{Distance from sample}?
{Energy on entering beamline component}?
{Energy on leaving beamline component}?
{Energy change caused by beamline component }?
{Wavelength on entering beamline component}?
{Wavelength spread FWHM on entering component}?
{Divergence of beam entering this component}?
{Wavelength on leaving beamline component}?
{Polarization vector on entering beamline component}?
{Polarization vector on leaving beamline component}?
{Wavelength spread FWHM of beam leaving this component}?
{Divergence FWHM of beam leaving this component}?
{flux incident on beam plane area}?
{Distribution of beam with respect to relevant variable e.g. wavelength. This is mainly useful for simulations which need to store plottable information at each beamline component. }?