larp rotatable collimators for lhc phase ii collimation 18 april 2007 larp collaboration meeting –...

LARP Rotatable Collimators for LHC Phase II Collimation

18 April 2007LARP Collaboration Meeting – Fermilab

Tom Markiewicz/SLACRepresenting Gene Anzalone, Eric Doyle, Lew Keller & Steve Lundgren

BNL - FNAL- LBNL - SLAC

US LHC Accelerator Research Program

LARP Collab. Mtg. - 18 April 2007 Rotatable Collimators - T. MarkiewiczSlide n° 2 / 59

Collimator Design as of April 2006

beam

beam

•136mm diameter x 950 mm long copper jaws (750 mm effective length + 2 x 100mm tapers)

•Vacuum tank, jaw support mechanism and support base derived from CERN Phase I


EXTERNAL COIL PERMITS 1 REV OF JAW

CERN PHASE I JAW POSITIONING MECHANISM – USE IF POSSIBLE

25mm thick annular (hollow core) copper jaw backed by continuous helical cooling tube

Collimator Design as of April 2006

NLC Jaw Ratchet Mechanism assumed

Sheet Metal formed RF transition


Stop prevents thermal bowing of jaws from intruding on minimum gap. Deal with:

•Residual swelling into beam•External vertical actuator and bellows that also has +/- 5mm transverse float•Mid-jaw recess•Forces possibly unbalanced front vs. back

Leaf springs allow jaw end motion up to 1mm away from beam. Must allow:

•Thermal motion while minimizing gravity-deflection

•Axial expansion

Adjustable central aperture-defining stop and leaf spring support required to prevent jaws

from deforming 1200um into beam


One Year Later…

• New jaw-hub-shaft design which eliminates central stop & flexible springs• New reverse-bend winding concept for the cooling coil which eliminates

the 3 end loops, permitting longer jaws and freeing up valuable space for jaw supports, rotation mechanism and RF-features

• Internally actuated drive for rotating after beam abort damages surface

These concepts discussed at October 2006 collaboration meeting

Main accomplishments in the last 6 months• Several test pieces manufactured and examined• Rotation & support mechanism fully designed• All parts for first full length jaw assembly manufactured & in-house• Test lab fully wired, plumbed and equipped

BUT…– Still have not brazed nor thermally tested a full length jaw assembly– Still do not have a complete mechanical (=“RC1”) prototype


http://www-project.slac.stanford.edu/ilc/larp/

Monthly meetings with CERN

Up-to-date in labeled folders

Written version of this talk


Advances since RC1 Baseline

solid core more cooling


New Idea to Eliminate Central Stop Jaw-Hub-Shaft

1. Hub located, in Z, near peak temperature location, which lowers peak temperature, reducing gradient and bending.

2. Max deflection toward beam reduced if the shaft deflection can be minimized

3. Both ends of jaw deflect away from beam. (Note: swelling component of deflection is not corrected.)

4. Cooling coils embedded in I.D. of outer cylinder.

shaft jawhub


Max Jaw Temp

Jaw max toward beam

Coll surface sagitta

Eff length

Operating Condition

Jaw Design Deflection Reference

oC m m m Steady State Baseline stop 86.5 36 394 0.43 Baseline shaft 86.5 426 394 0.43 Refined baseline shaft 66.3 238 202 0.63 Jaw-hub-shaft shaft 70.6 84 197 0.74 Transient Baseline stop 231 97 1216 0.24 Baseline shaft 231 1260 1216 0.24 Refined baseline shaft 197 853 913 0.31 Jaw-hub-shaft shaft 224 236 781 0.39

Evaluate jaw-hub-shaft for 950mm jawsw/ 22.5mm deep cooling tubes with hollow Moly shaft

versus 750mm jaw baseline & 750mm jaw solid copper shaft refined baseline

Notes:1. Deflection means deviation from straight (um).2. Eff length is length of jaw (m) deflected <100 um compared to maximum deflection point.3. Deflection is combination of swelling and shaft bending4. Molybdenum shaft static deflection due to gravity = 68um5. 7 min allowable aperture achieved by setting jaws of first collimator at 8.5 .

