Abstract
Ion emission angular distribution mechanisms in plasma focus devices (PFD) have not yet been well developed and understood being due to the lack of an efficient wide-angle ion distribution image detection system to characterize a PFD space in detail. Present belief is that the acceleration of ions points from “anode top” upwards in forward direction within a small solid angle. A breakthrough is reported in this study, by mega-size position-sensitive polycarbonate ion image detection systems invented, on discovery of 4π ion emission from the “anode top” in a PFD space after plasma pinch instability and radial run-away of ions from the “anode cathodes array” during axial acceleration of plasma sheaths before the radial phase. These two ion emission source mechanisms behave respectively as a “Point Ion Source” and a “Line Ion Source” forming “Ion Cathode Shadows” on mega-size detectors. We believe that the inventions and discoveries made here will open new horizons for advanced ion emission studies towards better mechanisms understanding and in particular will promote efficient applications of PFDs in medicine, science and technology.
Highlights
Even in far off-axis positions and the ions with energies lower than 300 keV are distributed widely over the emission angle of ±80°, while the higher-energy protons (>1 MeV) are confined in the half cone angle of ±30° 38
In order to characterize this “hypothesis” by real wide-angle measurements and analysis in 4πPFD space, it was the purpose of this study to: 1. develop and apply position-sensitive mega-size PC (MSPC) ion image detectors processed by mega-size electrochemical etching (ECE) (MS-ECE) chamber systems for 4πion emission angular distribution image studies in a plasma focus device (PFD) space, 2. study and verify sources of ion emissions from the “anode top” and the “anode electrodes array” in 4πPFD space, and
The breakthrough and discoveries made in this study resolve the shortcomings and limitations of presently available detectors and reveal facts towards better understanding of ion emission and angular distributions in 4πPFD space
Summary
Even in far off-axis positions and the ions with energies lower than 300 keV are distributed widely over the emission angle of ±80°, while the higher-energy protons (>1 MeV) are confined in the half cone angle of ±30° 38. The detectors usually used in such studies include activation detectors[7,41], magnetic analyzers[42], Faraday cups (FC)[25,28,43], Thomson spectrometer[44] and in particular polymer track detectors like CR-39 (polyallyl-diglycol-carbonate film), PM-355 (super-grade polyallyl-diglycol-carbonate film), CN (cellulose nitrate film) and LR-115 (red-dyed cellulose nitrate film) These polymer detectors can register tracks of ions such as protons, deuterons, alpha particles or heavier ions usually by a chemical etching process followed by microscopic observation and counting[7,16,18,27,45]. The rationale for the limitations in observing ion emission angular distributions in a wider-angle PFD space and in turn better mechanism understanding has been the lack of an ion angular distribution image detection system with a potential to provide wide-angle position-sensitive matrix data under single pinch shots. Develop and apply position-sensitive MSPC ion image detectors processed by mega-size ECE (MS-ECE) chamber systems for 4πion emission angular distribution image studies in a PFD space, 2. 3. explore other relevant phenomena with an aim to enhance better understanding of the mechanisms involved and last but not least to promote efficient advanced applications of PFD space in medicine, science and technology
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