Transcript Rotatable Collimators as a Possible US Contribution

US LHC Accelerator Research Program
BNL - FNAL- LBNL - SLAC
Rotatable Collimators
as a Possible US Contribution
to the LHC Luminosity Upgrade Project
24 April 2008
LARP CM#10
Tom Markiewicz/SLAC
beam
beam
Vision
DOE/LARP management perception is
that rotatable copper collimators are
relatively simple mechanical devices
that could be offered as a low risk
component of a US LHC Luminosity
Upgrade Project, offsetting risk of not
delivering Nb3Sn magnets, their main
interest.
LARP CM#10 - 24 April 2008
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Rotatable Collimator CP Proposal - T. Markiewicz
The Problem
Suggesting that the US manufactures 36 of these devices for the 30 reserved
Phase II secondary collimator lattice slots (plus 6 spares)
• Soft peddles fact that
– 1st single jaw has only now been brazed and still needs some weeks of
work before thermal-mechanical tests can begin
– SLAC has not begun, the “almost” fully defined, process of building the 1st
full beam testable double jaw collimator
• Ignores the CERN collimation “White Paper” plan calling for construction and
mechanical, vacuum & beam testing of three “complementary” designs that can
bring LHC luminosity from 1034 to 1035 before a production decision is made
– The Cu secondary RCs do not give x10 improvement in luminosity
– Destructive testing of the by-design damageable Copper may be prove
extensive enough to remove RC from consideration
• Does not address adequately the quality control issues seen in CERN’s Phase I
collimator production nor has there yet been any talk or agreement with CERN
on interface, installation, or engineering support issues.
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Rotatable Collimator CP Proposal - T. Markiewicz
My Opinion
LARP, through SLAC, is participating fully in the Phase II Collimation
project as outlined in the CERN “White Paper” plan and any action on
LARP’s part that looks, as this does, like it is circumventing the agreed
to schedule damages our relationship with our colleagues and is
doomed to failure.
If, after the R&D process concludes in October 2010, a decision is made
to produce some number of rotatable copper collimators, SLAC is
ready to participate.
This exercise should only be taken at the “CD-0” level: mission need and
ballpark cost estimate, and is hopefully, laying the bureaucratic
groundwork for eventual US participation in construction of collimators
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Rotatable Collimator CP Proposal - T. Markiewicz
References
Executive Summary
Second Phase LHC Collimators
R. Assmann
2007-04
Description Phase 2 Collimator Project
R. Assmann
2007-07-02
Collimation Issues for the Two LHC+ Scenarios and Future Plans
R. Assmann
Beam’07
2007-10-01
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Rotatable Collimator CP Proposal - T. Markiewicz
White Paper Plan
1. The R&D and prototyping of at least three different concepts for
advanced collimation designs, each addressing different possible
limitations to LHC luminosity.
2. Operational experience of the LHC with the Phase I collimation
system to understand the nature of any luminosity limit and the best
ways to ameliorate deleterious effects with already installed systems.
3. Testing of prototypes at CERN to their technological limits before any
installation in the LHC
4. Installation and testing of qualified Phase II prototypes in the LHC
during the second full year of LHC operation with a decision on phase
II design and production, which may require more than one
technology, at the end of the year.
5. Production of the collimators during years 3-4 of LHC operation,
installation during regularly scheduled shutdowns and use beginning
with year 5 of LHC operation.
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Rotatable Collimator CP Proposal - T. Markiewicz
White Paper Schedule
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Rotatable Collimator CP Proposal - T. Markiewicz
CERN Phase II R&D Budget
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CERN Pre-Production Manpower vs. Time
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Rotatable Collimator CP Proposal - T. Markiewicz
Production Estimated at 8M CHF
Table 1: Cost breakdown for the various work packages that are required for the phase 2 collimation system. Possible
and committed external contributions are listed as well. It is noted that possible FP7 contributions will only be known
at the end of 2007.
