Collaborators The beta-beam study group: cea, France

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The Beta-beam

  • Mats Lindroos

  • on behalf of

  • The beta-beam study group


  • The beta-beam study group:

    • CEA, France: Jacques Bouchez, Saclay, Paris Olivier Napoly, Saclay, Paris Jacques Payet, Saclay, Paris
    • CERN, Switzerland: Michael Benedikt, AB Peter Butler, EP Roland Garoby, AB Steven Hancock, AB Ulli Koester, EP Mats Lindroos, AB Matteo Magistris, TIS Thomas Nilsson, EP Fredrik Wenander, AB
    • Geneva University, Switzerland: Alain Blondel Simone Gilardoni
    • GSI, Germany: Oliver Boine-Frankenheim B. Franzke R. Hollinger Markus Steck Peter Spiller Helmuth Weick
    • IFIC, Valencia: Jordi Burguet, Juan-Jose Gomez-Cadenas, Pilar Hernandez, Jose Bernabeu
    • IN2P3, France: Bernard Laune, Orsay, Paris Alex Mueller, Orsay, Paris Pascal Sortais, Grenoble Antonio Villari, GANIL, CAEN Cristina Volpe, Orsay, Paris
    • INFN, Italy: Alberto Facco, Legnaro Mauro Mezzetto, Padua Vittorio Palladino, Napoli Andrea Pisent, Legnaro Piero Zucchelli, Sezione di Ferrara
    • Louvain-la-neuve, Belgium: Thierry Delbar Guido Ryckewaert
    • UK: Marielle Chartier, Liverpool university Chris Prior, RAL and Oxford university
    • Uppsala university, The Svedberg laboratory, Sweden: Dag Reistad
    • Associate: Rick Baartman, TRIUMF, Vancouver, Canada Andreas Jansson, Fermi lab, USA, Mike Zisman, LBL, USA

The beta-beam

  • Idea by Piero Zucchelli

    • A novel concept for a neutrino factory: the beta-beam, Phys. Let. B, 532 (2002) 166-172
  • The CERN base line 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
    • If possible find an “existing” detector site

CERN: -beam baseline scenario

Target values for the decay ring


  • Objective:

  • Production, ionization and pre-bunching of ions

  • Challenges:

  • Production of ions with realistic driver beam current

    • Target deterioration
  • Accumulation, ionization and bunching of high currents at very low energies

ISOL production

Mercury jet converter

60-90 GHz « ECR Duoplasmatron » for pre-bunching of gaseous RIB

Low-energy stage

  • Objective:

  • Fast acceleration of ions and injection

  • Acceleration of 16 batches to 100 MeV/u

Rapid Cycling Synchrotron

  • Objective:

  • Accumulation, bunching (h=1), acceleration and injection into PS

  • Challenges:

  • High radioactive activation of ring

  • Efficiency and maximum acceptable time for injection process

    • Charge exchange injection
    • Multiturn injection
  • Electron cooling or transverse feedback system to counteract beam blow-up?


  • Accumulation of 16 bunches at 300 MeV/u

  • Acceleration to =9.2, merging to 8 bunches and injection into the SPS

  • Question marks:

    • High radioactive activation of ring
    • Space charge bottleneck at SPS injection will require a transverse emittance blow-up

Overview: Accumulation

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


  • Objective:

  • 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

  • Challenges:

  • Transverse acceptance

Decay ring

  • Objective:

  • Injection of 4 off-momentum bunches on a matched dispersion trajectory

  • Rotation with a quarter turn in longitudinal phase space

  • Asymmetric bunch merging of fresh bunches with particles already in the ring

Injection into the decay ring

Horizontal aperture layout

Full scale simulation with SPS as model

Stacking in the Decay ring

Asymmetric bunch merging

Asymmetric bunch merging

Decay losses

  • Losses during acceleration are being studied:

    • 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:
      • Can be managed in low energy part
      • PS will be heavily activated
        • New fast cycling PS?
      • SPS OK!
      • Full FLUKA simulations of decay ring losses:
        • Tritium and Sodium production surrounding rock well below national limits
        • Reasonable requirements of concreting of tunnel walls to enable decommissioning of the tunnel and fixation of Tritium and Sodium

Decay losses

  • Acceleration losses:

How bad is 9 W/m?

