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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!