Status of Vertex at NIKHEF

1
Status of Vertex at NIKHEF

• VELO Mechanics
• RF/vacuum foil
• Rectangular bellow
• RF measurements
• Cabling
• Summary Outlook

2
VELO Overview
3
Secondary vacuum box
4
Material data
Material AlMg3 Young's modulus 70.000
MPa Poisons ratio 0.33 Shear Modulus 27.3
GPa Yield Strength 80-180 MPa Ultimate
Strength 180-260 MPa Electrical
conductivity 1.9x107 ohm-1 m-1 (almost 50 of
pure Al) Weldable!
5
Full size foil
Vacuum tight foil from 300 µm AlMg3 Buckling in
the center toblerones is solved Ribs (2.5mm high)
are added at the forward-end to increase the
stiffness.
6
FEM analysis
ACP 5080, AlMg4.5Mn (Alimex)
7
FEM analysis input
Input model for the FEM calculations
8
FEM analysis results
CONCLUSION The max stress (91 MPa) is 33 below
the Yield Strength (130 MPa), so still elastic
and safe. A max displacement of 0.3 mm is no
problem.
9
RF foil and Silicons-reinforcements


10
Bellow
11
Rectangular Bellow
Sagging problems
Vacuum leaks in corners
Parallel effort in edge-welding
12
RF pick-up (1)
Foil thickness 30 mm Al Power level in the 50
ohm coaxial line 10 Watts at 40MHz. The Si
detector was 5 mm from the foil outside conductor
of the coax.
In this condition there was no influence on the
noise background.
13
RF pick-up (2)
Cut a hole in the foil and put the silicon strip
just 5 mm in front of this hole. The power
level in this coax line was still 10 watt at
40MHz.
The fieldlevels from this radiator are much
higher then we can obtain with the beam through
the RF foil.
The result was that we do not see influence on
the working of the silicon in combination with
the electronics of the test setup at NIKHEF in
febr. 2002.
14
RF shielding
Frans Kroes has produced a note on Attenuation
of an EM field by AlMg4 screen of 0.2 mm
Conclusion Assuming a conductivity of 0.33 of
pure Al At 1 mm distance to the rf
screen 1.415 x 10-3 V/m
15
Conductivity

• ?Pure Al 37 x 106 Ohm-1 m-1
• Measured (accuracy 10) conductivity of
• 1 m long 1 cm wide strips of AlMg3

• ?undeformed 17 x 106 Ohm-1 m-1
• ?deformed 11 x 106 Ohm-1 m-1

• 45 for undeformed
• 30 for deformed material

16
Cabling

• Cables inside vacuum
• Heat production
• Signal shielding

• Kapton with 3 Cu layers
• 25 micron kapton outside layer
• --- 17 micron Cu (foil)
• 75 micron kapton
• --- 17 micron lines (100 micron width)
• 75 micron kapton
• ---17 micron Cu (foil)
• 25 micron kapton outside layer

17
Outgassing (2)
Poly-amide-imide coating 1.5 m2 Kapton
cables 20 m2
18
Summary and outlook

• Bellow
• Still under development
• RF measurements
• 300 µm Al gives sufficient rf shielding
• Side flaps not needed
• Outgassing
• poly-amide-imide
• Kapton cables with 3 Cu layers