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A few references that might be useful for the S2 pulse shape analysis needed to study the gas pocket.
1) Study of the gas pocket through the S2 pulse shape: we are interested in the gas drift time T.
To my understanding this parameter is “easy” to extract from the S2 pulse shape once you select a specific set of events (i.e. those which have a very short drift time in liquid). It can be fit to the average waveform (what I would do) and/or from Davide’s filtered signal.
2) S2 pulse shape was analyzed in DS50 and we have full documentation on its analytical expression. It should be adapted to SiPM response.
We should start from the internal note from Alden (docdb#1237) and references therein.
3) The gas drift time T may have a radial dependence that we can study. We do have information on xy in ReD raw data because we readout 24 single SiPM on the top. Vlad performed several uniformity studies on S2 that might be useful to this purpose. We also do have Kripton data that is uniformly distributed in the chamber.
4) We also took data while forming the gas pocket that might be interesting to look at. See docdb#886 for the exercise done in DS50.
5) Once T as a function of xy is known, you can extract a map of the gas pocket height (dgas) from the velocity (v(Egas)
T = dgas / v(Egas)
In DS50 we got v(E) from Magboltz (an open source code that solves the Boltzmann transport equations with numerical integration in order to simulate the interactions of electrons in gas mixtures under the influence of electric and magnetic fields).
See docdb#1172.
6) As Hanguo pointed out several times, we used this analysis to level the TPC. See the results in docdb#1181. A similar effort will be needed in Proto.
7) Alternative analysis methods exist. For example Chengliang in Princeton used S2/S1 analysis from Masa and compared the radial dependence to G4DS predictions in order to extract the gas pocket height map (see docdb#1161).
I suppose that Paolo and Luciano should be able to do a similar MC study in G4ReD.