Observation of Neutron Bursts Produced by Laboratory High-Voltage Atmospheric Discharge

For the first time the emission of neutron bursts in the process of high-voltage discharge in air was observed. Experiments were carried out at an average electric field strength of $\sim 1\mathrm{MV}·{\mathrm{m}}^{-1}$ and discharge current of $\sim 10\mathrm{kA}$. Two independent methods (CR-39 track detectors and plastic scintillation detectors) registered neutrons within the range from thermal energies up to energies above 10 MeV and with an average flux density of $\gtrsim {10}^6{\mathrm{cm}}^{-2}$ per shot inside the discharge zone. Neutron generation occurs at the initial phase of the discharge and correlates with x-ray generation. The data obtained allow us to assume that during the discharge fast neutrons are mainly produced.

Figure 1

The scheme of the laboratory experiment. (a) Layout of diagnostics: 1, 2, capacitive and active dividers; 3, high voltage input from Marx generator; 4, 13, magnetic probes; 5, track detectors; 6, anode shunt; 7, Rogowski coil; 8, 9, integral cameras; 10, scintillation detectors; 11, UV radiation detector; 12, PMT to visible light; 14, cathode; 15, anode. (b) Layout of CR-39 track detectors: 1, inside the anode; 2, inside the cathode; 3, 4, 5, axially placed in water; 6, 7, 8, radially placed at different distances from the discharge.

Figure 2

Different shapes of atmospheric discharge in the experiment.

Figure 3

Total distribution of track diameters. (a),(b) Detectors with radiators of $120\mu \mathrm{m}$ polyethylene, located in the anode (position 1) and in the cathode (position 2). (c) Detectors with radiators of 20% solution of ${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7$ in glycerol (position 1). (d) Detectors of the 20% solution of ${\mathrm{Na}}_2{\mathrm{B}}_4{\mathrm{O}}_7$ in glycerol with additional water moderator, placed near the anode (position 3). Dark columns correspond to the results of the experiment, and light columns to the relevant background detectors, placed 10 m in from the discharge. All positions are in accordance with Fig. 1b.

Figure 4

Typical photomicrographs of the events of ${}^{12}\mathrm{C}$ nucleus desintegration into three $\alpha$ particles (the size of the image is $130\times 100\mu {\mathrm{m}}^2$).

Figure 5

Scheme of real-time observation: (a) neutron signals, (b) oscillograms of voltage, current, x rays, and neutrons.