The OMC PZT ac response was resorded was not as expected and a remeasurement will be attempted this week. Data: https://www.dropbox.com/s/7pf0k6awoa4wg0z/230503.zip?dl=0
The writing of this elog is still on going
[Dean, Stephen, Koji]
4th OMC production was completed.
== PZT connector assembly ==
Dean and Stephen already crimped the pins to the PZT wires in the previous session.
We wanted to complete this cable by inserting the pins into the mighty mouse connector
This MM connector has the pin1 at the top left and numbered clock wise when it is seen from the mating side with the center notch up.
We looked at D1300589. This drawing has some inconsistency in the description (LV Piezo at the left side turns to HV Piezo at the right side), but it is not an issue as we are supposed to have two identical (or similar) PZTs.
Here the arrangement of the MM connectors:
- Pin 1: PZT1 Pos
- Pin 2: PZT1 Neg
- Pin 3: PZT2 Pos
- Pin 4: PZT2 Neg
== DCPD/QPD cable installation to the DCPD/QPD housings ==
We opened the cable bags and found that they were not completed. The cables didn't have face parts. We found the face parts in the cable parts plastic box, but the screws were missing. We had to send one to pick up screws from the OMC lab while the others were working on inserting helicoils into the cable ASSYs.
We also found the ancient elog about the cables. This told us that the cable set we had was not the proper one, but rather spares with all the long variants of the cables. This meant that the routing needed to be different from the past 3 OMCs.
The flex PCB boards have solder bumps sticking out. This prevented the front pieces from being flush with the back piece. It was slightly improved by clipping a few solder marks (Attachments 1/2). The cables were inserted into the DCPD/QPD housings. To align the connector heads properly, we installed dummy (i.e., non-high-QE PDs with caps) PDs to the housing. The QPDs were necessary to be removed from the housing as it was known that the insertion was very difficult.
DCPD cable for DCPD1 (Trans side): D1300372 S1301809
DCPD cable for DCPD2 (Refl side): D1300372 S1301807
QPD cable for QPD1 (Refl side): D1300375 S1301816
QPD cable for QPD2 (Trans side): D1300375 S1301814
Cable installation on the connector harness
We flipped the OMC (manually) so that we could work on the suspension side. The connectors were attached to the cable harness. The connector nuts were fastened by a nut spanner and/or a long-nose plier. (Attachment 3)
Routing of the cables / Installation of the cable ties
As mentioned above, some cables are longer than they used to be. So the routing required some creativity. The cables were attached to the cable pegs. We used Kapton sheets to distribute the cable tie's pressure to the wires and also protect the wires from the ties.
The OMC (004) and the transport fixture were so far placed in the 40m clean room.
OMC (004) + the transport fixture was transported to Downs 227 with the boxes for OMC cabling hardware and DCPD/QPD connector parts.
2/1 2:30PM~ Bonding reinforcement (Last EP30-2 gluing)
2/2 1:00PM~ Peripheral attachment / Optical testing setup
Belated entry: OMC(004) TMS measurement with the PZT voltages scanned (Jun 12/15, 2023)
Belated entry: OMC(004) Spot positions (Jun 15, 2023)
Photographs of the spot positions on the cavity mirrors and the DCPDs/QPDs as well as the reflected beams towards the beamdumps.
Work log for June 14, 2023
OMC(002) repair completed
When the cable harness of OMC(004) is going to be assembled, the cable harness of OMC(002) will be replaced with the PEEK one. Otherwise, the work has been done.
Note that there are no DCPDs installed to the unit. (Each site has two in the OMC and two more as the spares)
More photos: https://photos.app.goo.gl/XdU1NPcmaXhATMXw6
OMC #002 Optical tests
(Cabling / Wiring)
(Packing / Shipping)
We worked on the bonding of the flat mirrors for the OMC cavity with UV epoxy.
- Prepared the UV illumination setup. Cleaned up the table a bit to spare some space for the illuminator.
- Checked the output power of the illuminator. The foot pedal worked fine. The timer was set to be 10s. The UV output from the fiber was nominally 6W. This is after some warming up for ~1min. (Checked the output power continuously with the UV power meter.)
