This week, Aidan Crilly (ICL) is going to tell us about some of his recent work The details of his talk are given below. The seminar will be given in B741 at the normal time, 3 PM on Wednesday 9th March. It will also be streamed on Teams here for those joining remotely.
Looking forward to seeing you there!
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Neutron backscatter edges – a novel diagnostic for shell dynamics and propagating burn in Inertial Confinement Fusion
Observations during the stagnation of ICF implosions are primarily focused towards diagnosing the hotspot, with the cold dense fuel shell properties largely unmeasured. Efficient energy conversion between the kinetic energy of the shell and the internal energy of the hotspot is a key requirement for ignition. Residual kinetic and excess internal energy in the shell are energy sinks which will prevent ignition. Propagation of thermonuclear burn into the shell is required for high energy gains. Direct measurement of the energy content of the shell is therefore critically important to the understanding of implosion performance.
Observations during the stagnation of ICF implosions are primarily focused towards diagnosing the hotspot, with the cold dense fuel shell properties largely unmeasured. Efficient energy conversion between the kinetic energy of the shell and the internal energy of the hotspot is a key requirement for ignition. Residual kinetic and excess internal energy in the shell are energy sinks which will prevent ignition. Propagation of thermonuclear burn into the shell is required for high energy gains. Direct measurement of the energy content of the shell is therefore critically important to the understanding of implosion performance.
The scattered neutron spectrum emitted from an ICF implosion contains a wealth of information about the dense fuel. Neutrons which undergo a single 180° scattering event from D and T ions produce sharp edges in the spectrum. The spectral shapes of the backscatter edges are especially sensitive to the ion velocity distribution. Similar to the DT primary spectrum, thermal and non-thermal broadening and fluid velocity Doppler shifts govern the spectral shape of the backscatter edge. Thus, the backscatter edges provide a unique diagnostic feature to measure the hydrodynamic conditions of the dense fuel at stagnation. We develop and use a model of the backscatter edge spectra to study shell dynamics in OMEGA direct drive experiments and burn propagation in high yield NIF experiments.