We have completed all HAM7 close out tasks as in E2600157. Only thing left is that we may repeat 88609 backscatter tests tomorrow before SEI closeout tasks. Rahul and Ryan C completed SUS closeout measurements 91500.
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Out of OPO (before A:DC1): 1.304mW with standard deviation 0.4uW
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On SQZT7 HD path: 1.215mW std 0.5uW
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Out of OPO: 1.284mW std 65 uW
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On SQZT7 HD path: 1.215mW std 0.5uW
This is a loss of: 7.8%, 5.4%, 5.4%. We expect 4% but have been measuring up to 8% 91444 so are happy with this and will revisit in a future vent with different equipment. It is hard to look for 1% loss when our method gives us 1-2% variation.
Yesterday morning we spent time searching for losses, we later realized the ~2% loss we were chasing was caused by at temporary iris we had set at the beam at ZM3, next time we should use a larger 2" iris. Here is our results.
We checked the sliders of ZM2 and ZM3 by in turn putting a +/-10urad wobble on each and adjusting the sliders to be in the middle of the slider values where we started clipping: This gave us a repeatable 0.3% power improvement on the SQZT7 IR PD for <5urad slider changes.
In HAM7, as our main extra loss location is SFI1, we wanted to see if we could reduce this, before committing to moving A:M1 or A:M2,we tried moving ZM1 in yaw with the power meter on a crane after the SFI1 second pass (between SFI1 and B:M1). We found that the power was repeatably higher with ZM1 with -150urad in yaw, so sliders at (P 800, Y -240). Data attached.
Method of using Thorlabs power meter: We added the Thorlabs VRC2D1 IR pinhole aperture to the front of the power meter, moved power to maximize power though the pinhole and then removed pinhole and measure power.
We then put the power meter after the first pass of SFI1, between SFI1 and A:L2. We moved A:M1, starting with the thumb knob at 2pm, our clockwise edge of where we started clipping was clockwise 200deg to 9o'clock. The Anti clockwise edge was 360deg from starting location to 2 o'clock. So we are not 100% centered but not very near the edge. We could not see any repeatable power changes by moving a quarter turn of the knob. Data attached. We put A:M1 back to starting location.
This makes sense as on the first pass through SFI1 we could not improve the loss with alignment but on the second pass we could as the beam was double passes the iris that was causing clipping.
