-12- energy per unit charge and wide spread in the particle energy imply that a device of sufficient transmission and resolution must be quite large and must employ quite high fields, which in turn implies a large, expensive device. It also seems probable that the interpretation of the data obtained from sucha machine would be complicated by a pessible chemical effect on the intensity of the low-charged ion beams obtained. It seems desirable to search for another approach to the problem, reserving the possibility of designing such an apparatus as a last resort. ACKNOWLEDGMENTS The authors wish to express their appreciation to the crew of the LPTR for their aid in performing the experiments and to Mrs, Nancy Sawley and Miss Alice Conover for technical assistance in counting the samples and data reduction. I00184I