Chromaticity in LEIR performance

To study the low energy loss of LEIR at the beginning of the magnetic ramp in NOMINAL cycles, we measured the machine tune for different beam momentum offsets on February 12th, 2013. Later on, we computed the resulting chromaticity for both, the horizontal and the vertical plane from these measurement results. We found that the measured tunes have values close to the design tunes for both planes. However, we discovered that the tunes for both planes show a dynamic nature with respect to time during the magnetic ramp of the NOMINAL cycle. In the tune diagram, the tunes lie close to a forth order resonance. We have also discovered that the chromaticity for the vertical plane is positive during the magnetic ramp. This could provoke instabilities and it could be responsible for the observed beam loss of LEIR for NOMINAL cycles at the beginning of the magnetic ramp.