September 2002 A. Das LBNL 1

ATLAS Pixel Detector

Pixel Support Tube Rails:Design and Prototyping

September, 17 2002 Review

September 2002 A. Das LBNL 2

ATLAS Pixel DetectorIntroduction

I. Two Rail Designs, V and Flat, are used to provide 4 point, Pseudo-Kinematic Support

II. Rails are for delivery of the Detector only not for Support

III. Longest rails in actual detector are approx. 9 feet long (2.5 m)

IV. Short test rails were made to check shape and surface quality

September 2002 A. Das LBNL 3

ATLAS Pixel Detector

Rail Design

DETAIL 4DETAIL 3

DETAIL 1

Old Design

New Design

DETAIL 2

September 2002 A. Das LBNL 4

ATLAS Pixel Detector

Rail Tools

311.00

Flat Rail V-Rail

Cross Sections

Aluminum Tools

•CTE = 22.95 ppm/K

Cut By Wire EDM

•Length of 12.25 in. (311mm)

•Wire EDM is cheap, but surface is poor, so

Tooltec release film was used

Actual Rails 2.5 m in length

September 2002 A. Das LBNL 5

ATLAS Pixel Detector

Lay-Up Procedure (Tool + Tooltec)

Teflon Tooltec (5 mil)

September 2002 A. Das LBNL 6

ATLAS Pixel Detector

Lay-Up Procedure (Tool + Tooltec +Mat)

17 gsm Prepreg Reinforced Mat (10 mil)

Teflon Tooltec (5 mil)

September 2002 A. Das LBNL 7

ATLAS Pixel Detector

Lay-Up Procedure (All Layers)

8 Plies P-30 Cloth (1 mm total thickness)

17 gsm Prepreg Reinforced Mat (10 mil)

Teflon Tooltec (5 mil)

September 2002 A. Das LBNL 8

ATLAS Pixel Detector

Prototype Parts

• High Strength Carbon Fiber Cloth– The cloth is 1K tow square weave, and the resin is EX1515, 125 gsm, 5 mil thickness– Cloth has lower stiffness than the YSH-80• Print-Through– Print-through was a problem on the initial parts, the rough fiber structure on the top of lay-up was pushed

through to the smooth side by the pressure during the curing cycle.– Since no additional resin dams were laid down and perforated A4000R was used as the release ply during

cure, much resin bled through to the surrounding bag and breather material. It was believed that the print-through was caused by the lack of resin within the part.

– Resin dams were laid down on second set of prototypes and non-perforated A4000R was used with the result that the tool side was much smoother, proving hypothesis correct.

• Tool Part Interaction– Another possible problem is the tool part interaction associated with the difference in CTE’s between the

aluminum tool and the part.– Tool Part Interaction can cause the part to “bow” in the cross-sectional and or longitudinal direction

September 2002 A. Das LBNL 9

ATLAS Pixel DetectorTool-Part Interaction (Cross-Sectional Bow)

•Both V-Rail and Flat Rail Prototype Parts fit the tool

very well with no gaps.

•Tool Part Interaction doesn’t seem to be a problem in the

cross-section

•Will CMM cross-section later to find out for sure

September 2002 A. Das LBNL 10

ATLAS Pixel DetectorTool-Part Interaction (Longitudinal Bow)

R R

222 )( RRyx

hyL

x ,2

02)2( 22 yRhL

28

2 h

h

LR

We need an equation relating radius of bow to max deflection HR

We can find the radius from height-gauge measurements, and use the equation above to

calculate max bow.

Equation for Circle

September 2002 A. Das LBNL 11

ATLAS Pixel DetectorWorst-Case Longitudinal Bow

Second Flat-Rail Prototype

-1

0

1

2

3

4

5

6

7

8

9

-8 -6 -4 -2 0 2 4 6 8

Distance along length (in.)

Var

iati

on

in

hei

gh

t (m

il)

Measured

Best-Fit, R=2,352 in.

Second V-Rail Prototype

-1

0

1

2

3

4

5

6

-8 -6 -4 -2 0 2 4 6 8

Distance along length (in)

Var

iati

on

in

hei

gh

t (m

il)

Measured

Best Fit, R=3,451 in.

Plot of longitudinal bow versus length of part for the second V-Rail Prototype

•A curve-fit with radius of 3,451 in. best approximated the data.

•For the final 9ft.(108 in.) long part, the estimated max bow is approximately .422 in.

Plot of longitudinal bow versus length of part for the second Flat Rail Prototype

•Radius of 2,352 best approximates data

•Max bow of approximately .620 in. for final part.

September 2002 A. Das LBNL 12

ATLAS Pixel Detector

Conclusions

• Preliminary measurements using a height-gauge on prototype parts show that a worst-case bow of approximately .620 in. is expected on the final 2.5 m long rail

• There are three ways to compensate for the longitudinal bow caused by Tool Part Interaction in the final part.

I. A Reverse-Bow can be machined in the tool itself to compensate

II. The “bowed” part can be bonded to the PST so that it lies correctly.

III. In the future, steel tools with much lower CTE will be used in place of aluminum to minimize the effects of tool part interaction.