The original deterministic Attila solver was unique in its use of arbitrary tetrahedral elements with linear discontinuous finite element spatial differencing. By solving the linear Boltzmann transport equation (LBTE) on tetrahedral elements, Attila supported CAD integration and could leverage established computer aided engineering (CAE) practices, which commonly use tetrahedral elements. Attila was commercialized with the goal of introducing a CAD integrated, graphical user interface (GUI) driven radiation transport software system.

Many Attila users also ran Monte Carlo solvers, such as MCNP, to obtain an independent solution. Attila would be used for design iterations and identifying local “hot spots,” and MCNP would then be used for verification. By providing two independent solutions using deterministic and stochastic methods, Attila and MCNP became complementary to each other in radiological engineering design processes.

In 2011, Los Alamos National Laboratory began work on implementing an unstructured mesh (UM) capability in MCNP. Soon after, Transpire, Inc. started development work to support MCNP in the Attila GUI. With the advent of MCNP’s UM capability, both Attila and MCNP could use the same tetrahedral mesh, enabling a rapid, CAD integrated approach to setting up and running calculations using two independent solution methods.

Attila4MC was originally introduced in 2014, and a few years later, the CADIS and FW-CADIS variance reduction methods were added to Attila4MC. These methods further strengthened the complimentary benefits of Attila and MCNP by leveraging the Attila deterministic solver to accelerate MCNP convergence.

The acquisition by Silver Fir Software represents a new chapter in the Attila Product Line. The mission of Silver Fir Software is to improve the productivity of users doing radiation transport simulations, and to this end, our goal is to deliver best-in-class software and support.