integrate

• description: Defines integration parameters and begins integration. Allows specifying the integration time step, the total time to integrate, and other conditions of integration.

• example:

  &integrate
      dt_integration = 1e-12,
      start_time = 0,
      finish_time = 5e-9,
      status_interval = 128,
      space_charge = 1
  &end
  

  Starts integration of equations for particles and fields at a simulated time of 0, taking steps of 1ps, until reaching 5ns. Every 128 steps, status information is printed to the screen. Space charge is included.

• synopsis and defaults:

  &integrate
      double dt_integration = 0;
      double start_time = 0;
      double finish_time = 0;
      long status_interval = -1;
      long space_charge = 0;
      long check_divergence = 0;
      double smoothing_parameter = 0;
      double J_filter_multiplier = 0;  
      long terminate_on_total_loss = 0;
      STRING status_output = NULL;
      STRING lost_particles = NULL;
  &end
  

• details:
  • dt_integration: Simulation step size in seconds.
  • start_time: Simulation start time. Typically 0 for new runs. Ignored for runs that involve fields loaded from other simulations.
  • finish_time: Simulation stop time.
  • status_interval: Interval in units of a simulation step between status printouts.
  • space_charge: Flag requesting inclusion of space-charge in the simulation.
  • check_divergence: Flag requesting that status printouts include a check of the field values using the divergence equation.
  • smoothing_parameter: Specifies a simple spatial filter for the current density. The smoothing parameter, $s$, is used to compute two new quantities, $c_1 = 1-s$ and $c_2 = s/2$. The program smooths longitudinal variation for constant radius, using $A_o \rightarrow (A_- + A_+)c_2 + A_o c_1$, where $A_o$ is the central value and $A_\pm$ are the adjacent values to a grid point. This function is rarely used and I do not recommend it.
  • J_filter_multiplier: Specifies a simple time-domain filter for the current density. For each point on the grid, the new current density value $J(1)$ is replaced by $J(1)*(1-f) + J(0)*f$. This is an infinite impulse response filter. This function is rarely used and I do not recommend it.
  • terminate_on_total_loss: Flag requesting that when all simulation particles are lost (e.g., by hitting a wall or exiting the simulation), the simulation should terminate.
  • status_output: Provide the name of a file to which to write status information, including statistics on the beams and fields. File is in SDDS format.
  • lost_particles: Provide the name of a file to which to write information about particles that get lost. File is in SDDS format.