LHC Phase II Collimation Status Report and RF Contact, Jaw Cooling, Jaw Support Concepts

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LHC Phase II CollimationStatus Report and RF
Contact, Jaw Cooling, Jaw Support Concepts

• E. Doyle 9/12/05

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Status

• Conceptual design
• Jaws
• 136mm OD x 950mm L
• helical cooling channel
• eliminates water-vacuum joints
• 179um deflection steady state
• alternative axial channels limited azimuthally
• water-vac joints (can be air guarded)
• risky flow directing mechanism
• 73um deflection SS

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Status

• Jaw support
• center span aperture control/flex end mounts
• gt deflection away from beam
• Flex cooling supply
• coiled rigid tubing
• high torque to rotate jaw
• bellows tubing
• unavoidable water-vac joints
• RF signal path
• doable concept need verification from CERN

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Status

• Issues not addressed
• jaw rotating mechanism
• weight of jaws, forces due to flex cooling tubes
  how much motor torque required?
• Center stop mechanism
• Cooling of RF parts

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RF Contact Concept
Spring loaded fingers ground two jaws through
range of motion
Rigid round-square transition
Jaw support gap adjustment borrowed from CERN
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RF Contact Concept
Stationary top bottom walls
Step may be detrimental
Flexure ramp follows jaw motion sliding
contact with jaw and top/bottom walls
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RF Contact Concept
RAMP WRAPS 180o
STEP ELIMINATED
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• Jaw Support Concept
• Adjustable central jaw stops (not shown) define
  gap
• Flexible bearing supports allow jaw thermal
  distortion away from beam

Self aligning bearing
Leaf springs allow jaw end motion up to 1mm away
from beam
CERNs jaw support/positioning mechanism. Vacuum
tank, bellows, steppers not shown.
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Jaw Support Concept unresolved issues
Clearance problems with RF contacts
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Helical cooling passages fabrication
concept Based on CERNs design no weld or braze
between water vacuum

• Tube formed as helix, slightly smaller O.D. than
  jaw I.D.
• O.D. of helix wrapped with braze metal shim
• Helix inserted into bore, two ends twisted wrt
  each other to expand, ensure contact
• Fixture (not shown) holds twist during heat cycle

• Variations
• Pitch varies with length to concentrate cooling
• Two parallel helixes to double flow
• Spacer between coils adds thermal mass, strength
• Electroform jaw body onto coil

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Flex Cooling Supply Concept
Unresolved interferences between RF parts and
cooling and support parts Jaw rotation mechanism
not devised Substantial forces to rotate jaw
CERN design Jaw supported on individually
moveable shaft at each end, controlled by
steppers external to tank. Bellows allows full
range of jaw motion Continuous one-piece cooling
tube brazed to jaw, exits tank at each end
through shaft.
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Flex Cooling Supply Concept
Stub-shaft (bearing not shown)
Contiguous with helical tube inside jaw. Formed
after assembly-brazing of jaw and installation of
bearing on stub-shaft Exits through support shaft
per CERN design Material CuNi10Fe1, 10mm O.D.,
8mm I.D.
Support shaft
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Flex Cooling Supply Concept
Coil deforms plastically but lt ultimate
strain But stress in sharp tubing bends not
considered here (may exceed ultimate strain if
cold-formed) Therefore work hot? bearings must
be in place how to protect bearings Alternative
flex leads hot-formed separately, braze to
internal cooling helix using air-guarded joint to
protect vacuum from water
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Bellows-tubing alternative
Lower forces on jaw support mechanism More water
leak risk threaded connections shown would not
be used, but requires brazed and welded joints