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BETA-BEAM R&D in EUROPE. Michael Benedikt AB Department, CERN on behalf of the Beta-Beam Study Group Outline. Beta-beam baseline design The baseline scenario, ion choice, main parameters Ion production Decay ring design issues

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Michael Benedikt

AB Department, CERN

on behalf of the

Beta-Beam Study Group

NuFACT’04 - Beta Beam R&D


  • Beta-beam baseline design

    • The baseline scenario, ion choice, main parameters

    • Ion production

    • Decay ring design issues

  • Ongoing work and recent results

    • Asymmetric bunch merging for stacking in the decay ring

    • Decay ring optics design & injection

  • Future R&D within EURISOL

    • The EURISOL Design Study

    • The Beta-beam Task

  • Conclusions

NuFACT’04 - Beta Beam R&D

Introduction to Beta-beams

  • Beta-beam proposal by Piero Zucchelli:

    • A novel concept for a neutrino factory: the beta-beam, Phys. Let. B, 532 (2002) 166-172.

  • AIM: production of pure beams of electron neutrinos (or antineutrinos) from the beta decay of radioactive ions, circulating in a high energy decay ring (g~100)

  • The baseline scenario

    • Avoid anything that requires a “technology jump” which would cost time and money (and be risky)

    • Make use of a maximum of the existing infrastructure

NuFACT’04 - Beta Beam R&D

Beta-beam baseline design

Ion production


Neutrino source


Proton Driver SPL

Acceleration to final energy


Ion production ISOL target & Ion source


Neutrino Source

Decay Ring

Beam preparation ECR pulsed

Decay ring

Br = 1500 Tm B = 5 T C = 7000 m Lss = 2500 m

6He: g = 150 18Ne: g = 60

Ion acceleration Linac


Acceleration to medium energy RCS

NuFACT’04 - Beta Beam R&D

Main parameters (1)

  • Ion choice

    • Possibility to produce reasonable amounts of ions

    • Noble gases preferred - simple diffusion out of target, gas phase at room temperature

    • Not too short half-life to get reasonable intensities

    • Not too long half-life as otherwise no decay at high energy

    • Avoid potentially dangerous and long-lived decay products

  • Best compromise

    • 6Helium2+ to produce antineutrinos:

    • 18Neon10+ to produce neutrinos:

NuFACT’04 - Beta Beam R&D

Main parameters (2)

  • Target values in the decay ring


  • Intensity (av.): 1.0x1014 ions

  • Energy: 139 GeV/u

  • Rel. gamma: 150

  • Rigidity: 1500 Tm

18Neon10+ (single target)

  • Intensity (av.): 4.5x1012 ions

  • Energy: 55 GeV/u

  • Rel. gamma: 60

  • Rigidity: 335 Tm

  • The neutrino beam at the experiment has the “time stamp” of the circulating beam in the decay ring.

  • The beam has to be concentrated in as few and as short bunches as possible to maximize the peak number of ions/nanosecond (background suppression).

  • Aim for a duty factor of 10-4 -> this is a major design challenge!

NuFACT’04 - Beta Beam R&D
















1 GeV protons

















Ion production - ISOL method

  • Isotope Separation OnLine method.

  • Few GeV proton beam onto fixed target.

18Ne directly

6He via spallation n

NuFACT’04 - Beta Beam R&D

6He production from 9Be(n,a)

  • Converter technology preferred to direct irradiation (heat transfer and efficient cooling allows higher power compared to insulating BeO).

  • 6He production rate is ~2x1013 ions/s (dc) for ~200 kW on target.

Converter technology: (J. Nolen, NPA 701 (2002) 312c)

NuFACT’04 - Beta Beam R&D

18Ne production

  • Spallation of close-by target nuclides:18Ne from MgO:

    • 24Mg12 (p, p3 n4) 18Ne10

    • Direct target: no converter technology can be used, the beam hits directly the oxide target.

    • Production rate for 18Ne is ~ 1x1012 ions/s (200 kW dc proton beam at a few GeV beam energy).

    • 19Ne can be produced with one order of magnitude higher intensity but the half life is 17 seconds!

