Simple example (2.1.24)

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Jaakko Leppänen
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Simple example (2.1.24)

Post by Jaakko Leppänen » Fri Jun 26, 2015 12:33 pm

The completed photon interaction physics were included in update 2.1.24, and Toni will post a description of the physics models later on. Here are a few simple examples on how photon transport simulations can be run...

The source name in the "src" card must be followed by "g", to indicate that the source is for photons. For example, a point source of 1.0 MeV photons:

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src 1 g sp 0.0 0.0 0.0 se 1.0
The calculation also requires photon ACE libraries and a corresponding directory file. This data is not provided with the Serpent 1 installation package, but any photon library used with MCNP should do. The syntax is the same as for neutron data libraries:

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set acelib "dlc200.xsdata"
To create the Serpent directory file from an MCNP xsdir file, use the latest version of the xsdirconvert.pl script. The calculation also requires a few additional data files for the physics model, which are available for download at:

http://montecarlo.vtt.fi/download/photon_data.zip

The data path is defined in the input with "set pdatadir", for example:

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set pdatadir "/xs/photon_data"
Note that the path is the complete path to the directory where the data files in the zip file are located.

Since photon interaction data is elemental, also the material definitions look a bit different. Here's an example for air:

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mat air -1.20500E-03
 6000.02p  -1.24000E-04
 7000.02p  -7.55268E-01
 8000.02p  -2.31781E-01
18000.02p  -1.28270E-02
For a complete simple example, see one of the demo cases presented at the recent fusion neutronics workshop at Cambridge:

http://montecarlo.vtt.fi/mtg/Fusion_201 ... ma/simple2
- Jaakko

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Re: Simple example (2.1.24)

Post by Jaakko Leppänen » Fri Jun 26, 2015 12:43 pm

Serpent can also use isotopic material compositions written for neutron transport problems in photon calculations. The densities of individual isotopes are automatically summed for each element, and the corresponding cross section libraries read from the directory file. A few notes:

1) The calculation requires directory files for both neutron and photon calculation, for example:

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set acelib "sss_jeff31u.xsdata" "dlc200.xsdata"
The neutron data is not used, but it is required for forming the elemental compositions.

2) In this mode it is not possible to explicitly define which photon libraries are used, since the library ID's are not provided in the input. Serpent reads photon data from the first matching elemental entry in the directory file.

An example of a neutron input converted to photon input is found at:

http://virtual.vtt.fi/virtual/montecarl ... ma/simple3
- Jaakko

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