.. auto-generated by script ../../../../utils/nxdl2rst.py from the NXDL source NXdisk_chopper.nxdl.xml .. index:: ! NXdisk_chopper (base class) ! disk_chopper (base class) see: disk_chopper (base class); NXdisk_chopper .. _NXdisk_chopper: ============== NXdisk_chopper ============== **Status**: base class, extends :ref:`NXobject` **Description**: A device blocking the beam in a temporal periodic pattern. A disk which blocks the beam but has one or more slits to periodically let neutrons through as the disk rotates. Often used in pairs, one NXdisk_chopper should be defined for each disk. The rotation of the disk is commonly monitored by recording a timestamp for each full rotation of disk, by having a sensor in the stationary disk housing sensing when it is aligned with a feature (such as a magnet) on the disk. We refer to this below as the "top-dead-center signal". Angles and positive rotation speeds are measured in an anticlockwise direction when facing away from the source. **Symbols**: This symbol will be used below to coordinate datasets with the same shape. **n**: Number of slits in the disk **Groups cited**: :ref:`NXgeometry` .. index:: NXgeometry (base class); used in base class **Structure**: .. _/NXdisk_chopper@default-attribute: .. index:: default (file attribute) **@default**: (optional) :ref:`NX_CHAR ` .. index:: plotting Declares which child group contains a path leading to a :ref:`NXdata` group. It is recommended (as of NIAC2014) to use this attribute to help define the path to the default dataset to be plotted. See https://www.nexusformat.org/2014_How_to_find_default_data.html for a summary of the discussion. .. _/NXdisk_chopper/type-field: .. index:: type (field) **type**: (optional) :ref:`NX_CHAR ` Type of the disk-chopper: only one from the enumerated list (match text exactly) Any of these values: * ``Chopper type single`` * ``contra_rotating_pair`` * ``synchro_pair`` .. _/NXdisk_chopper/rotation_speed-field: .. index:: rotation_speed (field) **rotation_speed**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_FREQUENCY `} Chopper rotation speed. Positive for anticlockwise rotation when facing away from the source, negative otherwise. .. _/NXdisk_chopper/slits-field: .. index:: slits (field) **slits**: (optional) :ref:`NX_INT ` Number of slits .. _/NXdisk_chopper/slit_angle-field: .. index:: slit_angle (field) **slit_angle**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_ANGLE `} Angular opening .. _/NXdisk_chopper/pair_separation-field: .. index:: pair_separation (field) **pair_separation**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_LENGTH `} Disk spacing in direction of beam .. _/NXdisk_chopper/slit_edges-field: .. index:: slit_edges (field) **slit_edges[2n]**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_ANGLE `} Angle of each edge of every slit from the position of the top-dead-center timestamp sensor, anticlockwise when facing away from the source. The first edge must be the opening edge of a slit, thus the last edge may have an angle greater than 360 degrees. .. _/NXdisk_chopper/top_dead_center-field: .. index:: top_dead_center (field) **top_dead_center**: (optional) :ref:`NX_NUMBER ` {units=\ :ref:`NX_TIME `} Timestamps of the top-dead-center signal. The times are relative to the "start" attribute and in the units specified in the "units" attribute. Please note that absolute timestamps under unix are relative to ``1970-01-01T00:00:00.0Z``. .. _/NXdisk_chopper/top_dead_center@start-attribute: .. index:: start (field attribute) **@start**: (optional) :ref:`NX_DATE_TIME ` .. _/NXdisk_chopper/beam_position-field: .. index:: beam_position (field) **beam_position**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_ANGLE `} Angular separation of the center of the beam and the top-dead-center timestamp sensor, anticlockwise when facing away from the source. .. _/NXdisk_chopper/radius-field: .. index:: radius (field) **radius**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_LENGTH `} Radius of the disk .. _/NXdisk_chopper/slit_height-field: .. index:: slit_height (field) **slit_height**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_LENGTH `} Total slit height .. _/NXdisk_chopper/phase-field: .. index:: phase (field) **phase**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_ANGLE `} Chopper phase angle .. _/NXdisk_chopper/delay-field: .. index:: delay (field) **delay**: (optional) :ref:`NX_NUMBER ` {units=\ :ref:`NX_TIME `} Time difference between timing system t0 and chopper driving clock signal .. _/NXdisk_chopper/ratio-field: .. index:: ratio (field) **ratio**: (optional) :ref:`NX_INT ` Pulse reduction factor of this chopper in relation to other choppers/fastest pulse in the instrument .. _/NXdisk_chopper/distance-field: .. index:: distance (field) **distance**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_LENGTH `} Effective distance to the origin .. _/NXdisk_chopper/wavelength_range-field: .. index:: wavelength_range (field) **wavelength_range[2]**: (optional) :ref:`NX_FLOAT ` {units=\ :ref:`NX_WAVELENGTH `} Low and high values of wavelength range transmitted .. _/NXdisk_chopper/GEOMETRY-group: **GEOMETRY**: (optional) :ref:`NXgeometry` Hypertext Anchors ----------------- Table of hypertext anchors for all groups, fields, attributes, and links defined in this class. ======================================================================================================== ======================================================================================================== documentation (reST source) anchor web page (HTML) anchor ======================================================================================================== ======================================================================================================== :ref:`/NXdisk_chopper/beam_position-field ` :ref:`#nxdisk-chopper-beam-position-field ` :ref:`/NXdisk_chopper/delay-field ` :ref:`#nxdisk-chopper-delay-field ` :ref:`/NXdisk_chopper/distance-field ` :ref:`#nxdisk-chopper-distance-field ` :ref:`/NXdisk_chopper/GEOMETRY-group ` :ref:`#nxdisk-chopper-geometry-group ` :ref:`/NXdisk_chopper/pair_separation-field ` :ref:`#nxdisk-chopper-pair-separation-field ` :ref:`/NXdisk_chopper/phase-field ` :ref:`#nxdisk-chopper-phase-field ` :ref:`/NXdisk_chopper/radius-field ` :ref:`#nxdisk-chopper-radius-field ` :ref:`/NXdisk_chopper/ratio-field ` :ref:`#nxdisk-chopper-ratio-field ` :ref:`/NXdisk_chopper/rotation_speed-field ` :ref:`#nxdisk-chopper-rotation-speed-field ` :ref:`/NXdisk_chopper/slit_angle-field ` :ref:`#nxdisk-chopper-slit-angle-field ` :ref:`/NXdisk_chopper/slit_edges-field ` :ref:`#nxdisk-chopper-slit-edges-field ` :ref:`/NXdisk_chopper/slit_height-field ` :ref:`#nxdisk-chopper-slit-height-field ` :ref:`/NXdisk_chopper/slits-field ` :ref:`#nxdisk-chopper-slits-field ` :ref:`/NXdisk_chopper/top_dead_center-field ` :ref:`#nxdisk-chopper-top-dead-center-field ` :ref:`/NXdisk_chopper/top_dead_center@start-attribute ` :ref:`#nxdisk-chopper-top-dead-center-start-attribute ` :ref:`/NXdisk_chopper/type-field ` :ref:`#nxdisk-chopper-type-field ` :ref:`/NXdisk_chopper/wavelength_range-field ` :ref:`#nxdisk-chopper-wavelength-range-field ` :ref:`/NXdisk_chopper@default-attribute ` :ref:`#nxdisk-chopper-default-attribute ` ======================================================================================================== ======================================================================================================== **NXDL Source**: https://github.com/FAIRmat-Experimental/nexus_definitions/tree/fairmat/base_classes/NXdisk_chopper.nxdl.xml