  • For comparison, a 50 GeV muon storage ring proposed for FNAL would dissipate 48 W/m in the 6T superconducting magnets. Using a tungsten liner to

    • reduce peak heat load for magnet to 9 W/m.
    • reduce peak power density in superconductor (to below 1mW/g)
    • Reduce activation to acceptable levels
  • Heat load may be OK for superconductor.

SC magnets

  • Dipoles can be built with no coils in the path of the decaying particles to minimize peak power density in superconductor

    • The losses have been simulated and one possible dipole design has been proposed

Tunnels and Magnets



The Super Beam

R&D (improvements)

  • Production of RIB (intensity)

    • Simulations (GEANT, FLUKA)
    • Target design, only 200 kW primary proton beam in present design
  • Acceleration (cost)

    • FFAG versa linac/storage ring/RCS
    • High gamma option
  • Tracking studies (intensity)

    • Loss management
  • Superconducting dipoles ( of neutrinos)

    • Pulsed for new PS/SPS (GSI FAIR)
    • High field dipoles for decay ring to reduce arc length
    • Radiation hardness (Super FRS)

Comments & speculations: Ne and He in decay ring simultaneously

  • Possible gain in counting time and reduction of systematic errors

    • Cycle time for each ion type doubles!
  • Requiring =(60)150 for He will at equal rigidity result in a =(100)250 for Ne

    • Physics?
    • Detector simulation should give “best” compromise
  • Requiring equal revolution time will result in a R of 97(16) mm (=300 m)

    • Insertion in one straight section to compensate

Comments & sepculations: Accumulation Ne + He in DECAY RING

Comments & sepculations: Accumulation Ne + He before acceleration

  • Base line scenario assumes accumulation of 16 bunches for one second at 300 MeV/u (PS) for both He and Ne

  • Optimization assuming fixed ECR intensity (out):

Comments & speculations: Accumulation before acceleration

Comments & speculations: Wasted time?

Comments & speculations: Higher Gamma?

  • Requires either a larger bending radius or a higher magnetic field for the decay ring, the baseline circumference is 6885 m and has a bending radius () of 300 m:

      • At =500 (6He) , =935 m at B=5 T
      • To keep the percentage of straight section the same as the baseline the ring would become 21.4 km long
      • Alternatively new dipoles: =300 m at B=15.6 T
      • Or LHC type dipoles at B=10 T and =468 m with a circumference of 7794 m
  • Requires an upgrade of SPS or ramping of the decay ring

    • SPS upgrade expensive and time consuming
    • Ramping of decay ring requires less frequent fills and higher total intensity

Comments & speculations: Duty factor (or empty buckets)

  • The baseline delivers a neutrino beam with an energy badly troubled by atmospheric background

    • Duty factor=4 10-4, 4 buckets out of 919 possible filled —› 10 ns total bunch length
    • At =500 the duty factor can be increased to 10-2 (P. Hernandez), 92 buckets filled or 23 times the intensity theoretically, can that be realised?

Comments & speculations: Electron Capture, Monochromatic beams

  • Nuclei that only decay by electron capture generally have a long half-life (low Q value, <1022 keV)

    • Some possible candidates: 110Sn (4.1 h half life) and 164Yb (75.8 min half life)
    • Maybe possible if very high intensities can be collected in the decay ring and a high duty factor can be accepted (0.1)
      • High gamma with ramping of the decay ring?
      • For the baseline: With =259, assuming 2.3 1016 ions in the decay ring and a duty factor of 0.1 there would be 4 109 neutrinos per second at 259x0.326 MeV=84.434 MeV, is that useful?

Design Study

Superbeam & Beta Beam cost estimates (NUFACT02)

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