2024/08/09 by Ryan, R. A., Tsai, P. E., Johansen, A. R. +7 · 2 citations
#FOS: Physical sciences #Nuclear Experiment (nucl-ex) #Plasma Physics (physics.plasm-ph)
paper · doi:10.48550/arxiv.2408.05171
Previous measurements of neutron energy using fast plastic scintillators while operating the Fusion Z Pinch Experiment (FuZE) constrained the energy of any yield-producing deuteron beams to less than 4.65 keV. FuZE has since been operated at increasingly higher input power, resulting in increased plasma current and larger fusion neutron yields. A detailed experimental study of the neutron energy isotropy in these regimes applies more stringent limits to possible contributions from beam-target fusion. The FuZE device operated at -25~kV charge voltage has resulted in average plasma currents of 370~kA and D-D fusion neutron yields of 4×107 neutrons per discharge. Measurements of the neutron energy isotropy under these operating conditions demonstrates the energy of deuteron beams is less than 7.4 ± 5.6^(stat) ± 3.7^(syst)~keV. Characterization of the detector response has reduced the number of free parameters in the fit of the neutron energy distribution, improving the confidence in the forward-fit method. Gamma backgrounds have been measured and the impact of these contributions on the isotropy results have been studied. Additionally, a time dependent measurement of the isotropy has been resolved for the first time, indicating increases to possible deuteron beam energies at late times. This suggests the possible growth of m=0 instabilities at the end of the main radiation event but confirms that the majority of the neutron production exhibits isotropy consistent with thermonuclear origin.