[ Identification | Description | Input parameters | Links ]

# The `ILL_H22_D1A` Instrument

Simple monochromator Diffractometer for powders (D1A) installed on H22, with container/sample environment and radial collimator.

## Identification

- Site: ILL
- Author: E. Farhi
- Origin: ILL
- Date: 13 Apr 2006

## Description

    D1A is a reliable diffractometer for standard crystallographic problems. It gives
    excellent results with the Rietveld method owing to its near perfect Gaussian
    peak-shape in the 2θ-range 30° to 150°.

    Special features include
    a high fixed take-off angle of 122 deg, giving high resolution at large
    scattering angles (up to 160 deg);
    a bank of 25 high efficiency collimators and counters;
    an anisotropically squashed germanium monochromator focussing a 250
    mm high beam onto only 30 mm;
    a wide choice of wavelengths, from 1.39 Angs to 2.99 Angs, quickly available by
    simple rotation of the focussing monochromator;

    The large monochromator take-off angle means that the diffraction pattern is
    focussed for the parallel geometry shown (2θ = 122°). The counter can be swept
    through 0 deg to 2θ = 160° deg for the highest angle counter, usually in steps
    of 0.05 deg.
    Monochromator           Neutron wavelength
    Ge 117 DM=0.7946 AA     1.390
    Ge 335 DM=0.8655 AA     1.514
    Ge 115 DM=1.0925 AA     1.911 (optimal)
    Ge 113 DM=1.712 AA      2.994

    The sample is a powder, in a container can, all positioned in an
    Al environment (e.g. cryostat/furnace shield).

    This instrument was installed on the H22 guide.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
lambda | Angs | Wavelength at monochromator | 1.911
dlambda | Angs | Wavelength-spread around lambda at source | 0.03
DM | Angs | d-spacing of monochromator. Use DM=0 to compute the values from the requested wavelength. | 0
RV | m | Radius of vertical focussing. flat for 0 | -1
powder | str | File name for powder sample description | "Na2Ca3Al2F14.laz"
container | str | File name for container decription in Al cryostat/furnace | "V.laz"

## Links

- Source code for `ILL_H22_D1A_noenv.instr`.

[ Identification | Description | Input parameters | Links ]