[ Identification | Description | Input parameters | Links ]

# The `ISIS_SANS2d` Instrument

This instrument models the ISIS TS2 SANS2d instrument.

## Identification

- Site: ISIS
- Author: Richard Heenan with edits by Peter Willendrup
- Origin: ISIS, DTU Fysik
- Date: 2014

## Description

    This instrument models the ISIS TS2 SANS2d instrument up to the sample position.

    From the author:
    IMPORTANT: The instrument model does not currently include a correct moderator description
    - and the results it produces have not been validated against experimental results.
    The actual bender is continuously curved, here use straight segments approx.with gravity.
    1/7/10 L1=4m  increased gap between bender exit and S1 slit from .247 to .286m
    At 4m we actually use 1.75 to 16.5 angstrom.
    Note "2m guides" are actually 1.985m long (new ones will be 1.981m) so "real gaps" are included below, losses are pro-rata the gap/guide lengths.
    Both rear & front detectors are 980mm square and offset 150 above beam (would only use 100mm with hindsight)
    Rear detector can be offset -300mm or +269mm sideways.
    Front detector is closest at approx 1.4m,  furthest at approx((read det position) - 1.6m) , offset  up to -1200mm sideways
    there are 2 baffles between front & rear detector
    NIMROD (W5) spectrum might better than SANS2d (E2) spectrum for liquid H2 face incurent use.
    Stu Ansell's McStas spectra for TS-2 actually have no angle variation included.
    In reality spectra and backgrounds will vary, fast background is likely much higher on ZOOM(E1) than SANS2d (E2)
    RKH 2014

## Input parameters

Parameters in boldface are required; the others are optional.

Name | Unit | Description | Default
L1 | m | Variable distance from 1st to 2nd variable slit | 3.926
A1w | m | Width of first collimation slit, rectangular slit | 0.030
A1h | m | Height of first collimation slit, rectangular slit | 0.02
S6 | m | Radius of slit S6 (last of the optis slits) | 0.006
A2 | m | Radius of second collimation slit, circular slit | 0.006
Lmin | AA | Minimum wavelength to produce at the source | 1
Lmax | AA | Maximum wavelength to produce at the source | 14

## Links

- Source code for `ISIS_SANS2d.instr`.

[ Identification | Description | Input parameters | Links ]