Figure 2
Fig. 2. Tomographic measurement of longitudinal phase-space density during asymmetric bunch pair merging in the CERN PS. By controlling the relative phase and voltage ratio of a dual-harmonic RF system, it is possible to merge unequal emittances. Here, one "bunch" is a phantom: an empty bucket was conserved during its transportation into the core of a much larger bunch where the (white) empty phase space was merged with the (dark) central region of the particle distribution. Tomography reveals a well preserved empty bucket entering the bunch as the acceptance of the populated bucket shrinks and particles bleed out around the separatrix (blue curve).