- Checked the cavity alignment / FSR / TMS - it looked good at this moment
- We confirmed that the UV epoxy has an expiration of July 3, 2023. The bond capsule was brought from Downs right before the work started, and thawed at the lab.
- The bottom of FM1 and the breadboard were cleaned. Cleaning with lens cleaning paper + IPA remained a few specks of dust on the surface. We decided to use Vectra swabs to wipe the breadboard surface. This worked pretty well.
- Applied a tap of UV epoxy to FM1 and placed it on the template. The optic was constrained by a retainer clip.
- We found that the spot positions were significantly moved. Probably FM1 was not well touching the template before. We tried to recover the previous optical axis by aligning CM1 and CM2.
- Here is the tip: align the beam on CM1 at the desired spot. Move CM1 to bring the spot on CM2 to the desired spot. CM2 is aligned to have TEM00 as much as possible.
- We recovered reasonable spots on the mirrors. Measured the FSR and TMS (vertical and horizontal) to be 264.73MHz, 58.18MHz, and 58.37MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.
- Gave UV illumination 10s x 2. Confirmed that the mirror is rigidly bonded.
- Continued to bond the other flat mirror. The same process was repeated.
- The bottom of FM2 and the breadboard were cleaned.
- Applied a tap of UV epoxy to FM2 and placed it on the template. The optic was constrained by a retainer clip.
- Measured the FSR and TMS (vertical and horizontal) to be 264.7925MHz, 58.15MHz, and 58.3725MHz, respectively. This makes the 9th-order modes well separated from TEM00. Very good.
- Continued to bond some less important mirrors.
- SM1 was placed on the template with the same step as above. BS2 (for QPD) and a dummy QPD housing were also placed just to check if the optical axis has any inconsistency. The good beam alignment on the QPD housing was confirmed.
- Applied a bond to SM1 and blasted the UV (20s)
- Applied a bond to BS2. Checked the alignment on QPD1 again. It looked good. UV illumination was applied.
- Placed BS3 to the cavity transmission. A dummy DCPD housing was placed at the reflection side of BS3. There was no inconsistency with the beam alignment.
- The UV illumination was applied (20s).
CM1: PZT ASSY #8 (M7+PZT11+C11)
CM2: PZT ASSY #11 (M14+PZT13+C13)
We continued to bond two CM mirrors and the other two steering mirrors for QPD2.
Before the bonding work, the FSR and TMSs were checked again.
FSR: 264.7925 MHz
TMS_V: 58.15125 MHz
TMS_H: 58.33375 MHz
Checked the transmission: The OMC loss was 4.3 +/- 0.2 %.
This does not make the HOMs coincidently resonant until the 18th-order (+9MHz). Looks good.
- Applied the bond to CM1 and the UV illuminated.
- Applied the bond to CM2 and the UV illuminated.
==> The cavity bonding is completed.
Removed the micrometer for CM2 to allow us to bond SM2/SM3
- Checked the spot at QPD2: The spot was a couple of mm too left. This was too much off compared to the QPD adjustment range. ==> Decided to shim the SM3 position with a piece of Al foil.
- Otherwise everything looked good. SM2/SM3 were bonded.
Invar block bonding
- There are three tubes of EP30-2 that expires on 2/22, 2023.
- A tube was almost empty. Used this tube to fill/purge the applicator. The 2nd tube was then attached to squeeze out 8g of glue mixture.
- 0.4g of fused silica beads were added to the glue mixture.
- Mixed the bond and a test piece was baked by the oven. (200F=95C, 5min preheat, bakeing 15min).
- The glue test piece was "dry" and crisp. Looked good.
- Applied the glue on the invar blocks. Confirmed that the bonding surfaces were made completely "wet".
- 4-40 screws were inserted to the blocks so that the blocks were pushed toward the template. See Attachments 3 and 4.
CM1: PZT ASSY #8 (M7+PZT11+C11)
CM2: PZT ASSY #11 (M14+PZT13+C13)
1. Flipping the OMC
It turned out that the transport fixture for this OMC could not be closed. The locks are too short, and the knobs could not be turned. We temporarily fastened the long 1/4-20 screws to secure the box and flipped it to make the top side face up.
