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Machine parameters and limitations in the EURISOL beta-beam baseline. A.Fabich AB department, CERN On behalf of the Beta-beam study group http://cern.ch/beta-beam. Outline. Conceptual Design study Beta-beam baseline design Machine parameters Ion intensities Limitations Production

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machine parameters and limitations in the eurisol beta beam baseline

Machine parameters and limitations in the EURISOL beta-beam baseline

A.Fabich

AB department, CERN

On behalf of the

Beta-beam study group

http://cern.ch/beta-beam

outline
Outline
  • Conceptual Design study
    • Beta-beam baseline design
    • Machine parameters
    • Ion intensities
  • Limitations
    • Production
    • Decay losses
    • Acceptance
    • Tune shift
  • Conclusions

A.Fabich, CERN

conceptual design study
Conceptual design study
  • EURISOL Design Study
    • Within the 6th framework program of EU
    • Conceptual Design Report for Beta-Beam
  • The baseline scenario is based
      • on ISOL technique
      • at CERN: usage of PS and SPS machines
  • The Beta-beam Design Study is aiming for:
    • A beta-beam facility that will run for a “normalized” year of 107 s
    • Providing an annual rate of
      • 2.9*1018 anti-neutrinos (from 6He at g=100)
      • 1.1*1018 neutrinos (from 18Ne at g=100)

A.Fabich, CERN

beta beam baseline design
Beta-beam baseline design

Low-energy part

High-energy part

Neutrino source

Ion production

Acceleration

Beam to experiment

Proton Driver

Acceleration to final energy

PS & SPS

Ion productionISOL target & Ion source

SPS

Decay ring

Br= 1500 TmB = ~5 T C = ~7000 m Lss= ~2500 m

6He:g= 100 18Ne:g= 100

Neutrino Source

Decay Ring

Beam preparationECR pulsed

Ion accelerationLinac

PS

Acceleration to medium energy RCS

A.Fabich, CERN

machine cycle

cycle of 6He

magnet cycle (abstract)

Machine cycle

Baseline version:

  • Production
    • 6He, 18Ne
  • ECR, Linac and RCS
    • Cycling at 10 Hertz
  • Accumulation in the PS
    • Accumulation of 20 RCS bunches (~2 seconds)
  • Acceleration through PS and SPS as fast as possible
    • gtop = 100 for both isotopes
  • Injection into decay ring
    • Merging with circulating bunches
    • Every 6 s for 6He and every 3.6 s for 18Ne

A.Fabich, CERN

ion intensities
Ion intensities
  • For the design goal of

2.9*1018 antineutrinos/year

1.1*1018 neutrinos/year

  • Required isotope intensities:
    • Baseline version

Typical intensities of 108-109 ions for LHC injector operation (PS and SPS)

Top-down

A.Fabich, CERN

limitations
Limitations
  • Isotope production
  • The self-imposed requirement to re-use a maximum of existing CERN infrastructure
    • Cycling time, aperture limitations, collimation systems etc.
  • The high intensity ion bunches in the accelerator chain and decay ring
    • Space charge
    • Decay losses

A.Fabich, CERN

ion production
Ion production
  • 6He figures have reached the design values but no safety margin is yet provided.
  • 18Ne figures are more than one order of magnitude below the desired performance.
    • Missing factor (~25) for 18Ne production
    • Within baseline:
      • Improvement of isotope production/preparation
      • Possibly include an accumulation scenario at low energy
  • 19Ne no immediate solution (for baseline scenario)
    • Production rate much higher, but life time 10 times higher
    • Acceleration of an order of magnitude more ions
      • Excluded by space charge limits in the PS and SPS

A.Fabich, CERN

decay distribution
Decay distribution

Bunch

20th

15th

10th

5th

1st

  • 70% of first 6He bunch are lost before reaching decay ring
  • Overall only 50% (6He) and 80% (18Ne) reach decay ring
  • Normalization
    • Single bunch intensity to maximum/bunch
    • Total intensity to total number accumulated in RCS

total

A.Fabich, CERN

decay losses 1
Decay losses (1)
  • Relative decay distribution similar for both isotopes
  • ~90% of all decays before entering decay ring occur in the PS
  • Can be translated into power losses and compared with “existing” high intensity operation …

A.Fabich, CERN

decay losses 2

1st

1st

20th

20th

Decay losses (2)
  • In the PS most losses occur at low energy
    • accumulation
    • PS: g(6He)  [1.5 ; 9.3], g(18Ne)  [2.2 ; 15.5]

A.Fabich, CERN

power losses

Energy loss/cycle

Power loss

Power losses

Nucleon losses compared

  • PS and SPS comparable for CNGS and bb operation
  • PS exposed to highest power losses

A.Fabich, CERN

slide13

1σ Physical Emittance

S.Hancock

Scaling from normalized rms values of 7.8µm (H) and 4.2µm (V) for 11Tm 6He ions at PS injection, then

We assume the 18Ne has the same normalized emittance as the 6He because it comes from the Linac with identical βγ and is multi-turn injected into the RCS with the same geometrical set-up.

A.Fabich, CERN

slide14

Limits due to Tune Shift

S.Hancock

Considering for simplicity a round Gaussian beam of fully stripped ions, the self-field incoherent (“Laslett”) tune shift is

This allows upper limits on the total number of ions per shot to be estimated (taking into account unequal bunches) based on known limits at injection.

We assume τb = 80% of the rf bucket duration in all cases.

A.Fabich, CERN

solve tune shift limit
Solve tune shift limit

S.Hancock

  • Two batches from the PS instead of one.
  • One could also imagine deliberately blowing up the emittance to improve the situation in the downstream machine.

A.Fabich, CERN

conclusions
Conclusions
  • Baseline parameters fixed
    • Study goes now into detail of different machines and aspects
  • Average power losses are comparable to CNGS case (which is accepted)
    • PS has to stand the most demanding losses
    • Power losses < 3 W/m
  • Limits set by space charge in both the PS and SPS machines.
  • Main efforts will now focus on 18Ne shortfall.

A.Fabich, CERN

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