A gauge that is configured to detect a time at which radiation enters the gauge. The gauge may include a member that is configured to transition from a first state to a second state upon receipt of the incoming radiation, and may include a light probe that is configured to detect when the member transitions to the second state. The gauge may provide for determining a time of arrival of the radiation at another gauge. For example, the gauge may correlate the time of arrival at the gauge with the another gauge, thereby providing for correlating a response time of a test specimen with actual exposure time of the test specimen to radiation (e.g., an ion beam).

A gauge that is configured to detect a time at which radiation enters the gauge. The gauge may include a member that is configured to transition from a first state to a second state upon receipt of the incoming radiation, and may include a light probe that is configured to detect when the member transitions to the second state. The gauge may provide for determining a time of arrival of the radiation at another gauge. For example, the gauge may correlate the time of arrival at the gauge with the another gauge, thereby providing for correlating a response time of a test specimen with actual exposure time of the test specimen to radiation (e.g., an ion beam).