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Virginia Tech Update for Tracking Group, May 16, 2007





Collimator Simulation/Design:

 Last week we talked about shaping the side of the collimator opening in phi. This would not only be technically difficult to implement in GEANT, but it may also be hard to machine. After a discussion with Dave we decided that what we would actually like to know is the tolerances of the primary collimator with regards to rate and the Q2 distribution. I have outlined my thoughts on how to attack this problem below.



Plan to investigate collimator tolerances:

As a first pass I plan to eliminate the 1st and 3rd collimators, then move the global volume of the primary collimator. I'll also use the old field map (which is symmetric in all octants) and no collimator housing. That way any asymmetries octant to octant will be due to differences in the collimator, not some problem with acceptances. I will also assume that all of the individual openings are "perfect" and placed perfectly. I will look at rates and < Q2 > and < Q4 > in all 8 octants as an effect of varying the:

  • pitch/yaw - rotation of the collimator around the x (vertical axis) is yaw for the 12 o'clock and 6 o'clock octants and pitch for the 3 o'clock 9 o'clock
  • roll - rotation of collimator around z-axis
  • z translation - longitudinal shift of collimator
  • x (or y) translation - transverse shift of collimator


    		•







    Figure 1 - Definitions of rol, pitch and yaw for an asymmetric object.

    Figure 2 - Roll, pitch and yaw for the 12 o'clock and 6 o'clock octants.







    New Magnetic Field Map:
    Problems with new map:

  • had different rates with different array sizes for old map, even if they should have been big enough
  • had different rates for new map between using new code and just reading in new map
  • array values actually different with different array sizes for both maps


    • Tests of new map:

  • get same rate for whatever array size, as long as it is big enough
  • old map rate the same w/ and w/o code to read in new map
  • old map rate the same if I use new code to read it in
  • randomly chosen array values match map (for both maps)
  • seems to work in all octants
  • new code to read in new map gives same rate as just reading in new map


    • Issues that came up:

  • not using full phi range of old map (doesn't matter for elastics?)
  • not using full radial range of old map (probably important)- &int Bdl
  • there are "missing" values in the old and minitorus maps - what does code do with those values?
  • there are regions that should be excluded from the new map but aren't; what should the code do with those values?


    		•


    Figure 3 - x vs. y at bar location for all 8 octants.

    Rate
    (MHz)

    phi range

    Description

    785 +/- 5

    5:45

    what's been used

    787 +/- 5

    0:45

    still wrong, w/ mintor

    786 +/- 5

    0:50

    should be okay





    Figure 4 - My plots of x vs y for old (top) and new (bottom) maps.

    Figure 5 - Jim's plots of x vs y for old (top) and new (bottom) maps.





    Drift Chamber:



    We have constructed and are testing a full-size six plane (xuvxuv) drift chamber. Pictures are posted but no tracking results yet. We are going to adapt the HKS tracking code to use for our chambers. Work in progress.





    Figure 6 - Partially assembled chamber of the new design.

    Figure 7 - Chamber with both Al faces; you can see the vacuum window.





    Figure 8 - Card supports and cabling for new chamber design.

    Figure 9 - High voltage connectors in new chamber design.



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