VELO Mechanics

1
VELO mechanical aspects

• VELO Mechanics
• RF/vacuum foil
• Rectangular bellow
• Wake field suppressors
• Cabling
• Summary Outlook

2
Global system design
air

• Decouple access to Si detectors from access to
  1ary vacuum
• Use (ultra)pure neon venting
• NEGs need not be baked after access to Si
  detector
• Baking up to 150 oC is possible
• Mount two detector halves independently
• Note large-size, rectangular bellows and thin RF
  screen

1ary vacuum
2ary vacuum
3
(No Transcript)
4
RF and vacuum separation foil

• Separate prim. and sec. Vacuum
• Stiffness
• Protect against RF effects
• Wakefields
• EMC
• Restrict amount of material

• Overlapping detectors
• stereo angle
• alignment

5
RF foil box outside view
6
RF foil box inside view
7
FEA on Al. 250 mm
0.25 mm top plate 0.5 mm side plates 15
mbar max. displacement 0.35 mm max. stress MPa
58.8 MPa

8
Thin RF/vacuum foil
2000
2001

• Aluminum (250 mm thick)
• FEA max ?p ? 15 mbar irreversible deform., no
  safety factor
• successfully welded 100 ?m on 300 ?m
• press-shaping developed superplastic forming of
  AlMg3
• cheap readily available (compared to Be)
• Foil can be produced with radius of 6 mm
• Sharp edges of detector have to be rounded off

9
Superplastic Forming

• Aluminium Superplastic Forming (SPF)
• Hot stretching process sheet of superplastic
  grade aluminium alloy is forced onto or over a
  single surface tool by the application of air
  pressure.

Discovered in 1920 (Pb-Zn, Cd-Zn) not much
interest in the West. 1947 sverhplastichnost
http//www.superform-aluminium.com T 470 -
520 C small grain size bubble or cavity forming
10
SPF mold (1)
11
SPF mold (2)
12
Latest RF foils
Deformation 32 mm at 15 mbar 20 mm at -15
mbar Completely elastic
He leak tested
Concrete mold has been replaced by a brass one
13
Explosive Formation
Statement producer Uniform thickness after
deformation. Test will be performed.
14
Rectangular Bellow (1)
15
Rectangular Bellow (2)
The diaphragms were cut out of a 0.15 mm
stainless steel plate with a laser machine. Next
the diaphragms have successfully been shaped in a
forming mold.
16
Rectangular bellow (3)
The forming mold with the pressure envelope. The
pressure envelope is used to keep the system in
place.
17
Rectangular bellow (4)
With nitrogen at a pressure of 10 bar the
diaphragm are deformed into the right shape.
18
Rectangular bellow (5)
19
Rectangular bellow (6)
7 stainless steel plates (0.15 mm) will be vacuum
brazed together. Before brazing, the 0.05 mm
Ni-alloy solder is spot welded between the
layers.
20
Wake field suppressors (1)
Aim Provide a continuous conducting wall
throughout the VELO to guide the mirror charge

• Install wake field suppressors after mounting
  2ary vacuum container
• Upstream is easy mounted with large flange off
• Downstream is more delicate mount through top
  flanges
• 70 ?m CuBe, O/C, coated

21
Wake field suppressors (2)
The Wake field suppressor is made of two 0.075 mm
thin CuBe foils, compressed with gear wheel and
rack. CuBe is chosen for the good electrical and
elastic properties. The foil can be hardened at
320 degrees Celsius to get better spring
properties.
22
Wake field suppressors (3)
New design of the The Wake Field Suppressor,
which follows better the contour of the beam
pipe..
23
Cabling (1)
Almost solid cable tree!

• Cables
• Connectors
• very expensive!

24
Cabling (2)

• Cables inside vacuum
• Heat production
• Signal shielding

• Kapton with 3 Cu layers
• Outer layers for power and ground
• Inner layer for signal

Very expensive! New design has been made to
optimize nr. of kapton sheets required
25
Cabling(3)
26
Summary Outlook

• Base solution for RF/vacuum foil
• 300 mm base material Al with 3 Mg
• 170 mm at inner region
• Radius 6 mm
• Rectangular bellow
• Diaphragms are ready
• Will be assembled the coming months
• Wake field suppressors
• The wake field suppressors work fine
• A new design is in production
• Cabling solution available
• Has to be discussed further