J. Bouchez CEA/DAPNIA NuFact 03 June 5,2003 BETA BEAMS : design update and physics reach Physics motivation Recent progress on design Expected performances

Mixing matrix: the missing parameters 1   e          l = U l i i U is a unitary matrix: 3 angles :  12,  13,  23 plus 1 CP violating phase  3 masses m 1, m 2, m 3 SUN :   m 12 2 = eV 2,  12 ~ 35 o ATM :  m 23 2 = eV 2,  23 = 45 o Missing :  13 and the phase  both govern the    e oscillation at the atmospheric frequency We know that  13 is < 10 o we have to look for a small oscillation

= A 2 + S 2 + 2AS sin  = A 2 + S 2 - 2AS sin   atm) =  13 S (sun) ~ 0.04 for LMA How to measure  13 and  Study   e oscillations at first maximum L= 500 km/GeV x E compare amplitudes for neutrinos and antineutrinos Amplitudes are small, but asymetry may be LARGE

How to overcome superbeam limitations ? Main problem : SPL protons produce less negative pions, so less antineutrinos antineutrino cross-section ~ 5 times smaller than neutrinos So 10 SPL years have to be shared as ~ 2 neutrino + 8 antineutrino years The solution : Produce a e beam to study e    oscillation and run it SIMULTANEOUSLY with   beam from SPL Compare   e and e    (T asymetry, equivalent to CP asymetry) THIS WAS THE INITIAL MOTIVATION FOR A BETA BEAM

BETA BEAMS Concept proposed by Piero Zucchelli Produce radioactive ions (ISOL technique) Accelerate them in the CERN accelerator complex up to  of order 100 Store ions in a storage ring with long straight sections aimed at a far detector Advantages strongly focussed neutrino beam due to small Q value of beta decays (quality factor  /Q) very pure flavour composition (   contamination ~ ) perfectly known energy spectrum Baseline scenario studied at CERN (Mats Lindroos and collaborators) Recent progress presented at a special workshop at Moriond Possible synergy between beta beams and EURISOL Updated study of expected performances (Mauro Mezzetto)

Possible  + emitters ( e )

Possible  - emitters ( e )

 -beam initial baseline scenario (before Moriond) PS SPS ISOL target & Ion source SPL Cyclotrons Storage ring and fast cycling synchrotron Decay Ring Decay ring Brho = 1500 Tm B = 5 T L ss = 2500 m

A new idea for the ion source: using a pulsed ECR source Idea proposed by Pascal Sortais at Moriond workshop Based on experimental work done at Grenoble with Phoenix => High density/high frequency plasmas allow to produce efficiently short bunches (20  s instead of 20 ms) of ions with a high repetition rate (16 Hz) by pulsing the RF and the HV Advantages: Ions are already very well bunched and (hopefully) totally stripped This simplifies considerately the design downstream: Possibility to use a LINAC rather than a cyclotron or a FFAG Multiple turn injection in the storage ring becomes possible (40 turns)

New RFQ LINAC 3 PSB Simplification of the injection system P. Sortais, Moriond workshop

A simpler scheme SPL ISOL target Pulsed ECR source (100 keV, 20  s) LINAC (50 MeV/u 20  s) Storage ring (40 turn injection, single bunch of 150 ns with h=1 cavity, acceleration to 300 MeV/u) PS : Accumulation of 16 bunches (each He ions) reduced to 8 bunches by acceleration to  = 9.2 SPS : Acceleration of 8 bunches to  ~ 100 and ejection in batches of four to the decay ring Decay ring

Stacking in the decay ring 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 cycling (120 s as compared to 8s). –We need to stack at least over 10 to 15 injector cycles. Cooling is not an option for the stacking process: –Electron cooling is excluded because of the high electron beam energy and in any case far too long cooling times. –Stochastic cooling is excluded by the high bunch intensities. Stacking without cooling creates “conflicts” with Liouville.