2. Setting up the top-side template
The top side template was attached to the breadboard. We took care that the lock nuts on the positioning screws were not touched. The margins between the template and the glass edges were checked with a caliper. The long sides seemed very much parallel and symmetric, while the short sides were not symmetric. The lock nut on the short side was loosened, and the template was shifted to be symmetric w.r.t. the breadboard.
3. UV epoxy work
The cylindrical glass pieces were wiped, and the bonding surfaces were cleaned so that the visible fringes were <5 fringes. We confirmed the hooking side is properly facing up. The UV epoxy and UV curing were applied without any trouble. (Attachment 1)
4. EP30-2 bonding of the invar mounting blocks
Six invar blocks were bonded. This time the Allen key weights were properly arranged, so they didn't raise the blocks. The bond properly wetted the mating surfaces.
The final step of the bonding is to remove the template.
And replace the locks of the transport fixture.
Yesterday, we noticed that we could not close the transport fixture for OMC #4. We could not fully rotate the knobs of the locks. Today, I took the hooks from the functioning locks of the spare transport fixture.
It turned out that the default dimension of the lock seemed too tight. The functioning one has the through holes elongated by a file or something. This modification will be necessary for future transport fixtures.
The bottom side template was separated into two pieces and successfully removed from the breadboard. The template was assembled together again and bagged to store it in a cabinet.
We found that the invar block for DCPD(R) was bonded with some air gap (Attachment2 1/2).
The Allen key used as a weight was too small, which caused it to get under one of the screws used as hooks and lift the block.
We've investigated the impact of this tilt.
- Bonding strength: The bonding area is ~60% of the nominal. So this is weak, but we can reinforce the bonding with an aluminum bar.
- Misalignment of the DCPD housing: The tilt will laterally move the position of the DCPD. However, the displacement is small and it can be absorbed by the adjustment range of the DCPD housing.
- Removal: From the experience with the removal of the beam dump glass, this requires a long time of acetone soaking.
- We don't need to remove the invar block.
- Action Item: Reinforcement of the bonding
[Camille, Thejas, Koji]
We added a reinforcement bar at the back of the invar block which had the tilt issue.
The reinforcement bar was added to the backside rather than the side or front such that the DCPD housing does not interfere with the reinforcement bar.
Also, small amount of EP30-2 was added to the CM2 wire so that the repeated bend of the PZT wire cause the disconnection at the PZT.
The attached photo shows the resulting bond spread.
During the second UV epoxy session, we did not bond the input beam dump. This is because this beam dump was not the one planned from the beginning and if it was bonded in place, it would have created difficulties when removing the template.
First, we aligned a couple of Allen wrenches to define the location of the beam dump. We've checked that the main transmission is not blocked at all while the stray beam from the OMC reflection is properly dumped.
After the confirmation, the UV epoxy + UV alight were applied.
The resulting position of the beam dump is shown in the attachment.
A beam dump was stacked on the base of the previous beam dump. The angle was determined so that the main transmission goes through while the stray OMC reflection is blocked without clipping at the edge.
The resulting alignment of the beam dump is shown in Attachment 1.
The beam dump tended to slip on the base. To prevent that a couple of weights were placed around the bonding area. (Attachment 2)
Photo of the BS1 AR cleaning process
Attachment 1: Before cleaning. Foggy surface is visible.
Attachment 2: After FC cleaning. The structure of the deposited material is still quite visible.
Attachment 3: Acetone scrubbing. Cotton Q-tip was used so that the stick does not melt with acetone.
Attachment 4: After acetone scrubbing. Nicely clean!
Acetone scrubbing was applied to HR/AR of BS1, FM1, FM2, BS2, and HR of CM1 and CM2. (total 10 surfaces)
Then final FC paint was applied to these 10 surfaces.
We'll come back to the setup on Thu for FC peeling and loss measurement.
The damaged black glass was removed from the OMC breadboard leaving the glass base.
The black glass pieces were bonded very tightly on the FS base with EP30-2. The apparent amount of the bond was not so much but it was such hard that removal by hand was not possible.
We decided to give drips of Acetone on the base hoping the gradual dissolving of EP30-2. Using a knife edge, the "filets" of the bonds were removed, but the BD was still tight.
