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"

The ILL_H22_D1A Instrument

Identification

Description

Input parameters

Links

The `ILL_H22_D1A` Instrument