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 wavelenght 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 wavelenghts. 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: Algorithms | CorrectionFunctions\InstrumentCorrections