Pi-meson range shifter for clinical therapy

An energy-absorbing instrument, designed for use with a linear accelerator producing a high-intensity beam of negative pions, is described. The system makes use of a variable column of energy-absorbing fluid with depth controlled by a hydraulic servomechanism to conform to theoretically or experimentally derived sweep curves in the form of histograms or continuous functions. The dose-vs-depth curves which result from the vertical sweep of the instrument show excellent flattening over the stroke. The details of construction and control of this ''range shifter'' are described, as well as a unique method for command-function storage and interrupt control using programmable memories and microprocessor techniques