Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
Muon Cooling R&D for the Muon Collider
A 5 Year Plan for the USAlan BrossCOOL’09
Institute of Modern PhysicsLanzhou, China
2
Outline
My TalkWhy a Muon Collider? Inspirational
Physics motivation for and nature of possible future facilities based on ultra-high intensity muon beams
Muon Collider FundamentalsWhy Cooling is so critical
Outline of Conceptual Approaches to reach to required coolingWhat technologies are crucially central to making the above a reality. Technical R&D Overview Path to Realization
5 Year Plan EssentialsI hope to give you Overview of our activities but will have to leave out most technical details (See Snopok,Yonehara,Li,Ng)
http://www.cap.bnl.gov/mumu/https://mctf.fnal.gov/
Alan Bross COOL’09 IMP Lanzhou, China
Physics in Evolution
What we might do at a Muon Accelerator Facility
Alan Bross COOL’09 IMP Lanzhou, China 4
10 TeV3TeV
≈ 1TeV
+4TeV
0.5TeV
Alan Bross COOL’09 IMP Lanzhou, China 5
Evolution of a Physics Program
A μ source providing 1-2 X 1021
μ/yr supports a rich physics program:
1. Intense Low-energy muon physics (LFV)
μ e conversion experimentNeutrino Factory
Low Energy 4 GeVHigh Energy 25 GeV
Energy Frontier Muon Collider
1.5 - 4 TeV+
Alan Bross COOL’09 IMP Lanzhou, China 6
PRSTAB 2002
From Snowmass 96
Muon Collider - Motivation
Alan Bross COOL’09 IMP Lanzhou, China 7
Reach Multi-TeV Lepton-Lepton Collisions at High Luminosity
Muon Colliders may have special role for precision measurements.
Small ΔE beam spread –Precise energy scans
Small Footprint -Could Fit on Existing Laboratory Site
The Supersymmetric Particle Zoo
Alan Bross COOL’09 IMP Lanzhou, China 8
• Independent of actual supersymmetric mass scale and the reach of the ILC, the 2004 CLIC Study conclusions are still valid
u “A Multi-TeV machine is needed for extended coverage of the mass range
Snowmass Supersymmetric Benchmark
Alan Bross COOL’09 IMP Lanzhou, China 9
Alan Bross COOL’09 IMP Lanzhou, China 10
But the Physics Landscape has New Features since 2001
A typical sample “compressed” Higgs and superpartner mass spectrum with ΩDMh2 = 0.11An unfortunate feature, quite common to this scenario for dark matter, is that no visible superpartners would be within reach of a linear collider with √s = 500 GeV
Stephen Martinhep-ph/0703097
March, 2007
Strong(er?)Case for
considering Multi-TeV
Lepton Collider
Also New results frome+e- → ππ(γ) (TAU08)
Puts further pressure on Low-mass SS
MC Physics - Resolving degenerate Higgs
Alan Bross COOL’09 IMP Lanzhou, China 11
Difficult in e+e- machinewith equivalent R ≈ 1%
Muon Collider Design
Emphasis on Cooling
Muon Collider Facility
Alan Bross COOL’09 IMP Lanzhou, China 13
LEMC
*Probably favored at this time& used in following slides
MC – Design Options
From the previous slide, you see that there are many options for the cooling
Why?Because, at present there are NO Solutions to the technical issues involved
Operation of RF in High (1-3T) Magnetic FieldOperation of Very High Field (50T) Magnets
Alan Bross COOL’09 IMP Lanzhou, China 14
Muon Ionization Cooling
Muon Ionization Cooling - Transverse
• 2D Transverse Cooling
and• Figure of merit: M=LRdEμ/dsM2 (4D cooling) for different absorbers
Alan Bross COOL’09 IMP Lanzhou, China 16
Absorber Accelerator Momentum loss is opposite to motion, p, px, py, ΔE decrease
Momentum gain is purely longitudinal
Large emittance
Small emittance
H2 is clearly Best -Neglecting Engineering Issues
Windows, Safety
Muon Collider Design Progress
• Muon Collider designs start with a NF front-end, but require a much more ambitious cooling channel (6D cooling ~ O(106) c.f. 4D cooling ~ O(100).
