High intensity proton linacs are envisaged as drivers for numerous applications (neutron spallation source for condensed matter study, neutrino factories and muons colliders, hybrid systems for transmutation or energy production, etc). Energy and phase stability of the beam is of primary importance to avoid any beam loss along the linac and, for the applications using rings as compressor or accumulator, the tolerances are even more severe to allow a loss free injection into the rings. There is general agreement on the superconducting technology for the high-energy part, which offers some advantages, like higher gradient capabilities or operational costs reduction, as compared to room-temperature structures. However, due to the narrow bandwidth of superconducting systems and the inclination of the cavity walls to deform easily, various effects, like microphonics or Lorentz forces, could enhance the cavity field fluctuations and then spoil the energy stability of the proton beam. It is shown in this report that, provided a careful design of the RF feedback system, cavity fields can be very well controlled, even for the pulsed mode operation, by far the most complex one. On obvious grounds of cost savings, the ?one klystron for multiple cavities? scheme can be considered but must be restricted to sufficiently high proton energy. |
