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  16740   Mon Mar 21 18:24:07 2022 AnchalSummaryBHDPart IIa of BHR upgrade - Green laser alignment on Yarm

[Anchal, Tega]

We did the following alignment steps on Yarm today:

  • We aligned the green beam going into the ETMY chamber to the three irises on the path.
  • We aligned ETMY to get counter-propagating prompt reflection from ETMY.
  • We were able to see light in the reflection photodiode for the green PDH loop.
  • Then we went to ITMY chamber and checked where the beam is coming to. It was coming very low in height.
  • We walked the beam on the end to get it near the center of ITMY.
  • Then we changed the ETMY alignment again to get back the reflection beam on the reflection photodiode.
  • Then we went again to ITMY chamber and changed the ITMY alignment to get counter-propagating reflection from ITMY.

After this, we came back to the control room. One peculiar thing to note is that the C1:LS-Y_REFL_DC_OUT channel is inverted i.e. it is showing negative values for the reflection DC voltage. On this signal, we see a little bit higher-order mode flashing but it is not bright enough to be seen on the face camera of the suspension. We'll continue aligning the cavity using CDS now to get TEM00 mode.

After trying for a bit, we were able to get flash of about 2000 counts which is about 16% of the max value of 12200 counts. We adjusted the ITMY angular position using the IFO_ALIGN screen but used the OPTICAL_ALIGN offset screen to adjust the angular position of ETMY. The pitch and yaw values for ITMY are 1.0360 and -0.260 respectively whereas the pitch and yaw values for ETMY are 5664.0 and -4937.0 respectively. 

  16742   Thu Mar 24 19:20:28 2022 AnchalSummaryBHDPart IIa of BHR upgrade - Green laser alignment on Yarm

[Anchal, Paco]

Uneloged: yesterday, Paco and Ian tried locking the green laser on Yend to the Y-arm. Nothing noteworthy happened, no luck.

  • Started with aligning the green injection to the Iris on table (it was misaligned) and getting it on the ITMY center.
  • Then we realized that the beam is going through the focusing leans very offceter. This makes the beam warped and deflected inside that needs to be corrected by mirrors.
  • So we decided to adjust the lens position first.
  • We realized that lens position is hard to adjust along with keeping the beam hiting ITMY.
  • So, we decided to remove the lens first and just align the green beam directly with the Iris on the table and the ITMY center. The beam became as big as ITMY when it reached there without the lens in path. We aligned it to fall on the mirror.
  • Then we placed the lens back so that the beam goes through the center of the lens.
  • Then we aligned ETMY to get the reflection back to the reflection PD.
  • But then when we checked the beam at ITMY again, it was severely missing ITMY. The possible reason is that ETMY is a diverging lens for the beam as well and changing its position changed the beam direction in the beam tube.
  • We decided to do another iteration of lens positioning with the new ETMY position. So same steps, removed lens, aligned beam with iris and ITMY, placed back the lens, aligned ETMY again to get reflection back on the PD.
  • This time the beam was still reaching ITMY. So we were glad that our iterations converged in 2 repititions.
  • Then we aligned ITMY to get counter propagating beam.
  • At the end of this alignment:
    • We see dips in relfection photodiode counts from 12200 to 9500.
    • The ETMY oplev is partially out of range (only 1 of the quadrant seeing light) but that could be because we changed the lens position. So Oplev servo is off.
  • We confirmed that the PDH servo is properly connected and loop is on. But we see no HOM catching lock for YARM even after us doing about 10 min search with ITMY-ETMY alignments.
  • We are leaving things as it is. We'll continue trying to align the cavity tomorrow. Everyone is welcome to try as long as they restore the positions of the optics to a good state at the end.



  16744   Fri Mar 25 18:20:28 2022 AnchalSummaryBHDPart IIa of BHR upgrade - Green laser alignment on Yarm

[Anchal, Paco, Shruti]

  • Today we found out that the laser controller at the Yend had it's inputs disconnected for the FAST PZT input and the Slow temperature control input. The cables were also not labeled that were lying nearby.
  • I tracked the cables and connected the Fast input adn the slow input.
  • We then adjusted the temperature slider to go to previously marked laser crystal temperature of 40.1 degrees celsius. But we could not find the the beatnote of Y end IR with teh Main laser IR.
  • We scanned the laser crystal temeprature until we could see a beatntoe with the main IR laser and stopped in that region.
  • Then we continued looking for flashing and HOM, but no luck.
  • It was interesting that when the PDH loop was closed, we saw fluctuations in relfection photodiode DC value, but not so much when the loop was not closed.
  • We tried flipping the sign of the loop with no luck and we tried changing the gain of the loop as well, but no luck.
  • The behavior of this Yend laser and its controller is still suspicious to us. When the loop is closed, the PZT feedback signal should not cause a change in amplitude of the light so much as we see it.
  • Also the fact that when loop is clsoed we do not see signs of flashing in the reflection photodiode is interesting. If anyone has any ideas, that would be good.
  16745   Sat Mar 26 13:04:38 2022 PacoSummaryBHDPart IIa of BHR upgrade - Green laser alignment on Yarm

I came for a bit to check on the "1Y0 burning smell" reported by Koji last evening. I agree that there's a toasty smell around the 1Y0 rack, but it is hard to tell where it comes from exactly. I think we can use the FLIR heat camera, but this will have to wait for Monday when someone with an iphone is around.

I also played a bit with the YAUX alignment (which is still poor) but I didn't try anything different nor did I seem to have more success. This is also an outstanding item for Monday, where maybe the next step is to install the GTRY path for a CCD.

  16749   Thu Mar 31 18:58:16 2022 Ian MacMillanSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Xarm

[Ian, Paco]

We continued to try and lock the IR laser to the x-arm. Last time we adjusted TT2 PR2 and PR3 to adjust the beam to hit the center of the ITMX. Today we continued to adjust the same optics to make the beam hit the center of the beam splitter and make sure the beam is going in the direction of the ITMY. Then removed a mirror that wasn't even bolted down. I put it on the front right corner of the hood with all the other optics (right in front of a suspended mirror). With this unknown mirror removed the path was clear and hit the center of ITMX. From there we went and opened the ETMX chamber and using the IR scope we adjusted ITMX to put the beam on the center of the ETMX. We continued adjusting ETMX and ITMX until we had three reflections. We stopped here because we realized we should set up POX. We think this because any adjustment to set up the POX would mess up the work we had done on the x arm alignment.

