1. Distribution Command
Distribution Type  Description 


Initial distribution read in from text file provided by user see Section [fromfiledisttype]. 

Initial distribution generated using Gaussian distribution(s) see Section [gaussdisttype]. 

Initial distribution generated using flattop distribution(s) see Section [flattopdisttype]. 

Initial distribution generated using binomial distribution(s) see Section [binomialdisttype]. 

For dark current and multipacting simulations. This type of distribution will not be covered in this chapter, see instead Chapter [femiss]. 

For dark current and multipacting simulations. This type of distribution will not be covered in this chapter, see instead Chapter [femiss]. 

Legacy. Special case of 

Legacy. Special case of 
The distribution command is used to introduce particles into an OPAL simulation. Like other OPAL commands see Chapter [format], the distribution command is of the form:
Name:DISTRIBUTION, TYPE = DISTRIBUTION_TYPE, ATTRIBUTE #1 =, ATTRIBUTE #2 =, . . . ATTRIBUTE #N =;
The distribution is given a name (which is used to reference the distribution in the OPAL input file), a distribution type, and a list of attributes. The types of distributions that are supported are listed in Table [disttypes]. The attributes that follow the distribution type further define the particle distribution. Some attributes are universal, while others are specific to the distribution type. In the following sections we will define the distribution attributes, starting with the general, or universal attributes. (Note that, in general, if a distribution type does not support a particular attribute, defining a value for it does no harm. That attribute just gets ignored.)
1.1. Units
The internal units used by OPALt and OPALcycl are described in
Section [variablesopalt,variablesopalcycl]. When defining a
distribution, both OPALt and OPALcycl use meters for length and
seconds for time. However, there are different options for the units
used to input the momentum. This is controlled with the INPUTMOUNITS
attribute, defined in Table [distattrinputmounits].
Attribute Name  Value  Description 



Use no units for the
input momentum (e.g. 


Use the units eV for
the input momentum (e.g. 
1.2. General Distribution Attributes
Once the distribution type is chosen, the next attribute to specify is
the EMITTED
attribute, which is defined in Table [distattremitted].
The EMITTED
attribute controls whether a distribution is injected or
emitted. An injected distribution is placed in its entirety into the
simulation space at the start of the simulation. An emitted beam is
emitted into the simulation over time as the simulation progresses (e.g.
from a cathode in a photoinjector simulation). Currently, only OPALt
supports emitted distributions. The default is an injected
distribution.
Attribute Name  Value  Description 



The distribution is injected into the
simulation in its entirety at the start of the simulation. The particle
coordinates for an injected distribution are defined as in
Section [variablesopalt,variablesopalcycl]. Note that in OPALt the
entire distribution will automatically be shifted to ensure that the



The distribution is emitted into the simulation over time as the simulation progresses. Currently only OPALt supports this type of distribution. In this case, the longitudinal coordinate, as defined by Section [variablesopalt], is given in seconds instead of meters. Early times are emitted first. 
Depending on the EMITTED
attribute, we can specify several other
attributes that do not depend on the distribution type. These are
defined in
Section [universaldistattributes,injecteddistattributes,emitteddistattributes]
in Table [distattruniversal,distattrinjected,distattrsemitted].
1.2.1. Universal Attributes
Attribute Name  Default Value  Units  Description 



None 
Echo initial distribution to text file data/<basename > DIST.dat_. 


None 
Makes the generation scalable with respect of number of particles. The result depends on the number of cores used. 

1.0 
None 
Weight of distribution when used in a distribution list see Section [distlist]. 

0 
None 
The distribution (beam) will be broken up into 

1.0 
None 
Value used to scale the 

1.0 
None 
Value used to scale the 

1.0 
None 
Value used to scale the x momentum,


1.0 
None 
Value used to scale the y momentum,


1.0 
None 
Value use to scale the z momentum,


0.0 
m 
Distribution is shifted in 

0.0 
m 
Distribution is shifted in 

0.0 
Section [unitsdistattributes] 
Distribution is shifted
in 

0.0 
Section [unitsdistattributes] 
Distribution is shifted
in 

0.0 
Section [unitsdistattributes] 
Distribution is shifted
in 

0.0 
Section [unitsdistattributes] 
Tracer particle which is written also into data/track_orbit.dat 

0.0 
Section [unitsdistattributes] 
Tracer particle which is written also into data/track_orbit.dat 
1.2.2. Injected Distribution Attributes
Attribute Name  Default Value  Units  Description 


1.0 
None 
Value used to scale the 

0.0 
m 
Distribution is shifted in 
1.2.3. Emitted Distribution Attributes
Attribute Name  Default Value  Units  Description 


1.0 
None 
Value used to scale the 

0.0 
s 
Distribution is emitted later by this amount relative to the reference particle. 

