Accelerator based Neutrino beams

1
Accelerator based Neutrino beams

• Mats Lindroos

2
Outline

• Existing facilities
• CNGS
• The super beam
• The neutrino factory
• The beta beam
• Conclusions

3
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 nm beam at
CERN-SPS ? search for nt appearance at
Gran Sasso laboratory (730 km from CERN)
long base-line nm -- nt 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
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 nm- beam at Gran
Sasso
note 1 mm -gt 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
nm 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 nm component
• ne / nm 0.8    
• anti-nm / nm 2.1    
• anti-ne / nm 0.07   

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CERN underground
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CNGS target station
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CNGS target
-gt 10 cm long graphite rods, Ø 5mm and/or
4mm
proton beam
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
Magnetic Horn (S. v.der Meer, CERN)
length 6.5 m diameter 70 cm weight 1500
kg Pulsed devices 150kA / 180 kA, 1
ms water-cooled distributed nozzles
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Principle of focusing with a Magnetic Horn
Magnetic volume given by one turn at high
current ? specially shaped inner conductor -
end plates ? cylindrical outer 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?

• No Clear definition, but it is a very intense
  neutrino beam produced by a high power (gt1MW )
  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 captureliquid jetHorn
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Pion Capture Solenoid
20T
1.25T
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Liquid jet
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Jet test at BNL
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Targetry
Many difficulties enormous power density ?
lifetime problems pion capture
Stationary target
Replace target between bunches Liquid mercury
jet or rotating solid target
Proposed rotating tantalum target ring
Sievers
Densham
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Ionization cooling
IN
Liquid H2 dE/dx
sol
H2
rf
Beam
sol
RF restores only P// E constant
OUT
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Cooling experiment
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Cooling - rings
Main advantages shorter longitudinal cooling
Balbekov
Palmer
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Comparison of General Layout
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b-beam baseline scenario
SPS
PS
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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?

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Storage ring
SPL
ISOL Target ECR
Storage ring
Cyclotrons or FFAG
Fast cycling synchrotron
PS
SPS
Decay ring

• Charge exchange injection into storage ring
• Technology developed and in use at the Celsius
  ring in Uppsala
• Accumulation, bunching (h1) 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

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Overview Accumulation

• Sequential filling of 16 buckets in the PS from
  the storage ring

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PS
SPL
ISOL Target ECR
Storage ring
Cyclotrons or FFAG
Fast cycling synchrotron
PS
SPS
Decay ring

• Accumulation of 16 bunches at 300 MeV/u each
  consisting of 2.5x1012 6He(2) ions
• Acceleration to g9.2, 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

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SPS
SPL
ISOL Target ECR
Storage ring
Cyclotrons or FFAG
Fast cycling synchrotron
PS
SPS
Decay ring

• Acceleration of 8 bunches of 6He(2) to g150
• 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

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Decay ring
SPL
ISOL Target ECR
Storage ring
Cyclotrons or FFAG
Fast cycling synchrotron
PS
SPS
Decay ring

• Injection and accumulation will be described in
  talk on Thursday
• Major challenge to construct radiation hard and
  high field magnets

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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 b-decay losses accounted for, efficiency lt50

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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 b-decay losses accounted for, efficiency lt50

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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 g2488.08
• 18Ne has a g 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 r4654 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 RD for a full scale muon based neutrino
  factory is fascinating but very challenging
• Target issues still requires major RD
• Ionization cooling has to be experimentally tested

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What I can see in the crystal ball
As any Harry Potter reader knows that the art of
crystal ball viewing is both very difficult and
often prone to errors!

• 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

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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!