[fluka-discuss]: USRBDX and Lattice Errors

From: Bartkoski,Dirk Alan <DABartkoski_at_mdanderson.org>
Date: Tue, 2 Jun 2020 20:02:25 +0000

I have a model that utilizes Iodine 125 seeds in a Gamma-Knife type geometry to produce a localized dose. I have modeled this in FLUKA with a row of collimating holes which has been replicated using LATTICES. I simulate the multiple simultaneous seeds by simulating each individual seed location and combining the results.

I have two problems:

1) I am trying to score the photon current passing into the interior of my irradiator from the collimating holes. Implementing the USRBDX card to do one-way Current scoring causes the simulation to fail with

Program received signal SIGFPE: Floating-point exception - erroneous arithmetic operation.

I have been unable to identify the error.
If I run the simulation with only USRBIN scoring it runs just fine.

2) When I use a seed location in one of the lattice regions, I get lots of

Geofar: Particle in region 29 (cell # 5) in position -3.055184254E+00 6.866332986E+00 -3.308096656E+00
  is now causing trouble, requesting a step of 1.675802152E+03 cm
  to direction -2.521430795E-02 -7.443458025E-01 6.673181887E-01, error count: 0

type errors. From what I understand this is lattice related and probably numerical precision related.

I am at a loss as to how to fix these issues. I have attached my .flair (made with Flair3) and my input file.

Any suggestions would be greatly appreciated.
Dirk A. Bartkoski, Ph.D.
Research Scientist | Division of Radiation Oncology
T. Boone Pickens Tower (FCT8.5007)
1515 Holcombe Blvd.
Unit 1420
Houston, TX 77030

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Received on Tue Jun 02 2020 - 23:53:28 CEST

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