muon cooling r&d for the muon collider...muon collider design progress • muon collider designs...

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

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+


PRSTAB 2002

From Snowmass 96

Muon Collider - Motivation


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


• 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



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


Difficult in e+e- machinewith equivalent R ≈ 1%

Muon Collider Design

Emphasis on Cooling

Muon Collider Facility


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


Muon Ionization Cooling

Muon Ionization Cooling - Transverse

• 2D Transverse Cooling

and• Figure of merit: M=LRdEμ/dsM2 (4D cooling) for different absorbers


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


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


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


805 MHz Imaging


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


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


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


The VHFSMC Collaboration


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)


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))


A Muon Collider Cooling Scenario


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!


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)


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


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


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


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.


“Aspirational” MC Timeline


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


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


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


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

muon cooling r&d for the muon collider...muon collider design progress • muon collider designs...

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