International Design Study of aNeutrino Factory
J. Scott BergBrookhaven National Laboratory
IPAC 201027 May 2010
Neutrino Physics
❍ Neutrinos have mass❍ Mass and flavor eigenstates different❍ Mixing matrix angles θ12, θ23, θ13
❑ θ13 possibly zero, θ23 near 45◦
❍ CP-violating phase δ (irrelevant if θ13 zero)❍ Squared mass differences
❑ |∆m2
21| ≪ |∆m
2
31|
❑ Sign of ∆m2
31unknown
2
Neutrino Properties3
2
1
1
2
3
e µ τ
ma
ss
2
3
Long Baseline NeutrinoExperiments
❍ Accelerator: make neutrinos in flavor eigenstate❑ Mixture of mass eigenstates
❍ Neutrinos propagate to far detector❑ Each mass eigenstate has different phase
advance❑ Phase advance: square of mass
❍ Detector: detect flavor eigenstate❑ Detect corresponding lepton (e, µ)
4
Neutrino Factory Goals
❍ Create high-energy muon beam❍ Decay in ring, directed through earth to far
detector❍ Well-defined spectrum from muon decay
❑ µ− creates νµ and ν̄e❑ Distinguish by sign of detected leptons
✧ Need magnetized detector
5
Neutrino Factory vs.Superbeams
❍ Get results forsmallest θ13
❍ Better precisionfor mixingparameters
❑ Especiallyinteresting ifnearlysymmetric
10–5
10–4
10–3
10–2
10–1
True value of sin22θ13
0
0.2
0.4
0.6
0.8
1
Fra
ctio
no
fδ
CP
SPL
T2HK
WBB
NF
BB
GLoBES 2006
6
Neutrino Factory AcceleratorComplex
❍ High-power proton driver, protons hit❍ Target, producing pions decaying to muons❍ Front end, reshapes and intensifies beam❍ Acceleration, increase energy to 25 GeV❍ Decay ring, neutrinos produced decay toward
far detectors
7
Neutrino Factory AcceleratorComplex
12.6–25 GeV FFAG
3.6–12.6 GeV RLA
0.9–3.6 GeV
RLA
Linac to
0.9 GeV Muon Storage Ring
Muon Storage Ring
Linac optionFFAG/synchrotron option
Proton Driver
Neutrino Beam
Neutrino Beam
Hg Target
Buncher
Bunch Rotation
Cooling
1.5 km
755 m
1.1
km
8
International Design Study
❍ Goal: reference design report by end 2012❑ Basis for request to start project❑ Costs at 30% level
❍ Interim design report by end 2010❑ Move from design to engineering❑ Designs for all systems❑ Cost estimates at 50% level
❍ Focus on baseline: one design!
9
Baseline Parameters
❍ 25 GeV muon beam, both signs❍ Detectors at two distances
❑ 3000–5000 km❑ 7000–8000 km
❍ 5× 1020 muon decays per year per baseline
❍ Muon beam divergence of 0.1/γ
10
High-Power Proton Driver
❍ Supply protons to target to produce pions❍ Basic specifications:
❑ 4 MW proton beam power❑ Proton kinetic energy 5-15 GeV❑ RMS bunch length 1–3 ns❑ 50 Hz repetition rate❑ Three bunches, extracted up to 80 µs apart
11
Muon Capture vs.Proton Energy
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 10 20 30 40 50 60 70 80 90 100
Mes
ons/
prot
ons/
GeV
Proton Kinetic Energy, GeV
12
Muon Capture vs.Proton Bunch Length
13
Proton Bunch Structure
1–3 ns
> 160 µs
20 ms
14
Proton Driver Plans
❍ Will be upgrade to existing facility❍ Important to understand contribution to cost of
neutrino factory❍ Individual laboratories will contribute
❑ Plan to upgrade to neutrino factoryrequirements
❑ Corresponding cost estimate
15
Target
❍ Baseline is liquid mercury jet❑ Avoid target damage
❍ Target in 20 T field: pion capture❍ Demonstrated in MERIT experiment
❑ Proton beam pulses comparable to neutrinofactory
❑ Two bunches in rapid succession: no loss inproduction for second with spacing 350 µs orless
16
Mercury Jet Target Station
IronPlug
ProtonBeam
NozzleTube
SC-1
SC-2 SC-3 SC-4SC-5
Window
MercuryDrains
MercuryPool
Water-cooledTungsten ShieldMercury
Jet
ResistiveMagnets
SplashMitigator
17
Target Plans
❍ Engineering of target station and components❍ Jet nozzle: improve jet quality❍ Ensure sufficient shielding of superconducting
magnets❍ Fluid dynamics/engineering of Hg pool
