define_solenoid

• description: Define solenoid coils, from which static magnetic fields will be computed and imposed on the particle motion. The define_solenoid command permits defining a solenoid with a specified length, radius, symmetry, and current/field.

• example:

  &define_solenoid
     radius = 0.05, 
     z_start = 0.01, z_end = 0.02,
     Bz_peak = 1,
     turns = 100
  &end
  

  This command defines a 100-turn solenoid extending longitudinally between coordinates 1cm and 2cm, at a radius of 5cm. The current is adjusted to obtain a peak on-axis longitudinal B field of 1Tesla.

• synopsis and defaults:

  #namelist define_solenoid
          double radius = 0;
          double evaluation_radius_limit = 0;
          double z_start = 0;
          double z_end = 0;
          double current = 0;
          double Bz_peak = 0;
          long turns = 1;
          long symmetry = 0;
          STRING field_output = NULL;
  #end
  

• details:
  • radius: The radius of the coils in meters.
  • evaluation_radius_limit: The maximum radius in meters at which the solenoidal fields should be computed. This can save considerable CPU time if you are not interested in particles that go beyond a certain radius (e.g., you know they'll be lost).
  • z_start, z_end: The starting and ending longitudinal coordinate of the coils, in meters.
  • current: The current in each coil in Amperes (not Ampere-turns).
  • Bz_peak: The peak on-axis longitudinal magnetic field in Tesla desired from this solenoid. The current is scaled to achieve this value.
  • turns: The number of turns (or coils) in the solenoid.
  • symmetry: Either 0, 1, or -1 for no symmetry, even symmetry, or odd symmetry. For codes of , the resulting fields are those produced by the combination of the specified solenoid and another identical solenoid extending from -z_start to -z_end. If symmetry is 1 (-1), the field from the mirror solenoid adds to (subtracts from) the field due to the specified solenoid.
  • field_output: Requests output of the solenoid field to an SDDS file. This output is accumulated field from all solenoids defined up to this point, including the solenoid presently being defined.