Measurement and Analysis of Continuum Radiation From a Large-Diameter Long Implosion Time Argon Gas Puff$Z$-Pinch at 6 MA

Time-resolved measurements of the absolute free-bound (FB) continuum spectrum emitted from a 12-cm-diameter argon gas-puff
$Z$
-pinch driven at
$sim!!6$
-MA peak current with 220- to 260-ns implosion times are reported. A crystal spectrometer is used with silicon diode detectors to provide kiloelectronvolt spectral resolution. The energy and absolute-intensity calibration procedures for the spectrometer are described. The slope of the FB continuum is well represented by a decaying exponential spectrum with a single electron temperature from which spatially averaged, time-resolved
$(T_e(t))$
, and time-integrated
$(langle T_erangle)$
electron temperatures are inferred. An expression for the absolute FB continuum, which takes into account recombination onto bare as well as H-like species, is presented and used to infer time-integrated spatially averaged ion densities
$langle n_irangle$
. The values of
$langle T_erangle$
and
$langle n_irangle$
are in general agreement with the values of these quantities obtained by using the conventional K-shell line-ratio method. Values of
$T_e(t)$
peak on the rise of the continuum radiation pulse and gradually decrease during the pulse. The fraction of the total energy radiated in the K-shell that resides in the FB continuum is 6%–10%, and this fraction increases with
$langle n_irangle$
. Calculated continuum spectra are in agreement with measured spectra.