• In the last 5 years concepts for a complete end-to-end self con-sistent cooling scheme have been developed
Requires beyond state-of-art components: need to be developedHardware development and further simulations need to proceed together to inform choices between alternative technologies
• Key Areas of Technological developmentOperation of High-Gradient RF in a Magnetic Field (2-3T)High Field Magnets (up to 50T)
NFFRONTEND
17Alan Bross COOL’09 IMP Lanzhou, China
MuCool Component R&D and Cooling Experiment
Alan Bross COOL’09 IMP Lanzhou, China 18
MuCool201 MHz RF Testing
50 cm ∅ Be RF window
MuCoolLH2 Absorber
Body
• MuCoolu Component testing: RF, Absorbers, Solenoids
With High-Intensity Proton Beamu Uses Facility @Fermilab (MuCool Test Area –MTA)u Supports Muon Ionization Cooling Experiment (MICE)
MuCool Test Area
RF Test Program
MuCool has the primary responsibility to carry out the RF Test ProgramStudy the limits on Accelerating Gradient in NCRF cavities in magnetic fieldIt has been proposed that the behavior of RF systems in general can be accurately described (predicted) by universal curves
Electric Tensile Stresses are important in RF Breakdown eventsThis applies to all accelerating structuresFundamental Importance to both NF and MC – RF needed in
Muon capture, bunching, phase rotationMuon CoolingAcceleration
Arguably the single most critical Technical challenge for the NF & MC
19Alan Bross COOL’09 IMP Lanzhou, China
The Basic Problem – B Field Effect805 MHz Studies
• Data seem to follow universal curve
Max stable gradient degrades quickly with B field
• Re-measuredSame results
Grad
ient
in
MV/
m
Peak Magnetic Field in T at the Window
>2X Reduction @ required field
20Alan Bross COOL’09 IMP Lanzhou, China
805 MHz Imaging
21Alan Bross COOL’09 IMP Lanzhou, China
RF R&D – 201 MHz Cavity TestTreating NCRF cavities with SCRF processes
• The 201 MHz Cavity – 21 MV/m Gradient Achieved (Design –16MV/m)
Treated at TJNLAB with SCRF processes – Did Not Condition• But exhibited Gradient fall-off with applied B
1.4m
Design Gradient
22Alan Bross COOL’09 IMP Lanzhou, China
Facing the RF B Field Challenge
• Approaches to a SolutionReduce/eliminate field emission
Process cavities utilizing SCRF techniquesSurface coatings
Atomic Layer DepositionMaterial Studies
Non-Cu bodies (Al, Be?)Mitigate the effect of B field emission on breakdown
RF cavities filled with High-Pressure gas (H2)Utilize Paschen effect to stop breakdown
Magnetic InsulationEliminate magnetic focusing
Not Yet Tested
23Alan Bross COOL’09 IMP Lanzhou, China
High-Gradient RF Operation B Field
Promising indications @ a SolutionSCRF Processing techniques help
Reduce dark currentMore advanced techniques (Atomic-Layer-Deposition) may do more
Cavity material properties seem to be importantTiN helps
Coupled with SCRF processing may reduce FE even more
Mo, Be Coatings?Gas-filled cavities show promise
Operation with beam critical next test
24Alan Bross COOL’09 IMP Lanzhou, China
The VHFSMC Collaboration
25Alan Bross COOL’09 IMP Lanzhou, China
VHFSMC Goals
• The primary goal is to develop the Technology of High Temperature Superconductors for use in magnets at fields beyond those available for Nb based conductors.
• This supports the needs of the muon collider R&D as well as the NMR community (see National Academy COMAG report)
1. L ~ B solenoid2. L ~ B in collider ring3. HTS Conductors may be
Rad Hard. (BNL & CERN reports)
26Alan Bross COOL’09 IMP Lanzhou, China
Quick Overview of Bi 2212Why the excitement?
