Doyle RC1 prototype engineering studies

LARP Phase II Secondary Collimator RC1 Review SLAC 12/15/05Prototype Engineering Studies: 

LARP Phase II Secondary Collimator RC1 Review SLAC 12/15/05 Prototype Engineering Studies

LHC Phase II collimator concept development: 

LHC Phase II collimator concept development LHC & NLC collimators compared FLUKA/ANSYS jaw thermal response simulations A major % of our effort so far model evolution Baseline Jaw concept Material selection Cooling channel arrangement Jaw support Jaw geometry Baseline collimator concept aperture control jaw support/actuation RF parts cooling water supply Unresolved issues

Phase I Supporting System: 

Phase I Supporting System Fixed base Adjustable base Pivoting cradle (manual adjustment +/-10º) Jaw actuation system Vacuum Tank SLAC will utilize as much of CERN support and actuation systems as possible – must work in horizontal (shown), vertical (90o) and skew (+/- 45o)

Phase I Mechanical design: 

Phase I Mechanical design Steppers & roller screws – jaw ends independent Return Springs C/C, copper, SST jaw, 1.2 m long Vacuum tank Bellows not shown (4x) Coolant in/out SLAC concept substitutes - rotate-able jaws for 1.2m long Phase I jaws - Larger vacuum tank to allow max jaw diameter

NLC Consumable Collimator: 

NLC Consumable Collimator 6.0 Note short length of collimation material. L/D = .02

Slide6: 

Phase II Baseline layout 136mm diameter x 950 mm long jaws (750 mm effective length due to taper). Vacuum tank, jaw support mechanism and support base derived from CERN Phase I.

NLC & original LHC specs – major differences: 

NLC & original LHC specs – major differences Bottom Line: LHC & NLC collimators are different animals * * This spec infeasible, has been relaxed

Slide8: 

Water cooled 2-d & (3-d rectangular) model 3-d “Hollow cylinder” model - Uniform or limited arc cooling “Solid” model Tubular cooling channels Uniform ID Cooling – simulates helical or axial channels H2O simulation – helical flow shown Progression of ANSYS models – increasingly realistic beam

Material thermal performance (Hollow Cylinder Model)- O.D = 150 mm, I.D. = 100 mm, L = 1.2 m- NLC-type edge supports: 

Material thermal performance (Hollow Cylinder Model) - O.D = 150 mm, I.D. = 100 mm, L = 1.2 m - NLC-type edge supports

Slide10: 

Cu chosen as best balance between collimation efficiency, thermal distortion & manufacturablity

Slide11: 

Central Aperture Stop Swelling neutralized Bending neutralized NLC-type Aperture control - Swelling neutralized - Bending toward beam Shaft support (Phase I) -Swelling toward beam -Bending toward beam Aperture-defining support Choice of Aperture-Defining Scheme - To Minimize Bending and Swelling Deformation toward Beam

Slide12: 

61C Note transverse gradient causes bending Interesting side trip: 64% less distortion if cooling is limited to a 36o arc centered on beam path. 360o full I.D. cooling 36o arc cooling

Slide13: 

Limited cooling arc: free wheeling distributor – orientation controlled by gravity – directs flow to beam-side axial channels. Pro: Far side not cooled, reducing DT and thermal distortion. Con: peak temperature higher; no positive control over flow distributor (could jam); difficult fabrication. 360o cooling by means of helical (or axial) channels. Pro: Lowers peak temperatures. Con: by cooling back side of jaw, increases net DT through the jaw, and therefore thermal distortion; axial flow wastes cooling capacity on back side of jaw. Helical and axial cooling channels illustrated

Slide14: 

Helical cooling passages chosen for manufacturablity, beamline vacuum safety Per CERN’s Phase I design – no water-vacuum weld or braze 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 may vary with length to concentrate cooling Two parallel helixes to double flow Spacer between coils adds thermal mass, strength Electroform jaw body onto coil

Slide15: 

Max Cu temp 200 Possible boiling Max water return temp Deflection 325 & 750 (SS & trans) Baseline Jaw Performance

Estimates for downbeam collimator heat loading and deflection – scaled from worst case baseline (green): 

