At an absorption edge, the program uses the tabulated mass attenuation coefficient (MAC) for the element that actually exhibits the edge. For all other elements in the mixture—whose attenuation coefficients remain continuous at that energy—the MAC at the edge is estimated using a log–log (power-law) interpolation. The interpolation is performed using two nearby XCOM tabulated points for energies between 1 and 1.5 keV, and three nearby points at higher energies. This approach ensures a smooth and physically consistent MAC estimate for elements that do not exhibit an absorption edge at the selected energy.
Since some parameters, such as HVL and TVL, require density information, the user must provide a non-zero density value (in g/cm³). If the density is omitted or given as zero, the program will generate an error and stop execution. If a non-zero value is supplied but does not correspond to the true density of the material, GRASP-X will compute the relevant parameters using the provided value, and the user should adjust it if exact results are required.
The results are displayed both as a graph and a downloadable table.
In addition to the gamma shielding parameters mentioned above, the program also calculates the fast neutron removal cross section of the target.
Please cite the following article(s) if you have used GRASP-X in your research:
• Calculation of the fast neutron removal cross section was added. May 3, 2026.
• The atomic and electronic cross-section formulae were revised. April 6, 2026.
• Revised MAC interpolation approach: exponential fitting replaced by power-law (log–log)
interpolation to better reflect XCOM data trends. February 6, 2026.