Correlation technique for measurements of beam emittance and energy spread

When a beam of charged particles passes through a lattice with bending magnets, then mixing of the relative longitudinal positions of particles can take place. This mixing is caused by the energy spread of beam particles and by the spread of the particle betatron coordinates and angles, and has the effect of changing the time structure of the fields radiated by the beam at different points of its trajectory. It is shown in the paper that by measuring the correlation function of the radiation fields at two points of the beam trajectory, one can determine the beam emittance and the beam energy spread. A detailed analysis of this diagnostic technique with a few illustrative examples is provided. A method of intensity correlation has been proposed for a case when two radiation points are separated by a long distance and intersecting of two radiation fields in the same detector is difficult.