We built a power supply for the accelerometer shown in Attachment 1 based on the diagram shown in the Wilcoxon manual and shown in attachment 2. We used a 9V power supply and a capacitor value of 680uF. We did not use a constant current diode.
When hooked up to an oscilloscope we saw vibrations from hitting our hands on the table but we did not see the same amplitude in the negative and positive directions. For example, when I held the accelerometer and moved it down you would see a dip then a peak as the accelerometer accelerated down then accelerated up when I stopped the down word movement. But weirdly when I did the opposite (moved the accelerometer up the same dip then a peak appeared. This is a little concerning because it should be the opposite. it should be a peak then a dip. This in addition to the seemingly decreased sensitivity in one direction make me think that the accelerometer is broken.
I labeled the box with "might be broken" before I returned it to the cryo lab.
BS, ITMX and ETMX were aligned to get flashing in the X arm.
I aligned the POX beam on the ITMX table using a mixture of the old POP and POX optics. The beam was stirred to the POX11 RFPD. We measure the DC power using a scope but we see nothing. We went and saw that the POX11 cable was not connected to RF rack so we connected it along with some other RFPD cables.
We return but there is still no DC. We ndscope C1:LSC-POX11_I_ERR_DQ C1:LSC-POX11_Q_ERR_DQ and maximize the signal (attachment). The readout is very weak though. It should be as strong as POY which we already observed to have good SNR.
We also noticed that the one of the beam dumps for the POX RFPD is not glued and easily falls down.
[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.
Tega and Paco reported that the UR OSEM of AS1 lost the response.
- I have checked the LED MON (left) of the satellite amp for AS1. CH1/2/3 had 5V -> This indicates that the OSEM LEDs are (most likely) functioning.
- Then I went to the ITMY flange and connected the OSEM emulator instead of the Dsub25 cable. The attachment shows that the UR OSEM LED/PD worked fine with the OSEM emulator. WIth the vacuum flange connected it lost the response.
This indicates that the AS1 UR OSEM problem is localized in the chamber. Please check if the DSUB pins are touching the table or something else.
Coil Drivers LO2, SR2, AS4, and AS1 have been updated a reinstalled into the system.
LO2 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 Unit: S2100008
LO2 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 Unit: S2100530
SR2 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 Unit: S2100614
SR2 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 Unit: S2100615
AS1 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 Unit: S2100610
AS1 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 Unit: S2100611
AS4 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 Unit: S2100612
AS4 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 Unit: S2100613
[JC, Tega, Ian, Paco]
We found that the UR cable was clamped to the table by one of the ITMY OPLEV steering mirror mounts that was recently installed. After freeing the cable, the UR signal is now active again.
Nice. Please put this information on the DCC pages of the coil driver units. You'll find links to all the units in this document tree LIGO-E2100447. For each page, click on "Change Metadata" from the left panel and add the change made to the resistor (including the resistor name on PCB, previous and new value), and add a link to your previous elog post which has more details like photos, to "Notes and Changes", and upload an updated version of the circuit schematic by creating an annotation in the previous circuit schematic pdf. Every unit that has a serial number in the lab has a DCC page (if not, we should create one) where we should track all such hard changes.
If someone gets time, let's put in all the cable posts and clean up our cable routing on the tables.
While the pumpspool is vented, I thought it would be a convenient time to change out the tip seal on the TP3 forepump. This one had not been changed since 2018, so as preventative maintence I had JC remove the pump and begin cleaning/installing the new tip seal.
Unfortunately the tip seal broke, but I have ordered another. We should have this pump ready to go late next week. If one is needed sooner, there is a spare IDP 7 pump we can install as the TP3 forepump.
We recieved an overlay from Chris Stoughton which he used for a ZCU11 board. The overlay is supposed to be compatible with the RFSoC 2x2 and help enable the Multi-Tile Synchronization (MTS) we need. He also provides a .py with the necessary low level connection to the board and its memory along with a few sample notebooks.
Progress So Far:
Coming in this morning, I checked on the Nitrogen tanks to check the level. One of the tanks were empty, so I went ahead and swapped it out. One tank is at 946 PSI, the other is at 2573 PSI. I checked for leaks and found none.
For your (and mine) info:
N2 pressure can be monitored on the 40m summary page: https://nodus.ligo.caltech.edu:30889/detcharsummary/day/20220425/vacuum/
(you need to hit "today" to go to the current status)
[Anchal, Tega, JC]
We installed cable posts in ITMY, BS, and ITMX chambers for all the new suspensions. Now, there is no point where the OSEM connections are hanging freely.
