Ignition and propagation of nanosecond pulsed plasmas in distilled water - negative vs. positive polarity applied to a pin electrodeNanosecond plasmas in liquids are being used for water treatment, electrolysis or biomedical applications. The exact nature of these very dynamic plasmas and most important their ignition physics are strongly debated. The ignition itself may be explained by two competing hypothesis: ignition in water may occur (i) via field effects at the tip of the electrode followed by tunneling of electrons in between water molecules causing field ionization or (ii) via gaseous processes of electron multiplication in nanovoids that are created from liquid ruptures due to the strong electric field gradients. Both hypothesis are supported by theory, but experimental data are very sparse due to the difficulty to monitor the very fast processes in space and time. In this paper, we are analyzing nanosecond plasmas in water that are created by applying a positive and a negative polarity to a sharp tungsten electrode. The main diagnostics are fast camera measurements and fast emission spectroscopy. It is shown that plasma ignition is dominated by field effects at the electrode-liquid interface either as field ionization for positive polarity or as field emission for negative polarity. This leads to a hot tungsten surface at a temperature of 7000 K for positive polarity, whereas the surface temperature is much lower for negative polarity. At ignition, the electron density reaches 4 $\cdot$ 10$^{25}$ m$^{-3}$ for the positive and 2 $\cdot$ 10$^{25}$ m$^{-3}$ for the negative polarity. At the same time, the emission of the \Ha~light for the positive polarity is 4 times higher than that for the negative polarity. During plasma propagation, the electron densities are almost identical of the order of 1 to 2 $\cdot$ 10$^{25}$ m$^{-3}$ followed by a decay after the end of the pulse over 15 ns. It is concluded that plasma propagation is governed by field effects in a low density region that is created either by nanovoids or by density fluctuations in super critical water surrounding the electrode that is created by the pressure and temperature at the moment of plasma ignition.

]]>nanosecond dischargeplasma in liquidsPlasma in Liquids833519d2-1eec-4821-87a0-bbf6b88b1e6c2021-05-15T19:05:15+02:002024-03-22T12:37:41+01:00EP2Figure 5b emission intensity vs. voltage neg. pol.2021-05-17T13:49:34+02:002021-08-17T15:36:37+02:00text/plaintxt7859https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-4Figure 6b bubble radius evolution neg. pol.2021-05-17T13:50:38+02:002021-08-17T15:36:57+02:00text/plaintxt1108https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-5Figure 6b bubble radius evolution pos. pol.2021-05-17T13:50:56+02:002024-03-22T12:38:28+01:00text/plaintxt1065https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-6Figure 8a emission spectra pos. pol.2021-05-17T13:52:33+02:002021-08-17T15:37:15+02:00text/plaintxt300568https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-7Figure 8b emission spectra neg. pol.2021-05-17T13:52:57+02:002021-08-17T15:37:30+02:00text/plaintxt585112https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-8Figure 9a spectra analysis pos. pol.2021-05-17T13:53:23+02:002021-08-17T15:37:51+02:00text/plaintxt9210https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-9Figure 9b spectra analysis neg. pol.2021-05-17T13:53:44+02:002021-08-17T15:38:06+02:00text/plaintxt9061https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-10Figure 10 electron densities2021-05-17T13:54:07+02:002021-08-17T15:38:23+02:00text/plaintxt1425https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-11Figure 10 Electron densitiesElectron densities for positive and negative pulse.

]]>2021-08-17T15:21:39+02:002021-09-28T14:33:43+02:00text/csvcsv1425https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-12Figure 9b spectra analysis neg. pol.2021-08-17T15:23:44+02:002024-03-22T12:38:28+01:00text/csvcsv9003https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-13Figure 9a spectra analysis pos. pol.2021-08-17T15:24:05+02:002024-03-22T12:38:28+01:00text/csvcsv9152https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-14Figure 8b emission spectra neg. pol.2021-08-17T15:24:28+02:002024-03-22T12:38:28+01:00text/csvcsv292555https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-15Figure 8a emission spectra pos. pol.2021-08-17T15:24:48+02:002024-03-22T12:38:28+01:00text/csvcsv300568https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-16Figure 6b bubble radius evolution pos. pol.2021-08-17T15:25:08+02:002024-03-22T12:38:28+01:00text/csvcsv1065https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-17Figure 6b bubble radius evolution neg. pol.2021-08-17T15:25:47+02:002024-03-22T12:38:28+01:00text/csvcsv1108https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-18Figure 5b emission intensity vs. voltage neg. pol.2021-08-17T15:26:06+02:002024-03-22T12:38:28+01:00text/csvcsv7801https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-19Figure 5a emission intensity vs. voltage pos. pol.2021-08-17T15:26:25+02:002024-03-22T12:38:28+01:00text/csvcsv7535https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-20Figure 3 BCS voltage data for both polarities2021-08-17T15:26:43+02:002024-03-22T12:38:28+01:00text/csvcsv78425https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-21Figure 2b Emission spectra modelling neg. pol.2021-08-17T15:27:02+02:002024-03-22T12:38:04+01:00text/csvcsv114718https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-22Figure 2a Emission spectra modelling pos. pol.2021-08-17T15:27:19+02:002024-03-22T12:38:04+01:00text/csvcsv105062https://rdpcidat.rub.de/dataset/ignition-and-propagation-nanosecond-pulsed-plasmas-distilled-water-negative-vs-positive-23DKANhttps://rdpcidat.rub.de