LARP Collimation – Engineering & Analysis Adapting the NLC Consumable Collimator to LHC Phase II Secondary Collimation BEAM 2 BEAM 1 LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

LARP Collimation – Engineering & Analysis Overview Review NLC consumable collimator Compare NLC & LHC requirements Conceptual design NLC collimator adapted to LHC NLC jaws in LHC mechanism Thermal performance of candidate materials Unresolved issues LARP Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 problem; thermal bending problem gap range 0.2 – 2.0mm 0.5 – 45mm * Spatial constraints; NLC mechanism limited gap range SS power, per jaw ~1W – 10W ~1kW – 15kW (material dependent) LHC requires water cooling, possible power densities in boiling regime * Original max gap was 65mm, revised 5/12/05 LARP Collimation meeting June 15, 2005 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 (our first guess) Helical coolant supply tubes flex, allow one rev of jaw Aperture supported a both ends for stability, tilt adjustment Alternative (also shown): aperture support at jaw center thermal deflection away from beam no tilt control LARP Collimation meeting June 15, 2005 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 45mm aperture. Auxiliary jaw retracting mechanism needed. Also note vulnerability of mechanism to beam-induced heating. LARP Collimation meeting June 15, 2005 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 (shown) 3) less jaw motion (45mm max aperture – agreed 5/12/05) 4) reduce diameter of adjacent beam pipe. LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle NLC concept - problems Large jaw motions not possible estimated max 15 – 20mm Auxiliary mechanism to fully retract jaws Gap-defining mechanism intrudes into beam-pipe stay clear connect around outside of jaw => backlash, thermal sensitivity move stops outward => lower sensitivity,poor mechanical advantage Suitable only at ends of jaw – can’t prevent gap narrowing Clearance problems with adjacent beam Reduce jaw diameter => even less space for stop rollers One solution: instead of auxiliary mechanism to fully retract jaws…why not just use LHC mechanism in the first place? LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

NLC-LHC Hybrid: Cylindrical jaws in LHC Mechanism Jaw diameter 136mm Maximum aperture 45mm Jaw length 950mm (including end tapers) to fit existing mechanism Tank widened & deepened LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

NLC-LHC hybrid configuration - problems More thermal distortion with shaft support than NLC-type edge support Additional thermal swelling Tank and mechanism too short for full length NLC-type jaws shorten jaws or expand mechanism Jaws may be too heavy for LHC mechanism .75m long x 136m diameter weighs 97kg (+) (limit = ?) Solutions Lighten jaws (how?), strengthen mechanism Add rigid adjustable stop to limit minimum gap spring loaded ends able to deform away from beam LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Adjustable gap-defining stop Stop prevents gap closing as jaw bows due to heat Jaw ends spring-loaded to the table ass’y (not shown) … move outward in response to bowing May use two stops to control tilt LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

NLC concept & Hybrid concept – shared problem Jaw thermal effects / collimation efficiency tradeoff Deformation Swelling and bending Structural failure or loss of properties due to temperature cycling Heat removal Control deformation by targeted heat removal Potential for boiling Dense materials Pro: higher collimation efficiency Con: higher temperature increased deformation Increased tendency to boil higher heat flux density LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle Thermal Simulations Water cooled 3-d model FLUKA generated energy deposit mapped to blue area Water cooling: 360o complete I.D. ~45o between arrows 3-d model FLUKA generated energy deposit mapped to curved area Water cooling: ~45o arc between arrows 2-d model 25 x 80mm grid FLUKA generated energy deposit at shower max LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

2-d simulation results – boiling considerations 80mm x 25mm rectangular section located at shower max Water cooled back surface TCSH1, 80% TCPV debris + 5% beam LARP Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 Heat flux to water of 10^6W/m^2 or greater is in regime of possible film boiling LARP Collimation meeting June 15, 2005 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. environmental/safety issues, low collimation efficiency Al benefits from the reduced (45o) cooling arc. nearly meets the spec for SS condition Excessive deflection for the transient case Ti: excessive deflection 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 LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle Effect of shortened jaws, dense material, carbon pre-radiator – deflections referred to jaw edge 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 Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle Effect of shortened jaws, dense material, carbon pre-radiator – deflections referred to shaft 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 Collimation meeting June 15, 2005 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 deflection specs W jaws look good, but: temperatures and power densities very high (cooling system) deflections much greater if referred to jaw centerline What next? Adopt and apply material damage criteria (short & long term) Consider Glidcop Increase cooling arc in W jaws Other deflection reducing tricks (circumferential grooves) LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Un-grooved 10kW evenly dist. Grooved 40% deep Temperature Vertical displacement fixed symm plane symm plane LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Grooved Cylindrical Jaw ANSYS model – 150mm O.D., 25mm wall, 120cm long, Two symmetry planes: mid-span; beam/jaw centerline Grooves: 10mm deep, 50mm spacing 10kW heat, evenly distributed 45 deg cooling arc Case Power (kW) Tmax (C) Deflection - edge ref (um) Deflection - center ref (um) Cu - 10s 10.4 - mapped FLUKA 89 79 ~130 Cu 10.0 - even distributed 59.5 33 ~100 Cu - grooved 15 ~74 LARP Collimation meeting June 15, 2005 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 or other light material Reduce jaw length Force deflection away from beam Compensate for SS deflection in set-up, gauge transient relative to SS NLC Aperture stops 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 LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Status of Phase II LHC Collimator Concept - continued Cooling system loading is problematic for dense jaw materials Suppress boiling by means of overpressure Utilize boiling high heat transfer coefficient Risk of film boiling and melt-down Other engineering issues Determining realistic failure criteria for jaw materials Jaws must fully retract in power-off condition NLC mechanism: 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. LHC mechanism: includes this capability Design of flexible coolant supply tubes Manufacturability of jaws (material dependent) How to apply heat loading for testing Rotor indexing mechanism LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

LHC Phase II Collimation BONUS SLIDES LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Phase II Collimator Engineering - E. Doyle Material Properties LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Heat Transfer by Boiling Water LARP Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Beam’s Eye View of Aperture Mechanism Jaw retracted, aperture ~60mm LARP Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle

Alternate Stop-Roller Design LARP Collimation meeting June 15, 2005 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 Collimation meeting June 15, 2005 Phase II Collimator Engineering - E. Doyle