By wedging the black glass-black glass bonding with the nife edge, the left side (the directly damaged one) was taken off from the structure leaving a tiny fragment of the glass on the base.
The remaining one was even stronger. We patiently kept dripping Acetone on the base and finally, the black glass piece was knocked off and removed from the base.
Attachment 1: The base right after the black glass removal.
Attachment 2: The black glass pieces were stored in a container with Al foil + clean cloth bed. The damaged and fogged surfaces faced up.
Attachment 3: The zoom-in shot of the black glass pieces.
Attachment 4: The base was wiped with Acetone and cleaned with FC. We will bond another BD assembly on the base, presumably using the UV epoxy.
We obtained Regent grade DI water. It was poured into a smaller cup.
FC liquid was also poured into a small beaker.
Wash the mirror with a swab. We should have used a smaller swab that GariLynn has in her lab.
As soon as the mirror was wiped with the water, the FC was applied with a large brush. Don't let the water away!
Then more layer of the FC was added as usual.
The quick painting of FC made a mess around the mirrors due to excess liquid (Attachment 2). So, we decided to remove the FC remnants (on non-optic surfaces) with cotton swabs and then applied FC as usual.
This made the mess removed, however, we found the OMC loss was increased to >10%(!) (Attachment 3). We decided to continue tomorrow (Thu) with more weapons loaded consulting with GariLynn.
Another set of FC cleaning was applied to FM1/FM2/CM1/CM2 and SM2. Some FC strings are visible on SM2. So I decided to clean SM2 as well as the cavity mirrors close to SM2 (i.e. FM2 and CM2)
As a result, the bright scattering spot on CM1 is now very dim. And the loss was reduced to 4.0%. This is 0.4% better than the value before the water cleaning.
It'd be interesting to repeat the water cleaning, at least on FM1. FM1 is the closest cavity mirror to the beam dump damaged by the high-power laser pulse.
Maybe we should also clean the AR side of FM1 and BS1, as they were right next to the damaged beam dump. It is not for the loss but for reducing the scattering.
The second trial of the water scrub
A bright scatter is visible on FM1, so I tried water scrub on FM1. This time, both surfaces of FM1 and both surfaces of BS1 were cleaned.
Smaller Vectra swabs were used for the scrub. Then the water was purged by IPA splashed from a syringe. Right after that FC was applied.
This was a bit messy process as the mixture of water/IPA/FC was splattered on the breadboard.
Nevertheless, all the mess was cleaned by FC in the end.
The transmission measurements are shown in Attachment 1, and the analyzed result is shown together with the past results.
The 2nd water scrub didn't improve the transmission and it is equivalent to the one after the two times of deep cleaning.
I concluded that the water scrub didn't change the transmission much (or at all). We reached the cleaning limit.
The AL metal bracket was replaced with a PEEK version.
Attachments 1/2: Before the replacement. The photos show how the cables are arranged.
Attachment 3: How the replacement work is going. The 1/4-20 screws were super tight. Once the connectors were removed, an Allen key was inserted to a hole so that the 1/4-20 on the short sides were removed by closing Allen key arms. For the screws on the longer sides, the same technique can be applied by using three Allen keys. This time none of the screws/cable pegs were wasted. The clothes were used to protect the breadboard from any impact of the action.
Attachments 4/5: Final state.
OMC #1 repair has been 100% done
We still have 4 correct cable pegs and many 1/4-20 BHSCs for OMC #4.
The OMC #002 is ready for shipment.
Attachment 1: Work done on Sept 19, 2022
Other attachments: Putting the OMC in the pelican case.
New cable ties were installed on the cable pegs attached to the long sides of the cable bracket.
More epoxy delamination check:
DCPD R (Attachment 1): Found half delaminated
DCPD T (Attachment 2): Found half delaminated
QPD1/QPD2 (Attachment 3): Looks fine
In total we need to fix bonding of three invar bases (including the one for the cable bracket)
Measure the power ratio between the forward-propagating and reverse-propagating beams.