In BS chamber, we installed one post for LO2 near the north edge of the table and another post for PR3 on the Western edge with the blue cable running around the table on the floor.
In ITMY chamber, we installed the cable post in between AS1 and AS4 with the blue cables running around the table on the floor. This is to ensure the useful part of the table remains empty for future and none of the OSEM cables are taught in air.
I investigated this issue today. At first, it seemed that only new suspension testpoints are inaccessible. I was able to use diaggui for a measurement on MC2. The DAQ network cable between 1X4 and 1Y1 was tied and is very taught now (we should relieve this as soon as possible, best solution is to lay down a longer cable over the bridge). My hypothesis is that the DAQ network might have broken while tying this cable and it probably did not come back since then.
The simplest solution would have been to restart c1su2 models. As I restarted those models though, I found that c1lsc and c1sus models failed. This is very unusual as c1su2 models are independent and share nothing with the other vertex models. So I had to restart all the FE computers eventually. But this did not solve the issue. Worse, now the DAQ isn't working for the vertex machiens as well.
Next step was to try restarting fb1 itself. We switched off all the FE computers, restarted fb1, stopped daqd_* processes, reloaded gpstime module, restarted open-mx, mx, nds and daqd_* process. But the mx.service failed to load with following error message:
● mx.service - LSB: starts MX driver for Myrinet card
Loaded: loaded (/etc/init.d/mx)
Active: failed (Result: exit-code) since Mon 2022-04-25 17:18:02 PDT; 1s ago
Process: 4261 ExecStart=/etc/init.d/mx start (code=exited, status=1/FAILURE)
Apr 25 17:18:02 fb1 mx: Loading mx driver
Apr 25 17:18:02 fb1 mx: insmod: ERROR: could not insert module /opt/mx/sbin/mx_mcp.ko: File exists
Apr 25 17:18:02 fb1 mx: insmod: ERROR: could not insert module /opt/mx/sbin/mx_driver.ko: File exists
Apr 25 17:18:02 fb1 systemd: mx.service: control process exited, code=exited status=1
Apr 25 17:18:02 fb1 systemd: Failed to start LSB: starts MX driver for Myrinet card.
Apr 25 17:18:02 fb1 systemd: Unit mx.service entered failed state.
(Ignore the timestamp above, I ran the command again to capture the error message.)
However, I was able to start all the FE models without any errors and daqd processes are also all running without showing any errors. Everything is green in CDS screen with no error messages. But the only thing still wrong is mx.service which is not running.
From my limited knowledge and experience, mx.service is a one-time script that mounts mx devices in /dev and loads the mx driver. I tried running the script /opt/mx/sbin/mx_start_stop :
This gave the same error. On searching little bit online, "insmod: ERROR; cound not insert module" error comes up when the kernel version of the driver doesnot match the Linux kernel (whatever that means!). Such deep issues should not appear out of nowhere in a previosuly perfectly runnig system. I'll check around more what changed in fb1, network cables etc.
I have designed new cable supports for the new ribbon cables running up the side of the tables in the vacuum chambers. This is a ribbon cable version of the existing cable clamp cf D010120
The clamps that I have designed (shown in basic sketch attachment 1) will secure the cable at each of the currently used cable supports.
The support consists of a backplate and a frontplate. The backplate is secured to the leg of the table using a threaded screw. The frontplate clamps the cable to the backplate using two screws: one on either side. Between two fascinating points, the cable should have some slack. This should keep the cable from being stiff and help reduce the transfer of seismic noise to the table.
It is possible to stack multiple cables in one of these fasteners. Either you can put two cables together and clamp them down with one faceplate or you can stack multiple faceplates with one cable between each faceplate. in this case the stack would go backplate then cable then faceplate then cable then the second faceplate. this configuration would require longer screws.
The exact specifics about which size screws and which size plates to use still have not been measured by me. But it will happen
We connected a 8 MHz signal generator to the device in order to sync up the ADCs and DACs and hopefully get phase data.
Some things to note:
Xilinx RF Manual: https://docs.xilinx.com/v/u/2.4-English/pg269-rf-data-converter
18 (9 pairs) Coil Drivers have been modified. Namely ETMX/ITMX/ITMY/BS/PRM/SRM/MC1/MC2/MC3.