Work Package
External
contributor
Value of
contribution
[CHF]
CERN cost
after possible
FP7
contribution
FP7
1.2M
1.7M
LARP (US)
5.0M
-
CERN cost
[CHF]
CERN R&D and prototyping
2.9M
LARP R&D and prototyping
-
CERN 450 GeV beam test stand
1.7M
FP7
0.85M
0.85M
Test program and analysis
0.5M
FP7
0.25M
0.25M
Production & installation
8.0M
-
-
8.0M
Total
13.1M
5.0M - 7.3M
10.8M
Sub-total 2008-2010 (without
production and installation)
5.1M
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Rotatable Collimator CP Proposal - T. Markiewicz
NLC Consumable Collimator
rotatable jaws – 500 to 1000 hits
6.0
Note short high-Z material.
< 10 W per jaw
=>radiative cooling!
Aperture control
mechanism – 5mm
accuracy & stability
Alignment BPMs
upbeam & down
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Movers align chamber to
beam based on BPMs
Rotatable Collimator CP Proposal - T. Markiewicz
LHC Phase II Base Concept
physical constraints
current jaw design
20 facets
• beam spacing: geometrical constraint
• Length available 1.47 m flange - flange
Glidcop
Cu
Mo
• Jaw translation mechanism and
collimator support base: LHC Phase I
Cu coolant supply
tubes twist to
allow jaw rotation
• >10 kW per jaw Steady State heat
dissipation (material dependent)
Helical cooling channels
25mm below surface
Hub area
Cantilever Mo shaft
@ both ends
beam
beam
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Rotatable Collimator CP Proposal - T. Markiewicz
Cu Jaw-Cu Hub-Mo Shaft Design
2mm shaft-jaw gap gives x5
improvement in thermal deformation
over solid shaft-jaw design
1260 um  236 um (60kW/jaw, t=12min)
426 um  84 um (12kW/jaw, t=60min)
Rather than Cu, Moly shaft improves
Gravity sag x3:
200 um  67 um
Thermal bulge 30%:
339 um  236 um
LARP CM#10 - 24 April 2008
Molybdenum
Shaft
Copper Mandrel
Copper tubing wound in groove
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Rotatable Collimator CP Proposal - T. Markiewicz
Brazing Each Moly Shaft End to a Central Copper Hub
After much R&D, developed
method to braze Molybdenum
to Copper for inner shaft
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Three Braze Cycles
Three main brazing steps.
Brazing materials set to melt at gradually lower temperature.
1.) Braze each shaft end to a central half-hub
2.) In one go:
Braze shaft hubs to Mandrel
25% Gold, 75% Copper
Braze copper cooling coil to Mandrel
35% Gold, 65% Copper
3.) Braze jaw quadrants to mandrel surface
50% Gold, 50% Copper
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Inserting Molybdenum Shaft Ends into
Mandrel then Wind Coil Around Mandrel
with Ends of Coil Protruding Out Each End
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Braze Step#1 Shaft Assembly & Coil to Mandrel
On support stand and ready for
insertion in baking oven
Carbon block used to hold
thermally expanding copper
against central hub and shaft
(moly and copper)
Next time may use carbon block
full length of mandrel
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Filling Coil-Mandrel Keystone Gaps
Three brazing cycles needed before coilmandrel ‘keystone’ gaps filled adequately
On 3rd cycle excess braze material attaches
support stand to mandrel, which warps
Pix of 2nd braze cycle
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Recovery after Excess Braze Material Attaches
Mandrel & Shaft to Inox & Inconel Braze Supports
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Measure & Machine Quadrants to
Mandrel. Assemble & Braze
Using 50-50 Au-Cu brazing
material ($$)
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Results of Jaw Brazing 22 April 2008
Looks good!
QA measurements will be done 23-Apr
Next step is machine flat facets and
grooves for heater tests and
thermocouple holes.
