November 29, 2002 NIKHEF-1 Hans de Vries
Status RF foil
• RF/vacuum foil Purpose
Production methods used
Deformations: static - overpressure
Electrical properties
Coating
Cables
Interference Silicons
November 29, 2002 NIKHEF-2 Hans de Vries
RF and vacuum separation foil(1)
• Protect against RF effectsWakefields in Vertex vesselEMI in detectors
• Good conductivity
Why?• Separation extreme-high-vacuum of LHC from
Detector vacuum– (outgassing electronics, cables, NEG coating,…!)
• Stiffness
Physics requirement:• Restrict amount of material
– preferably low-Z (small radiation length)• Thin
• Detectors should overlap– Alignment– Stereo angle
• Complicated shape
November 29, 2002 NIKHEF-3 Hans de Vries
RF and vacuum separation foil(2)
Production from foil:Requirements for:• Stiffness• Welding• Thickness• Shape
•Choice of material•Methods to be used
November 29, 2002 NIKHEF-4 Hans de Vries
VELO Overview
November 29, 2002 NIKHEF-5 Hans de Vries
Secondary vacuum box
November 29, 2002 NIKHEF-6 Hans de Vries
Secondary vacuum box (detail)
November 29, 2002 NIKHEF-7 Hans de Vries
Material data:
Material: AlMg3Young's modulus: 70.000 MPaPoisons ratio: 0.33Shear Modulus: 27.3 GPaYield Strength: 80-180 MPaUltimate Strength: 180-260 MPaElectrical conductivity: 1.9x107 ohm-1 m-1
(almost 50% of pure Al)Weldable!
November 29, 2002 NIKHEF-8 Hans de Vries
Production of RF foil
– Hot gas forming• Deform at 350° Formation speed
– Superplastic deformation• Deform at 520°
– One cycle, p 10 bar Crystal growth, melting,Vacuum leaks
• Methods investigated:– Cold formation
• Press- anneal at 420° (or 350 °) - cool- press …– More than 15 cycles, 2 – 100 bar– Two or more molds Time consuming
– Explosive formation Uncontrolled
November 29, 2002 NIKHEF-9 Hans de Vries
Full size foil
Full size rf foil with reinforcement ribs
November 29, 2002 NIKHEF-10 Hans de Vries
3D measurement set-up
Mesh for 3D machine
-1000
-950
-900
-850
-800
-750
-700
-650
-600
-1600 -1400 -1200 -1000 -800 -600 -400 -200 0
Exploded view
November 29, 2002 NIKHEF-11 Hans de Vries
Measurement of one slot
-900
-890
-880
-870
-860
-850
-840
-830
-820
-810
-702 -701 -700 -699 -698 -697 -696 -695 -694 -693
20 x 5 measurement points
November 29, 2002 NIKHEF-12 Hans de Vries
3D result for one slot
-818
-830
-841
-852
-864
-875
-887
-694 -697 -701
-84
-83.5
-83
-82.5
-82
-81.5
-81
-81.5--81
-82--81.5
-82.5--82
-83--82.5
-83.5--83
-84--83.5
November 29, 2002 NIKHEF-13 Hans de Vries
Projection for one slot
-84.2
-84
-83.8
-83.6
-83.4
-83.2
-83
-82.8
-82.6
-82.4
-82.2
-82
-702 -701 -700 -699 -698 -697 -696 -695 -694 -693
Variation in depth of one slot ± 0.1 mm
November 29, 2002 NIKHEF-14 Hans de Vries
Minimum depth along foil
-85
-83
-81
-79
-77
-75
-73
-71
-69
-67
-65
-1600 -1400 -1200 -1000 -800 -600 -400 -200 0
November 29, 2002 NIKHEF-15 Hans de Vries
Minima enlarged
-84.4
-84.2
-84
-83.8
-83.6
-83.4
-83.2
-83
-1400 -1200 -1000 -800 -600 -400 -200
Variation in depth for all slots: ± 0.2 mm
November 29, 2002 NIKHEF-16 Hans de Vries
Close-up minima
-85
-83
-81
-79
-77
-75
-73
-1000 -950 -900 -850 -800
Position of slots along foil: 0.1 mm
November 29, 2002 NIKHEF-17 Hans de Vries
Thickness measurements
Along central beam line: 0.28 0.29 0.27 mm
0.24 0.27 0.25 0.26 0.30 0.27 0.24 0.27 mm
Largest curvature point: 0.15 mm
