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McStas: DiskChopper

[ Identification | Description | Input parameters | Links ]

The DiskChopper Component

Based on Chopper (Philipp Bernhardt), Jitter and beamstop from work by Kaspar Hewitt Klenoe (jan 2006), adjustments by Rob Bewey (march 2006)

Identification

  • Site:
  • Author: Peter Willendrup
  • Origin: Risoe
  • Date: March 9 2006

Description

Models a disc chopper with nslit identical slits, which are symmetrically distributed
on the disc. At time t=0, the centre of the first slit opening will be situated at the
vertical axis when phase=0, assuming the chopper centre of rotation is placed BELOW the beam axis.
If you want to place the chopper ABOVE the beam axis, please use a 180 degree rotation around Z
(otherwise unexpected beam splitting can occur in combination with the isfirst=1 setting, see
related bug on GitHub)

For more complicated gemometries, see component manual example of DiskChopper GROUPing.

If the chopper is the 1st chopper of the instrument, it sets t time with phase
- Only relevant for when using continuous source modules.

Example: DiskChopper(radius=0.2, theta_0=10, nu=41.7, nslit=3, delay=0, isfirst=1) First chopper
DiskChopper(radius=0.2, theta_0=10, nu=41.7, nslit=3, delay=0, isfirst=0)

Input parameters

Parameters in boldface are required; the others are optional.
NameUnitDescriptionDefault
theta_0degAngular width of the slits.0
radiusmRadius of the disc0.5
yheightmSlit height (if = 0, equal to radius). Auto centering of beam at half height.
nuHzFrequency of the Chopper, omega=2*PI*nu (algebraic sign defines the direction of rotation)
nslit1Number of slits, regularly arranged around the disk3
jittersJitter in the time phase0
delaysTime 'delay'0
isfirst0/1Set it to 1 for the first chopper position in a cw source (it then spreads the neutron time distribution)0
n_pulse1Number of pulses (Only if isfirst)1
abs_out0/1Absorb neutrons hitting outside of chopper radius?1
phasedegAngular 'delay' (overrides delay)0
xwidthmHorizontal slit width opening at beam center0
verbose1Set to 1 to display Disk chopper configuration0
AT ( , , ) RELATIVE
ROTATED ( , , ) RELATIVE

Links


[ Identification | Description | Input parameters | Links ]

Generated on 2024-01-03 11:47:43


Last Modified: Tuesday, 16-Apr-2024 20:05:22 CEST
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