Modeling the effect of anisotropic pressure on tokamak plasmas normal modes and continuum using fluid approaches

Extending the ideal MHD stability code MISHKA, a new code, MISHKA-A, is developed to study the impact of pressure anisotropy on plasma stability. Based on full anisotropic equilibrium and geometry, the code can provide normal mode analysis with three fluid closure models: the single adiabatic model (SA), the double adiabatic model (CGL) and the incompressible model. A study on the plasma continuous spectrum shows that in low beta, large aspect ratio plasma, the main impact of anisotropy lies in the modification of the BAE gap and the sound frequency, if the q profile is conserved. The SA model preserves the BAE gap structure as ideal MHD, while in CGL the lowest frequency branch does not touch zero frequency at the resonant flux surface where $m+nq=0$, inducing a gap at very low frequency. Also, the BAE gap frequency with bi-Maxwellian distribution in both model becomes higher if $p_\perp > p_\parallel$ with a q profile dependency. As a benchmark of the code, we study the m/n=1/1 internal kink mode. Numerical calculation of the marginal stability boundary with bi-Maxwellian distribution shows a good agreement with the generalized incompressible Bussac criterion [A. B. Mikhailovskii, Sov. J. Plasma Phys 9, 190 (1983)]: the mode is stabilized(destabilized) if $p_\parallel < p_\perp (p_\parallel > p_\perp)$

Analysing the impact of anisotropy pressure on tokamak equilibria

Neutral beam injection or ion cyclotron resonance heating induces pressure anisotropy. The axisymmetric plasma equilibrium code HELENA has been upgraded to include anisotropy and toroidal flow. With both analytical and numerical methods, we have studied the determinant factors in anisotropic equilibria and their impact on flux surfaces, magnetic axis shift, the displacement of pressures and density contours from flux surface. With $p_\parallel/p_\perp \approx 1.5$, $p_\perp$ can vary 20% on $s=0.5$ flux surface, in a MAST like equilibrium. We have also re-evaluated the widely applied approximation to anisotropy in which $p^*=(p_\parallel + p_\perp)/2$, the average of parallel and perpendicular pressure, is taken as the approximate isotropic pressure. We find the reconstructions of the same MAST discharge with $p_\parallel/p_\perp \approx 1.25$, using isotropic and anisotropic model respectively, to have a 3% difference in toroidal field but a 66% difference in poloidal current

Impact of lower oil prices on renewable energy technologies

The impacts of reduced oil prices on the economic viability of selected technologies which utilize solar, wind and biomass energy sources are examined. The technologies include dendrothermal, bagasse, fuel alcohol, wind electric, biomass gasifiers, solar water heaters, photovoltaic water pumps, and wind pumps. Specific projects in each of these categories are reviewed with oil prices above US$28 bbl, and their economic justifications recalculated at a range of lower oil prices. The findings indicate that the economic sensitivity of renewable energy technologies is mainly a function of scale and project location. Renewable energy technologies that compete directly in the modern large scale sector, such as dendrothermal are the most adversely affected by falling oil prices. Remote and rural applications are less affected because of their generally smaller sizes, and the reduced availablility and consequently greater costs of petroleum fuels.Energy and Environment,Energy and Poverty Alleviation,Environmental Economics&Policies,Energy Demand,Oil Refining&Gas Industry

Portable, Powerless Automation of Valve Actuation for Microfluidic Large Scale Integration Technology

Microfluidic large-scale integration (mLSI) is an emerging field that has the potential to fully automate the biological experimentation and technology development. mLSI offers high-throughput, while maintaining reduced costs and sample size in biochemical tests and experiments. The pneumatic control systems, and the use of solenoid valves that are needed for mLSI make this technology bulky and limits its use to specialized labs. Moreover, since the field is relatively new, few scientists are trained in microfluidic chip design and microfabrication. Eliminating the peripheral equipment from standard testing protocol will allow mLSI to be used in point-of-care settings and more widespread usage of this powerful technology. Our device is a portable, powerless alternative that operates without the use of costly solenoid valves and microcontrollers. In this report, we present a proof of concept demonstrating our device has potential in scalability, high throughout experimentation, and ease of use

Guiding Cooperative Stakeholders to Compromise Solutions Using an Interactive Tradespace Exploration Process

Engineering projects frequently involve the cooperation of multiple stakeholders with varying objectives and preferences for the resulting system. Finding a mutually agreeable solution is of paramount importance in order to assure the successful completion of these projects, particularly when different stakeholders are splitting the costs because none can afford to finance the project on their own. This paper proposes a process for uncovering potential mutually agreeable solutions between conflicting stakeholders, without relying on hypothetical aggregate or super-stakeholder preferences, by using guided individual preference compromises and efficiency tradeoffs. Opportunities for experimentally testing the process, with results investigating its usability and solution quality, are discussed. Further directions to improve and expand the process are also discussed, with attention paid to the design of the process as it relates to promoting an implied concept of “goodness” or “fairness” of compromise along with the ability of the process to incorporate advanced interactive technology to improve knowledge retention and understanding of the participating stakeholders.Massachusetts Institute of Technology. Systems Engineering Advancement Research Initiativ

Energetic Geodesic Acoustic Modes Associated with Two-Stream-like Instabilities in Tokamak Plasmas

An unstable branch of the energetic geodesic acoustic mode (EGAM) is found using fluid theory with fast ions characterized by their narrow width in energy distribution and collective transit along field lines. This mode, with a frequency much lower than the thermal GAM frequency ωGAM, is now confirmed as a new type of unstable EGAM: a reactive instability similar to the two-stream instability. The mode can have a very small fast ion density threshold when the fast ion transit frequency is smaller than ωGAM, consistent with the onset of the mode right after the turn-on of the beam in DIII-D experiments. The transition of this reactive EGAM to the velocity gradient driven EGAM is also discussed

Key Signature Estimation

The problem of automatic key signature detection has been the focus of much research in recent years. Previous methods of key estimation have focused on chromagrams and key profiling techniques. This paper presents a remarkably simple but effective method of estimating key signature from musical recordings. The algorithm introduces the keyogram , a concept resembling the chromagram, and is aimed for use on traditional Irish music. The keyogram is a measure of the likelihood of each possible major key signature based on a masked scoring system

Linear radial structure of reactive energetic geodesic acoustic modes

In this paper we have developed a fluid model to study the radial mode structure of the reactive energetic geodesic acoustic modes (reactive EGAMs), a branch of GAM that becomes unstable in the presence of a cold fast ion beam. We have solved the resulting dispersion relationship, a second order ODE, both analytically in restricted cases and numerically in general. It is found that the reactive EGAM global mode structure is formed with the inclusion of fast ion finite drift orbit effects. In two cases with typical DIII-D parameters but different q profiles, the global EGAM frequency is slightly higher than the local EGAM extremum, located either on axis with a monotonic shear or at mid-radius with a reversed shear. The mode wavelength roughly scales 1 2 with Lorbit in the core and L orbit at the edge, though the dependency is more complicated for the reversed shear case when L orbit < 0.06a (L orbit is the fast ion drift orbit width and a the minor radius). Finally, the growth rate of the global mode is boosted by 50% to 100% when switching from co-beam to counter-beam, depending on the fast ion density, which may help to explain the more frequent occurrence of EGAMs with counter-injection in experiments.Australian Research Council DP14010079