A couple of comments:
When we've got the optics off the bench we should route the new BNC cables and install all the patch bays. It's better to work above the bench when the optics aren't there.
2) As you say, one of the input mirrors cannot be housed in the original box. We will need to box this mirror in separately. Probably it is just a small box that we will add on to the side of the existing one. We can put something simple together ourselves to begin with.
8) We had already decided that it is unnecessary to do cylindrical mode matching. Back last summer Jenna worked on this for a while and the difference in contrast defect is very small.
One of the main priorities will be to get a beam locked in the new cavity with the vacuum pumped down. As we were discussing the other day, the alignment may shift when we pump and this is something that we're going to want to know about as soon as possible. Since we don't have our own pump, we won't easily be able to keep going up to air and back down.
The computer system has to be a reasonably high priority I think. It needs to be working stably and may take some time to fix.
The moment that we have got the parts roughly laid out on the table we should look to see if there is any machining work that needs done. We should check if there are any critical optics (injection and output) where we would benefit from having stiffer mounts. As we know from experience any parts that need made will have a lead time associated with them.
I like the idea of keeping all our electronics in the NIM crate. We should think what other stuff we're going to need. I would suggest we'll need a differential to single ended board, the new servo boards (which should include switching for the boost stages so we can control them from the computer), notch filters for the PZT input on the laser (we have one active twin T at the moment on a prototyping board). Anything else we're likely to need? We were floating the idea of making up a generic filter/amplifier board that we can later stuff for any job needed. I think I have a lot of the Altium parts for this already.
Lastly I would suggest we should think whether there are any new parts we'd like ordered - again this is just because of the lead time.
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Here is a rough plan for how I imagine the gyro upgrade should work. Anyone is invited to change things as they see fit.
- Dismantle current setup, inventory parts and store them in an organized way
- Inventory space on the table and decide the basic layout for the Enhanced Gyro
- As we are planning to house the input/REFL optics (and the laser) in the current gyro box, we will have to choose the layout pretty carefully from the start
- We need to think of a way to house the final steering mirrors into the vacuum system. One will be in the input optics box, but one will not. This can contribute noise.
- Begin vacuum system setup
- Clean parts
- Install
- In parallel with (3), begin input optics setup:
- Mount laser
- Install/align input polarization optics
- Install/align/configure EOM
- Do initial RFAM minimization
- Install CW/CCW beam separation polarizing optics
- Install/align CW AOM double-pass setup
- Maximize double-passed 1st order output beam power
- Full CW/CCW beam profiling
- Finalize IO layout to have accurate distances for modematching
- Full cylindrical modematching solution for CW/CCW
- Find optimal solution, consider beam widths at faraday isolators
- Order lenses
- Install injection/REFL isolation optics and optoelectronics
- Faraday isolators
- Waveplates
- Steering mirrors
- Focusing lenses
- Attenuators
- Gyro RFPDs
- If (8.2) lead time is high, work out quick, temporary spherical solution for locking in the meantime
- Install cavity optics
- Mount into chamber
- Steer in input beams
- Align cavity eigenmode by eye
- RF distribution
- Install dedicated LO crystal
- Install necessary splitters, couplers and distribute to:
- EOM resonant circuit input
- CW/CCW PDH mixers
- Connect AOM VCO through amplifier to AOM
- Optimize signals
- Sweep laser, adjust CCW demod phase for optimal error signal
- Tweak cavity alignment and maximize transmission
- Lock CCW
- Sweep AOM and adjust CW demod phase for optimal error signal
- Adjust injection alignment to maximize transmission
- Iterate above as necessary
- Pump down
- Reoptimize injection alignment (CW & CCW)
- Build transmission demod and PLL...
- To be continued...
A few things have been somewhat glossed over in the above:
- I still have to finish making the resonant circuit for the EOM. I have borrowed the RF transformer kit from the 40m and I will hopefully have this done before we need it
- We haven't ordered a dedicated oscillator for the LO. I guess we will get one of the Wenzel crystals and a power amp(?). This isn't extremely time-sensitive as we can use one of the RF FGs for the moment as we have been
- I am working on designing the new PDH boxes for the gyro in Altium. I am guessing these won't be completely done (i.e. received, stuffed, etc.) by the time we first want to lock the eGYRO, but we can use the old boxes until they are.
- Alastair has finished the RFPD design, and we are pretty much ready to pull the trigger on getting the boards in. We still need to make certain that the board will be compatible with whatever box we use as it is designed. I understand that the turnaround for the PCBs is pretty short, so we can proceed with the stuffing and testing while we await the boxes.
- Not sure about what to do with CDS. Rana is inclined to get an NDS2 server set up for the ATF, so I guess we will have to talk to John Zweizig about that. I understand that there are also plenty of other problems with the computers at the moment, though (e.g. the permissions thing). These need to be sorted out!!
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