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Internally actuated drive and jaw mount for
rotating after beam abort damages surface
Completed 27 May 2007
Universal Joint Drive Axle
Assembly
•Thermal expansion
•Gravity sag
•Differential transverse
displacement
LARP CM#10 - 24 April 2008
Rotation drive
with “Geneva
Mechanism”
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Rotatable Collimator CP Proposal - T. Markiewicz
Up Beam end detail beam side view of Current Idea for
RF Transition to Beam Pipe
LCR meter, Contact Resistance, Trapped Mode Calculations
Spiral style backing springs reside inside
“Sheath” (sheath not shown)
Thin sheet metal RF “Curtain”
Round to Square Transition
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Summary of Mechanical Design
Complete braze procedure developed, but want to look at…
• Full length graphite choke when brazing coil to mandrel
• Keystone reduction
– Blowing up coil with compressed air
– Wedging copper between mandrel between coil slots to drive it
towards coil
• Using 360 quarter length jaws with braze wire rings cut on ID rather
than 90 quarter length jaws
• Anything to reduce number surface prep requirements for brazes
Support & rotation done
Well developed ideas on RF features that (in principle) are far from
critical path
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Rotatable Collimator CP Proposal - T. Markiewicz
Performance Risks
• Will thermal-mechanical testing of the first jaw validate the shaft-hubjaw design that should limit maximum jaw deflection into the beam
area to 230 microns for 10 second bursts of 60kW beam absorption
• Will the mechanical accuracy of the device be adequate (40 um)
• Will the basic jaw-adjustment and jaw-rotation work as planned
• Will the effective impedance and RF characteristics of the jaw and the
transition to the vacuum tank aperture be adequate
• Will the device vacuum be sufficiently low
• When damaged by an aborted beam, will the extent of damage be
sufficiently localized to allow rotation to a clean surface, as planned
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Exact Nature & Extent of Damaged Region
Thin Cu sample in FFTB electron beam at SLAC
Hole = Beam Size
2000um 500 kW 20 GeV e- beam
hitting a 30cm Cu block a few mm
from edge for 1.3 sec (0.65 MJ)
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FNAL Collimator with .5 MJ
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Rotatable Collimator CP Proposal - T. Markiewicz
Accident Case: Permanent deformation AND Molten copper
Jaw facets
2.5mm x 2.5mm
elements
Tmax = 57 e3
3.3mm
Shaft
5mm
melt
Shower max – extent of melted
zone
Cooling
tubes
Case: beam abort system fires asynchronously, 8 full intensity bunches into jaw
Model: - increased resolution 3-D ANSYS & FLUKA models
- Thermal heating/cooling analysis followed by quasi-static stress analysis
- Jaw ends constrained in z during 200 ns, released for 60 sec cool-down
- 0.27 MJ deposited in 200 ns
- Molten material removed from model after 200 ns
Result: - 57e3 peak temperature (ultra fine model)
- 54 mm permanent deformation (concave)
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Braze Test #3: Vacuum tests: No improvement
•3rd Jaw Braze Test Assembly has been vacuum
baked at 300 degrees C for 32 hours. Results in
slightly lower pressure.
•Inclusion of longitudinal grooves in the inner length
of jaws for better outgasing
•Test Chamber setup similar to previous test.
LARP CM#10 - 24 April 2008
Old
New
Baseline
3.2E-9 Torr
2.4E-9 Torr??
w/ jaw assy.
3.7E-9 Torr
3.4E-9 Torr
Presumed jaw
assy. pressure
4.5E-10 Torr
10E-10 Torr??
LHC
requirement
7.5E-10 Torr
7.5E-10 Torr
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Efficiency Studies
Chiara Bracco (CERN)
Performance (Efficiency) of collimation system depends on # particles getting into the cold
aperture (>10s) per unit length as a function of location around the LHC given the optics model
AND an aperture model
500E6 Halo protons tracked over 200 turns in 10cm steps by Bracco et al to get loss maps for
each magnet
Beam intensity limitations are due to losses in the dispersion suppressor above the quench limit.
