Injector and positron source scheme. A first evaluation Thanks to O Injector and positron source scheme. A first evaluation Thanks to O.Dadoun, F Poirier, R.Chehab, P Lepercq, R.Roux, J.Brossard A.Variola

LER Linac 6.4-6.7 GeV HER Polarised e+ upgrade Luminosity loss ? Energy 80-100 MeV LER Damping ring Energy TBA Injector and Positron driver 300-600 MeV Bypass Line for e- Matching Slac Gun (140 keV) Linac 6.4-6.7 GeV Capture section 200-300MeV Damping ring Energy TBA Bunchers Positron Converter HER A.Variola

Needed injection rates: J.Seeman Perugia: Lifetime 5 minutes=> dn/dt=1600*6*1010/5/60=3.2 1011/sec If inj. @ 25 Hz and 5 pulse /train (but this parameter we hope that can be increased to be more flexible) => 2.5 109 / bunch We did simulations up to the capture. So a security factor 2 , taking into account the transport from the capture to the DR, the injection and the transport to the HER/LER, gives to us a required intensity of 5 109/bunch Having 10nC (6.2 1010)e- at the gun this means a accepted yield of ~0.1 BUT if we want to work (to preserve the cathode) at half the laser power it is better to take into account an accepted yield of 0.2 BUT now new scheme =>from R Boni Talk=>Δn PS ≈ 2•109 …. @ PS output A.Variola

A first, rough estimation Before to start I would like to stress that: -In Dafne production at 200 MeV drive beam and efficiency at the linac end is ~ 1.2 % -The accepted yield scales ~ linearly with the energy so @ 600 MeV one can expect 3.6% - If the Slac gun provides 10 nC = 6.2 1010 electrons => At the Linac end: 2.25 109 - This already fits the SuperB requirements but the Dafne system is very close to a QWT, very good for energy selection but not for acceptance. Moreover the capture system is @ 3 GHz!!! - If the DR acceptance is big we can suppose to capture with an AMD that is much more efficient also if we increase the captured energy spread. A.Variola

Better configuration for capture L-Band: 1.9-2 cm RADIUS If needed SLAC cavities : 0.9 cm radius 1st L BAND A.Variola

Analytical estimations (dependents from arbitrary, AMD length and field scan A.Variola S band

2nd : G+Parmela ~ 400pC / Geant ~ 900pC “ ” If gun 10 nC = 6.2 10 10 1st : G+Parmela ~ 300pC / Geant ~ 600pC => (does not fit the safety factor 2 in the first case) 2nd : G+Parmela ~ 400pC / Geant ~ 900pC “ ” 3rd : G+Parmela ~ 600pC / Geant ~ 1.3 nC ok!!!! PER BUNCH A.Variola

Latest results G4 Parmela G4+Parm Energy (MeV) AMD Nb of particles entering AMD (G4) Nb of particles out of AMD (G4) Nb of particles simulated in Parmela (% of G4) Nb of particles out of 1st cavity in Parmela Nb of particles at end of cavity (Eref=283MeV) Yield at the 1st cavity for Parmela (G4) Yield at the cavity when Eref=283MeV 80 200* 6T – 50 cm 6256 (12.1%) 5000 (79.92%) 2937 (58.74%) 2313 (46.26% wrt 5000) 12.1%*58.74%=7.1% (11.%) (5.6% -prev 4.48) 300* 4T – 30 cm 9760 (17.6%) (51.23%) 2593 (51.86%) 2074 (41.48% wrt 5000) =9.1% (15.%) (7.3%-6.3) 500* 2T – 30 cm 15676 (28.2%) (31.89%) 2689 (53.78%) 2166 (43.32% wrt 5000) =15.1% (22.%) (12.2%-9.7) It seems that differences comes out form different definitions of the transverse B field….…still investigating A.Variola

So also in the most pessimistic case: 500 MeV / 2T / 30cm at the end of the capture section: 12.2 % So in L band we will have 750 pC accepted Also taking into account the factor 2 => 375 pC (near the double of what we need) A.Variola

1 Also for the pessimistic case we are in the spec after the AMD Conclusions 1 Also for the pessimistic case we are in the spec after the AMD Still some work to understand the discrepancies Geant - Parmela These are minimal configurations: @ 600 MeV – 30-50 cm we are overestimated and we can operate the gun at reduced power increasing the cathode lifetime Factor n can be gained in number of bunches per train (at present we take into account 5). This means that also the DR must collect more bunches……to be evaluated. Lowing the current (luminosity?) ~ 30% positron polarization is for free A.Variola

Future activity 1 Solve the discrepancies between codes (we are progressing) 2 Have a final estimation in L band 3 Introduce the SLAC Constant Grad section 4 Study a Const imp section to increase the acceptance Give a final estimation and solution (we hope for December-Frascati) A.Variola

Ps…we started also the simulation of the SLAC gun Ps…we started also the simulation of the SLAC gun. We have already the results for the standard configuration Start at 15 nC since we found 30% losses We would like to propose some modifications in the future to optimize the line in the SuperB framework. Transv Long z DE Phase space A.Variola