TWO MAGNET ASYMMETRIC DOUBLY ACHROMATIC BEAM DEFLECTION SYSTEM

摘要

TITLEA TWO MAGNET ASYMMETRIC DOUBLYACHROMATIC BEAM DEFLECTION SYSTEMINVENTORRonald M. HutcheonABSTRACT OF THE DISCLOSUREThe beam deflection system includes two dipolemagnets for deflecting a charged particle beam in adeflection plane. The first magnet bends the beam in a pathhaving a radius P1 and a deflection angle .theta.1 greater than180°. The first magnet has an effective exit edge at anangle (90° - ?1) with respect to the beam path. The secondmagnet further bends the beam in a path having a radius P2and a deflection angle .theta.2 where 225° ? (.theta.1 + .theta.2) ? 280°. Theeffective entry edge of the second magnet is at an angleof (90° - ?2) to the beam path. In the usual practical casethe effective interior edges of the two magnets are roughlyparallel, that is, ?1 ? -?2 and the doubly achromaticproperties are obtained to first order when the anglessatisfy the following formula:?1 ? -?22?2 ? .theta.2 -(.theta.1 - 180°),and when the distance D between the effective edges of thetwo magnets is set so that the dipoles produce equal beamdispersion in the drift distance between them. For thecase of 270° total bend with P2 = P1 this occurs at adistance D, given by .