ETMX Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100624 ETMX Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100631
ITMX Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100620 IMTX Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100633
ITMY Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100623 ITMY Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100632
BS Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100625 BS Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100649
PRM Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100627 PRM Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100650
SRM Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100626 SRM Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100648
MC1 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100628 MC1 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100651
MC2 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100629 MC2 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100652
MC3 Coil Driver 1 (UL/LL/UR)now has R=100 // 1.2k ~ 92Ohm for CH1/2/3 S2100630 MC3 Coil Driver 2 (LR/SD)now has R=100 // 1.2k ~ 92Ohm for CH3 S2100653
Will be updating this linking each coil driver to the DCC
[Anchal, Paco, JC]
We had to open ITMY, ETMY chamber doors to get the cavity aligned again. Once we did that, we regained cavity flashing and were able to align the input injection and cavity alignment to get transmission flashing to 1.0 (C1:LSC-TRY_OUT_DQ). JC later centered both ITMY and ETMY oplevs. The ITMY oplev had become completely out of range.
We also opened ITMX, ETMX chamber doors to get Xarm alignment. Again, it seems that ITMX had moved a lot due to cable post installation.
To be continued
This would be a daily first task in the morning. We'll need to check the status of arm alignment and optimize it back to maximum every morning for the rest of the day's work.
Today, when I came, on openin gthe PSL shutter, IMC was aligned good, both arms were flashing but YARM maximum transmission count was around 0.7 (as opposed to 1 from yesterday) and XARM maximum transmission count was 0.5 (as opposed to 1 from yesterday). I did not change the input alignment to the interferometer. I only used ITMY-ETMY to regain flashing count of 1 on YARM and used BS and tehn ITMX-ETMX to regain flashing count of 0.9 to 1 in XARM.
Even thought the oplevs were centered yesterday, I found the oplev had drifted from the center and the optimal position also is different for all ooptics except EMTY and BS. It is worth nothign that in optimal position both PIT and YAW of ITMY and ITMX are off by 70-90 uradians and ETMX Pit oplev is off by 55 uradians.
I tried out this stack today and found some change of plans.
tl,dr; Jordan is preparing PLS-T238 and TR-1.5 with venting holes and C&B and they would be ready by tomorrow. I have collected all other parts for assembly, still looking for the mirror but I know other lab members know where it is, so no big issue there.
The assemly of this mirror is complete. A slight change here as well, we were supposed to use the former POYM1 (Y1-2037-0) mirror for POP_SM5 but I could not find it. It was stored on the right most edge of the table (see 40m/16450), but it is not there anymore. I found another undocumented mirror on the flow bench on the left edge marked (2010 July: Y1-LW1-2037-UV-0-AR) which means this mirror has a wedge of 1 degree and an AR coating as well. We do not need or care about the wedge or AR coating, so we can use this mirror for POP_SM5. Please let me know if someone was saving this mirror for some other purpose.
I'll finish assembly of POP_SM4 tomorrow and install them in ITMX chamber and resurrect POP path.
Here is more detail of the POP_SM4 mount assembly.
It's a combination of BA2V + PLS-T238 + BA1V + TR-1.5 + LMR1V + Mirror: CM254-750-E03
Between BA1V and PLS-T238, we have to do a washer action to fix the post (8-32) with a 1/4-20 slot. Maybe we can use a 1" post shim from thorlabs/newport.
Otherwise, we should be able to fasten the other joints with silver-plated screws we already have/ordered.
I think TR-1.5 (and a shim) has not been given to Jordan for C&B. I'll take a look at these.
We investigated the low power issue with POX11 photodiode.
Restored arm algiment to get 0.8 max flashing on YARM and 1 max flashing on XARM. I had to move input alignment using TT2-PR3 pair and realign YARM cavity axis using ITMY-ETMY pair.
I would like to advertise this useful tool that I've been using for moving cavity axis or input beam direction. It's a simple code that makes your terminal kind of videogame area. It moves two optics together (either in same direction or opposite direction) by arrow key strokes (left, right for YAW, up, down for PIT). Since it moves two optics together, you actually control the cavity axis or input beam angle or position depening on the mode.
Jordan and I, in order to start pumpig down the RGA Volume, we began by opening V7 and VM. Afterwards, we started RP1 and RP3. After this, the pressure in the line between RP1, RP3, and V6 dropped to 3.4 mTorr. Next, we tried to open V6, although an error message popped up. We haven't been able to erase it since. But we were able to turn on TP2 with V4 closed. The pressure in that line is reporting 1.4 mTorr.
