THE BEAM BRIGHTNESS AND THE PRINCIPLE FOR MEASURING EMITTANCE USING THE PEPPER POT METHOD

For a electron beam in a uniform (Waterbag) or Gaussian distribution in the transverse 4-phase space, the measurement principle of the beam emittance with the pepper pot method is studied. The results show that, for the Waterbag beam, the obtained emittance is the edge emittance and the spot sizes for beamlets are different form each other, and that, for the gaussian beam, the RMS emittance, but the spot sizes are equal, not depending on initial positions of the beamlets.