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

# The `Collimator_ROC` Component

Radial Oscillationg Collimator (ROC)

## Identification

- Author: Thomas C Hansen
- Origin: ILL (Dif/D20)
- Date: 15 May 2000
- Version: 1.2
- Modification history:
  - J.Ollivier Nov 2001: cleaned the code

## Description

    This is an implementation of an Ideal radial oscillating collimator,
    which is usually placed between a polycrystalline sample and a linear
    curved position sensitive detector on a 2-axis diffractometer like D20.
    The transfer function has been implemented analytically, as this is
    much more efficient than doing Monte-Caqrlo (MC) choices and to absorb
    many neutrons on the absorbing blades. The function is basically triangular
    (except for rather 'exotic' focuss apertures) and depends on the distance
    from the projection of the focus centre to the plane perpendicular to the
    collimator planes to the intersection of the same projection of the velocity
    vector of the neutron with a line that is perpendicular to it and containing
    the same projection of the focus centre. The oscillation is assumed to be
    absolutely regular and so shading each angle the same way. All neutrons not
    hitting the collimator core will be absorbed.

    Example: Collimator_ROC(
        ROC_pitch=5, ROC_ri=0.15, ROC_ro=0.3, ROC_h=0.15,
        ROC_ttmin=-25, ROC_ttmax=135, ROC_sign=-1, ROC_present=1)

WARNING: This is a contributed Component.

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
--- | --- | --- | ---
ROC_pitch | 1 | [deg] Angular pitch between the absorbing blades |
ROC_ri | 0.4 | [m] Inner radius of the collimator |
ROC_ro | 1.2 | [m] Outer radius of the collimator |
ROC_h | 0.153 | [m] Height of the collimator |
ROC_ttmin |  |  |
ROC_ttmax | 100 | [deg] Higher scattering angle limit |
ROC_sign | 1 | [1] Chirality/takeoff sign | 1
ROC_present | 1 | [1] Presence flag of this component | 1

## Links

- Source code for `Collimator_ROC.comp`.
- Source code of d20.instr, where this component is used Components for the simulation of D20

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