PRP on the sitemap is giving off an incorrect pressure for the line between RP1, RP3, and V6. This is verified by the pressure by the control screen and the physical controller as well.
[Paco, Anchal, Yuta]
We opened the BSC and ITMX chamber in the morning (Friday) to investigate POX11 beam clipping. We immediately found that the POX11 beam was clipping by the recently installed cable posts, so luckily no major realingment had to be done after reinstalling the cable post in a better location.
Because we had the BSC open, we decided to steer the AS1 mirror to align the AS path from ITMY all the way to the vertex chamber. Relatively small AS1 offsets (of ~ 2000 counts each) were added on PIT / YAW to center the beam on ASL (there is slight clipping along PIT, potentially because of the AS2 aperture. We then opened the vertex chamber and located the AS beam with relative ease. We decided to work on this chamber, since major changes propagate heavily downstream (simply changing the IMC pointing).
Anchal removed old optics from the vertex chamber and we installed the steering pair of mirrors for AS path. This changed the balance of the vertex table by a lot. By using the MC REFL camera beam spot we managed to coarsely balance the counterweights and recover the nominal IMC injection pointing. Simply reenabling the IMC autolocker gave us high transmission (~ 970 counts out of the typical 1200 these days).
The final IMC alignment was done by Anchal with delicate PIT motion on the input injection IMC miror to maximize the transmission (to our satisfaction, Anchal's motion was fine enough to keep the IMC locked). The end result was quite satisfying, as we recovered ~ 1200 counts of MC transmission.
Finally, we looked at the arm cavity transmission to see if we were lucky enough to see flashing. After not seeing it, we adjusted TT1 / TT2 to correct for any MMTT1 pitch adjustment needed after the vertex table rebalancing. Suprisingly, we didn't take too long and recovered the nominal arm cavity pointing after a little adjustment. We stopped here, but now the vertex table layout is final, and AS beam still needs to be aligned to the vertex in-air table.
Jordan recieved the new tip seal Friday afternoon and I continued the replacement process in the morning. Finishing up, we proceeded to test the pump in the Clean and Bake room. The pump's pressure lowered to 110 mTorr, and we continue pumping so the seal can recieve a good fitting.
Update: We have confirmed the pump is working great and have reinstalled this back into the vacuum system. Note: The same O-Rings were used.
The DCC has been updated, along with the modified schematic. Links have been attached.
We found that one of the Y1-1037-45P marked mirror that we used was actually curved. So we removed it and used a different Y1-1037-45P mirror, adjusted the position of the lens and got the beam to land on POX11 RFPD successfully.
Then in control room, we maximized the POX11_I_ERR PDH signal amplitude by changing C1:LSC-POX11_PHASE_R to 42.95 from -67.7. We kept the C1:LSC-POX11_PHASE_D same at 90. We were getting +/- 200 PDH signal on POX_I_ERR.
Then in our attempt to lock the XARM, when we ran the "Restore XARM (POX)" script, YARM locked!
We are not sure why the YARM locked, we might have gotten lucky today. So we ran ASS on YARM and got the transmission (TRY_OUT) stable at 1. The lock is very robust and retrievable.
Coming back to XARM, we realized that the transmission photodiode used for XARM was the low-gain QPD instead of the thorlabs high gain photodiode. The high-gain photodiode was outputing large negative counts for some reason. We went to the Xend to investigate and found that the high gain photodiode was disconnected for some reason. Does anyone know/remember why we disconnected this photodiode?
We connected the photodiode back and it seems to work normally. We changed the photodiode selection back to high gain photodiode for TRX and on 40 dB attenuation, we see flashing between 1.4 to 1.6. However, we were unable to lock the XARM. We tried changing the gain of the loop, played a little bit with the trigger levels etc but couldn't get it to lock. Next shift team, please try to lock XARM.
Jordan, Tega, JC
Issue has been resolved. Breaker on RP1 was tripped so the RP1 button was reporting ON, but was not actually on which continuously tripped the V6 interlock. Breaker was reset, RP1 and RP3 turned on. The V6 was opened to rough out the RGA volume. Once, pressure was at ~100mtorr, V4 was opened to pump the RGA with TP2. V6 was closed and RP1/3 were turned off.
