Figure 5

Negative ion concentration distribution around the device. The height of the devices in (a) and (d) is 8 cm, 16 cm in (b) and (e), and 30 cm in (c) and (f). (a), (b), and (c) show the measurement results without the electric field. (d), (e), and (f) show the measurement results with the electric field. Areas marked with * indicate that the negative ion concentration saturated the ion counter equipment’s measurement limitation.