Atmosphere Optics, Spectroscopy and Lasers Laboratory  LOA-SL

ELECTROSTATIC INSTABILITIES

IN LOW-TEMPERATURE

MAGNETIZED AND UNMAGNETIZED PLASMA (INSTAPLAS) 

Project number PN-III-P4-ID-PCE-2016-0355, supported by Ministry of Research and Innovation, CNCS-UEFISCDI 

Members: 

1.     Assoc. Prof. PhD. Eng. Dan-Gheorghe DIMITRIU, project manager 

2.     Assoc. Prof. PhD. Eng. Silviu-Octavian GURLUI 

3.     Assoc. Prof. PhD. Sebastian POPESCU 

4.     Prof. PhD. Maricel AGOP 

5.     ACS PhD. Liliana-Mihaela IVAN 

6.     ACS PhD. Stefan-Andrei IRIMICIUC 

7.     PhD. student Florin ENESCU 

8.     Vacant position, PhD. student 

Scientific overview: Plasma stability and its active control are major research tasks in view of developing and optimization of applications. For example, the fusion plasma instabilities delayed for such a long time the development of the first fusion energy plant. The instabilities are also present in space plasmas and the laboratory experiments proved to offer very good results for their characterization. 

Instabilities appear as soon as the plasma is externally constraint, the constraints being imposed by the applications in form of electric and magnetic fields or gradients, pressure, temperature or density gradients, geometrical constraints of the plasma device, etc. Plasma instabilities generally behave as oscillations (regular or not) of some plasma parameters and can lead to the disruption of the plasma column (as in the case of the fusion plasma) or to the appearance of chaotic states. Very often, the nonlinear dynamics of some complex space charge structures in form of double layers or multiple double layers leads to the onset of certain plasma instabilities, such as the ion-acoustic instability (in unmagnetized plasma) or potential relaxation instability and electrostatic ion-cyclotron instability (in magnetized plasma). Because of this, the dynamics of such complex structures will be also in our attention. 

Related to the instability phenomenology, very interesting nonlinear phenomena are associated, like bistability, multistability, hysteresis, memory, negative differential resistance, self-organization or chaos. All of these are hot topics not only of the plasma physics, but also in other scientific domains (engineering, electronics, medicine, economy, biology, chemistry, social science, etc.) because of their implications and applications. Thus, the study of the instabilities, as well as of the chaotic states of plasma is a challenging task, because of its interdisciplinary and transdisciplinary characters. The subject is at the edge of knowledge, allowing us to approach very complex experimental and theoretical modeling methods and having a big potential to obtain exciting results, suitable for publication in high-rated journals. 

We will focus on the open problems in this field of study: physical processes at the origin of the onset of plasma instabilities, identification of the energy sources that maintain the plasma instabilities, physical nature of the negative differential resistance, hysteresis, bistability and multistability in plasma, experimental control of plasma instabilities, transition to chaos in plasma, characterization of chaotic states of plasma, experimental control of chaos in plasma, theoretical modeling of plasma instabilities and chaotic states of plasma, relevance of the laboratory low-temperature plasma studies for other types of plasma, or for similar phenomena in other branches of science, applications. 

The methodology consists of experimental and theoretical modeling approach. 

The experiments will be performed in both magnetized and unmagnetized plasmas, in different kinds of experimental devices: plasma diodes (with and without magnetic field) with metallic or dielectric walls, double plasma (DP) machine and Q machine. Different diagnosis methods will be used, some of them simultaneously when this will be possible: Langmuir probes, emissive probes, electrostatic analyzers, laser induced fluorescence, space- and time-resolved optical emission spectroscopy, fast ICCD imaging and energy selective mass spectrometry. Modern methods of nonlinear dynamics will be applied for the analysis of the recorded experimental data. At least four instabilities will be analyzed: ion-acoustic instability, laser ablation plasma plume instability, potential relaxation instability and electrostatic ion-cyclotron instability. A special attention will be payed to the simultaneous excitation of these instabilities and the study of the complex phenomena arising during their interaction. The nonlinear dynamics of some complex space charge structures in plasma, as well as the analysis of chaotic states of plasma will be also approached during our research. 

For the theoretical modeling, the fractal hydrodynamic model developed in the frame of the scale relativity theory will be mainly applied, because it gives good results in the case of complex systems that acquire self-similarity and manifest strong fluctuations at all possible scales, as also plasma behaves. The scale relativity theory applies the principle of relativity to scale transformations. The standard laws of classical physics (motion in space-time) are completed by new scale laws (the space-time resolutions are used as intrinsic variables, playing for the scale transformation the same role as played by velocities for motion transformation). Because of the collisions, the particles (electrons, ions, neutrals) movements in plasma take place on continuous, but non-differentiable curves, i.e. fractal curves. The movement complexity is directly related to the fractal dimension of the trajectory. In this theoretical framework, the particle may be reduced to and identified with its own trajectory. Then, plasma will behave as a special collisionless fluid by means of geodesics in a fractal space-time. Such a model was already successfully applied by our group in describing the nonlinear dynamics of complex space charge structures in plasma as fireballs, multiple double layers and laser ablation plumes, as well as their transition to chaos. 

