Randy moved the 3IFO ISS PD array (S1202968) crate from MY storage to the OSB yesterday (WP). I opened the crate, moved the transport/storage container to the vacuum lab and optics lab to inspect. It was in a good shape except that some upgrade parts weren't there. Since I'm already forgetting what happened to other units, here's the summary.
First about parts.
- 3 of 4 units require replacement of the new PD array plate (D1300322), but we (are supposed to) have parts. I'm not sure which units were meant to be ready for installation, but if we replace the PD array plate, realignment must be done.
- None had the QPD tilt but we have enough parts for this.
- 1 of 4 units had the low QPD, i.e. QPD plane is much closer to the PSL than array PDs. No parts were located for this, and mostly for this reason we'll have to live with just two spares for 3 instruments instead of 1 spare per each instrument.
- Blue glass beam dump plates were only found for two units. The remaining two don't have these. This might be OK, the optics are easy to transplant when we pull the in-chamber unit.
Next, the summary per unit.
- Good spare S1202965 already has all upgrades. It's the only one with an updated PD array plate already installed upon initial inspection. Also see alog 83077.
- Second apare S1202966 will be OK (PD array plate will be replaced, QPD will be tilted, will use parts from the damaged unit of parts from the damaged unit S1202967 for some other things) except that blue glass beam dump optics aren't found. Also see alog 85019.
- 3IFO S1202968 will be OK (PD array plate will be replaced, QPD will be tilted).
- Damaged spare S1202967 cannot be restored in short order as that would mean locating or making/procuring new parts to make QPD higher (because the dirty parts from this unit will be reused for the second spare), C&B all new and existing metal parts, cleaning and reinstalling all optics, inspecting the surface of all 8 PDs to find particulates AND realigning the entire unit, which will be extremely time and labor intensive. Because of this, we'll only have 2 spares for three IFOs (H1, L1 and 3IFO) at least for now. Also see 82731.
Here's the thing about the PD array plate D1300322 (see attached). The updated version has a wider 100deg conical bore for larger beam clearance because it was found at some point (ECR E1400231) that the clearance was too small for the original bore and the reflection of some PDs will hit the bore wall at an glazing angle instead of hitting the beam dump. It's also easy to imagine that if you fiddle with the alignment for the production unit in chamber, INPUT light on some PDs will hit the bore wall first before hitting the PD surface.
We have the blue glass beam dumps for the S1202966 unit, they just need cleaned - location is sitting on top of the unit in the Optics lab.
I have found a bag with a label "Dirty Assy - not in ISC - single parts w/ s/n's in ICS". Inside the bag was an assembly that is a combination of upgrades and obsolete parts.
- Base plate (D1300323)
- A plate BS and two plate mirrors for the array (D1000957-V2 as a kit) and related parts
- Two blue glass beam dumps
- PD array elevator assy (D1400140)
- 50:50 BS (D1002114-V1)
- PROBABLY ATF 99:1 sampler (but it could be a high reflector of the same size as we have such high reflectors made by ATF in one of the boxes of ISS array spare parts, though I don't know why).
- Elevator post D1400143
- Upgrade to elevate the QPD position
- A kit of posts (D1300718-V3-1 SN 003 and 005, D1300718-V3-2 SN 003, 2pc D1300718-V3-3 SN 003 and 008)
- QPD mounting plate (D1300719-V2 SN 002)
- QPD assembly including QPD itself (most likely Q3000) but w/o tilt mechanism
- Obsolete PD array plate D1300322-V1
- Old experiment? 2pc of 3mm PD, most likely Excelitas C30665GH.
- This is different from all production units that are supposed to use 2mm Excelitas C30642GH, but these two diodes share the same outer dimensions and pin-compatible.
I'm going to send the upgrade parts to elevate the QPD position to C/B. In addition, I went through all of the boxes we know are somehow related to ISS 2nd loop (again) and found some unused blue glasses. This means that we have enough parts to produce 3 spares if we have to (though it would be a lot of work).
Here's the inventory list of the 2nd loop spare parts as of now: https://dcc.ligo.org/LIGO-E2500191
