Impurities produced by the vaporization of metals in the electrodes may be a major cause of reduced fusion yields in high-current dense plasma focus devices. We propose here that a major, but hitherto-overlooked, cause of such impurities is vaporization by runaway electrons during the breakdown process at the beginning of the current pulse. This process is sufficient to account for the large amount of erosion observed in many dense plasma focus devices on the anode very near to the insulator. The erosion is expected to become worse with lower pressures, typical of machines with large electrode radii, and would explain the plateauing of fusion yield observed in such machines at higher peak currents. Such runaway electron vaporization can be eliminated by the proper choice of electrode material, by reducing electrode radii and thus increasing fill gas pressure, or by using pre-ionization to eliminate the large fields that create runaway electrons. If these steps are combined with monolithic electrodes to eliminate arcing erosion, large reductions in impurities and large increases in fusion yield may be obtained, as the I4 scaling is extended to higher currents.
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October 2014
Research Article|
October 22 2014
Runaway electrons as a source of impurity and reduced fusion yield in the dense plasma focus
Eric J. Lerner;
Eric J. Lerner
LPPFusion, Inc.
, 128 Lincoln Blvd., Middlesex, New Jersey 08846, USA
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Hamid R. Yousefi
Hamid R. Yousefi
LPPFusion, Inc.
, 128 Lincoln Blvd., Middlesex, New Jersey 08846, USA
Search for other works by this author on:
Phys. Plasmas 21, 102706 (2014)
Article history
Received:
September 23 2014
Accepted:
October 05 2014
Citation
Eric J. Lerner, Hamid R. Yousefi; Runaway electrons as a source of impurity and reduced fusion yield in the dense plasma focus. Phys. Plasmas 1 October 2014; 21 (10): 102706. https://doi.org/10.1063/1.4898733
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