4.20 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, c₁ = 1 - s and c₂ = s∕2. The program smooths longitudinal variation for constant radius, using A_o → (A_-+A₊)c₂ +A_oc₁, where A_o is the central value and A_± 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.
  • auto_max_dt: if non-zero, dt_integration exceeding the maximum stable timestep is replaced by the maximum.