|Message: Re: Unexpected results for fluence and TID using Spenvis/GRAS||Not Logged In (login)|
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I have tested a normalization approach that seems to help with the various GRANT-based MULASSIS and GRAS routines.
In many space applications with omnidirectional or plane-parallel sources, the generated fluence is uniform throughout the problem geometry in the absence of particle interactions -- that is, with virtual geantinos or with the VOID entry used in the MCNP program.
For SPENVIS, the equivalent approach replaces the shielding materials with Vacuum and then analyzes (tallies) the resulting fluences throughout the geometry, whether using MULASSIS, GRAS/MULASSIS, or GRAS/GDML. One often finds that a generating source that was expected to produce a unit fluence in fact produces two or four times that result. One can then either renormalize the doses by the observed factor or adjust the input source fluence to produce an observed result of unity.
This approach has worked with both MULASSIS and GRAS, using parallel beams or omnidirectional sources, with both slab and shell shielding.
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