Download or read book Hydromagnetic Stability and Collisional Properties of Current driven Plasma Jets written by Thomas Carlton Underwood and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Pulsed plasma accelerators have been a research focus for many decades. They have the unique ability to generate high velocity, hydromagnetic jets with tunable compression and collimation. These features allow for both high acceleration efficiency and directed heat fluxes that are ideal for applications like space propulsion or ablative material testing. Such devices have led to fundamental contributions in the production of laboratory astrophysical jets, plasma jet driven magnetized target fusion, z-pinch schemes, and spheromak compact toroids. This work focuses on investigating two distinct issues with hydromagnetic flows that have conventionally limited both the scalability and efficiency of applications, namely, flow stability and collisionality. The basis of these studies is first informed by a detailed characterization of the plasma jet produced in the Stanford gun experiment. A combination of line broadening, high bandwidth imaging, electrical probes, and modeling is used to measure the equilibrium properties of the plasma jet. It is shown that the Stanford gun device can produce plasma jets with characteristic velocities of V ~ 100 km/s, number densities up to n ~ 10^23 m^-3, and magnetic Reynold's numbers of Re_m ~ 100. A detailed scaling of these parameter against both machine operating conditions and corresponding astrophysical phenomena is also given. The manner in which magnetized plasma jets evolve remains key to better understanding the stability of hydromagnetic systems and providing new insights into how they can be dynamically controlled. The underlying theory, apparatus, and optical features of a novel schlieren diagnostic capable of cinematically visualizing dense plasma jets is described. This diagnostic features the unique ability to simultaneously resolve both the characteristic Alfvenic timescales and spatial flow features with continuous acquisition over the lifetime of a jet. This diagnostic is employed to visualize the formation and evolution of stable hydromagnetic jets produced from a plasma gun device. Dynamic coherent flow features are identified and tracked over time throughout the evolutionary progression of plasma jets. To explain the apparent stabilizing behavior, a linear stability analysis of the magnetohydrodynamic equations is performed to identify the underlying mechanism contributing to the observed behavior. The results indicate that a stable dense plasma jet can be maintained for timescales over which a steady pinch current can be sustained, even at levels which would otherwise lead to rapid unstable mode growth and resultant pinch disassembly. Collisionality is first described in the plasma accelerator by considering the impact of the initial neutral gas distribution within the gun volume. A model based on the Rankine-Hugoniot formulation in combustion is presented and used to predict both characteristic operating regimes observed experimentally. Precise neutral gas triggering is used to change the gas distribution within the accelerator and modify the initial conditions governing the breakdown process. Both bulk energy transfer and time-of-flight measurements show that with increasing gas diffusion time, the directed energy in the flow decreases and the mode transitions from a deflagration or jet to a detonation or ``snowplow'' mode. Neutral gas simulations indicate that neutral gas governs the transition between these operating modes. This informs strategies to maintain high acceleration efficiency in pulsed plasma accelerators and eliminate shocking conditions caused by higher gas loadings. Finally, the role of flow collisionaliy is also considered in the context of using plasma guns to simulate high heat loadings caused by plasma disturbances in fusion reactors. Plasma gun devices have been used extensively to replicate ELM conditions in the laboratory, however feature higher density, lower temperatures, and thus higher flow collisionality than those expected in fusion conditions. Experimental visualizations are shown that indicate strong shocks form in gun devices during material stagnation over spatial and temporal scales that precede ablation dynamics. These measurements are used to validate magnetohydrodynamic simulations that capture the production of plasma jets and the shielding effect collisionality plays in particle transport to material surfaces. Simulations show that self-shielding effects in plasma guns reduce the free streaming heat flux by up to 90\% and further reduce the incoming particle kinetic energy impinging on material surfaces. These simulations are performed over a range of operating conditions for gun devices and a discussion is provided regarding how existing experimental measurements can be interpreted when extrapolating to fusion conditions.

