Method of and apparatus for measuring the mean concentration of thoron and/or radon in a gas mixture

Patent · Mon Jan 01 04:00:00 EST 1990

OSTI ID:867626

Lucas, Henry ^[1]

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1. P.O. Box 1454, Sedona, AZ 86336

A method of and an apparatus for detecting and accurately measuring the mean concentrations of .sup.222 Rn and .sup.220 Tn in a gas mixture, such as the ambient atmosphere in a mine, is provided. The apparatus includes an alpha target member which defines at least one operative target surface and which is preferably fabricated from a single piece of an alpha particle sensitive material. At least one portion of the operative target surface is covered with an alpha particle filter. The uncovered and filter covered operative surface is exposed to the gas mixture containing the .sup.222 Rn and .sup.220 Tn. In the radioactive decay series of these isotopes the maximum kinetic energy emitted by the alpha decay of .sup.222 Rn is about 1.1 MeV less than the maximum kinetic energy emitted by the alpha decay of a .sup.220 Tn. The alpha particle filter has a predetermined mass per unit area of the covered portion of the operative target surface that prevents penetration of alpha particles which originate from .sup.222 Rn decay, but which allows passage therethrough of the maximum kinetic energy alpha particles from .sup.220 Tn decay. Thus, a count of the alpha particle tracks in the uncovered portion of the target member is proportional to the mean concentration of sum of .sup.222 Rn and .sup.220 Tn in the gas mixture, while the count of alpha tracks in the target member under the filter is proportional to the concentration of only the .sup.220 Tn in the gas mixture.

• Research Organization: Argonne National Laboratory (ANL), Argonne, IL
• Assignee: Lucas, Henry (P.O. Box 1454, Sedona, AZ 86336)
• Patent Number(s): US 4975574
• OSTI ID: 867626
• Country of Publication: United States
• Language: English

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