[Koji, Jordan, Stephen]
The beam dumps, bonded on Fri 06 Dec 2019, were placed in the newly tuned and configured small dirty ABO at the Bake Lab on Fri 13 Dec 2019.
Images are shared and references are linked below
Bonding log entry - https://nodus.ligo.caltech.edu:8081/OMC_Lab/386
Bake ticket - https://services.ligo-wa.caltech.edu/clean_and_bake/request/992/
OMC Beam Dump - https://dcc.ligo.org/LIGO-D1201285
The beamdumps were taken out from the oven and packed in bags.
The bottom of the V are completely "wet" for 17 BDs among 20 (Attachment 1/2).
3 BDs showed insufficient glue or delamination although there is no sign of lack of rigidity. They were separated from the others in the pack.
Item lending as per Ian's request: Particle Counter from OMC Lab to QIL
The particle counter came back to the OMC lab on Aug 10, 2020
Check-in to the OMC lab to see the status. Nothing seemed changed. No bug. The HEPA is running normal. The particle level was 0.
Went into the HEPA enclosure and put a cover on the OMC. Because of the gluing template, the lid could not be close completely (that's expected and fine).
The IPA vector cloth bag was not dry yet but seemed expired (some smell). There is no stock left -> 5 bags to be ordered.
are there any measurements of the BRDF of these things? I'm curious how much light is backscattered into the incoming beam and how much goes out into the world.
Maybe we can take some camera images of the cleaned ones or send 1-2 samples to Josh. No urgency, just curiosity.
I saw that ANU and also some labs in India use this kind of blue/green glass for beam dumps. I don't know much about it, but I am curious about its micro-roughness and how it compares to our usual black glass. For the BRDF, I think the roughnesss matters more for the blackness than the absorption.
According to the past backscatter test of the OMC (and the black glass beamdump: not V type but triangular type on a hexagonal-mount), the upper limit of the back reflection was 0.13ppm. https://nodus.ligo.caltech.edu:8081/OMC_Lab/209
I don't have a BRDF measurement. We can send a few black glass pieces to Josh.
To spare some room on the optical table, I wanted to mount the two TFT monitor units on the HEPA enclosure frame.
I found some Bosch Rexroth parts (# 3842539840) in the lab, so the bracket was taken for the mount. This swivel head works very well. It's rigid and still the angle is adjustable.
BTW, this TFT display (Triplett HDCM2) is also very nice. It has HDMI/VGA/Video/BNC inputs (wow perfect) and the LCD is Full-HD LED TFT.
The only issue is that one unit (I have two) shows the image horizontally flipped. I believe that I used the unit with out this problem before, I'm asking the company how to fix this.
The image flipping of the display unit was fixed. The vendor told me how to fix it.
- Open the chassis by the four screws at the side.
- Look at the pass-through PCB board between the mother and display boards.
- Disconnect the flat flex cables from the pass-through PCB (both sides) and reconnect them (i.e. reseat the cables)
That's it and it actually fixed the image flipping issue.
See this entry: https://nodus.ligo.caltech.edu:8081/40m/15642
Thorlabs' powermeter controler + S401C head was lent from OMC Lab. Returned to OMC Jul 15, 2022 KA
I helped to complete the 5th OMC Transport Fixture. It was built at the 40m clean room and brought to the OMC lab. The fixture hardware (~screws) were also brought there.
FEMTO DLPCA200 low noise preamp (brand new)
Keithley Source Meter 2450 (brand new) => Returned 11/23/2020
were brought to the OMC lab for temporary use.
OMC Unit 4 Build Machined Parts are currently located in Stephen's office. See image of large blue box from office, below.
Loaned item D1100855-V1-00-OMC08Q004 to Don Griffith for work in semi-clean HDS assy.
This includes mass mounting brackets, cable brackets, balance masses, etc. For full inventory, refer to ICS load Bake-9527 (mixed polymers) and Bake-9495 (mixed metals).
Inventory includes all items except cables. Plasma sprayed components with slight chipping were deemed acceptable for Unit 4 use. Cable components (including flex circuit) are ready to advance to fabrication, with a bit more planning and ID of appropriate wiring.
Item loan: SRS LCR meter SRS720 borrowed from Downs. The unit is at the 40m right now for testing with an excelitas PD. Once it is done, the setup will be moved to the OMC lab for testing the high QE PDs
Attachment 1: System diagram. The reverse bias voltage is controlled by DS335. This can produce a voltage offset up to 10V. A G=+2 opamp circuit was inserted so that a bias of up to +15V can be produced. The capacitances of the photodiodes were measured with SR720 LCR meter with a probe. DS335 and SR720 were controlled from PC/Mac via serial connections.