Phase I Beam Intensity Limit
Phase I to II Global Improvement
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Intensity Limit at “Dispersion Suppressor” with
Phase II at Nominal Collimation Settings
Losses due to particles that hit primaries but
that do not see the secondaries
While philosophy is every bit helps (take the x3.6) “ultimate”
luminosity may require different collimation settings or
completely different collimators (crystals as primaries?)
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Graphite -> Copper
Switching to copper
will decrease the
imaginary part of
the impedance but
increase the real
part
This is either good or
bad depending on
how you want to
damp beam
instabilities
(Landau Damping
versus Feedback)
So, impedance still
dominated by
copper collimators
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Unscrubbed Unit Cost Based on work done to date: $250k
1 Complete Collimator (Set of 2 Jaws w 4 drive motors)
hardware fab inside shops
4 motor drive assys incl motors & lvdts
2 sets of ceramic geneva wheels
4 Moly Half Shafts/integral collets
2 Moly Gear blank/u-joints
2 Moly u-joints
4 End Curtain Assys
winding 2 Coils onto Mandrels
Misc shafts and brg retainers
cleaning copper cooling coil
assembly of 2 UB end support
assembly of 2 DB end support
assembly of 2 Collimators in Tank
mounting of stages to tank
vacuum qualification tests
functional tests
M&S
0
400
12000
1000
1000
400
copper cooling coil material
14800
2000
fab outside shops
2 Mandrels
2 Copper Hubs
50000
2000
fte
Man-weeeks Rate type/Salary type cost
Mech Fab
1
0
Mech Fab
1
0
4 Mech Fab
1
14336
4 Mech Fab
1
14336
2 Mech Fab
1
7168
2 Mech Fab
1
7168
1 Mech Fab
1
3584
2 Mech Fab
1
7168
1 Mech Fab
1
3584
0.2 Plating
1
1125.2
1 Mech Fab
1
3584
1 Mech Fab
1
3584
2 Mech Fab
1
7168
0.5 Mech Fab
1
1792
3 Mech Fab
1
10752
0
ME
1
0
23.7
85349.2
type
fab/assy in-house
parts fab out-house
braze
plating
1
2 M&S
3
3584
5626
200000
89600
2
2
2
2
tank
2 Mounting Arms
1 Coupling Plate Assy
2 upbeam end support
2 downbeam end support
hardware fab outside shops
4 Transition Ends
4 RF Spring and Ball Bearing Ring
4 Long RF Spring Sheath Assys
4 Short RF Spring Sheath Assys
4 Bellows and bellows weldments
2 Gear hobbing
e-beam welding of tank incl transportation
12000
4400
5250
15000
10000
2
2
2
2
2
2
2
2
2
2
2
2
2
7000
3000
8000
4000
10000
4000
5000
139650
cleaning for brazing
Assembly and brazing steps
assemble for brazing preparations
brazing preparations of Shafts and Mandrels
braze
measure modify and assemble for brazing preparations of Jaws
brazing preparations Jaws
braze
machine grooves for wire alloy for Jaw brazing
0.1
1 Plating
ME
ME
ME
ME
ME
ME
ME
ME
3
3
3
3
3
3
3
3
3
5626
25626 total
36 collimator assemblies
fiducialize for each orientation & log for future
travelers and final documentation package
Mechanical engineering support
Manufacturing Coordination
Technician support for assembly
154450
LARP CM#10 - 24 April 2008
265425.2 cross check total
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Rotatable Collimator CP Proposal - T. Markiewicz
Project Cost “x2 Estimate”
Unit Cost for Tank, 2 jaws, rotation & support, RF
Unit Cost for Rack & pinion, motors, LVDTs
$250k
$50k
These are probably underestimates:
Assembly, test & qualification at SLAC
36 units over 2 years
EDI&A
4 FTEs
$200k
6 FTE
Lab overhead
42%
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Project Schedule
Sure to be dominated by braze
operations and braze oven
cycles
72 jaws with 3 braze cycles
per jaw
– imply that while not
excluded 2 years of
production is aggressive
– 1 year construction
seems impossible
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