This effort is still in progress - but here's a short update for the commissioning call today.

With some help from Gabriele to optimize my fitting algorithm, I've been working on some code* that imports the HWS wavefront data and determines a custom CO2 mask that minimizes the Gaussian weighted RMS wavefront distortion that is accumulated on passage through the CP+ITM substrates.

The mask will not be able to do anything to correct the high spatial frequencies associated with the point absorber, but it does mitigate a good fraction of the low and medium spatial frequencies that result from the diffusion from the point absorbers.

Conclusion: the mask looks like something we could machine. The manufacturing time on masks is about 1 week.

* code uses FMINCON in MATLAB.

To do: determine optimum diameter. Determine how accurately this would need to be aligned. Quantify overall reduction in RMS OPD. Determine the exact location of the center of the optic is the HWS coordinate system.

Images:

• Top row left: single pass measurement from HWS
• Top row middle: Thermal lens from custom CO2 mask & RH
• Top row right: total thermal lens (sum of left and middle plots)
• Bottom left: Thermal lens from RH
• Bottom middle: CO2 mask/intensity pattern

All wavefronts have a DC offset added to set the mean weighted value of optical path distortion to zero.