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

2. OUTLINE
Shadowing
SuperSaturation
Saturation
Reflections
Curiosity

3. 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

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

5. 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.

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

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

8. 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.

9. 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!

10. SuperSaturation
Supersaturation
of CCD
VERY hard to
reconstruct

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

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

13. 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

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

15. 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

16. 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

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

18. 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

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

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

21. Crosstalk Explanation and Solution
NONE

22. 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