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Accelerator based Neutrino beams
Mats Lindroos
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Outline
• Existing facilities– CNGS
• The super beam• The neutrino factory
• The beta beam• Conclusions
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Acknowledgments
• CNGS– Konrad Elsener, CERN
• The Superbeam– Helmut Haseroth, Konrad Elsener,
Tsuyoshi Nakaya• The Neutrino Factory
– The nufact study group• The beta beam
– The beta beam working group
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CNGS
In Dec. 1999, CERN council approved the CNGS project:
build an intense beam at CERN-SPS
search for appearance at Gran Sasso laboratory (730 km from CERN)
“long base-line” -- oscillation experiment
note: K2K (Japan) running; NuMI/MINOS (US) under construction
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CERN to CNGS
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The Gran Sasso laboratory
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The CERN part
p + C (interactions) , K (decay in flight)
Polarity change foreseen!
…but the intensity will go down and the contamination goes up
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p / K profile at entrance to decay
tunnel
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CNGS muon beam profiles
first muon pit second muon pit
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Radial distribution of the
- beam at Gran Sassonote: 1 mm -> 1 km
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Number of particles expected per year:
For 1 year of CNGS operation, we expect:(4.8x1013 protons in SPS, 55% efficiency -- 1997)
protons on target 4.5 x 1019
pions / kaons at entrance to decay tunnel 5.8 x 1019 muons in first / second muon pit 3.6 x 1018 / 1.1 x 1017
in 100 m2 at Gran Sasso 3.5 x 1012
Upgrade with a factor of 1.5 feasible but requires investment in CERN injector complex
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Unwanted neutrino species
Relative to the main component:
e / = 0.8 %
anti- / = 2.1 %
anti-e / = 0.07 %
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CERN underground
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CNGS target station
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CNGS target
-> 10 cm long graphite rods, Ø = 5mm and/or 4mm
protonbeam
Note: - target rods interspaced to “let the pions out”
- target is helium cooled (remove heat deposited by the particles)
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CNGS focusing devices
length: 6.5 mdiameter: 70 cmweight: 1500 kg
Pulsed devices:150kA / 180 kA, 1 ms
water-cooled:distributed nozzles
“Magnetic Horn” (S. v.der Meer, CERN)
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Principle of focusing with a Magnetic
HornMagnetic volume given by “one turn” at high current:
specially shaped inner conductor - end plates cylindrical outer conductor
inner conductor
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CNGS Horn test
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CNGS decay tube + hadron stop
- dimensions of decay tube: 2.45 m diameter steel tubes, 6 m long pieces, 1 km total welded together in-situ vacuum: ~1 mbar
tube embedded in concrete
- hadron stop: 3.2 m graphite 15 m iron blocks
upstream end: water cooled
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What is the Super Neutrino Beam?
ProtonsProtonsProtonsProtonsProtons
– No Clear definition, but it is a very intense neutrino beam produced by a high power (>1MW ) accelerator.• A conventional method.• Still technically challenging due to the high
power and the high radiation environment, but not impossible.
– Multiple targets
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Target stack?
