Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Performance of Electret Ionization Chambers in Magnetic Field



P Kotrappa, L R. Stieff, Timothy F. Mengers, Robert McMichael, Robert D. Shull


Electret Ionization Chambers (EIC) are widely used for measuring radon and radiation. The radiation measured includes alpha, beta and gamma radiation. These detectors do not have any electronics and as such can be introduced into magnetic field regions. It is of interest to study the effect of magnetic fields on the performance of these detectors. Relative responses are measured with and without magnetic fields present. Quantitative responses are measured as the magnetic field is varied from 8 kA/m to 796 kA/m (100 Oersted to 10,000 Oersted). No significant effect is observed for measuring alpha radiation and gamma radiation. However a significant systematic effect is observed while measuring beta radiation from a 90 Sr-Y source. Depending upon the field orientation, the response increased from 1.0 to 2.7 (vertical position) and decreased from 1.0 to 0.60 (horizontal position). This is explained as due to the setting up of a circular motion for the electrons by the magnetic field, which may increase or decrease the path length in air depending upon the experimental configuration. It is concluded that these ionization chambers can be used for measuring alpha and gamma radiation in magnetic fields. However, caution must be exercised if measuring beta radiation. The most important application of the EIC is in measuring radon in air. Since radon is an alpha emitter, these detectors can be used for measuring radon in magnetic fields.
Radiation Protection Dosimetry


alpha, beta and gamma radiation, Electret Ionization Chambers (EIC)


Kotrappa, P. , Stieff, L. , Mengers, T. , McMichael, R. and Shull, R. (2006), Performance of Electret Ionization Chambers in Magnetic Field, Radiation Protection Dosimetry, [online], (Accessed June 17, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created April 6, 2006, Updated October 12, 2021