What happens to the voltage in an electret ion chamber as radon decays during testing?

In an electret ion chamber, the principle of operation involves measuring changes in voltage as a result of ionization caused by the decay of radioactive materials, such as radon. As radon decays, it emits alpha particles which ionize the air in the chamber. This ionization creates positive ions and free electrons, which can be collected by electrodes, resulting in an electrical current.

The electret material within the chamber is designed to hold a charge, which diminishes as it interacts with the ionization caused by the decaying radon. As the decay process continues and more ionization occurs, the overall charge on the electret is reduced, leading to a decrease in voltage. This trend indicates that the electret is effectively responding to the radioactivity from the radon decay over time.

Thus, the correct understanding of the relationship between radon decay and voltage in an electret ion chamber reveals that, in response to the ionization caused by radon decay, the voltage indeed decreases.