LARP Collimation – Engineering & Analysis Adapting the NLC Consumable Collimator to LHC Phase II Secondary Collimation BEAM 2 BEAM 1 LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

LARP Collimation – Engineering & Analysis Overview Review NLC consumable collimator Compare NLC & LHC requirements Conceptual design: NLC collimator as adapted to LHC Thermal performance of candidate materials Unresolved issues LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

NLC Consumable Collimator BPMs (not shown) at inlet & outlet Aperture is sole internal degree of freedom. Movers align collimator to beam as sensed by BPMs LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

NLC Consumable Collimator Heat dissipated by radiation. DT = 42C @ 10W/jaw Rigid datum structure aligned to beam by BPMs Aperture control mechanism: Thermal effects limited to small region LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle NLC Test Unit Cutaway Aperture support one end of rotor only Dual ball bearings preloaded for tilt-stability LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle NLC Aperture-control Mechanism Located at one end of rotor only. Tilt–stability not well controlled in test unit. LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle NLC Aperture-Defining Geometry One independent variable (stop roller spacing) defines aperture. s = stop roller spacing LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Major Differences - NLC & LHC Specs Specification NLC LHC Comments beam pipe ID 1cm 8.4cm Spatial constraints due to beam spacing jaw length ~10 cm 120 cm jaw tilt-stability gap range 0.2 – 2.0mm 0.5 – 60mm Spatial constraints SS power, per jaw ~1W – 10W ~1kW – 10kW (material dependent) LHC requires water cooling LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle LHC Collimator Mechanism Concept Basic NLC design morphed to fit LHC constraints Jaws hidden to show structure 1.2m long jaws, 150mm diameter Helical coolant supply tubes flex, allow one rev of jaw Aperture supported a both ends for stability, tilt adjustment Also shown: aperture support at jaw center thermal deflection away from beam no tilt control LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Thermal Distortion ANSYS Simulations 10 s apertures beam 150mm OD, 25mm wall, 1.2m long Simply supported FLUKA heat generation for 10x10x24 rectangular grid mapped to similar area of cylinder Steady state: 1hr beam lifetime Transient:10 sec @ 12 min beam lifetime I.D. water-cooled 20C, h=11880 W/m^2/ Various materials: Al, 2219 Al, Be+Cu, Cu, Invar, Inconel Ti, W rejected based on 2-D analysis Variations limit cooling to 45o arc solid cylinder jaw cut in two shorter pieces Cu, 61C support dx=221 um support LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

360o cooling of I.D. 45o cooling arc Note transverse gradient causes bending Note axial gradient 61C 89C Note more swelling than bending support dx=221 mm Spec: 25mm dx=79 mm 64% less distortion support LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle Material Comparison for SS & Transient Thermal Deflection Green: meets alternative spec of 50um (SS) and 200um (transient). Notes: BeCu is a made-up alloy with 6% Cu. We believe it could be made if warranted 2219 Al is an alloy containing 6% Cu Cu/Be is a bimetallic jaw consisting of a 5mm Cu outer layer and a 20mm Be inner layer Cu – 5 mm is a thin walled Cu jaw Super Invar loses its low CTE above 200C, so the 152um deflection is not valid LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Jaw Materials - discussion Only graphite meets the 25um deflection spec for both operating cases. Be-containing jaws meet the spec for the SS case but not for the transient. Be is unacceptable for environmental/safety reasons. Al benefits from the reduced (45o) cooling arc. nearly meets the spec for SS condition Excessive deflection for the transient What next? Divide jaw in shorter sections Use center-of-jaw aperture stops - jaw deflects away from the beam Revisit materials not modeled in 3-D: W & Ti LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Effect of shortened jaws, dense material, carbon pre-radiator Notes: Aperture transition from 10s to 7s 7s cases based on CERN ray files for interactions in TCPV pre-radiator – Phase I carbon collimator concentrates energy deposition toward front of Phase II jaw. LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Shortened jaws/dense material - discussion Dividing jaws beneficial Short front jaws more swelling than bending Cu jaws nearly meet relaxed specs W jaws look good, but: temperatures and power densities very high (cooling system) deflections much greater if referred to jaw centerline What next? Increase cooling arc in W jaws Simulate single 48cm W jaw Calculate cooling system loads LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Conceptual design - coolant channels Limited cooling arc: free wheeling distributor – orientation controlled by gravity – directs flow to beam-side axial channels regardless of jaw angular orientation. Far side not cooled, reducing DT and thermal distortion. 360o cooling by means of a helical channel. Lowers peak temperatures but, by cooling back side of jaw, increases net DT through the jaw, and therefore thermal distortion. Could use axial channels. LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Conceptual design - Stop Roller Details Ball nut (turned by actuator outside vacuum chamber). Ball screw (stationary) Thrust bearing Hole for beam passage As shown in current model: aperture range limited to ~ 10mm. This can be improved but this mechanism will not be able to produce the full 60mm aperture. Auxiliary jaw retracting mechanism needed. Also note vulnerability of mechanism to beam-induced heating. LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Beam’s Eye View of Aperture Mechanism Jaw retracted, aperture ~60mm LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Geometrical limits due to 150mm rotor, 224 mm Beam Axis Spacing 30mm jaw travel (in red) causes jaw to intersect adjacent beam pipe. No space for vacuum chamber wall. Resolution: 1) smaller jaw diameter 2) vacuum envelope encloses adjacent beam pipe 3) less jaw motion 4) reduce diameter of adjacent beam pipe. LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Alternate Stop-Roller Design LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Status of Phase II LHC Collimator Concept Deflection spec will be very hard to meet Relax deflection spec Allow use of Be Reduce jaw length Aperture stop mechanisms vulnerable to beam heating/damage Relocate ball screw outside beam path – like NLC (jaw ends only) Stop rollers unavoidably within region of beam pipe Combine NLC rotary jaws with LHC positioning mechanism Space limitations prevent 60mm max aperture with 150mm o.d. jaws Reduce jaw diameter Will likely increase deflection Adversely affects aperture stop mechanism Reduce opposing beam pipe diameter Include a pass-through for the opposing beam in the collimator vacuum chamber Reduce the maximum required aperture LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle

Status of Phase II LHC Collimator Concept - continued Cooling system loading is problematic for dense jaw materials Other engineering issues Jaws must fully retract in power-off condition Spring load jaws outward. Inward-forcing springs (necessary in any case) sized to overcome outward-forcing springs and grounded on solenoid or pneumatic device which gives way when power is off. Design of flexible coolant supply tubes Manufacturability of jaws (material dependent) How to apply heat loading for testing Rotor indexing mechanism LARP Coll. Video-conf. May 12, '05 Phase II Collimator Engineering - E. Doyle