Accelerator physics codes

A charged particle accelerator is a complex machine that takes elementary charged particles and accelerates them to very high energies. Accelerator physics is a field of physics encompassing all the aspects required to design and operate the equipment and to understand the resulting dynamics of the charged particles. There are software packages associated with each such domain. There are a large number of such codes. The 1990 edition of the Los Alamos Accelerator Code Group's compendium ^[1] provides summaries of more than 200 codes. Certain of those codes are still in use today although many are obsolete. Another index of existing and historical accelerator simulation codes is located at ^[2]

Single particle dynamics codes

For many applications it is sufficient to track a single particle through the relevant electric and magnetic fields. Some such codes include:

Space Charge Codes

The self interaction (e.g. space charge) of the charged particle beam can cause growth of the beam, such as with bunch lengthening, or intrabeam scattering. Additionally, space charge effects may cause instabilities and associated beam loss. Typically the Poisson equation is solved at intervals during the tracking using Particle-in-cell algorithms. Space charge effects lessen at higher energies so at higher energies the space charge effects may be modeled using simpler algorithms that are computationally much faster than the algorithms used at lower energies. Codes that handle low energy space charge effects, including computation of growth values and instability thresholds, include:

• ASTRA ^[21]
• Tranft ^[22]
• mbtrack ^[23]
• ORBIT,^[24] PyORBIT^[25]
• Synergia ^[26]
• IMPACT ^[27]
• OPAL ^[28]
• GPT ^[29]
• VSim ^[30]
• TraceWin ^[31]
• WARP ^[32]
• CST Studio Suite ^[33]

At higher energies, space charge effects include Touschek scattering and coherent synchrotron radiation (CSR). Codes that handle higher energy space charge include:

• Bmad
• ELEGANT
• MaryLie
• SAD

Impedance computation codes

An important class of collective effects may be summarized in terms of the beams response to an "impedance". An important job is thus the computation of this impedance for the machine. Codes for this computation include

• ABCI ^[34]
• ACE3P ^[35]
• CST Studio Suite ^[36]
• GdfidL^[37]
• TBCI ^[38]
• VSim ^[39]

Magnet and other hardware-modeling codes

To control the charged particle beam, appropriate electric and magnetic fields must be created. There are software packages to help in the design and understanding of the magnets, RF cavities, and other elements that create these fields. Codes include

• ACE3P ^[35]
• COMSOL Multiphysics ^[40]
• CST Studio Suite ^[41]
• OPERA ^[42]
• VSim ^[43]

Lattice file format and data interchange issues

Given the variety of modelling tasks, there is not one common data format that has developed. For describing the layout of an accelerator and the corresponding elements, one uses a so-called "lattice file". There have been numerous attempts at unifying the lattice file formats used in different codes. One unification attempt is the Accelerator Markup Language, and the Universal Accelerator Parser.^[44] Another attempt at a unified approach to accelerator codes is the UAL or Universal Accelerator Library.^[45]

The file formats used in MAD may be the most common, with translation routines available to convert to an input form needed for a different code. Associated with the Elegant code is a data format called SDDS, with an associated suite of tools. If one uses a Matlab-based code, such as Accelerator Toolbox, one has available all the tools within Matlab.

Codes in applications of particle accelerators

There are many applications of particle accelerators. For example, two important applications are elementary particle physics and synchrotron radiation production. When performing a modeling task for any accelerator operation, the results of charged particle beam dynamics simulations must feed into the associated application. Thus, for a full simulation, one must include the codes in associated applications. For particle physics, the simulation may be continued in a detector with a code such as Geant4.

For a synchrotron radiation facility, for example, the electron beam produces an x-ray beam that then travels down a beamline before reaching the experiment. Thus, the electron beam modeling software must interface with the x-ray optics modelling software such as SRW,^[46] Shadow,^[47] McXTrace,^[48] or Spectra.^[49] Bmad^[8] can model both X-rays and charged particle beams. The x-rays are used in an experiment which may be modeled and analyzed with various software, such as the DAWN science platform.^[50] OCELOT ^[51] also includes both synchrotron radiation calculation and x-ray propagation models.

See also

• CARE-HHH Codes Repository
• List of codes from UCLA Particle Beam Physics Laboratory

References