  16757   Tue Apr 5 18:15:06 2022 AnchalSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Xarm

[Paco, Anchal, Ian, JC]

We attempted the alignment of IR beam into the arm cavities. We used PR2 and PR3 (moved manually as well as using cdsutils) and got the YAW aligned pretty good on both X and Y directions. PIT alignment however turned out to be much harder to align. PR2 PR3 didn't have much range, so we zeroed there offset and tried to use TT1, TT2, MMT1, and MMT2 to align the PIT but it would get clipped before reaching BS table if we were to correct for PIT misalignment happening downstream. We concluded that the issue is that one of the PR2, PR3 mirrors have too much PIT offset in equilibrium position. We have requested Koji to change the output resistors in the coil drivers of PR2 and PR3 so that we can correct for the PIT offset in them directly using the coils and reduce load on upstream optics. We have tweaked TT1, TT2, MMT1, and MMT2 positions today, so we do not have the previous reference anymore.

  16758   Wed Apr 6 01:20:48 2022 KojiSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Xarm

PR2/PR3 Output R for fame OSEMS reduced from 1.2K to 1.2K//100Ohm

I put the R=100Ohm for PR3 with the functions of the units mistakenly swapped. This affects imbalanced actuation of PR3 right now as well as too strong SD

PR2 Coil Driver 1 (UL/LL/UR) / S2100616 / PCB S2100520 / R_OUT = (1.2K // 100) for CH1/2/3

PR2 Coil Driver 2 (LR/SD) / S2100617 / PCB S2100519 / R_OUT = (1.2K // 100) for CH3

PR3 Coil Driver 1 (UL/LL/UR) / S2100619 / PCB S2100516 / R_OUT = (1.2K // 100) for CH3 only

PR3 Coil Driver 2 (LR/SD) / S2100618 / PCB S2100518 / R_OUT = (1.2K // 100) for CH1/2/3


The output R was reduced from 1.2k to 1.2k//100 = 92 Ohm.

This means that the face coil gains were increased by a factor of 13.

The original gains for PR2 Pos/Pit/Yaw were {0.7, 0.3, 0.2}. To keep the same loop gain, the new gains were supposed to be {0.054, 0.023, 0.015}.
With the new gain, the oscillations were very slowly reduced. Therefore, I increased the gains to have the gain margin of 2. (i.e. increased the gains until I have the oscillation, and then made it half.)
The new values were {0.2, 0.1, 0.05}. The side gain was 20 and unchanged

For PR3 the same operation has been done.

The original gains for PR3 Pos/Pit/Yaw were {1, 0.52, 0.2}. They were supposed to be reduced to  {0.077, 0.04, 0.015}.
The gains were increased to {0.5, 0.1, 0.1}. The side gain was also increased from 1 to 5.

Attachment 1: PXL_20220406_060846581.jpg
Attachment 2: PXL_20220406_014205726.jpg
Attachment 3: PXL_20220406_060324812.jpg
Attachment 4: PXL_20220406_015259326.jpg
  16760   Wed Apr 6 22:51:47 2022 KojiSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Xarm

[Yuta Koji]

We took out the two coil driver units for PR3 and the incorrect arrangement of the output Rs were corrected. The boxes were returned to the rack.

In order to recover the alignment of the PR3 mirror, C1:SUS_PR3_SUSPOS_INMON / C1:SUS_PR3_SUSPIT_INMON / C1:SUS_PR3_SUSYAW_INMON were monitored. The previous values for them were {31150 / -31000 / -12800}. By moving the alignment sliders, the PIT and YAW values were adjusted to be {-31100 / -12700}. while this change made the POS value to be 52340.

The original gains for PR3 Pos/Pit/Yaw were {1, 0.52, 0.2}. They were supposed to be reduced to  {0.077, 0.04, 0.015}.
I ended up having the gains to be {0.15, 0.1, 0.05}. The side gain was also increased to 50.


Overall, the output R configuration for PR2/PR3 are summarized as follows. I'll update the DCC.

PR2 Coil Driver 1 (UL/LL/UR) / S2100616 / PCB S2100520 / R_OUT = (1.2K // 100) for CH1/2/3

PR2 Coil Driver 2 (LR/SD) / S2100617 / PCB S2100519 / R_OUT = (1.2K // 100) for CH3

PR3 Coil Driver 1 (UL/LL/UR) / S2100619 / PCB S2100516 / R_OUT = (1.2K // 100) for CH1/2/3

PR3 Coil Driver 2 (LR/SD) / S2100618 / PCB S2100518 / R_OUT = (1.2K // 100) for CH3

Attachment 1: PXL_20220406_213356237.MP.jpg
Attachment 2: PXL_20220406_212936502.MP.jpg
  16759   Wed Apr 6 12:03:51 2022 AnchalSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Yarm

[Anchal, Paco]

After Koji reduced the output resistors on PR2/PR3 coil drivers, we got much better actuation range. We aligned TT1 TT2 again to get beam centered on PR2 and PR3. Then we used only PR2 and PR3 to do the input beam alignment to Y arm cavity. Using access in ETMY chamber, we aligned the input beam parallel to cavity axis. Slight changes were required in ETMY alignment offsets to get first roundtrip in same spot on ITMY. remaining alignment is finer and needs to be done with a help of a reflection photodiode and cameras in the control room. Immediate next step is to setup POY path for locking the Yarm with IR.

Side note: Because of the large PIT correction required in PR3, we found that our upper OSEMs were hitting totally bright limit and lower OSEMs were hitting totally dark limit on PR3. This also destablized our damping loops. We pushed the upper OSEMs slighlty and pulled back the lower OSEMs slightly to get the PD signal in half shadow region again. This worked and our damping loops are stable again. However, we think we should repeat free swing test in future to diagonalize the input matrix for new OSEM positions.

  16762   Thu Apr 7 17:59:51 2022 AnchalSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Yarm

[Anchal, Paco, JC, Tega]

Today we have aligned the Yarm cavity for IR, with verified 1.5 roundtrips. We also placed following optics in the BS table.

  • POXM1 (installed earlier, not eloged)
  • SRMOL2
  • POYM1
  • SRMOL1
  • POYM2

We also cleared the in-air BS table of all previous optics. JC and Tega setup HeNe laser for Oplevs roughly for now. Tega also transported the POY RFPD from ITMY in-air table to the BS in-air table. We aligned the POY path to the table, but we had to move ITMY after that to get 2nd roundtrip in the arm cavity, which misaligned our POY path again. POY path would need to be modified tomorrow.


