Abstract
The potential usefulness of stopping negative pion beams in radiotherapy is discussed, with particular reference to their physical properties. A brief history of work in this field is given. A low momentum secondary beam line was constructed to transport pions, produced in a target bombarded with 8 GeV/c protons, to an irradiation area. This facility was primarily intended for radiobiological experiments and physical measurements relevant to pion radiotherapy. The stages of the design of the beam line are outlined and details of performance are given. Radiobiological experiments carried out in the peak, plateau and surface regions are summarised. The biological and physical consequences of the beam's wide momentum bite (13% fwhm) are examined. A detailed description is given of an experiment which measured the relative spectra of secondary particles leaving a carbon surface at the pion stopping peak. Si/Csl counter telescopes measured the relative spectra of protons, deuterons, tritons, He ions and Li ions. An unfolding technique was used to derive the pion capture emission spectra, which are compared with published calculations and experimental data. Suggestions are made for an extended programme of secondary particle measurements.