New Baseline


Model showing 42.5 winds of coil on Mandrel with 80mm wide space for U-Bend at downstream end

Restrain each tube on centerline of bearing

200mm

136mm dia


Comparison of Hollow Mo shaft and Solid Copper Shaft to same FLUKA secondaries: Improved deflections

Solid Cu, 75cm tapered jaw, asymmetric hub

Tubular Moly, 95 cm straight jaw, symmetric hub

Steady State=1 hour

= 12 min for 10 sec

Steady State=1 hour

= 12 min for 10 sec

Gravity sag 200 um 67.5 um

Power absorbed 11.7 kW 58.5 kW 12.9 kW 64.5 kW

Peak Temp. 66.3 °C 197 °C 66 °C 198 °C

Midjaw x 100 um 339 um 83.6 um 236 um

Effective Length 51 cm 25 cm 74 cm 39 cm

Sagitta 221 um 881 um 197 um 781 um


October 2006 Version of Jaw Upstream end with actuator and cooling lines

Lundgren


Current Upstream end with actuator and cooling lines


Universal Joint Drive Axle Assembly

• Thermal Expansion of molybdenum Shaft of 0.290mm (transient) causes each diaphragm to distort by 0.145mm.

• Shaft sag causes an in plane rotation of the Shaft ends of 0.00025 radians causing an equal distortion of the diaphragm.

• Transverse displacement one of the ends of the Shaft relative to the other by +/- 1.5mm causes an angular distortion of 0.0015 radians in the diaphragm.

• Worst case is for a Vertical Collimator with maximum “slew” of 0.0015 radians added to the sag component of 0.00025 radiansfor a total of 0.00175 radians of bending of the diaphragm.

Lundgren


Jaw Mount with Geneva Mechanism

0.5mm thick diaphragm

100 Tooth Worm Gear

Geneva Driver Wheel (on ratchet shaft)

Geneva Driven Wheel(on Worm shaft)

Lundgren

Linear actuator

http://www.flying-pig.co.uk/pages/mechindex.htm


Upstream end vertical section

Jaw

Geneva Mechanism

Support Bearings

Worm GearShaft

Water CoolingChannel

U-Joint Axle

Lundgren

1-2mm Gap

Diaphragm


Upstream end horizontal section

Support to Support 1000mm

Overall length 930mm

Facet length ~905mm

LundgrenCollimating Surface RF Transitions


Summary of New Baseline Configuration

Jaw consists of a tubular jaw with embedded cooling tubes, a concentric inner shaft joined by a hub located at mid-jaw

– Major thermal jaw deformation away from beam– No centrally located aperture-defining stop– No spring-mounted jaw end supports

Jaw is a 930mm long faceted, 20 sided polygon of GlidcopShorter end taper: 10mm L at 15o (effective length 910mm)Cooling tube is square 10mm Cu w/ 7mm square aperture at depth = 24.5 mmJaw is supported in holder

– jaw rotate-able within holder– jaw/holder is plug-in replacement for Phase I jaw

Nominal aperture setting of FIRST COLLIMATOR as low as 8.5 – Results in minimum aperture > 7 in transient 12 min beam lifetime event

(interactions with first carbon primary TCPV)– Absorbed power relatively insensitive to aperture: for 950mm long jaw

p=12.7kW (7), p=12.4kW (8.23)Auto-retraction not available for some jaw orientationsJaw rotation by means of worm gear/ratchet mechanism “Geneva Mechanism”


RF Shielding: Baseline DesignTie-Rods with Fingers Connect Jaws & Tank

Issues:– At a few 10s of grams per finger (.1 mΩ/contact) force causes

excessive deflection of the tie-rod holding fingers– Cooling required

Discussions with CERN and PeP-II experts in progress

Tie-Rods


Revised RF Spring configuration

Double Wedge Adapters mountacross Tank ceiling & floor

2 RF springs mount to each Adapter

Jaw facet RF springs mount on Tank ceiling & floor

Shorter length springs also mount to

Tank ceiling & floor

Note: Jaw facet springs are wide enough for line contact thru full transverse travel range


