Dear Andre For a continuum wavelength band source this unit is needed. A monochromator of a given type then extracts it's rocking curves worth of bandpass. Or in Laue diffraction a wide band is selected with eg a mirror cut off at short wavelengths and a filter or transmission mirror at long wavelengths. The sample crystal picks out it's rocking curves worth of bandpass. The source type can be xray or neutron. The synchrotron undulator is a special case where periodic magnets of low field create a gathering of wavelengths emitted from the SR source ie by constructive inteference into a narrow bandpass which can be say 0.02%. This is technical I realise but hope that sets you on the right track to consult a relevant textbook. Best wishes, John
Prof John R Helliwell DSc On 9 Feb 2011, at 12:13, Andre Luis Berteli Ambrosio <andre.ambro...@lnbio.org.br> wrote: > Dear ccp4bb, > > > > I sometimes find the flux of x-ray sources reported in units of > “photons/s/0.1% bandwidth” instead of simply “photons/s”. > > Where does the “1/0.1% bandwidth” unit come from? I have also seen other > percentages like 0.01% bw or 0.02% bw… > > Is it simply defining some degree of acceptance in energy (for example, the > flux between 8 KeV +/- 8 eV for a given stored current)? Does it somehow have > to do with energy resolution? > > Thank you in advance for your answers, > > > > -Andre Ambrosio > >