Asymmetric bunch pair merging (Benedikt, Hancock, Lindroos) Try to cheat Liouville macroscopically by: –Stacking longitudinally in the centre of the existing beam. –Using the fact that “older” parts of the stack are naturally loosing density because of beta decay. Asymmetric bunch pair merging moves the fresh bunch into the centre of the stack and pushes less dense phase space areas to larger amplitudes until these are cut by the momentum collimation system. The maximum density is always in the centre of the stack as required by the experiment.

Injection into the decay ring

intensities: 6 He From ECR source 2.0x10 13 ions per second PS after acceleration: 1.0 x10 13 ions per batch SPS after acceleration: 0.9x10 13 ions per batch Decay ring: 2.0x10 14 ions 50 % losses ions in four 10ns (decays already accounted for) long bunches

intensities: 18 Ne FOR 1 ISOL target : From ECR source: 0.8x10 11 ions per second PS after acceleration: 5.2 x10 11 ions per batch SPS after acceleration: 4.9 x10 11 ions per batch Decay ring: 9.1x10 12 ions Accounting for 50 % losses: 4.5x10 12 ions in four 10 ns long bunches FOR 3 ISOL targets 1.3 x10 13 ions

A VERY EXCITING POSSIBILITY Nothing forbids to store at the same time 18 Ne and 6 He ions in the decay ring with no loss of intensity for each species But as the rigidities for Neon and Helium will be different, the neutrino and antineutrino energies will be in the ratio 5 to 3. First studies show that this energy difference is quite acceptable This brings immediately a gain of a factor nearly 2 in run time to achieve a given sensitivity on CP violation with beta beams

Present results of CERN study A baseline scenario for the beta-beam at CERN exists Recent developments have brought important simplifications There is certainly room for further improvements which could result in higher intensities for example, a new (faster) PS would solve radiation problems and improve other projects (CNGS) First results are so encouraging that the beta- beam option should be fully explored –Study a “Green field” scenario ?

Performances of super + beta beams Working hypotheses (Mauro Mezzetto): Announced intensities for e and anti  e (with 3 ISOL targets for Neon ) UNO-like detector installed at a new Frejus underground laboratory 10 years running of both SPL and beta beam : - 2 years of  - 8 years of anti  - 10 years of e - 10 years of anti e Since 18 Ne and 6 He ions do not have the same rigidity, the anti e energy will be 1.67 times the e energy THIS NEEDS TUNING TO FIND THE BEST COMPROMISE

Lorentz boost optimization : Preferred values between  = 55 and 75

   and  measurements using superbeam and betabeam SPL: 2 years in  + 8 years in anti  BETABEAM: 10 years of 6 He AND 18 Ne (Mauro Mezzetto)

CP sensitivity : domain of 99% CL effect for maximal CP violation

Conclusions Beta beams are a splendid tool to study neutrino oscillations Together with superbeams, they allow to measure  13 and  with a sensitivity approaching that of a neutrino factory The possibility to install at Frejus a megaton detector receiving both a superbeam and a beta beam offers to Europe a unique opportunity Moriond workshop has brought together 2 communiities interested in intense radioactive beams (EURISOL and neutrino physicists) They have agreed to coordinate their efforts on the necessary R&D Last but not least, it has become clear at the workshop that low energy beta beams could also address very important issues for nuclear physics

Neutrino-Nucleus Interactions Neutrinos Supernovae Nucleosynthesis NUCLEAR STRUCTURE and REACTIONS STANDARD MODEL and BEYOND ASTROPHYSICS Cristina VOLPE

THE END (but to be continued) My warmest thanks to the all the people who have worked hard on this project Special thanks to Mats Lindroos Mauro Mezzetto

The neutrino mixing matrix: 3 angles and a phase   23  (atmospheric) = 45 0,  12  (solar) = 30 0,  13  (Chooz) < 13 0 OR?  m 2 23 = eV 2  m 2 12 = eV 2       2  m 2 23 = eV 2

