Alternatives

Several state-of-the-art programs to model charged particles dynamics exist. Most of them are listed in Wikipedia articles on Accelerator physics codes and Particle-in-cell method.

Broadly speaking, the codes can be categorized in the following way: beam dynamics with PIC for space charge, plasma simulation, high-energy beams, other applications.

Beam dynamics with PIC for space charge

• Warp is the most interesting open-source code in this category. It is not tailored to low-energy beams, but provides space charge support. It has most of the desired functionality and certain very advanced features such as support for curved meshes.

• SNOP - implements PIC

Several commercial packages are also available:

• CST Studio
• Opera
• Simion - for ions only.
• EGUN-IGUN

Plasma physics
Two of the most interesting open source codes are

• Smilei -- strong team, development progresses quickly.
• PIConGPU -- the most successful attempt to implement multi-GPU particle-in-cell.

Besides, there are a lot of other codes:

• P-I-C-S-A-R
• OSIRIS, MAGTAIL, PARSEC, QuickPIC, UPIC, and OSHUN" https://plasmasim.physics.ucla.edu/codes
• Educational codes http://picksc.idre.ucla.edu/software/skeleton-code/software-skeleton-code-openmpmpi/

High-energy physics
Most codes in this category do not implement PIC for space charge and use simpler methods to take particle-particle interaction into account.

• Mad seems to be de facto standard here.