- To increase the incident laser power, NPRO Current ADJ was set to be 0 (increased from -50)
- 1st: Without the baffle 0.373 +/- 0.001 uW / With the baffle 0.318 +/- 0.001 uW
- 2nd: Without the baffle 0.370 +/- 0.001 uW / With the baffle 0.318 +/- 0.001 uW
- 3rd: Without the baffle 0.370 +/- 0.001 uW / With the baffle 0.317 +/- 0.001 uW
==> 53.3 +/- 0.6 nW
- The main transmission was 84.0mW
==> Backpropagation ratio was 0.634+/-0.007 ppm
- Direct measurement of the OMC was after BS 96.6mW
==> Backpropagation power from the cavity: 61.3 +/- 0.7 nW
- Cavity transmission for the matched beam is Tcav RinputBS = 0.963
==> Incident resonant TEM00 power 100.3mW
- Reflection 61.3+/-0.7 nW x RinputBS = 60.8+/-0.7 nW
-> The effective reflectivity for the mode-matched resonant TEM00 beam incident on the OMC (1st steering mirror) is 0.606+/-0.007 ppm
Jun 21: Alena and Koji worked on gluing of the CM1 mirror on the OMC breadboard #002. This is an irregular procedure. Usually, the PZT mirror subassembly is prepared before the mounting prism is glued on the breadboard. In this occasion, however, a PZT and a mirror are bonded on an existing prism because only the damaged mirror and still functional PZT were debonded from the mouting prism.
For this purpose, the mirror and the PZT were fixed on the mounting prism with the modified fixture set (D1600338). The original PZT was reused, and the new mirror #8 was used. The alignment of the mirror was checked OK using the cavity beam before any glue was applied. The arrow of the CM mirror is facing up.
We mixed 8g EP30-2 (it was almost like 3~4 pushes) and 0.4g glass sphere bond lining. Along with EP30-2 procedure, the bond was mixed in an Al pot and tested with 200degF (~93degC) preheated the oven for 15min. The cured bond showed perfect dryness and crispness. The bond was painted on the PZT and the PZT was placed on the fixture. Then more bond was painted on the other side of the PZT. The mirror was placed in the fixture. The spring-loaded front plate was fixed, and the breadboard was left for a day. (Attachment 1~3)
Jun 22: The fixture was removed without causing any visible delamination or void. The attachment 4~6 show how wet the joint is (before baking). There were some excess of EP30-2, which bonded the fixture and the mounting prism as usual. The fixture was detached by prying the front piece against the rear piece with a thin allen key. Some of the excess bond on the mounting prism was removed by scratching.
The alignment of the cavity was checked with the cavity beam and it is still fine.
More photos can be found here: Link to Google Photos Album "OMC #002 Repair - CM1 gluing"
The optical surfaces were coated with FirstContact to keep them clean / somewhat protected during the transportation.
The PD aperture was sealed with FirstContact "caps" (made by Kate in 2016?).
o Power Budget (2022/07/18)
NPRO ADJ -50 (min)
Fiber incident 62.8mW
Fiber output 45.1mW
Matching to the fiber 72%
DCPD T = 8.90 +/- 0.01 mW
REFPD = 3.760 +/- 0.001 V
DCPD R = 8.82 +/- 0.01 V
REFPD = 3.760 +/- 0.001 V
CM1 = 81.4 +/- 0.1 uW
REFPD = 3.767 +/- 0.001 V
CM2 = 86.6 +/- 0.1 uW
REFPD = 3.767 +/- 0.001 V
OFS = -6.214 +/- 0.001 mV (beam blocked)
LOCKED = 57.5 +/- 0.5 mV
REFPD = 3.970 +/- 0.003 V
UNLOCK = 2.816 +/- 0.003 V
REFPD = 3.943 +/- 0.001 V
P_Inc = 20.04 +/- 0.01 mW
REFPD = 3.946 +/- 0.001 V
- Cavity coupling 0.989 (1.1% junk&sidebands)
- Cavity R&T: R=756ppm, T=0.946
- OMC Throughput (Cavity T x First BS R): T=0.939
- Cavity loss per mirror 90 ppm / Round Trip Loss 432ppm
o Power Budget after FirstContact cleaning (2022/07/20)
NPRO ADJ -50 (min)
Fiber incident --.-mW
Fiber output --.-mW
Matching to the fiber ??%
DCPD T = 8.62 +/- 0.01 mW
REFPD = 3.549 +/- 0.001 V
DCPD R = 9.46 +/- 0.01 V
REFPD = 3.562 +/- 0.001 V
CM1 = 74.5 +/- 0.1 uW
REFPD = 3.585 +/- 0.001 V
CM2 = 81.7 +/- 0.1 uW
REFPD = 3.585 +/- 0.001 V
vOFS = -6.197 +/- 0.001 mV (beam blocked)
LOCKED = 47.6 +/- 0.2 mV
REFPD = 3.596 +/- 0.003 V
UNLOCK = 2.700 +/- 0.003 V
REFPD = 3.590 +/- 0.001 V
P_Inc = 19.36 +/- 0.001 mW
REFPD = 3.594 +/- 0.001 V
- Cavity coupling 0.980 (2.0% junk&sidebands)
- Cavity R&T: R=229ppm, T=0.970 (previous T=0.946, 2.4% UP!)
