Multispectral imaging of continuum emission for determination of temperature and density profiles inside implosion plasmas

In inertial confinement fusion experiments, implosion of a cryogenic hydrogen isotope-filled capsule produces a plasma with a high-temperature, low-density core (the hot spot) surrounded by a low-temperature, high-density main fuel layer. Experimental measurements of temperature and density profiles in the hot spot are critical for implosion diagnosis. In this paper, we propose a simple technique for measuring core temperature and density profiles in cryogenic implosion plasmas. This technique uses absolutely calibrated continuum emission spectroscopy coupled with two-dimensional imaging to allow temperature and density profiles to be measured directly. We develop the technique analytically, and validate it using synthetic data and hydrodynamics simulation results. We find that the technique should be sufficiently accurate to measure central temperatures and densities to better than 20%. The technique may also find application to the diagnosis of other types of plasmas.