Puffin (Parallel Unaveraged Fel INtegrator) simulates a Free Electron Laser (FEL). Puffin is a massively parallel numerical solver for an unaveraged, 3D FEL system of equations, and is written mostly in Fortran 90, using MPI and OpenMP. The initial publication describing the first version of the code is:- LT Campbell and BWJ McNeil, Physics of Plasmas 19, 093119 (2012) The code has undergone many improvements and extended its functionality since then. It no longer uses an external linear solver package, and the only external packages now required are FFTW (version 3.3 onwards), and parallel HDF5 libraries. Please note Puffin is currently under active development. This is the first alpha release. Recent changes over the closed version: Can now input with the Puffin HDF5 output format More metadata in the output files Can now resume from previous runs using HDF5 Puffin dumps Twiss parameters can be used with the simple beam input Communication time reduced in reorganisation stage of the parallel field algorithm Using doxygen for dev documentation The example auto-plotting python scripts for Visit have been refactored and can be called separately Added python script (powPrep.py) to collect the power data together Better point transforms for quads, now including energy dependence Fixed bug of extra half-period diffraction per undulator module HDF5 output is now the default data output format

Funded by EPSRC grant EP/M011607/1, STFC Agreement Number 4163192 Release #3, and EPSRC grant EP/K000586/1.