ALaDyn `input.data` guide

Following here is a brief description of the input.data file required for the simulation parameters definition, through an example. This method is currently deprecated, in favour of the new input namelist.

Lines 1-2-3-4 / Grid parameters

7168,   3584,    1,     3500
  nx,     ny,   nz,  ny_part
100.0,    2.0
  k0, yx_rat

nx is the number of grid points in the x direction
for PWFA simulations, it is required that this number contains the number of cpus of the y and z domains defined by pey in order to be sure that FFTs are working as expected
ny is the number of points in the y direction
in order to be sure that the simulation is working as expected, it is better to always use a number that contains pey
nz is the number of points in the z direction; for a 2D simulaton, use nz = 1
in order to be sure that the 3D simulation is working as expected, it is better to always use here a number that contains the number of cpu assigned to split the z domain (mpi_ntot/pey)
nypart is the transverse size of the target, expressed in number of grid cell filled with particles (if the simulation is a 3D one, the target is a square in the xy plane)
k0 defines the resolution, being the numbero of points per μm along x, so that Δx = 1/k0 [μm]; please remember to set a value small enough to solve the skin depth
yxrat is the ratio between the resolution along x and y: Δy = yxrat/k0 [μm]; the resolution along z is the same as for y.

With those parameters, the full box size (in μm) is: Lx = nx / k0, Ly = yxrat * ny / k0, Lz = yxrat * nz / k0

Lines 5-6 / Numerical schemes

  2,   2,   0,     0
LPf, Der, str, iform

Lpf is the leapfrog order used in the integration scheme
Der is the order of the finite difference scheme
str has three possible different values:
0 for uniform grid
1 to enable stretching along transverse axes
2 to enable stretching along all axes, but for x it is only on the right side of the box (need testing)
iform has two possible different values:
0: (D_xJ_x,D_yJ_y,D_zJ_z) to be inverted on a grid (to be preferred) (energy conservation not guaranteed)
1: only (D_xJ_x) to be inverted on a grid
2: no charge preserving (use energy conservation algorithm)

Lines 7-8 / Driver and target models

  1,    3,     1
mdl, dmdl, ibeam

mdl has five possible different values
1 laser is p-polarized
2 laser is s-polarized
3 laser is circularly polarized
4 laser is described by its envelope approximation model
5 the driver is an electron beam. Its description must be given in a separate namelist file
6 the driver is a proton bunch. Its description must be given in a separate namelist file
dmdl has five possible different values
1 the simulation is done using just two species, electrons and protons
2 four species, e, p, C, Al, used in this way: [e+p]foam + [e+Al]bulk + [e+C+p]contaminants (Al is in reality a generic atom, defined by Z_i and A_i, while C is hard coded: we use Al in this readme since it is the common experimental choice, while for C it is an experimental mandatory choice - but it will be lifted in the future)
3 three species, e, p, C, in one layer: [e+C+pn]bulk (mind the n*, managed with nsb) (C is in reality a generic atom, defined by Z_i and A_i: we use C in this readme since it is the common experimental choice)
4 three species, e, p, Al, used in this way: [e+p]foam + [e+Al]bulk + [e+p]contaminants
5 three species, e, p, Al, identic to case 4, but with the contaminant layer mass limited
ibeam: for PWFA (model_id #5/#6):
0
1
2

Lines 9-10 / Number and type of particle species

  0,   0,   0,   3,   1
ibx, iby, ibz, nsp, nsb

nsp is the number of species (be careful and coherent with dmdl)
nsb, used with dmdl=3, defines the ratio n between the number of C ions and protons, to form CH_n

Lines 11-12 / Ionization status and schemes

    4,         11,        13,               26.98
ion_min(1),ion_max(1),atomic_number(1),mass_number(1)
    1,         1,          1,         1.0
ion_min(2),ion_max(2),atomic_number(2),mass_number(2)
    0,       0
ionz_lev,ionz_model,

ion_min
ion_max
atomic_number
mass_number
ionz_lev
ionz_model

Lines 13-14 / Initial temperatures of the species

 0.0003 ,    0.0 ,    0.0 ,    0.0
t0_pl(1),t0_pl(2),t0_pl(3),t0_pl(4)

Lines 15-16-17-18 / Number of particles per cell

   12, 4, 4, 4, 4, 4
np_xc
    9, 3, 4, 4, 4, 4
np_yc

First two are the number of electrons and ions per cell along x/y in the bulk, second two numbers refer to the front layer and third two to the contaminants. A special case is dmdl=3, in which the first indicates the number of electrons, the second the number of protons (to be multiplies by nsb) and the third is the number of ions; in this case the other numbers are not important.

