ModeratorTzero v1¶
Summary¶
Corrects the time of flight of an indirect geometry instrument by a time offset that is dependent on the energy of the neutron after passing through the moderator.
See Also¶
Properties¶
Name |
Direction |
Type |
Default |
Description |
---|---|---|---|---|
InputWorkspace |
Input |
Mandatory |
The name of the input workspace, containing events and/or histogram data, in units of time-of-flight |
|
OutputWorkspace |
Output |
Mandatory |
The name of the output workspace |
|
EMode |
Input |
string |
Indirect |
The energy mode (default: Indirect). Allowed values: [‘Indirect’, ‘Direct’, ‘Elastic’] |
tolTOF |
Input |
number |
0.1 |
Tolerance in the calculation of the emission time, in microseconds (default:1) |
Niter |
Input |
m |
1 |
Number of iterations (default:1) |
Description¶
Corrects the time of flight (TOF) by a time offset that is dependent on the energy of the neutron after passing through the moderator. A heuristic formula for the correction is stored in the instrument definition file. Below is shown the entry in the instrument file for the VISION beamline:
<!-- formula for t0 calculation. See http://muparser.sourceforge.net/mup_features.html#idDef2 for available operators -->
<parameter name="t0_formula" type="string">
<value val="(incidentEnergy < 34.7332) ? 37.011296*incidentEnergy^(-0.052874) : (incidentEnergy < 88.7556) ? 124.267307*incidentEnergy^(-0.394282) : (incidentEnergy < 252.471) ? 963.775145*incidentEnergy^(-0.850919) : (incidentEnergy < 420.145) ? 33.225834*incidentEnergy^(-0.242105) : (incidentEnergy < 100000.0) ? 120.569231*incidentEnergy^(-0.455477) : 0.0" />
</parameter>
The recorded
: emission time from the moderator : time from moderator to sample or monitor : time from sample to detector
This algorithm will replace
For a direct geometry instrument, the incident energy
, a function of the incident energy with the distance from moderator to sample, and the initial unknown velocity ( ) with the distance from sample to detector, and is the final fixed velocity ( )
Note
We obtain
Here’s the result of applying ModeratorTzero to both the event list and the histogrammed data of a run in the VISION beamline. The transformation of either events or histograms shifts the curve to smaller TOF’s. The transformed curves are not supposed to be identical, but similar and differentiated from the original curve.
For indirect instruments featuring an incoming neutron flux having a
sufficiently narrow distribution of energies, a linear relationship
between
Categories: AlgorithmIndex | CorrectionFunctions\InstrumentCorrections
Source¶
C++ header: ModeratorTzero.h
C++ source: ModeratorTzero.cpp