Polarization

In the REF_M instrument, a polarizer is placed in front of the sample and an analyzer is place behind the sample. This spin setup selects the spin state of the neutrons before and after they interact with the sample. They project the spin along a particular direction, and the selected spin state is either “up” or “down” along this direction.

Processing variables (PV) Polarizer and Analyzer indicate whether any of these spin selectors has been installed and are in use. Given a particular Polarizer, PV PolarizerState indicates the selected “up” or “down” state. PV variable AnalyzerState plays an analogous role for the analyzer.

The following tables summarize the possible values of Polarizer and Analyzer along with corresponding PolarizerState and AnalyzerState values. Lastly, the table also shows the corresponding ORSO polarization value that is used when saving the reduced data to ORSO format

PV Polarizer	PV PolarizerState	ORSO Polarization Value
0 - No Polarizer		o - “unpolarized”
1 - Reflection	1 - ON	m - “minus” or “down”
1 - Reflection	0 - OFF	p - “plus” or “up”
2 - Transmission	1 - ON	p
2 - Transmission	0 - OFF	m
3 - Undefined		o

PV Analyzer	PV AnalyzerState	ORSO Polarization Value
0 - No Analyzer		o - “unpolarized”
1 - Fan & SF2	1 - ON	m - “minus” or “down”
1 - Fan & SF2	0 - OFF	p - “plus” or “up”
2 - 3He	1 - ON	p
2 - 3He	0 - OFF	m
3 - Undefined		o