In the McStas formulation of a neutron scattering instrument, all
objects apart from the neutron ray are referred to as components. This
includes for instance
- Source The exit of a neutron production facility, where
neutron rays of certain velocities are emitted into some
portion of space
- Monochromator (Idealized) crystals used to select a
neutrons of a single wavelength
1 to probe the sample with (monochromator) or to
analyze (analyzer)
- Sample An object altering the neutron physical properties
in some sense, examples used here are
- Vanadium. Scatters incoming neutron rays incoherently
- Powder2. Can be thought of as a large number of crystals,
each scattering neutron rays according to the Bragg law, thereby
producing two concentric Debye Sherrer cones. This sample also
has the posibility of adding inchoherent, eleasticly scattered
neutron rays.
- Monitors Objects monitoring or registering neutron ray
characteristics. In the exercises below are used different types
of detectors or monitors:
- Monitor. Single monitor, detecting the number of flying
through a plane. (User defined opening size)
- PSD_monitor. Square monitor, detecting the number of
neutron rays passing through a plane, divided into
pixels. square regions of a plane. (User defined resolution
and opening siz)
- PSD_monitor_4PI. As PSD_monitor but shaped like a sphere.
- L_monitor. Wavelength monitor, measuring the different
wavelengths of the passing neutron rays. (L is for
)
- Monitor_nD. General monitor for detecting all sorts of
physical properties of the neutron ray. In our cases used with
options
- 'single' - as PSD_monitor but only one small square
- 'banana' - as PSD_monitor but shaped like a curved,
horizontal band
- Collimators Devices controling the direction and divergence
of the neutron ray.
- Collimator_linear A series of parallel absorbing neutron plates
that limits the beam divergence.
Typical values are
to
.
More information on the McStas components is available by using the
mcdoc
program (You may need to set the BROWSER system variable
to your webbrowser of choice):
mcdoc -s
, Shows a html list of all the components
mcdoc Monitor.comp
, Shows the documentation for a given component
mcdoc -M
, brings up the McStas manual in PDF format
mcdoc -c
, brings up the McStas component manual in PDF format
Peter Willendrup
2005-11-16