[ Identification | Description | Input parameters | Output parameters | Links ]

# The `Filter_powder` Component

Incorporating code from Single_crystal, written by KN, December 1999 Box-shaped powder filter or sample (BUGGY)

## Identification

- Author: B. Fortescue
- Origin: ILL, Based on Be_filter, written by SN Klausen, December 1999,
- Date: August 2000
- Version: 1.8
- Modification history:
  - EF, Aug. 24th 2001: made it work
  - EF, 22nd Apr 2003 : now uses Read_Table library
  - EF, 22nd May 2003 : Corrected velocity dir change bug.

## Description

    This is a general box-shaped powder filter/sample which simulates
    multiple coherent scattering vectors and absorption (incoherent
    scattering is modelled as absorption).
    Crystal structure is specified with an ascii data file. Each line
    contains seven numbers, separated by white space. The first three numbers
    are the (h,k,l) indices of the reciprocal lattice point, and the last
    number is the value of the structure factor |F|**2, in barns.  (The rest
    of the numbers are not used; the file is in the format output by the
    Crystallographica program).
    Optionally, a number of absorbing blades may be incorporated into the
    filter - these are X-Z or Y-Z planes evenly spaced along the X or Y axis
    of the filter which absorb any neutron encountering them.

    EXAMPLE:
    You may use, as a filter, something like (5x5x5 cm cube):
        Filter_powder(
         ax=2.714, by=2.714, cz=4.405, cc=120,
         sigma_a = 0.0156,
         reflections="BeO.lau")

    and as a sample (1x1x1 cm cube):
        Filter_powder(
         ax=3.8186, by=3.8186, cz=11.6777,
         xmin =-0.005 , xmax = 0.005, ymin = -0.005, ymax = 0.005,
         zmin = -0.005, zmax = 0.005, XBlades=0, YBlades=0,
         sigma_a = 0, reflections="YBaCuO.lau")                                  *
    %BUGS

    This component is known to produce wrong results but is given in hope
    somebody will find it useful and fix it.

WARNING: This is a contributed Component.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
--- | --- | --- | ---
reflections | string | File name containing structure factors of reflections |
xmin | m | Lower x-value of powder sample | -0.05
xmax | m | Upper x-value of powder sample | 0.05
ymin | m | Lower y-value of powder sample | -0.05
ymax | m | Upper y-value of powder sample | 0.05
zmin | m | Lower z-value of powder sample | -0.05
zmax | m | Upper z-value of powder sample | 0.05
ax | AA | ,ay,az : Coordinates of first unit cell vector | 2.714
ay |  |  | 0
az |  |  | 0
bx | AA | ,by,bz : Coordinates of second unit cell vector | 0
by |  |  | 2.714
bz |  |  | 0
cx | AA | ,cy,cz : Coordinates of third unit cell vector | 0
cy |  |  | 0
cz |  |  | 4.405
pack | 1 | Packing factor of powder | 1
sigma_a | barns | Absorption cross-section per unit cell at 2200 m/s | 0.0156
DW | 1 | Debye-Waller factor of reflection | 1
XBlades | 1 | Number of vertical absorbing blades | 2
YBlades | 1 | Number of horizontal absorbing blades | 2
aa | - | ,bb,cc : unit cell angles alpha, beta and gamma (deg). Then uses norms of vectors a,b and c as lattice parameters. | 90
bb |  |  | 90
cc |  |  | 0

## Output parameters

Name | Unit | Description | Default
--- | --- | --- | ---
XBlade_pos |  |  |
YBlade_pos |  |  |
xb |  |  |
xt |  |  |
yb |  |  |
yt |  |  |
pf_hkl_info |  |  |

## Links

- Source code for `Filter_powder.comp`.
- See also filter.ps (PS doc).

[ Identification | Description | Input parameters | Output parameters | Links ]