RGA is pumping down and will take scans next week to determine if a bakeout is needed
I installed POP_SM4 and POP_SM5 in the ITMX chamber in the nominal positions. This must have affected the ITMX Oplev because I could see that one of the ITMX oplev beam was going through POP_SM5. It needs to be changed in order to follow the original plan. However, since POP_SM5 is a 1064 line mirror, it is transparent to the opleve beam, so maybe we can just use the ITMX oplev in the current fashion.
[Tega, Yehonathan, Koji, Yuta]
We tried to align AS path this afternoon.
IMC is not aligned now after the work today
Green mirrors/perisocope in IMC chamber were removed since some of them was clipping the AS beam, and this changed the balance of the IMC stack and thus MC1 and MC3 alignment.
Summary of changes:
- Rotated AS2 in roll by 90 deg to have more aperture for the transmission (photo)
- IR beams are now centered on AS1, AS2, AS3 and AS4 (photo, photo)
- Moved ASL towards -X direction for about 1/4 inch
- Installed GRY_SM2 at the nominal position (re-used GR_SM3 from IMC chamber)
- Removed green optics GR_SM4, GR_SM3, GR_PERI2L (GR_PERI2L is now stored at Xend)
- Removed IFI camera mirrors FIV1, FIV2 (they are now stored at Xend) (photo, photo)
- GR_SM4 mount is now reused as GRY_SM1 (Y2-2037-0 is now mounted instead of previously mounted Y2-LW1-2050-UV-45P/AR), and GRY_SM1 is installed at the nominal position (photo)
- Moved weights to balance the stack
OMC chamber (we don't have OMC in this chamber...)
- We swapped AS5 and AS6 so that the nobs comes in -X direction to have more spacing between AS beam and IMC REFL beam (photo)
- Moved weights to balance the stack
What we did:
1. Misaligned ITMX and use ITMY reflected beam to align AS path
2. Centered the IR beam on AS1 using SR2
3. Centered the IR beam on AS2 and ASL using AS1. AS2 was rotated in roll by 90 deg to have more aperture for the transmisson.
4. Centered the IR beam on AS3 using AS2 nobs, centered the IR beam on AS4 by rotating AS3 in yaw.
5. "AS beam" (it turned out that what we are looking was actually not the AS beam!! Some stray light) was in +X direction by 1 inch or so at AS5. Moving AS5 to center the beam would clip IMC REFL beam. So we swapped AS5 and AS6 so that the nobs comes in -X direction to have more spacing between AS beam and IMC REFL beam.
6. Balanced OMC chamber stack again using IMC REFL beam as a referece (bring the IMC REFL beam to the reference red circle on the monitor).
7. Tweaked the alignment of TT1 and TT2 to have Yarm flashing to ~0.9 in TRY.
8. Moved AS5 towards +X by an inch or so to center the "AS beam."
9. Moved ASL towards -X direction for about 1/4 inch and re-centered the beam by AS1 to see if the "AS beam" gets far from IMC REFL at OMC chamber, but the "AS beam" didn't move much.
10. By blocking the beam from ITMY, we found that "AS beam" was not the actual one.
11. Opened IMC chamber and found that AS beam is blocked by the past optics.
12. Removed old green optics and IFI camera mirrors. GR_SM4 mount and GR_SM3 were reused as mentioned above.
13. Tried to balance IMC chamber stack to recover IMC alignment. We used IMC REFL beam as a reference, but it was hard to completely bring the IMC REFL beam to the reference red circle on the monitor. It is now off by a beam diameter or so. No IMC flashing now.
Theoretically, balancing IMC chamber stack would recover all the IFO alignment, but maybe tough. It is maybe easier to align MC1 and MC3 to have IMC locked. Assuming input pointing to IMC is not drifted too much, we should be able to recover Yarm flashing by tweaking TT1 alignment only. However, MC3 SD OSEM is at the edge of the range. We might have to balance the stack more or tweak SD OSEM position.
I feel like there is an instability in my thought process on this. Before my tendency to try to scale and generalize this problem brings me to a full stop I will make small but quick progress.
First thing is to calculate the noise budget for a simple Michelson. The involved optics are:
all sensed with OSEMs and OpLevs only.
Things to fetch:
1. OSEM sensing noise. Where do I get the null stream (AKA butterfly mode)?
2. Oplev noise, look at the SUM channel (or this elog)
3. Actuation TF. Latest elog.
4. Coil driver noise. Going to take the HP supply curve from this elog.
5. Seismic noise + Seismic stack TF. Or maybe just take displacement noise from gwinc.
6. Laser noise. Still need to search.
7. DAC noise. Still need to search.
I'm planning on simulating the BHD readout noise in a manner very similar to the ALS noise model using Simulink. I've made a sketch of the model for the longitudinal DOFs (attached). A model for ASC will be similar but with more measurement devices (OpLevs, QPDs, WFSs).
