Fiber matching: 43.2/56.7 = 76%
S/P-pol ratio 0.7/43.2 = 1.6%
Clean Supply Ordered
Friday, Nov 11th, 2022
Setting up OMC #1 for transmission measurements:
The laser beam was aligned to the OMC cavity. The OMC cavity was locked and the transmission measurements were recorded.
The measured total optical loss of the OMC was
1st: 0.015 +/- 0.003
2nd: 0.085 +/- 0.005
3rd: 0.0585+/- 0.0008
4th: 0.047 +/- 0.002
In avegrage the estimated loss is
Loss = 0.055 +/- 0.014
This is unchanged from the measurement at LLO after the FC cleaning
Loss = 0.053 +/- 0.010
Monday, November 14, 2022
Camille and Koji did a "deep cleaning" of OMC#1:
1) Applied First Contact to the mirror surfaces. Removed first contact after ~10 minutes.
2) Acetone scrub of the mirror surfaces with a cotton swab.
3) Applied First Contact again. Removed after ~10 minutes. We left the FC paint on for the work on Thu.
The foggy spot on the input mirror was unchanged after the first round of First Contact. But the foggy spot came off during the acetone scrub.
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.
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.
- Removed the first contact we left on Monday.
- Measured transmission (Set1) Very high loss! Total optical loss of 18.5%! Observation with the IR viewer indicated that CM1 has bright scattering. We suspencted a remnant of FC.
- Applied the second FC on the four cavity mirrors. This made the CM1 sport darker.
- Measured the transmission (Set1~Set3). We had consistent loss of 4.2~5.0%. We concluded that this is the limitation of this OMC even with the cleaning.
Conclusion on the cleaning of OMC #001
- After a couple of first contact cleaning trials and deep cleaning, the total loss was measured to be 0.045+/-0.004.
This indicated a slight improvement from the loss measured at LLO before any cleaning (0.064+/-0.004).
However, the number did not improve to the level we marked in 2013 (0.028+/-0.004).
- This loss level of 4.5% is comparable to the loss level of OMC #3, which is currently used at LHO.
Therefore, this OMC #1 is still a useful spare for the site use.
- Some notes / to-do regarding this unit:
1) The beam dump with melted black glass was removed. A new beam dump needs to be bonded on the base.
2) The connector bracket still needs to be replaced with the PEEK version.
3) The PZT of CM1 has been defunct since 2013. Combining LV and HV drivers is necessary upon use at the site. (LLO used to do it).
The four cavity mirrors in OMC #1 were each scrubbed using acetone and a cotton swab.
Then, the four mirrors were painted with First Contact (picture attached). The First Contact was allowed to dry for 20 minutes, then removed while using the top gun.
OMC Transmission measurement after the 2nd deep cleaning
The 2nd deep cleaning didn't improve the transmission. (See Attachment 2)
The measured loss was 0.044+/-0.002
Aaron took the set to Cryo lab