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Neutrino factoryCERN
•Superconducting proton linac as driver
•Proton bunch train not longer than decay ring
•Bunch to bucket philosophy
•Longitudinal cooling using bunch rotation
•Transversal cooling using ionization cooling
•Recirculating linear accelerators
•Decay ring
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Neutrino factoryJapan
3 GeV and 50 GeV rings are part
of JAERI-KEK Joint Project
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American Study II
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Target and pion capture
liquid jet+Horn
Protons
Current of 300 kA
To decay channel
Hg target B1/RB = 0
Gilardoni
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Pion Capture: Solenoid
20T 1.25T
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Liquid jet
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Jet test at BNLEvent #11 25th April
2001
P-bunch: 2.71012 ppb100 nsto = ~ 0.45 ms
Hg- jet : diameter 1.2 cm jet-velocity 2.5 m/sperp. velocity ~ 5 m/s
Picture timing [ms]0.000.754.50
13.00
K. Mc Donald, H. Kirk, A. Fabich, J.Lettry
Protons
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Targetry
Proposed rotating tantalum target ring
Many difficulties: enormous power density lifetime problems pion capture
Replace target between bunches:
Liquid mercury jet or rotating solid target
Stationary target:
Densham
Sievers
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Ionization cooling
H2 rf
Liquid H2: dE/dx
RF restores only P//: E constant
Beam
sol
sol
IN
OUT
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Cooling experiment
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Cooling - rings
Balbekov Palmer
Main advantages:shorterlongitudinal cooling
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Comparison of General Layout
System CERN FNAL (Study I) BNL (Study II) Japanese
System rep rate 50 Hz 2.5/5 Hz
Proton driver type
Linac (SPL) Synchrotron Synchrotron (AGS)
Synchrotron
p driver energy 2.2 GeV 16 GeV 24 GeV 50 GeV
Target material Hg C C
Collection Horn Solenoid Solenoid
Beam structure Bunch-to-bucket
Re-bunching Re-bunching
Phase rotation rf 2 induction linacs
3 induction linacs
FFAG
Cooling channel 88 MHz 200 MHz 200 MHz No cooling
Acceleration 2 RLAs (20/50 GeV)
2 RLAs (20/50 GeV)
1 RLA (20 GeV) 4 FFAGs (1/3/ 10/20-50 GeV)
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-beam baseline scenario
PS
SPSISOL target & Ion source
SPL
Cyclotrons
Storage ring and fast cycling synchrotron
Decay
Ring
Decay ring
Brho = 1500 Tm
B = 5 T
Lss = 2500 m
MeV 86.1 Average
MeV 937.1 Average
189
1810
63
62
cms
cms
E
eFeNe
E
eLiHe
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Objectives for CERN study
• Present a coherent and “realistic” scenario for acceleration of radioactive ions:– Use known technology (or reasonable
extrapolations of known technology)– Use innovations to increase the performance– Re-use a maximum of the existing CERN
accelerators– Use the production limit for ions of interest
as starting point
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Low-energy stage
• Fast acceleration of ions and injection into storage ring
• Preference for cyclotrons– Known price and technology
• Acceleration of 16 batches of 1.02x1012 or 2 1013 ions/s 6He(1+) from 20 MeV/u to 300 MeV/u
• Comment:– Bunching in cyclotron?
SPLISOL Target + ECR
Storage ring
Cyclotronsor FFAG
Fast cycling
synchrotronPS SPS
Decay ring
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Storage ring
• Charge exchange injection into storage ring– Technology developed and in use at the Celsius ring
in Uppsala
• Accumulation, bunching (h=1) and injection into PS of 1.02x1012 6He(2+) ions
• Question marks:– High radioactive activation of ring– Efficiency and maximum acceptable time for charge
exchange injection– Electron cooling or transverse feedback system to
counteract beam blow-up
SPLISOL Target + ECR
Storage ring
Cyclotronsor FFAG
Fast cycling
synchrotronPS SPS
Decay ring
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Overview: Accumulation
• Sequential filling of 16 buckets in the PS from the storage ring
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PS
• Accumulation of 16 bunches at 300 MeV/u each consisting of 2.5x1012 6He(2+) ions
• Acceleration to =9.2, merging to 8 bunches and injection into the SPS
• Question marks:– Very high radioactive activation of ring– Space charge bottleneck at SPS injection will
require a transverse emittance blow-up
SPLISOL Target + ECR
Storage ring
Cyclotronsor FFAG
Fast cycling
synchrotronPS SPS
Decay ring
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SPS