NuFACT’04 - Beta Beam R&D

2 x 1.1 ms to decay ring (4 bunches with few ns)




2.2 ms

2.2 ms

SPS: injection of 8 (16) bunches from PS. Acceleration to decay ring energy and ejection of 4 + 4 bunches. Repetition time 8 s.

PS: 1s flat bottom with 8 (16) injections. Acceleration in ~1s to top PS energy



1 s

1 s





RCS: further bunching to ~100 ns Acceleration to ~300 MeV/u. 8 (16) repetitions over 1s.

Post accelerator linac: acceleration to ~100 MeV/u. 8 (16) repetitions over 1s.

60 GHz ECR: accumulation for 1/8 (1/16) s ejection of fully stripped ~20ms pulse. 16 batches during 1s.



Target: dc production during 1 s.

1 s

1 s

7 s

From dc ions to very short bunches

NuFACT’04 - Beta Beam R&D

Decay ring design aspects

  • The ions have to be concentrated in very few very short bunches.

    • Suppression of atmospheric background via time structure.

  • There is an absolute need for stacking in the decay ring.

    • Not enough flux from source and injection chain.

    • Life time is an order of magnitude larger than injector cycling (120 s as compared to 8 s SPS cycling).

    • We need to stack at least over 10 to 15 injector cycles.

  • Cooling is not an option for the stacking process:

    • Electron cooling is excluded because of the high electron beam energy and in any case far too long cooling times.

    • Stochastic cooling is excluded by the high bunch intensities.

  • Stacking without cooling creates “conflicts” with Liouville.

NuFACT’04 - Beta Beam R&D

Asymmetric bunch pair merging

  • Moves the fresh bunch into the centre of the stack and pushes less dense phase space areas to larger amplitudes until these are cut by the momentum collimation system.

  • The maximum density is always in the centre of the stack as required by the experiment.

  • Requirements:

    • Dual harmonic RF systems:

    • Decay ring will be equipped with 40 and 80 MHz system.

    • Gives required bunch lengths of < 10 ns for physics.

  • Stack and fresh bunch need to be positioned in adjacent “buckets” of the dual harmonic system (12.5 ns distance!)

NuFACT’04 - Beta Beam R&D

Full scale simulation for SPS

NuFACT’04 - Beta Beam R&D

Test experiment in CERN PS

Merging of circulating bunch with empty phase space.

Longitudinal emittances are conserved

Negligible blow-up

NuFACT’04 - Beta Beam R&D



Test experiment in CERN PS

  • Ingredients:

    • Dual-harmonic RF system

    • 10 and 20 MHz systems of PS

    • Phase and voltage variations

  • Potential applications:

    • Production of hollow bunches

    • Stacking in longitudinal phase space

NuFACT’04 - Beta Beam R&D

Decay ring injection design aspects

  • Asymmetric merging requires fresh bunch injected in adjacent 2nd harmonic bucket to existing stack

  • Background suppression requires short bunches and therefore high frequency RF in decay ring ≥ 40MHz

  • Combination of both means 12.5 ns between bunches

    • Fast injection (septa & kickers) excluded (too fast, too rigid)

  • Alternative injection scheme proposal

    • Inject an off-momentum beam on matched dispersion trajectory

    • No fast elements required (bumper rise and fall ~10 ms)

    • Requires large normalized dispersion at injection point (small beam size and large separation by momentum difference)

    • Has to be paid by larger magnet apertures in decay ring

NuFACT’04 - Beta Beam R&D

Decay ring injection layout

  • Example machine and beam parameters:

    • Dispersion:Dhor = 10 m

    • Beta-function: bhor = 20 m

    • Moment. spread stack: Dp/p = ±1.0x10-3 (full)

    • Moment. spread bunch: dp/p = ± 2.0x10-4 (full)

    • Emit. (stack, bunch):egeom = 0.6 pmm


First turn after injection

Beam: ± 2 mm momentum

± 4 mm emittance

Required bump

22 mm

Septum & alignment 10 mm

Septum & alignment 10 mm

Stack: ± 10mm momentum

± 4 mm emittance

Separation: ~30 mm, corresponds to

3x10-3 off-momentum

22 mm

Central orbit undisplaced

NuFACT’04 - Beta Beam R&D

β-functions (m) Dispersion (m)

