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Transfer Line Studies. James N. Bellinger University of Wisconsin-Madison 12 December 2008. Summary. No Cocoa yet Hand fits show relative rotation among Endcap disks Can identify backwards DCOPS. Description. 6 Transfer lines at 60 degree intervals around the outside of the detector

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transfer line studies
Transfer Line Studies

James N. Bellinger

University of Wisconsin-Madison

12 December 2008

James N. Bellinger 12-December-2008Summary
  • No Cocoa yet
  • Hand fits show relative rotation among Endcap disks
  • Can identify backwards DCOPS
James N. Bellinger 12-December-2008Description
  • 6 Transfer lines at 60 degree intervals around the outside of the detector
  • 12 DCOPS on each Transfer line
    • 4 on each Endcap
    • 4 on selected MABs
  • 2 Lasers on each Transfer line
    • Call them the Plus and Minus lasers
  • 72 DCOPS in all, with 144 readings
    • Oriented so the 1/3 CCD pair measure Rφ, 2/4 pair measures radius
James N. Bellinger 12-December-2008Problems
  • A few DCOPS were unreadable
  • Sometimes LV to Barrel DCOPS was off
  • Lasers were shadowed in places: no signal
  • Laser direction not always adjustable
James N. Bellinger 12-December-2008Layout















data selection
James N. Bellinger 12-December-2008Data Selection
  • From CRAFT run
    • Select interval with field at 3.8T in which laser directions don’t drift much
    • Select interval with field off ditto
    • (CRAFT data taking was two runs: would have been a single run if the power hadn’t failed)
  • Plot the distribution of mean values subject to quality cuts
    • Background area <300000 pixel x counts
    • Signal area>0 and <500000
    • Sigma >39 pixels and < 220
    • Mean>0 pixels and < 2048
endcap only study
James N. Bellinger 12-December-2008Endcap-only study
  • For each magnetic field state
  • For each Endcap, use the laser at that end
    • For each Transfer line, use the 4 DCOPS
    • Reorient the CCD information to match DCOPS mounting
    • For each CCD, fit the means at the 4 DCOPS and find the residuals
    • Average the residuals of opposite pairs of CCDs
    • Interpret these residuals as displacements of the DCOPS and plot them
plus endcap dcops displacements
James N. Bellinger 12-December-2008Plus Endcap DCOPS displacements

Vectors plotted

to show dX

Ring diameter is

not relevant

Largest vector

has length given

in the title

Vectors at center

average of rest,

to estimate disk


minus endcap dcops displacements
James N. Bellinger 12-December-2008Minus Endcap DCOPS displacements

ME-1 and

ME-2 show

relative rotation

about .5 mrad

ME-1 and ME-2

show relative

dislocation of

about 3mm

change with field
James N. Bellinger 12-December-2008Change with field

Change in relative

displacement with

field is mostly


ME+3 and ME+2

move oppositely


The disk YE+2 bends, and the DCOPS

positions are cantilevered

change of raw beam positions
James N. Bellinger 12-December-2008Change of Raw Beam Positions



Difference between

field on and off for

Minus endcap at each

station, as a function of

position (φ) around the


ME-4 next to laser: little


ME-3: about 3mm

ME-2: about 3mm

ME-1: about 8mm



connecting across
James N. Bellinger 12-December-2008Connecting Across
  • Select data from 16-August
  • Not all profiles are usable
  • For Transfer Line 1, only connect with Up/Down CCD data (Rφ)
  • Both lasers reach across for Line 1, so I can compare their results directly
example of transfer line profiles
James N. Bellinger 12-December-2008Example of Transfer Line Profiles


CCD0 data reaches across, but

CCD1 gets blocked somewhere


dcops orientations
James N. Bellinger 12-December-2008DCOPS orientations

This one is odd:

data suggests

other direction

DCOPS directions

aren’t the same

along a line

deviations from linear fit
James N. Bellinger 12-December-2008Deviations from Linear Fit
  • 10 Stations had data for Up/Down CCDs (not always both of the pair) for both laser beams
  • Estimated laser tilt
  • Averaged CCD values if both present
  • Corrected for laser tilt if not
  • Fit for each laser and plotted the deviations from the fits
James N. Bellinger 12-December-2008Oddity


Difference is huge

at this point. If

I assume the


backwards, the

points fit very



Difference in

deviations found

using Plus and

Minus laser fits

James N. Bellinger 12-December-2008Conclusions
  • When the beam is unobstructed we can get useful information out of the system
  • Once mounting variations are understood we’ll have a better measure of the resolution of the system