1 
None 
Number of time steps to take during emission. The simulation time step will be adjusted during emission to ensure that this many time steps will be required to emit the entire distribution. 

None 
None 
Emission model to use when emitting particles from cathode see Section [emissionmodel]. 
1.3. FROMFILE
Distribution Type
The most versatile distribution type is to use a user generated text file as input to OPAL. This allows the user to generate their own distribution, if the built in options in OPAL are insufficient, and have it either injected or emitted into the simulation. In Table [distattrfromfile] we list the single attribute specific to this type of distribution type.
Attribute Name  Default Value  Units  Description 


None 
None 
File name for text file containing distribution particle coordinates. 
An example of an injected FROMFILE
distribution definition is:
Name:DISTRIBUTION, TYPE = FROMFILE, FNAME = "text file name";
an example of an emitted FROMFILE
distribution definition is:
Name:DISTRIBUTION, TYPE = FROMFILE, FNAME = "text file name", EMITTED = TRUE, EMISSIONMODEL = None;
The text input file for the FROMFILE
distribution type has slightly a
slightly different format, depending on whether the distribution is to
be injected or emitted. The injected file format is defined in
Table [fromfileinjfileformat]. The emitted file format is defined in
Table [fromfileemitfileformat].
N  













. 

. 







N  













. 

. 







Note that for an emitted FROMFILE
distribution, all of the
particle’s time, t
, coordinates will be shifted to
negative time (if they are not there already). The simulation clock will
then start at t = 0
and distribution particles will be
emitted into the simulation as the simulation progresses. Also note
that, as the particles are emitted, they will be modified according to
the type of emission model used. This is defined by the attribute
EMISSIONMODEL
, which is described in Section [emissionmodel]. A choice
of NONE
for the EMISSIONMODEL
(which is the default) can be defined
so as not to affect the distribution coordinates at all.
To maintain consistency N
and NPART
from the BEAM
command in Chapter [beam] must be equal.
1.4. GAUSS
Distribution Type
As the name implies, the GAUSS
distribution type can generate
distributions with a general Gaussian shape (here we show a
onedimensional example):
f(x) = \frac{1}{\sqrt{2 \pi}} e^{\frac{(x  \bar{x})^{2}}{2 \sigma_{x}^{2}}}
where \bar{x}
is the average value of x
.
However, the GAUSS
distribution can also be used to generate an
emitted beam with a flat top time profile. We will go over the various
options for the GAUSS
distribution type in this section.
1.4.1. Simple GAUSS
Distribution Type
We will begin by describing how to create a simple GAUSS
distribution
type. That is, a simple 6dimensional distribution with a Gaussian
distribution in all dimensions.
Attribute Name  Default Value  Units  Description 