Describing the previous example, it means that, along x:

n_e^x = 9, n_i^x = 4, in the central layer (bulk)
n_e^x = 3, n_i^x = 3, in the frontal layer (foam)
n_e^x = 6, n_i^x = 6, in the contaminant layer

n_e^x = 0 in the first np_xc position just means to ignore the plasma and do just a laser propagation simulation.

np_yc: the same as np_xc, this describes the number of particles per cell along transverse directions (valid also for z for 3D simulations)

Lines 19-20 / Laser parameters

16.5, 16.5, 33.0, 6.2,  3.0,  0.8
  tf,   xc,   wx,  wy,   a0, lam0

these lines are valid only for ibeam=1

xc is the position (in μm) along x of the central point of the laser envelope
tf is the distance (in μm) after which the laser is focused; so the focus is at xf = xc + tf
wx is twice the longitudinal waist, corresponding to the total laser length, which is twice the FWHM. For example, if we have a 40 fs FWHM Ti:Sa laser, we should write for wx=33 μm because:

    (40 fs/3.333)*2*1.37 = 33 μm
    40/3.3333 is done to convert fs to μm
    *2 is to convert from FWHM to full length
    *1.37 is to convert from laser intensity to fields: usually we receive from experiments the FWHM of the laser intensity, but we set the length of fields and the FWHM of a cos4 has to be converted to the FWHM of a cos2: FWHM(cos4)=FWHM(cos2)/1.37

wy is the transverse waist FWHM (in μm)
a is the laser adimensional parameter: a₀=eA/(m_e c²)
lam0 is the laser wavelength (in μm)

Lines 21-22 / Target shape parameters

0.0, 0.0, 2.0, 0.0, 0.08, 0.0, 0.01
 lx

lx(1) is the length of the upstream layer (foam or preplasma), having density n1/nc
lx(2) is the length of the ramp (linear or exponential depending on the mdl) connecting the upstream layer with the central one (made with bulk particles)
lx(3) is the length of the central layer (bulk), having density n2/nc
lx(4) is the length of the ramp (linear), connecting the bulk with the contaminants (made with bulk particles)
lx(5) is the length of the downstream layer (contaminants), having density n3/nc
lx(6) is the angle α of incidence, between the laser axis and the target plane
lx(7) is the offset between the end of the laser and the beginning of the target (if zero, the target starts right at the end of the laser pulse). The offset is calculated before laser rotation, so mind the transverse size if lx(6) ≠ 0, in order to avoid laser initialization inside the target.

Lines 23-24 / Target shape parameters

0.0, 0.0
 ly

ly(1) defines the wire size
ly(2) defines the interwire size

Lines 25-26 / Target density parameters

 100.0,   1.0,  10.0
 n2/nc, n1/nc, n3/nc

n2/nc is the density in the central layer (bulk)
n1/nc is the density in the upstream layer (foam/preplasma)
n3/nc is the density in the downstream layer (contaminants)

Lines 27-28 / Moving window

    20, 100.0, 150.0,     1.0
wnd_sh,  w_in, w_end, w_speed

wsh is the number of time steps after which the moving-window is called, repeatedly
win is the absolute time at which the window starts moving
wend is the absolute time at which the window stops moving
wspeed is the β speed of the moving window

Lines 29-30 / Output manager

  10,  200,     3,    1,     0,     0
nout, iene, nvout, nden, npout, nbout

nout is the number of binary outputs during the relative time of the simulation
iene is the number of text outputs during the relative time of the simulation
nvout is the number of fields written. For a 2D P-polarized case, we have just 3 fields, E_x, E_y and B_z; in all the other cases there are 6 fields with these IDs: 1=E_x, 2=E_y, 3=E_z, 4=B_x, 5=B_y, 6=B_z. At each nout step, every field with ID ≤ nf will be dumped.
nden can have three different values; every output is divided by species on different files:
1: writes only the particle density n on the grid
2: writes also the energy density n ･ gamma on the grid
3: writes also the currents J on the grid
npout
1: writes only the electron phase space
2: writes only the proton phase space
in general it writes only the phase space of the n-th species, with n=npv; if n=npv>nps, it writes the phase spaces of all the particle species
nbout

Lines 31-32 / Output subsampling

  1,    1
jmp, pjmp

jmp: jump on grid points; if jmp=2, it means that each processor is going to write only one point every two. Mind that it's extremely important that jmp is a divisor of the number of grid points per processor, otherwise the grid output will be corrupted
pjmp: jump on particles; if pjmp=2, it means that each processor is going to write the phase space of just one particle every two.

Lines 33-34 / Particle box to be dumped

 0.0, 100.0,  20.0
 xp0,   xp1, ypmax

In the dump we will find only particles contained inside the box defined by xp0 < x < xp1
In the dump we will find only particles contained in the box |{y,z}| < ypmax

Lines 35-36 / Simulation time settings

100.0,  0.8
 tmax,  cfl

tmax is the relative time (in μm, because it is multiplied by c) that the simulation is going to be evolved. Being relative, it's going to be added to the time eventually already reached before the restart. To obtain the time in fs, you have to divide it by 0.299792458 [speed of light in μm/fs]
cfl is the Courant–Friedrichs–Lewy parameter ( Wikipedia CFL-parameter page )

Lines 37-38 / Restart manager and processor settings

  0,     0,    0,  64
new, id_ew, dump, pey

new: identifies if a simulation is new new=0 (data is recreated from initial conditions) or if it is a restart new=1 (dump are going to be read)
id_ew identifies the starting number of the output files (if new=0) or the last one written in the previous step (if new=1)
dump
1: each processor will dump a binary file for every nout in order to enable restart
0: dumps are suppressed
pey identifies the number of processors used for 2D simulations, or how many processors are going to be used for the y domains (mpi_ntot/pey is the number of processors used for the z domains) for 3D simulations.

Guide

Old input guide

ALaDyn input.data guide