= A CP  sin    solar term… sin  sin (  m 2 12 L/4E) sin   … need large values of sin    m 2 12 (LMA) but *not* large sin 2   … need APPEARANCE … P( e  e ) is time reversal symmetric (reactors or sun are out) … can be large (30%) for suppressed channel (one small angle vs two large) at wavelength at which ‘solar’ (S)= ‘atmospheric’ (A) and for e  ,  … asymmetry is opposite for e   and e   P( e   ) - P( e   ) P( e   ) + P( e   ) P( e   ) = ¦A¦ 2 +¦S¦ A S sin  P( e   ) = ¦A¦ 2 +¦S¦ A S sin  ‘Solar’ (S) -- ‘Atmospheric’ (A) 

60-90 GHz « ECR Duoplasmatron » for gaseous RIB Very high density magnetized plasma n e ~ cm – 3.0 T pulsed coils or SC coils GHz / KW 10 –200 µs / = 6-3 mm optical axial coupling optical radial coupling (if gas only)  1-3 mm 100 KV extraction UHF window or « glass » chamber (?) Target Rapid pulsed valve 20 – 100 µs 20 – 200 mA to ions per bunch with high efficiency Very small plasma chamber  ~ 20 mm / L ~ 5 cm Arbitrary distance if gas

Rapid ionization of RIB : future prospects 1 – ECRIS can supply either efficiency or pulsed currents ECRIS must supply efficiency AND pulsed currents 2 – 28 GHz / 10 KW preliminary tests could be done at ISN 3 – Possible extension to RIB of condensable elements and upgrade of the other metallic ion stable beams (Pb) next step of PHOENIX development 4 – Never start an heavy ion project without a strong preliminary ion source development program !

Storage ring Charge exchange injection into storage ring –Technology developed and in use at the Celsius ring in Uppsala Accumulation, bunching (h=1) and injection into PS of 1.02x He(2+) ions Question marks: –High radioactive activation of ring –Efficiency and maximum acceptable time for charge exchange injection –Electron cooling or transverse feedback system to counteract beam blow-up SPL ISOL Target + ECR Storage ring Cyclotrons or FFAG Fast cycling synchrotron PSSPS Decay ring

Low-energy stage Fast acceleration of ions and injection into storage ring Preference for cyclotrons –Known price and technology Acceleration of 16 batches of 1.02x10 12 or ions/s 6 He(1 + ) from 20 MeV/u to 300 MeV/u Comment: –Bunching in cyclotron? SPL ISOL Target + ECR Storage ring Cyclotrons or FFAG Fast cycling synchrotron PSSPS Decay ring

PS Accumulation of 16 bunches at 300 MeV/u each consisting of 2.5x He(2+) ions Acceleration to  =9.2, merging to 8 bunches and injection into the SPS Question marks: –Very high radioactive activation of ring –Space charge bottleneck at SPS injection will require a transverse emittance blow-up SPL ISOL Target + ECR Storage ring Cyclotrons or FFAG Fast cycling synchrotron PS SPS Decay ring

SPS Acceleration of 8 bunches of 6 He(2 + ) to  =150 –Acceleration to near transition with a new 40 MHz RF system –Transfer of particles to the existing 200 MHz RF system –Acceleration to top energy with the 200 MHz RF system Ejection in batches of four to the decay ring SPL ISOL Target + ECR Storage ring Cyclotrons or FFAG Fast cycling synchrotron PS SPS Decay ring

Decay ring Injection and accumulation will be described in talk on Thursday Major challenge to construct radiation hard and high field magnets SPL ISOL Target + ECR Storage ring Cyclotrons or FFAG Fast cycling synchrotron PSSPS Decay ring

Overview: Accumulation Sequential filling of 16 buckets in the PS from the storage ring

Acknowledgements We would like to especially thank all our colleagues in the “beta beam study group” for their support and helpful discussion. Conclusions Asymmetric bunch merging is a promising method for stacking beams of radioactive ions. Simulations give excellent results, an experimental proof of principle is under way. For a beta beam decay ring, an off-momentum injection with bunch merging seems at present the favorable injection an stacking scenario.