Primary Collimator Live Page
Katherine's Status Report
Tony's Status Report
Klaus's Status Report
Michael's Web Page
Burnham's Web Page
Burnham's collimator pics
Keep Out Zones a la Allena
Previous Reports
The following pages require a username and password:
Qweak elog at JLab
Qweak Simulation Forum
Virginia Tech Update for Tracking Group,
.bash
include/bfield.inc
gufld.F
uginit.F
You can download the gzipped new map from the document database:
new map
For comparisons:
.euclid
gukine.F
old gufld.F
Collimator simulation/design:
So now I have a version of the code that will switch between field maps using the MAGF flag in the .bash script. There is a hard-coded check that the read-in R, z and &phi are within the ranges of the declared arrays. I plan to make that check more fool proof but for now the necessary new scripts have links to the left. The "old range" for the old map refers to the fact that the array was not large enough to contain all of the B field values in the map. This causes a technical problem where there are field values placed in random places in memory, but also that we were not using the full range of available map values, and in fact it was not symmetric in &phi in a given octant.
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Figure 1 - x vs. y for the old field map, BFIL = 1.00 (old ranges). |
Figure 2 - x vs. y for the old field map, BFIL = 1.00. |
Figure 3 - x vs. y for the new field map, BFIL = 1.00. |
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Figure 4 - x vs. y for the old field map, VT row 20 collimator, BFIL = 1.00. |
Figure 5 - x vs. y for the old field map, 25cm up collimator, BFIL = 1.00. |
Figure 6 - x vs. y for the old field map, 25cm up collimator, BFIL = 1.00, Katherine's sides in phi. |
From these results I think we need to change the radius but not necessarily the BFIL factor. It seems that by changing the inner radius of the bar we can get back to the same error on Qweak, though tolerances, etc. may not be the same. Also it looks like the "wings" are barely fitting on the ends of the bar with the 25cm upstream collimator. This will affect our tolerances as well.
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Table 1 - Compare old results with new field map results. A bit of history... |
Figure 7 - Compare Q2 distributions with old/1.00 (black) and new/1.00 (red) maps. |
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Figure 8 - Inelastic % vs. lower x for different BFIL (new map) and BFIL =1.00 (old map) |
Figure 9 - Error on Qweak vs. lower x for different BFIL (new map) and BFIL =1.00 (old map). |
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Figure 10 - < Q2 > vs. lower x for different BFIL (new map) and BFIL =1.00 (old map) |
Figure 11 - Rate vs. lower x for different BFIL (new map) and BFIL =1.00 (old map). |
The inelastic percentages are roughly the same because the relative separation between the drooping part of the inelastic profile and the elastic profile are roughly the same. It could have been better or worse for the new map depending on the optics of the magnet, but it seems like we may be okay.
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Figure 12 - Elastic (blue) and inelastic (red) profiles with |
Figure 13 - Elastic (blue) and inelastic (red) profiles with |
Figure 14 - Elastic (blue) and inelastic (red) profiles with |
Summary of collimator tolerances discussion:
Dave made a draft of the collimator tolerances which prompted a great deal of discussion. Part of that discussion included recognizing that while our tolerances can be eased a little because we will average over 8 octants, that doesn't mean that knowing < Q2 > is trivial. Fortunately the tolerances in Jim's table seem looser than Dave anticipated.
Out of the discussion there are several issues that have come up:
collimator tilt - Juliette will be working on this
radii at the corners - not sure how to handle this in GEANT but may be possible
moving region II chambers upstream for 3rd collimator - Juliette
add non-defining lead wall, mv minitorus, etc., thinner "collimator" - ??
Dave suggests incorporating a safety factor by dividing the tolerances from Jim's table by 2 or more to keep within tolerances.
From Jim's Report:
Dave's original draft:
DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**DRAFT**
DEFINING COLLIMATOR CONSTRUCTION, ALIGNMENT, CMM SURVEY TOLERANCES 5/25/07
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DEFINING COLLIMATOR
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OCTANT HOLE CONSTRUCTION TOLERANCES (SET BY SENSITIVITES): +-0.15MM,
OCTANT HOLE RADIAL POSITIONING, WHETHER BY CONSTRUCTION OR ALIGNMENT (SET BY SENSITIVITIES): +-0.15MM
REFERENCE FACE FLATNESS CONSTRUCTION TOLERANCE (SET BY Q^2): +-1MM,
ALIGNMENT OF OCTANT HOLE MIDLINE WITH AXIS OF PHI SYMMETRY (SET BY SIZE OF BARS): +-0.5MM
MISCELLANEOUS
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COLD TARGET CENTER TO COLLIMATOR DISTANCE SURVEY REQUIREMENT (SET BY Q^2): +-3 MM
(I HAVE ASSUMED THE AS-BUILT OCTANT HOLE DIMENSIONS AND THEIR RADIAL POSITIONS WILL BE
MEASURED BY CMM, COORDINATE MEASURING MACHINE, TO MUCH HIGHER PRECISION THAN THE CONSTRUCTION
TOLERANCES.)
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The alignment tolerances can be found in Jim's talks.
