcc ref S12020967

Apparent contamination and glass chipping in spare ISS PD array SN 1202967 (Siva, Mayank, Jennie, Keita)

To rebuild the spare ISS PD Array unit (D1101059 S1202967, note that I myself don't have an access right for the S-number document on DCC) and align the PDs, we opened the transport container (D1400368) in the optics lab.

We initially had a hard time to open the container as the viton gasket (D1400366) was REALLY firmly stuck to the container lid (D1400367) and the container base (D1400365). We put the container on top of small stainless steel cart and used screwdrivers to pry the cover off from the base plate. Even after two  corners were freed, we could not lift the lid just by hand, and we had to continue prying the lid until all four corners were freed.

Contamination:

After finally removing the lid, we found two bases for concern, the first is the contamination.

1. There were some class A hardwares (screws/bolts, washers, one half of the QPD PCB retainer, and what turned out to be one of the two adjustment cams for one of the two plate high reflectors) scattered around on the transport container base plate, which is supposed to be a class B surface. But the base plate was dirty when we wiped it using pre-soaked wipe.
2. Another half of the QPD PCB retainer was freely lying on the ISS PD base plate (D1300323) which is supposed to be class A surface, and it was dirty too.
3. We wiped all parts that were not attached to anything, and they were all dirty.
4. We haven't assessed the quality of the diodes nor the plate optics but there's no reason to believe that they are not contaminated.

The first two pictures shows the container assembly before and after removing the lid. 

Note that the second picture shows the class A "cover" for the assembly tilted back. It turns that the cover was just put there, free to rattle. Connection rods that are supposed to attach the cover to the cage structure were not bolted to the cage.

The third picture shows how filthy the container base plate was. It also shows a half of QPD retainer parts that were found there, next to a swagelock fitting attached to the base plate.

Fourth picture shows the pre-soaked wipe I used to lightly clean the top surface of the PD array base plate. I immediately picked up some black stuff. You can also see that the PEEK parts are covered with black stuff.

Fifth picture shows the PEEK parts. I wiped the top parts but the bottom one is yet to be cleaned. You can easily see the difference.

6th and 7th picture shows deep scuff on the class A surface of the array PD structure, which seemed to have most accumulated the black stuff.

IM4 trans QPD centered

I've used the pico to center IM4 trans QPD.   See alogs about this history: 80604 78962 78943 78856

 After difficulty with input alignment shifts in the spring, we centered IM4 with the hopes that we could use that as a reference for any future input alignment shifts to reset the IMs.  However this didn't work well when the PMC was swapped.  Now we are recentering IM4 trans to get this new reference since we've been operating here for a while.

02:08utc NLN Lockloss due to FSS/IMC Glitch After 1hr Lock

Had about 20hrs with no IMC/FSS glitches from 9pm Thurs night until about 340pmPT Fri afternoon.  But have now had several for the last 5hrs.

Also for one ~60min stretch, H1 almost made it to NLN, but had rung up violins which kept us at OMC Whitening for 20min until the next IMC glitch.

Here are some running notes for the rough 5hrs filled with glitches (currently have H1 in IDLE).

Notes During Return of IMC/FSS Glitch Locklosses

2340utc (340pmPT) LOCKLOSS with IMC tag was the beginning of IMC/FSS glitch locklosses (where we went almost 20hrs since the last glitch around 5utc (9pmPT).

0111-0208:  OBSERVING

0208utc (608pmPT):  Attached screenshot shows a coincident glitch lockloss seen on FSS & IMC.  Here is the LOCKLOSS page also tagged with IMC glitch.

Starting an FRS Ticket to mark the DOWNTIME (FRS-32644) for 3.5hrs of DOWNTIME so far.  Where there was notable part of downtime due to IMC not locking easily.

• 0241 Lockloss at DARM to DC ReadOut looked like a FSS/IMC glitch lockloss---> IMC + FSS lockloss tags.
• 0255 Lockloss at RESONANCE also looked like a FSS/IMC glitch lockloss---> IMC lockloss tag
• 0256 Lockloss at READY ---> FSS lockloss tag
• 0334 lock made it almost to NLN, Yay Yay Yay!!!!   BUT it was a little delayed due to....

VIOLINS Rung Up A Bit: (haven't had this since my shift on Tues night!)   So were stuck at OMC WHITENING for over 20min before H1 had....

• 0357 Lockloss at OMC WHITENING (with an IMC LOCKLOSS tag)

So for the last 3hrs:

• 0208-0256:  50min with a flurry of FSS/IMC glitches causing locklosses at various states also causing IMC locking grief.
• 0256-0357:  Hour of NO glitch locklosses, and almost made it to NLN (but rung up violins prevented that).  Then another IMC glitch.
• 0420 Went to IDLE due to more locklosses and for a pause

Not sure what is more useful.  Keep having ISC LOCK continue to locking, or to leave it in IDLE for IMC/PMC/FSS monitoring....

Centered IMC WFS

I took the opportunity to center the IMC WFS this morning since we've been getting the notification on DIAG_MAIN for some time. The process was as follows:

1. Offload IMC WFS by taking IMC_LOCK to 'MCWFS_OFFLOADED'
2. Take IMC_LOCK to 'OFFLINE'
3. Using the MCWFS centering scope and picomotors on the IMC overview screen, center the signal on each WFS (scope screenshot attached)
4. Accept IMC PZT offset SDFs from the previous offloading (attached)

OFI TEC servo tested in-air

Looking at the OFI TEC servo we noticed that the response was much slower than what one could expect from the given ugf frequency. The gain was increased fomr -1 to -15, whereas the ugf frequency was decreased from 50mHz to 10mHz. This resulted in a response time around 10s, which is about 3x faster than when we started. Increasing the ugf beyond this can make the servo unstable.

