diff --git a/docs/source/dataanalysis/dataanalysis.rst b/docs/source/dataanalysis/dataanalysis.rst index 3df5651cc..22df2b073 100644 --- a/docs/source/dataanalysis/dataanalysis.rst +++ b/docs/source/dataanalysis/dataanalysis.rst @@ -58,8 +58,12 @@ Example to print the integrated orbit path length ``s`` at each beam monitor pos Reduced Beam Characteristics ---------------------------- -ImpactX calculates reduced beam characteristics like averaged positions, momenta, beam emittances and Courant-Snyder (Twiss) parameters during runtime. -These quantities are calculated before, after, and during each step of the simulation. +ImpactX calculates reduced beam characteristics based on the beam moments during runtime. +These include averaged positions, momenta, beam emittances and Courant-Snyder (Twiss) parameters. +For computing beam moments (as elsewhere), positions and momenta are given as deviations with respect to the reference particle (see :ref:`Coordinates and Units `). + +The reduced beam characteristics are stored with the output of the beam monitor element. +They are also calculated before, after, and during each step of the simulation. If ``diag.slice_step_diagnostics`` is enabled, they will also be calculated during each slice of each beamline element. The code writes out the values in an ASCII file prefixed ``reduced_beam_characteristics`` containing the follow columns: @@ -69,13 +73,13 @@ The code writes out the values in an ASCII file prefixed ``reduced_beam_characte * ``s``, ``ref_beta_gamma`` Reference particle coordinate ``s`` (unit: meter) and relativistic momentum normalized by the particle mass and the speed of light (unit: dimensionless) * ``x_mean/min/max``, ``y_mean/min/max``, ``t_mean/min/max`` - Average / minimum / maximum beam particle position in the dimensions of ``x``, ``y`` (transverse coordinates, unit: meter), and ``t`` (normalized time difference :math:`ct`, unit: meter) + Average / minimum / maximum particle displacement with respect to the reference particle in the dimensions of ``x``, ``y`` (transverse coordinates, unit: meter), and ``t`` (normalized time difference :math:`ct`, unit: meter) * ``sig_x``, ``sig_y``, ``sig_t`` RMS of the average beam particle positions (unit: meter) * ``px_mean/min/max``, ``py_mean/min/max``, ``pt_mean/min/max`` - Average / minimum / maximum beam momenta normalized by reference particle momentum (unit: dimensionless, radians for transverse momenta) + Average / minimum / maximum particle momentum deviation from the reference particle momentum, divided by the magnitude of the reference particle momentum (unit: dimensionless, radians for transverse momenta) * ``sig_px``, ``sig_py``, ``sig_pt`` - RMS of the average beam momenta (energy difference for ``pt``) (unit: dimensionless) + Standard deviation of the particle momentum deviations (energy difference for ``pt``) normalized by the magnitude of the reference particle momentum (unit: dimensionless) * ``emittance_x``, ``emittance_y``, ``emittance_t`` Normalized beam emittance (unit: meter) * ``alpha_x``, ``alpha_y``, ``alpha_t`` diff --git a/docs/source/theory/intro.rst b/docs/source/theory/intro.rst index 729b71cad..2709de077 100644 --- a/docs/source/theory/intro.rst +++ b/docs/source/theory/intro.rst @@ -38,6 +38,7 @@ One can set the number of slice steps through each lattice element for the appli Currently, space charge kicks are calculated in 3D. A 2D space-charge solver for purely transversal effects will be added in the future. +.. _theory-coordinates-and-units: Coordinates and Units ---------------------