Superconducting pion generator for cancer therapy

Recently, a number of measurements of the physical and radiobiological properties of the negative pion have confirmed the advantages of this particle for use in cancer therapy. An obstacle to the introduction of pions into clinical practice is the size and expense of the accelerator required to produce them. The development of a large solid-angle acceptance pion channel reduces the accelerator requirement, and use of a compact recirculated electron linac (500 MeV, 500 μ amp) becomes feasible. The basic magnetic elements of the channel are two 750 bend toroids, each consisting of 60 Nb--Ti wound superconducting pancake coils. The cylindrical design of the channel allows simultaneous multi-port irradiation with 60 controllable beams capable of depositing uniform biological equivalent dose distributions within an irregular-shaped deep-seated tumor. The installation of this system is nearly completed, and initial tests will be carried out at low intensity using the Stanford Mark III accelerator this fall. At a later date, when a high intensity beam becomes available from the recirculated superconducting accelerator, a quick switch will be made to this beam for pre-therapeutic studies. Construction of a prototype clinical pion facility in the Stanford Medical Center is planned, but is contingent on the successful completion of these tests. (U.S.)