Measurements of betatron phase advance and beta function in the ISR

To check the optics of large storage rings measurements of the lattice functions are important. Some of these measurement methods have been tried out in the ISR. Information about the optics all round the ring is obtained by exciting a continuous betatron oscillation. The responses of different position monitors are compared with a network analyser. The square of the observed amplitude gives directly the relative value of the beta function. By measuring the relative phase of the responses the betatron phase advance between the locations of the monitors is obtained. Most of the error introduced by cable lengths is eliminated by observing both the upper and lower betatron side bands. The phase measurement does not depend on the monitor calibration. Its accuracy is therefore quite good as is confirmed by comparing the results with computations. Near the low-beta insertion, the beta functions are measured by observing the variation of the tune with changing quadrupole excitation