McStas logo McStas - A neutron ray-trace simulation package ILL; PSI; ESS Niels Bohr Institute DTU Physics NEXMAP


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[ Identification | Description | Input parameters | Links ]

The HZB_NEAT Instrument

V3 Time-of-Flight-Spectrometer (NEAT) at BENSC, 1995 version.



In time-of-flight spectrometers neutron pulses are created by us-
ing mechanical chopper devices, realised on NEAT by fast rotating
discs with speeds up to 20000 RPM. The discs are coated with neu-
tron absorbing materials except for the narrow windows. Phased to
each other according to the flight time of neutrons between them,
the choppers 'cut out' pulses of neutrons with a desired wave-
length from the white beam. An interaction with moving atoms in
the sample changes the velocities of the scattered neutrons and
this is detected by the secondary part of the spectrometer on the
basis of the time of flight between the sample and the neutron de-
tectors at 2.5 m distance. The secondary spectrometer of NEAT
contains an array of 388 3He 60 cm2 area single counter detectors
(SD) for the large-angle scattering.

The NL 2 (upper part) guide is modelled.
This model only contains the first and last choppers, and has only a single
pulse (no frame overlap). The sample is a 2mm thick plate rotated by 45 degrees,
which material can be any powder/liquid/amorphous sample.

Input parameters

Parameters in boldface are required; the others are optional.
lambdaAngsincident wavelength on sample6
dlambdaAngswavelength spread shot from the source0.05
rpmrpmdisk chopper rotation speed, setting the resolution, Hz=rpm/60.10000
cohstrsample coherent S(q,w) file name. Use LAZ/LAU or SQW file"Rb_liq_coh.sqw"
incstrsample incoherent S(q,w) file name. Use NULL to scatter incoherently"Rb_liq_inc.sqw"
tminsMinimum ToF measured0.01806
tmaxsMaximum ToF measured0.01826


[ Identification | Description | Input parameters | Links ]

Generated on 2023-09-19 20:01:36

Last Modified: Tuesday, 16-Apr-2024 20:05:20 CEST
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