Muon Collider & Neutrino Factory
Studies
R B Palmer
MSU
1/27/05
Design Studies
• 95-98: Muon Collider
Much smaller than Linear Collider
Hard Problem - Only conceptual studies done
• 99-04: Neutrino Factories
Similar technologies
Only way to study leptonic CP violation if sin2(2θ13) < 0.01
Detailed Studies including cost and performance
• 05–:
Returning to Collider
Technology R&D
• Hg Target Experiments
• Cooling Components and MICE Experiment
• 200 MHz SC RF, and FFAG Studies
1
Collaborators
• US Collaboration > 100 members
BNL, Cornell, Fermi, LBNL, US Universities (including MSU)
– 2 Spokespersons: S. Geer, Bob Palmer
– Project manager: Mike Zisman
– MCOG Steve Holmes Jim Siegrist, Tom Kirk
– MUTAC Helen Edwards chair
• European Groups
CERN, RAL (UK), INFN (Italy), Universities
• Japanese Groups
KEK, Osaka, other Universities
• Russia
BINP (including Skrinski, who started all this)
2
MUON COLLIDER
• Energy advantage over p’s (same as for e+ e- Linear Collider)
• Suppressed Synchrotron Radiation (∝ γ 4 ∝ m−4 )
– Circular
∗ Smaller because acceleration over many turns
∗ ≈ 1000 turns cf 1 collison for Linear Collider
– no ”beamstrahlung”
∗ dE/E ll 1% eg for Higgs mass determination
(cf 30% for 3 TeV Linear)
∗ allows larger Nµ per bunch (Helps Luminisity)
– larger spot size & emittance (For same Luminosity)
∗ Easier Final Focus Tolerances
• Direct Higgs Production
– µ+ µ− → h, A, H (σ ∝ m2)
3
But: µ’s in diffuse phase space and µ’s Decay
• Requires Efficient µ Production
– 20 T Solenoid to capture π’s
– RF Phase Rotation to reduce dE/E
• Requires Rapid Cooling (Beam size reduction)
– ionization cooling certain
– study optical and other exotics
• Requires Rapid Acceleration
– Recirculating Linear Acceleration (RLA) or FFAG
• Must Shield Ring Magnets from Muon Decay Electrons
– 3-6 cm Tungsten Shield
• Must Shield Detector from Decay Electron Background
– Loss of Forward Cone
• Must be Deep to Avoid Serious Neutrino Radiation
– Limits Energy to 3-10 TeV
4
Neutrino Radiation Limits Maximum Energy
Earth
?
~
ν’s
Ring
6
~
ν’s
depth
• Radiation ∝ E 3/length2 ∝ E 3/depth
• Use: 1/10 Federal limit = 10 mR/year
• Negligible problem at 1.5 TeV
• E = 3 TeV ok at 300 m depth
– ≈ 10 mR/year
• E > 3 TeV Requires:
– Beam wobbles, and/or
– Special Locations (eg an island), and/or
– Better Cooling (Optical Stochastic?)
5
Schematic of Muon Collider (not to scale)
Injection in both directions in all rings (not shown)
Proton driver
Drift
Bunch
Rotate
Target & Capture
Phase Rotate (Reduces dp/p)
Cool
(Reduce Emittance by 1000,000)
Linac
FFAG/RLA
FFAG/RLA
Acceleration
(.2 GeV - 1.5 T)
FFAG/RLA
Synchrotron
Collider Ring
6
(High Ave, Bending Field)
3 TeV Muon Collider (drawn to scale)
1.5 TeV acc
Collider
FNAL Site
p source
1 km
+
BNL Site
7
+
Compare sizes for 3 TeV Physics
5T 25+25 TeV pp
(≈ 3 TeV)
FNAL
14 TeV LHC
pp (1.5 TeV)
CLIC ee (3 TeV)
MuMu (3 TeV)
BNL
10 km
8
NEUTRINO FACTORY
• Uses similar technologies as Collider, but
• Simpler than Collider
Flux Required for the Physics
9
Neutrino Factory Studies in the US
• 99-00
Neutrino Factory Feasibility Study I
– Emphasized Feasibility, with complete Simulation
– ”Entry Level Performance” (≈ 0.2 1020 µ/yearsec at 1 MW)
• 01-02
Neutrino Factory Feasibility Study II
– Emphasized Performance
– Similar Cost
– 6 times Performance of Study I
• 03-04
Neutrino Factory Feasibility Study IIa
– Emphasized Cost Reduction
– Part of APS Neutrino Study (September 04)
– 61 % cost of Study II
– Same flux, both charges: 12 times Performance of Study I
– Meets original Physics Requirement
– Small further cost reduction possible: publication this year
10
Comparison: Conventional vs. Factory
• Conventional:
p + C → πHigh E → µ̄ + νµ
• Neutrino
Factories:
p+Hg → πLow E → µLow E → µHigh E → e + νµ + ν¯e
For θ13 or CP
• Conventional:
– ID
– Detector:
– Background:
νµ
→
νe
e shower and no µ
water or light plates
