Measurement of the four-dimensional transverse emittance of an ion beam

Abstract

A pepper-pot emittance measurement system has been developed for measuring the four-dimensional transverse emittance of an ion beam. The complete emittance can be constructed by stepping a graphite pepper-pot mask through a cross section of the beam and taking two-dimensional profiles of its images. The profiles are measured by moving a set of thin collectors (0.6 mm wide and 0.4 mm apart) stacked vertically on a ceramic board through a cross section of the beam. A high-resolution capability of 1.6 mm by 1.3 mrad has been demonstrated for beam widths of 50 mm and divergence angles up to 75 mrad. An adaptive algorithm has been developed to match the pepper-pot holes to their corresponding images without imposing any bounds on the divergence or direction of the beam.