A Method to Produce Intense Positron Beams via Electro Pair Production   on Electrons
  Intense positron beams can be prepared via electro production with the reaction $e^{-} + e^{-} \rightarrow e^{-}+e^{+}+e^{-}+e^{-}$ due to the availability of high current electron beams. Head on collisions inside of a magnetic field of a solenoid are used to produce unpolarized/polarized positrons via $e^{-}-e^{+}$ - pair production. A flux of unpolarized positrons, $N_{positron}=6.55 \cdot 10^{11} s^{-1}$, has been obtained as a result of calculations for a special case of parameters with beam currents for both electron beams of $I_{e}$=10 mA and beam momenta of $p_{beam 1}$=0.63 MeV/c and $p_{beam 2}$=10.0 MeV/c. Intensities are an order of magnitude smaller in the case of polarized positrons due to a reduced current of one of the electron beams. Suitable cuts on momenta of the positrons allow to achieve a polarization transfer from electrons to positrons of $\geq $ 85\% reducing, however, the intensity to 27\% 
Berthold Schoch
physics.acc-ph