Accelerator lattice

The files in this directory handle the accelerator lattice. These are fields of various types and configurations. The lattice is laid out along the z-axis.

The AcceleratorLattice has the instances of the accelerator element types and handles the input of the data.

The LatticeElementFinder manages the application of the fields to the particles. It maintains index lookup tables that allow rapidly determining which elements the particles are in.

The classes for each element type are in the subdirectory LatticeElements.

Host and device classes

The LatticeElementFinder and each of the element types have two classes, one that lives on the host and one that can be trivially copied to the device. This dual structure is needed because of the complex data structures describing both the accelerator elements and the index lookup tables. The host level classes manage the data structures, reading in and setting up the data. The host classes copy the data to the device and maintain the pointers to that data on the device. The device level classes grab pointers to the appropriate data (on the device) needed when fetching the data for the particles.

External fields

The lattice fields are applied to the particles from the GetExternalEBField class. If a lattice is defined, the GetExternalEBField class gets the lattice element finder device level instance associated with the grid being operated on. The fields are applied from that instance, which calls the “get_field” method for each lattice element type that is defined for each particle.

Adding new element types

A number of places need to be touched when adding a new element types. The best method is to look for every place where the “quad” element is referenced and duplicate the code for the new element type. Changes will only be needed within the AcceleratorLattice directory.