Ionization Chamber of Robley Evans |
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This ion chamber was constructed for Robley Evans
at MIT (ca. 1940) for the analysis of breath samples from workers in the
radium industry. It
was desirable that the sample be collected in an uncontaminated room some
distance away from the radium department, preferably with all the windows
open. In addition, the individual providing the sample should not have
participated in radioactive work for the previous three or more hours.
The subject was required to exhale approximately one breath of
every four for a period of ten minutes or so into a one-liter spherical
glass flask.. Information about the collection procedure and the
individual from whom the sample was collected was recorded on data cards.
This information included, among other things, the individual’s name,
information pertaining to their work, calcium-rich foods and beverages in
their diet, and the time, date and supervision of the sample collection. |
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| After the sample had been transferred to the ion chamber, the radon concentration was determined via the current generated by the alpha emissions of the radon and its polonium decay products. A very similar stainless steel ion chamber was produced in the 1950s by the Atomic Instrument Company of Cambridge Massachusetts, the Model 972 Radon Chamber. The latter was 14" high and 8" in diameter, it weighed 15 pounds at operated at 150 volts. | |
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The photograph to the left shows one of the one-liter glass flasks used by Robley Evans to collect breath samples. Evans preferred glass because rubber and other organic materials had a tendency to absorb some of the radon. The photograph also shows two of the data cards used to record information about the individual from whom the sample was collected. Items donated by David Allard |
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References: Evans,
Robley, Radium Poisoning II The Quantitative Determination of the
Radium Content and Radium Elimination Rate of Living Persons, Am. J.
Roentgenol. And Radium Therapy, 37:
368-378, 1937. Evans,
Robley, Protection of Radium Dial Workers and Radiologists from Injury
by Radium, J. Ind. Hygiene and Tox. 25 (7): 253-269, 1943. Evans,
Robley, Apparatus for the determination of minute quantities of radium,
radon and thoron in solids liquids and gases. Rev. Sci. Instr. 6:
99-112, 1935. Evans, Robley, Ionization currents produced by Radon, RaA and RaC in cylindrical ionization chambers. Physical Review 48: 177-186, 1935. U.S. Atomic Energy Commission. RIB-8. Radiation Instrument Catalog No. 3. July 1, 1952. page BIC 15A. |
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