- OMC Throughput (Cavity T x First BS R): T=0.963
- Cavity loss per mirror 42.8 ppm / Round Trip Loss 238ppm
== Initial Preparation ==
== Measurements ==
== Repair / Preparation ==
== Shipping ==
Inspection of the delaminations in the optics side
Inspection of the bonding on the suspension interface side. All look good.
#1 The Invar bar on the cable bracket (DCPD side)
Added short (frosted) Al bars (Attachment 1) to the short sides of the invar bar. (Attachments 2/3). Some glue was sucked into the delamination gap by capillary action (=good) (Attachment 4)
#2 The Invar bar on the cable bracket (QPD side)
Added short (frosted) Al bars to the short sides of the invar bar. (Attachments 3/5). Maybe some glue was sucked into the delamination gap??? Not so clear. (Attachment 4)
#3 The Invar bar reinforced in 2016
Added a short (frosted) Al bars to a short side of the invar bar (Attachment 6). On both sides of the 2016 reinforcement, rectangular prisms are added (Attachment 6)
Some capillary action is visible beneath the invar bar (Attachment 7)
Leave it as it is for a day
Checked the delamination status:
The cable bracket was successfully replaced.
- The hole size extension is going forwared now.
- Madeline and Chub are cleaning (sonicating) a drill (29/64=0.4531")
- The parts in a bag were brought to the 40m C&B lab.
- The hole is going to be 11mil=0.28mm larger than the recommendation (0.442").
It's not a D-hole. The connector has a rounded-rectangular flange that fits into the PEEK parts.
So I don't think it's an issue.
- Chub has a proper spanner to fasten the nuts. We want to use it here and LLO.
Now we got the C&Bed parts to continue to work on the cable bracket replacement.
1) Helicoil insertion
1/4-20 Helicoils were inserted into the 6 thread holes of D1300052. It went mostly okay. We witnessed that the Helicoil insertion tool delaminated the plating of the Helicoils upon insertion (Attachment 1). Stephen mentioned that this is not usual, but we didn't find anything further such as increased friction, more debris, etc. So we decided to go forward.
2) EP30-2 Kit
The EP30-2 kit was transferred from the 40m clean room to the OMC lab. The EP30-2 kit tracking was updated via C1900343
3) D1300052 reinstallation -> FAIL
Now resumed to the installation of D1300052 bracket. However, the hole size of the bracket is just a bit too small compared with the size of the mighty mouse connectors. It was already quite tight with the metal version. However, this PEEK version seems to have 0.1 mm further small diameter, and then the connectors do not penetrate the holes. The plan could be
1) Use a razor blade to shave the hole inner circle.
2) Use a cleaned drill bit to make the hole size 0.2mm bigger.
- D1300052-V3 SN001 is going to be used (Attachment 1)
- This is the PEEK version of the cable bracket (Attachment 2). The side thread holes have no Helicoils inserted. This needs to be done!
Connector arrangement check / cable routing check
Attachment 3: Connector Arrangement from the Northside
Attachment 4: Connector Arrangement from the South side
Attachment 5: Cable routing (Northside down)
At this point, the delamination of the V shape beam dumps was visible. This is the subject of bonding reinforcement.
LLO has one empty OMC transportation fixture.