0.0 
m 
RMS width, 

0.0 
m 
RMS width, 

0.0 
m 
RMS radius, 

0.0 
m 
RMS length, 

0.0 
s 
RMS width, 

0.0 
Section [unitsdistattributes] 
Parameter


0.0 
Section [unitsdistattributes] 
Parameter


0.0 
Section [unitsdistattributes] 
Parameter


3.0 
None 
Defines transverse distribution cutoff in the


3.0 
None 
Defines transverse distribution cutoff in the


3.0 
None 
Defines transverse distribution cutoff in the


3.0 
None 
Defines longitudinal distribution cutoff in
the 

3.0 
None 
Defines cutoff in 

3.0 
None 
Defines cutoff in 

3.0 
None 
Defines cutoff in 
In Table [distattrgauss] we list the basic attributes available for a
GAUSS
distribution. We can use these to create a very simple GAUSS
distribution:
Name:DISTRIBUTION, TYPE = GAUSS, SIGMAX = 0.001, SIGMAY = 0.003, SIGMAZ = 0.002, SIGMAPX = 0.0, SIGMAPY = 0.0, SIGMAPZ = 0.0, CUTOFFX = 2.0, CUTOFFY = 2.0, CUTOFFLONG = 4.0, OFFSETX = 0.001, OFFSETY = 0.002, OFFSETZ = 0.01, OFFSETPZ = 1200.0 USEEV = TRUE;
This creates a Gaussian shaped distribution with zero transverse
emittance, zero energy spread, \sigma_{x} = {1.0}\mathrm{mm}
,
\sigma_{y} = {3.0}\mathrm{mm}
,
\sigma_{z} = {2.0}\mathrm{mm}
and an average energy of:
W = {1.2}{MeV}
In the x
direction, the Gaussian distribution is cutoff at
x = 2.0 \times \sigma_{x} = {2.0}\mathrm{mm}
. In the
y
direction it is cutoff at
y = 2.0 \times \sigma_{y} = {6.0}\mathrm{mm}
. This distribution
is injected into the simulation at an average position of
(\bar{x},\bar{y},\bar{z})=({1.0}\mathrm{mm}, {2.0}\mathrm{mm}, {10.0}\mathrm{mm})
.
1.4.2. GAUSS
Distribution for Photoinjector
Attribute Name  Default Value  Units  Description 


0.0 
s 
Flat top time see Figure [flattop]. 

0.0 
s 
Rise time see Figure [flattop]. If defined will
override 

0.0 
s 
Fall time see Figure [flattop]. If defined will
override 

0 
None 
Sinusoidal oscillations can imposed on the flat top in Figure [flattop]. This defines the amplitude of those oscillations in percent of the average flat top amplitude. 

0 
None 
Defines the number of oscillation periods
imposed on the flat top, 
A useful feature of the GAUSS
distribution type is the ability to
mimic the initial distribution from a photoinjector. For this purpose we
have the distribution attributes listed in Table [distattremittedgauss].
Using them, we can create a distribution with the time structure shown
in Figure [flattop]. This is a half Gaussian rise plus a uniform
flattop plus a half Gaussian fall. To make it more convenient to mimic
measured laser profiles, TRISE
and TFALL
from
Table [distattremittedgauss] do not define RMS quantities, but instead
are given by (See also Figure [flattop]):
\begin{aligned}
\mathrm{TRISE} = t_{R} &= \left(\sqrt{2 \ln(10)}  \sqrt{2 \ln \left(\frac{10}{9} \right)} \right) \sigma_{R}\\
& = 1.6869 \sigma_{R} \\
\mathrm{TFALL} = t_{F} &= \left(\sqrt{2 \ln(10)}  \sqrt{2 \ln \left(\frac{10}{9} \right)} \right) \sigma_{F}\\
& = 1.6869 \sigma_{F}\end{aligned}
where \sigma_{R}
and \sigma_{F}
are the
Gaussian, RMS rise and fall times respectively. The flattop portion of
the profile, TPULSEFWHM
, is defined as (See also Figure [flattop]):
\mathrm{TPULSEFWHM} = \mathrm{FWHM}_{P} = t_\mathrm{flattop} + \sqrt{2 \ln 2} \left( \sigma_{R} + \sigma_{F} \right)
Total emission time, t_{E}
, of this distribution, is a
function of the longitudinal cutoff, CUTOFFLONG
see Table [distattrgauss], and is given by:
\begin{aligned}
t_{E}(\mathrm{CUTOFFLONG}) &= \mathrm{FWHM}_{P}  \frac{1}{2} (\mathrm{FWHM}_{R} + \mathrm{FWHM}_{F})
+ \mathrm{CUTOFFLONG} (\sigma_{R} + \sigma_{F}) \\
&= \mathrm{FWHM}_{P} + \frac{\mathrm{CUTOFFLONG}  \sqrt{2 \ln 2}}{1.6869} (\mathrm{TRISE} + \mathrm{TFALL})\end{aligned}
Finally, we can also impose oscillations over the flattop portion of
the laser pulse in Figure [flattop], t_\mathrm{flattop}
.
This is defined by the attributes FTOSCAMPLITUDE
and FTOSCPERIODS
from Table [distattremittedgauss]. FTOSCPERIODS
defines how many
oscillation periods will be present during the
t_\mathrm{flattop}
portion of the pulse. FTOSCAMPLITUDE
defines the amplitude of those oscillations in percentage of the average
profile amplitude during t_\mathrm{flattop}
. So, for
example, if we set \mathrm{FTOSCAMPLITUDE} = 5
, and the
amplitude of the profile is equal to 1.0
during
t_\mathrm{flattop}
, the amplitude of the oscillation will
be 0.05
.
1.4.3. Correlations for GAUSS
Distribution (Experimental)
Attribute Name  Default Value  Units  Description 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 


