PDD - Waveforms
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6 Experimental Requirements- 6.1 Time Resolution
- 6.2 Waveforms
- 6.3 Dynamic Range and Linearity
- 6.4 Absolute Amplitude Calibration and Stability
- 6.5 Dead time
- 6.6 Sensitivity of optical modules
- 6.7 Noise Rate and Noise Rate Stability
- 6.8 Failure Rate
- 6.9 IceTop
6.2 Waveforms
Experience with the AMANDA detector for observing electromagnetic showers and high-energy showering muons has demonstrated the significant advantages of using the presently available "reduced" waveform information, like amplitude and time-over-threshold (TOT) rather than amplitude alone. Light scattering results in strong signal dispersion over large distances. This effect dilutes information (namely the precise arrival time of the first photon), but also adds information: The length of the light signal recorded by a single PMT indicates the distance to the light source. Therefore the combination of amplitude and time structure allows one to distinguish between close, dim light sources and distant, bright light sources. The reconstruction of distant tracks and very large high energy showers will therefore require full waveform digitization. For instance, simulations based on TOT alone have demonstrated very poor angular resolution for electromagnetic showers.
Waveforms should be recorded at a rate of ≥ 200 Msps for the first 400 ns in order to obtain good timing and double pulse resolution. For longer times, a lower sampling rate of ≥ 33 Msps is sufficient to tease out structure due to secondary light pulses such as those due to double bangs from ντ events.
The waveform sampling depth should be roughly 4 μs, long enough to capture full waveform information from most (but not all) double bang events.
