FIG. 10 shows the F-crosssection of FIG. 9 (dotted box), and how multiple vertical linear sensor arrays (VLSAs) can be combined. Each VLSA has a narrow field-of-view, taken from a specific viewing angle. These views combine, overlapping in the center, so that even if a bubble of fuel is not in the exact center of a vertically rising FLiBe column, it will still be likely to detect it by at least one of these arrays. In addition, having multiple arrays increases both the sensor resolution and the maximum rate of laser pumping.