[ Identification | Description | Input parameters | Links ]

# The `ILL_H15_D11` Instrument

## Identification

- Site: ILL
- Author: FARHI Emmanuel (farhi@ill.fr)
- Origin: ILL
- Date: 2012

## Description

    D11 - LOWEST MOMENTUM TRANSFER and  LOWEST BACKGROUND SANS

    D11 is the archetype of a long, pinhole geometry instrument for small angle
    neutron scattering (SANS), designed for the study of large scale structures in
    soft matter systems, chemistry, biology, solid state physics and materials science.

    This model allows to specify the collimation length, i.e. the free path between
    the end of the guide and the sample location. When Lc=1.5 m, the intensity is
    maximal, but Q-resolution (divergence) is degraded. The Lc=40.5 m configuration
    is the low-Q one.
    The collimation can also be given as predefined configuration 'iLc' starting from 0

    iLc ={ 1.5, 2.5, 4, 5.5, 8, 10.5, 13.5, 16.5, 20.5, 28, 34, 40.5}

    so that e.g. iLc=5 corresponds with a 10.5 m collimation

    The quality of the collimation section can be specified among a set of glass
    pre-set specifications. The available configurations are:

    | Borkron_1972   Borkron_2003    Borofloat_2001  Borofloat_2003
    Chamfers [mm] | 0.2            0.2             0.8             0.2
    Wavyness [rad]| 2.5e-5         1e-4            8e-4            2e-4

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
Lambda | Angs | neutron wavelength reaching D11 sample | 4.51
Config | string | guide configuration. Must be one of Borkron_1972 Borkron_2003 Borofloat_2001 Borofloat_2003 | "Borkron_1972"
Lc | m | guide collimation, i.e. free path between end of guide and sample location. Must be one of 40.5, 34, 28, 20.5, 16.5 13.5 10.5, 8, 5.5, 4, 2.5, 1.5 | 0
iLc | index | guide collimation predefined length | 5
Chamfers | m | chamfers width (input/output movable guide section+longitudinal top/bottom sides) | 0.0002
Waviness | rad | movable guide Waviness | 2.5e-5

## Links

- Source code for `ILL_H15_D11.instr`.

[ Identification | Description | Input parameters | Links ]