pwfa.inp

pic 模拟程序！面向对象

pwfa.inp
{

Here we look at the generation of a large-amplitude wakefield by a
very short ( < 50 fs), high intensity ( > 1e18 W/cm^2) laser pulse.
The pulse is so short, in order to make the simulation as fast as
possible for initial work.  We use a laser wavelength of 1 micron
and  and a minimum spot size of 5 micron in order to connect with
previous work by Rodolfo Giacone and Brad Shadwick.  Otherwise, the 
parameters are comparable to those used in the l'OASIS experiments 
at LBNL.

Pulse with transverse Gaussian profile and z polarization is launched from
the left boundary.  The longitudinal profile is a truncated Gaussian.

Cartesian geometry, with a pre-ionized electron plasma and a stationary
background of He++ ions.  The primary goal is to see how the plasma wake 
for a pre-ionized plasma differs from that for a laser pulse that must
create its own plasma.

This is derived from pwfaHe.inp -- here we replace the neutral He gas
with a pre-ionized electron plasma.
}

Variables
{
// General numerical parameters
  PI = 3.14159

// **********************************************************************
// General physical parameters
// **********************************************************************
  electronMass = 9.1094e-31 
  electronCharge = -1.6022e-19
  permit = 8.8542e-12 
  speedLight = 2.9979e8
  speedLight2 = speedLight*speedLight 
  electronCharge2 = electronCharge*electronCharge 
  qOverM = electronCharge/electronMass

  ionCharge = -electronCharge
  unitMassMKS = electronMass / 5.48579903e-04
  hydrogenMassNum = 1.00797
  hydrogenMass = unitMassMKS * hydrogenMassNum
  HeMassNum = 4.0026
  HeMass = unitMassMKS * HeMassNum

// **********************************************************************
// Plasma parameters
// **********************************************************************
//   Here, we specify a zero plasma density, because we launch the laser
//   pulse into a vacuum region.  Down below, we define the parameters
//   used for loading the initial electron plasma into the simulation.
  elecPlasmaDensity =  0.0 
  elecPlasmaFreq = sqrt(electronCharge*qOverM*elecPlasmaDensity/permit)
 
// **********************************************************************
// Laser pulse parameters - y polarization
// **********************************************************************
//   We are modeling a laser pulse with wavelength of 0.8 micron, a
//   FWHM pulse length of 6.7 fs, a peak intensity of 3 x 10^18 W/cm^2
//   and a minimum laser spot size of 5 micron.
//
  peakLaserIntensity = 3e+18  // W/cm^2
  pulseLengthFWHM = 6.7e-15
  RMStoFWHMfactor = 2. * sqrt( ln(2.) )
  FWHMtoTotalFactor = sqrt( ln(2.) )
  pulseLengthRMS = pulseLengthFWHM / RMStoFWHMfactor
  pulseLengthTotal = pulseLengthFWHM * FWHMtoTotalFactor

  laserWavelength = 1.0e-06
  laserFrequency = 2.*PI*speedLight/laserWavelength

  // We must convert the intensity to MKS units
  peakLaserIntensityMKS = peakLaserIntensity * 1.0e+04
  peakElectricField = sqrt(2.*peakLaserIntensityMKS/speedLight/permit)

// **********************************************************************
// Grid parameters
// **********************************************************************
// We must resolve the laser wavelength
  Nx = 512
  Ny = 256

  Lx = 30.0e-06
  Ly = 50.0e-06

  dx = Lx / Nx
  dy = Ly / Ny

  d = 1. / sqrt( 1./(dx*dx) + 1./(dy*dy) )
  timeStep = 0.7 * d / speedLight

// **********************************************************************
// More laser parameters:
// **********************************************************************
// We model the laser pulse envelope as a Gaussian (nPulseShape=1).
  nPulseShape = 1
  pulseLength  = pulseLengthTotal * speedLight

// Here we specify the waist size, Rayleigh length, etc.
// These parameters are for a pulse with y-polarization.
  waistSize = 5.0e-06 
  angFreq = laserFrequency
  angFreq2 = angFreq * angFreq
  waveVector = sqrt( (angFreq2-elecPlasmaFreq*elecPlasmaFreq) / speedLight2 )
// For waistSize = 5e-6 and wavelength = 1e-6, the Rayleigh length is 78.5e-6
  rayleighLength = waistSize * waistSize * waveVector / 2.
  waistLocation = Lx


// **********************************************************************
// Plasma parameters
// **********************************************************************
  plasmaDensityMKS = 3.0e+25
  simulationVolume = Lx * Ly * 1.0
  totalNumPlasma = plasmaDensityMKS * simulationVolume
  numPtclsPerCell = 8
  numCells = Nx * Ny
  numPlasmaPtcls = numPtclsPerCell * numCells
  plasmaNumRatio = totalNumPlasma / numPlasmaPtcls

  numZeroCells = 50
  numFlatCells = Nx-100
  numRampCells = Nx - numFlatCells - numZeroCells
  zeroEnd = (numZeroCells + .5) * dx
  rampEnd = (numZeroCells + numRampCells + .5) * dx