Estimates for downbeam collimator heat loading and deflection – scaled from worst case baseline (green)

Slide17: 

Jaw diameter – limited by vacuum tank size and required range of motion. Vacuum tank size limited by proximity of opposing beam pipe in all collimator orientations. Jaw Diameter Determined

Slide18: 

jaw tends to bow toward beam due to heating. Stop prevents reduction of gap Jaw ends spring-loaded to the table ass’y (next slide) … move outward in response to bowing Shallow groove => smooth contact surface safe from beam accidents May use two stops to control tilt Adjustable central gap-defining stop Stop in/out position controls aperture, actuator external, works through bellows.

Slide19: 

Self aligning bearing Leaf springs allow jaw end motion up to 1mm away from beam Adjustable central jaw stops (previous slide) define gap Flexible bearing supports allow jaw thermal distortion away from beam CERN’s jaw support/positioning mechanism. Vacuum tank, bellows, steppers not shown. Flexible end supports used in conjunction with central gap-defining mechanism

Slide20: 

Rigid round-square transition Spring loaded fingers ground two jaws through range of motion RF contact overview Sheet metal parts flex to follow jaw motion Clearance problems to be resolved Concept satisfies CERN RF requirements - Need sufficient contact pressure Cooling issues not addressed

Slide21: 

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. Unresolved interferences between RF parts and cooling and support parts Jaw rotation mechanism not devised Substantial forces to rotate jaw Mandrel to support coil not shown Flex Cooling Supply Tube Concept Space required for flexible water connections results in 95 cm maximum jaw length.

Slide22: 

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. Stub-shaft (bearing not shown) Support shaft Detail of Flex Cooling Supply Tube

Slide23: 

ANSYS simulation: Axial stress for un-grooved and grooved jaw with axially uniform heat input. Grooves reduce bending deflection Note: RF taper requirements may make this concept un-feasible

Specifications for baseline Phase II collimator: 

Specifications for baseline Phase II collimator * * Relaxed from original spec baseline design deviates

Unresolved Issues: 

Unresolved Issues Jaw actuation mechanism How to handle mass of rotary jaws (fail open springs) Availability of CERN actuation mechanism for SLAC use is being discussed Jaw rotary indexing mechanism force to rotate jaws acceptable? concept not developed do we know angular position of jaw at all times? RF parts – taper requirement details not clear central groove in jaws (smooth track for central aperture stop) strain-relieving grooves in jaws what is the acceptable range of taper angles for the jaw ends Heat generation in thin RF parts Need details of CERN support stands, etc Effects due to accident does accident cause unacceptable gross distortion of the jaw? do RF fingers work in contact with damaged surface? How much material melts and where does it go? – depends on jaw orientation is central aperture stop safe from contamination by melted material? Beam tests may be required

LHC Phase II Collimation: 

LHC Phase II Collimation BONUS SLIDES

Phase I Jaw - Design Principles: 

Phase I Jaw - Design Principles 1. Jaws in C/C or graphite 2. Cooling Cu-pipes (2 x 3 turns) and plate pressed against the jaw, brazed to the bar. 3. Main GlidCop® support bar Glidcop support bar Cu cooling plate c/c

Material Properties: 

Material Properties

Heat Transfer by Boiling Water: 

Heat Transfer by Boiling Water

Construction possibility – jaw with axial cooling channels: 

Construction possibility – jaw with axial cooling channels

NLC Aperture-Defining GeometryOne independent variable (stop roller spacing, s) defines aperture.: 

NLC Aperture-Defining Geometry One independent variable (stop roller spacing, s) defines aperture. s = stop roller spacing

NLC Jaw Indexing Mechanism: 

NLC Jaw Indexing Mechanism

NLC suspension and aperture-defining mechanism: limitations in LHC environment. 150mm jaw full 30 mm retraction showing interference with opposing beam pipe. Vac envelope with pass-through for beam 2 as possible solution.: 

NLC suspension and aperture-defining mechanism: limitations in LHC environment. 150mm jaw full 30 mm retraction showing interference with opposing beam pipe. Vac envelope with pass-through for beam 2 as possible solution.