Isochronous 180 degrees turns for the SLC positron system

The design of the compact, achromatic, second-order isochronous 180 degrees turn, for the SLC positron transport system is described. Design criteria require an energy range of 200+or-20 MeV, energy acceptance of +or-5%, transverse admittance of 25 pi mm-mr, and minimal lengthening of the 3 to 4 mm (rms) positron bunch. Optics specifications and theoretical performance are presented and compared to experimental results based on streak camera measurements of bunch length immediately after the first isochronous turn (200 MeV) and positron beam energy spread after S-band acceleration to 1.15 GeV. >