10
100
1000
10000
0 5 10 15 20 25 30 35 40 45
Applied Field (T)
J E (A
/mm
²)
YBCO Insert Tape (B|| Tape Plane)
YBCO Insert Tape (B⊥ Tape Plane)
MgB2 19Fil 24% Fill (HyperTech)
2212 OI-ST 28% Ceramic Filaments
NbTi LHC Production 38%SC (4.2 K)
Nb3Sn RRP Internal Sn (OI-ST)
Nb3Sn High Sn Bronze Cu:Non-Cu 0.3
YBCO B|| Tape
YYBBCCOO BB⊥⊥ TTaappee
2212
RRRRPP NNbb33SSnn
BBrroonnzzee NNbb33SSnn MgB2
NNbb--TTiiSSuuppeerrPPoowweerr ttaappee uusseedd iinn rreeccoorrdd bbrreeaakkiinngg NNHHMMFFLLiinnsseerrtt ccooiill 22000077
1188++11 MMggBB22//NNbb//CCuu//MMoonneell CCoouurrtteessyy MM.. TToommssiicc,, 22000077
427 filament strand with Ag alloy outer sheath tested at NHMFL
Maximal JE for entire LHC Nb-Ti strand production (CERN-T. Boutboul '07)
CCoommpplliieedd ffrroomm AASSCC''0022 aanndd IICCMMCC''0033 ppaappeerrss ((JJ.. PPaarrrreellll OOII--SSTT))
44554433 ffiillaammeenntt HHiigghh SSnnBBrroonnzzee--1166wwtt..%%SSnn--
00..33wwtt%%TTii ((MMiiyyaazzaakkii--MMTT1188--IIEEEEEE’’0044))
27Alan Bross COOL’09 IMP Lanzhou, China
A Muon Collider Cooling Scenario
Alan Bross COOL’09 IMP Lanzhou, China 28
Muon Ionization Cooling Experiment
29
Measure transverse (4D) Muon Ionization Cooling10% cooling – measure to 1% (10-3)
Single-Particle ExperimentBuild input & output emmittance from μ ensemble
Tracking Spectrometer
RFCavities
FocusCoils
Magneticshield
LiquidHydrogenAbsorbersFiber Tracker
SeeDerun Li’s
Talk
Guggenheim RFOFO - Simulations
RF
liquid H2
solenoid
SeeP. Snopok’s
Talk
Helical Cooling Channel
• Magnetic field is solenoid B0+ dipole + quad• System is filled with H2 gas, includes rf
cavities• Cools 6-D (large E means longer path length)• But, incorporating RF is Engineering challenge!
31Alan Bross COOL’09 IMP Lanzhou, China
SeeK. Yonehara’s
Talk
HCC Magnet Design & Prototyping
• Helical solenoid (HS): Smaller coils than in a “snake” design
Smaller peak fieldLower cost
• Field components in HS determined by geometry
Over constrainedCoil radius is not free parameter
• 4 Coil Demonstration ModelValidate mechanical structure and fabrication methodsStudy quench performance and margins, field quality, quench protectionUse SSC conductor
Outer bandage rings
Inner bobbin
Superconducting coils (one layer, hard bend wound)
32Alan Bross COOL’09 IMP Lanzhou, China
Final Cooling
• LH2 absorbers tested in MICE• 50 T Solenoids
Very recently the “National Very High Field Superconducting Magnet Collaboration” was formed
2 Year $4M program to study HTS conductor and cable
Alan Bross COOL’09 IMP Lanzhou, China 33
Initial Design of Liquid Li Lens
Lens assembly w/ current discs and the primary and secondary coils
Li D = 2.54 cm; L = 30.0 cm
Lithium Lens for Muon Final Cooling
Kevin Lee
More “Speculative” Approaches to Muon Cooling
R. Palmer’s ICOOL model
Muon Cooling With an Inverse Cyclotron
G4beamline model
θ1
θ2
r2
r1
Bz = 2 TBz = -0.5 T
raveave
rminmin
rmaxmax
Terry Hart
VORPAL 3D Simulations with space-chargeKevin Paul
36Alan Bross COOL’09 IMP Lanzhou, China
Particle RefrigeratorFrictional Cooling
• Frictional cooling has long been known to be capable of producing very low emittance beams
• The problem is that frictional cooling only works for very low energy particles, and its input acceptance is quite small in energy:
Antiprotons: KE < 50 keVMuons: KE < 10 keV
Key Idea:Make the particles climb a few Mega-Volt potential, stop,
and turn around into the frictional cooling channel. This increases the acceptance from a few keV to a few MeV.
