Range-energy relations for protons in nickel
Farmer, Bobby Joe
Bonner, T. W.
Master of Arts
The primary objective of this study was to determine by experimental methods a range-energy relation for protons in nickel, the energy range covered being between approximately 2 and 5 Mev. Nickel is often used for target backings and in other phases of nuclear research in which accurate values of particle energy absorption are required. Since no experimental data for ranges or energy loss in this metal were available in this energy range, it is apparent that such information would be very useful. The first determinations of ranges were carried out with monoenergetic alpha-particles produced by the disintegration of radioactive nuclei, this being the only source of high energy charged particles available at the time. Later, similar measurements were made with monoenergetic proton beams from particle accelerators. The method of determining the range of these particles in a particular substance was to introduce very thin layers of the material between the source and a detector until the transmission reached zero. Then a plot of the transmission as a function of the absorber thickness was obtained, from which the mean range, i.e., the range at which 50% transmission occurred, was determined. Due to the inaccuracy in determining the thicknesses of the thin foils, a high degree of accuracy could not be obtained with this method. With the advent of charged particle accelerators which utilized analyzing magnets, a source of a variety of charged particles became available. Since the energy of the particle beam is variable, we are given a new and more easily utilized method of mean range measurements. One may now use a single foil of the absorbing material, and instead of using the absorber thickness as the variable, use the energy of the particle beam. A transmission curve is then obtained which gives the transmission as a function of the energy. This method is more accurate in that the thickness of only one thick foil must be determined instead of many thin foils as was necessary in the earlier method. If a sufficient number of data points are obtained, one may find an empirical relation between the ranges and energies of the particles. Then upon differentiation of this relation, the rate of energy loss of the particle may be determined. This energy loss may then be compared with existing theories, a treatment of which is given in the next section.