Table of Contents
Corrects the time of flight of an indirect geometry instrument by a time offset that is linearly dependent on the wavelength of the neutron after passing through the moderator.
Name | Direction | Type | Default | Description |
---|---|---|---|---|
InputWorkspace | Input | MatrixWorkspace | Mandatory | The name of the input workspace, containing events and/or histogram data, in units of time-of-flight |
OutputWorkspace | Output | MatrixWorkspace | Mandatory | The name of the output workspace |
This algorithm Corrects the time of flight (TOF) of an indirect geometry
instrument by substracting a time offset linearly dependent
on the wavelength of the neutron when emitted through the moderator.
This algorithm is suitable to data reduction of indirect instruments
featuring a neutron flux with a narrow distribution of wavelengths. A
empirical formula for the correction, stored in the instrument
definition file, is taken as linear on the initial neutron wavelength
:
,
(
is in units of microsec/Angstrom and
is in units
of microsec. Below is the example XML code included in BASIS beamline
parameters file.
<!-- Moderator Tzero/LambdaZero Parameters -->
<parameter name="Moderator.TimeZero.Gradient">
<value val="11.967"/>
</parameter>
<parameter name="Moderator.TimeZero.Intercept">
<value val="-5.0"/>
</parameter>
The recorded TOF: , with
This algorithm will replace TOF with
For an indirect geometry instrument, is not known but
the final energy,
, selected by the analyzers is known. For
this geometry:
and with
in units of microseconds.
Putting all together:
, with
[TOF’]=microsec
If the detector is a monitor, then we can treat it as both sample and
detector. Thus, we use the previous formula inserting the time from
sample to detector and with the initial fligh path
as the distance from source to monitor.
Categories: Algorithm Index | CorrectionFunctions\InstrumentCorrections
C++ source: ModeratorTzeroLinear.cpp (last modified: 2019-01-07)
C++ header: ModeratorTzeroLinear.h (last modified: 2018-10-05)