Diagnosing ignition with DT reaction history

Wilson, D. C.; Bradley, P. A.; Cerjan, C. J.; Salmonson, J. D.; Spears, B. K.; Hatchet, S. P.; Herrmann, H. W.; Glebov, V. Yu.
October 2008
Review of Scientific Instruments;Oct2008, Vol. 79 Issue 10, p10E525
Academic Journal
A full range DT reaction history of an ignition capsule, from 109 to 1020 neutrons/ns, offers the opportunity to diagnose fuel conditions hundreds of picoseconds before and during burn. The burn history begins with a sharp rise when the first shock reaches the center of the capsule. The level of this jump reflects the combined shock strength and the adiabat of DT fuel. Changes to the four laser pulses driving the capsule implosion which are large enough to degrade the yield make measurable changes to the reaction history. Low mode asymmetries grow during convergence but change the reaction history during the final ∼100 ps. High mode asymmetry or turbulence mixing affects only the reaction history within ∼50 ps of peak burn rate. A capsule with a tritium fuel layer containing a small amount of deuterium (∼1%) creates a reaction history similar to the ignition capsule, but without the final ignition burn. A combination of gas Cerenkov detectors and the neutron temporal diagnostic could be capable of diagnosing the full history of ignition and tritium rich capsules.


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