  16768   Fri Apr 8 17:21:31 2022 Ian MacMillanSummaryBHDPart IIa of BHR upgrade - IR laser alignment on Yarm

[Ian, Paco, Tega]

Paco and I opened the ETMY and ITMY chamber to work on yesterdays efforts to lock the y arm. We temporarily in stalled a camera behind the ETMY to look at the transmission as we adjusted the ETMY and ITMY. We then moved on to setting up the POY. the beam was too large for the apature of the PD so we installed a lens in the beam path to decrease it.

Once that was installed we saw some flashing on the C1:LSC-POYCD_OUT channel. We also could see the flashing on the monitors in the control room. The flashing beam seemed to be in the middle of ITMY but was slightly to the right on the ETMY. From here we tried to walk the beam using PR3 and ETMY to move the beam to the center of the ETMY.

  16770   Mon Apr 11 21:13:21 2022 PacoSummaryBHDPart IIa of BHR upgrade - POY11 debugging

[Paco, Koji]

I asked Koji for some advice regarding closing the loop on YARM using POY11. A few things seemed off including

  • The YARM transmission; which was peaking at ~ 20 (typically, TRY is normalized so that under nominal input power conditions we see TRY in the range [0, 1])
  • The POY11 DCPD level was quite low; we expect a few tens of uW in this low power configuration where no more than 100 mW are going through IMC.

We looked at the POY11 RFPD first. We tried flashing an incandescent lamp in-situ and saw some weak response using an oscilloscope and the DC Out readout. We then used the OPHIR power meter and recorded ~ 1.2 uW of light incident on the POY11 RFPD... Initially, we suspected our beam was not filling the PD sensitive area (~ 2 mm diameter), but a quick estimate using the 200 mm focusing lens currently installed in the ITMY table gave us quite a generous margin of error... so we questioned the OPHIR measurement. We swapped the power meter and this time got ~ 18.4 uW, which is more in line with what we expected (phew).

Moving on, from the POY11 RFPD responsivity, and our ~ 20 uW of incident power, we expected on the order of a 20 mV of DC Output, but weren't really seeing this on the scope, so we decided to test the pins on the power of the RFPD. The DB15 cable not only supplies bipolar 15 VDC but also monitors several other test points such as Tsens, or DCout in the RFPD. We quickly noticed a weird signal on the ENAB testpoint, so we removed POY11 RFPD from the ITMY table and took it to the PD testbench. After redoing the soldering on the breakout board and RF amplifier (ZXX-500LN+), which we tested separately, we saw the expected behavior using a +- 15 VDC power supply... thus verifying that the RFPD and breakout board seemed to work ok. We turned our attention to the upstream DB15 connection, and after quickly checking the newly run cables, we ended up debugging the eurocrate PD interface. After attempting a simple power cycle and failing, we removed this card and looked at the schematic. It would seem that the logic enabling ICs (one or both) failed, thus preventing the card from enabling its outputs correctly.... We bypassed the logic by soldering pins 4,8,14 on U1, U20 and then checked the circuit in-situ, and we saw it worked fine again.

Now none of the status LEDs (which are driven by the logic IC portion) work on this card, but the card itself works fine at least for POY11.

We moved on, and installed the DB15 cables, checking the functionality at every step... Then we looked at the POY11_I_ERR signal and were happy to see nice pdh wavelets. We pushed forward a little bit more to try and lock YARM. First, we went to the Y end and centered the ETMY Oplev so as to register the position where the YARM is flashing... The ITMY Oplev is still not online. Then, we optimized the ETMY damping gains somewhat to try and make it less noisy, and finally, played with the LSC YARM loop gain to attempt locking. This last push was not as successful, but we have an idea of what next steps are needed to reduce the SUS noise, including

  • Install ITMY Oplevs, and close loop
  • Optimize ITMY damping gains

To be continued....

  16771   Mon Apr 11 21:44:14 2022 KojiSummaryBHDPart IIa of BHR upgrade - POY11 debugging

We took out the right most PD interface board D990543 and removed the 74LS04 chips. In fact two out of 4 were already replaced with enabling wires, however it seemed that one of the remaining two got failed.
These remaining two chips were removed and the enabling signals were connected to VCC (+5V). This operation made the status LED light not functional. (We didn't bother to fixed them by connecting them to the GND)

The new schematic diagram was attached here, and the corresponding DCC entry (https://dcc.ligo.org/D1900318-v1) was modified. Attachments #2-3 show the circuit after the changes, and the front view respectively.

Attachment 1: D990543A1.PDF
D990543A1.PDF D990543A1.PDF D990543A1.PDF
Attachment 2: PXL_20220412_023941730.jpg
Attachment 3: PXL_20220412_023950567.jpg
  16779   Thu Apr 14 11:52:57 2022 yehonathanSummaryBHDPart IIa of BHR upgrade - POY11 debugging

{JC, Paco, Yehonathan, Ian}

POY lens was moved to infront of the POY steering mirror to make the POU beam focused on the POY11 RFPD. We measured the DC output with an oscilloscope and optimized it with the steering mirrors. We get ~ 16.5mV.

The new lens position blocked the BS OpLev ingoing beam, so we repositioned the OpLev mirrors to make the beam path not hit the lens.

We went to the control room to observe the PDH signal. We observed a series of PDF osscillation and then the signal died infront of our eyes! There is just noise.

We go and check the +/-15V powering the RFPD and we find that the V- is ~ 14V which is good but the V+ was ~ 2.7V which is not.

We went to the PD interface and measure the POY11 output oltages using a breakout board and got the same result.

The PD interface was taken out for inspection. All the OP27 on channel 3 were replaced with new ICs (without need turns out)...

The PD interface card turned out to be OK. What happened is that one of the Kepcos in the RF rack died because its fan crumbled as seen in Attachment #2 (could this be the source of burning smell?). In response, the rack was drawing from the other Kepco (connected in parallel) way too much current  (4A) and the current limiter dropped its voltage from 15V to 2.7V.

The Kepco pair was removed and replaced with a single Sorensen. The POY PDH signal was restored (see attachment).

Attachment 1: Screenshot_2022-04-14_15-53-39.png
Attachment 2: PXL_20220414_220616875.jpg
  16781   Thu Apr 14 18:39:13 2022 PacoSummaryBHDPart IIa of BHR upgrade - POY11 debugging


In reply to Koji's questions;

Q1: What is the product number of the broken Kepco?

