Plasma Performance of the Central Cell of a Cat-D Tandem Mirror Reactor
A particle and power balance assessment of the central cell of a conceptual D-D tandem mirror reactor (TMR) is carried out using a two-dimensional (2-D) Fokker-Planck code and a zero-dimensional (0-D) simulation code. The two computational models produce excellent agreement except for the mean triton energy, the difference in which can be attributed to the fact that the 2-D code considers the long slowing-down time of the tritium. It is demonstrated that for an ion confining potential between 200 and 300 keV, a) the central cell of a catalyzed-deuterium (Cat-D) fueled TMR can achieve ignition in the temperature range of 40-60 keV, b) the alpha ash buildup must be strictly controlled to obtain an economical ratio of electrostatic confining potential to central-cell temperature ¿/T, allowing the exhaust tritium to beta decay to helium-3 prior to reinjection results in roughly the same net electrical power output, and c) injecting extra tritium beyond that bred in the plasma allows a drop in the minimum ion confining potential required for ignition. It is shown that the ion confining potential is minimized when Tic, = 50 keV; this results in a plasma Q of 26. A quantitative comparison with a D-T reactor scenario is presented. It is shown that under ideal operating conditions, a conceptual Cat-D TMR has a 35-40 percent higher power conversion efficiency than a D-T device; this must be weighed against the higher temperature and plugging requirements of Cat-D.
Multi-species Fokker-Planck calculations for D-T and D-3He mirror reactors
Values of the confinement parameter ntau and the figure of merit Q (the ratio of thermonuclear power to injected power) are obtained for postulated reactor conditions. The heart of the work is the numerical solution, under tested assumptions, of the coupled Fokker-Planck equations for as many as six charged species. A study is made of D-T and D-3He fuel cycles, including reaction products, in the following parameter ranges: mirror ratio, 2<or=Rm<10; injection energy, 50 keV<or=E0<or=1500 keV; equilibrium 3He fraction for the D-3He cycle, 0.05<or=fHe<or=0.35. The computed Q's fall in the ranges 0.5<QDT<1.5, 0.1<QDHe<0.3. The present results are compared with previous work, with analytical/empirical approximations, and with a separate code treating velocity space more rigorously for a single positive species.
Geomagnetic Polarity Epochs: Sierra Nevada Data, 3
Available paleomagnetic and radiometric results for about 60 igneous rocks 3.6 m.y. old or less are consistent with the following geomagnetic polarity epoch time scale: Brunhes normal polarity epoch, 0.0 to 0.85±0.15 million years; Matuyama reversed polarity epoch, 0.85±0.15 to 2.4±0.1 million years; Gauss normal polarity epoch, 2.4±0.1 to 3.35±0.1 million years; Gilbert reversed polarity epoch, 3.35±0.1 million years to (?). A brief interval of normal polarity (the Olduvai event) occurs within the Matuyama reversed epoch at about 1.9 m.y., and a brief interval of reversed polarity (the Mammoth event) occurs within the Gauss normal epoch at about 3.06 m.y. Data for twelve units from eastern California and Nevada, reported here for the first time, are particularly useful in defining the Gauss-Gilbert boundary and for recognizing the Mammoth event.