Experimental study on hard x-rays emitted from metre-scale negative discharges in air

Abstract

Please cite as: P O Kochkin et al 2015 J. Phys. D: Appl. Phys. 48 025205 Abstract.We investigate the development of meter long negative discharges and focus on their X-ray emissions. We describe appearance, timing and spatial distribution of the X-rays. They appear in bursts of nanosecond duration mostly in the cathode area. The spectrum can be characterized by an exponential function with 200 keV characteristic photon energy. With nanosecond-fast photography we took detailed images of the pre-breakdown phenomena during the time when X-rays were registered. We found bipolar discharge structures, also called "pilot systems", in the vicinity of the cathode. As in our previous study of X-rays from positive discharges, we correlate the X-ray emission with encounters between positive and negative streamers. We suggest that a similar process is responsible for X-rays generated by lightning leaders.

Electromagnetic radiation of simulated mid-gap streamers

“…The simulations show how at the range of 2.4 GHz the radiation at Eo=Ek is highly attenuated but still existing. Combining the results of [8], [9] it is shown that the x-rays might be related to the encounter of space streamers. In such encounter, the electrons would highly accelerate similar to 'overvoltage' cases simulated here.…”

“…Recently, it has been found that RF power radiation at microwave range peaks at the time of the detection of x-rays [9]. That coincidence with the optical observations of streamers [8] encouraged us to investigate the electromagnetic spectrum radiation by streamers.…”

“…At ground, x-ray emissions are associated at the leader step phase [3][4][5]. These two discoveries promoted the mechanisms of X-ray radiation in laboratory sparks [6][7][8][9]. The investigations show that x-ray primary occur before the breakdown in fast voltage impulses.…”

“…The investigations show that x-ray primary occur before the breakdown in fast voltage impulses. By means short exposure intensified cameras [8] found that x-ray emissions were associated with streamer phase of the discharge instead with the presence of leaders. Recently, it has been found that RF power radiation at microwave range peaks at the time of the detection of x-rays [9].…”

Observation of hard radiations in a laboratory atmospheric high-voltage discharge

“…Of course, such a possibility can not be rejected completely, however, with high probability we can assume that this signal (with SD1) is formed by fast neutrons. Moreover most part of experiments with laboratory discharges give the energy of gamma rays at level of 150-200 keV [16][17][18][19]. At the same time, for another shot (Fig.…”