Absolute calibration of the continuum x-ray spectrometer (ConSpec) at the National Ignition Facility

Abstract

We present the absolute calibration of the continuum x-ray spectrometer (ConSpec), designed to measure the hot-spot electron temperature of inertial confinement fusion (ICF) implosions at the National Ignition Facility (NIF). The spectrometer measures emission from photon energies of 20 to 30 keV where opacity effects in ICF implosions at the NIF are negligible and provides spatial resolution to separate the hot-spot emission from other x-ray sources, such as the gold emission from the hohlraum wall. Using a combination of x-ray ray tracing and calibration data taken using a well characterized x-ray source, we measure the dispersion, spatial resolution, and absolute sensitivity of the instrument. Finally, we present an example spectrum measured at the NIF and demonstrate the ability to measure the hot-spot electron temperature with uncertainty under 10%.