Attachment 2: Overview
Attachment 3: How was the probe attached to the photodiode under the test
Attachment 4: The bias circuitry and the power supply
Attachment 5: G=+2 amp
The capacitance at no bias was 460~500pF. This goes down to below 300pF at 1.0~1.5V reverse bias. At maximum +15V, the capacitance goes down to 200~220pF.
On this opportunity, the capacitances of a couple of Excelitas C30665 photodiodes were measured. In Attachment 2, the result was compared with one of the results from the high QE PDs. In general the capacitance of C30665 is lower than the one from the high QE PDs.
More explicit insights into the inventory for the Unit 4 build. Image of inventory included below.
ref: E1900034 and other associated documents.
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.
The table width was an inch too large compared to the door width. We need to tilt the table and it seemed too much for us. Let's ask the transportation for handling.
Photo courtesy by Juan
- The lab is chilly (18degC)
- Cleaned the lab and the optical table a bit so that the delicate work can be done. The diode test rig (borrowed from Downs - see OMC ELOG 408 and OMC ELOG 409) was removed from the table and brought to the office (to return on Monday)
- The rack electronics were energized.
- The OMC mirrors in use were returned to the cases and stored in the plastic box.
- The optical table was also cleaned. Removed the old Al foils. The table was wiped with IPA
- The OMC #4 was moved to the other part of the table, and then OMC #2 was placed in the nominal place (Attachment 1). Note that the "legs" were migrated from #4 to #2. There are three poles that defines the location of the OMC Transportation
- The lid was removed and the OMC was inspected (Attachment 2). Immediately found some more delamination of the epoxy beneath the cable bracket (Attachment 3). This needs to be taken care of before shipment.
- The cavity was already flashing as usual, and a bit of alignment made the TEM00 flashing.
- The locking was a little tricky because the LB unit seemed to have a gain-dependent offset. After some adjustment, robust locks were achieved. The cavity was then finely adjusted. Attachment 4 shows the CCD image of the reflection. The core of the spot is more or less axisymmetric as usual. There is also a large helo around the spot. I was not aware of this before. I may need to wipe some of the mirrors of the input path.
- As the satisfactory lock was achieved, I called a day by taking a picture of the table (Attachment 5).
== Initial Preparation ==
== Measurements ==
== Repair / Preparation ==
== Shipping ==
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
Bond reinforcement blocks for the invar brackets:
The backscatter beam is supposed to appear in the backpropagation path. The transmission of the OMC has a couple of optics, it's not easy to access that beam.
To try to deflect the beam either horizontally or vertically, small optical pieces were made. (Attachment)
These are the combination of the optics
- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs 1/2"sq BB Dielectric Mirror BBSQ05-E03
- Thorlabs PF05-03 Fused Silica Mirror Blank (dia12.7mm x t 6.0mm) + Thorlabs ME05-G01 Protected Al Mirror (dia12.7mm x t 3.2mm) + Thorlabs MRA10-K13 Right-Angle Prism Nd:YAG 10mm
Torr seal was used as the bonding epoxy. It uses a 1:2 volume mixture (not easy because of the viscosity) and is relatively fast to cure (in a couple of hours).
The test piece showed some softness after 3~4 hours so I left the parts cured overnight at room temp (i.e. 18degC)
The profile of the beam incident on the fiber input
The fiber input was deflected by a 45deg mirror. The beam profile was measured with WincamD. The beam was too strong (~60mW) even at the smallest pump power (ADJ -50) of the NPRO. So the two ND20 filters were added to the lens right before the 45 deg mirror and the camera.
The measured profile had some deviation from the nice TEM00 particularly around the waist. This could be a problem of the too small beam on the ND filter and the CCD.
This is not an issue as we just want to know the approximate shape of the beam.
For the fiber coupling, if we have the beam waist radius of ~200um it is sufficient for decent coupling.
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
SRS LCR meter SRS720 was returned to Downs as before.
OMC Reinforcement blocks
1. P/N D1600316; Version v4; Type 01; Qty 30; Source Chemistry Machine Shop
2. P/N D1600316; Version v4; Type 02; Qty 15; Source Chemistry Machine Shop
3. P/N D1600316; Version v4; Type 01; Qty 40; Source Resource MFG PO S422806
4. P/N D1600316; Version v4; Type 02; Qty 40; Source Resource MFG PO S422806
Stephen asked Srinath for the ICS entry.
