. . . but are going to hit their ultimate limitations. In a - PowerPoint PPT Presentation

Mauro Mezzetto Istituto Nazionale di Fisica Nucleare, Sezione di Padova Beta Beams Summary: • Introduction. • The accelerator complex. • Physics potential. • Different scenarios. Thanks to: P . Zucchelli, M. Lindroos, J. Bouchez, P . Hernandez, JJ Gomez-Cadenas, J. Burguet-Castell, O. Mena, D. Casper, A. Blondel, S. Gilardoni, C. Volpe, S. Rigolin, A. Donini, P . Migliozzi, F . Terranova, P . Lipari (I hope I’m not forgetting too many people). Neutrino 2004, College de France, June 14-19 ,2003 M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 1

. . . but are going to hit their ultimate limitations. In a conventional neutrino beam , neutrinos are produced by SECONDARY particle decays (mostly pions and kaons). Given the short life time of the pions ( 2 . 6 · 10 − 8 s), they can only be focused (and charge selected) by means of magnetic horns. Then they are let to decay in a decay tunnel, short enough to prevent most of the muon decays. • Besides the main component ( ν µ ) at least 3 other neutrino flavours are present ( ν µ , ν e , ν e ), generated ν e contamination is a background for θ 13 and δ , by wrong sign pions, kaons and muon decays. ν µ contamination dilutes any CP asymmetry. • Hard to predict the details of the neutrino beam starting from the primary proton beam, the problems being on the secondary particle production side. • Difficult to tune the energy of the beam in case of ongoing optimizations. M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 3

All these limitations are overcome if secondary particles become primary Collect, focus and accelerate the neutrino parents at a given energy. This is impossible within the pion lifetime, but can be tempted within the muon lifetime (Neutrino Factories) or within some radioactive ion lifetime (Beta Beams) : The full 6 He flux MonteCarlo code • Just one flavour in the beam • Energy shape defined by just two parameters: Function Flux(E) Data Endp/3.5078/ Data Decays /2.9E18/ the endpoint energy of the beta decay and the ye=me/EndP c ...For ge(ye) see hep-ph0312068 γ of the parent ion. ge=0.0300615 2gE0=2*gamma*EndP c ... Kinematical Limits • Flux normalization given by the number of ions If(E.gt.(1-ye)*2gE0)THEN Flux=0. Return Endif circulating in the decay ring. c ...Here is the Flux Flux=Decays*gamma**2/(pi*L**2*ge)*(E**2*(2gE0-E))/ + 2gE0**4*Sqrt((1-E/2gE0)**2-ye**2) • Beam divergence given by γ . Return M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 4

Beta Beam (P. Zucchelli: Phys. Lett. B532:166, 2002) M. Lindroos and collaborators, see http://beta-beam.web.ch/beta-beam EURISOL Existing at CERN DECAY RING SPL B = 5T SPS Isol target L = 2500 m & Ion source New RFQ Linac PS PSB • 1 ISOL target to produce He 6 , 100 µA , ⇒ 2 . 9 · 10 18 ion decays/straight session/year. ⇒ ν e . • 3 ISOL targets to produce Ne 18 , 100 µA , ⇒ 1 . 2 · 10 18 ion decays/straight session/year. ⇒ ν e . • The 4 targets could run in parallel, but the decay ring optics requires: γ ( Ne 18 ) = 1 . 67 · γ ( He 6 ) . M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 5

MW-L inac : SPL (S uperconducting P roton L inac ) 45 keV 7 MeV 120 MeV 1.08 GeV 2.2 GeV 13m 78m 334m 345m 3 MeV 18MeV 237MeV 389MeV H - RFQ1 chop. RFQ2 dump RFQ1 chop. RFQ2 R DTL CCDTL F Q 1 c h o p . R F Q 2 β 0.52 β 0.7 β 0.8 RFQ1 chop. RFQ2 LEP-II Source Low Energy section DTL Superconducting section Stretching and collimation line PS / Isolde Accumulator Ring EKIN = 2.2 GeV EKIN = 2.2 GeV 2 ma current 23 Power = 4 MW Power = 4 MW 100 µ a needed by Beta-Beam 10 protons/year 10 protons/year Protons/s = 10 16 16 Protons/s = 10 targets It can accomodate both a conventional ν beam (SPL-SuperBeam) and a Beta Beam M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 6

He production by 9 Be(n, α ) 6 He production by 9 Be(n, α ) 6 β Converter technology: ( J. Nolen, NPA 701 (2002) 312c ) Layout very similar to planned EURISOL converter target aiming for 10 15 fissions per s.

