SingleReadoutDeadTimeCorrection

Dead time is the time after an event that a detector is not able to detect another event. For a paralyzable detector, an event that happens during the dead time restarts the dead time. For a non-paralyzable detector, the event is simply lost and does not cause additional dead time.

Dead-time correction corrects for detector dead time by weighing the events according to:

\[N = M \frac{1}{(1-\mathrm{rate} \cdot (\frac{t_{\mathrm{dead}}}{t_{\mathrm{bin}}}))}\]

for non-paralyzable detectors and

\[N = M \frac{\mathrm{Re} (\mathrm{W}(-\mathrm{rate} \cdot (\frac{t_{\mathrm{dead}}}{t_{\mathrm{bin}}})) )}{\frac{\mathrm{rate}}{t_{\mathrm{bin}}}}\]

for paralyzable detectors, where

\(N\) = true count
\(M\) = measured count
\(t_{\mathrm{dead}}\) = dead time
\(t_{\mathrm{bin}}\) = TOF bin width
\(\mathrm{rate}\) = measured count rate
\(\mathrm{W}\) = Lambert W function

The class SingleReadoutDeadTimeCorrection is a Mantid-style algorithm for computing the dead-time correction for an event workspace. One can optionally include error events in the dead-time computation.

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	EventWorkspace	Mandatory	Input workspace used to compute dead-time correction
InputErrorEventsWorkspace	Input	EventWorkspace		Input workspace with error events used to compute dead-time correction
DeadTime	Input	number	4.2	Dead time in microseconds
UseDeadTimeThreshold	Input	boolean	False	If True, use a correction of 0 for TOF bins requiring corrections greater than `DeadTimeThreshold`
DeadTimeThreshold	Input, Optional	number	1.5	If `UseDeadTimeThreshold` is True, this is the upper limit for dead-time correction ratios
TOFStep	Input	number	100.0	TOF bins to compute dead-time correction, in microseconds
Paralyzable	Input	boolean	False	If True, paralyzable correction will be applied, non-paralyzable otherwise
TOFRange	Input	dbl list	[0.0, 0.0]	TOF range to use to compute dead-time correction
OutputWorkspace	Output	MatrixWorkspace	Mandatory	Output workspace containing the dead-time correction factor for each TOF bin

Usage

Example using SingleReadoutDeadTimeCorrection

import mantid.simpleapi as mtd_api
from lr_reduction import template
from lr_reduction.DeadTimeCorrection import SingleReadoutDeadTimeCorrection
from lr_reduction.utils import amend_config

mtd_api.config["default.facility"] = "SNS"
mtd_api.config["default.instrument"] = "REF_L"


def test_deadtime(nexus_dir):
"""
Test the time-resolved reduction that uses a measured reference.
It is generally used at 30 Hz but it also works at 60 Hz.
"""
with amend_config(data_dir=nexus_dir):
    ws = mtd_api.Load("REF_L_198409")

algo = SingleReadoutDeadTimeCorrection()
algo.PyInit()
algo.setProperty("InputWorkspace", ws)
algo.setProperty("OutputWorkspace", "dead_time_corr")
algo.setProperty("UseDeadTimeThreshold", True)
algo.setProperty("DeadTimeThreshold", 1.1)

algo.PyExec()
corr_ws = algo.getProperty("OutputWorkspace").value
corr = corr_ws.readY(0)
for c in corr:
    assert c <= 1.1