Angular collection using solenoids

Pion collection after the target is considered using solenoids. Two collection systems, involving solenoids, the quarter wave transformer and the adiabatic lens, widely used for the positron collection in linear accelerators, are described. Their main features, such as the acceptance volume in transverse phase space, the maximum source radius, the maximum transverse momentum acceptance, are described. The results are presented for the phase space associated with the canonical variables as well as for the trace space concerning the geometrical variables. The energy acceptances for both systems are presented and compared. Some special properties of the solenoids are then outlined. (author)