FLUKA: USRBDX
Previous Index Next
USRBDX
defines a detector for a boundary crossing fluence or current estimator
See also USRBIN, USRCOLL, USRTRACK, USRYIELD
The full definition of the detector may require two successive cards
(the second card, identified by the character '&' in any column from
71 to 78, must be given unless the corresponding defaults are
acceptable to the user)
For all SDUM
's except EN-NUCL and ENERGY:
First card:
WHAT(1)
= i1 + i2 * 10 + i3 * 100 + i4 * 10000, where i1, i2 i3, i4 have the
following meaning:
i1 = 1.0 : linear binning in energy and solid angle
= -1.0 : logarithmic binning in energy, linear in solid angle
= 2.0 : logarithmic binning in solid angle, linear in energy
= -2.0 : logarithmic binning in energy and solid angle
i2 = 0.0 : one way scoring
= +1.0 : two-way scoring
i3 = 0.0 : current scoring
= +1.0 : fluence scoring (inverse cosine-weighted)
i4 = 0.0 : group-wise scoring for low energy neutrons
=+/-1.0 : point-wise scoring for low energy neutrons
Default
= 1.0 (one-way current, linear in energy and solid
angle, groupwise scoring)
WHAT(2)
= (generalised) particle type to be scored
Default
= 201.0 (all particles)
WHAT(3)
= logical output unit
> 0.0 : formatted data are written on WHAT(3)
unit
< 0.0 : unformatted data are written on |WHAT(3)
| unit
Values of |WHAT(3)
| < 21 should be avoided (with the
exception of +11).
Default
= 11.0 (standard output unit)
WHAT(4)
= first region defining the boundary
(in case of one-way scoring this is the upstream region)
Default
= 1.0
WHAT(5)
= second region defining the boundary
(in case of one-way scoring this is the downstream region)
Default
= 2.0
WHAT(6)
= area of the detector in cm**2
Default
= 1.0 (fluence or current gets integrated over the
boundary area)
SDUM
= any character string (not containing '&') identifying the
detector (max. 10 characters)
Continuation card:
WHAT(1)
= maximum kinetic energy for scoring (GeV)
Default
: Beam momentum value according to the BEAM option
(if no BEAM card is given, 200 GeV)
WHAT(2)
= minimum kinetic energy for scoring (GeV)
Note that the lowest energy limit of the last neutron group
is 1.E-14 GeV (1.E-5 eV) for the 260 data set.
Default
= 0.0 if linear energy binning, 0.001 GeV otherwise
WHAT(3)
= number of energy intervals for scoring
Default
= 10.0
WHAT(4)
= maximum solid angle for scoring in sr
Default
= 2 pi for one-way estimators, 4 pi for two-way
WHAT(5)
= If linear angular binning: minimum solid angle for
scoring (sr)
Default
= 0.0
If logarithmic angular binning: solid angle of the first
bin (sr)
Default
= 0.001
WHAT(6)
= number of angular bins
Default
= 1.0 for linear angular binning, 3.0 otherwise
SDUM
= & in any position in column 71 to 78
For SDUM
= EN-NUCL:
The energy scale for all USRBDX estimators will be changed from energy
to energy per nucleon (for particles with baryon number = 0 or 1, i.e.
all elementary hadrons and leptons, nothing will be changed).
For SDUM
= ENERGY:
the energy scale for all USRBDX estimators will be changed to the default,
that is total kinetic energy.
Default
(option USRBDX not given): no boundary crossing estimator detector
IMPORTANT!
----------
Notes:
1) The results of a USRBDX boundary crossing estimator are given as
DOUBLE DIFFERENTIAL distributions of fluence or current in energy
and solid angle, in units of cm-2 GeV-1 sr-1 per incident primary,
EVEN WHEN ONLY 1 INTERVAL (BIN) HAS BEEN REQUESTED, which is often
the case for angular distributions. Thus, for example, when
requesting a fluence or current energy spectrum, with no angular
distribution, to obtain INTEGRAL BINNED results (fluence or current
in cm-2 PER ENERGY BIN per primary) one must multiply the value of
each energy bin by the width of the bin (even for logarithmic
binning), AND BY 2 pi or 4 pi (depending on whether one-way or
two-way scoring has been requested). This is done automatically
by the dedicated post-processing utility program USXSUW (see Note 8).
2) Angular distributions must be intended as distributions in solid angle
2 pi (1-cos(theta)), where theta is the angle between the particle
trajectory and the normal to the boundary at the point of crossing.
