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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)

     First card:

     
WHAT(1)
= i1 + i2 * 10 + i3 * 100, where i1, i2 i3 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)
Default
= 1.0 (one-way current, linear in energy and solid angle)
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
SDUM
= any character string (not containing '&') identifying the detector (max. 10 characters) Continuation card:
WHAT(1)
= maximum kinetic energy for scoring (GeV)
Default
: Beam particle total energy as set by the BEAM option (if no BEAM card is given, the energy corresponding to 200 GeV/c momentum will be used)
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
Default
(option USRBDX not given): no boundary crossing estimator detector IMPORTANT! ----------
Notes:
1) If the results have been written unformatted, and processed by the post-processing program $FLUPRO/flutil/usxsuw.f, two different files are produced, respectively with extension _sum.lis and _tab.lis. 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 cmumulative 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 angular bin, the data of the bin must then be multiplied by its width. 2) The formatted results of a USRBDX boundary crossing estimator, and the results written unformatted and converted to formatted by the post-processing program $FLUPRO/flutil/usxrea.f, 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). 3) Angular distributions must be intended as distributions in 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 theta=0 and the value indicated by the user with
WHAT(5)
in the second USRBDX card. 4) 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. 5) The maximum number of boundary crossing detectors that the user can define is 1100. 6) 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. 7) When scoring neutron fluence or current, and the requested energy bin structure overlaps with that of the low energy neutron groups, bin boundaries are forced to coincide with group boundaries and no bin can be smaller than the corresponding group. Actually, the program uses the requested energy limits and number of intervals to estimate the desired bin width. The number of intervals above the upper limit of the first low-energy neutron group is recalculated according to such width. 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 two Tables in 10.4.1.1}. 8) 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 > 20 MeV. The second table refers only to neutrons with energy < 20 MeV, and its interval structure is that of the neutron energy groups. 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. 9) 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, with the corresponding percent errors, in a file, and in another file 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).
Example:
*...+....1....+....2....+....3....+....4....+....5....+....6....+....7...+...8
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 &
* Calculate fluence spectrum from 0 to 5 GeV, in 200 linear energy intervals,
* of antineutrons passing from region 3 to region 4 (and not from 4 to 3).
* Write formatted results on unit 21. The area of the boundary is 400 cm2.
* A single angular interval is requested (from 0 to 2pi)

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