Preparation of air-settled, roll-thinned phosphorus targets

Red ³¹P targets of 2.6 and 2.9 mg/cm ²±0.1 mg/cm ² with 1-cm×2-cm side dimensions were prepared for a nuclear mass measurement which required good thickness uniformity. The thinner target, with 50 μg/cm ² of gold flashed on both surfaces, withstood a 173-MeV α beam of 175 nA for 18 h. Adaptations will be described for an Indiana University Cyclotron Facility air-settling method used to distribute phosphorus powder, as well as the methods developed for subsequent pressing, roll thinning, and dry release to obtain self-supporting targets. An envelope of gold foil, in contact with the phosphorus during each step, was instrumental in the process.