νe’s and NC π o’s
≈ 10−2
→ νµ
wrong sign µ
• Neutrino Factories:
νe
– ID
– Detector:
Thin magnetized Fe plates
– Background:
Misidentified sign
11
or Liquid A
≈ 10−4
Looking for CP violation
ν̄/ν
Errors in CP angle δ
12
Ambiguities
Resolution of Ambiguities
Requires two distances
13
Schematic of Neutrino Factory Study IIa
Proton driver
Target & Capture
Drift
Bunch
Rotate
Phase Rotate
Cool (factor 1-10)
10 %
17 %
21 %
Linac
Approx 1 B$
RLA
Acceleration
42 %
Storage Ring
9%
FFAG 1
FFAG 2
• Very similar to front end of Collider (but easier)
• Technologies for Factory also apply to Collider
14
TECHNOLOGIES for Factory or Collider
1) Target and Capture
• Liquid mercury Jet ’destroyed’ on every pulse
• 20 T Solenoid captures all low momentum pions
• Field subsequently tapers down to approx 2 T
• Target tilted to maximize extraction of pions
15
BNL Target Experiment E951
• Single pulse 4 Tp
But density equiv to 1 MW
• Non-Explosive Dispersion good
• But 4 MW Nu-Factory requires:
32 Tp/bunch
CERN Proposed Experiment P186
• More intensity
32 Tp as required for 4 MW
• 15 T pulsed Magnet near completion
16
2) Phase Rotation
(Reduce dp/p prior to Cooling)
Neuffer’s Bunched Beam Rotation with 200 MHz RF
dE
Drift
RF Buncher
RF
dt
• RF frequency must vary along bunching channel
Because High mom. bunches move faster than lower
17
Simulation of Phase Rotation
Momentum (GeV/c)
110.7 m End
of drift
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pp p p p
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pp pppppppppppppppppppppp ppppppppppp ppp pp p p
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p ppppppppppppppppppppppppppppppppp ppppppppp pppp pp p
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pppp ppp p pppp pp ppp p p p p
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p pp p pppppppppppppp ppppppppppppppppppppp pppp pp ppp pppppp pppppppp p
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p p pp p p p
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p p ppp pppppppppppppppppppppppp ppppppppppppppppp ppppp pp p p p p p p p
p
p
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p p p pppppppppppppp ppppppppppppppppppppp pp pppppppppppp pp ppppp pppp p ppp ppp
p pp pp pppppppppppppp p ppppppppppp ppp p pp p ppp p p pp p
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p p pp p p p p pppppppppp p ppp p p p p
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p p p pp ppppppp ppppppppppppppppppppppppppppp pp ppppppppppppppppppppppp pp p p pppp pppp p
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p p p pp pppp ppppppppppppppppppppppppppppppppppp pp ppp ppppppppp p
p p p ppp p pppppp p pppppp pp ppp pp p pp
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p p
p p
pp p pppppppp ppp pp pp ppp p p
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p pp p p p
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ppppppp pppp ppppp pp pppp ppp ppppppp pppppp pp ppp p p
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p
p
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ppppp pppp p pp ppppp pp pppppp ppp ppp p ppp p ppp p p pp p
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p p p p p
p
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ppppp pppppppp ppppppppp pppppp p ppppp p ppppppp ppppp pp p pppp p p p p
pp pp pppp p p p ppp pp pp p pp p p p p p p p
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p p p pp p pp pp ppp p pppp p ppppp p p p p pppp pp ppppp pp p
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pp p ppp pp pp p pppppp pppppppp p pppppp ppppppp p ppppp pppp ppp ppppp p pppp p p p
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p p pp ppp p pp pppp p ppp p pp p ppppp pp pp p p p p pp p p
p pp ppp ppppp ppppppp ppppppp p ppppppp pppppppp p ppppppp p pppppppp p ppppp pp pppppp p p