As a side note: The applied voltage at the driver was about 3x higher than the voltage readback from the TEC, indicating a rather large voltage drop in the cable.

Initial HAM6 Inspection: New discoloration on Fast Shutter

Sheila, Betsy, Camilla

With the HAM6 +X door off we did an initial inspection of HAM6, looking for anything that could have caused the pressure spikes seen in 78346, 78432. 

There was discoloration on the fast shutter, see lower half of the -X part of the "fast shutter cap" and viton piece: part (4) and  (10) of D1003318. Photos attached.  This was the only thing we could see out of the ordinary. 

From the Feb 2024 HAM6 closeout photos in 75791, this photo shows the fast shutter and no discoloration can be seen. 

We'll plan to inspect the fast shutter when closed today.

Quick inspection of the first OFI comonents visible as the door came off

Looks like there is visible damage on the KTP optic of the OFI.

 

TBC...

power estimates for sqz beams

Summary: We think that the sqz beam is seeing similar loss to the IFO beam in th alignment that we were running in until Friday, but double passed. The sqz beam transmission can be restored by moving the beam, and there should be enough power in this beam to be a useful diagnostic in chamber to distinguish between OFI and SRM damage.

Camilla and Noaki have measured 1.3mW coming from HAM7 towards HAM5 with the OPO locked on the seed. SRM transmission is 32.34%, ( 72680 ) so if nothing was damaged we should have something like 0.41mW of the OPO seed beam in transmission of SRM, which we should be able to measure with a power meter. 

The table in 79101 indicates that the single bounce transmission to AS_C has dropped to 64% of what it was last Thursday.  Here's a table of power predictions for the sqz beam arriving in HAM6:

no damage	sqz seed beam we expect at AS_C
no damage	1.3mW*(1-0.3234) * 0.99^2 = 0.86mW
single pass of damaged optic with 0.64 transmission	1.3*(1-0.3234)*0.99*0.99 * 0.64 = 0.55mW
double pass of damaged optic with 0.64 tramission	1.3*(1-0.3234)*0.99*0.99 * 0.64 *0.64 = 0.35mW

With the alignment used for observing in recent weeks Naoki and Camilla measured 0.2 mW on AS_C QPD (not well centered on AS_C, but on the diode), which is calibrated into Watts arriving in HAM6.  They moved ZM4 +5 to improve the transmission of the sqz beam to 0.9mW when centered on AS_C.  These numbers don't agree super well with the predictions above, but they seem to suggest that the SQZ beam sees similar damage to the main IFO beam, but double passed.

Tried and failed to recover alignment onto ISS array and IM4 TRANS

Jennie, Jenne, Sheila, Keita

 

While the PSL team were preparing for a PSL in cursion, I started moving MC3 based on our plan to re-align onto the ISS array and IM4 TRANS QPD after the PMC swap last week.

We tried going up in yaw, saw some increase in power on IM4 trans QPD but then the ISS second loop QPD started to become further from the centre position as did the IM4_TRANS QPD (this is well centred enough that we could see the power drop whereas the ISS QPD started quite far off centre so that the nsum is quite close to zero).

We went back to the maximum value then tried IM3 alignment is both DOFs but this did not improve things in both QPDs so we tried MC3 pitch. Sheila then noticed that we were mazking the IMC relflected spot some horrible higher order mode so we decided to stop and think.

MC1 and MC3 changed in common yaw due to the WFS as we changed the uncorntolled differential DOF (MC1 - MC3), which we did not expect, to recover our alignment we would need MC1 and MC3 to change differentially as they did after the PMC swap, in this image.

The ndscope channels I used for this alignment walking session are attached with cusors before we changed anything and after we recovered the IMC alignment to pre-maintenance.

In conclusion we have reverted the IMC alignment back to before our changes as we think some action before the in-vacuum mirrors is needed.

Plan: To revert periscope PZT and MC1 back to their positions before the PMC swap and get Jason/Ryan to move steering mirrors in the PCAL enclosure to recover the prompt reflection from the IMC as witnessed by the MC WFS behind MC1. Then we can re-align the IMC.

MC mirrors moved due to PMC swap

Jennie W, Jenne, Keita, Sheila

 

Summary: The input alignment was changed due to the PMC (pre-mode cleaner) swap last week. Sheila et. al. tried to recover this with IM3 moves but the IM4 TRANS QPD, our main alignment reference into the main IFO, is still off in yaw and so we will need to walk mirror or mirrors in the IMC (input mode cleaner) tomorrow to recover this.

The other option is to move something upstream in the PSL but this is harder to do as it involves moving in air steering mirrors and so is harder to reverse. This is plan B for another maintenance Tuesday.

 

Attached you can see how the MC mirrors changed before (first cursor) and after (second cursor) the PMC swap and Jenne tweaking the periscope mirror (first two plots in bottom row show positioning into IMC via the pitch and yaw of the upper PSL periscope mirror).

 

Plan: Move MC3 in yaw in order to change the output spot position in the IMC. We will do this with the ASC for the IMC running so the alignment loops for the angle of MC2 and the differential yaw between MC1 and MC3 will still run, but I will increase the gain value of these loops to its old value from December 2014 (0.25).

For future reference, the triangular cavity DOFs are discussed here: DCC LIGO-P1000135

And the MC in particular here: DCC LIGO-G1301131