Flux, intensity, brightness and brilliance

In practice, a (electron) is usually a good deal less than a (radiation) (=y 1) so that a (total) is determined almost completely by y-1. The machine emittance is then, in units of metre radians for example, 

Other quantities of interest are the so-called beta-functions in the horizontal and vertical where 

The principles of SR and the practicalities of producing it have now been covered. The radiation emanates with defined spectral characteristics from a finite source size and with a finite angular divergence. Macromolecular crystallography exploits some or all of these properties depending on the size of the crystal sample, the unit cell and the crystal sample mosaicity. The terms flux, intensity, brightness and brilliance are used to describe the various aspects of SR and its use in experiments. 

The spectral flux, 0, is the number of photons, emitted per unit time into a relative bandwidth dktX into an angle element in the plane of the electron orbit and integrated in the vertical plane. The units of flux P are usually 

Note that the universal distribution of Schwinger described in section 4.3 is per mA per GeV whereas the flux here is a practical value for a given machine. 

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