shortbeam.inp

pic 模拟程序！面向对象

shortBeam
{

Low-energy attosecond electron pulse (from laser wakefield) --
  how long does it take to increase 10-fold in length and radius?

Moving window:
  Once the electron beam has fully entered the simulation region, 
  a moving window algorithm is invoked so that the beam can be 
  modeled for long times.

Boundary conditions:
  The simulation region is bounded by insulators.
}

// Define variables that can be used throughout this input file.

Variables
{
// First, define some useful constants.
	pi = 3.14159
	speedOfLight = 2.998e+08
	unitCharge = 1.602e-19
	electronCharge = -1 * unitCharge
	electronMass = 9.1095e-31
	electronMassEV = electronMass * speedOfLight * speedOfLight / unitCharge

// Next, define the parameters of the high-energy electron beam.
  beamGamma = 12
	beamEnergyEV = (beamGamma-1.) * electronMassEV
	beamTempEV = 0.0003 * beamEnergyEV
	totalNumBeam = 1.0e+06
	totalBeamCharge = totalNumBeam * electronCharge
	rmsBeamRadius = 800.e-09
	rmsBeamLength = 9.e-09
	rmsBeamTime = rmsBeamLength / speedOfLight
	radialCutoffFac = 3
	axialCutoffFac = 3
	totalBeamRadius = radialCutoffFac * rmsBeamRadius
	totalBeamLength = 2 * axialCutoffFac * rmsBeamLength
	beamAspectRatio = totalBeamLength / totalBeamRadius
  totalBeamArea = pi * totalBeamRadius * totalBeamRadius
  rmsBeamVolume = pi * rmsBeamRadius * rmsBeamRadius * rmsBeamLength
  rmsBeamEmittanceNormPiMRad = 1.0e-08  // not used!

// Define the number of grids in R and Z
	simRadiusOverBeamRadius = 1.5
	simLengthOverBeamLength = 50
	numRgridsAcrossBeam = 8
	numZgridsAcrossBeam = 24
	numRgrids = numRgridsAcrossBeam * simRadiusOverBeamRadius
	numZgrids = numZgridsAcrossBeam * simLengthOverBeamLength
	numCells = numRgrids * numZgrids

// Number of beam particles
	numBeamPtclsPerCell = 10
	numBeamCells = numRgridsAcrossBeam * numZgridsAcrossBeam
	numBeamPtcls = numBeamPtclsPerCell * numBeamCells
	beamNumRatio = totalNumBeam / numBeamPtcls

// Intermediate calculations for modeling Gaussian shape of the beam.
	invSigRsq = 1.0 / ( rmsBeamRadius * rmsBeamRadius )
	invSigZsq = 0.5 / ( rmsBeamLength * rmsBeamLength )
	invSigTsq = invSigZsq * speedOfLight * speedOfLight

// Calculate the size of the simulation region, grid spacings, time step.
// We are assuming the same grid size in both z and r	
  maxRadiusMKS = simRadiusOverBeamRadius * totalBeamRadius
  maxLengthMKS = simLengthOverBeamLength * totalBeamLength
	rGridSize = maxRadiusMKS / numRgrids
	zGridSize = maxLengthMKS / numZgrids

  effGridSize = 1./sqrt(1./(zGridSize*zGridSize)+1./(rGridSize*rGridSize))
	timeStep = 0.999 * effGridSize / speedOfLight

// This is the desired delay time before the moving window algorithm activates.
	movingWindowDelay = 0.95 * maxLengthMKS / speedOfLight

// Calculate peak currents for defining emission of the beam.
  peakCurrentDensity=totalBeamCharge*speedOfLight/rmsBeamVolume/sqrt(2.*pi)
	peakCurrent = peakCurrentDensity * totalBeamArea
	pulseLengthSec = totalBeamLength / speedOfLight
  oneHalfPulse = pulseLengthSec/2.
  oneEighthPulse = pulseLengthSec/8.
  threeEighthsPulse = 3.*oneEighthPulse
  sevenEighthsPulse = 7.*oneEighthPulse
}

// This simulation has only one "region", which contains grid, all particles, etc.
Region
{

// Define the grid for this region.
Grid
{

// Define number of grids along Z-axis and physical coordinates.
	J = numZgrids
	x1s = 0.0
	x1f = maxLengthMKS
	n1 = 1.0

// Define number of grids along R-axis and physical coordinates.
	K = numRgrids
	x2s = 0.0
	x2f = maxRadiusMKS
	n2 = 1.0
}

// Specify "control" parameters for this region
Control
{
// Specify the time step.
	dt = timeStep

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

// Define the beam electrons.
Species
{
	name = electrons
	m = electronMass
	q = electronCharge
}

// Define the beam emitter, which introduces the beam into the simulation.

BeamEmitter
{
	speciesName = electrons
	I = peakCurrent

// Define the 2-D function F(x,t) that specifies beam emission profile.
  xtFlag = 3
  F=exp(-invSigRsq*x*x)*exp(-invSigTsq*(t-oneHalfPulse)*(t-oneHalfPulse))*step(pulseLengthSec-t)

// Macroparticles are emitted from the left boundary, close to the axis of symmetry.
	j1 = 0
	j2 = 0
	k1 = 0
	k2 = numRgridsAcrossBeam
	normal = 1
	np2c = beamNumRatio

// Emit particles, directed along the Z-axis,  with specified energy and temperature.
	units = EV
	v1drift = beamEnergyEV
	v1thermal = beamTempEV
	v2thermal = 0.0
	v3thermal = 0.0
}

// Specify an insulator along the left boundary.  This serves as a
//   particle boundary condition (catches particles that leave the
//   simulation) and minimizes perturbations to the fields.

Dielectric
{
	j1 = 0
	j2 = 0
	k1 = 0
	k2 = numRgrids
	normal = 1
}

// Specify an insulator along the radial boundary.

Dielectric
{
	j1 = 0
	j2 = numZgrids
	k1 = numRgrids
	k2 = numRgrids
	normal = -1
}

// Specify a perfect conductor along the right boundary.
// The fields are zero here anyway, and this helps to suppress
//   an instability in which Er and Bphi suddenly begin to
//   grow rapidly at this boundary.

Conductor
{
	j1 = numZgrids
	j2 = numZgrids
	k1 = numRgrids
	k2 = 0
	normal = -1
}

// Define the cylindrical symmetry axis.
CylindricalAxis
{
	j1 = 0
	j2 = numZgrids
	k1 = 0
	k2 = 0
	normal = 1
}

}