US EPA

2068993 

Journal Article 

Long-Term Stability of Electret Dosimeters 

Pela, CA; Ghilardi, AJP; Ghilardi Netto, T 

1988 

Yes 

Health Physics
ISSN: 0017-9078
EISSN: 1538-5159 

NIOSH/00179435 

54 

6 

669-672 

English 

3378898 

The long term charge stability of cylindrical electret dosimeters under various heat and radiation conditions was assessed in the search for optimum conditions to stabilize the charge. Dosimeters were prepared so that the charges on the various electrets were approximately equal and produced a saturation ion collection field. Dosimeters were stored in a dessicator to avoid effects of humidity. Dosimeter test conditions included heat treatment in the presence and absence of aluminum foil wrapping on the Teflon electret (30 month observation); irradiation versus no treatment (7 month observation); and irradiation after heat treatment versus heat treatment alone (7 month observation). The heat treatment (120 degrees-C for 30 minutes) produced a 3 percent charge reduction; radiation (0.18 millicuries per kilogram) produced a 10 percent decrease. In the absence of radiation, the charge loss during the first month was about 3 percent with little dependence on heat; this loss was smaller in subsequent months, with about a 0.3 percent loss per month without heat and a 0.2 percent loss per month with heat. Previous radiation treatment had no effect on charge stability, nor did aluminum foil wrapping. Charge loss of heat treated dosimeters after the first month was of the magnitude expected due to natural background radiation. The authors conclude that the cylindrical electret ionization chamber could serve as an acceptable long term radiation monitor.