On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Chemical Modifications of BDH-TTP [2,5-Bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene]: Control of Electron Correlation

Organic molecular conductors with a strongly correlated electron system, in which the itinerancy of electrons (or holes) and the electron correlation (U/W, U, the on-site Coulomb repulsion, W, the bandwidth) compete with each other, are promising candidates for achieving superconductivity and also for exploring remarkable physical properties induced by external stimuli such as pressure, light, voltage and current. Our synthetic approach to the construction of strongly correlated organic electron systems is based on chemical modifications to the donor molecule BDH-TTP [2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] capable of producing metallic CT (charge-transfer) salts stable down to low temperatures (4.2–1.5 K). This aims at enhancing the electron correlation in the itinerant electron system by decreasing the bandwidth. Chemical modifications of BDH-TTP such as ring expansion of two outer dithiolane rings, replacement of one sulfur atom in an outer dithiolane ring with an oxygen atom and introduction of two methyl substituents into an outer ditiolane ring led to BDA-TTP [2,5-bis(1,3-dithian-2-ylidene)-1,3,4,6-tetrathiapentalene], DHOT-TTP [2-(1,3-dithiolan-2-ylidene)-5-(1,3-oxathiolan-2-ylidene)-1,3,4,6-tetrathiapentalene] and DMDH-TTP [2-(4,5-dimethyl-1,3-dithiolan-2-ylidene)-5-(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene], respectively. In this review, the physical properties and the crystal and electronic structures of molecular conductors derived from these donor molecules will be described