Dissemination 

1.     S. Popescu – Turing instability and spatial self-organization in plasma, 16^th International Conference on Global Research and Education, Iasi, Romania, 25-29 September 2017, oral presentation;  

2.     D. G. Dimitriu, M. Agop – Spontaneous symmetry breaking related to the onset of instabilities in low-temperature plasma, Symmetry 2017 – The First International Conference on Symmetry, Barcelona, Spain, 16-18 October 2017; 

3.     S. Popescu, D. G. Dimitriu – On energy transformation and entropy production in a dc gas discharge, Entropy 2018 – From Physics to Information Science and Geometry, Barcelona, Spain, 14-16 May 2018; 

4.     C. T. Teodorescu-Soare, D. G. Dimitriu, O. Vasilovici, C. Ionita, S. Irimiciuc, R. Schrittwieser – Experimental investigation of a discharge between two spherical concentric grid with axisymmetric holes, 19^th International Congress on Plasma Physics, Vancouver, Canada, 4-8 June 2018; 

5.     D. G. Dimitriu, S. A. Irimiciuc, M. Agop – Self-modulated oscillations in the dynamics of a hollow grid cathode discharge plasma, accepted to be presented as oral contribution to 11^th CHAOS 2018 International Conference on Non Linear Analysis and Modelling: Theory and Applications, Rome, Italy, 5-8 June 2018, oral presentation; 

6.     S. A. Irimiciuc, D. G. Dimitriu, M. Agop – Appearance and instability of non-concentric multiple double layers in low-temperature discharge plasma, accepted to be presented to 11^th CHAOS 2018 International Conference on Non Linear Analysis and Modelling: Theory and Applications, Rome, Italy, 5-8 June 2018, oral presentation; 

7.     M. Agop, S. A. Irimiciuc, D. G. Dimitriu – Transition to chaos by intermittency related to the nonlinear dynamics of non-concentric multiple double layers in low-temperature plasma, accepted to be presented to 11^th CHAOS 2018 International Conference on Non Linear Analysis and Modelling: Theory and Applications, Rome, Italy, 5-8 June 2018, oral presentation; 

8.     S. A. Irimiciuc, D. G. Dimitriu, M. Agop – A compact non-differential approach for modeling laser ablation plasma dynamics, accepted to be presented to 11^th CHAOS 2018 International Conference on Non Linear Analysis and Modelling: Theory and Applications, Rome, Italy, 5-8 June 2018, oral presentation; 

9.     S. A. Irimiciuc, D. G. Dimitriu, M. Agop – Experimental and theoretical investigations of the interaction between two complex space charge structures in hollow grid cathode discharge plasma, 24^th Europhysics Conference on Atomic and Molecular Physics of Ionized Gases (ESCAMPIG), Glasgow, UK, 17-21 July 2018; 

10.  D. G. Dimitriu, S. A. Irimiciuc – Transition to chaos by intermittency of multiple fireballs dynamics in low-temperature discharge plasma, 24^th Europhysics Conference on Atomic and Molecular Physics of Ionized Gases (ESCAMPIG), Glasgow, UK, 17-21 July 2018; 

11.  S. A. Irimiciuc, G. Bulai, D. G. Dimitriu, S. Gurlui – Role of molecule formation and multiple-structure scenarios in dynamics of laser produced plasma, 24^th Europhysics Conference on Atomic and Molecular Physics of Ionized Gases (ESCAMPIG), Glasgow, UK, 17-21 July 2018; 

12.  D. G. Dimitriu, S. A. Irimiciuc, M. Agop – Investigation of the interaction between two complex space charge structures in low-temperature plasma, Conference on Complex Systems (CCS), Thessaloniki, Greece, 23-28 September 2018; 

13.  D. G. Dimitriu, S. A. Irimiciuc, M. Agop – On the appearance and dynamics of multiple complex space charge structures in low-temperature discharge plasma, Conference on Complex Systems (CCS), Thessaloniki, Greece, 23-28 September 2018; 

14.  D. G. Dimitriu, M. Agop – Analysis of low-frequency instabilities in low-temperature magnetized plasma, Chapter 5 in the book Fractional Dynamics and Anomalous Transport in Plasma Science, ed. C. H. Skiadas, ISBN: 978-3-030-04482-4, Springer, 2018; 

