Abstract: A passive radon surface flux monitor has a dome with an open base having a radial flange and a top opening where an electret can be threaded. Attached to and extending below the open base of the dome is a metal collar that supports the dome when placed on the ground. The collar holds a conductive screen against the radial flange. The conductive screen permits diffusion of gas including radon, thoron, and their daughter products into the dome. A thin paper diaphragm on the conductive screen prevents dust from entering the dome. Sealant seals the connection of the collar, screen, flange, and diaphragm to prevent lateral loss of radon. A collar is pressed partially into the ground at a suitable site and an electret is threaded into the top opening. After a time, the electret is removed and its change in voltage measured.

Abstract: A new type of radon progeny monitor called an electret radon progeny integrating sampling unit (E-RPISU) using an electret ion chamber to measure radon progeny concentration. A conventional 1 LPM particulate air sampling system is used to collect the radon progeny on a roughly 3.5 cm2 filter that is mounted on a side of an electret ion chamber such that the collected progeny are exposed to the inside of the chamber. Alpha radiation emitted by the progeny collected on the filter ionizes the air in the approximately 220 ml chamber. Ions of opposite polarity collect on the surface of the electret of suitable thickness and reduce its surface voltage. A specially built surface voltmeter is used to measure the electret voltage before and after sampling. The electret voltage drop that occurs during the sampling period is proportional to the time integrated progeny concentration. A similar unit with a screen in the place of filter is used to measure unattached progeny concentration.

Abstract: A gamma radiation compensated radon measurement system includes a housing and cooperating tube assembly that define a first, larger sensing volume and second, smaller sensing volume, each of which includes an electrically charged electret. When in its operative configuration, the first and second volumes are in communication with one another so that both volumes are exposed to the same radon concentration as well as the same gamma radiation. A partition separates the two sensing volumes so that ions formed in one sensing volume do not enter the other sensing volume. The two electrets are exposed to their respective sensing volumes to accumulate ions at different rates determined by the design characteristics of the two sensing volumes. The response characteristic of each electret/sensing volume combination is mathematically modelled and the radon and/or gamma concentration is be determined by simultaneously solving the characteristic equations for each electret/sensing volume combination.

Abstract: A small enclosed ion chamber with an electrostatically charged electret attached to the inner chamber wall. Filtered holes in the chamber permits radon in the ambient air in the chamber to enter or exit by diffusion. Positive or negative ions (depending on the polarity of the electret charge) formed in the chamber air by the passing of gamma radiation or X-rays move to and collect on the electret surface by virtue of its electrostatic attraction to ions of opposite polarity. These ions neutralize the ions of opposite polarity on the electret and cause a measurable reduction in its surface voltage which reduction is proportional to the dose of gamma and/or X-ray incidence on the chamber. The reduction of the electret surface voltage is used to calculate the dose of gamma or X-ray radiation incident upon the chamber during a known exposure period.

Abstract: A programmable controlled-exposure radon measurement system includes a radon detector of the type that is programmably inhibited or enabled at selected times to effect randon measurement. In the preferred embodiment, a radon detector of the type having an electret within a chamber is located at the test site and the container opened and closed to the ambient atmosphere at selected times to limit exposure to certain intervals during the day for a selected number of successive days. The container is opening by an actuator, such as an electro-actuator or a fluidic actuator, under the control of a programmable controller, such as a 7-day timer or a stored program controlled microprocessor. A fail-safe function is provided by which the radon detector is inhibited in the event of a power failure to preserve test data up to the time of the power failure.

Abstract: An electret ion chamber based radon monitor is employed as a method of measuring radium-226 and dissolved radon-222 concentrations in water. The procedure consists of taking a known volume of water and placing it in a container of known volume and determining the equilibrium radon concentration in the air phase above the water using an electret ion chamber radon. The radon concentration in the original water sample is calculated from the radon concentration of the air phase. A detailed theory is proposed and experimental results reported. Given a 200 ml water sample, it is typically possible to measure radon concentration of 160 pCi/l with an accuracy of 10% in a one day measurement. One pCi/l of Ra-226 can be also determined with an accuracy of 10% over a 10 day period.

Abstract: A small enclosed ion chamber with an electrostatically charged electret attached to the inner chamber wall. Positive or negative ions (depending on the polarity of the electret charge) formed in the chamber air by the passing of gamma radiation or X-rays move to and collect on the electret surface by virtue of its electrostatic attraction to ions of opposite polarity. These ions neutralize the ions of opposite polarity on the electret and cause a measurable reduction in its surface voltage which reduction is proportional to the dose of gamma and/or X-ray incidence on the chamber. The reduction of the electret surface voltage is used to calculate the dose of gamma or X-ray radiation incident upon the chamber during a known exposure period. In the preferred embodiment, filtered holes in the chamber permit radon to diffuse out of the ion chamber.

Abstract: An electret ion chamber for monitoring radon comprises a housing having an electret holder and a cover. The cover is attached to a plunger which closes over the electret when the cover is in place and is removed from the electret when the cover is opened. The plunger effectively turns "on" and "off" the radon monitor with the opening and closing of the cap. In very short term and very long term radon monitors, this turn on and off feature is not needed.

Abstract: A sensitive radon monitor has a container with a flat bottom and an upwardly and outwardly extending truncated conical side wall terminating upwardly in a relatively large upper edge. A cover overlies the upper edge. The cover has a disk-shaped plate with holes in a circular arrangement. A filter is placed atop the disk and a retainer ring overlies a peripheral portion of the filter and the disk. A negatively charged electret is held against an underside of a central position on the disk, and a detector is held upward against the electret. A second positively charged electret lines the inside of the cup-shaped base. Ambient gases flow into and out of the container through the filter and through the holes in the cover disk. The filter removes liquid and solid particles flowing through the opening establish an equilibrium. Radon decays within the chamber and positively charged products of the decay are attracted and repelled toward the first electret and toward the detector.

Abstract: A small enclosed chamber with an electrostatically charged electret attached to the inner chamber wall. A filtered hole in the chamber permits radon or other radioactive gas to enter by diffusion. Positive or negative ions (depending on the polarity of the electret charge) formed in the chamber air by the decay of the radioactive gas move to and collect on the electret surface by virtue of its electrostatic attraction to ions of opposite polarity. These ions accumulate and cause a measurable reduction in the surface voltage of the electret which reduction is proportional to the time integrated concentration of the radioactive gas in the chamber. The electret surface voltage of the reduction value is used to calculate the average concentration of the radioactive gas during the exposure period. The electret thickness and chamber volume can both be increased to increase the sensitivity of the invention to radioactive gases such as radon, tritium or carbon-14 dioxide or such other radioactive gases.

Abstract: Radioactive gas, particularly radon, is measured in the subsoil environment by electrostatically charging one or two electrets and placing the electret(s) within a chamber having openings protected by a filter which permits gas to flow through the openings while preventing particles from flowing through the openings. The chamber with the electrostatically charged electret(s) and the detector is placed in a receiver formed within the hollow wall of an elongated probe. Foam cushions surround the chamber and assist in the filtering. An open material, such as steel wool, holds the foam in place and the next lower section of the probe holds the steel wool in place. When sampling is done at only one level, the next lower section is the soil moving nose of the probe. Holes in the side wall near the nose admit subsoil gas into the receiver.