Instrument for measuring total alpha particle energies of alpha emitters in ambient air

This paper describes the design, fabrication, testing and evaluation of a s elf-reading, carbon fiber, electrometer-type instrument. It is used for mea suring the total energy of alpha particles emitted in air by progenies of R n-222 (Po-218, Pb-214, and Bi-214), and sometimes by other types of alpha e mitters (e.g. Pb-212, U-238 and Pu-239). The purpose of these measurements is to assess the energy delivered by alpha emission from these sources to t he lung tissue. A sample (charged progenies attached to aerosols) is collec ted on filter paper from a known volume of air and placed on the instrument . The discharge rate indicates the alpha energy in MeVl(-1) of air per min that is produced by the alpha emitters. The calibration procedure shows tha t the instrument has an energy sensitivity for alpha particles of 800.5 MeV /scale unit. The range of the readout scale is 30 units. Measurements of al pha contamination in air were made using this instrument in buildings, priv ate homes and in a standard chamber. The value of the radon concentration i n this chamber is traceable back to the US Environmental Protection Agency (EPA) and to the National Institute of Standards and Technology (NIST). (C) 2000 Elsevier Science B.V. All rights reserved.