Phase II Collimators for the LHC

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Phase II Collimators for the LHC the LARP
Collimation Program
US LHC Accelerator Research Program
bnl - fnal- lbnl - slac

• 21 April 2005
• ILC Collaboration Phone Meeting
• Tom MarkiewiczSLAC

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LARP Collimation Program Tasks

• Task 1 Studies on a rotating metallic phase 2
  collimator
• Responsible T. Markiewicz, SLAC
• Task 2 Fast set-up and optimization of cleaning
  efficiency (simulations and tests at RHIC)
• Responsible A. Drees, BNL
• Task 3 Improvements with tertiary collimators at
  the LHC experimental insertions
• Responsible N. Mokhov, FNAL
• Task 4 Radiation tests of LHC collimator
  materials for phase 1 and phase 2 new proposed
  work package
• Responsable N. Simos, BNL

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Task 4 Radiation tests of LHC collimator
materials

• ASSESS the effects of proton irradiation on
  material properties
• BNL AGS/BLIP (200 MeV protons) Hot Cell Sample
  Measurement Facility
• Properties thermal expansion, mechanical
  properties, thermal conductivity/diffusivity and
  thermal shock
• Materials 2-d weave carbon-carbon and exact
  graphite used in Phase I jaws plus materials
  considered viable for Phase II jaws
• Status Task to begin in the second half of FY05

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Task 3 Modeling IP5 and CMS with tertiary
collimators
1m Cu TCTV and TCTH _at_ z150m25mm x 80mm jaws _at_
8.4s
1mW/gm _at_ 106 p/s
150m
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TCT-Induced Energy Deposition in Triplet Quads
and Backgrounds entering CMS/ATLAS
Photon Flux
Peak Energy deposition of 0.35mW/g in Q3 SC coils
at bMAX _at_ z50m _at_ 106 p/s and design spec of
DQlt0.53mW/gm ? max loss rate at TCT 2 x 106 p/s
1000 photons/cm2/s _at_ 106 p/s scraped physics
backgrounds
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Task 2 Benchmarking Tracking Codes with RHIC
Data
Ions Agree
Protons Data does not agree
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LHC Beam Dump Abort System
R. Schmidt HALO 03
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Beam Dump Kicker Failure
R. Schmidt HALO 03
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Bunches on Collimators ? Delay in Retriggering
Dump Kicker
Dt now lt 0.7 ms ? 8 bunches on colls
J.-B. Jeanneret HALO 03
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Graphite or Carbon-Carbon Chosen for Phase I
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Normal Proton Loss Rates

• Handle heat load from normal proton loss rates
• 487 kW for 10 sec
• 97 kW indefinitely
• NB
• Power ABSORBED by any individual collimator ltlt
  Power lost by beam
• Maps of ENERGY DEPOSITION in the system are not
  yet available

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LHC Phase I Carbon/Carbon Secondary Collimators
cooled for 7kW DC
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C-C Phase I Prototypes Made TestedFull Order
Placed
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Impedance Limits LuminosityCollimators Dominate
Impedance
Unstable
Stable
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Quench Protection Sets Maximum Current Given
Collimator System Inefficiency
7.6E6 p/m/s _at_ 7 TeV
12min
Nom. I
Intensity
Inefficiency
4E11 p/s x 2E-5 8E6 p/s corresponds to stated
quench limit in Q3 given maximum dQ/dV
2E-5Desired
2E-4Phase II(assumes 1m Cu)
11E-4Phase I
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IR7 Collimator Layout2m gaps (32 in IR3 7)
left for Phase II secondary collimatorsFocus on
the 2 SC behind primary collimators
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Reminder of SLAC NLC Consumable Spoiler as
Prototype for Phase II LHC Secondary Collimator

• Differences LC / LHC
• Jaw length
• Maximum gap
• Power deposited

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Task1 Studies of a rotating metallic collimator
for possible use in LHC Phase II Collimation
System

