Plasma Morning Session

Plasma Morning Session

Plasma Session I

Chair: Reuven Boxman (TAU)



Otto Landen (LLNL)
Keynote Speaker

Breakthrough in Inertial Confinement Fusion (ICF) on the NIF

In August, the 192 laser beam 0.5 Petawatt (PW), 1.9 Megajoule (MJ) National Ignition Facility (NIF) [1] sufficiently compressed, heated and confined a deuterium-tritium (DT) plasma [2] such that it liberated enough exothermic fusion energy in a runaway “burn propagating” mode to double its temperature to 100 million degrees, producing ≈10x more peak fusion power (10 PW) and energy (1.3 MJ) than any prior attempt. This is the same form of energy that powers the Sun and the stars through gravitational confinement, and that potentially could be an enduring source of clean energy on Earth. The accomplishment was built on decades of hard work and dedication by many theoretical, computational and experimental plasma physicists, laser physicists, material scientists, chemists, precision engineers and technical staff at LLNL, in partnership with the inertial fusion, plasma, and the high energy density science community. In terms of fusion energy gain, 1.3 MJ represents 5x the energy deposited in the capsule that confines the DT and 0.7x of the incident laser energy. In context, a future inertial fusion energy power plant would require 100x more gain delivered several times a second. This talk will review the basic physics of indirect-drive ICF [3], the scientific and technical challenges that led up to creating this new regime in the laboratory, and present the unique time and space dependent conditions extracted from an array of x-ray and nuclear bolometers, cameras and spectrometers. The talk will conclude by discussing strategies based on extrapolations using a combination of simulations, theory and current results for increasing the system efficiency and hence fusion gain a further 10x in the next few years at NIF.
[1] E. I. Moses et. al., Phys. Plasmas 16, 041006 (2009)
[2] J. H. Nuckolls, L. Wood, A. Thiessen, G. B. Zimmermann, Nature 239, 129 (1972).
[3] J. D. Lindl, Phys. Plasmas 2, 3933 (1995); J.D. Lindl et. al., Phys. Plasmas 11, 339 (2004).



Hank Strauss (HRS Fusion)
Contributed Speaker

Solution of the Disruption Problem in ITER

Disruptions in ITER will be much milder in ITER than in present experiments. They will be self mitigating: disruption precursors rather than disruptions.
ITER is a large tokamak under construction in France, which is supposed to achieve magnetic fusion. It has a high strength magnetic field produced by superconducting magnets.
Like all tokamaks, it is expected to experience disruptions, caused by magnetohydrodynamic (MHD) instabilities. Because of the large size, stored energy, and magnetic field, the disruptions could damage the machine. A great deal of effort has been made to develop a disruption mitigation system, which has its own problems.
A new analysis [1,2] has shown that ITER should be much more MHD stable than previously thought. The reason is the highly conducting shell surrounding ITER, which stabilizes or slows down resistive wall modes. The new analysis shows that most disruptions in the JET tokamak are caused by resistive wall tearing modes, which are also stabilized. Simulations of ITER show that the expected disruptions will also be resistive wall tearing modes.
A key metric of ITER is the thermal quench time. This determines the thermal wall load of a disruption. Until now it has been estimated to be a few ms. This would cause severe damage unless mitigated by injection of radiative material, which can cause further problems. The new theory shows that the thermal quench time is 10 - 100 times longer than previous estimates, greatly reducing the possibility of damage.
Analysis of data, theory, and MHD simulations will be presented.
[1] H. Strauss and JET Contributors, Effect of Resistive Wall on Thermal Quench in JET Disruptions, Phys. Plasmas 28, 032501 (2021)
[2] H. Strauss, Thermal Quench in ITER Locked Mode Disruptions, Phys. Plasmas 28, 072507 (2021)



Nir Druker (Technion)
Contributed Speaker

Enhancement of Plasma Assisted Ignition by Multi-Voltage Pulse Discharges

The use of cold plasma for ignition improvement in internal combustion engines has been widely investigated in the past two decades. Usually, high voltage nanosecond pulses are repeatedly applied to facilitate such a process. Compared to traditional ignition, nanosecond repetitive pulse ignition systems demonstrate improvement in heat release rate during combustion, ignition delay time reduction and enhanced ignition process in flowing and lean reactive gas mixtures.
In this research, we conducted a preliminary, theoretical/numerical investigation into the possibility of use of on-board control of electrically-based cold plasma-assisted ignition and combustion. The focus was on diagnostics and enhancement of energy deposition in specific modes, by application of bi-polar short duration voltage pulses in low-pressure air. The physical model couples the electric field, potential and current, with the relevant conservation equations for 24 species via 168 kinetic reactions, including molecules’ rotation, vibration, electronic excitation, dissociation, and ionization inside the electrodes gap. Evaluation using various pulse repetition frequencies and different pulse shapes was conducted. Special attention was given to the overall coupled energy deposited during the discharge, and to energy channeled to known ignition supportive modes such as nitrogen electronic excitation and oxygen radicals’ generation.
The results of the analysis show that for the considered conditions, energy deposition can be divided into two main stages, characterized by high and low voltage magnitudes, respectively. It was found for the first time, that the (low voltage) second stage’s energy deposition can be higher than that of the first (high voltage) stage. At the second stage, the deposition of energy into specific modes can be tuned by setting appropriate voltage magnitudes. In addition, the energy deposited in modes important for ignition exhibits a simple linear relation to the overall energy deposition. Furthermore, based on these findings, we demonstrate how a new sequence of voltage pulses can further increase enhancement of ignition and combustion supportive processes.



