EQSANSDarkCurrentSubtraction v2¶

EQSANSDarkCurrentSubtraction dialog.

Table of Contents

Summary
Properties
Description
Source

Summary ¶

Perform EQSANS dark current subtraction.

Properties ¶

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory
Filename	Input	string	Mandatory	The name of the input event Nexus file to load as dark current. Allowed extensions: [‘_event.nxs’]
OutputWorkspace	Output	MatrixWorkspace	Mandatory
PersistentCorrection	Input	boolean	True	If true, the algorithm will be persistent and re-used when other data sets are processed
ReductionProperties	Input	string	__sans_reduction_properties
OutputDarkCurrentWorkspace	Output	MatrixWorkspace
OutputMessage	Output	string

Description ¶

Subtract the dark current from an EQSANS data set. This algorithm is rarely called directly. It is called by SANSReduction.

This workflow algorithm will:

Properly load the dark current data set
Normalize the dark current to the data taking period
Subtract the dark current from the input workspace

The dark current is subtracted pixel by pixel by normalizing the dark current data by counting time. The total number of dark current counts $N_{dc}(i)$ for each pixel i is obtained by integrating over all time of flight bins. For a given pixel and wavelength bin, the corrected signal is given by:

$I'(i,\lambda_j)=I_{data}(i,\lambda_j)-N_{dc}(i) \ \ \frac{T_{data}}{T_{dc}} \ \ \frac{t_{frame}-t^{low}_{cut} - t^{high}_{cut}}{t_{frame}} \ \ \frac{\Delta\lambda_j}{\lambda_{max}-\lambda_{min}}$

where the T-values are the counting times for the data set and the dark current (dc). The $t_{cut}$ values are the TOF cuts at the beginning and end of a frame. $t_{frame}$ is the width of a frame. $\Delta\lambda_j$ is the width of the wavelength bin we are considering.