0.0 
Section [unitsdistattributes] 

To generate Gaussian initial distribution with dispersion, first we
generate the uncorrelated Gaussian inputs matrix
R=(R1,...,R_n)
. The mean of R_i
is
0
and the standard deviation squared is 1. Then we
correlate R
. The correlation coefficient matrix
\sigma
in x
, p_x
,
z
, p_z
phase space reads:
\sigma= \left[
\begin{array}{cccc}
1 &c_x &r51 &r61\\
c_x &1 &r52 &r62\\
r51 &r52 &1 &c_t\\
r61 &r62 &c_t &1
\end{array}
\right]
The Cholesky decomposition of the symmetric positivedefinite matrix
\sigma
is \sigma=C^{\mathbf{T}}C
, then the
correlated distribution is C^{\mathbf{T}}R
.
Note: Correlations work for the moment only with the Gaussian
distribution and are experimental, so there are no guarantees as to its
efficacy or accuracy. Also, these correlations will work, in principle,
for an emitted beam. However, recall that in this case,
z
in meters is replaced by t
in seconds, so
take care.
As an example of defining a correlated beam, let the initial correlation coefficient matrix be:
\sigma= \left[
\begin{array}{cccc}
1 &0.756 &0.023 &0.496\\
0.756 &1 &0.385 &0.042\\
0.023 &0.385 &1 &0.834\\
0.496 &0.042 &0.834 &1
\end{array}
\right]
then the corresponding distribution command will read:
Dist:DISTRIBUTION, TYPE = GAUSS, SIGMAX = 4.796e03, SIGMAPX = 231.0585, CORRX = 0.756, SIGMAY = 23.821e03, SIGMAPY = 1.6592e+03, CORRY = 0.999, SIGMAZ = 0.466e02, SIGMAPZ = 74.7, CORRZ = 0.834, OFFSETZ = 0.466e02, OFFSETPZ = 72e6, R61 = 0.496, R62 = 0.042, R51 = 0.023, R52 = 0.385;
1.5. FLATTOP
Distribution Type
The FLATTOP
distribution type is used to define hard edge beam
distributions. Hard edge, in this case, means a more or less uniformly
filled cylinder of charge, although as we will see this is not always
the case. The main purpose of the FLATTOP
is to mimic laser pulses in
photoinjectors, and so we usually will make this an emitted
distribution. However it can be injected as well.
1.5.1. Injected FLATTOP
The attributes for an injected FLATTOP
distribution are defined in
Table [distattrflattopinj,distattruniversal]. At the moment, we cannot
define a spread in the beam momentum, so an injected FLATTOP
distribution will currently have zero emittance. An injected FLATTOP
will be a uniformly filled ellipse transversely with a uniform
distribution in z
. (Basically a cylinder with an
elliptical cross section.)
Attribute Name  Default Value  Units  Description 


0.0 
m 
Hard edge width in 

0.0 
m 
Hard edge width in 

0.0 
m 
Hard edge radius. If nonzero 

0.0 
m 
Hard edge length in 
1.5.2. Emitted FLATTOP
Attribute Name  Default Value  Units  Description 


0.0 
m 
Hard edge width in 

0.0 
m 
Hard edge width in 

0.0 
m 
Hard edge radius. If nonzero 

0.0 
s 
RMS rise and fall of half Gaussian in flat top defined in in Figure [flattop]. 

0.0 
s 
Flat top time. See Figure [flattop]. 

0.0 
s 
Rise time. See Figure [flattop]. If defined will
override 

0.0 
s 
Fall time. See Figure [flattop]. If defined will
override 

0 
None 
Sinusoidal oscillations can imposed on the flat top in Figure [flattop]. This defines the amplitude of those oscillations in percent of the average flat top amplitude. 

