Plan to replace solar cell with lens + photodiode
Powerpoint with initial version of hardware design: CBP_large_lens_calibration_system.pptx
Should the focused beam fit on a photodiode?
Theoretical answer: Yes, comfortably. d = 2*w0 = M^2 * k(A, D) * lambda * f/D, where k is ideally 1.27, usually between 1.5 and 2, M is the beam quality, which should be pretty high, f=700 mm, D = 260 mm
So for lambda = 1 um, d = 5.38 um
Then the power through an aperture P(r, z = 0) = P0 (1 - exp(-2r^2/w0^2)), if want P/P0 = 0.999, then r/w0 = sqrt(-1/2 ln(.001)) = 1.86, and P/P0 = 0.0001 has r/w0 = 2.145. This beam diameter is still under 15 um, so it very easily fits within the diameter of the photodiode.
Notes from meeting on 6/9/2023 with Chris and Chuck
- biggest concern for whether the spot fits on the photodiode is chromatic aberration for a spherical lens
- build access panel/hatch instead of having a tube connector
- lens covers should be metal and they should be actuated
- whole assembly should go on the TMA, either at the top of they pylons or by the primary mirror
- should use black rubber coverings or honeycomb aluminum instead of sheet metal rings
- need to design an adapter from cylinder to rail for the lens holder (cylindrical to rectangular)
- consider using 3-4 aluminum rings to stabilize the tube
- for mounting the lens
- use 3 100 mil teflon pads as inserts
- at same location drill 1/4" through holes in radial direction
- squeeze RTV through those holes
- use CTE of glass, RTV, and aluminum to determine the appropriate size of the gap to make everything athermal
- machine aluminum clips to dimension of known gap from CTV calculation
- For the logic timer - if we need to switch out the Keithley 6514 for the 6517B we can
- check timings - see if that's a viable option
- could make new CSC if necessary - figure out if it is