1. 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
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2. LER Linac 6.4-6.7 GeV HER Polarised e+ upgrade Luminosity loss ?
Energy MeV
LER
Damping ring
Energy TBA
Injector and
Positron driver
MeV
Bypass Line for e-
Matching
Slac Gun (140 keV)
Linac GeV
Capture section
MeV
Damping ring
Energy TBA
Bunchers
Positron Converter
HER
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3. Needed injection rates: J.Seeman Perugia:
Lifetime 5 minutes=> dn/dt=1600*6*1010/5/60= /sec
If 25 Hz and 5 pulse /train (but this parameter we hope that can be increased to be more flexible) =>
/ 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 ( )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
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4. 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 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.
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5. Better configuration for capture L-Band: 1.9-2 cm RADIUS
If needed SLAC cavities : 0.9 cm radius
1st L BAND
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6. Analytical estimations (dependents from arbitrary, AMD length and field scan
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S band

7. 2nd : G+Parmela ~ 400pC / Geant ~ 900pC “ ”
If gun 10 nC =
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
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8. 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
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9. 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)
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10. 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 600 MeV – 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
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11. 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)
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12. 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
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