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p ppp pp pp p ppp pppp pppppp p ppppp p pppppp ppppppppp ppppp
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p
p p pp p p p ppp p pp ppppppp p pppppp p
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p
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p pp
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161.7 m End
of bunch
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0.0
p p p p
ppp p pppp ppp pp p p
p
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p pp p p
p p pp p
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pp pp p pp p pp pp p p pp p ppp ppp pp p p
pp ppp ppppppp ppppppp ppppppppp pppp ppp pppppp pppp pppp pp ppp p pppp pp
···············
p
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pppppppp p ppppp p ppppppp p pppp ppppppp ppppp p pppp ppppp ppppp pppp ppppp pppppp pp
··········
p
p
p
p
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p
p p pp pp ppp p pp p p p ppp
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p
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pppp pppppp p pppppppp ppppppp pp ppppppp p pppppppp ppppp pppppp pppp pppppp pppp pppp ppppp pppp
················
p
p
p
p
···
ppp p ppppppp p ppppppp ppppppppp ppppp pppp pppppp p ppppppp ppppp p ppp ppppp ppppp pppppp ppp p
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p ppppppp pp p ppppp pppp pppp ppp ppp pp pp pp ppp ppp pp pp pp
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ppp p ppppp ppp ppp p p ppp p ppp pp p p p p pp p p ppp p
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p p p p p pp ppp p p
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p p pppp pppp p ppp ppppp ppp ppp ppp p p pp ppp
p p
p p pp
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p pp
pp p
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p
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p p pp p
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Momentum (GeV/c)
215.63 m···················End of rotate
0.6
0.4
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-50
0
ct
50
(m)
100
p
p p p p p pp
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p ppppp p p p pp ppp pp p pp
p
p
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pp ppp p pp pp ppp p p p pp ppp pppp p p p
··
ppppp pppp pppppp ppp p ppp pppp pppppp ppp ppppp ppp pppppp ppppp p
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pppp ppp p pp p p p pp p p p p p pp pp pp pp p p
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p ppp p p p pp p p p p p p p pp ppp pp p pp p pp p p p
··
p p pppppp p ppp pp pppppp ppppp pppppp pppppp ppppppp ppppp pppp ppp p ppp pppp p pppp
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p ppppp p p pp ppp p p p p pp p ppp pp p p pp p pp p p p p
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pp pppppp pppppppp ppppppppp pppp p pppp ppppppppp ppppp ppp pp ppppppp ppp p pppp pppp p ppp
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p pppp ppp p ppppppppp pp p ppp p pp pppp ppp ppp ppp p pppp ppppp pp
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pppp pp p pp p p pppp p pppp pp p p pp pppp ppp
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pp ppp p p ppp p ppp p p p p ppp p p p p
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pppp p pppp p pp pp pp p p p p
p
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265.9 m······ 50 m of cooling
-50
18
0
ct
50
(m)
100
3) Ionization Cooling
Electron, synchrotron, and stochastic cooling all too slow
• TRANSVERSE
– Competes with
Coulomb Scattering
– Best with Hydrogen
– and Strong Focus
p less
*p⊥ less
Material
:
p restored
p⊥ still less
Acceleration
• dE/E Reduced by Emit Exchange (Not needed for Factory)
– Competes with
Straggling
– Best with strong RF
→large dp/p
– Also works with
material in bend
High dp/p
Low n
Low dp/p
High n
-
BB
B
B
B
B
B
B
Material Magnet
19
Study IIa Cooling Channel
