Magnetic fields in CPO3D and CPO3DS.

See also general note on magnetic fields.

For magnetic fields in CPO2D and CPO2DS, see magnetic 2D.

The magnetic field can be synthesised by adding together components selected from a menu. The maximum number of selections is 'maxvolts'.

The fields available in the menu are:

uniform magnetic field

circular current hoop

solenoid, type 1, stack of hoops

solenoid, type 2, helical coil subdivided into straight sections

‘coiled’ solenoid (type 1)

straight finite length of current

point dipole

arc of current

User-supplied 3D grid of points, complete grid array

User-supplied 3D grid of points, incomplete grid array

User-supplied 2D grid of points, for axially symmetric systems, complete grid array

User-supplied 2D grid of points, for axially symmetric systems, incomplete grid array

User-supplied field.

See details of how these fields are specified.

The user-supplied complete grid arrays are essentially redundant, but are retained for compatibility with older versions.

In the case of the user-supplied incomplete grids there is an option for assuming that the magnetic field is zero at missing grid points.

See also:

Note on using CPO3D to calculate a magnetic field by solving Laplace’s equation

Note on scaling total field

For users who are editing or constructing an 'input data file' without the use of the data-builder -that is, pre-processor:

But Manual editing is certainly not recommended -it is a relic from the time when the databuilder was not available All users are strongly encouraged to use the databuilder, which always gives the correct formats and which has many options for which the formats are not described or easily deduced.

Each selection is defined by a letter, followed by other lines of data (see below). The letters are:

'n' -for 'no' or 'no more' -that is, to terminate the list (and then the rest of this block of data will not be read)

'u' -for 'uniform' -that is, a uniform magnetic field

'h' -for 'hoop' -that is, a circular current hoop

's' -for 'solenoid', type 1

'e' -for 'solenoid', type 2

‘c’ for coiled solenoid

'l' -for 'length' -that is, a straight finite length of current

'd' -for 'dipole' -that is, a point dipole

'a' -for 'arc' -that is, an arc of current

'g' -for 'grid' -for user-supplied 3D grid of points, complete grid array

'i' -for 'grid' -for user-supplied 3D grid of points, incomplete grid array

'x' -for 'axial' -for user-supplied 2D grid of points, for axially symmetric systems, complete grid array

'y' -for 'axial' -for user-supplied 2D grid of points, for axially symmetric systems, incomplete grid array

'o' -for 'own' -that is, a user-supplied field.

In the case of 'i' and 'y' the option for assuming that the magnetic field is zero at missing grid points is triggered by putting 'y' on the 3rd space of the line.