Sheila, Georgia

 

Picking up HAM7 work were we left it at the end of the year. 

 

We found that even though the alignment sliders for the ZMs and FC1 where back were they were before the break, the refroreflected beam was not making it back through the VIP. 

 

ZM3 OSEM input filter offsets were turned off for some reason, we turned those back on. This doesn’t explain the alignment but seemed like it should have been on. 

 

We turned on the dodgey FC ASC to add a dither to ZM3, and then aligned ZM3 to get the beam through the VIP (it was blocked by the aperture on SFI2 between the polarizer and the rotator. We aligned ZM5 and the SQZT7 periscope mirrors to get the beam onto the CLF trig diode which we’re using to monitor the IR transmisison of the the OPO, reflected off the beam diverter. And did alignment of ZM3 and ZM2. Final slider values:

 

ZM2 P: 1760

ZM2 Y: -20

ZM3 P: 1853

ZM3 Y: -966

 

 

When we went out to the floor to try and profile beams we found the beam off ZM5 was moving around and the power was fluctuating wildly. It looks like the beam leaving the VOPO towards ZM1 is stable, so we think that some combination of ZM1/ZM2/ZM3 are swinging around causing the beam to get clipped on the VIP and the power reaching ZM4/ZM5 to fluctuate. We've asked Rahul to investigate the ZM damping loops as particularly the longituinal DOF damping has a large amplitude.

 

We started checking the PZT actuation strength so we have something to compare to once we're under vacuum.

 

PZT1 driven with Thorlabs driver (cable 98)

8V pk-to-pk out of sig gen, Thorlabs PZT driver has gain of 15, 0-118V scan.
4 green resonances (all at the high voltage hald), 2 1064 resonances.

 

We tried driving PZT2 with the Thorlabs PZT driver but aren't sure that it is connected. We ran out of time to finish this task.