Transverse Beam Containment in the ANL 4-GeV Microtron

Optical systems have been designed to contain the electrons during the acceleration from 0.185-4.0 GeV. These systems are located in the dispersive straight sectionX and maintain a matched dispersion free beam with ß* = 15.0 m in the linac centers, and transverse beam waists in the centers of the dispersive straight sections. A thin-lens code has been developed to design the multi-energy system. Three versions of the focussing systems have been evolved: (i) Two quadrupole triplets for E ¿ 1.62 GeV; (ii) A single triplet for 1.655 ¿ E 2.215 GeV, and (iii) A pentaquad system for E ¿ 2.250 GeV. For case (i) we step the exit edges for the 60° bending magnets so as to simulate a zero degree edge - this reduces vertical defocussing effects to an acceptable value. At the higher energies the exit edge angles are -60°. The entrance angles are 15° on the linac sides of the dipoles. Energy behavior of the Twiss parameters and quadrupole strengths are presented.