Regime Density Research Articles

Cooperation on Transnational Environmental Crime: Institutional Complexity Matters

There have been clear calls for enhanced international cooperation to meet the environmental, economic and criminal challenges of transnational environmental crime (TEC), defined here to include illegal wildlife trade, timber trafficking and the black market in ozone‐depleting substances. In the absence of an overarching international or transnational environmental crime legal framework, institutional settings are characterized by regime density and complexity amid a growing number of actors across related but distinct institutional settings. Scholars of international cooperation have worried that this kind of complexity leads to legal indeterminacy, normative ambiguity and regulatory uncertainty that will make cooperation more difficult. In the TEC sphere, these propositions remain under‐researched and untested. This article sketches the contours of a study that would bring some conceptual and empirical clarity to these issues. In doing so, it outlines the constitutive elements of the TEC regime complex and the nature of institutional interplay between and among those elements.

Overview of experimental results and code validation activities at Alcator C-Mod

Recent research on the Alcator C-Mod tokamak has focused on a range of scientific issues with particular emphasis on ITER needs and on detailed comparisons between experimental measurements and predictive models. Research on ICRF (ion cyclotron range of frequencies) heating emphasized the origins and mitigation of metallic impurities while work on lower hybrid current drive experiments have focused on linear and nonlinear wave interactions that limit efficiency at high densities in regimes with low single pass absorption. Experiments in core turbulence and transport focused on quantitative, multi-field comparisons between nonlinear gyro-kinetics simulations and experimental measurements of profiles, fluxes and fluctuations. Experiments into self-generated rotation observed spontaneous flow reversal at a critical density identical to the transition density between linear ohmic confinement and saturated ohmic confinement regimes. H-mode studies have measured pedestal widths consistent with kinetic-ballooning-mode-like instabilities, while the pedestal heights quantitatively match the EPED code predictions. Experiments with I-mode have increased the operating window for this promising edge-localized-mode-free regime. Extrapolation of I-mode to ITER suggests that the fusion gain Q ∼ 10 could be possible in ITER. Investigations into the physics and scaling of the power exhaust channel width in attached enhanced D-alpha H-mode and L-mode plasma showed a direct connection between the midplane pressure-folding length and the outer divertor target footprint. The width was found to scale inversely with IP, while being independent of conducted power, BT or q95 and insensitive to the scrape-off layer connection length—a behaviour that suggests critical-gradient physics sets both pressure and heat-flux profiles.

Microwave measurements of the time evolution of electron density in the T-11M tokamak

Unambiguous diagnostics intended for measuring the time behavior of the electron density and monitoring the line-averaged plasma density in the T-11M tokamak are described. The time behavior of the plasma density in the T-11M tokamak is measured by a multichannel phase-jump-free microwave polarization interferometer based on the Cotton-Mouton effect. After increasing the number of simultaneously operating interferometer channels and enhancing the sensitivity of measurements, it became possible to measure the time evolution of the plasma density profile in the T-11M tokamak. The first results from such measurements in various operating regimes of the T-11M tokamak are presented. The measurement and data processing techniques are described, the measurement errors are analyzed, and the results obtained are discussed. We propose using a pulsed time-of-flight refractometer to monitor the average plasma density in the T-11M tokamak. The refractometer emits nanosecond microwave probing pulses with a carrier frequency that is higher than the plasma frequency and, thus, operates in the transmission mode. A version of the instrument has been developed with a carrier frequency of 140 GHz, which allows one to measure the average density in regimes with a nominal T-11M plasma density of (3–5)×1013 cm−3. Results are presented from the first measurements of the average density in the T-11M tokamak with the help of a pulsed time-of-flight refractometer by probing the plasma in the equatorial plane in a regime with the reflection of the probing radiation from the inner wall of the vacuum chamber.

Heating and compression of laser-irradiated spherical targets

Heating and dynamics of compression of shell targets irradiated by a nanosecond laser pulse in the “Kal'mar” facility are investigated. Comprehensive procedures are developed and used to investigate the energy balance and the compression dynamics of the target scattered by the radiation plasma at the harmonic frequencies 2ω0 and 3/2ω0, and of the spectral distribution of the continuous x radiation. The use of the developed procedures has made it possible to clarify the dependence of the components of the energy balance on the target parameters, to establish new regularities governing the shell motion, to identify the phenomena that take place in the region of the critical and quarter-critical density, and to demonstrate experimentally the possibility of reaching in the “exploding pusher” regime densities much higher than the density of a solid body.

The upward vertical flow of air‐water mixtures: III. Effect of gas phase density on flow pattern, holdup and pressure drop

AbstractResults of measurements of pressure drop and holdup are reported over a range of air and water rates for the upward vertical flow of air‐water mixtures in a 1.50 inch I.D. tube with average air densities ranging from 0.092 to 0.552 lb./ft.3 Superficial water velocities were between 0.0695 and 7.35 ft./sec.The data are analyzed by the method first suggested by Govier, Radford and Dunn and later used by Govier and Short. This involves the division of the flow range into four regimes on the basis of the pressure drop curves (to aid correlation of flow pattern and holdup data) and the separation of the unit pressure drop into hydrostatic and irreversible components. A superficial friction factor is calculated from the irreversible component of the unit pressure drop.The average density of the gas phase has a more or less marked effect on all three regime transitions. The transitions all shift similarly to lower air‐water discharge volume ratios with increasing gas phase density. While the flow patterns were not directly observed in the investigation here reported, the flow pattern transitions would be expected to behave similarly.Over the range investigated, the gas phase density has little or no effect on the superficial friction factor. The holdup ratio is unaffected by the gas phase density in Regimes I and II but is significantly affected in Regimes III and IV.