• Acceleration of 8 bunches of 6He(2+) to =150– Acceleration to near transition with a new
40 MHz RF system– Transfer of particles to the existing 200 MHz
RF system– Acceleration to top energy with the 200 MHz
RF system• Ejection in batches of four to the decay ring
SPLISOL Target + ECR
Storage ring
Cyclotronsor FFAG
Fast cycling
synchrotronPS SPS
Decay ring
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Decay ring
• Injection and accumulation will be described in talk on Thursday
• Major challenge to construct radiation hard and high field magnets
SPLISOL Target + ECR
Storage ring
Cyclotronsor FFAG
Fast cycling
synchrotronPS SPS
Decay ring
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Intensities: 18Ne
• From ECR source: 0.8x1011 ions per second• Storage ring: 4.1 x1010 ions per bunch• Fast cycling synch: 4.1 x1010 ion per bunch• PS after acceleration: 5.2 x1011 ions per batch• SPS after acceleration: 4.9 x1011 ions per batch• Decay ring: 9.1x1012 ions in four 10 ns
long bunch– Only -decay losses accounted for, efficiency <50%
e
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Intensities: 6He
• From ECR source: 2.0x1013 ions per second
• Storage ring: 1.0 x1012 ions per bunch• Fast cycling synch: 1.0 x1012 ion per bunch• PS after acceleration: 1.0 x1013 ions per batch• SPS after acceleration: 0.9x1013 ions per batch• Decay ring: 2.0x1014 ions in four 10
ns long bunch– Only -decay losses accounted for, efficiency <50%
e
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Result of CERN study• A baseline scenario for the beta-beam at
CERN exists• While, possible solutions have been
proposed for all identified bottlenecks we still have problems to overcome and…
• …it is certainly possible to make major improvements!– Which could result in higher intensity in the
decay ring!• First results are so encouraging that the
beta-beam option should be fully explored– Investigate sites at other existing accelerator
laboratories– Study a “Green field” scenario
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Higher energy in the decay ring?
• LHC top rigidity (23270 Tm):– 6He has a =2488.08– 18Ne has a = 4158.19– With a “futuristic” radiation hard
superconducting dipole design for the decay ring with a field of 5 Tesla the radius of the arcs will be r=4654 m!• Bigger than LHC arcs!
– Lower intensities as LHC only can handle transversally small bunches
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Neutron beams?
• As for a neutrino beam and neutron beam can be created if a beta-delayed neutron emitter is stored in the decay ring– High energy
• Physics case?
– Low energy• Medical use – neutron therapy• Waste transmutation at neutron resonances
– Intensity?
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Comments• The super beam can be available soon (when the
necessary high power drivers are completed)• The beta-beam is largely based on existing
technology but requires costly civil engineering for the decay ring– Moderate extrapolations on target technology– Strong synergies with projects in nuclear physics
• EURISOL• GSI upgrade• SPIRAL-2• SPES in Legnaro• Ion programme in LHC and low energy ion (accelerator and)
storage rings in Europe
• The R&D for a full scale muon based neutrino factory is fascinating but very challenging– Target issues still requires major R&D– Ionization cooling has to be experimentally tested
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What I can see in the crystal ball
• High power proton drivers become available– Next generation ISOL RNB
facilities– Super beams– Low energy electron neutrino
beams available• Physics case?
• The beta-beam is taken to higher energies
• Muon based neutrino factory starts delivering beam
As any Harry Potter reader knows that the art of crystal ball viewing is both very difficult and often prone to errors!
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Conclusion• Beta-beam at CERN:
– Low energy part will benefit nuclear physics– Acceleration to high energy is likely to benefit heavy ion programme
• LHC beam brightness?– Find a way of benefiting ion programme in LHC with our decay ring
and our luck might be made!• Having said that…
– GSI is world leading on high energy ions• Should open new possibilities at GSI for ions
• Having said that…– Italy is the only European country that seems willing to invest in high
energy physics inclduing neutrinos and underground detectors• Low energy neutrino beams?
• Having said that…– GANIL is one of the centers for accelerated radioactive ions
• Low energy neutrino beams?
• I hope I have set out a promising future for the research in to different aspects of the beta-beam!