EP2

The group "Experimental Physics II - Reactive Plasmas" at the faculty of physics and astronomy at Ruhr University Bochum.

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Nanosecond pulsed discharges in distilled water - Part I: Continuum radiation and plasma ignition

Nanosecond plasmas in liquids are an important method to trigger the water chemistry for electrolysis or for biomedical applications in plasma medicine. The understanding of these chemical processes relies on knowing the variation of the temperatures in these dynamic plasmas. This is analyzed by monitoring nanosecond pulsed plasmas that are generated by high voltages (HV) at 20 kV and pulse lengths of 10 ns applied to a tungsten tip with 50 micrometer diameter immersed in water. Plasma emission is analyzed by optical emission spectroscopy (OES) ranging from UV wavelengths of 250 nm to visible wavelengths of 850 nm at a high temporal resolution of 2 ns. The spectra are dominated by the black body continuum from the hot tungsten surface and line emissions from the hydrogen Balmer series. Typical temperatures of up to 6000 K to 8000 K are reached for the tungsten surface corresponding to the boiling temperature of tungsten at varying tungsten vapor pressures. The analysis of the ignition process and the concurrent spectral features indicate that the plasma is initiated by field ionization of water molecules at the electrode surface. At the end of the pulse, field emission of electrons can occur. During the plasma pulse, it is postulated that the plasma contracts locally at the electrode surface forming a hot spot. This causes a characteristic contribution to the continuum emission at small wavelengths.

FieldValue
Publisher
Authors
Release Date
2019-12-23
Resources
Identifier
2e1e5452-fd7e-4330-8915-87d305813f48
Permanent Identifier (URI)
Is supplementing
Plasma Source Name
Plasma Source Application
Plasma Source Specification
Plasma Source Properties
20 kV, 4 mJ
Plasma Source Procedure
50 micrometer tungsten tip immersed in distilled water. FID power supply using a 12 meter cable between power supply and plasma electrode. BCS at middle position to measure voltage and current.
Plasma Medium Name
Plasma Medium Properties
distilled water, deionized
Plasma Medium Procedure
degassed water
Plasma Diagnostic Name
License
Public Access Level
Restricted
Rights
Not yet Publisher Data
Funding Agency
Project
Subproject
Contact Name
Achim von Keudell
Contact Email

Data and Resources