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# SetGoniometer v1¶

## Summary¶

Define the goniometer motors used in an experiment by giving the axes and directions of rotations.

GoniometerAnglesFromPhiRotation

## Properties¶

Name

Direction

Type

Default

Description

Workspace

InOut

Workspace

Mandatory

An workspace that will be modified with the new goniometer created.

Goniometers

Input

string

None, Specify Individually

Set the axes and motor names according to goniometers that we define in the code (Universal defined for SNS). Allowed values: [‘None, Specify Individually’, ‘Universal’]

Axis0

Input

string

Axis0: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Axis1

Input

string

Axis1: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Axis2

Input

string

Axis2: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Axis3

Input

string

Axis3: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Axis4

Input

string

Axis4: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Axis5

Input

string

Axis5: name, x,y,z, 1/-1 (1 for ccw, -1 for cw rotation). A number of degrees can be used instead of name. Leave blank for no axis

Average

Input

boolean

True

Use the average value of the log, if false a separate goniometer will be created for each value in the logs

## Description¶

Use this algorithm to define your goniometer. Enter each axis in the order of rotation, starting with the one farthest from the sample.

You may enter up to 6 axes, for which you must define (separated by commas):

• The name of the axis, which MUST match the name in your sample logs. You can specify a number, and a log value will be created (GoniometerAxis?_FixedValue, where ? is the axis number)

• The X, Y, Z components of the vector of the axis of rotation. Right-handed coordinates with +Z=beam direction; +Y=Vertically up (against gravity); +X to the left.

• The sense of rotation as 1 or -1: 1 for counter-clockwise, -1 for clockwise rotation.

The run’s sample logs will be used in order to determine the actual angles of rotation: for example, if you have an axis called ‘phi’, then the time-average value of the log called ‘phi’ will be used as the rotation angle. Units are assumed to be degrees.

When the Average property is set to False then a separate goniometer will be created for each value in the log. When multiple log axes are defined they must have the same length and are assumed to be all the same time series.

The “Universal” goniometer at SNS is equivalent to Axis0 tied to the “omega” log pointing vertically upward, Axis1 tied to “chi” log, pointing along the beam, and Axis2 tied to “phi”, pointing vertically upward.

SetGoniometer(w,”Universal”) is the same as SetGoniometer(w,Axis0=”omega,0,1,0,1”,Axis1=”chi,0,0,1,1”,Axis2=”phi,0,1,0,1”)

## Usage¶

wg = CreateSingleValuedWorkspace()
AddSampleLog(wg, "Motor1", "45.", "Number")
SetGoniometer(wg, Axis0="Motor1,0,1,0,1", Axis1="5,0,1,0,1")

print("Log values: {}".format(wg.getRun().keys()))
print("Goniometer angles:  {}".format(wg.getRun().getGoniometer().getEulerAngles('YZY')))
print("Clearing goniometer up")
SetGoniometer(wg)
print("Goniometer angles:  {}".format(wg.getRun().getGoniometer().getEulerAngles('YZY')    ))


Output:

Log values: ['Motor1', 'GoniometerAxis1_FixedValue']
Goniometer angles:  [50,0,0]
Clearing goniometer up
Goniometer angles:  [0,0,0]


Example - multiple goniometers - omega scan

ws = LoadILLDiffraction(Filename='ILL/D20/000017.nxs')
SetGoniometer(ws, Axis0='omega.position,0,1,0,1', Average=False)

print('Number of goniometers =', ws.run().getNumGoniometers())

for i in range(ws.run().getNumGoniometers()):
print(f'{i} omega = {ws.run().getGoniometer(i).getEulerAngles("YZY")[0]:.1f}')


Output:

Number of goniometers = 21
0 omega = 1.0
1 omega = 1.2
2 omega = 1.4
3 omega = 1.6
4 omega = 1.8
5 omega = 2.0
6 omega = 2.2
7 omega = 2.4
8 omega = 2.6
9 omega = 2.8
10 omega = 3.0
11 omega = 3.2
12 omega = 3.4
13 omega = 3.6
14 omega = 3.8
15 omega = 4.0
16 omega = 4.2
17 omega = 4.4
18 omega = 4.6
19 omega = 4.8
20 omega = 5.0


Example: WISH goniometer

The WISH instrument at ISIS has a goniometer arm at 45 degrees to vertical (phi axis) that is closest to the sample, and a vertical rotation axis furthest from the sample (omega axis). The rotation angles about these axes are stored in the ewald_pos and ccr_pos logs of the workspace. The initial orientation of the phi-axis (at omega=0) is typically in the plane normal to the incident beam (i.e. the XY-plane). In this case the goniometer can be set as so

ws = LoadEmptyInstrument(InstrumentName='WISH')
SetGoniometer(ws, Axis0="ccr_pos,0,1,0,1",Axis1="ewald_pos,1,1,0,1")


Categories: AlgorithmIndex | Crystal\Goniometer