A1: Kepco JQE 0-25 V 4A (1/4 rack mountable 100 W linear power supply)

Q2: Do you feel the burning smell on this broken kepco?

A2: Not very clearly. It just smells like generic broken electronic, but the fan was already long gone by the time we detected its problem.

Q3: How much current does the +15 VDC line draw from the Sorensen?

A3: The Sorensen current monitor reads 6.3 Amps

Q4: Is there a linear power supply in the market that can handle this much current with some margin?

A4: Probably... but we would have to look around.

Q5: Do we really need a linear power supply there?

A5: Good question, I guess anything that is not contaminating the RF electronics with HF noise (e.g. switching PS) can work?

Q6: Is the same fan problem happening on other Kepcos?

A6: Other fans are on, but at least one or two have the "ill" sound... It may be worthwile to give them maintenance if we can.

  16786   Mon Apr 18 17:53:45 2022 PacoSummaryBHDPart IIa of BHR upgrade - POY11 debugging

[Paco, Ian]

We aligned the X-arm IR laser

  • First fix pointing on the ITMX by moving the BS (mostly pitch)
  • then open etmx chamber and fine tune the pointing using the BS until it is centered on ETMX
  • using beam card we quickly see the third reflection back misaligned on pitch so we move ITMX pitch to center it on ETMX
  • fine tune the ITMX alignment on ETMX and check higher order reflaction overlaping with input

at this point we checked C1:LSC-TRX_DQ using ndscope and luckly we see a tiny bit of flashing (about 0.04 in normalized high gain PD counts). So we closed ETM chamber and ITM chamber and go to control room to optimize this signal. The optimization was done in the following way:

  • First, just reiterate on the last steps from above, by maximizing the peak transmission using ITMX/ETMX pair.
  • Then, slide BS alignment, mostly in PIT, and return to ITMX/ETMX pair.
    • At some point, turning the BS PIT made a huge improvement, so I turned the control room light off and looked at the camera on the quad monitors.
  • Based on the location of the flashes (now brighter) on the ITMX/ETMX, the beam seemed to be off in PIT more than YAW, so we focused on correcting the pointing (moving BS) and then correcting with ITMX/ETMX, until the flashes got centered around ETMX.

Final peak transmission (C1:LSC-TRX_DQ) was ~ 1.3 in normalized high gain PD counts. Power budgeting tells us the peak should be ~ 2.0. The flashing on this arm is much better than YARM, so we will press on by installing POX11 RFPD and attempt locking tomorrow. This also means that YARM can be improved by a combination of alignment and/or SUS damping.

In the end we turned on the ETMX oplev and centered it to "save" our flashing position using this reference.

  16437   Thu Oct 28 16:32:32 2021 PacoSummaryBHDPart IV of BHR upgrade - Removal of BSC eastern optics

[Ian, Paco, Anchal]

We turned off the BSC oplev laser by turning the key counterclockwise. Ian then removed the following optics from the east end in the BSC:

  • OM4-PJ (wires were disconnected before removal)
  • GRX_SM1
  • OM3
  • BSOL1

We placed them in the center-front area of the XEND flow bench.

Photos: https://photos.app.goo.gl/rjZJD2zitDgxBfAdA

  16592   Tue Jan 18 15:19:49 2022 PacoSummaryBHDPart IV of BHR upgrade - Replaced old SR3 with SOS SR2. OSEM tuning attemtped.

[Tega, Anchal, Paco]

We started working on SR2 installation. Preliminary work involved

  • Removing SR3 from BS chamber. For whatever reason this optic was still installed. It got relocated in the west corner of the ETMX flow bench.

That was pretty much it. After identifying the cabling situation, we proceeded to bring SR2 from the cleanroom. The magnets and wires remained well through their travel.

Connected OSEM one-by-one. Starting from top right  to left (PIn1)

1st connector: LL -> UR -> UL

2nd connector: LR -> SD** (we had some trouble here where the first time we made a connection we didn't see any signal, after a brief review of cables, sat amp unit, cables again with Koji, and sat amp again, we found out a connection was not done in the front of the SR2 SatAmp box, after which we saw the sensor signals).

Loosening all OSEMs and taking them out and noting full bright readings:

  • SD: 29600 -> 14980
  • LR:  21840 -> 10920
  • UR:  25900 -> 12950
  • LL: 28020  -> 14010
  • UL: 25750 -> 12875

After finishing the initial SD osem tuning, we moved onto UL, and then to UR, but we noticed that the UR was not able to drop to its target value of ~13000 counts, even when the OSEM face was < 1 mm from the adapter (see Attachments #1-2). Apart from becoming harder to push in, it became apparent that the dark level (full shadow) is not consistent with ~ 0 counts; is there an offset coming from SatAmp? We quickly checked the OSEM by replacing it in-situ with another working one from the cleanroom batch, but the issue persisted. We decided to stop here, as we suspect the SatAmp box might have some issue.

Photos: https://photos.app.goo.gl/HXzG6mj4oxKTksjZ7

Attachment 1: PXL_20220119_012954365.jpg
Attachment 2: PXL_20220119_013003522.jpg
  16605   Thu Jan 20 17:03:36 2022 AnchalSummaryBHDPart IV of BHR upgrade - SR2 OSEM tuned.

The main issue with SR2 OSEMs, now that I think of it, was that the BS table was very inclined due to the multiple things we removed (including counterweights). Today the first I did was level the BS table by placing some counterweights in the correct positions. I placed the level in two directions right next to SR2 (clamped in its planned place), and made the bubble center.

While doing do, at one point, I was trying to reach the far South-West end of the table with the 3x heavy 6" cylindrical counterweight in my hand. The counterweight slipped off my hand and fell from the table. See the photo in attachment 1. It went to the bottommost place and is resting on its curved surface.

This counterweight needs to be removed but one can not reach it from over the table. So to remove it, we'll have to open one of the blank flanges on the South-west end of BS chamber and remove the counterweight from there. We'll ask Chub to help us on this. I'm sorry for the mistake, I'll be more careful with counterweights in the future.

Moving on, I tuned all the SR2 OSEMs. It was fairly simple today since the table was leveled. I closed the chamber with the optic free to move and damped in all degrees of freedom.

Photos: https://photos.app.goo.gl/CQ6VouSB1HX2DPqW6


Attachment 1: DJI_0144.JPG
  16595   Wed Jan 19 12:50:10 2022 AnchalSummaryBHDPart IV of BHR upgrade - SR2 OSEM tuning progress.