I'm not pretending to simulate everything in this diagram on the first go, it is just a sketch of the big picture.
[Paco, JC, Anchal]
We balanced the IMC table back again to point that got us 50% of nominal transmission from IMC. Then we tweaked the steering mirror for injection to IMC to get up to 90% of nominal transmission. Finally, we used WFS servo loop to get to the 100% nominal transmission from IMC. However, we found that the WFS loop has been compromised now. It eventually misaligns IMC if left running for a few minutes. This needs to be investigated and fixed.
We aligned the BS, ITMY, and ETMY PIT and YAW to get the flashing on X-arm whilst also keeping the flashing of Y-arm. From attachment 1, it is clear that POXDC photodiode is not receiveing any light, so our next task is to work on POX alignment.
We needed to sort out the POXDC signal so we could work on X-arm alignment. Given that POXDC channel value was approx 6 compared to POYDC value of approx. 180, we decided to open the ITMX chamber to see if we could improve the situation. We worked on the alignment of POX beam but could not improve the DC level which suggests that this was already optimized for. As an aside, we also noticed some stray IR beam from the BS chamber, just above the POX beam which we cold not identify.
Next we moved on to the POP beam alignment, where we noticed that the beam level on LO1 and POP_SM4 was a bit on the high side. Basically, the beam was completely missing the 1" POP_SM4 mirror and was close to the top edge of LO1. So we changed TT2 pitch value from 0.0143 to -0.2357 in order to move the beam position on POP_SM4 mirror. This changed the input alignment, so we compensated using PR2 (0.0 -> 49.0) and PR3 (-5976.560 -> -5689.800). This did not get back the alignment as anticipated, so we moved ITMY pitch from 0.9297 to 0.9107. All of these alignment changes moved the POP beam down by approx 1/5 of an inch from outside the mirro to the edge of POP_SM4 mirror, where about half of the beam is clipped.
We need to repeat these aligment procedures with say 1.5 time the change in TT2 pitch to center the beam on POP_SM4 mirror.
We first aligned the single arm cavity resonance for both arms to get maximum flashing. As we opened the chamber, I found that the POP beam was mostly hitting the POP_SM4 mirror but was clipping about 2 mm on the top edge.
I used TT2-PR3 to lower the injection beam angle and moved pairs of ITMY-ETMY, and ITMX-ETMX to recover as much flashing as I could in the both arms. Then, I moved PR2 in pitch from 49 to 71 to maximize the arm flashing again. After these steps, the POP beam was clearly within the POP_SM4 mirror but still in the upper half of the optic and there was maybe just a mm of clearance from the top edge. I decided to raise POP_SM4 mirror by 0.14" spacer. Now the beam is still in upper half of the mirror but has a good clearance from the edge.
The POP beam is coming outside in the in-air table at as a rising beam in the nominal path near the center of the window. This beam needs to be directed to the POP camera and RFPD on the far-side of the table.
In order to setup POP camera and RFPD on the ITMX table, we decided to first work on the IMC and X/Y-arm alignment.
We zeroed IMC WFS outputs and aligned IMC manually to get IMC transmission of 1200 and reflection of 0.35.
We used the new video game tool that moves the pairs of mirrors - PR3 & ETMY, ITMY & ETMY - in common and differential modes. This brought the Y-arm flashing to 0.8. Note that we used the _OFFSET bias values for PR3 & ETMY alignment instead of the _COMM bias values.
We repeated the same procedure of moving the pairs of mirrors - BS & ETMX, ITMX & ETMX - in common and differential modes but manually this time. This brought the X-arm flashing to ~1.0.
I have made a Simulink diagram to use in the MICH modeling (attachment) for the homodyne angle detection scheme. The model will be used for each optic separately and the noises will be combined in quadrature.
