# 7. Track File Format¶

The current revision of the particle track file format is 3.0.

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Attributes
• filetype (char[]) – String indicating the type of file.

• version (int[2]) – Major and minor version of the track file format.

Datasets
• track_<b>_<g>_<p> (Compound type) – Particle track information for source particle in batch b, generation g, and particle number p. particle. The compound type has fields r, u, E, time, wgt, cell_id, cell_instance, and material_id, which represent the position (each coordinate in [cm]), direction, energy in [eV], time in [s], weight, cell ID, cell instance, and material ID, respectively. When the particle is present in a cell with no material assigned, the material ID is given as -1. Note that this array contains information for one or more primary/secondary particles originating. The starting index for each primary/secondary particle is given by the offsets attribute.

Attributes
• n_particles (int) – Number of primary/secondary particles for the source history.

• offsets (int[]) Offset (starting index) into the array for each primary/secondary particle. The last offset should match the total size of the array.

• particles (int[]) – Particle type for each primary/secondary particle (0=neutron, 1=photon, 2=electron, 3=positron).