Conductor - Racetrack
Racetracks are used in particle accelerators and in traps for plasmas or (at ultra-low temperatures) neutral atoms. BiotSavart implements planar racetracks. The dimensions of the racetrack are specified by the following quantities:
| base | straight section length (x direction) |
| length | straight section length (z direction) |
| span | distance between straights |
| width | width of conductor (in plane) |
| height | height (out of plane) |
The figure below shows these quantities in the object coordinate frame.
The nturn parameter
The corners of the racetrack are approximated, both in drawing and field calculation, by finite angular steps. The number of steps in the semicircle is set by the nturn parameter. This is the number of interior faces in a 180 degree turn, not counting the faces at 0 and 180 degrees. The computation time is proportional to nturn+2, so it is best to use a small number unless an accurate depiction of the end fields is desired. The magnetic field is calculated by subdividing the racetrack into filamentary wires. The finesse of the subdivision is set by the resolution box. Choose it wisely. Suppression of field divergence inside the conductor is automatic.
Case base = 0 (traditional BiotSavart racetrack)
If the base parameter is zero then the ends of the racetrack are semicircular.
Case base > 0 (general planar racetrack)
If the base parameter is not zero then the ends of the racetrack are quarter circles connected by a straight. The number of intermediate faces in each quarter turn is nturn/2, evaluated using integer arithmetic. This corresponds to counting the ends of the straight as a single face as shown above.