zaxis — Z-Axis Four-Circle (Surface)#

Z-axis four-circle diffractometer for surface diffraction. The sample surface normal is parallel to the Z-axis. Sample and detector share an alpha base stage.

Walko (2016) designation: (S1D2)1

Coordinate basis: You (1999) (BASIS_YOU): vertical=+x, longitudinal=+y, transverse=+z.

Quick start#

import ad_hoc_diffractometer as ahd

g = ahd.presets.zaxis()
g.wavelength = 1.0  # Å
print(g.summary())

Pre-built geometry definition#

This geometry is defined by the zaxis() factory function — see the source for the complete stage and mode configuration.

Stage layout#

Static fallback (click to expand if the interactive figure above is blank)

zaxis stage layout

Sample stages (base first):

Stage

Axis

Handedness

Parent

alpha

+vertical (+x)

right-handed, shared base

base

Z

+longitudinal (+y)

right-handed

alpha

Detector stages (base first):

Stage

Axis

Handedness

Parent

delta

−transverse (−z)

left-handed

alpha

gamma

+vertical (+x)

right-handed

delta

Shared stage: alpha (base stage shared between sample and detector stacks)

Diffraction modes#

Each mode is a ConstraintSet of 1 constraint (N − 3 = 1 for N = 4 DOF). Requires g.surface_normal = (h, k, l) — see Surface Geometry and the Reference Vector. See Work with Constraints and Diffraction Modes for the extras dict pattern.

zaxis#

ReferenceConstraint: surface normal aligned with the Z-axis; alpha directly equals the incidence angle β_in, gamma directly equals the exit angle β_out.

Computed

Z, delta, gamma

Constant during forward()

—

Extras (input)

n̂ (surface normal)

Extras (output)

alpha_i (= alpha), beta_out (= gamma)

reflectivity#

ReferenceConstraint: symmetric reflection — alpha_i = beta_out (alpha = gamma).

Computed

Z, delta, alpha, gamma

Constant during forward()

—

Extras (input)

n̂

Extras (output)

alpha_i, beta_out

API reference#

References#

  • Bloch, J. Appl. Cryst. 18, 33–36 (1985). DOI: 10.1107/S0021889885009858

  • Walko, Ref. Module Mater. Sci. Mater. Eng. (2016).