No abstract

Tertiary protons with birth energies from 27 to 30.8 MeV result from the implosion of ignition-scale inertial confinement fusion targets, such as those planned for the National Ignition Facility (NIF). Measurement of the tertiaries' slowing can provide a determination of the imploded areal density of the fuel capsule, as well as information about implosion asymmetry that results from anisotropy of the areal density and plasma temperature. To determine the utility of tertiaries for all phases of ignition experiments, we analyze three representative cases: a gas capsule (0.7 kJ yield); a cryogenic fuel capsule that fails to ignite (15 kJ); and a cryogenic fuel capsule that ignites and burns (13,000 kJ). In each case, tertiaries escape from the capsule and convey critical information about implosion dynamics. Tertiaries might also prove useful for current laser facilities such as the newly completed OMEGA. France. The goal is to generate at least 10 times more energy from fusion than the laser energy (51.8 MegaJoule) used to drive the capsule implosions. In such experiments, densities and areal densities will be immense (~ 10 g/cm 3 and -1 g/cm 2 ). Precisely because of such extremes (see Fig. 1-3), new diagnostic methods will be required to measure critical parameters such as capsule implosion symmetry'," and areal density 9 -2 .Here we identify a solution to these particular issues based on detection of teritary protons that have birth energies between -27 and 30.8 MeV. We concentrate on these high-energy tertiaries both because of their ability to escape the capsules envisioned for all phases of the NIF and because they convey pivotal information.Diagnosis of tertiary protons will be useful during three phases of the approach to ignition. In the first phase, conditions for symmetric drive will be established using nonigniting DT gas-filled capsules, with small fusion yields (0.7 kJ). In the second phase, the drive pulse-shape for igniting cryogenic (solid fuel) capsules will be determined, as well as further fine-tuning of drive symmetry. Ignition itself will not yet be achieved, but the yields will typically be much larger (15 kJ) than for gas capsules. In the final stage, fully ignited cryogenic capsules with large yields (13,000 kJ) will be diagnosed. Below we analyze the tertiary production and spectra from each of these cases. In addition to these considerations of the NIF implosions, we briefly examine the potential utility of tertiary protons for current laser experiments such as the recently-completed OMEGA.High-energy tertiary protons are generated in a 3-step process starting with the primary fusion between deuterium (D) and tritium (T) ionswhere the short range of the a particles propagates the fusion burn from the igniting core outwards into the dense fuel region". The second step involves the 14.1-MeV neutron elastically scattering off a plasma deuteron:(2) n(14.1MeV) + D ------------> n' + D( 11 ----12.5 MeV). (12.5)MeV corresponds to a collision in which the deuteron scatters at 20 (0) deg...

No abstract

No abstract

No abstract