A.Variola Frascati SuperB meeting 1 Injector and positron source scheme. A.Variola, O.Dadoun, F Poirier, R.Chehab, P Lepercq, R.Roux, J.Brossard

A.Variola Frascati SuperB meeting 2 Slac Gun (140 keV) Bunchers Injector and Positron driver MeV Positron Converter Capture section MeV Bypass Line for e- Linac GeV Damping ring Energy TBA Damping ring Energy TBA LER HER Matching Polarised e+ upgrade Luminosity loss ? Energy MeV In SLAC we proposed ….but now see R.Boni talk

A.Variola Frascati SuperB meeting 3 Needed injection rates: new scheme =>from J.Seeman and R Boni Talk=>Δn PS ≈ 2 – PS output ~ 333 pC/bunch Taking a factor 2 => 600 pC exit capture section

A.Variola Frascati SuperB meeting 4 From SLAC…this is always valid 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 600 MeV one can expect 3.6% - If the Slac gun provides 10 nC = electrons => At the Linac end: 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 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 Frascati SuperB meeting ws - 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 Frascati SuperB meeting 6 L band / Geant and Parmela AMD input – G4 = 8569 positrons AMD output – G4 But we want yield : 8569/1.58= 5423 e- (=nb of positrons entering the AMD / production yield e-/e+) Nb of particles (MeV)  E rms (MeV)  X rms (cm)  X’ rms (rad)  z (cm) MeV case – AMD 6 T, 50 cm, r=2cm With this sample, we have a yield of 59.7% for the AMD (=3235/5423) Y (cm) X (cm)

A.Variola Frascati SuperB meeting 7 AMD (6 T – 50 cm) exit X (cm) X’ (rad) Energy (MeV) Population

A.Variola Frascati SuperB meeting 8 ACS – L band ACS: Accelerating Capture Section 1.3 GHz, aperture 1.8 cm Input s z =1cm (random gaussian distributed) PositionNb of particles (MeV)  E rms (MeV)  X rms (cm)  X’ rms (rad)  z (cm) End of AMD cm** End of 1 st cavity 2105 End of ACS Round beam i.e.  x =~  y,  x’ =~  y’

A.Variola Frascati SuperB meeting 9 ACS – L band ACS: Accelerating Capture Section 1.3 GHz, aperture 1.8 cm  (deg) Energy (MeV) X (cm) X’ (rad)

A.Variola Frascati SuperB meeting 10 S - Band SLAC type TW cavities: –1 tank is constituted of 85 travelling wave structures –1 tank = 3.01 m –In total 6 tanks are used here to bring the positrons at least up 250 MeV For the simulation with Parmela, the ACS is then constructed with one single file containing the 6 tanks (but here the gradient is not decreasing in the fourth tank…need POISSON files) Or the ACS is constructed with 2 files containing each 3 tanks. The second file takes as input the output of the first file (losses of particles are observed at junction of tanks 1 and 2!).

A.Variola Frascati SuperB meeting 11 ACS – S band 2.8 GHz, aperture 0.95 cm SLAC type constant aperture Input  z =1cm** (case with 6 tanks in 1 file) PositionNb of particles (MeV)  E rms (MeV)  X rms (cm)  X’ rms (rad)  z (cm) End of AMD ** End of 1 st cavity (trwave)* End of ACS *In the case of the S-band ACS it is here the end of the first trwave i.e. at 7.9 cm after the beginning of the ACS (for Parmela simulation we have: drift+cell+half a trwave). Note: the nb of particles at the end of the first tank, i.e. at ~3.01m, is 527. ** Random gaussian distribution

A.Variola Frascati SuperB meeting 12 ACS – S band 2.8 GHz, aperture 0.95 cm SLAC type constant aperture Input  z =1cm (case with 6 tank in 1 file)  (deg) Energy (MeV) X (cm) X’ (rad)

A.Variola Frascati SuperB meeting 13 ACS – S band 2.8 GHz, aperture 0.95 cm SLAC type constant aperture Input  z =1cm (case with 3 tanks separated in 2 files) PositionNb of particles (MeV)  E rms (MeV)  X rms (cm)  X’ rms (rad)  z (cm) entrance cm** End of 1 st cavity Same as previous case End of ACS

A.Variola Frascati SuperB meeting 14 Summary => Yield AMD typeYield e-/e+ (production) AMD Yield (e- /e+ in %) ACS type Yield at end of 1 st cav. (e-/e+ in %) Yield at end of ACS (e-/e+ in %) 6 T – 50 cm (600 MeV) L-Band ** 6 T – 50 cm (600 MeV) S-Band18 (9.7*)5.9^ 5.9 T - 15 cm (200 MeV) S-Band3.3 (2.0*)1.6** For S-Band, the case with 6 tanks in 1 file is chosen * End of tank **Explanation: 1857 positrons/ 5423 electrons = 34.2%, 789 positrons/ electrons = 1.6% ^ in the case of 3 tanks in 2 files, yield: 246/5423 = 4.5%

A.Variola Frascati SuperB meeting 15 Analytical estimations (dependents from arbitrary, AMD length and field scan S band : matching more critical

A.Variola Frascati SuperB meeting 16 Conclusions L Band =>35% (3.5nC). We can loose more than a order of magnitude!!! S Band => ~600 pC without any optimisation. Consistent with the initial boundary conditions S Band Dafne => 1.6%. Consistent with the measured yield (good to validate simulations) So : we want to be safe => L Band up to damping ring S band works anyway…a little margin can be gained by: 1) increasing the energy (700 – 800 MeV) 2) New design of S band with larger diameter (lower gradient) 3) 2 GHz? Should be an occasion for CLIC synergies…..politically correct! S Band Dafne good agreement. In my point of view this scheme is viable, we have only to decide if we want to have a big margin or not Next steps : 1) Solve the 1 / 2 tanks discrepancy 2) Optimisation of L/S band 3) Post acceleration up to 600 MeV (1 GeV?) The best test bench should be to send the SLAC gun here, in Frascati and mount it on Dafne. Is it feasible? Money, integration, manpower…..

A.Variola Frascati SuperB meeting 17 Better configuration for capture L-Band: cm RADIUS 1 st L BAND We had problems of agreement between Geant and Parmela: Solved

A.Variola Frascati SuperB meeting 18 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 EEPhase space