NEA-1884 SACALC-ELLIPSOID.

1. NAME OR DESIGNATION OF PROGRAM:  SACALC-ELLIPSOID

3. DESCRIPTION OF PROGRAM OR FUNCTION

SACALC-ELLIPSOID is a program for a Microsoft Windows personal computer that calculates the solid angle subtended by a ellipsoid solid or surface (so that will include spherical and spheroidal solid and surfaces) to a right cylinder detector, or a cuboid detector at any position and orientation to the detector. The program also calculates the number of hits on the detector sides and the average path length through the detector volume (assuming no scattering or absorption). The current performance of personal computers makes it realistic to model the order of 109 simulations of radiation emission and achieve accuracies of solid angle estimates typically better than 0.03 %.

The program also calculates the number of hits on the detector walls and the average path length through the detector volume (assuming no scattering or absorption).

The input data can be done on screen, or for batch processing, multiple cases can be entered as a text file.

4. METHODS

The program uses a Monte Carlo method to calculate the average solid angle for source-detector geometries that are difficult to analyse by analytical methods. The values of solid angle are calculated to accuracies of typically better than 0.03%.

5. RESTRICTIONS ON THE COMPLEXITY OF THE PROBLEM

The sources are assumed to be uniformly distributed. To avoid rounding errors, differences less than 1e-12 are assumed to be zero.

6. TYPICAL RUNNING TIME

It depends on the number of random events selected by the user. On an Intel Core i7 Q740 1.73 GHz with 4 Gbytes RAM under OS Windows 7, the program took just under 12 minutes to simulate 1E9 random events for a rotated ellipsoidal surface source, giving an error of less than 0.03% where the average probability of a hit was 0.1. For faster calculations, multiple instances of the program can be run on computers with multi-core processors.

7. UNUSUAL FEATURES

The program models non-coaxial and non-parallel geometries, and combinations of source and detector shapes.

10. REFERENCES

- R. Whitcher: 'A Monte Carlo method to calculate the average solid angle subtended by a detector to an ellipsoidal surface or solid source at any position and orientation'.  (Radiation Protection Dosimetry 2012 149 (4): 444-453).
- A Monte Carlo Method to Calculate the Average Solid Angle Subtended by a Right Cylinder to a Source that is Circular or Rectangular, Plane or Thick, at any Position and Orientation (Radiation Protection Dosimetry 2006 118(4):459-474).

- Ralph Whitcher: "SACALC_Ellipsoid v1.0" User's guide (RW 2/12)

11. HARDWARE REQUIREMENTS

The program runs on any computer operating Microsoft Windows OS XP, Vista/7/8.

13. SOFTWARE REQUIREMENTS:  The program was compiled with Turbo Delphi 2006.

15. NAME AND ESTABLISHMENT OF AUTHORS:  
Ralph WHITCHER
Crawley
United Kingdom

SACALC_ellipsoid1a.exe           Executable to run the SACALC_ellipsoid code
SACALC_ellipsoid_readfile_example.txt  Example of a text file for batch
processing
SACALC_ellipsoid.pdf             Documentation in PDF Format