It was indeed the issue of the top OSEM plate not being in the right place horizontally. But the issue was more non-trivial. I believe because of the wedge in thick optics, there is a YAW offset in the optic in the free hanging position. I had to readjust the OSEM plate 4 times to be able to get full dark to bright range in both upper OSEMs. After doing that, I tuned the four OSEMs somewhat near the halfway point and once I was sure I'm inside the sensitive region in all face OSEMs, I switched on POS, PIT, and YAW damping. Then I was able to finely tune the positions of both upper OSEMs.

However, on reaching to lower right OSEM, I found again the same issue. I had to stop to go to the 40m meeting, I'll continue this work in the afternoon. But OSEM plate adjustment in the horizontal direction, particularly for thick optics is required to be done before transporting them. I achieved the best position by turning the OSEM 90 degrees and using the OSEM LED/PD plates to determine the position. This was the final successful trial I did in adjusting the plate position horizontally.


  16593   Tue Jan 18 18:16:28 2022 AnchalSummaryBHDPart IV of BHR upgrade - SR2 Sat Amp Box inspection

I tested the monitor ports on the SR2 Sat Amp Box but found that all LED Mon and PD Mon are giving expected values. I disconnected the cable to OSEM and checked the PD monitors and found no offsets in case of no PD current. I realised that PD transimpedance offset should be checked with PD inputs shorted instead. So I created a male DB 25 connector with pinds 2-3, 50-6, 8-9 and 11-12 shorted. This on connecting to the OSEM cable at the back of sat amp boxes should short the PD inputs. On using this plug, I found no offsets in any of the Sat Amp PD output channels.

Discussion with Koji

It is possible that the issue is there because the magnet is missing the LED-PD path way because it is offset sideways. In fact, in my limited memory, I do not recall seeing the UL OSEM signal ever going to complete darkness either. Tomorrow, we should take a photo of the OSEMs from the back and see if any sideways adjustment of the top OSEM plate is required. If any adjustment is required, we must take the OSEMs out and then do the adjustment. Do not attempt to adjust OSEM plate with OSEMs inserted in-situ. That will most probably knock off the magnets.

  16622   Tue Jan 25 11:02:54 2022 AnchalSummaryBHDPart IX of BHR upgrade - AS1 free swing test failed

For some reasonf the free swing test showed only one resonance peak (see attachment 1). This probably happened because one of the earthquake stops is touching the optic. Maybe after the table balancing, the table moved a little over its long relazation time and by the time the free swing test was performed at 3 am, one of the earthquake stops was touching the optic. We need to check this when we open the chamber next.

Attachment 1: AS1_freeSwingTestFailed.pdf
  16639   Wed Feb 2 16:32:02 2022 AnchalSummaryBHDPart IX of BHR upgrade - AS1 free swing test still not good

We still did not get a good AS1 free swinging spectrum. It seems the Side OSEM is reporting coupling to too many DOFs and some extra resonances than we expect. So we did not upload the new input matrix calculated from this test. I'm attaching teh peak fitting (attachment 1) and the diagonalization attempt (attachment 2) to give some idea of what happened. Note how different this fre swinging spectrum looks from the other optics. Given that Yehonathan also felt that somthing might be off with this optic, we need to reevaluate if the suspension has wire not aligned in grove, or it is imbalanced or something else if touching it still.


Attachment 1: AS1_FreeSwingData_PeakFitting_20220125.pdf
Attachment 2: AS1_SUS_InpMat_Diagnolization_20220202.pdf
  16625   Thu Jan 27 08:27:34 2022 PacoSummaryBHDPart IX of BHR upgrade - AS1 inspection and correction


This morning, I went into ITMY chamber to inspect AS1 after the free swinging test failed. Indeed, as forecasted by Anchal, the top front EQ stop was slightly touching, which means AS1 was not properly installed before. I proceeded by removing it well behind any chance of touching the optic, and did the same for all the other stops, of which most were already recessed significantly. Finally, the OSEMs changed accordingly to produced a PITCHed optic (top front EQ was slightly biasing the pitch angle), so I did a reinstallation until the levels were around the 14000 count region. After damping AS1 relatively quickly, I closed the ITMY chamber.


For some reasonf the free swing test showed only one resonance peak (see attachment 1). This probably happened because one of the earthquake stops is touching the optic. Maybe after the table balancing, the table moved a little over its long relazation time and by the time the free swing test was performed at 3 am, one of the earthquake stops was touching the optic. We need to check this when we open the chamber next.


  16620   Mon Jan 24 21:18:40 2022 PacoSummaryBHDPart IX of BHR upgrade - AS1 placed and OSEM tuned


AS1 was installed in the ITMY chamber today. For this I moved AS4 to its nominal final placement and clamped it down with a single dog clamp. Then, I placed AS1 near the center of the table, and quickly checked AS4 could still be damped. After this, I leveled the table using a heavier/lighter counterweight pair. 

Once things were leveled, I proceeded to install AS1 OSEMs. The LL, UL, UR OSEMs had a bright level of 27000 counts, while SD and LR were at 29500, and 29900 respectively. After a while, I managed to damp all degrees of freedom around the 50% thousand count levels, and decided to stop. 

UL 27000.  -> 16000
UR 27000. -> 13800
LL 27000 -> 14600
LR 29900 -> 14900
SD 29500 -> 12900

Free swinging test set to trigger

AS1 is set to go through a free swinging test at 3 am this evening. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.

To access the test, on allegra, type:

tmux a -t AS1

Then you can kill the script if required by Ctrl-C, it will restore all changes while exiting.


  16729   Tue Mar 15 18:42:37 2022 AnchalSummaryBHDPart IX of BHR upgrade - AS1 resuspended and OSEMs tuned



  16545   Thu Jan 6 11:54:20 2022 AnchalSummaryBHDPart IX of BHR upgrade - Placed AS1 and AS4

[Paco (Vacuum Work), Anchal]

Today we opened the ITMY Chamber and installed suspended AS1 and AS4 in their planned positions. In doing so, we removed the razor or plate mounted on a pico motor at the south end of the table (see 40m/16450). We needed to make way for AS4 to be installed.

Photos: https://photos.app.goo.gl/YP2ZZhQ3jip3Uhp5A

We need more dog clamps for installing the suspensions, we have used temporary clamps for now. However, knows where new C&B clamps are, please let us know.

