H− magnetic beam extractors design for the KOMAC project

Complete design specifications for 260 MeV H− beam extractors are presented. The extractor employs a novel design of a stripper magnet which separately handles both the stripping of the H− beam and the bending of the unextracted H− beam. The design objective of the extractor is to partially extract a negative hydrogen ion (H−) beam at 260 MeV from the main linac where both protons (H+) and negative hydrogen ions are accelerated up to 1 GeV. Since the extractor adopts the magnetic stripping method, emittance growth is unavoidable for the extracted beam. However, the unextracted H− beam returns to the main linac with no change in the beam profile. The main features of this extractor are: (1) its ability to regulate the intensity of the extracted beam and (2) the nondestructive effect on the profile of the H− downstream beam. These extractors will be utilized for the Korea Multi-purpose Accelerator Complex (KOMAC) linear accelerator of 1 GeV cw proton (H+)/negative hydrogen (H−) beams with an intensity of 20 mA.