Landau cavities stabilizing and stretching 3 GeV bunches

Landau cavities stabilizing and stretching 3 GeV bunches

After being able to ramp up the beam current to around 130 mA, we can start to see the stabilizing effect of our three Landau cavities operating at the third harmonic (300 MHz). For currents above ~125 mA, the shunt impedance of these cavities becomes sufficient to approach flat-potential conditions when the cavities are properly tuned in. In this regime we can see the longitudinal spectrum calm down as the additional Landau damping stabilizes the beam. We can also see the bunch length increase while the synchrotron frequency drops. We have seen integrated lifetime in excess of 3 Ah under such conditions. This is about a factor three higher than we usually saw when the Landau cavities were tuned out.