  16554   Fri Jan 7 16:17:42 2022 AnchalSummaryBHDPart IX of BHR upgrade - Placed AS1 and AS4 filters


Added input filters, input matrix, damping filters, output matrix, coil filters, and copy the state over from LO1 into AS1 screen in anticipation for damping.

Added input filters, input matrix, damping filters, output matrix, coil filters, and copy the state over from LO1 into AS4 screen in anticipation for damping.

  16559   Sat Jan 8 16:01:42 2022 PacoSummaryBHDPart IX of BHR upgrade - Placed LO2 filters

Added input filters, input matrix, damping filters, output matrix, coil filters, and copy the state over from ITMX into LO2 screen in anticipation for damping.

  16591   Tue Jan 18 14:26:09 2022 PacoSummaryBHDPart IX of BHR upgrade - Placed remaining filters SR2, PR3, PR2

[Anchal, Paco]

Added input filters, input matrix, damping filters, output matrix, coil filters, and copy the state over from LO1 into SR2, PR2, PR3 screens in anticipation for damping.

  16800   Thu Apr 21 18:42:47 2022 TegaUpdateBHDPart V of BHR upgrade - Align LO and AS beams to BHD BS

[Tega, Yuta, Paco]

We tried aligning the LO and AS beams on to the BHD beamsplitter. During the alignment process, we noticed that the damping loop for AS1 was not working. Paco drew our attention to the fact that the UR OSEM signal was alway close to zero, so we checked to ensure that the magnet was still within the OSEM recess and it looks OK. Next we checked the electrical connection at the interface between the copper OSEM cables to the blue in-vacuum flat cable and this too looks alright also. Since the AS1 coil driver was recently modified, it is possible we might find the problem there, so I'll ask Koji about this.

So Koji clarified that the coil driver board and SATAMP boards are different so we should connect this issue to the coil driver board.

  16797   Thu Apr 21 16:49:01 2022 PacoUpdateBHDPart V of BHR upgrade - BS Oplev + LO1 offset

[Paco, JC, Yuta]

We aligned the BS oplev using the new BSOL mirror pair. The main change is now the AOI of the oplev on the BS is quite normal. The output beam in the in-air table was quite large (diverging?) so we had to place a short FL lens in front of the QPD.

Separately, I added the LO1 YAW offset of ~ -2500 counts (before the coil driver changes it was -24500 counts) and saw LO beam hitting LO2. This means the alignment of the LO beam can move downstream.

  16788   Tue Apr 19 18:10:10 2022 PacoUpdateBHDPart V of BHR upgrade - POX11 path, LO path, and ITMX Oplev

[Yuta, Paco]

We set up POX11 beam path from ITMX chamber to the ITMX in-air table. To do this, we first identified the POX reflection on the ITMX chamber, and then steered the POXM1 (in the BSC) by hand until we cleared the viewport. We also checked that the POX beam is centered on POXM1.

We then decided to slide the LO1 YAW to clear the LO beam path, which was otherwise clipping on the PR2 SOS. The slider (DAC limited) range of -25000 counts was barely enough to clear the SOS comfortably and avoid hitting the POXM1. The LO beam is now hitting LO2 mirror, so LO alignment can proceed from BSC and ITMY chamber.

Finally, we aligned the input ITMX Oplev beam to ITMXOL2, then ITMX, then to ITMXOL2, and finally into the ITMX in-air optical table. We took some photos of the Oplev beam (see Attachments) to note their position.

By the end of in-vacuum work there was still some flashing in the arm cavities, but fine alignment is required.

After closing the ITMX Chamber, and BSC, we moved on to center the ITMXOL beam. We accomplished this by using two mirrors instead of one as was previously the case. This relaxed the angle of incidence a little, but we had to change the path and the position of the QPD. The QPD sum reads ~ 6600 counts versus the ~ >8000 counts it read right before the vent. One attempt at closing the OL loop, and the ITMX starting oscillating in YAW (PIT was ok), so we realized that maybe we flipped the order in which the OL1 / OL2 mirror were arranged and so the YAW loop needed to flip its sign. Indeed after changing the C1:SUS-ITMX_OL_YAW_GAIN from -6.0 to 6.0 the OL_YAW loop is stable.

Attachment 1: DJI_0167.JPG
Attachment 2: DJI_0169.JPG
Attachment 3: DJI_0168.JPG
  16789   Wed Apr 20 08:20:22 2022 PacoUpdateBHDPart V of BHR upgrade - PR2 weirdness

Yesterday, I tried tuning the PR2 damping gains by increasing the gain until the damping gave the ~5 oscillations (by watching the damped motion using StripTool, and keeping an eye on the PD var). I noticed that often when I changed the gain, some OSEM sensors shifted (gained an offset!!) and the PD var values changed, typically increasing at higher damping gains. I reverted the changes until the PD var looked "normal" again (~ 2 mV) but it is hard to imagine that the damping filters can have such a "DC" effect, given the shape comprises single zero at 0 Hz (and pole at 30 Hz).

  16792   Wed Apr 20 18:50:03 2022 KojiUpdateBHDPart V of BHR upgrade - PR2 weirdness

It seemed that it comes from the servo oscillation. This does not happen when the output limitters were set to be 100-ish. But even so the gains looked quite low.

I turned on the Cheby rool-offs for all the DOFs, and this allowed me to increase the damping gain A LOT.
The gains were 2~5 but now they are now 20-25 for the face OSEMs and 150 for SD.

The attached is the example of the damping when all the damping loops are on.

I think we need to tune the servo loops carefully for all the SUSs by actually looking at the openloop transfer functions rather than a personal feeling. => To Do

Attachment 1: Screenshot_2022-04-20_18-46-11.png
  16450   Fri Nov 5 12:21:16 2021 AnchalSummaryBHDPart VI of BHR upgrade - Removal of ITMYC optics

Today I opened the ITMY chamber and removed the following optics and placed them in Xend flow bench (See attachment 1-3 for updated photograph):

  • OM1
  • OM2
  • SRMOL1
  • SRMOL2
  • POYM1
  • 3 counterweights one of which was double the height of others.

I also unscrewed SRM and parked it near the Western end of the table where no optical paths would intersect it. Later we will move it in place once the alignment of the rest of the optics has been done.

While doing this work, I found two unnoted things on the table:

  • One mirror mounted on a mount but not on a post was just sitting next to ITMY. I have removed this and placed it on Xend flow bench.
  • One horizontal razor or plate on the South end of table, mounted on what I thought looked like a picomotor. The motor was soldered to wires without any connector in-line, so I could not remove this. This is on the spot of AS4 and will need to be removed later.