Asymmetric bunch merging There is an absolute need for stacking in the decay ring. ● Not enough flux from source and injection chain. – Life time is an order of magnitude larger than injector – 0.5 0.4 @ A D cycling (120 s as compared to 8s). 0.3 0.2 0.1 0 We need to stack at least over 10 to 15 injector cycles. – 8.17 ´ 10 11 4 D s V e @ e Cooling is not an option for the stacking process: ● 2 0 @ MeV D 0 Electron cooling is excluded because of the high electron – - 2 beam energy and in any case far too long cooling times. - 4 - 60 - 40 - 20 0 20 40 60 Stochastic cooling is excluded by the high bunch @ ns D – 0.6 rms E { = 0.0585 eVs BF = 0.16 E { matched = 0.298 eVs = 1.57 ´ 10 11 0.5 N e intensities. rms p = 1.2 ´ 10 - 3 2 s p f s0;1 = 822;790 Hz 0.4 @ A D 0.3 0.2 0.1 Stacking without cooling creates “conflicts” with Liouville. ● 0 8.52 ´ 10 11 7.5 D s V 5 e @ e 2.5 0 @ MeV D Asymmetric bunch pair merging 0 - 2.5 (Benedikt, Hancock, Vallet, A proof of principle of asymmteric - 5 bunch pair merging , AB-note-2003-080 MD)) - 7.5 - 125 - 100 - 75 - 50 - 25 0 25 50 @ ns D 0.4 E { rms = 0.0583 eVs BF = 0.14 E { matched = 1.63 ´ 10 11 = 0.317 eVs N e 0.3 rms p = 1.34 ´ 10 - 3 2 s p f s0;1 = 0;1060 Hz Try to cheat Liouville macroscopically by: @ A D 0.2 ● 0.1 0 Stacking longitudinally in the centre of the existing beam. – 8.16 ´ 10 11 4 D s V e @ e Using the fact that “older” parts of the stack are naturally 2 – 0 @ MeV D loosing density because of beta decay. 0 - 2 Asymmetric bunch pair merging moves the fresh bunch into the ● - 4 centre of the stack and pushes less dense phase space areas to - 100 - 75 - 50 - 25 0 25 50 75 @ ns D 0.5 0.4 E { rms = 0.0593 eVs BF = 0.224 E { matched = 0.333 eVs = 1.56 ´ 10 11 @ A D 0.3 N e larger amplitudes until these are cut by the momentum rms p = 8.5 ´ 10 - 4 f s0;1 = 0;415 Hz 2 s p 0.2 0.1 0 collimation system. 8.1 ´ 10 11 4 D s V e e @ The maximum density is always in the centre of the stack as 2 ● 0 @ MeV D 0 required by the experiment. - 2 - 4 - 60 - 40 - 20 0 20 40 60 @ ns D E { rms = 0.0639 eVs BF = 0.168 E { matched = 0.323 eVs = 1.6 ´ 10 11 N e rms p = 1.25 ´ 10 - 3 2 s p f s0;1 = 823;790 Hz

The decay ring • Civil engineering costs: Estimate of 400 MCHF for 1.3% incline (13.9 mrad) • Ring len g th: 6850 m, useful straight session: 36% • Magnet cost: f irst estimate at 100 MCHF (SC magnets, 5T) •For  <75 the length could be halved •With LHC magnets (10 T) the length could be halved •A 2 km ring could be feasible under these assumptions S. Russenschuck, CERN 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 FLUKA simulated losses in surrounding one possible dipole design has been rock (no public health implications) proposed

R&D (improvements)  ISOL Linac, Rapid Decay SPL Target cyclotron cycling PS SPS ring + ECR or FFAG synchrotron • Production of RIB (intensity) – Simulations (GEANT, FLUKA) – Target design, only 100 kW primary proton beam in present design • Acceleration (cost) – FFAG versa linac/storage ring/RCS • 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) Mat s Lindroos M-MWATT Workshop, CERN, May 2004.

Fluxes CC Rates x 10 7 ν /m 2 /20 meV ν CC/kton/year 4.5 4500 SPL ν µ 4 SPL ν µ 4000 − − SPL ν SPL ν 3.5 µ µ 3500 − − e (He 6 ) e (He 6 ) Beta ν Beta ν 3 3000 Beta ν e (Ne 18 ) Beta ν e (Ne 18 ) 2.5 2500 2 2000 1.5 1500 1 1000 0.5 500 0 0 0 0.2 0.4 0.6 0.8 1 0 0.2 0.4 0.6 0.8 1 E ν (GeV) E ν (GeV) < E ν > < E ν > Fluxes @ 130 km CC rate (no osc) Years Integrated events ν/m 2 /yr (440 kton × 10 years) (GeV) events/kton/yr (GeV) SPL Super Beam 4 . 78 · 10 11 ν µ 0.27 41.7 0.32 2 36698 3 . 33 · 10 11 ν µ 0.25 6.6 0.30 8 23320 Beta Beam 1 . 97 · 10 11 ν e ( γ = 60 ) 0.24 4.5 0.28 10 19709 1 . 88 · 10 11 ν e ( γ = 100 ) 0.36 32.9 0.43 10 144783 M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 11

UNO detector • Fiducial volume: 440 kton: 20 times SuperK. • 60000 PMTs (20”) in the inner detector, 15000 PMTs in the outer veto detector. • Energy resolution is poor for multitrack events but quite adequate for sub-GeV neutrino interactions. • It would be hosted at the Frejus laboratory, 130 km from CERN, in a 10 6 m 3 cavern to be excavated. The ultimate detector for proton decay, atmospheric neutrinos, supernovae neutrinos. M. Mezzetto, “Beta Beam”, Neutrino 04, College de France , 14-19 June 2004. 12