1. Status of the BETA-BEAM Task within the EURISOL Design Study
Michael Benedikt
AB Department, CERN
on behalf of the
Beta-beam Study Group
M. Benedikt
CARE/BENE CERN

2. Outline The Beta-beam study inside EURISOL
The Beta-beam base line design
Work progress in the beta beam task
Conclusions
M. Benedikt
CARE/BENE CERN

3. Eurisol DS + Beta-beam 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 low-energy part of the beta-beam led to integration of beta-beam design study into EURISOL:
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.
Aims of the Design Study (Feb 2005 – Jan 2009):
Technical Design Report for EURISOL.
Conceptual Design Report for Beta-Beam.
M. Benedikt
CARE/BENE CERN

4. Beta-beam baseline design
Low-energy part
High-energy part
Ion production
Acceleration
Neutrino source
Beam to experiment
Proton Driver SPL
Acceleration to final energy
PS & SPS
Ion production ISOL target & Ion source
SPS
Decay ring
Br = 1500 Tm B = ~5 T C = ~7000 m Lss= ~2500 m
6He: g = Ne: g = 100
Neutrino Source
Decay Ring
Beam preparation ECR pulsed
Ion acceleration Linac PS
Acceleration to medium energy RCS
M. Benedikt
CARE/BENE CERN

5. From dc to very short bunches
2 ms t B
1.9 s PS
SPS
2 ms to decay ring
(20 bunches of <5 ns)
PS: 1.9 s flat bottom with 20 injections. Acceleration in 0.8 s to top energy.
Target: dc production during 1.9 s.
60 GHz ECR: accumulation for 0.1 s.
Ejection of fully stripped ~20 ms pulse batches during 1.9 s.
RCS: further bunching to ~100 ns. Acceleration to ~500 MeV/u Hz repetition rate.
SPS: injection of 20 bunches from PS. Acceleration to decay ring energy and ejection. Repetition time 6 s (6He).
4.1s
Post accelerator linac: acceleration to ~100 MeV/u repetitions during 1.9 s.
M. Benedikt
CARE/BENE CERN

6. The Beta-beam task
Beta-beam task starts at exit from EURISOL post accelerator and comprises the design of the complete accelerator chain up to the decay ring.
Conceptual design of an large scale accelerator complex.
Work is organised in four sub-task:
ST1: Parameters and base line design.
ST2: Design of low energy rings (RCS + eventually accumulation/cooling ring).
ST3: Ion acceleration in PS and SPS and design of alternative machines.
ST4: Decay ring design.
Participating institutes:
CEA Saclay, CERN, GSI, IN2P3 Orsay, RAL, Stockholm Univ., TRIUMF.
M. Benedikt
CARE/BENE CERN

7. Goals vs. starting conditions
For the base line design, the aims are (J. Bouchez et al., NuFact’03):
An annual rate of anti-neutrinos (6He) along one straight section
An annual rate of neutrinos (18Ne) at g=100
always for a “normalized” year of 107 seconds.
The corresponding target values for ions in the decay ring are:
The status at beginning of the design study (Jan. 2005) was:
Antineutrino rate (and 6He figures) factor 3 below goal.
Neutrino rate (and 18Ne figures) factor 50 below desired performance.
Excessive incoherent space charge effects at PS injection.
6Helium2+
Intensity (av.): x1014 ions
Rel. gamma:
18Neon10+ (single target)
Intensity (av.): x1013 ions
Rel. gamma:
M. Benedikt
CARE/BENE CERN

8. ST1: Parameters & baseline design
Improve base line design (performance, beam physics limitations)
Provide consistent parameters for complete chain (inj./ej. energies, etc.)
No modifications on ion production (EURISOL) side (# of targets, etc.), only change is ECR frequency.
10 Hz operation of RCS and ECR (100 ms accumulation time in ECR for intensity increase).
Use of all possible RF buckets in the PS (10 MHz system allows for h=21). 20 buckets filled, one empty for the kicker.
No bunch merging in PS at top energy at expense of duty factor.
RCS energy range increased from Br = 8 Tm to 11 Tm to decrease space charge effects at PS injection.
Increased number of injections/merges in decay ring for 18Ne. Possible due to larger bucket acceptance for 18Ne.
M. Benedikt
CARE/BENE CERN

9. ST1: Base line version2
magnet cycle (abstract)
cycle of 6He
DC ion production
6He, 18Ne
ECR, Linac and RCS
Cycling at 10 Hertz
Accumulation in PS
20 RCS bunches (~2 seconds)
Acceleration in PS and SPS
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
Present status version2 (after 9 months of the design study):
Antineutrino rate (and 6He figures) have reached the design values but no safety margin is yet provided.
Neutrino rate (and 18Ne figures) still a factor 20 below desired performance. Achieved improvement factor 2.5. Next step: analyze production side.
M. Benedikt
CARE/BENE CERN

