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

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Control of the chemistry of a humidified He RF atmospheric pressure plasma jet by pulse modulation

Pulse modulation of an RF-driven atmospheric pressure plasma jets (APPJs) can be used to control the production of short-lived and long-lived species. This was applied for the production of H2O2 by a humidified He APPJ operating at 13.56 MHz. In addition to H2O2, several species involved in plasma chemistry were measured for the first time using different diagnostic methods applied to the same plasma source and under the same conditions: OH by LIF, H2O2 by FTIR and mass spectrometry and HO2, H2 and O2 by mass spectrometry. The feed gas humidity and dissipated plasma power are control parameters for all species. The highest species densities are found for H2 and O2, medium densities for H2O2 and OH, while the OH radical has the lowest density. Pulse modulation of the RF signal was performed with duty cycles of 10% and 50% and various numbers of pulses per residence time of the gas. With an increasing number of pulses per residence time, an accumulation of the long-lived H2O2 is evident while the formation of the short-lived OH radical is suppressed. H2 and O2 showed remarkable differences when pulse modulation is applied, as the H2 density is reduced by half and the O2 density increases almost fivefold. Thus, the chemistry under pulse modulation of the RF signal is shifted to O-containing chemistry.

FieldValue
Publisher
Authors
Release Date
2025-10-01
Identifier
834f7a28-91c2-4ca6-8edd-1262e77066f9
Permanent Identifier (URI)
Is supplementing
Plasma Source Name
Plasma Source Application
Plasma Source Specification
Plasma Source Properties
Two stainless steel electrodes with capillary (borosilicate, wall thickness 0.2mm) in between. Dimension of plasma: width: 1mm, length: 40mm, height: 1mm, Volume: 40mm³. Distance between electrodes: 1.4mm. Distance between electrode (plasma) end to capillary exit: 10mm. Sinusoidal waveform at 13.56 MHz with voltages (rms) between 150 and 700V. Plasma powers of up to 10W. Gas composition varies. Pulse modulation of the RF signal by low-frequency pulsing: 10% or 50% and frequencies from 42 Hz to 2 kHz
Language
English
License
Plasma Medium Name
Plasma Medium Properties
Flow rate: 1 slm, humidity admixtures: 0 - 6400ppm (0-100% of gas flow through ice cooled bubbler)
Plasma Medium Procedure
Cooling of the bubbler 1h before measurements with 900mL ice cubes and 400mL fridge cooled water.
Contact Name
Schüttler, Steffen
Contact Email
Plasma Diagnostic Properties
Thermocouple to measure temperature in the effluent with extrapolation into the gas phase, OES for temperature measurement using OH band, LIF for detection of OH, FTIR for detection of H2O2, mass spectrometry for H2O, H2O2, HO2, H2 and O2
Public Access Level
Public
Plasma Diagnostic Name
Funding Agency
Project
Subproject

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