Study of Electron Beams in Wire Arrays at 1-MA $Z$-Pinch Generators

We analyzed the characteristics of energetic electron beams produced by implosions of multiplanar wire arrays, nested cylindrical wire arrays (NCWAs), and compact cylindrical wire arrays (CCWAs), as well as X-pinches. In this paper, filtered soft and hard X-ray (HXR) diodes, spatially resolved time-integrated and time-gated spatially integrated LiF crystal spectrometers, and a Faraday cup were fielded to study the time evolution and spatial distribution of electron beams. Observed Faraday cup signals (electron cutoff energy, with EB from 42 to 250 keV) always coincide with HXR signals, and their pulse shape is similar to the shape of HXR pulses. The dependence of the total energy of the electron beam (Eb) on the wire material and the geometry of the wire-array load was studied. The electron-beam energies increase with the atomic number of the wire material. Aluminum tracer wires were found to decrease Eb in loads with Cu, Mo, or W wires. The intensity of cold K- and L-shell time-gated spectra correlate with corresponding amplitudes of HXR peaks and Faraday cup signals. The timing of correlation between the onset of energetic electron beams, HXR generation, and appearance of trailing mass for NCWAs and CCWAs is presented and discussed.