drift time window

[YifanC]

The drift time window is provided as a standalone parameter in the detector configuration file. It is not associated / calculated from the drift distance or electric field, which makes it rather inflexible to change to other detector configuration and prong to errors. To be improved.

[jiangmei-yang]

I wrote a function to retrieve the longest drift time from the response file; should we use this as the value of time_padding or time_window, so we don't need to modify the time window for each different response config;

I don't see why we are having two different parameters time_padding and time_window, they seem to serve the same purpose in detsim.py; we may simply keep one? e.g.

larnd-sim/larndsim/detsim.py

Lines 335 to 336 in 450b5b7

	t0 = abs(z - detector.TPC_BORDERS[t["pixel_plane"]][2][0]) / detector.V_DRIFT - detector.TIME_WINDOW
	if not t0 < time_tick < t0 + detector.TIME_WINDOW:

and

larnd-sim/larndsim/detsim.py

Lines 428 to 430 in 450b5b7

	t0 = abs(z - detector.TPC_BORDERS[t["pixel_plane"]][2][0]) / detector.V_DRIFT - detector.TIME_WINDOW
	if not t0 < time_tick < t0 + detector.TIME_WINDOW:

these are the only places that TIME_WINDOW being used.

[jiangmei-yang]

There are some small inconsistency on the same parameters among different functions:
In drifting.py,

larnd-sim/larndsim/drifting.py

Line 57 in 450b5b7

track["t_start"] += min(drift_start, drift_end) / detector.V_DRIFT + track["t0"]

track["t_start"] = (shorter drift time) + track["t0"], but in detsim.py, tracks_current_mc,

larnd-sim/larndsim/detsim.py

Line 300 in 450b5b7

t_start = round((t["t_start"]-t["t0_start"]-detector.TIME_PADDING) / detector.TIME_SAMPLING) * detector.TIME_SAMPLING

, when it tries to go back to (shorter drift time) = track["t_start"] - track["t0_start"];

so in drifting.py should we also subtract track["t0_start"]: track["t_start"] = (shorter drift time) + track["t0_start"]

larnd-sim/larndsim/drifting.py

Lines 57 to 58 in 450b5b7

	track["t_start"] += min(drift_start, drift_end) / detector.V_DRIFT + track["t0"]
	track["t_end"] += max(drift_start, drift_end) / detector.V_DRIFT + track["t0"]

and similarly: track["t_end"] = (longer drift time) + track["t0_end"]

[jiangmei-yang]

larnd-sim/larndsim/detsim.py

Line 39 in 450b5b7

t_end = round((track["t_end"] + 1) / detector.TIME_SAMPLING) * detector.TIME_SAMPLING

What is this + 1 for? Looks like a very arb. padding value and not being used when calculating time elsewhere