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Parameters have been specified for electron beams with energies 5--45 MeV from a Brown Boveri betatron for use in computerised dosimetry calculations. A semi-empirical equation is given for the dose at any point at various depths in water. This equation is a modification to Kawachi's predictive model which was based on solutions of a general age--diffusion equation. The depth doses and isodose curves are predicted as a function of the practical range, source skin distance (SSD) and field size. Depth dose accuracy requirements of +/-2% above 50% depth dose and +/-5% at lower doses, relative to maximum dose, have been set and achieved. Also, the shape of the isodose curves with the constrictions at higher doses and bulging at lower values are accurately predicted. Computer calculated beams have been used to generate summed isodose distributions for certain clinical situations.

A 240 MeV electron storage ring has been in operation at the Physical Sciences Laboratory of the University of Wisconsin for one year. The storage ring injector is a 50 MeV FFAG electron synchrotron. The bunched beam from the synchrotron is injected into the storage ring in a single turn. Radio-frequency capture is accomplished by using the signal from the bunched beam as the master oscillator during capture. Using this method, high capture efficiency is achieved. A useful consequence of the method of radio-frequency capture is the damping of the coherent synchrotron oscillation instability. The beam may be accelerated, or decelerated, to any energy within the capability of the ring -10 MeV to 240 MeV. The vacuum system operates at a pressure in the mid 10-10 range allowing lifetimes of many hours for low intensity beams. During the first year of operation several interesting effects have been observed. Among these were photo etching of metal from the vacuum chamber by synchrotron radiation and enhanced beam loss due to scattering from ions trapped in the electron beam. The beam also exhibits a transverse coherent instability that violates the Courant-Sessler criteria for stability.