I gathered some more bits of info to fill the Simulink boxes. This is what I have so far:
# Displacement noises from gwinc
# OSEM sensing noise from the null stream
# OpLev noise from SUM channel + Seismic motion
freq = np.logspace(1, 4, 100)
coil_driver_noise = 1*freq/freq # pA/sqrt(Hz), elog 15846
RIN = 1e-2*freq/freq #1/sqrt(Hz), elog 16082
freq_noise = (1e6/freq**2) #Hz/sqrt(Hz), elog 15431
dark_noise = 1e-8 #V/sqrt(Hz) https://wiki-40m.ligo.caltech.edu/Electronics/RFPD/AS55
ADC_noise = 1e-6 #V/sqrt(Hz)
DAC_noise = 1e-6 #V/sqrt(Hz), elog 13003
#POS->BHD from Finesse
#RIN->BHD from Finesse
#Frequency noise->BHD from finesse
#Control filters from MEDM
#Whitening filters from https://wiki-40m.ligo.caltech.edu/Electronics/WhiteningFilters
#Dewhitening filters from elog 12983
DAC_gain = 6.285e-4 #V/cts, elog 16161
coil_driver_gain = 31 # elog 15534
coil_driver_TF = 0.016 #N/A per coil, elog 15846
coil_R = 20e3 #Ohm,, elog 15846
SUS_TF = 1/(0.25*freq**2) #m/N, single pendulum
OSEM_TF = 2*16384*1e3 #cts/m, https://wiki-40m.ligo.caltech.edu/Calibration
ADC_TF = 1638.4 #cts/V
DCPD_responsivity = 0.8 #A/W
DCPD_transimpedance = 1e3 #V/A
We investigated why WFS loop wasn't working. It seemed like WFS1 PIT error signal has a huge offset which would push the loop to misalign all optics' PIT. So we did the following steps:
I made the first pass at a tool to measure the quantization noise of specific filters in the 40m system. The code for which can be found here. It takes the input to the filter bank and the filter coefficients for all of the filters in the filter bank. it then runs the input through all the filters and measures the quantization noise at each instance. It does this by subtracting the 64-bit output from the 32-bit output. Note: the actual system is 64 bit so I need to update it to subtract the 64-bit output from the 128-bit output using the long double format. This means that it must be run on a computer that supports the long double format. which I checked and Rossa does. The code outputs a number of plots that look like the one in Attachment 1. Koji suggested formatting a page for each of the filters that is automatically generated that shows the filter and the results as well as an SNR for the noise source. The code is formatted as a class so that it can be easily added to the IFOtest repo when it is ready.
I tracked down a filter that I thought may have lower thermal noise than the one that is currently used. The specifics of this will be in the DCC document version 2 that I am updating but a diagram of it is found in attachment 2. Preliminary calculations seemed to show that it had lower quantization noise than the current filter realization. I added this filter realization to the c code and ran a simple comparison between all of them. The results in Attachment 3 are not as good as I had hoped. The input was a two-toned sin wave. The low-level broadband signal between 10Hz and 4kHz is the quantization noise. The blue shows the current filter realization and there shows the generic and most basic direct form 2. The orange one is the new filter, which I personally call the Aircraft Biquad because I found it in this paper by the Hughes Aircraft Company. See fig 2 in paper. They call it the "modified canonic form realization" but there are about 20 filters in the paper that also share that name. in the DCC doc I have just given them numbers because it is easier.
1) I need to make the review the qnoisetool code to make it compute the correct 64-bit noise.
a) I also want to add the new filter to the simulation to see how it does
2) Make the output into a summary page the way Koji suggested.
3) complete the updated DCC document. I need to reconcile the differences between the calculation I made and the actual result of the simulation.
As I went to correct the ITMX Oplev mirrors, I found that both mirrors were placed in very different positions than the design position. Part of the reason I think was to preserve outside oplev path, and party because a counterweight was in ITMXOL1 position. I had to do following steps to correct this:
During the above work, i must have kicked the cable between the vacuum flange and the satellite amplifier box for ITMX. This disconnected all the OSEMs and Coils. We tried several things to debug this and finally found that nudging the connections on Sat Amp box brought the OSEMs and coils back online. Note that the connector was not partially out or in a state that obviously showed disconnection of the pins. I'm glad we are putting in new electronics soon for the vertex optics as well.
Started work on the relocating the green transmission optics, cameras and PDs. Before removing the any of the optics, we checked and confirmed that the PDs and Cams are indeed connected to the GRN TRX/Y medm channels. Then added labels to the cables before moving them.
Relocated Optics & PDs & Cameras:
Don is working on finalizing the BHD Platform design. All the components on the BHD platform are almost populated and aligned.
Don is still working on the table legs so that we can detach the legs when we need to float the table in the future.
