ИСТИНА

The effect of the ionizing radiation field on the behavior of CsI aerosols formed by condensation of supersaturated vapor was examined. Supersaturated CsI vapor was formed by evaporation from a metal surface ohmically heated to high temperatures. The CsI sublimation time at a heater temperature of (800 ± 50)°С at the minimal current passed through the heater was about 15 min at a current of 10–20 А. The radiation field in the chamber was made with a GUG-120 γ-ray installation consisting of 80 60Co ionizing radiation sources of type GIK-7-4 with a total activity of 0.065 MCi. In the ionizing radiation field produced by the GUG-120 γ-ray installation, the flux of γ-quanta per aerosol particle was (5–8)∙1014 s–1. Similar experiments were performed on a stationary electron beam from U-12F (mean current 1000 μA, electron energy Е = 4.0 MeV) and U-003 (mean current 150 μA, electron energy Е = 4.5 MeV) accelerators. In both cases, the absorbed dose was 9 kGy. In the 4–4.5-MeV electron field produced by U-12F and U-003 electron accelerators, the electron flux per aerosol particle was 2∙1013–1014 s–1. A study of the size distribution function of CsI particles showed that, both in the field of 60Co γ-radiation and in a stationary electron beam, three modes of particle size are observed with the mean sizes of 0.13, 0.57, and 0.76 μm. The amount of particles of size 0.13 μm is larger by a factor of ~10–20 than the amount of particles of sizes 0.57 and 0.76 μm. Comparison of the distribution functions of CsI aerosol particles formed by supersaturated vapor condensation in an ionizing radiation field and without it showed that the ionizing radiation affected not only the size but also the amount of particles. The mean size of the particles of the first mode increased from 0.006 to 0.13 μm (by a factor of more than 20), but their number decreased. At the same time, for the second and third modes, the particle size decreased with a simultaneous increase in their relative amount. The particle size decreased from 2.5 to 0.57 μm for the second mode and from 125 to 0.76 μm for the third mode. It should be noted that, in the ionizing radiation field, the particle size practically does not exceed 1.0 μm. That is, under the action of the ionizing radiation, not only the CsI particle sizes become closer, but also the particles of size in the range 0.1–1.0 μm are stabilized.