• So the particles enter the device backwards; they come back out with the equilibrium kinetic energy of the frictional cooling channel regardless of their initial energy.
• Particles with different initial energies turn around at different places.
• The total potential determines the momentum (energy) acceptance.
Remember that 1/e transverse cooling occurs by losing andre-gaining the particle energy. That occurs every 2 or 3 foilsin the frictional channel.
Solenoid
μ− In(3-7 MeV)
μ− Out(6 keV)
…Resistor DividerGnd
HV Insulation First foil is at -2 MV, so outgoing μ− exit with 2 MeV kinetic energy.
Solenoid maintains transverse focusing.
μ− climb the potential, turn around, and come back out via the frictional channel.
10 m
20cm
1,400 thin carbon foils (25 nm), separated by 0.5 cm and 2.4 kV.
-5.5 MV
Device is cylindrically symmetric (except divider); diagram is not to scale.
Tom Roberts
Particle Refrigerator
38Alan Bross COOL’09 IMP Lanzhou, China
The Way Forward
Joint NFMCC and Fermilab MCTF 5 Year Proposal to DOE
Organization
•NFMCC (Neutrino Factory & Muon Collider Collab.)–National collaboration funded since 1999.–Pursues Neutrino Factory & Muon Collider R&D.–NF R&D pursued with international partners
•MCTF (Muon Collider Task Force)–Task Force established at Fermilab in 2006–Pursues Muon Collider R&D, utilizing FNAL assets and extends & complements the NFMCC program
•MCCC (Muon Collider Coordinating Committee)–Leadership of NFMCC (Bross, Kirk, Zisman) and MCTF (Geer, Shiltsev)–Co-ordinates NFMCC & MCTF plans to optimize the overall program … has worked well and resulted in a joint 5 year plan for future activities.
40Alan Bross COOL’09 IMP Lanzhou, China
“Aspirational” MC Timeline
Alan Bross COOL’09 IMP Lanzhou, China 41
Cooling R&D ProgramIn the 5 Year Plan
• PrecoolingTransverse cooling as in MICE (Study 2a)Helical precooler
• 6D CoolingGuggenheim Channel
“Tapering” channelHelical Cooling ChannelFOFO SnakeFinal Cooling
50T HTS Solenoids + LH2 absorbersPIC – REMEXLi Lens Channel
• In addition the following are neededCharge separation and recombinationLow energy bunch merging
Alan Bross COOL’09 IMP Lanzhou, China 42
FUNDING PROFILE
0
5000
10000
15000
20000
25000
30000
YEAR
FUN
DS
(K$)
M&SSWFTOTAL
PROPOSED EFFORT CONTRIBUTIONS
0
20
40
60
80
100
120
YEAR
EFF
OR
T (F
TE)
LBNLBNLFNALOTHERSUM
Muon Collider Technical Foundation after 5 Years
From Here to There
43Alan Bross COOL’09 IMP Lanzhou, China
Year 5
Closing Remarks
Road Map to the Future
We believe ~2012 will be a pivotal time in HEPLHC Physics ResultsNeutrino Data from Reactor and Accelerator ExperimentsMajor Studies for Frontier Lepton-Colliders Completed
ILC EDRCLIC CDR
In order for the Muon Collider to be a viable option at this time, the R&D in this 5 year plan is essential – Muon Cooling is Key
Not all issues will be addressed, but much progress can be made
Technology down-selection
45Alan Bross COOL’09 IMP Lanzhou, China
ENDAcknowledgments
I want to thank all my colleagues in the Neutrino Factory and Muon Collider Collaboration and the
Fermilab Muon Collider Task force for all the hard work and for the many conversations I have had
with them on this subject.In Particular I want to thank Bob Palmer, Steve,
Geer, Vladimir Shiltsev and Mike Zisman