A pepper-pot emittance meter for low-energy heavy-ion beams

A novel emittance meter has been developed to measure the four-dimensional, transverse phase-space distribution of a low-energy ion beam using the pepper-pot technique. A characteristic feature of this instrument is that the pepper-pot plate, which has a linear array of holes in the vertical direction, is scanned horizontally through the ion beam. This has the advantage that the emittance can also be measured at locations along the beam line where the beam has a large horizontal divergence. A set of multi-channel plates, scintillation screen and ccd camera is used as a position-sensitive ion detector allowing a large range of beam intensities that can be handled. This paper describes the design, construction and operation of the instrument as well as the data analysis used to reconstruct the 4D phase-space distribution of an ion beam. Measurements on a 15 keV He+ beam are used as an example.