Pulsed electrostatic quadrupole focusing for the CERN muon storage ring

In order to improve the precision in the measurement of the g-factor anomaly a=(g-2)/2, it is desirable to have the polarized muons circulating in a uniform magnetic field (B.v=0). Vertical focusing of the muons can be done with an electrostatic quadrupole field. Although the required potentials on the electrodes are reasonable ( approximately 40 kV), the combined action of magnetic and electric field considerably enhances the probability of breakdown. This is due to trapped electrons which circulate around the electrodes and ionize the molecules of the rest gas. However, with reasonable vacuum (<10 /sup -6/ torr) the build-up of charge is slow. Therefore a pulsed electrostatic quadrupole field is applied, the field being on during the storage time of the muons, i.e. 1 ms. In this way the system is operational. (6 refs).