Editing Dead time (section)

==Overview==
The total dead time of a detection system is usually due to the contributions of the intrinsic dead time of the detector (for example the ion drift time in a [[gaseous ionization detector]]), of the analog front end (for example the shaping time of a spectroscopy amplifier) and of the [[data acquisition]] (the conversion time of the [[analog-to-digital converter]]s and the readout and storage times).

The intrinsic dead time of a detector is often due to its physical characteristics; for example a [[spark chamber]] is "dead" until the potential between the plates recovers above a high enough value. In other cases the detector, after a first event, is still "live" and does produce a signal for the successive event, but the signal is such that the detector readout is unable to discriminate and separate them, resulting in an event loss or in a so-called "pile-up" event where, for example, a (possibly partial) sum of the deposited energies from the two events is recorded instead. In some cases this can be minimised by an appropriate design, but often only at the expense of other properties like energy resolution.

The analog electronics can also introduce dead time; in particular a shaping spectroscopy amplifier needs to integrate a fast rise, slow fall signal over the longest possible time (usually 0.5–10 microseconds) to attain the best possible resolution, such that the user needs to choose a compromise between event rate and resolution.

Trigger logic is another possible source of dead time; beyond the proper time of the signal processing, spurious triggers caused by noise need to be taken into account.

Finally, digitisation, readout and storage of the event, especially in detection systems with large number of channels like those used in modern High Energy Physics experiments, also contribute to the total dead time. To alleviate the issue, medium and large experiments use sophisticated pipelining and multi-level trigger logic to reduce the readout rates.<ref>{{cite report|title=ALICE DAQ and ECS Manual |date=December 2010  |url=https://ph-dep-aid.web.cern.ch/ph-dep-aid/dateUserGuide/dateUserGuide.pdf |type=ALICE Internal Note/DAQ ALICE-INT-2010-001 |first1=F. |last1=Carena |first2=W. |last2=Carena |display-authors=1}}</ref>

From the total time a detection system is running, the dead time must be subtracted to obtain the [[live time]].