Time-of-Flight Neutron Powder Diffraction

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Comments

  • Discussion items
    • time_focusing_type (e.g. difc, cubic, ..)
    • time_focusing_parameters [ndetector,nparameters]
    • Definition of groups for binning in NeXus file or via NXdetector ?
    • Deadtime correction information (in combination with gang_..)
    • Profile types and starting parameters
    • Incident spectrum (here in NXcharacterization, alternative analytical description ?)
  • Other
    • Binned data back in NeXus - this actually is used in Rietveld.

Proposal

Contents

XML Meta-DTD Definition for NXtofnpd.xml

This follows the XML Meta-DTD Definition format and can be downloaded from http://svn.nexusformat.org/definitions/tags/PRE_NXDL/instruments/NXtofnpd.xml 

<?xml version="1.0" encoding="UTF-8"?>
<!--
URL:     http://definitions.nexusformat.org/NXtofnpd.xml
Editor:  Peter Peterson <petersonpf@sns.gov>
$Id$

Instrument definition for a time-of-flight neutron powder diffractometer. 

-->
<NXentry name="{Entry Name}">

   <title type="NX_CHAR[]">{Extended title for entry}</title>
   <definition type="NX_CHAR[]" version="$Revision$" URL="definitions.nexusformat.org/NXtofnpd.xml">TOFNPD</definition>
   <start_time type="ISO8601">{Starting time of measurement}</start_time>
   <end_time type="ISO8601">{Ending time of measurement}</end_time>

   <NXinstrument name="{name of the instrument}">
      <name short_name="{abbreviated name of instrument}" type="NX_CHAR[]">{Name of instrument}</name>

      <NXsource name="source">+
         <distance type="NX_FLOAT" units="meter">{distance from the sample (should be negative)}</distance>
      </NXsource>

     <NXdetector name="{Name of detector bank}">
        <time_focusing_type type="NX_CHAR">gsas_difc|gsas_cubic|jason</time_focusing_type>
        <time_focusing_parameters type="NX_FLOAT[fp]">{Parameters for focusing depending on type}</time_focusing_parameters>

	<time_of_flight type="NX_FLOAT[tof+1]" axis="3" primary="1?" units="microsecond">
		{Total time of flight}+
	</time_of_flight>

	<detector_number type="NX_INT[i?,j?]">
		{Identifier for detector}
	</detector_number>

	<data type="NX_FLOAT[np,i,j,tof]|NX_INT[np,i?,j?,tof?]" signal="1" axes="[number of scan points,x_offset,y_offset,time_of_flight]">
		{Data values}
	</data>

	<data_error type="NX_FLOAT[np?,i?,j?,tof?]|NX_INT[np?,i?,j?,tof?]" units="number">
		{Data values}?
	</data_error>

	<distance type="NX_FLOAT[np?,i?,j?]">
               {secondary flightpath}
	</distance>

	<polar_angle type="NX_FLOAT[np?,i?,j?]">
               {polar angle for each detector pixel}
	</polar_angle>

	<azimuthal_angle type="NX_FLOAT[np?,i?,j?]">
               {azimuthal angle for each detector pixel. If missing, angle assumed to be zero.}?
	</azimuthal_angle>

	<solid_angle type="NX_FLOAT[i?,j?]" units="steradians">
		{Solid angle subtended by the detector at the sample}?
	</solid_angle>

	<dead_time type="NX_FLOAT[np?,i?,j?]">
		{Detector dead time}?
	</dead_time>

        <layout type="NX_CHAR">point|linear|area{How the detector is represented}</layout>
      </NXdetector>
 
      <NXcharacterization name="isotropic_scatterer">
	  <definition version="$Revision$" URL="definitions.nexusformat.org/NXtofnpd.xml">TOFNPD</definition>
      </NXcharacterization>

     <NXcharacterization name="isotropic_scatterer_background">
	  <definition version="$Revision$" URL="definitions.nexusformat.org/NXtofnpd.xml">TOFNPD</definition>
      </NXcharacterization>

    <NXcharacterization name="empty_environment">
	  <definition version="$Revision$" URL="definitions.nexusformat.org/NXtofnpd.xml">TOFNPD</definition>
      </NXcharacterization>
   </NXinstrument>

