Review of Tracker Geometry
• Overall view
• Recent bug fixes
• “Passive” tracker
–
–
–
–
– Offset
– Wrong Converter
• Typical tray
• “Active” tracker
– Vertical dimensions
• Groupings
• Radiation Lengths
– Horizontal dimensions
June 11, 2003
TKR Geometry Review
Closeout
Walls
MCM
Other
•
•
•
•
•
Cables
Heat Straps
Flexures
Bosses
???
1
Overview
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Zoom In
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More Zoom
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Comparison of Previous & (Mostly) Corrected
Geometry
Previous
June 11, 2003
New, 1st Draft
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Detail
Previous
June 11, 2003
New, 1st Draft
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Wrong Converter
• A one point, the material for the SuperGlast
converter was changed from pure tungsten to a
tungsten alloy.
• Since the alloy is less dense, the thickness of the
converter had to be increased to yield the same
radiation length.
• This was done, but the material was left as pure
tungsten.
• Fixed now…
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Vertical Dimensions of Stack (mm)
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Horizontal Dimensions
• Nothing has changed since the last iteration.
• In the last design, the top and bottom ladders on a
tray were translated in opposite directions along
their length so that they were out of register by
about 1.5 mm.
– This was never modeled in the geometry.
– BJ says this “feature” has been eliminated from the
current version.
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Side View of a Typical Tray in a Tower
Boss, closeout and
spacer are not part of
geometry model
Not to Scale!!
“Boss”
Ladders
Wall
Closeout
Silicon
Glue
dc = 27.92 mm*
Bias Board
Tray
*Top, Bottom, larger
D
Tungsten
Face Sheet
Core
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d = 2.05 – 2.1 mm
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Spacer
post
10
Details of Top Face of Trays
(all trays the same, except top tray)
siThick, 0.400 mm
Glue, 0.150 mm
Bias plane, 0.100 mm
Glue, 0.100 mm
faceThick, 0.200 mm
(SuperGlast/Bot 0.290)
Glue, 0.075 mm
(dots)
Core
Not to Scale, separated to
indicate grouping!
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Details of Bottom Face of Standard Tray, including Bottom Face of
Top Tray
Core
Face sheet, 0.200 mm
Glue, 0.075 mm
convThickReg, 0.105
mm Tungsten
Glue, 0.100 mm
Bias plane, 0.100 mm
Glue, 0.150 mm
Not to Scale, separated to
indicate groupings!
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TKR Geometry Review
Silicon, 0.400 mm
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Radiation Lengths for some common Materials
RadLen vs Z
70
H
RadLen (g/cm2)
60
50
C
40
Polystyrene
Kapton, Mylar
O
G10
30
Al
Si
20
Fe
Cu
10
CsI
W
0
0
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10
20
30
40
Z
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50
60
70
80
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Example of Composite Material Calculation
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Composite Material Calculation, continued
X0(C) = 42.7
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Another Calculation
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Another Calculation, continued
X0(C) = 42.7
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Summary of “Active” Radiation Lengths
• Converter
• Silicon
• Core
1.0850
0.1584 
0.0513 
• BotFace
• TopFace
• BotBias
0.0363 ?
0.0341 ?
0.0250
June 11, 2003
• Top 3 items are simple
elements; 93% of r.l.
• Remaining 3 are
composites; mostly
carbon, with Si, Cu, etc.
• TopFace is thicker than
BotFace; should show
more r.l.; Found a typo!
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Passive Tracker
• Walls: Carbon Fiber, bolts, Al coating 
• MCM: Calculation based on BTEM module ½ 
– Could be redone, if we had the info
• Closeout
– Complicated shape; dimensions and effective density
should be reviewed.
• Other material not in model
–
–
–
–
Cables
Flexures
Heat straps
???
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Conclusion
• Recent discovery of bugs has prompted a careful
review of our model.
• Several new (minor) bugs have been uncovered.
• Minor design changes since last implementation
need to be incorporated.
• Modeling of passive tracker should be reexamined.
• No big changes are expected.
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