Photos: https://photos.app.goo.gl/S5siAYguBM4UnKuf8

Attachment 1: XendFlowBenchLeftEnd.jpg
Attachment 2: XendFlowBenchMiddle.jpg
Attachment 3: XendFlowBenchRightEnd.jpg
  16552   Thu Jan 6 21:04:41 2022 AnchalSummaryBHDPart VIII of BHR upgrade - LO1 OSEMs inserted

[Anchal, Koji] Part of elog: 40m/16549.

The magnets on the mirror face are arranged in a manner that the overall magnetic dipole moment is nullified faraway. Because of this, the coil output gains in all such optics need to have positive and negative signs in a butterfly mode pattern (eg. UL, LR: +ve and UR, LL: -ve).

In the particular case of LO1, we chose following coil output gains:

UL -1
UR 1
LR -1
LL 1
SD -1

This ensures that all damping gains have positive signs. Following damping gain values were chosen:

YAW 0.2

Having said that, this is a convention and we need to discuss more on what we want to set a convention (or follow a previous one if it exists). My discussion with Koji came up with the idea of fixing the motion response of an OSEM with respect to coil offset by balancing the coil gains across all optics and use same servo gains for all optics afterwards. But it is a complicated thought coming out of tired minds, needs more discussion.

Important notes for suspending the optics:

  • Do not insert the OSEMs fully. Leave all of the magnet out of the OSEMs before transportation.
  • Tighten the OSEMs completely while adjusting the height of the optic. Adjust height of OSEM holder plate if necessary.
  • Ensure the all cage screws are screwed tight completely.

Photos: https://photos.app.goo.gl/CJsS18vFwjo73Tzs5

  16621   Tue Jan 25 10:55:02 2022 AnchalSummaryBHDPart VIII of BHR upgrade - LO2 input matrix diagonalization performed.

The free swinging test was successful. I ran the input matrix diagonalization code (/opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/sus_diagonalization.py) on the LO2 free-swinging data collected last night. The logfile and results are stored in /opt/rtcds/caltech/c1/Git/40m/scripts/SUS/InMAtCalc/LO2 directory. Attachment 1 shows the power spectral density of the DOF basis data (POS, PIT, YAW, SIDE) before and after the diagonalization. Attachment 2 shows the fitted peaks.

Free Swinging Resonances Peak Fits
  Resonant Frequency [Hz] Q A
POS 0.981 297 3967
PIT 0.677 202 1465
YAW 0.775 2434 1057
SIDE 1.001 244 4304

LO2 New Input Matrix

The new matrix was loaded on LO2 input matrix and this resulted in no control loop oscillations at least. I'll compare the performance of the loops in future soon.

  16618   Mon Jan 24 18:53:09 2022 AnchalSummaryBHDPart VIII of BHR upgrade - LO2 placed and OSEMs tuned

I placed LO2 in its planned position in BS chamber, inserted the OSEMs, and tuned their position to halfway brightness. At the end of the work, I was able to damp the optic successfully. The full open (full brightness) OSEM ADC counts are:

UL 25743.  -> 12876
UR 27384. -> 13692
LL 25550. -> 12775
LR 27395 -> 13697
SD 28947 -> 14473

Today's OSEM tuning was relatively unhappening. I have only following two remarks:

  • BS table was 3 SOS near the East end and PRM is parked in the center, thus the table is very unevenly balanced. I had to use all available counter weights to make it flat near the LO2 suspension.
  • The side OSEM for LO2 is not exactly centered (probably due to table imbalance). I was able to balance the table to a point though that the side OSEM was responsive to full range and I was able to damp the optic.

Free swinging test set to trigger

LO2 is set to go through a free swinging test at 10 pm tonight. We have used this script (Git/40m/scripts/SUS/InMatCalc/freeSwing.py) reliably in the past so we expect no issues, it has a error catching block to restore all changes at the end of the test or if something goes wrong.

To access the test, on allegra, type:

tmux a -t LO2

Then you can kill the script if required by Ctrl-C, it will restore all changes while exiting.

Photos: https://photos.app.goo.gl/Ff3yGBprj9xgPbnLA


  16509   Wed Dec 15 16:11:38 2021 AnchalSummaryBHDPart VIII of BHR upgrade - Placed LO1

[Anchal, Yehonathan, Paco]

Today we opened ITMX chamber and removed the following optics and placed them in the Xend flow bench (see attachment 1):

  • POPM1
  • POPM2

Yehonathan brought his first SOS baby next to ITMX chamber. The suspension was carried by hands throughout. He gave me the suspension over the IMC beam tube from where I placed it on the table. I checked through the OSEMs and the face magnets were still on. I could not verify the side magnet but nothing seemed out of place.

I then moved LO1 near its planned place. I had to bolt it at 1 inch North and 0.5 inch West of its planned position because the side OSEM on ITMX is long and protrudes out of the base footprint. Even if it was small, the current layout would make the OSEM pins of the side OSEMs of ITMX and LO1 very near each other. So we can not place LO1 closer to ITMX from current position. This means the layout needs to be redesigned a bit for the modified position of LO1. I believe it will significantly shift and turn the beam from LO1 to LO2, so we might need to change the beam upstream from TT2 onwards. More discussion is required.

Unfortunately, what I thought was clicking photos was just changing modes between video and image mode, so I have no photos from today but only a video that I recorded in the end.

Photos: https://photos.app.goo.gl/23kpCknP3vz7YVrS


Attachment 1: signal-2021-12-15-161437.jpeg
  16510   Wed Dec 15 17:44:18 2021 KojiSummaryBHDPart VIII of BHR upgrade - Placed LO1

If ITMX already has another side magnet, we can migrate the side OSEM of ITMX to the other side. This way, the interference of the OSEMs can be avoided.