Alternate Sheet Metal Transition configuration

NORMAL CONTACTS TO TANK CEILING & FLOOR

ROUND

RECTANGULAR

HOURGLASS

RETRACTED 22.5MM

Note: Not all Jaw facets are shown


BrazeTest #1 Cooling Tube

Jaw Center Mandrel

~100 mm

~70 mmdia

~100 mm dia


Aluminum Mandrel for Coil Winding Test and to test 3-axis CNC Mill before cutting 200mm and

950mm Copper Mandrels

200mm

Cooling Tube aligner


Development of Winding Tooling

Vise-Type Roller-Type

Aluminum Mandrel with Coil Wound

Test Winding the 200mm Copper Mandrel


Fabrication of Quarter Jaws for 2nd Braze Test


Final Wind of 200mm Copper Mandrel


First 200mm PrototypeBefore-After Brazing Coil to Mandrel

4 braze cycles were required before part deemed good enough to do jaw braze

Learned a lot about required tolerances of cooling coil and mandrel grooves

Pre-Coil-Braze


More Winding Tooling Developed

1m winding tooling Mill vise as precision bender


1mm raised shoulder (Hub) at center

Full Length Molybdenum Shaft


Braze Test#2 Delivered 19 Dec 2006


Vacuum Bake Test Results: 4/1/07

1st Jaw Braze Test Assembly has been vacuum baked at 300 degrees C for 32 hours.

•LHC Requirement = 1E-7 Pa = 7.5E-10 Torr•Baseline pressure of Vacuum Test Chamber:

4.3E-7 Pa (3.2E-9 Torr)•Pressure w/ 200mm Jaw Assy. in Test Chamber: 4.9E-7 Pa (3.7E-9 Torr)•Presumed pressure of 200mm lg. Jaw Assy.:

6.0E-8 Pa (4.5E-10 Torr)•Note: above readings were from gauges in the foreline, closer to the pump than to the Test Chamber. Pressures at the part could be higher.

Plan to discuss vacuum results with SLAC experts (Dan Wright) and to possibly incorporate vacuum pumpout drill holes into the design.

Next step: Sectioning & braze quality examination


Aluminum Test Mandrel with 80mm Gap for Downstream U-Bend (11/17/06)


Braze Test #3: 200mm Cu mandrel with U-Bend

Upstream end

Downstream end

Minor re-machining required to engage drive pins of coil

winding tooling


Tubing Wound and Tack Welded to Mandrel at the U-Bend

Note stub ends of cooling tube


Braze Test #3: Ready in Braze Lab for coil-mandrel braze

Next steps:

-Braze 8 quarter-round half-length jaws

-Vacuum test?

-Section & examine braze quality


Cut-away of Cu-Mo Hub CAD Model

#1 - Mandrel Dummy#2 - Mo Shaft Dummy#3 - Mo Backing Ring#4 - Cu Hub with braze wire grooves

#2#1

#3

#4

Initial plan to braze one long Mo shaft with raised hub to inner radius of Cu mandrel deemed unworkable

Brazing HALF-LENGTH shafts to a COPPER hub piece and THEN brazing the Cu hub to the Cu mandrel deemed possible

First test if Mo “backing ring” sufficient to keep Mo and Cu in good enough contact for a strong braze joint


Cu-Mo Hub Braze Test parts

#1 - Mandrel Dummy (not shown)#2 - Mo Shaft Dummy#3 - Mo Backing Ring#4 - Cu Hub with braze wire grooves

#2

#3 #4


Sectioned Cu-Mo Hub Braze Test Assemblyafter 3 additional heat cycles to mimic full

assembly procedure

#1 - Mandrel Dummy#2 - Mo Shaft Dummy#3 - Mo Backing Ring#4 - Cu Hub

#2

#3 #4

#1


Moly-Cu Joint Declared “Good” by SLAC Braze Shop Experts, but…..

