Summary of the Symposium

Abstract

S. CURTIS: I have the pleasure of introducing Dr. Tobias. It is very fitting for Toby to be giving the summary of this symposium. If there is anyone who deserves to be called the father of heavy charged particle biophysics, I believe it is he. From the very early days, just after heavy galactic cosmic rays were discovered, he predicted that these might be detected by astronauts who would see flashes of light-which did turn out to be the case. All through his career he has shown an insight into the field of heavy charged particle biophysics that is truly remarkable. And in characteristic style he told me yesterday that he would not be able to come on the cruise last night because he felt he had to work on today's talk. I take great pleasure in introducing the honorary chairman of this symposium, Dr. Cornelius Tobias, to give the summary. C. A. TOBIAS: Let me first summarize some general thoughts about the field of heavy ions. Heavy charged particles are part of our universe. This has been known only since 1948 when Phyllis Freier and group first discovered galactic heavy ions in high-altitude balloon flights. Low-energy accelerated heavy ions (7 MeV/u) became available at the HILAC in the early 1950s, and the Bevalac has been used to accelerate particles up to krypton since 1975. The entire spectrum of heavy ions became available only in 1982 when GSI and LBL successfully accelerated any of the nuclei in the periodic table, including uranium. I believe it is good for us all to remember that this was only 3 years ago, and unless we plan wisely for the future of biomedical heavy ion research, the heavy-ion accelerators might shut down when they have served their purpose for physics and chemistry research. Second, we may state that we have no surefire method to predict what heavy particles can do without actually performing experiments using heavy beams. It is not possible to reproduce or calculate accurately either the spatial pattern of ionization or the temporal complexity of early chemical events in particle tracks. With present-day techniques one could not put a heavy ion track together from a beam of electrons: practically this is not feasible because one would need such a fantastically intense electron beam that the electrons would repulse each other and scatter away. Temporally if you try to put two electrons next to one another, these particles would have to follow within 10-16 s. Dr. Paretzke mentioned that one would need an extremely high electron beam intensity to achieve this. Third, as was shown during the symposium, it is important to have heavy particle beams to be able to explore what they can contribute to medicine. Our entry into space and the eventual colonization of space by man requires the understanding of the magnitude and nature of the deleterious effects of heavy ions. Dr. Lett and Dr. van der Kogel demonstrated that cataractogenesis and the effects of