❑ Acts as beam dump❑ Return Hg to loop
18
Mercury Pool Dynamics
19
Front End
❍ Pions (thus muons) start with large energyspread: reduce
❑ “Neuffer” phase rotation✧ Uses high-frequency RF✧ Does both signs
❑ Create 200 MHz bunch train❍ Reduce transverse beam size
❑ Ionization cooling
20
Pion Spectrum
0
50
100
150
200
250
300
0 0.2 0.4 0.6 0.8 1
Mes
ons/
10M
eV/G
eV
Kinetic Energy, GeV
10GeV+50GeV+100GeV Beam-Mesons(Positives+Negatives) at 50m
10GeV50GeV
100GeV
21
Phase Rotation
ct
∆E
Drift rf-Buncher rf-Rotation
22
RF in Magnetic Field
❍ RF cavities in magnetic field❑ Large angular and energy acceptances
❍ Experiments: gradient reduced in magnetic field❍ Don’t have complete picture yet❍ Ongoing experiments
❑ Change magnetic field orientation w.r.t.surface
❑ Gas-filled RF cavities❑ Test different surface materials
23
Ionization Cooling Lattice
24
Gradient vs. Magnetic Field
0 1 2 3 4Solenoid Magnetic Field (T)
0
5
10
15
20
25
30
35
40
45G
radi
ent (
MV
/m)
25
Mitigation Strategies
❍ Reduce fields on cavities❑ Increase distance to magnets❑ Add bucking coils❑ Add shielding to solenoids
❍ Magnetically insulated lattice: high-E fieldsurfaces parallel to B
❍ Make cavity from beryllium❍ Fill cavities with pressurized hydrogen gas
26
Front End Plan
❍ Mitigation often reduces performance❍ Operation limits of cavities still unknown❍ Baseline: choose technically optimal design
❑ Earlier “Study IIa” lattice❑ Improved Neuffer phase rotation
❍ One alternative to understand penalty/cost ofmitigation
27
Acceleration
❍ Efficiency: maximize passes through RF❍ Four stages to get good efficiency
❑ Linac to 0.9 GeV❑ Two RLAs: to 3.6 GeV and 12.6 GeV (4.5
passes)❑ FFAG to 25 GeV (11 passes)
❍ Use 200 MHz SCRF
28
Acceleration
12.6–25 GeV FFAG
3.6–12.6 GeV RLA
0.9–3.6 GeVRLA
Linac to0.9 GeV
29
AccelerationLinac and RLAs
❍ Lattices completely defined❍ More detailed magnet designs❍ Tracking beginning with soft ends
30
AccelerationFFAG
❍ Many passes (11): no switchyard❍ Injection/extraction challenging
❑ 15 cm radius, 0.09 T field, 7 needed, 546 mring circumference
❍ Selected triplet lattice with long drifts❑ Longer drifts ease injection/extraction❑ Double cavity in long drift: better gradient
✧ Reduce longitudinal distortion: largetransverse amplitude
31
AccelerationFFAG
❍ Add some chromaticity correction❑ Modest amount: hurts dynamic aperture❑ Helps longitudinal distortion
❍ Design kicker systems (magnet, power supply)❍ Study lattice dynamics in EMMA experiment
32
Decay Ring
❍ Long straights to maximize decays to detector❍ High beta functions in straight: reduce
divergence❑ Less divergence, less flux uncertainty for
given divergence uncertainty❍ Excellent dynamic aperture
33
Decay RingDynamic Aperture
34
Decay RingDiagnostics
❍ Reduce flux spectrum uncertainty❍ Polarimeter: measure decay electron spectrum
❑ Neutrino flux depends on polarization❑ Detector transverse to beam, in matching
section following weak bend❍ In-beam He gas Cerenkov: beam divergence
❑ Emittance growth: verify if acceptable
35
Decay RingPolarimeter
36
Low-Energy Neutrino Factory
❍ Same as above but stopping accelerationearlier, different decay ring
❍ Competitive with high energy (and bestsuperbeams) if θ13 large
❍ Interesting as part of staging❑ Start with low energy❑ Upgrade to high energy or larger detector
depending on physics results❍ Will be described in design reports
37
Conclusions
❍ Neutrino factory: precision measurements ofneutrino mixing
❍ Well-defined scenario, lattices almost complete❍ Continuing important R&D
❑ RF cavities in magnetic fields❑ MICE cooling experiment❑ EMMA: FFAG dynamics
❍ Starting engineering of components
38
Top Related