Figure 2: Space–charge interactions between ion bunches.

Ion beam density profiles imaged 24 cm (7.9 μs) from the source region, for nine closely spaced bunches each of 100 μm diameter. Upper panel: experimentally measured profiles for increasing bunch charge, showing increased expansion and the emergence of high-density regions due to intra-beam space–charge effects. Left to right: shaped excitation laser beam with total power of <1, 70, 210, 340, 640 and 980 μW. Lower panel: simulated bunch structure for ion bunches with spatial profiles calculated with laser profile and powers as used in the experimental images. Total bunch charges of 0 C, 2 fC, 8 fC, 10 fC, 13 fC and 19 fC. The greyscale density profiles are normalized individually to maximize contrast. Scale bar, 5 mm.