LHO has one empty OMC transportation fixture.
LHO has one OMC transportation fixture with 3IFO OMC in it.
LHO has the Pelican trunk for the OMC transportation. Last time it was in the lab next to the optics lab.
Attached please see my notes summarizing the models for the electrodes and inductors within the 3rd IFO EOM
Loan from ATF:
2 blue banana cables returned on Jun 4, 2013
BNC cable returned on Mar 21, 2013
TENMA triple power supply returned on July 17, 2015
4x GPIB cables returned on Mar 21, 2013
From EE shop:
red banana cables returned on Jun 4, 2013
[Rich, Dean, Koji]
Stuffed all inductors for the new LLO EOM. As the impedances were sensitive to the positions of the inductors in the housing, they were glued with a glue gun.
Also the lid of the housing significantly change the stray capacitance and lowers the resonant frequency (meaning lowers the Q too), we decided to tune the matching circuit without the lid.
The attached plots show the measured impedances. They all look well tuned and matched. We will prepare and perform the optical measurement at the 40m.
Preparation for ionized N2 blow
- 99.9998% N2 cylinder delivered (ALPHAGAZ 2 grade by AIR LIQUIDE) ALPHAGAZ 2 [PDF]
- Filter and Arcing module already in the lab
- A brass regulator to be installed (Done - March 24)
- 50 ft air line already in the lab / needs to be wiped/rinsed (Done - March 24)
- Air line and filter installed (Done - March 24)
[Koji,Philip, Liyuan, Joe]
We moved the curved mirrors to these positions:
inner = 0.807mm
outer = 0.983 mm
inner = 0.92 mm
outer = 0.85 mm
To do this so that realignment was easier, we moved the screws in steps of 5um. We alternated which mirror we adjusted so that we could monitor with a wincam how well aligned the beam into the cavity was. We only moved the cavity mirrors a small amount so we could still see higher order mode flashes transmitted through the cavity (e.g.TM03 modes). We would then improve the input alignment, and then move the cavity mirrors some more. Once the mirrors were adjusted according to http://nodus.ligo.caltech.edu:8080/OMC_Lab/190422_195450/misalignment4.pdf the spot positions looked near the middle of the curved mirrors (using a beam card). We began beam walking but we ran out of range of the bottom periscope screws in the yaw dof. We tried using the third screw to move the mirrror in both yaw and pitch, hopefully this will let move the mirror such that we can use the just the yaw screw. This screw also ran out of range, so we decided that the cavity needed a small adjustment.
The curved mirrors were moved slightly (>5um) and then we tried to get alignment. By using the fibre coupler translation stage, we move the beam side ways slightly, and then tried to get the periscope mirrors back to a position where the screws could move the mirrors. Once we had an ok alignment, we checked the beam. It looked like it was pretty close to the centre of the curved mirrors, which is where we wanted it to be.
We then tried locking the cavity, although the error signal was quite small. The adjusted the input offset and gain of the servo (there is apparently some problem to do with the input and output offsets). Once the cavity was locked we could make the final adjustments to aligning. We still ran out of range on the periscope. We decided to move the breadboard with the fibre coupler and mode matching lenses on it. Because we knew that the cavity was aligned such that the beam hits the centres of the curved mirrors, we could regain flashes quite quickly. We saw the error signal go down, but eventually this decrease was just to do with the beam clipping on the periscope mirrors. We moved the spot back to where we ok aligned, and slid the periscope so we were not clipping the mirror. This worked very well, and then optimised the alignment.
We then tried to improve the mode matching.
We took photos of the spot positions (quite near the center) and made the detuned locking measurement. The fitting of the data (attachment 1) wsa 1.1318m (what error should we put here?).
I think the order we did things in was:
I've cleared the small optical table and wondered how to move it out of the room. Fortunately, the north side of the big table had wide enough clearance and let the 36" wide table go through. This was easy without moving other heavy stuff.
From here to the door, a bit of work is required. A possibility is to roll the laser blocking wall to the south side of the big table. This will require moving the shelving in the entrance area but it's not a lot of work compared to disassembling a part of the wall.
If this does not work somehow, we will consider removing the last panel of the wall and it will definitely allow the table to get out from the door.