Small holes held braze wire

•Grain boundary issues?•Possible fracturing?

Samples being sliced & polished and sent to Physical Electronics lab for analysis

Cu-Mo joints we care about

1mm expansion gap


More Coil Tests Planned

• Twist a length of actual cross-section to failure for a measure of the margin of safety and maximum torque requirements.

• Bend samples of actual cross-section into required configurations.

• Section samples to inspect for internal distortion shapes and smoothness of transitions.

4-1/2 Turnswithout failure


Full length Mandrel: In-House & Inspected

– Most groove widths meet specification except for a few at each end.– Positioning of distorted areas could indicate damage was done by

excessive forces imparted by hold down fixturing during machining.– Future Mandrel drawings will include a note warning about potential

damage caused by excessive clamping forces.

out of specification grooves


Up Beam Flex Mount Assembly components

Geneva Wheel & Actuator

(Ultimately, bearings will be ceramic; these steel)

SLAC Shops will fab first Universal Joint/Axle and Geneva Wheel Rotator Assembly by June 5

http://www.flying-pig.co.uk/pages/mechindex.htm


RF Contact Springs for Investigation


Main Steps Still Needed for Full Size Single JawFor Thermal-Mechanical Tests

After 200mm Jaw tests Completed Satisfactorily

– Jaw 1/4 sections (16 needed of 24 now at SLAC) require slight modifications for braze gap requirements.

– Moly shaft (at SLAC) will need to be cut in two pieces and brazed to copper hub

– Drill Cu mandrel for Moly Shaft

– Decide to use in-house SLAC Copper, or order our own (Finland 20 week delivery) or use CERN order of Ni-Cu alloy, anneal & wind mandrel

– Winding and Braze Cycles

– Drill jaw to accept resistive heater• Understand (ANSYS) any change to expected performance


Test Lab Preparation ~Finished

Clean space with gantry access Basic equipment: Granite table, racks,

hand tools Power supplies to drive heaters Chiller & plumbed LCW to cool jaw 480V wiring for heater power supplies

• required engineering review, safety review, and multiple bids (?!)

Acquire Heaters• 5kW resistive heaters from OMEGA

PC & Labview Rudimentary software tests only

National Instruments DAQ with ADCs• Data Acquisition and Control Module• 32-Channel Isothermal Terminal Block• 32-Channel Amplifier

Thermocouples Capacitive Sensors– Vacuum or Nitrogen (?)– Safety Authorization (!!!)

Adjacent 16.5 kW Chiller

Heater Power Supplies staged for installation in rack


Steps on Path to the Two Jaw Mechanical Prototype RC1

• Successful thermal performance of first full length jaw• Complete the design of RC1 RF features• Successful test of a working model of the Geneva wheel & universal joint• Fit-up and initial tests on 1st full length jaw• Complete fabrication of second jaw (Glidcop?, Moly??) with full support

assembly on the four corners• Remodeling of CERN parts for interface to US parts

– Models and assemblies of the various Collimator Mounting Stands are complete

– An enlarged vacuum tank has been modeled and some CERN support stand modifications have been identified

– No fabrication drawings have been done as yet• Acquisition of Phase I support & mover assemblies

– CERCA/AREVA REFUSES to supply SLAC– Recent (18 APR 07) proposal to sell SLAC a non-functional CERN

TCS collimator with damaged tank & bellows:


PLASTIC DEFORMATION of ENTIRE JAW after a BEAM ABORT ACCIDENT?

PRELIMINARY RESULT:– 0.27 MJ dumped in 200 ns into ANSYS model– Quasi steady state temperature dependent stress-strain

• bilinear isotropic hardening

– Result: • plastic deformation of 208 um after cooling, sagitta ~130um

– Jaw ends deflect toward beam

• Jaw surfaces at 90 to beam impact useable, flat within 5 um

Doyle

54 umBeam side

Far side Melted material removed


Boundary Conditions

During energy deposit (0 – 200 ns). All nodes (both ends) constrained in z

After energy deposit (200ns – 60 sec), z-constraints released. Original analysis used this constraint at all times.


