Fuel areal density () measurements using secondary and tertiary reaction for ICF targets

Summary form only given, as follows. In order to achieve ignition in an ICF target, the fuel areal density must be sufficiently high that a significant fraction of the energy of fusion produced alpha particles is deposited in the fuel. Therefore, characterizing areal density is to determine the quality of an implosion. Currently in ICF experiments at the Nova Laser Facility, fuel areal density is measured using the "secondary neutron technique". This technique relies upon the observation of 12-17 MeV neutrons produced via the D(T,n)/sup 4/He reaction in an initially pure deuterium fuel, where the 1.01 MeV reacting triton is produced from the /sup 2/H(/sup 2/H,/sup 1/H)/sup 1/H and D(D,p)T primary reactions. At the proposed National Ignition Facility, the higher anticipated areal densities should slow the triton completely rendering this technique ineffective. Here the possibility of using "tertiary reaction neutrons" is discussed. This technique has the potential of measuring fuel areal densities of 100-300 mg/cm/sup 2/, well beyond the secondary limit of 30 mg/cc. Details of the instrument used to measure secondary neutron spectra, experimental results and potential application to the measurement of tertiary neutrons are presented.