Abstract :
A device has been designed and built to obtain the four dimensional emittance of a particle beam. Two rotating discs with hole patterns scan the beam using the Nipkov principle. The emittance is determined from 10.000 beam samples, each of which is taken in 1 ms. Dependent on the chosen hole pattern a complete cycle of 10.000 samples takes 20-40 s. A small computer is used to control the experiment and to store the measurement data. Beam samples of 1 nA and up can be measured with 1% accuracy. The emittance of a particle beam can be described as a function in the four dimensional phase space: E(x,x´,y,y´), with E = dI/dV, where x and y are mutually perpendiculat and transverse to the beam direction z, I is the beam current, dV a volume element in phase space, and x´ = dx/dz, y´ = dy/dz. A much used representation of the emittance is given by E(x,x´) = ¿ Edydy´, E(y,y´) = ¿ Edxdx´. phase space phase space