200 MHz RF
16 MV/m
radii
(m)
0.6
107
A/mm2
SC Coil
0.4
0.2
0.0
0.0
21 cm radius
1 cm LiH
or 1.5 cm Li
0.5
length
1.0
(m)
1.5
• ≤ 200 MHz RF for required aperture
• LiH instead of Liquid Hydrogen (as in Study II)
• Simpler focus system than Study II (see MICE Exp. below)
20
Cooling Performance in Study IIa
emit (pi mm)
20
15
10
•
8.9
5
0
150
200
250
length
300
(m)
21
350
Cooling with Emittance Exchange in a Ring
• Bending and wedge absorbers: Cooling also in longitudinal
• Many turns gives more cooling at lower cost
• Needed for a Muon Collider
• e.g RFOFO Ring
Now fully simulated
Injection/Extraction
Vertical Kicker
Alternating 3T Solenoids
Tilted for Bending By
201 MHz rf 12 MV/m
Hydrogen Absorbers
33 m Circ
• 6D emittance down by 300 (cf 1000,000 req for Collider)
22
R&D on Ionization Cooling Components
MUCOOL Collab Lead by Fermilab (A. Bross)
• Design, Build, Absorbers
• Design, Build, and Test Absorber Windows
• High Gradient RF Studies at 805 MHz
(Lab G FNAL)
• Design & Start Const. of 201 MHz Cavities
• Experiment with High Pressure Hydrogen
• Test area at FNAL
23
STTR
MUON IONIZATION COOLING EXPERIMENT
(MICE)
• Solid Design based on Study-2 channel
(Similar components to RFOFO cooling ring)
• International Collaboration: (US, Europe, Japan)
• Funding proposal sent to NSF,
(& in Europe & Japan)
• Proposal has Scientific Approval at RAL
24
4) R&D ON ACCELERATION
SC Cavity work for Acceleration (Cornell NSF)
• Built new test pit
• Design, build, and test 201 MHz SC cavities
11 MV/m achieved
limited by drop in Q c.f. FS2 spec = 16 MV/m
• Cavity returned to CERN for re-coating
25
ACCELERATION
• Must be fast: Muon lifetime=2 micro sec
• Synchrotron much too slow Except above 500 GeV for collider
• Use initial SC Linac
• Then Recirculating Linear Collider (RLA)
Dog-bone and Racetrack RLA’s, with same number of passes
through the Linac, have:
– slightly less total arc length
– much easier switch-yards
• Followed by FFAG’s (see below)
26
Scaling FFAG MURA & KEK (Japan)
p ∝ rn+1
drift for rf
bend outward
B∝
rn
bend inward
Low Momentum
Mid Momentum
High Momentum
POP FFAG at KEK
• Eliminates multiple arcs of RLA
• Allows more turns → less RF
• ∆p limited only by aperture
but only 1:2 for Japan 20 GeV
• Tune independent of momentum
i.e. Chromaticity=0
BUT
• Large magnet apertures
• Non-isochronous
→ Low Frequency RF
→ Non-superconducting RF
• Studies in Collaboration with Japan
2-3 Workshops per year
27
Non-Scaling FFAG
(Proposed by Carol Johnstone)
Combined function strongly focusing lattices without sextupoles
e.g. from Dejan Trbojevic
• Orbits are not similar, as in scaling
• They are closer together than in scaling
→ smaller apertures
→ more isochronous
28
More Isochronous than Scaling Allows use of SC RF
Design can be isochronous at center of momentum range:
1.25
Scaling (10-20)
dct/turn (m)
1.00
0.75
0.50
Non-scaling (10-20)
0.25
0.00
10.0
12.5
15.0
Momentum (GeV)
17.5
20.0
• Less path length difference for same energy range
• Non-monotonic
• Allows 200 MHz (vs. 25 MHz for scaling)
29
But huge chromaticity
→ Tunes cross many integer resonances (right scale)
But if
1. All cells essentially identical
2. Reasonably small magnet errors
3. Rapid acceleration
Initial simulations indicate negligible emittance growth
30
Conclusion
• Muon Collider
– Interesting for physics & Smaller than Linear Collider
– Difficult technically
– Neutrino Radiation limits Maximum Energy
– Now returning to its study
• Neutrino Factory
– If θ13 < 10−2 Factory is only hope to see CP
– If θ13 > 10−2 Factory perhaps not needed
– Will not know for 5-10 years
– Neutrino Factory Design in good shape
• Sound R&D Program in Progress
– Hg Jet Target for 4 MW (CERN Exp)
– Cooling Components (MUCOOL)
– SC RF at 200 MHz (Cornell)
– Cooling Experiment (MICE)
• Interesting Spin-Offs: Hg Target, Non-Scaling FFAG’s
• US Funding a problem for MICE
31