SixTrack

SixTrack
Name	SixTrack
Developer	CERN, collaboration
Released	1996
Programming language	Fortran, C, Python (wrappers)
Operating system	Linux, macOS, Windows (via WSL)
License	GPL-compatible (collaboration-specific)

SixTrack SixTrack is a high-performance, particle-tracking software package used for long-term dynamics studies in charged-particle accelerators. Developed at CERN with contributions from national laboratories and universities such as FNAL, DESY, STFC Rutherford Appleton Laboratory, GSI Helmholtz Centre for Heavy Ion Research, and LBNL, the code specializes in symplectic, single-particle tracking for circular machines and transport lines. It is widely integrated into workflows with simulation tools like MAD-X, FLUKA, Geant4, PyORBIT, and ROOT for design, commissioning, and high-intensity operation studies.

Overview

SixTrack models the longitudinal and transverse motion of relativistic particles through magnetic and RF elements of storage rings and transfer lines. The project originated to support upgrades and operation of the Large Hadron Collider and related injector chain components such as PS Booster and SPS (accelerator). Typical studies include dynamic aperture, tune footprint, resonance analysis, slow extraction, and loss maps for collimation systems. The code is designed for large-scale, multi-turn simulations, enabling interaction with complementary software such as MAD, MAD-X, SixDesk, and visualization via ROOT and Matplotlib toolchains.

Physics and Computational Methods

SixTrack employs symplectic integration using map-based representation of accelerator elements like dipoles, quadrupoles, sextupoles, octupoles, RF cavities, and thin-lens multipoles. The underlying algorithms implement canonical transformations that preserve phase-space volume, reflecting principles from Hamiltonian mechanics and Lie algebraic methods used across accelerator theory in works associated with Ernest Courant, Herman K. Hahn, and modern authors at CERN. Tracking includes chromatic effects, synchrotron motion, and momentum compaction modeled for machines such as LHC, RHIC, and SPS (accelerator). For collective effects studies, SixTrack interfaces with codes handling space charge, wake-fields, and impedance models originating from studies by groups at BNL and FNAL. Numerically, the code supports fixed-step, high-order integrators, particle sampling strategies, and diagnostics for tune, action-angle variables, and frequency-map analysis developed in collaboration with research groups at EPFL.

Code Development and Implementation

SixTrack's core is written in Fortran for numerical kernels, augmented by C and Python wrappers for I/O, workflow orchestration, and pre/post-processing. Development has been coordinated through collaborations involving CERN IT, the CERN Accelerator Beam Physics group, and partner institutions like TU Darmstadt. Version control, testing, and continuous integration practices parallel those in large scientific software projects at CERN Openlab. Portability targets high-performance clusters and heterogeneous architectures; recent efforts include parallelization with MPI, threading with OpenMP, and GPU offloading prototypes tested at CERN and HL-LHC related projects. Input formats are compatible with established accelerator lattice descriptions such as those produced by MAD-X and SAD, and outputs integrate with visualization and analysis frameworks like ROOT and Python scientific libraries maintained by communities at NumFOCUS projects.

Applications in Accelerator Design and Operations

SixTrack has been instrumental in design and operational studies for major facilities including Large Hadron Collider, HL-LHC, SPS (accelerator), ISOLDE, LHCb, and upgrade proposals at CERN. It is routinely used to generate loss maps for collimation design, tune scans for resonance avoidance, and dynamic aperture computations that inform magnet and optics specifications used by engineering teams at CERN and partner labs. The tool supports machine protection and commissioning tasks, interfacing with beam instrumentation developments at CERN and diagnostic campaigns at GSI Helmholtz Centre for Heavy Ion Research and DESY. Collaborative projects have expanded SixTrack usage into injector chains like Linac4 and transfer lines feeding experiments such as ALICE and ATLAS.

Validation, Benchmarks, and Performance

Validation campaigns compare SixTrack results against experimental data from beam studies at LHC and measurement campaigns at facilities including CERN SPS, BNL RHIC, and DESY PETRA. Benchmarks include dynamic aperture convergence tests, tune diffusion estimates, and loss-map reproducibility against full-physics simulations combining Geant4 and FLUKA for shower and activation predictions used by CERN radiation protection groups. Performance profiling and scaling studies have been carried out on HPC platforms at CERN IT and national supercomputing centers, demonstrating efficient MPI scaling for large-particle ensembles and multi-turn studies. Optimizations for vectorization and memory locality mirror practices from high-performance scientific computing seen in projects at Argonne National Laboratory and Oak Ridge National Laboratory.

User Community and Governance

The SixTrack user base comprises accelerator physicists, beam dynamics experts, and engineers from institutes like CERN, FNAL, DESY, BNL, GSI Helmholtz Centre for Heavy Ion Research, and universities across Europe, North America, and Asia. Governance is maintained via collaboration boards and working groups coordinated at CERN Accelerator Beam Physics group meetings, workshops at IPAC, and training schools run by CERN and partner institutions. Contributions follow community coding practices with review by domain experts from laboratories including STFC Rutherford Appleton Laboratory and LBNL, and integration testing for major releases is organized through collaborative test suites reflecting operational scenarios for LHC and future upgrades like HL-LHC.

Category:Accelerator physics software