fe teA ie on ee a ee, mommies Atmospheric Storage of Strontium The atmosphere has been sampled at various altitudes to estimate |. Sr70 presently stored in suspended form. Methods of Sampling Lower Atmosphere (200 feet) —- Samples were collected at 15 cubicfeet per minute through an MSA Comfo filter which has an fefficiency of over 90% at 0.3 micron. The samples were collected on the roo New York Operations Office. Samples have been collected continuo 12/21 - 28/53. Tropopause (35 - 42,000 feet) -= The region of the tropop been sampled by a aircralt equipped with celluloses filters. Dup cate samples are collected at a flow of approximately 6000 cubic minute, The efficiency of collection of the filter paper appears the range 90-95% (Appendix B ). Four flights have been completed Stratosphere (lO - 100,000 feet}-- It was necessary for tre Laboratory to design and ctuild special equipment for sampling in this region[of the atmosphere from which dust had not previously been collected. Although many devices are available for dust sampling in the lower atmosphere, the problems presented in the sampling at 100,000 feet make these Hevices entirely unsuitable. Preliminary calculations based on the best dstimates of expected concentration of activity set the requirement of volume air to be Sampled at approximately 1000 cubic meters. Since the only practikal means of attaining this altitude is by means of non-extensible helium filled balloons, consideration of weight of the sampler and its self-contained power supply were of great import. These factors in addition to the great reduction in air pressure and temperature at this altitude prompted the investigation of electrostatic precipitation for the solution of this problem. The most inviting feature of the electrostatic precipitator is tha free passage of air through the device without restriction allowing tha air moving efficiency. At these altitudes, the ease of producing greatest orona ioniza- tion without the use of excessively high voltages greatly reduces quirements in the charging device, he power re= Preliminary tests in an evacuated bell jar demonstrated the feasibti obtaining contolled corona discharge restricted to a small region central wire at this pressure by using a quasi-constant current p Calculations indicated reasonable dimensions would efficiently p the dusts of interest. Figure 11 illustrates the basic features of the device. It consisks of four sections of 4" 0.D. by 1/16" wall aluminum tubing each 13" long. [he first section contains an insert 8" long reducing the inner diameter to P.785%, A nichrome wire .012" in diameter is supported on an insulator andj runs centrally