15.  S. Irimiciuc, D. G. Dimitriu, M. Agop – Theoretical modeling of the interaction between two complex space charge structures in low-temperature plasma, Chapter 6 in the book Fractional Dynamics and Anomalous Transport in Plasma Science, ed. C. H. Skiadas, ISBN: 978-3-030-04482-4, Springer, 2018; 

16.  C. T. Teodorescu-Soare, S. A. Irimiciuc, C. Ionita, D. G. Dimitriu, B. Hodoroaba, T. O’Hara, O. Vasilovici, L. Amarandi, R. W. Schrittwieser – Concentric double hollow grid cathode discharges, International Journal of Mass Spectrometry 436 (2019) 83-90; 

17.  D. G. Dimitriu – On the instabilities of complex space charge structures in low-temperature plasma, Statistical Physics of Complex Systems International Conference, Stockholm, Sweden, 7-11 May 2019, oral presentation; 

18.  S. Popescu, D. G. Dimitriu – A dynamical model for plasma fireball, accepted for oral presentation to 12^th CHAOS 2019 International Conference on Non Linear Analysis and Modeling: Theory and Applications, Chania, Greece, 18-21 June 2019; 

19.  S. Popescu, D. G. Dimitriu – Nonlinear dynamics of complex space charge structures at the origin of low-frequency plasma instabilities, accepted for oral presentation to 12^th CHAOS 2019 International Conference on Non Linear Analysis and Modeling: Theory and Applications, Chania, Greece, 18-21 June 2019; 

20.  R. Schrittwieser, C. T. Teodorescu-Soare, C. Ionita, D. G. Dimitriu, O. Vasilovici, S. Gurlui, S. A. Irimiciuc, B. Hodoroaba, T. O’Hara, L. Amarandi, F. Enescu, F. Mazzanti, R. Stenzel, J. Gruenwald – Inverted fireballs, invited lecture to 18^th International Conference on Plasma Physics and Applications, Iasi, Romania, 20-22 June 2019; 

21.  D. G. Dimitriu, S. A. Irimiciuc, M. Agop – Nonlinear dynamics of non-concentric multiple double layers as a source of low-temperature plasma instabilities, accepted for poster presentation to 18^th International Conference on Plasma Physics and Applications, Iasi, Romania, 20-22 June 2019; 

22.  S. Popescu, D. G. Dimitriu – Minimum entropy production in the process of fireball formation, accepted for poster presentation to 18^th International Conference on Plasma Physics and Applications, Iasi, Romania, 20-22 June 2019; 

23.  D. G. Dimitriu, S. A. Irimiciuc, M. Agop – Low-temperature plasma instabilities and chaotic states triggered by the nonlinear dynamics of complex space charge structures, accepted for poster presentation to 46^th EPS Conference on Plasma Physics, Milan, Italy, 8-12 July 2019; 

24.  C. T. Teodorescu-Soare, S. A. Irimiciuc, C. Ionita, D. G. Dimitriu, B. Hodoroaba, T. O’Hara, O. Vasilovici, L. Amarandi, R. W. Schrittwieser – Concentric double hollow grid cathode discharges, accepted for oral presentation to 46^th EPS Conference on Plasma Physics, Milan, Italy, 8-12 July 2019; 

25.  C. T. Teodorescu-Soare, F. Enescu, C. Ionita, D. G. Dimitriu, S. Gurlui, F. Mazzanti, R. W. Schrittwieser – Spectral investigations on concentric double hollow grid cathode discharges, accepted for poster presentation to 46^th EPS Conference on Plasma Physics, Milan, Italy, 8-12 July 2019; 

26.  S. Popescu, D. G. Dimitriu – Entropy production during the fireball formation in discharge plasma, accepted for oral presentation to 34^th International Conference on Phenomena in Ionized Gases (ICPIG) & 10^th International Conference on Reactive Plasmas (ICRP), Sapporo, Japan, 14-19 July 2019; 

27.  D. G. Dimitriu, S. Popescu – Low-temperature plasma instabilities related to the nonlinear dynamics of fireballs and multiple double layers, accepted for poster presentation at 34^th International Conference on Phenomena in Ionized Gases (ICPIG) & 10^th International Conference on Reactive Plasmas (ICRP), Sapporo, Japan, 14-19 July 2019; 

28.  R. Schrittwieser, C. T. Teodorescu-Soare, F. Enescu, C. Ionita, D. G. Dimitriu, S. Gurlui, F. Mazzanti, S. A. Irimiciuc, B. Hodoroaba, T. O’Hara, O. Vasilovici, L. Amarandi – Oscillatory behavior of hollow grid cathode discharges, invited lectures to 21^st International Conference on Electromagnetics in Advanced Applications (ICEEA) & 9^th IEEE-APS Topical Conference on Antennas and Propagation in Wireless, Granada, Spain, 9-13 September;