Yang Cao (Technion)
Contributed Speaker

The Non-Linear High-Power Microwave Complete Absorption Phenomenon in a Plasma Filled Waveguide

We present the first experimental observation of a fully-absorption of a K-band high-power microwave (HPM) pulse (1.2 GW, 0.5 ns, 25.6 GHz)(1) in a plasma-filled waveguide.(2) The plasma density dependent waveguide cut-off frequency is near to the pulse frequency. In the plasma-filled waveguide, due to the ponderomotive force caused by HPM pulse, plasma electrons being kicked towards the waveguide wall, generating a potential well in the waveguide where the remaining electrons keeps oscillate in the HPM pulse field. At this near critical plasma density, the group velocity of the pulse decreases, which provides sufficient time for these trapped electrons to collide with ions while their regular field-induced oscillation motion becomes chaotic and thermal. This results in all the energy of the pulse being transferred to the kinetic energy of electrons. This nonlinear full-absorption phenomenon of HPM pulse is absent when pulse power is low and the potential well does not form in the waveguide. The experimental result is confirmed by 3D particle-in-cell (PIC) simulations.
1.) Y. Cao, Y. Bliokh, J.G. Leopold, V. Rostov, Y. Slutsker, and Y.E. Krasik, Phys. Plasmas 26, 023102 (2019).
2). Y. Cao, J.G. Leopold, Y.P. Bliokh, G. Leibovitch, and Y.E. Krasik, Phys. Plasmas 28, 062307 (2021).



Marko Cvejic (WIS)
Contributed Speaker

Spectroscopic measurements of the magnetic field curvature and self-rotating plasma

Z-pinches with preembedded axial magnetic field Bz0 undergo a radial implosion while compressing the plasma and the embedded magnetic flux. While the Bz flux is compressed, the Bz-lines in the metal electrode continue to be frozen at their initial radius. Thus, a transition region where the field lines are bent radially is formed. We developed novel polarization-based spectroscopic technique, that utilizes the combined effect of the Zeeman splitting and Doppler shift due to the implosion velocity, to directly measure the Bz and Br, namely the curvature. The measurements of Br allow for study the self-rotation seen for the first time, to develop in the plasma, and for correlating the rotation and the implosion with the effect of the jz × Br forces. Br measurements are essential because Br determines the rotation jz × Br and the implosion of the plasmas near the electrodes.



Sharon Waichman (NRCN, Rotem Industries)
Contributed Speaker

Enhanced adhesion of boron carbide coatings on aluminum substrates

Boron carbide is a ceramic material having superior properties, in particular big cross section for neutron absorption, which makes it suitable for nuclear applications including homeland security and accelerators. We deposited 2.0-3.5 µm boron carbide coating on an aluminum substrate using pulsed-DC magnetron sputtering. The adhesion between these two materials is challenged because of the formation of an unstable aluminum-carbon bond and the difference between their thermal expansion coefficients that may cause stress and subsequent adhesive failure. Hence, we applied an adhesive intermediate titanium layer (0.5-1.5 µm) and systematically studied the coating process parameters that affect the deposited film, mainly the impact of the titanium interlayer thickness on the adhesion, and the effect of the bias voltage applied during deposition on the growing film. We discovered that increasing the deposition power (3.3-10 W/cm2) increased, as expected, the deposition rate, but had little effect on other properties. Microstructure densification and surface morphology were studied by SEM. XRD and XPS, respectively, confirmed the predicted amorphous structure and B4C composition. XPS also revealed oxidized and carbonaceous species on the surface, which increased with energy supplied during deposition. Coatings deposited with a bias voltage higher than ~ -150 V adhered poorly to the substrate. Boron carbide coatings with thickness of at least 3.5 µm, deposited over a 1.5 µm thick titanium layer, adhered for several months (until today), in a 2% RH environment. We determined that the optimal bias voltage applied to the substrate during deposition was ~ 60 V. In summary, we determined that a continuous and a dense boron carbide coating layer will adhere well to an aluminum substrate if an intermediate titanium layer is first deposited, and optimal coating parameters are used when depositing the boron carbide layer.



Roundtable Discussion

Moderator: Reuven Boxman (TAU)
Panel members: Otto Landen (LLNL-NIF), Sharon Waichman (NRCN/Rotem Industries), Michael Keidar (GWU), Hank Strauss (HRS Fusion), Asher Yahalom (Ariel U.), Amnon Fisher (RAFAEL), Joe Lefkowitz (Technion)

Plasma for a Greener Earth


Humankind is facing an extreme challenge this century: providing for the health, welfare, and prosperity of a burgeoning human population on planet Earth, which is experiencing human induced climate change, fresh water insufficiency, rapidly spread disease, and pollution. This panel will address how plasma can help face this challenge. The much-sought “killer” plasma application is controlled nuclear fusion, which has the potential to supply power without burning fossil fuel or producing copious radioactive waste. When, if at all, can it be realized? In the shorter term, plasma can be used to depollute effluent gases and waste water from industry and agriculture. Plasma is used to produce wear resistant low friction coatings for mechanical components, which reduce energy use for the manufacture, maintenance and operation of vehicles and other machines. What else can plasma do?




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IVS-IPSTA 2021 - 39th Annual Conference
November 17, 2021 | ONLINE

Conference Organizing Team

Gilbert Daniel Nessim (IVS President, BIU) | Ilya Grinberg (BIU) | Haim Barak (BIU)

Tatyana Bendikov (WIS) | Elad Koren (Technion) | Muhammad Bashouti (BGU) 
Noa Lachman-Senesh (TAU) | Igal Kronhaus (Technion)
Sharon Waichman (NRCN, Rotem Industries)