Probing high areal-density cryogenic deuterium-tritium implosions using downscattered neutron spectra measured by the magnetic recoil spectrometer

For the first time high areal-density (ρ R) cryogenic deuterium-tritium (DT) implosions have been probed using downscattered neutron spectra measured with the magnetic recoil spectrometer (MRS) [J. A. Frenje, Rev. Sci. Instrum. 79, 10E502 (2008)], recently installed and commissioned on OMEGA [T. R. Boehly, Opt. Commun. 133, 495 (1997)]. The ρ R data obtained with the MRS have been essential for understanding how the fuel is assembled and for guiding the cryogenic program at the Laboratory for Laser Energetics (LLE) to ρ R values up to ∼300 mg/ cm². The ρ R data obtained from well-established charged particle spectrometry techniques [C. K. Li, Phys. Plasmas 8, 4902 (2001)] were used to authenticate the MRS data for low- ρ R plastic capsule implosions, and the ρ R values inferred from these techniques are in excellent agreement, indicating that the MRS technique provides high-fidelity data. Recent OMEGA-MRS data and Monte Carlo simulations have shown that the MRS on the NIF [G. H. Miller, Nucl. Fusion 44, S228 (2004)] will meet most of the absolute and relative requirements for determining ρ R, ion temperature (T_i) and neutron yield (Y_n) in both low-yield, tritium-rich, deuterium-lean, hydrogen-doped implosions and high-yield DT implosions.