Pulse Integral¶
Note: some of the following text was taken from Walter Ogburn's doctoral thesis.
Overview¶
This routine is applied primarily to phonon pulses. Users may apply this routine to the charge channels, but in general the charge optimal filter routines provide far superior energy estimation so in practice this is never applied to charge pulses.
The integral if found by first subtracting the pre-pulse baseline, then rolling off the trace with a low-pass filter and integrating. The integral provides a more linear energy estimator, less strongly affected by position dependence and saturation effects than the optimal filter routine prior to application of the position correction. The drawback is that the integral routine is more sensitive to noise and has inferior energy resolution for small pulses. The integral energy estimator is often used to study very high energy, saturating events, such as those from alpha particles.
This routine was implemented to roughly follow a similar routine in Darkpipe. The original Darkpipe routine implemented a high-pass filter of very low frequency (~100 Hz), however it is unclear how beneficial this was (Soudan pulses are 1.6 ms long, suggesting that there isn't much content in the signal at 100 Hz). The implementation of a high-pass butterworth filter in BatRoot also struggled with filtering the Soudan traces at such low frequencies. Consequently the Darkpipe filtering was replaced with a low-pass butterworth filter to remove high frequency components. The PulseIntegral currently uses the same filtering parameters as the ConstFreqRTFTWalk.
Future Improvements / Extensions¶
Some studies can be made to determine what could be gained from reinstating the high pass filtering. Some work could also be done to improve the boundary handling ability in the high-pass filtering routine at low frequencies.