Given the complex requirements for initial data treatment on pulsed source SANS instruments there has been general agreement to separate these from the much simpler pin-hole geometry cameras used for monochromatic X-ray and Neutron SAS studies, shown together below as NXmonosas.
Effort was made to simplify the definition below, correct errors (such as removed fields that did not exist in base classes), and remove unnecessary information.
Suggest that this be called NXsas_mono_area (very cumbersome) since the fields are appropriate to SAS instruments with area detectors at monochromatics sources. The definition does not match well to other types of SAS instrument such as USAS, Kratky, step-scanning, or slit-camera with PSD.
A description of the wavelength and possibly a spectral description (either vague or detailed such as a spectral profile) is needed for analysis software to account for not only wavelength but wavelength smearing and other spectral effects (high-order harmonics, for example). Due to the variety of optics used to provide such a beam, rather than define each of those possible optics in the generic instrument definition, we define the spectral properties of the beam incident on the sample that results from all the upstream optics.
Two possible ways:
<?xml version="1.0" encoding="utf-8"?>
<!--
URL: ?
Name: NXsas_mono_area (candidate name)
Editor: Ron Ghosh <ron@ill.fr>
Principal Contributors:
Steve King <s.m.king@rl.ac.uk>,
Mark Koennecke <Mark.Koennecke@psi.ch>,
P.Jemian APS,
J.Suzuki-san JPARC,
A.Gotz ESRF
Valuable comments from
N. Maliszewskyj,
P Kienzle NIST,
N. Terrill DIAMOND
Version October 2006
-->
<NXroot>
<NXentry name="{Entry Name}">
<NXinstrument name="{Name of instrument}">
<name short_name="{short name of instrument}">{Name of instrument}?
</name>
<NXsource name="{Name of facility}">
<probe type="NX_CHAR">"neutron"|"x-ray"</probe>
</NXsource>
<NXattenuator name="{Name of beam attenuator}">
<attenuator_transmission type="NX_FLOAT">
{The nominal fraction of the beam transmitted by the attenuator}
</attenuator_transmission>
</NXattenuator>
<NXaperture name="Name of beamline aperture">
<NXgeometry name="geometry">{location and shape of aperture}</NXgeometry>
</NXaperture>
<NXcollimator name="Name of beam collimator">
<NXgeometry name="geometry">{location and shape of collimator}</NXgeometry>
</NXcollimator>
<!--
A description of the wavelength and possibly a spectral description
(either vague or detailed such as a spectral profile) is needed for
analysis software to account for not only wavelength but wavelength
smearing and other spectral effects (high-order harmonics, for example).
Due to the variety of optics used to provide a generic beam, define
the spectral properties of the beam incident on the sample
that results from all the upstream optics.
-->
<NXmonochromator name="Beam_at_sample"> {characteristics of beam at sample}
<wavelength type="NX_FLOAT[]" units="angstrom">{selected wavelength}</wavelength>
<wavelength_fwhm type="NX_FLOAT[]" units="angstrom">
{wavelength distribution full width at half maximum}?
</wavelength_fwhm>
<NXdata name="wavelength_distribution">?</NXdata>
</NXmonochromator>
<NXdetector name="{Name(s) of detector(s)}">
<data type="NX_FLOAT[i,j,...]|NX_INT[i,j,...]" signal="1">
{Data values}?
</data>
<distance type="NX_FLOAT" units="mm">
{distance between sample and detector}
</distance>
<x_offset type="NX_FLOAT[k+1]" axis="1">
{X-direction pixel coordinate on the detector with origin at detector center}?
</x_offset>
<y_offset type="NX_FLOAT[l+1]" axis="2">
{Y-direction pixel coordinate on the detector with origin at detector center}?
</y_offset>
<quiet_count type="NX_FLOAT[i,j,...]|NX_INT[i,j,...]">
{signal from detector when not illuminated}?
<!-- This field needs to be added to NXdetector -->
</quiet_count>
<NXgeometry name="beam_center">
{x,y position of straight-through beam (a.k.a. beam center) on the detector}?
</NXgeometry>
</NXdetector>
<NXbeam_stop name="Name of beam stop">
<NXgeometry name="geometry">{shape, orientation and position of the beam stop}
</NXgeometry>
<status type="NX_CHAR">{"in"|"out"}</status>
</NXbeam_stop>
</NXinstrument>
<NXmonitor name="control {Name of the monitor}">
<mode type="NX_CHAR">
"monitor"|"timer"?
</mode>
<preset type="NX_FLOAT">{preset for terminating measurement}</preset>
<data type="NX_INT[i]|NX_FLOAT[i]">
{Monitor value}
</data>
<quiet_count type="NX_FLOAT[i,j,...]|NX_INT[i,j,...]">
{signal from monitor when not illuminated}?
<!-- This field needs to be added to NXmonitor -->
</quiet_count>
<count_time type="NX_FLOAT" units="second">
{Elapsed actual counting time, the time the instrument
was really counting, without pauses or times lost due
beam unavailability}
</count_time>
</NXmonitor>
<NXsample name="{Name of sample}"></NXsample>
<NXdata name="Datablock name">+
<data type="NX_INT[...] | NX_FLOAT[...]" signal="1">
{link to detector counts in NXdetector}
</data>
<x_offset type="NX_FLOAT[k+1]">
{link to x_offset in detector group}
</x_offset>
<y_offset type="NX_FLOAT[l+1]">
{link to y_offset in detector group}
</y_offset>
</NXdata>
</NXentry>
</NXroot>