spill_generator_number_of_spills = 1
beam = {
  "particle_generator":"counter",
  "random_seed":0,
  "definitions":[
  {
    "random_seed_algorithm":"incrementing_random",
    "n_particles_per_spill":1,
    "reference":simulation_reference_particle,
    "transverse":{"transverse_mode":"pencil"},
    "longitudinal":{"longitudinal_mode":"pencil", "momentum_variable":"energy"},
    "coupling":{"coupling_mode":"none"}
  },{
    "random_seed_algorithm":"incrementing_random",
    "n_particles_per_spill":1000,
    "reference":simulation_reference_particle,
    "transverse":{"transverse_mode":"penn", "normalised_angular_momentum":0., "emittance_4d":15., "beta_4d":800., "alpha_4d":0., "bz":0.},
    "longitudinal":{"longitudinal_mode":"gaussian", "momentum_variable":"p", "sigma_p":100., "sigma_t":1.},
    "coupling":{"coupling_mode":"none"}
  },
  ]
}