Workflows#

He3 Cell Workflow#

The he3 submodule provides a helper He3CellWorkflow:

[1]:

from ess import polarization as pol

print(pol.he3.He3CellWorkflow.__doc__)


    Workflow for computing transmission functions for He3 cells.

    This can handle polarizers as well as analyzers.

    Parameters
    ----------
    in_situ :
        Whether to use an in-situ definition of the cell opacity based on cell
        parameters, or an ex-situ definition based on direct beam data. The latter
        requires a direct-beam measurement with depolarized cells.
    incoming_polarized :
        Whether the incoming beam for computing the analyzer transmission is polarized.
        This is the case in beamlines with a supermirror polarizer, but also if the
        polarizer is not removed from the beam during the analyzer transmission
        measurement.

Opacity#

There are two ways of computing the opacity, from cell parameters and from direct-beam measurements.

[2]:

workflow = pol.he3.He3CellWorkflow(in_situ=True)  # True is the default
workflow.visualize(pol.He3OpacityFunction[pol.Polarizer])

[2]:

[3]:

workflow = pol.he3.He3CellWorkflow(in_situ=False)
workflow.visualize(pol.He3OpacityFunction[pol.Polarizer])

[3]:

Transmission function#

The opacity can be used to obtain the transmission function of the cells. We show the in-situ case, but it works equivalently for the more precise definition of opacity:

[4]:

workflow = pol.he3.He3CellWorkflow()
workflow.visualize(
    pol.TransmissionFunction[pol.Polarizer], graph_attr={"rankdir": "LR"}
)

[4]:

There is a variant of the workflow using an incoming polarized beam for computing the transmission function of the analyzer:

[5]:

workflow = pol.he3.He3CellWorkflow(in_situ=False, incoming_polarized=True)
workflow.visualize(
    (pol.TransmissionFunction[pol.Polarizer], pol.TransmissionFunction[pol.Analyzer]),
    graph_attr={"rankdir": "LR"},
)

[5]:

Supermirror Workflow#

The supermirror submodule provides a helper SupermirrorWorkflow:

[6]:

from ess import polarization as pol

workflow = pol.supermirror.SupermirrorWorkflow()
print(workflow.__doc__)

A container for providers that can be assembled into a task graph.

[7]:

workflow.visualize(pol.TransmissionFunction[pol.Polarizer])

[7]:

Full pipeline#

On-the-fly reduction: opacity from cell parameters#

[8]:

he3_workflow = pol.He3CellWorkflow()
workflow = pol.PolarizationAnalysisWorkflow(
    analyzer_workflow=he3_workflow, polarizer_workflow=he3_workflow
)
results = (
    pol.PolarizationCorrectedData[pol.Up, pol.Up],
    pol.PolarizationCorrectedData[pol.Up, pol.Down],
    pol.PolarizationCorrectedData[pol.Down, pol.Up],
    pol.PolarizationCorrectedData[pol.Down, pol.Down],
)
workflow.visualize(results, graph_attr={"rankdir": "LR"})

[8]:

Precise reduction: opacity from direct-beam measurements of unpolarized cells#

[9]:

he3_workflow = pol.he3.He3CellWorkflow(in_situ=False)
workflow = pol.PolarizationAnalysisWorkflow(
    analyzer_workflow=he3_workflow, polarizer_workflow=he3_workflow
)
workflow.visualize(results, graph_attr={"rankdir": "LR"})

[9]:

Correction workflow#

The correction worklow on its own looks as follows:

[10]:

from ess.polarization.correction import CorrectionWorkflow

workflow = CorrectionWorkflow()
workflow.visualize(results, graph_attr={"rankdir": "LR"})

[10]:

There is also a half-polarized version of the workflow, in case only a polarizer is used:

[11]:

from ess.polarization.correction import CorrectionWorkflow

results = (
    pol.HalfPolarizedCorrectedData[pol.Up],
    pol.HalfPolarizedCorrectedData[pol.Down],
)
workflow = CorrectionWorkflow(half_polarized=True)
workflow.visualize(results, graph_attr={"rankdir": "LR"})

[11]:

Note that in parts of the workflow Up is used as a dummy value for the spin of the analyzer that is not present.