Space, Time, and Energy Distributions of Neutrons and X Rays from a Focused Plasma Discharge

Abstract

The energy spectrum and spatial distribution of neutrons emitted by a plasma focus device were measured with nuclear emulsions and scintillation detectors, and the results are reported. The average energy of the D‐D neutrons emitted along the axis was shifted $\text{∼500\hspace{0.17em}keV}$ corresponding to an axial center‐of‐mass velocity of ${\text{2\hspace{0.17em}×\hspace{0.17em}10}}^8\hspace{0.17em}\mathrm{cm}/\sec$ for the reacting deuterons. An 11% anisotropy in the neutron fluxes measured in the forward and radial directions correlates with an axially streaming plasma which is not isotropic; the reacting deuterons collide predominantly in the radial direction. Time‐resolved collimation measurements of the emitted neutrons showed an axial translation of the neutron source corresponding to velocities up to ${\text{2\hspace{0.17em}×\hspace{0.17em}10}}^8\hspace{0.17em}\mathrm{cm}/\sec$ ; this correlates with the nonsimultaneous pinching of the noncylindrical plasma along the axis. Plasma densities of ${\text{∼\hspace{0.17em}2\hspace{0.17em}×\hspace{0.17em}10}}^{20}{\mathrm{cm}}^{\text{−3}}$ and ion temperatures of 2 keV were consistent with observed neutron yields of ${10}^{10}$ and pulse widths of 60 nsec. X‐ray intensity measurements were made for x‐ray energies of ${\text{7\hspace{0.17em}<\hspace{0.17em}E}}_p\text{\hspace{0.17em}<\hspace{0.17em}30\hspace{0.17em}keV}$ and showed an $E_p^{\text{−2}}$ dependence which does not agree with plasma bremsstrahlung, but appears to result from anode bombardment of axially accelerated electrons with energies $\text{>\hspace{0.17em}200\hspace{0.17em}keV}$ . The line radiation corresponded to that of fairly cold ions.