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Papers by Karnig Mikaelian

Physics of Plasmas, 2006

Radial profiles of nuclear burn in directly driven, inertial-confinement-fusion implosions have b... more Radial profiles of nuclear burn in directly driven, inertial-confinement-fusion implosions have been systematically studied for the first time using a proton emission imaging system sensitive to energetic 14.7MeV protons from the fusion of deuterium (D) and 3-helium (He3) at the OMEGA laser facility [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. Experimental parameters that were varied include capsule size, shell composition and thickness, gas fill pressure, and laser energy. Clear relationships have been identified between changes in a number of these parameters and changes in the size of the burn region, which we characterize here by the median “burn radius” Rburn containing half of the total DHe3 reactions. Different laser and capsule parameters resulted in burn radii varying from 20to80μm. For example, reducing the DHe3 fill pressure from 18to3.6atm in capsules with 20μm thick CH shells resulted in Rburn changing from 31to25μm; this reduction is attributed to increased fue...

We consider the photon-photon channel, gamma + gamma yields e/sup +/ + e/sup -/ + e/s up +/ + e/s... more We consider the photon-photon channel, gamma + gamma yields e/sup +/ + e/sup -/ + e/s up +/ + e/sup -/, with respect to the possible relevant experimental roles it plays in (i) the photoproduction process gamma + Z yields Z + e/sup +/ + e/sup -/ + e/sup +/ + e/sup -/, (ii) the colliding beam process e/sup plus or minus / + e/sup -/ yields e/sup plus or minus / + e/sup +/ + e/sup -/ + e/sup +/ + e/sup -/, and (iii) the absorption of high-energy cosmic photons. Discussion of the first role includes calculation of rates at different energies, enor estimates, and effects of screening and threshold cuts. In the second role, emphasis is placed on scale changes due to energy and angle kinematic cuts. Competition with the single-pair absorption process (i.e., gamma + gamma yields e/sup +/ + e/sup -/) at the higher cosmic gamma -ray e nergies ole. (auth)

APS Division of Plasma Physics Meeting Abstracts, Oct 1, 2001

ABSTRACT

Bulletin of the American Physical Society, 2019

Bulletin of the American Physical Society, 2016

We apply the Canuto-Goldman (CG) analytical model to turbulence generated by the class of instabi... more We apply the Canuto-Goldman (CG) analytical model to turbulence generated by the class of instabilities which have a power-law growth rate. For the case of Rayleigh-Taylor (RT) instability we compare the results of the model with the experiments of Read and Youngs and find reasonable agreement on the scale size of large eddies: they are predicted to be a0% of the mixing length and are at least an order of magnitude larger than the smallest eddies. We interpret this as chunk mix. Based on the experiments of Read and Yotmgs we develop a simple model for turbulence generated by Richtmyer-Meshkov (RIM) instabilities. The CG method applied to our model predicts that the relative sizes of large eddies and small eddies do not vary by more than 60%. We interpret this as atomic mix. Independently of the CG model we find that the ratio of turbulent to directed energy is about 2~ and 9% for RT and RM respectively, and varies as the square of the Atwood number in both cases.

Le Journal de Physique Colloques, 1974

Physical Review Fluids, 2016

Physikalisch Chemische Trenn Und Messmethoden, Nov 1, 1988

We have carried out a number of 2D numerical simulations on an ALE code for shock-tube experiment... more We have carried out a number of 2D numerical simulations on an ALE code for shock-tube experiments in which a shock crosses one or more contact discontinuities and, after traveling through a homogeneous medium, reflects off a rigid wall at the end of the shock-tube and re-crosses the contact discontinuity. We have considered two-fluid and three-fluid experiments: the first fluid, which carries the original shock, is air; the other fluids are helium, freon, SF/sub 6/, or air again. Helium is lighter than air, while freon and SF/sub 6/ are heavier than air. The interface(s) between the fluids serve as contact discontinuities and are subjected to the original shock, the re-shock, and subsequent rarefactions/compressions. 9 refs., 6 figs.