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)

Organizational Form and Industry Emergence: Nonprofit and Mutual Firms in the Development of the U.S. Personal Finance Industry

Economic theories of commercial nonprofits and mutuals usually emphasise the advantages of such organisational forms in reducing agency and monitoring costs in markets that suffer from information asymmetries in exchanges between firms and their customers. This article examines the ability of such transaction cost theories to account for historical variations in the ownership and governance of firms in the US personal finance industry between the early nineteenth century and the Great Depression. It focuses, in particular, on mutual savings banks and their role in the development of the intermediated market for savings accounts. While I find some evidence in support of transaction cost theories of organisational form, I also find that entrepreneurial and socio-political factors played crucial roles in the choice of ownership and governance structures; mutual savings banks predominated in the early years of the industry because the form offered entrepreneurial advantages over investor-owned corporations and because in some states they benefited from regulatory and political advantages that joint-stock companies lacked. Their relative decline by the early twentieth century was the result of increasing competition in the market for savings deposits, the loosening of regulatory barriers to entry, and changes in public policy that reduced the transaction, innovation, and regulatory advantages that the mutual savings bank form had once held. The article draws out the theoretical implications for our understanding of the historical role of nonprofit and mutual firms