James N. Bellinger 1-November-2007 Proposals for DCOPS James N. Bellinger 1-November-2007

OUTLINE Shadowing SuperSaturation Saturation Reflections Curiosity

Shadowing Shims are compromises, to let us laser-align with Field=0 and Field=4 Tesla B=0 B=4 Disk warping changes the DCOPS position and laser direction

Shadowing 2 B=0 CCD 1 shadowed CCD 3 shadowed B=4 Laser Laser ME+2 example

Shadowing Question What happens if we straighten out an SLM? Shadows due to Z-shims go away? Serious shadowing when field is different. Likely won’t be able to reconstruct. Lose comparison to photogrammetry.

What We See Lasers . . . . . . No info at CCD1 when shimmed Animation: compares Compromise to Straight shims. ME+2/SLM1 Laser at PT1

On another SLM Lasers . . . . . . Animation: compares Compromise to Straight shims. No info at CCD1 when shimmed ME+2/SLM3 Laser at PT 3

Straightening the SLM Z reduces RPhi shadowing with the field off Tentative Conclusion Straightening the SLM Z reduces RPhi shadowing with the field off SO . . . Straightening the SLM Z for field on should reduce RPhi shadowing when the field is on.

Shadowing Partial Solution Z-shadowing due to chamber misalignment No solution RPhi-shadowing due to Z-sensors Create/install Z-shims to make line straight at B=4 Realign lasers with field on!

SuperSaturation Supersaturation of CCD VERY hard to reconstruct

SuperSaturation Solution Dr. Eartly is replacing filters for the afflicted CCDs

Saturation Saturation of CCD Fit is degraded at best, lost at worst

Saturation Solution None at this time. Replacing filters is time-consuming: reserve effort for critical problems. Software change may help: Use raw instead of background-subtracted profiles and use auxiliary fit if saturation found

Reflections Reflections sometimes interfere with the signal Sometimes they don’t This reflection bounces off an exposed leg of a downstream CCD

Where do reflections come from? Shiny components back-reflect Shiny wall Exposed tip of filter Shiny notch in orange posts? Light going under CCD mount, reflecting off frame

How do we fix reflections? Shiny components back-reflect Stuff black paper under CCD Shiny wall Scribble w/ black paint pen Exposed tip of filter ?Not sure? Shiny notch in orange posts? Scribble w/ black paint pen Light going under CCD mount, reflecting off frame Stuff black paper under CCD

Paint pen Scribbling on the Al box reflector resulted in >6x and 3x reduction

Reflection Solutions Opportunistic fixes: When DCOPS come off Stuff a fold of black paper under each CCD, tape in place Paint the reflective sides inside the DCOPS with a pen (Marker does not work) Paint the orange post notch as appropriate

Curiosity We have crosstalk! A peak in one CCD matches a dip in others Laser head misalignment splits the beam

Crosstalk Hurts Very small signals can be shifted from their true values May not matter if we never use small signals

Crosstalk Explanation and Solution NONE

Summary of Proposals Create new shims to make SLM lines straight at B=4 Replacing filters in supersaturated sensors is being done now. Deal w/ saturated sensors in software Opportunistically fix DCOPS Insert black paper under CCDs Paint reflective inside surfaces