Horizontal bx

Vertical by

Horizontal Dispersion Dx

Begin of the arc

End of the arc

Injection area

Decay ring arc lattice design

A. Chance, CEA-Saclay (F)

FODO structure

Central cells detuned for injection

Arc length ~984m

Bending 3.9 T, ~480 m leff

5 quadrupole families

NuFACT’04 - Beta Beam R&D


Horizontal envelopes :

Δp/p = 0 kickers off

Δp/p = 0 kickers on

Δp/p = 0.8% kickers off

Δp/p = 0.8% kickers on

Vertical envelopes :

stored beam

injected beam

Decay ring injection envelopes

A. Chance, CEA-Saclay (F)

Envelope (m)

NuFACT’04 - Beta Beam R&D

Radiation protection - decay losses

  • Losses during acceleration

    • Full FLUKA simulations in progress for all stages (M. Magistris and M. Silari, Parameters of radiological interest for a beta-beam decay ring, TIS-2003-017-RP-TN)

  • Preliminary results:

    • Manageable in low energy part

    • PS heavily activated (1s flat bottom)

      • Collimation? New machine?

    • SPS ok.

    • Decay ring losses:

      • Tritium and Sodium production in rock well below national limits

      • Reasonable requirements for tunnel wall thickness to enable decommissioning of the tunnel and fixation of Tritium and Sodium

FLUKA simulated losses in surrounding rock (no public health implications)

NuFACT’04 - Beta Beam R&D

Future R&D

  • Future beta-beam R&D together with EURISOL project

  • Design Study in the 6th Framework Programme of the EU

  • The EURISOL Project

    • Design of an ISOL type (nuclear physics) facility

    • Performance three orders of magnitude above existing facilities

    • A first feasibility / conceptual design study was done within FP5

    • Strong synergies with the beta-beam especially low energy part:

      • Ion production (proton driver, high power targets)

      • Beam preparation (cleaning, ionization, bunching)

      • First stage acceleration (post accelerator ~100 MeV/u)

      • Radiation protection and safety issues

NuFACT’04 - Beta Beam R&D

EURISOL Design Study

  • Production of an Engineering Oriented Design, of the facility, in particular in relation to its most technologically advanced aspect (i.e. excluding the detailed design of standard elements of the infrastructure).

    • Technical Design Report for EURISOL.

    • Conceptual Design Report for Beta-Beam (first study).

NuFACT’04 - Beta Beam R&D

Eurisol Design Study Tasks

*PW=Paperwork PRO=Prototype E =Experiment

NuFACT’04 - Beta Beam R&D

EURISOL - Participating Institutes

NuFACT’04 - Beta Beam R&D

Task: Beta Beam Aspects

Starts at exit of heavy ion LINAC (~100 MeV/u) to Decay Ring (~100 GeV/u).


Proton Driver SPL

Acceleration to final energy


Ion production ISOL target & Ion source


Beam preparation ECR pulsed

Neutrino Source

Decay Ring

Decay ring

Br = 1500 Tm B = 5 T C = 7000 m Lss = 2500 m

6He: g = 150 18Ne: g = 60

Ion acceleration Linac


Acceleration to medium energy RCS

NuFACT’04 - Beta Beam R&D

Beta-Beam Sub-Tasks

  • Beta Beam task starts at exit of the EURISOL post accelerator.

  • Comprises the design of the complete chain up to the decay ring.

  • Organisation: „parameter and steering committee“ and 3 sub-tasks:

    • ST 1: Design of the low energy ring(s)

    • ST 2: Ion acceleration scenarios in PS/SPS and required upgrades of the existing machines including new designs to eventually replace PS/SPS

    • ST 3: Design of the high energy Decay Ring

    • Detailed work and man-power planning is under way

    • Around 38 (13 from EU) man-years for beta beam R&D over next 4 years (only within beta-beam task, not accounting linked tasks)

NuFACT’04 - Beta Beam R&D


  • Well established beta-beam base line scenario

  • R&D work has started on several critical aspects (mainly decay ring)

  • Beta-Beam Task well integrated in the EURISOL DS

  • Strong synergies between Beta Beam and EURISOL

  • Definitive EU decision expected these days

  • Detailed planning for coming 4 years under way

NuFACT’04 - Beta Beam R&D

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