1. University of Wisconsin at Madison
DCOPS Analysis
James N. Bellinger
University of Wisconsin at Madison
22-February-2007
DCOPS Data from MTCC2

2. Simple Analysis
This is not a substitute for using COCOA, which is what we intend for the final determination of position.

3. DCOPS Sensor CCD 1: RPhi CCD 2: Z CCD 4: Z CCD 3: RPhi
The Line has 10 DCOPS, with a laser at each end
CCD 2: Z
CCD 4: Z
CCD 3: RPhi

4. Piecing together lines for Z measurements
Disk bending tilts the lasers
Field-off: laser offscale one way by #8 of 10
Field-on: laser offscale other direction
By #9 the laser beam has vanished
Have to piece together incomplete lines

5. RPhi measurements
Disk bending has little effect: beam reaches far side
Field off
Field on
This is the crucial direction for momentum measurements

6. Analysis Approach
Fit the measured positions with a straight line. The resulting residuals are independent of the laser direction and show the variation from an “average position” level.
Residuals can be refit, and the resulting new residuals will be the same as the old ones. I rely on that when piecing Z- measuring lines together.

7. Field-OFF ME+2/SLM1 Z measurements
CCD2=+
CCD4=*
PG=o
ME+2
1/10
The positions are
consistent with the
shimming.
The data was taken
over several weeks.
Photogrammetry is
in good agreement

8. Field-ON ME+2/SLM1 Z measurements
CCD2=+
CCD4=*

9. Field OFF notes
The distribution of Z positions is consistent with shimming of the sensors, except for chamber ME+2/1/10 which seems a couple mm high at one end.
Absolute Z positions require Z-sensors

10. Field effect
The relative position changes when the field turns on are consistent with the predicted disk deformation of 15 mm at the center of the disk.
Both CCD measurements of Z are consistent
Measurements are stable

11. Quality notes
CCD2 profiles were somewhat shadowed in the 6’th and 7’th DCOPS, so the quality of the profiles’ fits are poorer. This shows up in the distribution of residuals, and in the RMS of the following slide.

12. Z measurement stability
Station CCD2 CCD4
CCD2 = 96 microns
CCD4 = 53 microns
Measurements were
taken over 3 weeks
Field is OFF
RMS in microns

13. Rphi residuals: Field ON
Laser 1= +
Laser 2= *
This is the direction critical for momentum measurement

14. Rphi measurement stability
Station PT1 Laser PT4 Laser TP
1/2/O
1/2/I
2/3/O
2/3/I
2/20/I
2/20/O
1/10/I
1/10/O TP
Laser 1 = 15 microns
Laser 2 = 48 microns
Measured over weeks
Field is ON, CCD1
RMS in microns

15. Rphi residuals and photogrammetry
Laser 1 OFF= +
Laser 2 OFF= *
PG = o
Agreement with photogrammetry
Laser 1 and 2 data are consistent

16. Rphi residuals Field OFF and ON
Laser 1 OFF= +
Laser 2 OFF= *
Laser 1 ON = o
Laser 2 ON = x
CCD 3 data
Shifts are noticeable
Measurements are stable

17. Change in RPhi from OFF to ON
Laser 1 = *
Laser 2 = o
The endpoints of each distribution on the previous slide were corrected to be 0 before subtracting to get these, so the endpoints have change=0 by construction.
This is a relative measure of the Rphi change when the field turns on, using CCD3

18. SLM2: Average position Z deviations
Black + photogrammetry
Red Field=0
Green Field=3.8
Blue Field=4.0
The x = CCD2
The * = CCD4
Photogrammetry matches the CCD2 better than the CCD4 averages
Fitting uses averaged positions
Oddities
PT5
PT2

19. Summary The DCOPS system works and can locate misaligned chambers
COCOA should work
Bending is consistent with predictions
The ability to adjust the laser direction would help

20. CMS Z relative positions (animated gif)
In Powerpoint the gif is animated, showing field 0, 3.8, and 4.0 data respectively

21. Auxilliary Material

22. Quality studies
Although after solving the previous two problems I had reasonable-looking results for the fits, the resolution was plagued with fliers.
Hand scanning showed which CCDs were consistently bad (and I then always excluded these) and which “events” had unusually bad profiles. This can be made automatic later. So far it looks as though the absolute signal size [available] and signal to background [not available in MTCC data] are the most useful quantities.

23. Piecing together partial lines
Fit one side’s data: 7 DCOPS worth
Fit the other side’s data: 7 DCOPS worth (there was sometimes more, but I was being conservative)
Fit the difference between the residuals of the above two fits in the overlap region.
Use this to extrapolate into the right-hand side’s data from the left and calculate residuals from this “virtual laser.”
Using the left side’s residuals and the extrapolated residuals fit this set to a line and find the residuals from that fit.

24. Scanning for both lasers on