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)

Food resources of postlarval brown shrimp (Penaeus aztecus) in a Texas salt marsh.

p. 329-337.Field and laboratory experiments were conducted to identify the sources of food in the natural diet of postlarval brown shrimp (Penaeus aztecus Ives). A series of enclosures placed in East Lagoon (29 degrees 20' N, 94 degrees 45' W) on Galveston Island, Texas, USA, in May 1985, were used to evaluate the individual and combined contribution Spartina alterniflora detritus , epiphytes of S. alterniflora, plankton and demersal fauna in terms of differences in shrimp growth and carbon assimilation (stable carbon-isotope analysis). Demersal fauna (harpacticoid copepods, amphipods, tanaids and polychaete annelids), and plankton (>0.095 mm) accounted for approximately 53 and 47% of the growth of the post larvae (11 to 22 mm rostrum-telson length), respectively, while the authchthonous plant substrates, S. alterniflora detritus and epiphytes, contributed little. Laboratory experiments confirm that a mixed diet consisting of both animal protein and phytoplankton promates maximum growth. Our results indicate that plankton may be an important allochthonous source of carbon contributing to the growth and development of shrimp in the salt marsh.http://gbic.tamug.edu/request.ht