Induced Activation of Secondary Phase II Collimators

Issue Raised by LARPAC Reviewers

Contact Dose Rate for Exposures at 4E9 p/s loss rate

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08

Cooling Time (sec)

mS

v/h

r 30d

100d

1yr

20yr

1min 1hr 1d 1wk 1mo 1yr

Exposure

( t~1 day )

15 mSv/yr = max dose for rad worker at CERN

Work in progress by Mokhov et al

Have requested dose rate at ~1m


Inter-Lab Collaboration

Good will & cooperation limited only by busy work loads– Three video meetings since October 26, 2006 – Many technical exchanges via email– CERN FLUKA team modeling Rotatable Collimator– CERN Engineering team looking at SLAC solid-model of RC and

independently doing ANSYS calculations of thermal shock– CERN physicist

• investigating effects of Cu jaws at various settings on collimation efficiency• Participating in discussion of RF shielding design

– SLAC Participation in upcoming CERN Phase II brainstorming meeting– Ralph Assmann to visit SLAC in May/June 2007

Need to continue to pursue– Plan to bring a TCS assembly to SLAC – Plan to bring a spare support and mechanism to set gross x, y, u jaw

angles– Plans to understand scope and time scale of beam tests


Phase II – TCSM FLUKA Model @ CERNLuisella Lari


Extract from talk by Elias Metral Adressisg RF Concerns of SLAC Collimator Design


Collaboration on ANSYS Calculations of SLAC Design Performance and Damage


Collaboration on Tracking Efficiency StudiesChiara Bracco - CERN


Chiara’s (Frightening) Conclusions


CERN Collimation Plan & Schedule

0) Assume SLAC LARP develops Rotatable Collimator1) Develop TWO other complementary designs2) Develop a test stand for the three designs3) Fabricate 30 Phase II collimators of chosen design & 6 spares

The target schedule for phase 2 of LHC collimation:2005 Start of phase 2 collimator R&D at SLAC (LARP) with CERN support.2006/7 Start of phase 2 collimator R&D at CERN.2008 Completion of three full phase 2 collimator prototypes at CERN and SLAC.

Prototype qualification in a 450 GeV beam test stand at CERN.2009 Installation of prototypes into the LHC and tests with LHC beam at 7 TeV.

Decision on phase 2 design and production.2010 Production of 36 phase 2 collimators.2011 Installation of 30 phase 2 collimators during the 2010/11 shutdown.

Commissioning of the phase 2 collimation system.LHC ready for nominal and higher intensities.


Summary of Progress since October 2006 Meeting

Design & Calculation– Mechanical design almost complete

• RF shielding concepts need finalization & testing– ANSYS calculations examining permanent deformation in case of

accidental beam abort complete

Fabrication– Fabricate and braze together a 2nd short (20cm) copper mandrel, cooling

tube and 4- quarter-round jaw pieces• Vacuum Bake test complete• To be sectioned & examined for braze quality

– Fabricate a 3rd mandrel with improved features & wind cooling coil• Await coil braze, 8-jaw braze, vacuum test, sectioning & examination

– Acquire first full length mandrel– Acquire first full length Molybdenum shaft

• Newest design will require it to be cut in half & brazed to a central copper hub– Moly-Copper test braze complete & subject to 4 braze cycles

• Visual checkout OK; await SEM analysis of Copper-Moly joint


LARP Collimator Delivery Schedule

Done Braze test #1 (short piece) & coil winding procedures/hardware

Prep heaters, chillers, measurement sensors & fixtures, DAQ & lab

Section Braze test #2 (200mm Cu) and examine –apply lessons

Braze test #3 (200mm Cu) – apply lessons learned

Fab/braze 930mm shaft, mandrel, coil & jaw pieces

2007-09-01 1st full length jaw ready for thermal tests

Fab 4 shaft supports with bearings & rotation mechanism

Fab 2nd 930mm jaw as above with final materials (Glidcop) and equip with rf features, cooling features, motors, etc.

