Mini-beta II

An improved mini-beta system has been found which uses readily available conventional quadrupoles, and its properties and limitations have been investigated. A four-fold symmetric arrangement matched to MI8 optics is assumed. The new quadrupole arrangement is flexible and adaptible to PETRA operation at beam energies up to 23 GeV; minor adjustments of the system can be made to reduce the chromaticity (or increase the luminosity) over a broad range. The relationship between the linear chromaticity xisub(z) and the luminosity gain relative to the present mini-beta set up is roughly linear, and it is not sensitive to the absolute k-values of the quadrupoles. The luminosity gain may be as high as a factor of two, but it depends critically on the maximum tolerable chromaticity and the assumed machine acceptance. (orig.)