• If we ALLOW (rare) ASYNCH. BEAM ABORTS to DAMAGE
  METAL JAWS, is it possible to build a ROTATING
  COLLIMATOR
• that we can cool to lt10kW, keeping TltTFRACTURE
  and PH2Olt1 atm.
• that has reasonable collimation system efficiency
• that satisfies mechanical space accuracy
  requirements

Overall Plan FY 2004 Introduction to project FY
2005 Phase II CDR and set up of a collimator lab
at SLAC FY 2006 Design, construction testing
of RC1 FY 2007 Design, construction no-beam
testing of RC2 FY 2008 Ship, Install, Beam Tests
of RC2 in LHC May-Oct 2008 run FY 2009 Final
drawing package for CERN FY 2010 Await
production installation by CERN FY
2011 Commissioning support RC1Mechanical
Prototype RC2 Beam Test Prototype
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Study of Material for Secondary Collimators
Yunhai Cai
Heavy material is more effective in terms of
efficiency of the system. So copper is chosen
because its high thermal conductivity.
Length should be about 1 meter. Achievable
efficiency is about 3.5x10-4 at 10 s.
Copper
Similar result was obtained by Ralph Abmann
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Vertical Skew Collimators
Secondary halo in normalized phase space at the
end of collimation system
Primary collimator
Collimators are projected to The end of
collimation system
6 and 7 sigma contours
This is an independent check of the simulation
code, since the collimators are plotted according
to the lattice functions calculated using MAD.
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Tertiary Halo Particles Escaped from the
Secondary Collimators
TCSG.E5R7.B1 last skew collimator
Number of particles beyond 10s is 73, which is
consistent with the efficiency calculation 73/144
446 5x10-4. Tertiary halo at large
amplitude is generated by the large-angle Coulomb
scattering in the last collimator. If we add a
tertiary collimator at 8s in the same phase
as the collimator TCSG.D4L7.B1 after the
secondary collimators, the efficiency should be
better than 1x10-4.
TCSG.D4L7.B1
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Energy Deposition in Metal Phase II Secondary
Collimators w/ Carbon Phase I Collimators Open
Jaws at 10 sigma Pencil Beam with 805510
loss model Only 1 TCSH in current (v6.5)
collimation configuration
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Power absorbed in one TCSH1 jaw at 10s when 80
(5) of 450kW of primary beam interacts in TCPV
(TCSH1)
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Steady State Temperature of TCSH1 at shower max
when jaw at 10s is in contact with 20C H2O and
80 (5) of 90kW of primary beam interacts in
TCPV (TCSH1)
25mm
Jaw 25x80mm Solid Cu PTOT1270W
CV Cu taken as constant
80mm
Doyle 2004-09-28
Power Density to H2O 0.38 MW/m2(H2O boils at 1
atm _at_ 1.3E6)
Boundary Condition Convection
CoefficientHCH2011880 W/m2/C
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Time Dependence of Peak Temperature of TCSH1
shower max when jaw at 10s is in contact with
20C H2O and 80 (5) of 450kW of primary beam
interacts in TCPV (TCSH1)
Beam Side of Jaw
Jaw 25x80mm Solid Cu PTOT6400W
Doyle 2004-09-28
Water Side of Jaw
10 sec
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Heat Load Temperature Summaryfrom 2D ANSYS
(Tensile Limit)
(180)
(150)
(770)
(680)
(140)
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What is the damage area in a missteering
accident?
Missteered beam (9E11 protons) on secondary Jaw
Copper Jaw
Cross section at shower max.
Copper
2.5 cm
Fracture temp. of copper is about 200 deg C
Assumed Damage threshold seems inconsistent with
FNAL experience
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Power Deposition on First Secondary Collimatorin
12 Min. Lifetime (kW per jaw)
Sensitivity to aperture and to source of halo
H, V, or S
Notes 1. Collimator data, ray files, and loss
maps from LHC Collimator web page, Feb. 2005. 2.
Must add contribution from direct hits on
secondary jaws.
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LHC Collimator Mechanism ConceptEnd and center
aperture stops included in same model

