Accelerator based Neutrino beams

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					Accelerator based Neutrino beams
Mats Lindroos

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• Existing facilities

• The super beam • The neutrino factory • The beta beam • Conclusions

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– 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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In Dec. 1999, CERN council approved the CNGS project:

an intense nm beam at CERN-SPS  search for nt appearance at Gran Sasso laboratory (730 km from CERN)
 build

“long base-line” nm -- nt oscillation experiment
note: K2K (Japan) running; NuMI/MINOS (US) under construction
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The Gran Sasso laboratory

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The CERN part


 (interactions) 

p+, K+  (decay in flight)  m+ + nm

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 -> 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
-> 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

inner conductor
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CNGS Horn test

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CNGS decay tube + hadron stop

- dimensions of
 2.45 m diameter steel tubes, 6 m long pieces, 1 km total  welded together in-situ  vacuum: ~1 mbar  tube embedded in concrete
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decay tube:

- hadron stop:  3.2 m graphite  15 m iron blocks
 upstream end: water cooled

What is the Super Neutrino Beam?
– 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

Protons Protons Protons Protons Protons

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Target stack?

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Neutrino factory CERN
•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 factory Japan

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
Current of 300 kA
p Protons Hg target B1/R To decay channel B=0

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Pion Capture: Solenoid

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Liquid jet

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Jet test at BNL
Event #11 25th April 2001
K. Mc Donald, H. Kirk, A. Fabich, J.Lettry



Hg- jet :

2.71012 ppb 100 ns to = ~ 0.45 ms diameter 1.2 cm jet-velocity 2.5 m/s perp. velocity ~ 5 m/s
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Picture timing [ms] 0.00 0.75 4.50 13.00

Many difficulties: enormous power density  lifetime problems pion capture Replace target between bunches: Liquid mercury jet or rotating solid target Stationary target:

Proposed rotating tantalum target ring

Sievers Densham
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Ionization cooling

Liquid H2: dE/dx


Beam H2 rf

RF restores only P//: E constant
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Cooling experiment

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Cooling - rings
Main advantages: shorter longitudinal cooling

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Comparison of General Layout
System System rep rate Proton driver type p driver energy Target material CERN 50 Hz Linac (SPL) 2.2 GeV Hg Synchrotron 16 GeV C FNAL (Study I) BNL (Study II) 2.5/5 Hz Synchrotron (AGS) 24 GeV C Synchrotron 50 GeV Japanese

Beam structure Phase rotation Cooling channel Acceleration

Bunch-tobucket rf 88 MHz 2 RLAs (20/50 GeV)

Re-bunching 2 induction linacs 200 MHz 2 RLAs (20/50 GeV) Moriond meeting

Re-bunching 3 induction linacs 200 MHz 1 RLA (20 GeV) FFAG No cooling 4 FFAGs (1/3/ 10/20-50 GeV)

b-beam baseline scenario
Decay ring Brho = 1500 Tm


B=5T Lss = 2500 m
6 2 6 He3 Li e n

Decay ISOL target & Ion source Cyclotrons Storage ring and fast cycling synchrotron SPS Ring

Average Ecms  1.937 MeV
18 10

Ne18Fe e +n 9

Average Ecms  1.86 MeV


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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 Moriond meeting as starting point

Low-energy stage
SPL ISOL Target + ECR Cyclotrons or FFAG Storage ring Fast cycling synchrotron PS SPS Decay ring

• 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 Cyclotrons or FFAG Storage ring 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 (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
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Overview: Accumulation

• Sequential filling of 16 buckets in the PS from the storage ring
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SPL ISOL Target + ECR Cyclotrons or FFAG Storage ring 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 g=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
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SPL ISOL Target + ECR Cyclotrons or FFAG Storage ring Fast cycling synchrotron PS SPS Decay ring

• Acceleration of 8 bunches of 6He(2+) to g=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
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Decay ring
SPL ISOL Target + ECR Cyclotrons or FFAG Storage ring 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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• 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 <50%
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• 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

ne – Only b-decay losses accounted for, efficiency <50%
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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 betabeam option should be fully explored
– Investigate sites at other existing accelerator laboratories – Study a “Green field” scenario Moriond meeting

Higher energy in the decay ring?
• LHC top rigidity (23270 Tm):
– 6He has a g=2488.08 – 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 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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• 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 hasMoriond meeting to be experimentally tested

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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• 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!
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