NRCalculateSlitResolution v1¶

Summary¶

Calculates the reflectometry resolution (dQ/Q) for a given workspace.

Properties¶

Description¶

This algorithm takes a workspace and a value for two theta, and attempts to calculate the reflectometry resolution (dQ/Q) from them. If no value is provided for two theta then NRCalculateSlitResolution will attempt to fetch a value from the workspace’s log using the theta log name provided.

The effective inverse of this algorithm is CalculateSlits v1.

Beam Divergence¶

Schematic showing beam divergence using two slits (Slit1 and Slit2)

Proof

$$\begin{align}\begin{aligned}\frac{d1}{x} \equiv \frac{d2}{l - x} \equiv \tan(\alpha)\\\therefore \frac{d1}{x} = \frac{d1 + d2}{l}\\\therefore \alpha = \arctan\left(\frac{d1 + d2}{l}\right)\end{aligned}\end{align}$$

where $\alpha$ gives is the beam divergence in radians. Parameter d1 is the vertical distance of Slit1 opening, d2 is the same for Slit2. parameter l is the distance between the slits in the beam direction. See figure above for reference.

The resolution is then calculated from:

$$resolution = \frac{\alpha}{2 \tan(\theta)}$$

Usage¶

ws = Load('INTER00013460')
res = NRCalculateSlitResolution(Workspace = ws, TwoTheta = 0.7 * 2)
print("Resolution: {:.4f}".format(res))

Resolution: 0.0340

Categories: AlgorithmIndex | Reflectometry\ISIS

Source¶

C++ header: NRCalculateSlitResolution.h

C++ source: NRCalculateSlitResolution.cpp