Download or read book Collisional Current Drive in Two Interpenetrating Plasma Jets written by and published by . This book was released on 2011 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Effect of Collision on a Cross field Current driven Plasma Instability written by Richard David Lee and published by . This book was released on 1977 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976-05 with total page 912 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Fusion Energy Update written by and published by . This book was released on 1980 with total page 68 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Evolution and Dynamics of Magnetized Plasma Jets in the MoCHI LabJet Experiment written by Eric Sander Lavine and published by . This book was released on 2018 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt: Magnetized plasma jets are generally modeled as magnetic flux tubes filled with flowing plasma governed by magnetohydrodynamics (MHD). Recent theoretical work has outlined a more fundamental approach based on flux tubes of canonical vorticity, where canonical vorticity is defined as the circulation of a species’ canonical momentum. This approach extends the concept of magnetic flux tube evolution to include the effects of finite particle momentum and enables visualization of the topology of plasma jets in regimes beyond MHD. Under the appropriate conditions, this framework suggests how to form and drive stable, collimated plasma jets with very long aspect ratios. To explore this possibility, a triple electrode planar plasma gun (MoCHI.LabJet) has been designed to produce helical shear flows inside a driven, magnetized plasma jet. This thesis presents the motivation, foundational theory, design, and initial results from this novel pulsed power experiment. The formation of long (1.1 m), collimated, stable jets with aspect ratios ≳20:1 was observed following an improvement to the insulation between the gun electrodes. Ion Doppler spectroscopy measurements of these jets suggest the presence of strong helical flows with sufficient shear to stabilize current driven kink-instabilities. Magnetic field measurements suggest an additional mechanism for enhanced stability by indicating that the magnetic field of the jet is qualitatively similar to a Taylor double helix. Strong flows, a plasma [beta]≈1, and the unbounded nature of jets in the MoCHI experiment; however, are inconsistent with a Taylor state, suggesting a unique and heretofore unobserved plasma state that may be best described as a generalized, non-Taylor, driven equilibrium.

Download or read book Dynamics of Magnetically Driven Plasma Jets written by Auna Louise Moser and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Numerical and Analytical Studies of the MHD driven Plasma Jet Instabilities and Waves written by Xiang Zhai and published by . This book was released on 2015 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes a series of experimental, numerical, and analytical studies involving the Caltech magnetohydrodynamically (MHD)-driven plasma jet experiment. The plasma jet is created via a capacitor discharge that powers a magnetized coaxial planar electrodes system. The jet is collimated and accelerated by the MHD forces. We present three-dimensional ideal MHD finite-volume simulations of the plasma jet experiment using an astrophysical magnetic tower as the baseline model. A compact magnetic energy/helicity injection is exploited in the simulation analogous to both the experiment and to astrophysical situations. Detailed analysis provides a comprehensive description of the interplay of magnetic force, pressure, and flow effects. We delineate both the jet structure and the transition process that converts the injected magnetic energy to other forms. When the experimental jet is sufficiently long, it undergoes a global kink instability and then a secondary local Rayleigh-Taylor instability caused by lateral acceleration of the kink instability. We present an MHD theory of the Rayleigh-Taylor instability on the cylindrical surface of a plasma flux rope in the presence of a lateral external gravity. The Rayleigh-Taylor instability is found to couple to the classic current-driven instability, resulting in a new type of hybrid instability. The coupled instability, produced by combination of helical magnetic field, curvature of the cylindrical geometry, and lateral gravity, is fundamentally different from the classic magnetic Rayleigh-Taylor instability occurring at a two-dimensional planar interface. In the experiment, this instability cascade from macro-scale to micro-scale eventually leads to the failure of MHD. When the Rayleigh-Taylor instability becomes nonlinear, it compresses and pinches the plasma jet to a scale smaller than the ion skin depth and triggers a fast magnetic reconnection. We built a specially designed high-speed 3D magnetic probe and successfully detected the high frequency magnetic fluctuations of broadband whistler waves associated with the fast reconnection. The magnetic fluctuations exhibit power-law spectra. The magnetic components of single-frequency whistler waves are found to be circularly polarized regardless of the angle between the wave propagation direction and the background magnetic field.

Download or read book Documentation of Plasma Physics Pt 1 Experimental Plasma Physics and Theoretical Plasma Physics written by and published by . This book was released on 1981 with total page 532 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1989 with total page 932 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1994 with total page 892 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Plasma Physics Index written by and published by . This book was released on 1981 with total page 834 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Energy Research Abstracts written by and published by . This book was released on 1978 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INIS Atomindex written by and published by . This book was released on 1985 with total page 952 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INIS Thesaurus written by and published by . This book was released on 1986 with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Scientific and Technical Reports written by United States. National Aeronautics and Space Administration Scientific and Technical Information Division and published by . This book was released on 1966 with total page 1440 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Selected Listing of NASA Scientific and Technical Reports for written by United States. National Aeronautics and Space Administration. Scientific and Technical Information Division and published by . This book was released on 1965 with total page 1680 pages. Available in PDF, EPUB and Kindle. Book excerpt: