Status of the beta-beam study Mats Lindroos on behalf of the EURISOL beta-beam task UK HEP FORUM 2008 The beta-beam team

Outline of message I would like to give in this talk Beta-beam concept A beta-beam facility Layout (e.g EURISOL DS) Challenges How can we improve the beta-beam Before we build it: High gamma Beta-beams After we built it: Intensity and flux Electron capture Beta-beams High-Q vlaue Beta-beams The beta-beam team

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 a pure beam of electron neutrinos (or antineutrinos) through the beta decay of radioactive ions circulating in a high-energy (~100) storage ring. First study in 2002 Make maximum use of the existing infrastructure. Ions move almost at the speed of light The beta-beam team

Beta-beam Basics n Beta-beam 6He boost Aim: production of (anti-)neutrino beams from the beta decay of radio-active ions circulating in a storage ring Similar concept to the neutrino factory, but parent particle is a beta-active isotope instead of a muon. Beta-decay at rest n-spectrum well known from electron spectrum Reaction energy Q typically of a few MeV Accelerated parent ion to relativistic gmax Boosted neutrino energy spectrum: En2gQ Forward focusing of neutrinos: 1/g boost n 6He Beta-beam g=100 The beta-beam team

The beta-beam options Low energy beta-beams Nuclear physics, double beta-decay nuclear matrix elements, neutrino magnetic moments The medium energy beta-beams or the EURISOL beta-beam Lorenz gamma approx. 100 and average neutrino energy at rest approx. 1.5 MeV (P. Zucchelli, 2002) The high energy beta-beam Lorenz gamma 300-500 and average neutrino energy at rest approx. 1.5 MeV The very high energy beta-beam Lorenz gamma >1000 The high Q-value beta-beam Lorenz gamma 100-500 and average neutrino energy at rest 6-7 MeV The Electron capture beta-beam The beta-beam team

The EURISOL scenario Based on CERN boundaries Ion choice: 6He and 18Ne Relativistic gamma=100/100 SPS allows maximum of 150 (6He) or 250 (18Ne) Gamma choice optimized for physics reach Based on existing technology and machines Ion production through ISOL technique Bunching and first acceleration: ECR, linac Rapid cycling synchrotron Use of existing machines: PS and SPS Opportunity to share a Mton Water Cerenkov detector with a CERN superbeam, proton decay studies and a neutrino observatory Achieve an annual neutrino rate of either 2.9*1018 anti-neutrinos from 6He Or 1.1 1018 neutrinos from 18Ne Once we have thoroughly studied the EURISOL scenario, we can “easily” extrapolate to other cases. EURISOL study could serve as a reference. The beta-beam team

Which ion is best? Factors influencing ion choice Need to produce reasonable amounts of ions. Noble gases preferred - simple diffusion out of target, gaseous 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. EURISOL Choice in 2002 Helium-6 to produce antineutrinos: Neon-18 to produce neutrinos: The beta-beam team

However, there are other… The beta-beam team

Production of beta-beam isotopes The Isotope Separation On-Line (ISOL) method at medium energy EURISOL type production, uses typically 0.1-2 GeV protons with up to 100-200 kW beam power through spallation, fission and fragmentation Direct production Uses low energy but high intensity ion beams on solid or gas targets. Production through compound nuclei which forms with high cross section at low energies Direct production enhanced with a storage ring Enhancing the efficiency of the direct production through re-circulation and re-acceleration of primary ions which doesn’t react in the first passage through the target. Possible thanks to ionization cooling! The beta-beam team

Options for production ISOL method at 1-2 GeV (200 kW) >1 1013 6He per second <8 1011 18Ne per second 8Li and 8B not studied Studied within EURISOL Direct production >1 1013 (?) 6He per second 1 1013 18Ne per second Studied at LLN, Soreq, WI and GANIL Production ring 1014 (?) 8Li >1013 (?) 8B 6He and 18Ne not studied Will be studied in the future 1 GeV p p n 2 3 8 U 1 F r + spallation L i X fragmentation 4 C s Y fission The beta-beam team

6He production from 9Be(n,a) Converter technology: (J. Nolen, NPA 701 (2002) 312c) 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. The beta-beam team

Direct production: 16O(3He,n)18Ne Measurements at Louvain-La-Neuve (CRC) of cross section The gas target was constructed like a cell with thin entrance foils In experiment the target pressure and the 3He beam energy was changed Beam energy, MeV Target pressure, mbar (torr). Eloss,MeV 13 900 (675) 2 14.8 1200 (900) 2.4 Courtesy to Semen Mitrofanov and Marc Loislet at CRC, Belgium The beta-beam team

Preliminary results from CRC Production of 1012 18Ne in a MgO target: At 13 MeV, 17 mA of 3He At 14.8 MeV, 13 mA of 3He Producing 1013 18Ne could be possible with a beam power (at low energy) of 1 MW (or some 130 mA 3He beam). To keep the power density similar to LLN (today) the target has to be 60 cm in diameter. To be studied: Extraction efficiency Optimum energy Cooling of target unit High intensity and low energy ion linac High intensity ion source Thinn MgO target Water cooled target holder and beam dump Ion beam The beta-beam team

Light RIB Production with a 40 MeV Deuteron Beam T.Y.Hirsh, D.Berkovits, M.Hass (Soreq, Weizmann I.) Studied 9Be(n,α)6He, 11B(n,a)8Li and 9Be(n,2n)8Be production For a 2 mA, 40 MeV deuteron beam, the upper limit for the 6He production rate via the two stage targets setup is ~6∙1013 atoms per second. The beta-beam team

A new approach for the production Beam cooling with ionisation losses – C. Rubbia, A Ferrari, Y. Kadi and V. Vlachoudis in NIM A 568 (2006) 475–487 7Li(d,p)8Li 6Li(3He,n)8B 7Li 6Li Missed opportunities See also: Development of FFAG accelerators and their applications for intense secondary particle production, Y. Mori, NIM A562(2006)591 The beta-beam team

Critical review of the production ring concept Low-energy Ionization cooling of ions for Beta Beam sources – D. Neufer (To be submitted) Mixing of longitudinal and horizontal motion necessary Less cooling than predcited Beam larger but that relaxes space charge issues If collection done with separator after target, a Li curtain target with 3He and Deutron beam would be preferable Separation larger in rigidity The beta-beam team

Problems with collection device A large proportion of beam particles (6Li) will be scattered into the collection device. The scattered primary beam intensity could be up to a factor of 100 larger than the RI intensity for 5-13 degree using a Rutherford scattering approximation for the scattered primary beam particles (M. Loislet, UCL) The 8B ions are produced in a cone of 13 degree with 20 MeV 6Li ions with an energy of 12 MeV±4 MeV (33% !). Secondary ions Rutherford scattered particles Collection off-axes using Wien filter Beam Collection on-axes The beta-beam team

Low duty cycle, from dc to very short bunches… …or how to make meatballs out of sausages! Radioactive ions are usually produced as a “dc” beam but synchrotrons can only accelerate bunched beams. For high energies, linacs are long and expensive, synchrotrons are cheaper and more efficient. The beta-beam team

60 GHz « ECR Duoplasmatron » for gaseous RIB 2.0 – 3.0 T pulsed coils or SC coils Very high density magnetized plasma ne ~ 1014 cm-3 Small plasma chamber F ~ 20 mm / L ~ 5 cm Target Arbitrary distance if gas Rapid pulsed valve ? 1-3 mm 100 KV extraction UHF window or « glass » chamber (?) 20 – 100 µs 20 – 200 mA 1012 per bunch with high efficiency 60-90 GHz / 10-100 KW 10 –200 µs /  = 6-3 mm optical axial coupling optical radial (or axial) coupling (if gas only) P.Sortais et al. The beta-beam team

Charge state distribution! Multiple charge state acceleration in linac? The beta-beam team

What is important for the decay ring? The atmospheric neutrino background is large at 500 MeV, the detector can only be open for a short moment every second The decay products move with the ion bunch which results in a bunched neutrino beam Low duty cycle – short and few bunches in decay ring Accumulation to make use of as many decaying ions as possible from each acceleration cycle Ions move almost at the speed of light Only “open” when neutrinos arrive The beta-beam team

Injection The beta-beam team

Rotation The beta-beam team

Merging The beta-beam team

Repeated Merging The beta-beam team

Test experiment in CERN PS Ingredients h=8 and h=16 systems of PS. Phase and voltage variations. time energy S. Hancock, M. Benedikt and J-L.Vallet, A proof of principle of asymmetric bunch pair merging, AB-Note-2003-080 MD The beta-beam team

The Large Aperture Dipole, first feasibility study Courtesy Christine Vollinger high tip field, non-critical 6 T LHC ”costheta” design Good-field requirements only apply to about half the horizontal aperture. The beta-beam team

Collimation and absorption Merging: increases longitudinal emittance Ions pushed outside longitudinal acceptance  momentum collimation in straight section Decay product Daughter ion occurring continuously along decay ring To be avoided: magnet quenching: reduce particle deposition (average 10 W/m) Uncontrolled activation Arcs: Lattice optimized for absorber system OR open mid-plane dipoles Optical functions (m) primary collimator s (m) Straight section: Ion extraction et each end s (m) Deposited Power (W/m) A. Chance et al., CEA Saclay The beta-beam team

Model for absorbers Horizontal Plane Absorber outside beam-pipe Dipole 1 Dipole 2 Absorber in beam pipe 1 m 1 m 6 m 2 m 6 m 2 m The beta-beam team

Heat Deposition Model, one cell Q Absorbers B B ”Overlapping” Quad to check repeatability of pattern Q (ISR model) B (new design) B No Beampipe (angle large) Concentric cylinders, copper (coil), iron (yoke) Q The beta-beam team

Local Power Deposition Local power deposition concentrated around the mid plane. Limit for quench 4.3mW/cm3 (LHC cable data including margin) Situation fine for 6Li 18F: 12 mW/cm3 The beta-beam team

Intra Beam scattering, growth times Results obtained with Mad-8 6He 18Ne The beta-beam team

Particle turnover ~1 MJ beam energy/cycle injected  equivalent ion number to be removed ~25 W/m average Momentum collimation: ~5*1012 6He ions to be collimated per cycle Decay: ~5*1012 6Li ions to be removed per cycle per meter LHC project report 773 bb p-collimation merging decay losses injection Straight section Arc Momentum collimation The beta-beam team

Decay losses Losses during acceleration Preliminary results: 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 (1 s flat bottom). Collimation? New machine? SPS ok. Decay ring losses: Tritium and sodium production in rock is well below national limits. Reasonable requirements for tunnel wall thickness to enable decommissioning of the tunnel and fixation of tritium and sodium. Heat load should be ok for superconductor. FLUKA simulated losses in surrounding rock (no public health implications) The beta-beam team

Activation and coil damage in the PS The coils could support 60 years operation with a EURISOL type beta-beam The beta-beam team

Radiation protection issues Radiation safety for staff making interventions and maintenance at the target, bunching stage, accelerators and decay ring 88% of 18Ne and 75% of 6He ions are lost between source and injection into the Decay ring Safe collimation of “lost” ions during stacking ~1 MJ beam energy/cycle injected, equivalent ion number to be removed, ~25 W/m average Magnet protection Dynamic vacuum First study (Magistris and Silari, 2002) shows that Tritium and Sodium production in the ground water around the decay ring should not be forgotten The beta-beam team

Neutrino flux from a beta-beam EURISOL beta-beam study Aiming for 1018 (anti-)neutrinos per year It is possible that it could be increased to some1019 (anti-) neutrinos per year. However, this only be clarified by detailed and site specific studies of: Production Bunching Multiple charge state acceleration in linac Loss management Magnet protection Cooling down times for interventions Tritium and Sodium production in ground water The beta-beam team

How effective is the different proposed improvements? Increase production, improve bunching efficiency, accelerate more than one charge state and shorten acceleration Improves performance linearly Can be done as an upgrades! Accumulation Improves to saturation Can be done as an upgrade! Improve the stacking; sacrifice duty factor, add cooling or increase longitudinal bunch size The beta-beam team

Stacking efficiency and low duty factor Normalized Annual rate For 15 effective stacking cycles, 54% of ultimate intensity is reached for 6He and for 20 stacking cycles 26% is reached for 18Ne The beta-beam team

Why do we gain with such an accumulation ring? Left: Cycle without accumulation Right: Cycle with accumulation. Note that we always produce ions in this case! The beta-beam team

The beta-beam in EURONU DS The study will focus on production issues for 8Li and 8B 8B is highly reactive and has never been produced as on ISOL beam Production ring enhanced direct production Which is the best ring lattice? How to collect the produced ions? What are the “real” cross sections for the reactions? How can the accelerator chain and decay ring be adapted to 8Li and 8B Magnet protection system Intensity limitations The beta-beam team

Gamma and decay-ring size, 6He Rigidity [Tm] Ring length T=5 T f=0.36 Dipole Field rho=300 m Length=6885m 100 935 4197 3.1 150 1403 6296 4.7 200 1870 8395 6.2 350 3273 14691 10.9 500 4676 20987 15.6 New SPS Civil engineering Magnet R&D New version corrected version posted 3 September 2008 thanks to Sanjib Kumar Agarwalla who spotted a mistake in the previous table.

Conclusions The EURISOL beta-beam conceptual design report will be presented in second half of 2009 First coherent study of a beta-beam facility A beta-beam facility using 8Li and 8B First result from Euronu DS WP A beta-beam facility can be built today… Known technology with good performance …and tomorrow In a phased scenario the intensity and type of ion can be improved/changed Crucial to chose the right machine-detector combination (distance) from the beginning! The beta-beam team