Spatially resolved EUV emission from focused REB discharges into thin targets

摘要

The EUV emission from 10‐ to 100‐mg/cm2‐thick planar targets (Z=6–79) exposed to 60‐nsec‐duration focused relativistic electron beams was examined at current densities of 0.4–1.0 MA/cm2. Spatially resolved spectra were obtained with a stigmatic near‐normal incidence spectrograph, in the wavelength range 500–2100 Å, along axial and radial directions. Time‐resolved EUV data were obtained with windowless photoelectric diodes operated unfiltered and filtered with 0.5‐μm‐thick aluminum. The axial views show copious emission from the diode gap associated with late‐time impedance collapse. Radial views show continuum radiation which is emitted from the region of the target exposed to the focused REB and line radiation which originates from a lower‐density (approximately 1019 cm-3) more‐extended late‐time plasma resulting from foil expansion. The region of the foil exposed to the focused REB radiates as a blackbody source with a peak temperature of 2–6 eV. These temperatures are a factor of 2 below the calculated temperatures for classical deposition in the foils exposed to the focused beam assuming no hydrodynamic foil expansion.