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

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

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

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 = 100 18Ne: g = 100 Neutrino Source Decay Ring Beam preparation ECR pulsed Ion acceleration Linac PS Acceleration to medium energy RCS M. Benedikt CARE/BENE CERN

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. 20 batches during 1.9 s. RCS: further bunching to ~100 ns. Acceleration to ~500 MeV/u. 10 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. 20 repetitions during 1.9 s. M. Benedikt CARE/BENE CERN

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

Goals vs. starting conditions For the base line design, the aims are (J. Bouchez et al., NuFact’03): An annual rate of 2.9 1018 anti-neutrinos (6He) along one straight section An annual rate of 1.1 1018 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.): 1.0x1014 ions Rel. gamma: 100 18Neon10+ (single target) Intensity (av.): 7.2x1013 ions Rel. gamma: 100 M. Benedikt CARE/BENE CERN

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

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

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

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

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

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

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

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

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

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

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