Modify 1st jaw or fab a 3rd jaw identical to 2nd jaw, as above

Mount 2 jaws in vacuum vessel with external alignment features

2008-04-01 2 full length jaws with full motion control in vacuum tank available for mechanical & vacuum tests in all orientations (“RC1”)

Modify RC1 as required to meet requirements

2009-01-01 Final prototype (“RC2”) fully operational with final materials, LHC control system-compatible, prototype shipped to CERN to beam test


Phase II Task Summary

There has been continued progress in design and excellent but slow progress on the necessary small scale projects to finalize procedures.

Time estimates for thermal test of first jaw and construction of first 2 jaw prototype (RC1) are expanding. In June 2006 DOE was told

“Expect thermal tests and completely tested RC1 device by end of FY06 and mid-FY07, respectively”

Now need to say:

“Expect thermal tests and completely tested RC1 device by end of FY07 and mid-FY08, respectively”

Jeff Smith (Ph.D., Cornell joins SLAC Collimation team ~July 1, 2007

Better project management needed on my part.

Need to incorporate schedule in CERN White Paper plan.

Extra Material Follows


Specification Changes Relative to April 2006 Design

RC1 Report 12/12/05 Current spec value value jaw Length 95cm including 10cm end tapers 93cm with 1cm end

tapers Diameter 136mm 20 facets, tangent to

136mm Material Copper Glidcop AL-15 cooling Embedded helical channel Reduced helix depth,

Helix pitch reversal Special features Circumferential slots to reduce

thermal-induced bending, if no RF problems

eliminated

deformation <25um toward beam; <325mm away in steady state; <750um away in 10 sec transient

Inward: 84um SS, 236um Trans – 1st coll to be set at 8.5 for clearance

Range of motion 25mm per jaw, including +/- 5mm beam location drift

27.5 mm per jaw including +/- 5mm

Aperture stop Range of motion Controls aperture from 5-15 sigma (2-6mm full aperture), must float +/- 5mm as jaws are moved to follow beam drift

eliminated

Heat load Steady state 11.3 kW 12.9kW Transient 56.5 kW 64.5kW RF contacts configuration Sheet metal parts subject to

CERN approval New geometry


Heat deposited in major components (W/m^3) in 1 hr beam lifetime operation

Component Units Upbeam Downbeam Stub shaft, aluminum W/m^3 6.5e3 52e3 Bearing, Si3N4 W/m^3 8.3e3 66.4e3 Image current bridge, aluminum W/m^3 150e3 400e3 Mo shaft (~const in z, concentrated in =120o) W 520 Jaw, Glidcop AL-15 (heat highly variable in z and ) kW 12.8


Major jaw dimensions and calculated cooling performance

Component dimension units Jaw OD tangent to 20-faceted surface 136 mm Jaw OD to facet vertices 137.7 mm Jaw ID 66 mm Jaw length, including 10mm (in z) x 15o taper on each end 930 mm Mo Shaft OD 64 mm Mo Shaft ID 44 mm Hub length (centered) 150 mm Cooling tube OD x ID (square x square) 10 x 7 mm Embedded helix – center radius 80 mm Helix – number of turns ~47 - Cooling tube length – helix + entry + exit from vac tank ~16 m Flow per jaw 9 l/min Velocity 3 m/s Water temperature rise (SS 12.8 kW per jaw) 20.3 C Pressure drop 2.4 bar

larp rotatable collimators for lhc phase ii collimation 18 april 2007 larp collaboration meeting –...

Documents

length of jaw

jaw baseline

jaw support mechanism

jaw end motion

length jaw assemblystill

shaftjawhubevaluate

central stop jawhub

version of jaw upstream