Thursday 2nd July 2015

Post date: Jul 2, 2015 7:04:15 AM

We continued the constant bucket area experiment in more detail. Starting at 4kV, we adjusted the final voltage between 1.5V and 4V so that the bucket area decreases, stays constant or increases during the acceleration cycle. The acceleration time was adjusted so that the final energy reached is always 100 MeV. The injected beam quality fluctuated during the measurement, complicating the comparison of S12 monitor data. To get around this we also recorded data from S7 which we hope will allow us to account for these fluctuations.

We also tried keeping the bucket area constant by instead increasing phi_s from 20 deg to 28 deg (and keeping the volts constant). Again we accelerated to 100 MeV. Finally we added adiabatic capture into the mix by increasing the voltage from 3kV to 4kV in the first 0.25 ms and then keeping the BA constant by again increasing phi_s from 20 to 28 degrees. This rf pattern required a 100 microsecond change in the delay time to get the beam injected. A strong rf dipole signal was seen on the real time spectrum analyser.

Next we will test whether the acceleration rate has any influence on the tune measured in the subsequent flattop. One idea is that resonances cause detuning with amplitude during the acceleration cycle. Changing the rate of acceleration should change the amplitude reached after, say, crossing a resonance which may in turn change the measured tune.