response time, \(\tau_{\text{R}}\)

of a detector
Also contains definition of: rise time
of a radiation detector
https://doi.org/10.1351/goldbook.R05345
The time required for the detector output to go from the initial value to a percentage (e.g. 99%) of the final value. In the case of an exponential behaviour of the detector \(\tau _{\text{R}}\) can be related to the time constant \(\tau _{\text{c}}\). The rise time \(\tau _{\text{r}}\) is the time required for the detector output to vary between given percentages (e.g. from 10% to 90%) of the final value. Similarly, the fall time \(\tau _{\text{f}}\) is the time required for the detector output to vary between given percentages (e.g. from 90% to 10%) of the initial value.
Source:
PAC, 1995, 67, 1745. 'Nomenclature, symbols, units and their usage in spectrochemical analysis-XI. Detection of radiation (IUPAC Recommendations 1995)' on page 1751 (https://doi.org/10.1351/pac199567101745)