0 
None 
Defines the number of oscillation periods
imposed on the flat top, 

None 
File name containing measured laser image. 


None 
Name of the file containing the laser image. 


0.0 
None 
Parameter defining floor of the background to be subtracted from the laser image in percent of the maximum intensity. 


Flip the laser profile in horizontal direction. 



Flip the laser profile in vertical direction. 



Rotate the laser profile
90 



Rotate the laser profile
180 



Rotate the laser profile
270 
The attributes of an emitted FLATTOP
distribution are defined in
Table [distattrflattopemit,distattruniversal]. The FLATTOP
distribution was really intended for this mode of operation in order to
mimic common laser pulses in photoinjectors. The basic characteristic of
a FLATTOP
is a uniform, elliptical transverse distribution and a
longitudinal (time) distribution with a Gaussian rise and fall time as
described in Section [gaussdisttypephotoinjector]. Below we show an
example of a FLATTOP
distribution command with an elliptical cross
section of 1mm by 2mm and a flat top, in time, 10ps long with a 0.5ps
rise and fall time as defined in Figure [flattop].
Dist:DISTRIBUTION, TYPE = FLATTOP, SIGMAX = 0.001, SIGMAY = 0.002, TRISE = 0.5e12, TFALL = 0.5e12, TPULSEFWHM = 10.0e12, CUTOFFLONG = 4.0, NBIN = 5, EMISSIONSTEPS = 100, EMISSIONMODEL = ASTRA, EKIN = 0.5, EMITTED = TRUE;
1.5.3. Transverse Distribution from Laser Profile (Under Development)
An alternative to using a uniform, elliptical transverse profile is to
define the LASERPROFFN
, IMAGENAME
and INTENSITYCUT
attributes from
Table [distattrflattopemit]. Then, OPALt will use the laser image as
the basis to sample the transverse distribution.
This distribution option is not yet available.
1.5.4. GUNGAUSSFLATTOPTH
Distribution Type
This is a legacy distribution type. A GUNGAUSSFLATTOPTH
is the
equivalent of a FLATTOP
distribution, except that the EMITTED
attribute will set to TRUE
automatically and the EMISSIONMODEL
will
be automatically set to ASTRA
.
1.5.5. ASTRAFLATTOPTH
Distribution Type
This is a legacy distribution type. A ASTRAFLATTOPTH
is the equivalent
of a FLATTOP
distribution, except that the EMITTED
attribute will
set to TRUE
automatically and the EMISSIONMODEL
will be
automatically set to ASTRA
. There are a few other differences with how
the longitudinal time profile of the distribution is generated.
1.6. BINOMIAL
Distribution Type
The BINOMIAL
type of distribution is based on [JohoDist]. The shape of
the binomial distribution is governed by one parameter m
.
By varying this single parameter one obtains the most commonly used
distributions for our type of simulations, as listed in
Table [binomdist].
m 
Distribution  Density  Profile 

0.0 
Hollow shell 


0.5 
Flat profile 


1.0 
Uniform 


1.5 
Elliptical 


2.0 
Parabolic 



Gaussian 


1.7. Emission Models
When emitting a distribution from a cathode, there are several ways in which we can model the emission process in order to calculate the thermal emittance of the beam. In this section we discuss the various options available.
1.7.1. Emission Model: NONE
(default)
The emission model NONE
is the default emission model used in
OPALt. It has a single attribute, listed in
Table [distattremitmodelnoneastra]. The NONE
emission model is very
simplistic. It merely adds the amount of energy defined by the attribute
EKIN
to the longitudinal momentum, p_{z}
, for each
particle in the distribution as it leaves the cathode.
Attribute Name  Default Value  Units  Description 