// This is the desired delay time before the moving window algorithm activates.
  movingWindowDelay = (Nx-10) * dx / speedLight
}

Region
{
Grid
{
  J = Nx 
  x1s = 0.0
  x1f = Lx 
  n1 = 1.0 
  K = Ny 
  x2s = 0.0
  x2f = Ly 
  n2 = 1.0
  Geometry = 1
}

Control
{
  dt = timeStep

// Turn on the moving window algorithm.
  movingWindow = 1
  shiftDelayTime = movingWindowDelay
}


// Define the electrons
Species
{
  name = electrons
  m = electronMass 
  q = electronCharge 
  particleLimit = 2.0e+06 // prevents out-of-control growth in # of ptcls
}


// Load the plasma electrons over the entire simulation region, but
//   leave the last dx strip of cells empty, because this strip must
//   be handled separately to accomodate the moving window algorithm.
Load
{
  speciesName = electrons
  density = plasmaDensityMKS
  x1MinMKS = 0.0
  x1MaxMKS = Lx - dx
  x2MinMKS = 0.0
  x2MaxMKS = Ly
  np2c = plasmaNumRatio

  analyticF = plasmaDensityMKS * step(x1-zeroEnd) * ( ramp( (x1-zeroEnd)/(rampEnd-zeroEnd) ) * step(rampEnd-x1) + step(x1-rampEnd) * step(Lx-0.5*dx-x1) )

// Specify loading that is more uniform than random
  LoadMethodFlag = 1
}

// Load the plasma electrons into the last dx strip of cells, which was
//   omitted by the load instruction above.
Load
{
// Name this load group "shiftLoad" so that the moving window algorithm
//   knows to invoke it every time the simulation window is shifted.
  Name = shiftLoad
  speciesName = electrons
  density = plasmaDensityMKS

  x1MinMKS = Lx - dx
  x1MaxMKS = Lx
  x2MinMKS = 0.0
  x2MaxMKS = Ly
  np2c = 2 * plasmaNumRatio

// Specify loading that is more uniform than random
  LoadMethodFlag = 1
}


// Define the He++ ions
Species
{
  name = HePlusPlus
  m = HeMass
  q = 2*ionCharge
}


// Load the plasma ions over the entire simulation region.
Load
{
  speciesName = HePlusPlus
  // There's one He++ ion for every two electrons
  density = 0.5*plasmaDensityMKS
  x1MinMKS = 0.0
  x1MaxMKS = Lx
  x2MinMKS = 0.0
  x2MaxMKS = Ly

  analyticF = 0.5*plasmaDensityMKS * step(x1-zeroEnd) * ( ramp( (x1-zeroEnd)/(rampEnd-zeroEnd) ) * step(rampEnd-x1) + step(x1-rampEnd) )

// This specifies a static uniform background (no macro-particles).
  np2c = 0
}

Diagnostic
{
	j1 = 0
	j2 = Nx
	k1 = 0
	k2 = Ny
	VarName = WaveDirDiagnostic
        polarizationEB = EzBy
        psd1dFlag = 1 // calculate the 1d power spectral density
        windowName = Blackman
	title = Wave Energy
	x1_Label = x
	x2_Label = y
	x3_Label = Wave Energy
}

// Launch the laser pulse
PortGauss
{
  j1 = 0 
  k1 = 0 
  j2 = 0 
  k2 = Ny 
  normal = 1

  A = 0
  C = 1.0 

// Wave (0)
  pulShp_p0 = nPulseShape
  tdelay_p0 = 0.0 
  pulLeng_p0 = pulseLength
  chirp_p0 = 0.0
  spotSize_p0 = waistSize
  waveLeng_p0 = laserWavelength
  focus_p0 = waistLocation
  amp_p0 = 0.0

// Wave (1)
  pulShp_p1 = nPulseShape
  tdelay_p1 = 0.0
  pulLeng_p1 = pulseLength
  chirp_p1 = 0.0
  spotSize_p1 = waistSize
  waveLeng_p1 = laserWavelength
  focus_p1 = waistLocation
  amp_p1 = peakElectricField

  EFFlag = 0 
  name = PortGauss
}


Conductor
{
  j1 = 0
  k1 = Ny 
  j2 = Nx 
  k2 = Ny 
  normal = -1
}


Conductor
{
  j1 = 0
  k1 = 0 
  j2 = Nx 
  k2 = 0 
  normal = 1
}


Conductor
{
  j1 = Nx
  k1 = 0
  j2 = Nx
  k2 = Ny
  normal = -1
}

}