Diagnosing ablator ρR and ρR asymmetries in capsule implosions using charged-particle spectrometry at the National Ignition Facility

Abstract

By fielding several compact proton spectrometers at various locations around an ignition-capsule implosion at the National Ignition Facility [G. H. Miller, E. I. Moses, and C. R. Wuest, Nucl. Fusion 44, S228 (2004)], ρR and ρR asymmetries of the ablator for a failed implosion can be obtained through absolute measurements of knock-on proton (KO-P) spectra. For ignition capsules with a Cu-doped beryllium (Be) ablator, 50:50 mixture of deuterium-tritium (DT) fuel and ∼1% residual hydrogen (H) by atom, failed implosions can be diagnosed for neutron yields ranging from ∼1011 to ∼6×1015 and local ρRs up to ∼240mg∕cm2. For capsules with an ablator of Ge-doped CH, which contains a large amounts of H, failed implosions can be diagnosed for neutron yields ranging from ∼1010 to ∼6×1015 and local ρRs up to ∼200mg∕cm2. Prior to the first ignition experiments, capsules with a Cu-doped Be ablator (or Ge-doped CH ablator), more deuterium-lean fuel mixture and H-dopant levels up to 25% in the fuel will be imploded to prim...