  16730   Tue Mar 15 18:45:12 2022 AnchalSummaryBHDPart X of BHR upgrade - BHDBS Path setup

[Paco, Anchal]

BS Chamber work

  • ASL was positioned in nominal place.
  • PR3 was moved to its nominal place from temprorary position.
  • BS Table was rebalanced
  • Earthquake stops were removed from all SOS from BS table (LO2, SR2, BS, PR3)

ITMY Chamber work

  • AS2, AS3, LO3, LO4, and BHDBS were positioned in the nominal place.
  • AS1 was moved to its nominal place from temporary position.
  • ITMY tbale was rebalanced
  • Earthquake stops were removed from all SOS from ITMY table (AS1, AS4, ITMY)
  15075   Thu Dec 5 01:54:39 2019 gautamUpdateLSCPartial CM board path engaged
  • The arm powers could be stabilized somewhat once the CM_SLOW path to MC2 was engaged.
  • However, I was never able to get the AO path to do anything good.
  • Took a bunch of CM board TFs, need to think about what I need to do differently to get this next bit to work.
  • An SR785 is sitting next to the LSC rack hooked up to the CM board. I also borrowed the GPIB unit from the AG4395 to grab data from said SR785.
  • One thing I noticed that the CARM_B (=CM_SLOW) and DARM_B (=AS55_Q) signals both had a DC offset, so maybe this is indicative of some DC offset in the PRMI 3f signals? Right now, I lock the PRMI without any offsets, and as I reduce the CARM offset, I can see the DC value of REFL11_I and AS55_Q changing significantly. To be investigated in tonight's locking.
Attachment 1: AOengaged.pdf
  12672   Wed Dec 7 11:52:48 2016 ericqUpdateIMCPartial IMC ringdowns

The transients are likely due to doppler interference due to the input laser frequency sloshing due to errant control signals after the IMC unlock. I performed a few "partial" ringdowns by reducing the power by about 80% while keeping the IMC servo locked. (Function generator at 0.5Vpp square wave, 0.25V offet. Turned IMC boosts off to increase the stable range of the servo).

I need to work out how to extract the loss from this, I think having a partial ringdown may change the calculations somewhat; the time constants in the trans and refl signals are not identical.

Thanks to Gautams nice setup, it was very easy to take these measurements. Thanks! Code and data attached.

Attachment 2: IMCpartial.zip
  12675   Thu Dec 8 19:01:21 2016 ranaUpdateIMCPartial IMC ringdowns

Mach Zucker on howto do Ringdowns:  https://dcc.ligo.org/LIGO-T900007

  949   Tue Sep 16 10:57:45 2008 YoichiConfigurationPEMParticle counter gain
Since we reduced the integration time of the particle counter by a factor of 10, we had to add a gain of 10
to the EPICS channels C1:PEM-count_full and C1:PEM-count_half.
I asked Alex to change it and he did it. I forgot to ask him to change the gain of C1:PEM-count_half. So now only
C1:PEM-count_full has x10 gain.

C1:PEM-count_full and C1:PEM-count_half are 'Soft Channel' records in the database (Pcount.db). The values are actually
written into the VAL fields directly by an SNL code Particle.o.
Particle.o reads data from the RS-232C port, to which the particle counter is connected. Then it parses the data and put values
into relevant EPICS channels using channel access. This means we cannot change the gain of the channels by modifying the
database file. For example, ASLO field does not have any effect when the value is directly written into the VAL field.
We had to modify the SNL code. Alex modified Particle.st and the new SNL object file is Particle_x10.o sitting in 
/cvs/cds/caltech/target/c1psl/. I modified seq.load so that c1psl loads Particle_x10.o when rebooted.
The source code for the old Particle.st can be found on lesath.ligo.caltech.edu in
I asked Alex to disclose the location of the source of the new code.
In order to compile the SNL code into an object file for Motorola CPU by ourselves, we have to call Dave Barker at LHO.
  16416   Wed Oct 20 11:16:21 2021 AnchalSummaryPEMParticle counter setup near BS Chamber

I have placed a GT321 particle counter on top of the MC1/MC3 chamber next to the BS chamber. The serial cable is connected to c1psl computer on 1X2 using 2 usb extenders (blue in color) over the PSL enclosure and over the 1X1 rack.

The main serial communication script for this counter by Radhika is present in 40m/labutils/serial_com/gt321.py.

A 40m specific application script is present in the new git repo for 40m scripts, in 40m/scripts/PEM/particleCounter.py. Our plan is to slowly migrate the legacy scripts directory to this repo overtime. I've cloned this repo in the nfs shared directory at /opt/rtcds/caltech/c1/Git/40m/scripts which makes the scripts available at all computers and keep them upto date in all computers.

The particle counter script is running on c1psl through a systemd service, using service file 40m/scripts/PEM/particleCounter.service. Locally in c1psl, /etc/systemd/system/particleCounter.service is symbollically linked to the file in the file.

Following channels for particle counter needed to be created as I could not find any existing particle counter channels.


These are created from 40m/softChansModbus/particleCountChans.db database file. Computer optimus is running a docker container to serve as EPICS server for such soft channels. To add or edit channels, one just need to add new database file or edit database files in thsi repo and on optimus do:

controls@optimus|~> sudo docker container restart softchansmodbus_SoftChans_1

that's it.

I've added the above channels to /opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini to record them in framebuilder. Starting from 11:20 am Oct 20, 2021 PDT, the data on these channels is from BS chamber area. Currently the script is running continuosly, which means 0.3u particles are sampled every minute, 0.5u twice in 5 minutes and 1u, 2u, and 5u particles are sampled once in 5 minutes. We can reduce the sampling rate if this seems unncessary to us.

Attachment 1: PXL_20211020_183728734.jpg
  16420   Thu Oct 21 11:41:31 2021 AnchalSummaryPEMParticle counter setup near BS Chamber

The particle count channel names were changes yesterday to follow naming conventions used at the sites. Following are the new names:


The legacy count channels are kept alive with C1:PEM-count_full copying C1:PEM-BS_DUST_1000NM channel and C1:PEM-count_half copying C1:PEM-BS_DUST_500NM channel.

Attachment one is the particle counter trend since 8:30 am morning today when the HVAC wokr started. Seems like there was some peak particle presence around 11 am. The particle counter even counted 8 counts of particles size above 5um!


Attachment 1: ParticleCountData20211021.pdf
  16421   Thu Oct 21 15:22:35 2021 ranaSummaryPEMParticle counter setup near BS Chamber

SVG doesn't work in my browser(s). Can we use PDF as our standard for all graphics other than photos (PNG/JPG) ?

  16422   Thu Oct 21 15:24:35 2021 ranaSummaryPEMParticle counter setup near BS Chamber

rethinking what I said on Wednesday - its not a good idea to put the particle counter on a vac chamber with optics inside. The rumble from the air pump shows up in the acoustic noise of the interferometer. Let's look for a way to mount it near the BS chamber, but attached to something other than vacuum chambers and optical tables.


I have placed a GT321 particle counter on top of the MC1/MC3 chamber next to the BS chamber.


ELOG V3.1.3-