Effect of RF phase modulation near a parametric resonance on the longitudinal emittance

Aiming at increasing the apparent bunch length and hence the beam lifetime in electron storage rings, RF phase modulation near one parametric resonance has been experimentally investigated. Since the eventual benefit of this technique depends greatly on the ring parameters, we studied the effect of such a modulation for different RF parameters on the longitudinal emittance. Theoretical predictions and results of simulations are compared and discussed. It is shown that synchrotron radiation tends to spoil the parametric resonance. In particular, a criterion for islands survival has been found