电子束亮度及多孔板法测量发射度的原理

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

本文探讨了利用多孔板法测量四维横向相空间中均匀分布以及高斯分布的电子束发射度的测量原理。结果表明,对于四维均匀分布的电子束,该法测量的是电子束的边发射度,并且光斑尺寸随着小孔位置不同而变化;对于高斯分布的电子束,该法测量的是电子束的均方根发射度,其光斑尺寸与小孔位置无关。

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.