10. ST2: Design of low energy rings
Comparison Beta-beam RCS (100 MeV/u injection to 11 Tm) to to other machines:
Dipole field requirements
Beta-beam RCS Bmin=0.24 T Bmax=1.0 T
ISIS(50 Hz, 800 MeV p) Bmin=0.18 T Bmax=0.7 T
AUSTRON(25/50 Hz, 1.6 GeV p) Bmin=0.20 T Bmax=0.94 T
JPARC(25Hz, 3 GeV protons) Bmin=0.25 T Bmax=1.01 T
Accelerating voltage and RF frequency
Beta-beam RCS 10 Hz, V=100 kV, h=1, FRF ~ 0.64 to 1.24 MHz for He FRF ~ 0.64 to 1.45 MHz for Ne
ISIS 50 Hz, V=140 kV, h=2, FRF=1.34 to 3.1 MHz,
J-Parc RCS 25 Hz, V=450 kV, h=2, FRF=1.23 to 1.67 MHz,
AUSTRON 25/50Hz, V=250 kV, h=2, FRF=1.34 to 2.62 MHz
Parameters are very similar to other RCS machines.
M. Benedikt
CARE/BENE CERN

11. ST2: Design of low energy rings
Analysis of candidate lattices for RCS:
FODO lattices (JParc) have the advantage of relatively low quadrupole gradient, regular optical functions and easy chromaticity correction.
Doublet / triplet lattices (ISIS, Austron) provide longer uninterrupted drift space for injection, extraction, RF cavities and collimation system.
Dispersion suppressed in straight sections to avoid synchro-betatron coupling.
J-Parc layout
The Beta-beam RCS magnet and RF parameters are well inside typical RCS specifications and do not pose critical technical issues.
Next step: lattice choice/optics design.
A. Tkatchenko
M. Benedikt
CARE/BENE CERN

12. ST3: Ion acceleration PS-SPS
Analysis of beam losses:
Relative decay distribution similar for both isotopes
~90% of all decays (before injection to decay ring) occur in the PS, conenctrated at low energy (accumulation over 2 s).
A. Fabich
M. Benedikt
CARE/BENE CERN

13. ST3: Ion acceleration PS-SPS
Comparison of beam losses Beta-beam - CNGS
Energy loss/cycle
Power loss
Power deposition due to beam losses:
PS and SPS comparable for CNGS and Beta-beam operation.
PS exposed to highest power deposition.
M. Benedikt
CARE/BENE CERN

14. ST3: Ion acceleration PS-SPS
Loss distribution / dynamic vacuum effects / new PS:
Loss distribution along machine period
Pressure evolution due to desorption PS
Bottom-up
P. Spiller
New
“PS”
Losses quasi equally distributed in PS, no place for collimation.
Optimized doublet lattice allows separation of decay products and collimation.
M. Benedikt
CARE/BENE CERN

15. ST4: Decay ring design
Detailed studies and simulation of asymmetric merging (accumulation).
The neutrino beam at the experiment has the “time stamp” of the circulating beam and must 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 below 10-2.
Full scale simulation of longitudinal bunch merging.
S. Hancock
M. Benedikt
CARE/BENE CERN

16. ST4: Decay ring design
Lattice design and injection region optimisation
Injected beam
Off-momentum injection on matched dipsersion orbit.
Needed for asymmetric merging distance between injected and stored bunches 25 ns.
Avoids very fast elements.
Has to be paid by additional aperture in the arcs, injection region.
Next steps:
Collimation strategy and design.
SC magnets, RF system.
Stored beam
A. Chance
M. Benedikt
CARE/BENE CERN

17. Other activities
Feasibility and performance improvement with additional low-energy accumulation/cooling ring.
Tracking and beam loss studies for complete chain.
Improvement possibilities for 18Ne (collaboration with other EURISOL tasks)
Production rate of 18Ne (multiple targets?)
Charge state distribution after ECR source.
Analysis of 19Ne as alternative to 18Ne (higher production rate, longer lifetime).
M. Benedikt
CARE/BENE CERN

18. Conclusions
The Beta-beam design study within EURISOL is advancing well, encouraging results obtained after only 9 months.
Main efforts will now focus on looking for possibilities to reduce the 18Ne shortfall (together with other EURISOL tasks.
Going beyond the base line design (at a later stage) with additional accumulation rings, and other new machines (green-field) may open the way to important performance enhancements but efforts are very restricted due to the limited manpower available.
M. Benedikt
CARE/BENE CERN