This script lives in /reg/g/psdm/tutorials/examplePython/cfd.py and demonstrates how to run a constant-fraction-discriminator algorithm on a waveform (similar to a peak-finder for area-detectors).
from psana import * from pypsalg import find_edges ds = DataSource('exp=amotut13:run=206') det = Detector('AmoETOF.0:Acqiris.0') import matplotlib.pyplot as plt for nevent,evt in enumerate(ds.events()): waveforms,times = det.raw(evt) # find edges for channel 0 # parameters: baseline, threshold, fraction, deadtime, leading_edges edges = find_edges(waveforms[0],0.0,-0.05,1.0,5.0,True) # pairs of (amplitude,sampleNumber) print edges break
Sven Augustin suggested this code to get actual times instead of sample numbers for the edges:
import pypsalg def CFD(x, y, baseline=0.0, threshold=0.1, fraction=1.0, deadtime=5.0, leading_edges=True): if x is None or y is None: return None edges = pypsalg.find_edges(y, baseline, threshold, fraction, deadtime, leading_edges) if not edges.size: return None amplitudes, sample_numbers = edges.T # test whether the last element was found to be a peak, if so ignore it if sample_numbers[-1] >= len(y) - 1: amplitudes = amplitudes[:-1] sample_numbers = sample_numbers[:-1] # separate integer index and linearly interpolated fraction in between indices = sample_numbers.astype(int) linterp = sample_numbers % 1 # get x step size for each index and calculate interpolated x axis steps = x[1:][indices] - x[:-1][indices] times = x[indices] + steps * linterp return times, amplitudes
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