Motivation and Goals

Ef general design goals are following:

1. Focus on simulation of low-energy charged particle beam devices: ion sources, electron guns, etc. Current goal is simulation of electron beam ion sources (EBIS).
2. Detailed control over simulation algorithm. This is essential if nonstandard numerical scheme is required.
3. Support for parallel execution (both CPU and GPU) to handle large number of particles and long simulation times.
4. Integration with CAD systems to simplify device geometry specification. Implementation of specialized tools to easily extract, display and analyze properties of practical interest from output data.
5. Source code is free and open, available for modifications and redistribution.

The goals have been influenced by the following considerations.

Ef is developed with a particular application in mind: simulation and optimization of certain type of ion source - electron beam ion source, EBIS. Such sources are commonly used to produce beams of highly charged ions for applications in particle physics, medicine and surface modification. Their principle of operation employs an electrostatic ion trap to hold the ions while ionizing them to desired charge state with an electron beam.

Like many ion sources and electron guns, EBIS primarily operates in non-relativistic energy regime. In such mode, particle-particle interaction (space charge) plays prominent role and has to be taken into account alongside with external fields. Besides, non-relativistic kinematics can be used to simplify calculations without too much loss in accuracy, whereas relativistic regime can be provided as an option. Due to large number of particles and long time duration to simulate the problem is computationally demanding and requires parallelization to accomplish the simulation in reasonable amount of time. In EBIS different spatial and time scales are involved: slow ions and fast electrons have uncomparable time evolution scales, and transversal size of the beam (less than 1 mm radius) is much much less longitudinal trap length (50-100 cm). This requires fine control over details of simulation algorithm to incorporate certain modifications in the numerical scheme if necessary.

Device geometry plays a major role in low-energy beam devices. Therefore, integration with CAD systems is highly desirable to simplify geometry specification. A useful feature would be to provide an opportunity to automate the search for the optimal geometry of the device and it’s regimes. For practical means, such parameters as intensity, emittance, current fluctuations, particle energy spectrum, phase profiles and particle trajectories are of most interest. An ideal program should allow to display them and provide tools to analyze them easily.

The source code of the program is free and open, available for modifications and redistribution. Apart from various general considerations and immediate practical benefits, this is also essential to comply with a principle of reproducible research.

While the program currently focuses on ion sources of certain type, it should be useful for simulation of other low-energy charged particle beam and (possibly) plasma devices.