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DepolarizedAnalyserTransmission v1¶

Summary ¶

Calculate the transmission rate through a depolarized He3 cell.

Properties ¶

Name	Direction	Type	Default	Description
DepolarizedWorkspace	Input	MatrixWorkspace	Mandatory	The fully depolarized helium cell workspace. Should contain a single spectra. Units must be in wavelength.
EmptyCellWorkspace	Input	MatrixWorkspace	Mandatory	The empty cell workspace. Must contain a single spectra. Units must be in wavelength
TEStartingValue	Input	number	0.9	Starting value for the empty analyser cell transmission fit property T_E.
PxDStartingValue	Input	number	12.6	Starting value for the depolarized cell transmission fit property pxd.
StartX	Input	number	1.75	StartX value for the fit.
EndX	Input	number	14	EndX value for the fit.
IgnoreFitQualityError	Input	boolean	False	Whether the algorithm should ignore a poor chi-squared (fit cost value) of greater than 1 and therefore not throw an error.
OutputWorkspace	Output	TableWorkspace	Mandatory	The name of the table workspace containing the fit parameter results.
OutputFitCurves	Output	MatrixWorkspace		The name of the workspace containing the calculated fit curve.
OutputCovarianceMatrix	Output	TableWorkspace		The name of the table workspace containing the calculated non-normalised covariance matrix from the fit.

Takes a pair of normalised, single-spectra workspaces representing a depolarized helium cell and the empty cell. It will then determine the empty cell transmission value, T_E, and the cell path length multiplied by the gas pressure pxd by using an exponential fit. The parameters table is then output for use in later calculations. Optionally, the calculated fit curve and a non-normalised version of the covariance matrix can also be output to check the quality of the fit. See Fit v1 for more details.

A polarised He₃ cell decays over time. At the end of its life, it will be fully depolarized and a run is created to find the depolarized transmission rate through the helium. This allows for more effective efficiency corrections.

When depolarized, \(P_{He} = 0\), therefore the transmission can be determined using \(T(\lambda) = T_E(\lambda) * exp(-\mu) = T_E(\lambda) * exp(-0.0733 * p * d * \lambda)\). We can then use this equation, after normalising the DepolarizedWorkspace by the EmptyCellWorkspace, to perform a fit to determine our \(T_E\) (T_E) and \(p * d\) (pxd) values.

Usage ¶

Example - Calculate Transmission

# Create example workspaces.
CreateSampleWorkspace(OutputWorkspace='mt', Function='User Defined', UserDefinedFunction='name=UserFunction, Formula=1.465e-07*exp(0.0733*4.76*x)', XUnit='wavelength', NumMonitors=1, NumBanks=0, BankPixelWidth=1, XMin=3.5, XMax=16.5, BinWidth=0.1)
CreateSampleWorkspace(OutputWorkspace='dep', Function='User Defined', UserDefinedFunction='name=UserFunction, Formula=0.0121*exp(-0.0733*10.226*x)', XUnit='wavelength', NumMonitors=1, NumBanks=0, BankPixelWidth=1, XMin=3.5, XMax=16.5, BinWidth=0.1)

output = DepolarizedAnalyserTransmission("dep", "mt")

print("PXD Value = " + str(output.column("Value")[0]) + ".")
print("T_E Value = " + str(output.column("Value")[1]) + ".")