Stephen made the C&B request https://cleanandbake.ligo.caltech.edu/clean_and_bake/request/1708/
Madeline was asked to take care of the C&B.
Also, the Torr Seal box was returned to Madeline.
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)
- Installed the High QE PDs to OMC #002
Upon the installation, the legs of the PDs were cut by 3mm. Also, the tab of the PD could not be embedded in the DCPD housing. Therefore, the tabs were cut.
The alignment looked just fine. The weak reflections are directed to the black glass beam dumps.
- After the installation, the QEs were measured.
It is so confusing. So I decided to make the QE test setup.
Ophir RM9 with chopper (+/-5%): 8.97mW
Thorlabs S140C integrating sphere (+/-7%): 9.11mW
Thorlabs S130C PD power meter (+/-7%): 9.15mW
Thorlabs S401C thermal power meter (+/-3%): 8.90mW
So there looks ~3% discrepancy between S130C and S401C
Then tried to measure the QE of C1-03@Cage B3 with Ophir RM9
- Initial state: QE=0.95
- First FirstContact application: QE went up to 0.973
- Second FirstContact application: QE = 0.974, basically no change
- Calibrate the trans-impedance amp with Keithley
- Apply FC to B1-22 and B1-23 to see if there is an improvement
- The power should be measured with S401C because the accuracy seems better (+/-3%).
- Take photos of the PD FC process
General To Do:
- Backscatter test 2nd trial
- Start applying the first contact to the optical surfaces
- Beam dump cleaning
- Apply FC cap to the PDs
- Delamination repair (light side)
- Delamination repair (dark side)
- Cable bracket replace (dark side)
- 4 CLASS A wire clamp obtained from the OMC spare
- 4 more DIRTY wire clamp obtained from WB experiments (they no longer use these)
Once the later ones are C&Bed, we have enough.
- DLPCA-200 trans-impedance amplifier was calibrated.
Keithley source meter 2450 was connected to the amp. Provide current and read the output voltage with the precision digital voltage meter (Agilent/Keysight).
Gain: 999.7V/A@7mA, 999.6V/A@8mA
- From the power meter spec, Thorlabs S401C seemed the best (+/-3%). So the QEs of the 9 PDs were checked with this power meter again.
- All PDs exhibited the QE of 0.95~0.96. It's all relative as the power meter has a systematic error.
- Tried to clean B1-22 and B1-23 PDs. They didn't show significant improvement after the cleaning. To avoid the unnecessary risk of damaging the PDs, further cleaning was not performed. (Some photos were attached)
- What we can do is use this result as the relative measurements.
- For OMC#2, B1-22 is the DCPD(T) and B1-23 is the DCPD(R). C1-03 and C1-12 are the spares, according to this latest result.
- At LLO, we track down the source of the throughput reduction (-10%). The QEs of the PDs are going to be tested in the same setup at once to compare their PDs and our PDs.
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?).
- 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.
- (Attachment 1) The connector nut rings were removed using an angled needle nose plier. The connector shell has a tight dimension relative to the hole on the bracket. But of course, they could be extracted.
- The 4 screws mounting the bracket to the invar blocks were successfully removed. No extra damage to the bonding.
- (Attachment 2) The plan was to remove the cable pegs by unfastening the button head 1/4-20 screws from the bracket and then just replace the bracket with the new one. However, these screws were really tight. The two were successfully removed without cutting the PEEK cable ties. Two cable ties were necessary to be cut to detach the bracket+pegs from the fragile OMC. Then one screw was removed. However, the final one could not be unfastened. This is not a problem as we are not going to recycle the metal cable bracket... as long as we have spare parts for the new bracket.
- (Attachment 3) Right now, the new bracket is waiting for the helicoils to be inserted. So the OMC lid was closed with the cables piled up. Just be careful when the lid is open.
Checking the spare parts
- Conclusion for OMC#2: need PEEK cable ties
- for more OMCs: need more BHCS / PEEK cable ties / Helicoils
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.
- 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.
The cable bracket was successfully replaced.
New cable ties were installed on the cable pegs attached to the long sides of the cable bracket.
Checked the delamination status:
#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
Inspection of the bonding on the suspension interface side. All look good.
Inspection of the delaminations in the optics side
EP30-2 bonding setup