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DetermineSpinStateOrder v1

Summary

Takes a workspace group of Polarised SANS run periods and returns a string (e.g ‘11, 10, 01, 00’) of their corresponding spin states in Wildes notation.

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	WorkspaceGroup	Mandatory	A Polarised SANS run from either LARMOR or ZOOM (group workspace with 4 periods).
SpinFlipperLogName	Input	string		Name of the log contained in the InputWorkspace which holds the flipper current (can be inferred if data is from LARMOR or ZOOM).
SpinFlipperAverageCurrent	Input	number	Optional	Expected average current for the spin slipper over all periods. Used to determine if a particular period has the flipper active or not (can be inferred if data is from LARMOR or ZOOM).
SpinStates	Output	string		A comma-seperated string of the spin states of each of the run periods e.g ‘11, 10, 01, 00’

Description

Takes a Polarised SANS transmission run and attempts to determine the spin state for each run period.

The average current through the RF flipper for every run is extracted from the appropriate spin flipper log in the instrument. The beam polarisation is determined by comparing each period transmission to the average transmission (greater than the average suggests the same state as the flipper).

If the data is from LARMOR or ZOOM, properties SpinFlipperLogName and SpinFlipperAverageCurrent can be inferred by the algorithm.

Instrument | SpinFlipperLogName | SpinFlipperAverageCurrent
LARMOR | FlipperCurrent			4.0
ZOOM | Spin_flipper			0.0

Otherwise, they can be supplied explicitly by the user.

Usage

Example - DetermineSpinStateOrder

from mantid.simpleapi import *
from mantid.api import WorkspaceGroup

wsGroup = WorkspaceGroup()
mtd.add("group", wsGroup)
y_values = [10, 80, 20, 90]
flipper_current_values = [3, 3.5, 5.5, 5.8]

for i in range(4):
    ws_name = f"ws_{i}"
    CreateSampleWorkspace("Histogram", "Flat background", XUnit="Wavelength", XMin=0, XMax=10, BinWidth=1, NumEvents=10, InstrumentName="LARMOR", OutputWorkspace=ws_name)
    CropWorkspace(ws_name, StartWorkspaceIndex=1, EndWorkspaceIndex=1, OutputWorkspace=ws_name)
    mtd[ws_name] *= y_values[i]
    AddTimeSeriesLog(ws_name, "FlipperCurrent", "2010-01-01T00:00:00", flipper_current_values[i])
    wsGroup.addWorkspace(mtd[ws_name])

ConvertToHistogram(wsGroup, OutputWorkspace=wsGroup)
result = DetermineSpinStateOrder(wsGroup)
print(f"Spin state order from wsGroup is {result}")

Output:

Spin state order from wsGroup is 01,00,10,11

Categories: AlgorithmIndex | SANS

Source

C++ header: DetermineSpinStateOrder.h

C++ source: DetermineSpinStateOrder.cpp