1.0 
eV 
Thermal energy added to beam during emission. 
An example of using the NONE
emission model is given below. This
option allows us to emit transversely cold (zero x and y emittance)
beams into our simulation. We must add some z momentum to ensure that
the particles drift into the simulation space. If in this example one
were to specify EKIN = 0
, then you would likely get strange results as
the particles would not move off the cathode, causing all of the emitted
charge to pile up at z = 0
in the first half time step
before the beam space charge is calculated.
Dist:DISTRIBUTION, TYPE = FLATTOP, SIGMAX = 0.001, SIGMAY = 0.002, TRISE = 0.5e12, TFALL = 0.5e12, TPULSEFWHM = 10.0e12, CUTOFFLONG = 4.0, NBIN = 5, EMISSIONSTEPS = 100, EMISSIONMODEL = NONE, EKIN = 0.5, EMITTED = TRUE;
One thing to note, it may be that if you are emitting your own
distribution using the TYPE = FROMFILE
option, you may want to set
EKIN = 0
if you have already added some amount of momentum,
p_{z}
, to the particles.
1.7.2. Emission Model: ASTRA
The ASTRA
emittance model uses the same single parameter as the NONE
option as listed in Table [distattremitmodelnoneastra]. However, in this
case, the energy defined by the EKIN
attribute is added to each
emitted particle’s momentum in a random way:
\begin{aligned}
p_{total} &= \sqrt{\left(\frac{\mathrm{EKIN}}{mc^{2}} + 1\right)^{2}  1} \\
p_{x} &= p_{total} \sin(\phi) \cos(\theta)) \\
p_{y} &= p_{total} \sin(\phi) \sin(\theta)) \\
p_{z} &= p_{total} {\cos(\theta)}
\end{aligned}
where \theta
is a random angle between 0
and
\pi
, and \phi
is given by
\phi = 2.0 \arccos \left( \sqrt{x} \right)
with x
a random number between 0
and
1
.
1.7.3. Emission Model: NONEQUIL
The NONEQUIL
emission model is based on an actual physical model of
particle emission as described in [flo:97, clen:2000, dowe:2009]. The
attributes needed by this emission model are listed in
Table [distattremitmodelnonequil].
Attribute Name  Default Value  Units  Description 


4.86 
eV 
Photoinjector drive laser energy. (Default is 255nm light.) 

4.31 
eV 
Photocathode work function. (Default is atomically clean copper.) 

7.0 
eV 
Fermi energy of photocathode. (Default is atomically clean copper.) 

300.0 
K 
Operating temperature of photocathode. 
An example of using the NONEQUIL
emission model is given below. This
model is relevant for metal cathodes and cathodes such as CsTe
.
Dist:DISTRIBUTION, TYPE = GAUSS, SIGMAX = 0.001, SIGMAY = 0.002, TRISE = 1.0e12, TFALL = 1.0e12, TPULSEFWHM = 15.0e12, CUTOFFLONG = 3.0, NBIN = 10, EMISSIONSTEPS = 100, EMISSIONMODEL = NONEQUIL, ELASER = 6.48, W = 4.1, FE = 7.0, CATHTEMP = 325, EMITTED = TRUE;
1.8. Distribution List
It is possible to use multiple distributions in the same simulation. We
do this be using a distribution list in the RUN
command
see Chapter [track]. Assume we have defined several distributions:
DIST1
, DIST2
and DIST3
. If we want to use just one of these
distributions in a simulation, we would use the following RUN
command
to start the simulation:
RUN, METHOD = "PARALLELT", BEAM = beam_name, FIELDSOLVER = field_solver_name, DISTRIBUTION = DIST1;
If we want to use all the distributions at the same time, then the command would instead be:
RUN, METHOD = "PARALLELT", BEAM = beam_name, FIELDSOLVER = field_solver_name, DISTRIBUTION = {DIST1, DIST2, DIST3};
In this second case, the first distribution (DIST1
) is the master
distribution. The main consequence of this is that all distributions in
the list will be forced to the same EMITTED
condition as DIST1
. So,
if DIST1
is to be emitted, then all other distributions in the list
will be forced to this same condition. If DIST1
is to be injected,
then all other distribution is the list will also be injected.
The number of particles in the simulation is defined in the BEAM
command see Chapter [beam]. The number of particles in each distribution
in a distribution list is determined by this number and the WEIGHT
attribute of each distribution (Table [distattruniversal]). If all
distributions have the same WEIGHT
value, then the number of particles
will be divided up evenly among them. If, however we have a distribution
list consisting of two distributions, and one has twice the WEIGHT
of
the other, then it will have twice the particles as its partner. The
exception here is any FROMFILE
distribution type. In this case, the
WEIGHT
attribute and the number of particles in the BEAM
command are
ignored. The number of particles in any FROMFILE
distribution type is
defined by the text file containing the distribution particle
coordinates. (Section [fromfiledisttype]).