   <NXmonitor name="{name of the monitor}">*
      <distance type="NX_FLOAT" units="meter"></distance>
      <time_of_flight type="NX_FLOAT[i]|NX_INT[i]" units="microsecond"></time_of_flight>
      <data type="NX_FLOAT[i]|NX_INT[i]" units="number"></data>
      <data_error type="NX_FLOAT[i]|NX_INT[i]" units="number">?</data_error>
   </NXmonitor>

   <NXdata name="">+
      <time_of_flight>{Link to time_of_flight in NXdetector}</time_of_flight>
      <detector_number>{Link to detector_number in NXdetector}</detector_number>
      <data>{Link to data in NXdetector}</data>
   </NXdata>

</NXentry>

Tabular Representation of XML Meta-DTD

(automatically generated from http://svn.nexusformat.org/definitions/tags/PRE_NXDL/instruments/NXtofnpd.xml)

NXentry

Name Type Description Attributes
titleNX_CHAR[]Extended title for entry
definitionNX_CHAR[]
version="$Revision$"

URL="definitions.nexusformat.org/NXtofnpd.xml"

start_timeISO 8601Starting time of measurement
end_timeISO 8601Ending time of measurement
{name of the instrument}NXinstrument

NXinstrument

Name Type Description Attributes
nameNX_CHAR[]Name of instrument
short_name="{abbreviated name of instrument}"
sourceNXsource

NXsource

Name Type Description Attributes
distanceNX_FLOATdistance from the sample (should be negative)
units="meter"

NXinstrument continued (1)

Name Type Description Attributes
{Name of detector bank}NXdetector

NXdetector

Name Type Description Attributes
time_focusing_typeNX_CHAR
time_focusing_parametersNX_FLOAT[fp]Parameters for focusing depending on type
time_of_flightNX_FLOAT[tof+1]Total time of flight
axis="3"

primary="1?"
units="microsecond"

detector_numberNX_INT[i?,j?]Identifier for detector
dataNX_FLOAT[np,i,j,tof]|NX_INT[np,i?,j?,tof?]Data values
signal="1"

axes="[number of scan points,x_offset,y_offset,time_of_flight]"

data_errorNX_FLOAT[np?,i?,j?,tof?]|NX_INT[np?,i?,j?,tof?]Data values
units="number"
distanceNX_FLOAT[np?,i?,j?]secondary flightpath
polar_angleNX_FLOAT[np?,i?,j?]polar angle for each detector pixel
azimuthal_angleNX_FLOAT[np?,i?,j?]azimuthal angle for each detector pixel. If missing, angle assumed to be zero.
solid_angleNX_FLOAT[i?,j?]Solid angle subtended by the detector at the sample
units="steradians"
dead_timeNX_FLOAT[np?,i?,j?]Detector dead time
layoutNX_CHAR

NXinstrument continued (2)

Name Type Description Attributes
isotropic_scattererNXcharacterization

NXcharacterization

Name Type Description Attributes
definitionNX_CHAR
version="$Revision$"

URL="definitions.nexusformat.org/NXtofnpd.xml"

NXinstrument continued (3)

Name Type Description Attributes
isotropic_scatterer_backgroundNXcharacterization

NXcharacterization

Name Type Description Attributes
definitionNX_CHAR
version="$Revision$"

URL="definitions.nexusformat.org/NXtofnpd.xml"

NXinstrument continued (4)

Name Type Description Attributes
empty_environmentNXcharacterization

NXcharacterization

Name Type Description Attributes
definitionNX_CHAR
version="$Revision$"

URL="definitions.nexusformat.org/NXtofnpd.xml"

NXentry continued (1)

Name Type Description Attributes
{name of the monitor}NXmonitor

NXmonitor

Name Type Description Attributes
distanceNX_FLOAT
units="meter"
time_of_flightNX_FLOAT[i]|NX_INT[i]
units="microsecond"
dataNX_FLOAT[i]|NX_INT[i]
units="number"
data_errorNX_FLOAT[i]|NX_INT[i]
units="number"

NXentry continued (2)

Name Type Description Attributes
NXdata

NXdata

Name Type Description Attributes
time_of_flightNX_CHARLink to time_of_flight in NXdetector
detector_numberNX_CHARLink to detector_number in NXdetector
dataNX_CHARLink to data in NXdetector

Retrieved from "http://www.nexusformat.org/Time-of-Flight_Neutron_Powder_Diffraction"
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