euro-optics-plasma-science-2018-keynote

E u r o S c i C o n J o i n t E v e n t o n

Laser Optics & Photonics and

Atomic & Plasma Science

American Journal of Computer Science and Information Technology

ISSN: 2349-3917

J u l y 1 6 - 1 7 , 2 0 1 8

P r a g u e , C z e c h R e p u b l i c

Page 26

Laser Optics & Photonics and Atomic & Plasma Science 2018

n an applied research project on a pulsed microwave sulfur lamp prototype of 1

kW, fitted with a rotation less and electrode less spherical bulb, we discovered

that the plasma may form, despite gravity, a ball of about half the bulb size,

settled in the center. In a preceding publication, we then reported measurements

performed with a photodiode that shows the high-pressure plasma response to

short microwave pulses, and we showed by modelization that the ball formation

results from an acoustic resonance in a spherical mode. Out of this formation, the

signal AC component has the same frequency as the pulse rate, and resembles

to a triangular signal, rising during the ON periods and falling back during the OFF

periods. When the ball formation occurs, at a pulse rate a little below30 kHz, theAC

component changes to a sinusoidal signal of a slightly lower frequency, and beats

appear with a frequency equal to the frequency shift. In the preceding publication,

it was demonstrated that the beats could result from the simultaneous excitation

of two normal modes, because they have a frequency difference matching the

observed frequency shift. As the higher of the two frequencies is the pulse rate, the

one is due to a forced oscillation, whereas the other one is due to a free oscillation.

In this article, we study the dissipation due to bulk viscosity and, thus, identify

a mechanism that can couple the two oscillations, explaining the simultaneous

excitation.

Biography

Gilles Courret has completed his PhD at the Swiss Federal Insti-

tute of Technology (EPFL) in 1999. Since 2013, he is Professor

of Physics in the Department of Industrial Technologies of the

University of Applied Sciences and Arts Western Switzerland

(HES-SO). His research interests include Microwave-Plasma

Interaction, Plasma Chemistry, Light Sources and Illumination

Engineering, with Emphasis on the Improvement of Energy

Efficiency. He has published more than 20 papers in reputed

journals.

Coupling of two oscillations of close

frequencies in a high pressure plasma

enclosed in a spherical bulb

G Courret, P W Egolf and M Croci

University of Applied Sciences and Arts Western Switzerland

(HES-SO), Switzerland

G Courret et al., Am J Compt Sci Inform Technol 2018, Volume 6

DOI: 10.21767/2349-3917-C1-001