November 29, 2002 NIKHEF-18 Hans de Vries
FEM analysis: input
Input model for the FEMcalculations
November 29, 2002 NIKHEF-19 Hans de Vries
FEM analysis: down
10 mbar over pressure in primary vacuum
Maximum deflection 0.88 mmin “floppy part” of foil
November 29, 2002 NIKHEF-20 Hans de Vries
FEM analysis: up
10 mbar over pressure in secundary vacuum
Maximum deflection 1.04 mmin “floppy part” of foil
November 29, 2002 NIKHEF-21 Hans de Vries
Deflection measurement
November 29, 2002 NIKHEF-22 Hans de Vries
FEA for full box (1)
November 29, 2002 NIKHEF-23 Hans de Vries
FEA for full box (2)
November 29, 2002 NIKHEF-24 Hans de Vries
FEA for full box (3)
November 29, 2002 NIKHEF-25 Hans de Vries
FEA for full box (4)
November 29, 2002 NIKHEF-26 Hans de Vries
RF pick-up (1)
Foil thickness 30 m 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.
November 29, 2002 NIKHEF-27 Hans de Vries
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 theelectronics of the test setup at NIKHEF in febr. 2002.
November 29, 2002 NIKHEF-28 Hans de Vries
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
November 29, 2002 NIKHEF-29 Hans de Vries
Conductivity
Pure Al = 37 x 106 Ohm-1 m-1
• Measured (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
November 29, 2002 NIKHEF-30 Hans de Vries
Coating
• The extreme deformation might result in tiny leaks in the material.
• Also a protective layer might be used at the inside of the detector box.
• Apply poly-amide-imide coating– Solution in N-Methyl-2-Pyrrolidone (NMP)– Drying and polymerization at 60º, 150º, 260º and
315º C– Properties like Kapton and Torlon – Good electric insulation– Radiation resistant 30 MGy, strength not changed
• Outgassing properties have been studied
November 29, 2002 NIKHEF-31 Hans de Vries
Final solution
A thin layer of poly-amide-imide is air brushed on the inside of the foil for electrical protection and to increase vacuum tightness
Effect of the layer:
Leak detectionWith Helium
Before After1.2e-3 3.2e-71.2e-5 7.2e-73.6e-5 5.2e-73.8e-5 2.4e-61.2e-6 3.2e-7
November 29, 2002 NIKHEF-32 Hans de Vries
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
November 29, 2002 NIKHEF-33 Hans de Vries
Outgassing (1)
Massspectra of outgassing after 48 hour
0.0E+00
5.0E-13
1.0E-12
1.5E-12
2.0E-12
0 5 10 15 20 25 30 35 40 45 50
Mass [amu]
Ion
Crr
ent
[A.l/
s.cm
^2]
Coated
Aluminum
Outgassing after 48 hour - Coated-Aluminum = 2.6E-09 mbar.l/s.cm 2̂ - Aluminum = 6.5E-10 mbar.l/s.cm 2̂
Outgassing poly-amide-imide coating
November 29, 2002 NIKHEF-34 Hans de Vries
Outgassing (2)Contribution in the pressure of the secondary vacuum by out gassing
Seff=500l/s
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
0 1 2 3 4 5 6 7 8 9 10
time [day]
P [
mb
ar]
Coating
Flat Cable
Poly-amide-imide coating: 1.5 m2
Kapton cables: 20 m2
November 29, 2002 NIKHEF-35 Hans de Vries
RF foil and Silicons
November 29, 2002 NIKHEF-36 Hans de Vries
RF foil and Silicons-reinforcements
November 29, 2002 NIKHEF-37 Hans de Vries
Summary
• Full size RF/vacuum foil has been obtained– Material: 300 m Al with 3% Mg– Minimal radius 8 mm – Deviations measured: ± 0.3 mm– FEM analysis has been performed– Variations measured for 10 mbar
overpressure– Electrical properties measured– Application of poly-amide-imide– Kapton cables with 3 Cu layers