The experimental characterization of a compact H− cyclotronʹs spiral inflector

There are very few detailed measurements of the optical characteristics of a cyclotronʹs inflector, or of beam properties in the immediate vicinity of an inflector. This scarcity of measured data is largely due to the inaccessibility of a typical inflector. This paper describes an experimental technique developed to make detailed optical measurements in the neighbourhood of an inflector. The technique uses a pinhole collimator, scintillators, a TV camera, image analysis software, and a 1 MeV test cyclotron. Measurements of beamspots and central ray coordinates at key locations before and after the inflector were obtained using the technique. The measured data was compared with beam transport simulations to yield improved models of the injection system and inflector.