• Note Conceptual model. Not much detail
  engineering yet. Not included
• Rotary jaw indexing mechanism
• Loading springs which hold jaws against aperture
  stops
• Open aperture power-off mechanism
• Vacuum chamber, BPMs, movers, etc

Jaws hidden to show structure

• 1.2m long jaws
• Helical coolant supply tubes flex, allow one rev
  of jaw
• Jaws supported a both ends for stability, allow
  tilt control
• Alternative jaws supported in center
• thermal deflection away from beam
• no tilt control

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360o limited arc coolant channel concepts
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.
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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 possible
vulnerability of mechanism to beam-induced
heating.
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Geometrical limits due to 150mm rotor, 224 mm
Beam Axis Spacing, 8.8cm beam pipe
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.
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3D Time Dependent Thermal Distortion Simulations
beam

• 150mm OD, 25mm wall, 1.2m long
• Simply supported
• ANSYS simulation FLUKA energy deposit for
  10x10x24 rectangular grid mapped to similar area
  of cylinder
• Most cases TCSH1 receives 80 of debris from
  primary (TCPV) plus 2.5 of direct beam per jaw.
  TCSH1 at 10s.
• Steady state 1hr beam lifetime
• Transient10 sec _at_ 12 min beam lifetime
• I.D. water-cooled 20C, h11880 W/m2/C
• Temperature rise of H2O not modeled
• Materials Al, 2219 Al, BeCu, Cu, Invar,
  Inconel
• Ti, W rejected based on 2-D analysis
• Variations
• 45o of ID nearest to beam cooled (not whole
  360o)
• solid cylinder (not thick wall) 45o cooled

Cu, 61C
support
dx221 um
support
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Material Comparison for SS Transient Thermal
Deflection LHC Spec. is 25um

• 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
• Green shading meet our suggested alternative
  spec of 50um for SS and 200um (1s) for the
  transient.

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Technical Discussions of Phase I Project

• Only low Z, Be compounds, absorb sufficiently
  little energy, conduct the heat away fast enough,
  and are stiff enough to come close to meeting jaw
  straightness tolerance of 25um
• Deflection of jaw away from beam of collimators
  immediately downstream of primaries (hardest hit)
  may be allowed if sufficiently low and overall
  collimation efficiency maintained by remaining
  collimators
• Be, C, and Al do not provide adequate cleaning
  efficiency
• Shorter 50cm collimators not excluded (at least
  in hard hit location)
• Space constraints must be maintained
• Beam pipe diameter must remain at 88mm
• 60mm maximum jaw gap with 5mm center variation
• Central stop roller jaw adjust mechanism seems
  incompatible with 60mm gap, plus need to
  understand impact of having device in beam median
  plane
• Relatively simply geometry used to date in energy
  deposition studies (at SLAC) must be improved to
  true maximum heat load is understood
• Tests/simulations to estimate extent of damage in
  asy. beam abort should continue

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Next Steps of Phase II Project

• CERN will xfer latest version of tracking code
  with absorbers at 10sigma
• SLAC will investigate thinner layers of Cu on
  appropriate substrates as well as revisiting
  exotic metals (SuperInvar, ALbuMet, GumMetal)
• Eventual MARS benchmark of FLUKA results still
  deemed valuable
• Phase II Infrastructure requirements are being
  frozen
• They will be transmitted to SLAC
• Will look into possibility integrating CERN mover
  system with SLAC jaw assembly
• Politics
• Phase II collaboration meeting will be scheduled
  in June at SLAC with adequate CERN engineering
  and simulation expertise to ensure that RC1/RC2
  specs meet LHC requirements and constraints
• Later (September) would delay incorporation to
  design

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Phase II Collimator Budget Summary
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Phase II Collimator Labor Summary
Eric Doyle Lew Keller Yunhai Cai
Tom Markiewicz Tor Raubenheimer Andrei Seryi
Joe Frisch Engineer2 Postdoc1