When logarithmic scoring is requested for angular distributions, all
intervals have the same logarithmic width (equal ratio between upper
and lower limit of the interval), EXCEPT THE FIRST ONE. The limits
of the first angular interval are zero (i.e. theta=0) and the solid
angle value indicated by the user with WHAT(5)
in the continuation card.
3) If the generalised particle is 208.0 (ENERGY) or 211.0 (EM-ENRGY),
the quantity scored is differential energy fluence (if
cosine-weighted) or differential energy current (energy crossing the
surface). In both cases the quantity will be expressed in GeV per
cm2 per energy unit per steradian per primary. That can sometimes
lead to confusion since GeV cm-2 GeV-1 sr-1 = cm-2 sr-1, where
energy does not appear. Note that integrating over energy and solid
angle one gets GeV/cm2.
4) The maximum number of boundary crossing detectors that the
user can define is 1100.
5) The logical output unit for the estimator results (WHAT(3)
of
the first USRBDX card) can be any one of the following:
- the standard output unit 11: estimator results will be
written on the same file as the standard FLUKA output
- a pre-connected unit (via a symbolic link on most UNIX systems,
ASSIGN under VMS, or equivalent commands on other systems)
- a file opened with the FLUKA command OPEN
- a file opened with a Fortran OPEN statement in a user-written
initialisation routine such as USRINI, USRGLO or SOURCE (see 13})
- a dynamically opened file, with a default name assigned by the
Fortran compiler (typically fort.xx or ftn.xx, with xx equal
to the chosen logical output unit number).
The results of several USRBDX detectors in a same FLUKA run can
be written on the same file, but of course only if they are all
in the same mode (all formatted, or all unformatted).
It is also possible in principle to write on the same file the
results of different kinds of estimators (USRTRACK, USRBIN, etc.)
but this is not recommended, especially in the case of an
unformatted file, because it would make very difficult any reading
and analysis.
6) When scoring neutron fluence or current, and the requested energy
interval overlaps with the structure of the low energy neutron groups,
one gets two separate tables if the default groupwise scoring is
is selected. In the lower one, interval boundaries are
forced to coincide with group boundaries. For the upper one, the
program uses the input energy limits and number of intervals to
estimate the desired interval width. The number of intervals above
the upper limit of the first low-energy neutron group is recalculated
according to such width, which is readjusted to match the number of
intervals with the least greater integer.
Note that the lowest energy limit of the last neutron group
is 1.E-14 GeV (1.E-5 eV) for the 260-group data set.
All group energy boundaries are listed in Table 10.4.1.1}.
7) If the scored fluence or current is that of a generalised particle
which includes neutrons (e.g. ALL-PART, ALL-NEUT, NUCLEONS, NUC&PI+-,
HAD-NEUT, and even ENERGY), the spectrum is presented in two
separate tables. One table refers to all non-neutron particles and
to neutrons with energies above the upper limit of the first low-energy
neutron group (20 MeV). In case an interval crosses 20 MeV, it will
include the contribution of neutrons with energy > 20 MeV and not that
of neutrons with energy < 20 MeV. The second table refers only to
low-energy neutrons and its interval structure is that of the neutron
energy groups.
8) A program USXSUW is available with the normal FLUKA code distribution
in directory $FLUPRO/flutil. USXSUW reads USRBDX results in binary
form from several runs and allows to compute standard deviations. It
returns double differential and cumulative fluence or current, with the
corresponding percent errors, in a file (_sum.lis), and in another file
(_tab.lis) formatted for easy plotting. It also returns a binary file
that can be read out in turn by USXSUW. The content of this file is
statistically equivalent to that of the sum of the files used to
obtain it, and it can replace them to be combined with further
output files if desired (the USXSUW program takes care of giving it
the appropriate weight).
For each detector, the _sum.lis file starts with a header summarizing
the detector characteristics. It then gives the differential and
cumulative fluxes as a function of energy, integrated over solid
angle (single differential). Below, the angular binning is detailed,
and the results of the double differential fluxes are given
(angular distributions per each energy bin).
The _tab.lis file presents the same data (except for the cumulative
values), stripped down to only keep easily plottable distributions.
When using Flair and choosing a detector in the drop-down list,
the user has the option to select the single differential data,
or the double differential one from any one of the angular bins.
In order to obtain an integrated value inside a specific solid angle
bin, the data of the bin must then be multiplied by its width.
Example:
USRBDX 101.0 ANEUTRON 21.0 3.0 4.0 400.0 AntiNeu
USRBDX 5.0 0.0 200.0 0.0 0.0 0.0 &
Previous Index Next
