Lawrenceville Plasma Physics (United States)

The dense plasma focus (DPF) device has great potential as a fusion energy generator using hydrogen-boron (pB11) fuel1. Experiments using deuterium have already demonstrated mean ion energies >200 keV, in the range needed for burning pB112. To test that potential, we are preparing for experiments with hydrogen-boron fuel in the megampere DPF device, FF-2B. We plan to use isotopically-pure decaborane (B10H14) as the fuel source and have installed equipment for the safe handling and disposal of the toxic vapors from this material. High isotopic purity of the boron-11 is required to avoid generation of radioactive Be-7. While the main pB11 fusion reaction produces no neutrons, two side reactions do produce both neutrons and radioactive C-11. We show how these reaction products can be used with suitable detectors to provide accurate data on fusion yield, and the density and ion energy of the confined fusion-producing plasma.

The dense plasma focus FF-2B machine with 1.2 MA peak current is designed as a low-impurity fusion device for a high neutron yield. Using for the first time monolithic beryllium electrodes, FF-2B has achieved a forty-fold reduction of impurities by mass with a dramatic reduction in electrode erosion as compared with previous copper <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> and tungsten <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> electrodes. We observed evenly-spaced filaments initially in the sheath, but the leading portion of the current sheath becomes disordered during run-down, limiting compression and fusion yield. Oscillations in the initial 200 ns of the current pulse are a possible cause of this disordering and we discuss possible mitigations. The impedance of the FF-1 and FF-2B devices at the pinch for both the 10cm and 14cm electrodes was correlated with the fusion yield. To obtain improved neutron yield with beryllium electrodes, we are reducing the inductance of the machine with a doubling of the number of switches.

Gridded inertial-electrostatic confinement (IEC) devices interest fusion researchers owing to their ability to burn advanced fusion fuels and have many near-term applications. In these devices, a high voltage (10-180 kV) accelerates ions radially between nearly transparent electrodes in spherical or cylindrical geometry. In this paper, we report experiments that study fusion reactions within the microchannels formed between the wires of the nearly transparent IEC cathode grid. Fusion proton counts were measured while sweeping the microchannels across a proton detector by rotating the central cathode grid with respect to the detector. The observed proton counts increased or decreased in correspondence with the grid wire orientation with respect to the proton detector. The fusion reactions were thus inferred to be nonuniform around the central grid and primarily occurring in channels formed by the grid wire gaps. We interpret this effect as an indication that most ions and charge-exchanged neutrals traverse radially along these microchannels. The grid wires will also shadow fusion reactions taking place at radii smaller than the cathode radius. Both the microchannels and the grid-wire shadowing causes the proton counts to vary, in measurements presented herein, by as much as 45%. We explore whether these effects could have played a role in previous research that reported potential-well structures.

This paper studies the profit efficiency of a sample of large U.S. commercial banks and explores how this performance varies with selected measures of bank risk reflecting aspects of credit risk, liquidity risk, and insolvency risk. We use a standard profit function and the stochastic frontier approach, and compare two standard functional forms – Cobb‐Douglas and translog – to assess the tradeoff between precision and parsimony. We find that profit efficiency is sensitive to credit risk and insolvency risk but not to liquidity risk or to the mix of loan products.

Supporters of the standard Big Bang theory point to the abundances of light elements, predicted by Big Bang Nucleosynthesis (BBN) as one of the main observational supports of the theory. However, current data no longer confirm BBN. Instead, measurements of the abundances of He3, He4, and D clearly contradict BBN at more than a 3σ level, eliminating a key support of the Big Bang.