[ Identification | Description | Input parameters | Links ]

The Pol_Bfield Component

Identification

• Site:
• Author: Erik B Knudsen, Peter Christiansen and Peter Willendrup
• Origin: RISOE
• Date: July 2011

Description

Region with a definable magnetic field.

The component is nestable if the concentric flag is set (the default). This means that it requires a
// START MAGNETIC FIELD
COMPONENT msf =
Pol_Bfield(xwidth=0.08, yheight=0.08, zdepth=0.2, Bx=0, By=-0.678332e-4, Bz=0)
AT (0, 0, 0) RELATIVE armMSF

// OTHER COMPONENTS INSIDE THE MAGNETIC FIELD CAN BE PLACED HERE

// STOP MAGNETIC FIELD
COMPONENT msf_stop = Pol_simpleBfield_stop(magnet_comp_stop=msf)
AT (0, 0, 0) RELATIVE armMSF

Note that if you have objects within the magnetic field that extend outside it you may get
wrong results, because propagation within the field will then possibly extend outside, e.g.
when using a tabled field. The evaluated field will then use the nearest defined field point
_also_ outside the defintion area. If these outside-points have a non-zero field precession will
continue - even after the neutron has left the field region.

In between the two component instances the propagation routine
PROP_DT also handles spin propagation.
The current algorithm used for spin propagation is:
SimpleNumMagnetPrecession
in pol-lib.

Example: Pol_Bfield(xwidth=0.1, yheight=0.1, zdepth=0.2, Bx=0, By=1, Bz=0)
Pol_Bfield(xwidth=0.1, yheight=0.1, zdepth=0.2,
filename="bfield.dat", fieldFunction=table_magnetic_field)

The magetic field may be given as any definable c-function with a specific footprint:
int func(double x, double y, double z, double t, double *bx, double *by, double *bz, void *data)
where the magnetic field at coordinates (x,y,z, t) is returned in the variables
pointed to by bx,by, and bz. Additional parameters to be handed to the function
should be handed to the function using the pointer data.

Functions supplied by the system are:
1. const_magnetic_field: Constant field (Bx,By,Bz) within the region
2. rot_magnetic_field: Field is initially (0,By,0) but after a length of zdepth
has rotated to (By,0,0)
3. majorana_magnetic_field: Field is initially (Bx,By,0) liearly transforms to
(-Bx,By,0) after zdepth where By<

Input parameters
Parameters in boldface are required;
the others are optional.


 
Name
Unit
Description
Default


 
fieldFunction
pointer
Function describing the magnetic field.
const_magnetic_field

 
field_prms
NULL

 
xwidth
m
Width of opening.
0

 
yheight
m
Height of opening.
0

 
zdepth
m
Length of field.
0

 
radius
m
Radius of field if it is cylindrical or spherical.
0

 
Bx
T
Parameter used for x composant of field.
0

 
By
T
Parameter used for y composant of field.
0

 
Bz
T
Parameter used for z composant of field.
0

 
filename
 
File where the magnetic field is tabulated.
"bfield.dat"

 
geometry
NULL

 
interpol_method
 
When using tabulated field, choice of interpolation method "kdtree" (default) / "regular"
NULL

 
concentric
 
Allow components and/or other fields inside field. Requires a subsequent Pol_simpleBfield_stop component.
1




  

  
AT (
  
, 
  
, 
  

  
) RELATIVE
  

  

    Generate
  
  
  

  
ROTATED (
  
, 
  
, 
  

  
) RELATIVE
  



Links


  
 Source code for Pol_Bfield.comp.
  



 [ Identification
 | Description
 | Input parameters
 | Links ]



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