Figure 1: Visualization of 3D experiment with heavy ion beams.

(a) Sample preparation: The piece of filter membrane was delineated in 5 × 5 mm sections with a pencil (Step 1), which was then sterilized; Cells at logarithmic phase of growth were quantitatively applied to the middle of each section on the membrane (Step 2) and dried with sterile absorbent paper (not shown in Fig. 1). (b) Irradiation target preparation: a second piece of filter membrane was placed onto the sample membrane, and the two were tightly wrapped into a cylinder together (Step 3), subsequently, we used a parafilm to seal the cylinder (not shown in Fig. 1). The cylinder was affixed to a copper sheet with a round hole (Step 4) and a plastic pipe with a incision was used to fix the cylinder (step 5) for storage at 4 °C. (c) Irradiation and preparation of the tested units: The membranes and copper sheet were irradiated with mid-high energy heavy ion beams (Step 6). Under sterile conditions, the plastic pipe and copper sheet were removed (Step 7) and the filter membrane opened (Step 8). Based on the experimental design, the filter membrane was cut into assay units along the corresponding sections lines, and numbered by assay unit (Step 9). All experiments were performed according to the assay units. CSIIE, Cross section of irradiation at initiative end; PP, Plastic pipe; RCS, Round copper sheet with a round hole at the centre; X, radial direction; Y, axial direction (i.e. irradiation direction with heavy ion beams).