Why are Geiger Mueller counters considered more sensitive compared to ionization chambers?

Geiger Mueller counters are considered more sensitive compared to ionization chambers primarily because of the mechanism of signal amplification they employ. In a Geiger Mueller counter, radiation ionizes the gas within the tube, creating free electrons and positive ions. These primary particles can then lead to further ionization events through a process known as Townsend avalanche, where secondary ionizations are generated from the initial ionization. This multiplication process creates a larger signal output for even a small amount of incoming radiation, allowing for the detection of very low levels of radiation.

This amplification makes Geiger Mueller counters particularly effective at registering low doses that ionization chambers may not detect reliably. In contrast, ionization chambers operate based on the measurement of the total charge produced by ion pairs and do not amplify the signal to the same degree. They are typically more suited for higher radiation levels or for measuring cumulative doses, rather than for detecting low levels of radiation.

While the other options may have their respective roles in radiation detecting, they do not directly address the inherent sensitivity mechanism that makes Geiger Mueller counters advantageous in detecting low levels of radiation.