The BHD BS mount will have a third picomotor so that we can steer 3 dof with the mount while the remaining dof needs to be provided by the OMC.
The BHD BS position is going to be adjusted so that the incident and trans beams have sufficient clearance.
The OMC legs (kinematic mounts) need more work so that we can adjust their positions for initial setup while they can be the reference for the reproducible placement of the OMCs.
The OMCs are rigidly held with the legs. For the damping of the 1-kHz body bode, which has a relatively high Q, there will be a dissipative element touching the glass breadboard.
I quickly ran the FEA model to check the resonant freqs of the BHD platform.
The boundary conditions were:
Don has optimized the cut-out size for the OMCs to increase the rigidity of the plate. Also, the ribbed grid is made at the bottom side.
The lowest mode is at 168Hz. Because there is no leg around, it seems reasonable to have this kind of mode as the fundamental mode.
The other mode lined up at 291Hz, 394Hz, 402Hz, ...
The mode freqs will be lower once the platform is loaded. But as the unloaded platform mode, these mode freqs sound pretty good numbers.
Tega and I cleaned up the BS OPLEV Table and took out a couple of mirrors and an extra PD. The PD which was removed is "IP-POS - X/Y Reversed". In addition to this, the cable is zip-tied to the others located on the outside of the table in case this is required later on.
Next, we placed the cameras and mirrors for the green beam into their postions. A beam splitter and 4 mirrors were relocated from PSL table and placed onto the BS Oplev table to complete this. I will upload the picture of the newly updated photo with arrows of the beam routes.
Followed the steps below to complete the ITMX optlev installation. The ITMX optlev return beam now reaches its QPD without being blocked by the input steering mirror.
Although, I centered the ITMX optlev readout, this was not done when the XARM flashing is maximized bcos the IMC chamber was being worked on, so this should be done later when the IR beam is back.
We installed GRX_SM1, GRX_SM2, and finished aligning the GRY_SM1, and GRY_SM2 steering mirrors in the BS and IMC Chambers. GRY_SM1 was slightly misplaced (by ~ 2 inches), so we had to move it slightly. Luckily this didn't grossly misaligned the IMC, and we could recover quickly by touching MC1 & MC3 pitch, and MC1 slight yaw.
Then, Yuta installed GRX_SM1, and GRX_SM2 by repurposing two 45 AOI P-Pol GR transmission mirrors on the flowbench. Because one of the weights on the BSC was in the way of GRX_SM2, it was shifted it before installation. This probably shifted the balancing of the whole table. The GRY beam is still not lock-able to the YARM, so as a proxy for GRY transmission beam we used the slight GRX reflection from the BS, and noted slight clipping through PR3 (in transmission). This should probably be checked with GTRY.
We believe this is the last installation operation of this vent.
We made sure the WFS feedback loop is working, and realigned the arm cavities to be flashing.
Paco and I began aligning the Green Beam in the BS Oplev Table. while aligning the GRN-TRX, the initial beam was entering the table a bit low. To fix this, Paco went into the chamber and correcting the pitch with the steering mirror. The GRN-TRX is now set up, both the PD and Camera. Paco is continuing to work on the GRN-TRY and will update later on today.
In the morning, I will update this post with photos of the new arrangement of the BS OPLEV Table.
Update Wed May 11 16:54:49 2022
GRY is now better mode matched to the YARM and is on the edge of locking, but it more work is needed to improve the alignment. The key difference this time with respect to previous attempts was to scan the two lenses on translation stages along the green injection path. This improved the GTRY level by a factor of 2.5, and I know it can be further improved. Anyways, the locked HOMs are nicely centered on the GTRY PD, so we are likely done with the in-vac GTRY GTRX alignment.
Update Wed May 12 10:59:22 2022
The GTRX PD is now set up and connected. The camera have been set to an angle because the cable to connect it is too thick for the camera to maintain its original position along the side.
Tega and I went in to adjust the POP being in the ITMX Table. The beam entered the table high, so we adjusted the this by adding mirrors (The highlighted in Turqoise are mirrors which adjust the pitch of the beam). All the mirrors are set and we are now in the process of adjusting the PD.
Got POP beam centered on camera and nominally on the two PDs. Attachment #1 shows "carrier" camera.
We finally managed to steer the AS beam from ITMY chamber, through BS and IMC chambers, to the in-air AP table.
We moved the AS5 mirror north to its nominal position and we also moved the ASL lens on BS chamber back to its nominal position. Attached photos are taken after today's alignment work.