###################################################################### 
# 
# File: simpleEm.pre 
# 
# Purpose: Simple electromagnetic simulation. 
# Shows vacuum propagation of a wave launched from 
# x-lower end of simulation. 
# 
###################################################################### 

########## 
# 
# Define variables in lines starting with ¿$¿ for later use 
# 
########## 

# Variable for the dimension simulation parameter 
$ NDIM = 3 # Number of dimensions in simulation (1, 2, or 3) 

# Variables for the grid input block 
# Number of cells along x, y, and z axes 
$ NX = 40 
$ NY = 20 
$ NZ = 20 
# Length of grid along x, y, and z axes 
$ LX = 1.6e-5 
$ LY = 5.e-5 
$ LZ = 5.e-5 
# Location of start point along x, y, and z axes in SI units 
$ XSTART = 0. 
$ YSTART = -0.5*LY 
$ ZSTART = -0.5*LZ 

# Variables for setting up the time step simulation parameter 
# Courant condition 
$ DXI = NX/LX 
$ DYI = NY/LY 
$ DZI = NZ/LZ 
$ DLI = math.sqrt(DXI*DXI + DYI*DYI + DZI*DZI) 
$ DL = 1./DLI 
$ LIGHTSPEED = 2.9979e8 
# Define 90% of Courant limit
$ DT = 0.9*DL/LIGHTSPEED 

# Variable for the moving window simulation parameter 
# Shift position - when pulse gets close to x-upper wall 
$ DSHFTPOS = 0.95*LX 

# Variables for setting up boundary condition input blocks 
# Number of cells along x, y, and z axes plus one guard cell 
$ NX1 = NX + 1 
$ NY1 = NY + 1 
$ NZ1 = NZ + 1 

# Variables for setting up pulse in boundary condition input block 
$ WAVELENGTH = 4.e-6 
$ FREQUENCY = LIGHTSPEED/WAVELENGTH 
$ PI = 3.1415926535897931 
$ OMEGA = 2.*PI*FREQUENCY 
$ KAY = 2.*PI/WAVELENGTH 
$ AMPLITUDE = 8.0e10 # peak amplitude of pulse in volts/meter 

########## 
# 
# Define the simulation parameters 
# 
########## 

# Parameters that can be overridden on the command line are 
# commented with (OR) 

# The dimension and precision of the simulation 
dimension = NDIM # (OR) 
floattype = float # (OR) 

# Time step and number of steps 
dt = DT 
nsteps = 250 # (OR) 

# Dump output into an HDF5 file every 250 time steps 
dumpPeriodicity = 250 # (OR) 

# Moving window 
downShiftDir = 0 # Shift along direction 0 
downShiftPos = DSHFTPOS # Start shifting at t = DSHFTPOS/(speed of light) 

########## 
# 
# Define the grid: the physical problem and the number of cells 
# 
########## 

<Grid globalGrid> 
  numPhysCells = [NX NY NZ] 
  lengths = [LX LY LZ] 
  startPositions = [XSTART YSTART ZSTART] 
</Grid> 

########## 
#
# Define the decomposition 
# 
########## 

<Decomp decomp> 
  periodicDirs = [1 2] # The periodic directions 
  decompType = regular 
</decomp> 

########## 
# 
# Define the electromagnetic field; describe the EM field¿s boundary 
# conditions 
# 
########## 

# The electromagnetic field is a Yee field, with z-polarized wave 
# launched from x-lower end of simulation, conductors x-lower and x-upper 
# 
<EmField myYeeEmField> 
  kind = yeeEmField # An FDTD EM field on a Yee mesh 

  # This boundary condition puts values of E_z on x-lower boundary 
  <BoundaryCondition xLowerWaveLauncher> 
    # The indices parameter determines which components of E_z are set. 
    # The length of indices must match that of amplitudes and phases, 
    # resulting in those being used for other components of E. 
    kind = variable               # Value given by a function 
    lowerBounds = [0 -1 -1]       # Lower cell limits for BC application 
    upperBounds = [1 NY1 NZ1]     # Upper cell limits for BC application 
    indices = [2] # z polarized 
    function = planeWavePulse     # Function used for E_z 
    # Below here are the parameters for the function. 
    # There should be one amplitude and one phase for each index. 
    amplitudes = [AMPLITUDE]      # Amplitudes for each of the indices 
    phases = [1.57]               # Phases for each of the indices 
    # The following parameters are used for all indices 
    k = [KAY 0 0 ]                # k-vector parameter for wave 
    omega = OMEGA                 # Angular frequency parameter for wave 
    vg = LIGHTSPEED               # Group velocity parameter for wave 
    widths = [5.e-6 1.e-5 1.e-5]  # Widths of pulses, along k, transverse 
    origin = [-5.e-6 0.e-5 0.e-5] # Origin parameter for wave 
  </BoundaryCondition> 

  # Set E_y to zero on x-lower boundary 
  <BoundaryCondition xLowerConductor> 
    kind = constant           # Value same at all cells 
    lowerBounds = [0 -1 -1]   # Lower cell limits for BC application 
    upperBounds = [1 NY1 NZ1] # Upper cell limits for BC application 
    # There should be one amplitude for each index 
    indices = [1]             # E_y set by this 
    amplitudes = [0.]         # E_y set to zero 
  </BoundaryCondition> 

    # Set E_y and E_z to zero on x-upper boundary 
  <BoundaryCondition xUpperConductor> 
    kind = constant             # Value same at all cells 
    lowerBounds = [NX -1 -1]    # Lower cell limits for BC application
    upperBounds = [NX1 NY1 NZ1] # Upper cell limits for BC application 
    # There should be one amplitude for each index 
    indices = [1 2]             # E_y and E_z set by this 
    amplitudes = [0. 0.]        # Values for E_y and E_z 
  </BoundaryCondition> 
</EmField>