Kassiopeia: a modern, extensible C++ particle tracking package

Abstract

The KASSIOPEIA particle tracking framework is an object-oriented software package using modern C+ + techniques, written originally to meet the needs of the KATRIN collaboration. KASSIOPEIA features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease-of-use for novice programmers. To solve KASSIOPEIAʼs target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur in flight such as bulk scattering and decay, and stochastic surface processes occurring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle's state evolves. Thanks to the very general approach taken by KASSIOPEIA it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopeia.

Locust: C++ software for simulation of RF detection

“…Next, just as in section 2, the LMCSignal array is processed through an applicable receiver chain and is digitized. To illustrate, figure 4 shows a flow diagram in which the functionality of the block corresponding to 'LMCGenerator 1' is expanded to interact with the external Kassiopeia software package [3]. The next section will describe this interface in more detail.…”

“…One example of software that can be used to define external signals is the Kassiopeia simulation software package [3], compiled as a submodule within Locust. First developed for the KATRIN experiment [19], Kassiopeia is a software tool designed to compute electromagnetic fields in complex geometries, simultaneous with timedependent solutions of particle states in position and momentum (x,p).…”

“…The calculated electron trajectory x(t) is derived using the adiabatic approximation, which relies on conservation of the magnetic moment of the electron(e.g. [3]). The approximation is valid when variations in the electric and magnetic fields are minimal over each cyclotron orbit.…”

“…An eighth order Runge-Kutta integrator is used to solve the ordinary differential equation describing the trajectory. Power P lost by the electron to synchrotron radiation is then computed in Kassiopeia as [3] m where F=dp/dt is the radiation reaction force, || F andF are the components of F parallel and perpendicular to the magnetic field,…”

“…Within the context of the Locust framework, the characteristics of the signal will be observed as it traverses the components of a simulated receiver, is digitized, and is then processed after Locust with the Katydid [2] analysis software. Section 3 will refer to the second running mode in which Locust is integrated with another numerical model, an electron cyclotron orbit simulation performed with the Kassiopeia [3] software package.…”