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

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

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

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

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

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.

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

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

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

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

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.

Z measurement stability Station CCD2 CCD4 0 92 51 1 78 52 2 30 35 3 41 26 4 88 65 5 28 126 6 261 104 7 44 11 8 140 26 9 155 31 CCD2 = 96 microns CCD4 = 53 microns Measurements were taken over 3 weeks Field is OFF RMS in microns

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

Rphi measurement stability Station PT1 Laser PT4 Laser TP1 10 40 1/2/O 10 106 1/2/I 5 49 2/3/O 11 49 2/3/I 12 32 2/20/I 19 22 2/20/O 13 113 1/10/I 22 22 1/10/O - 20 TP4 33 26 Laser 1 = 15 microns Laser 2 = 48 microns Measured over weeks Field is ON, CCD1 RMS in microns

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

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

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

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

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

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

Auxilliary Material

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.

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.

Scanning for both lasers on