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Directly driven implosions at the Omega laser have tested the effects of pre-mix of Ar, Kr, and Xe in D 2 + 3 He filled glass micro-balloons. Diagnostics included: D+D and D+T neutron yields, D+ 3 He proton yields and spectra, Doppler broadened ion temperatures, time dependent neutron and proton burn rates, and time gated, high energy filtered, X-ray images. Yields are better calculated by XSN LTE than by non-LTE. Yields with a small amount of premix, atom fractions of ~5e-3 for Ar, 2e-3 Kr, and Xe for 5e-4, are more degraded than calculated, while the measured ion temperatures are the same as without pre-mix. There is also a decrease in fuel ρr. The neutron burn histories suggest that the early yield coming before the reflected shock strikes the incoming shell is un-degraded, with yield degradation occurring afterwards. Adding 20 atm % 3 He to pure D fuel seems to produce a similar degradation. Calculated gated X-ray images agree with observed when the reflected shock strikes the incoming shell, but are smaller than observed afterward. This partially explains yield degradation and both the low fuel and whole capsule ρr's observed in secondary T+D neutrons and slowing of the D+ 3 He protons. Neither LTE on non-LTE captures the degradation by 3 He or at low pre-mix levels, nor matches the large shell radii after impact of the reflected shock.

The yield of an inertial confinement fusion capsule can be greatly affected by the inclusion of high-Z material in the fuel, either intentionally as a diagnostic or from mixing due to hydrodynamic instabilities. To validate calculations of these conditions, glass shell targets filled with a D 2 and 3 He fuel mixture were fielded in experiments with controlled amounts of pre-mixed Ar, Kr, or Xe. The experiments were fielded at the OMEGA laser [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using 1.0 ns square laser pulses having a total energy 23 kJ and direct drive illumination of shells with an outer diameter of $925 lm and a thickness of $5 lm. Data were collected and compared to one-dimensional integrated models for yield and burn-temperature measurements. This paper presents a critical examination of the calculational assumptions used in our experimental modeling. A modified treatment of laser-capsule interaction improves the match to the measured scattered laser light and also improves agreement for yields, burn-temperatures, and the fuel compression as measured by the ratio of two yields. Remaining discrepancies between measurement and calculation will also be discussed. V C 2012 American Institute of Physics. [http://dx

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In order to maximize the K-line radiation from imploding gas puff loads driven by high current, pulsed power generators such as the DECADE Module 2 (DM2), initial puff diameters of 5-10 cm are required to provide implosion times of 200-300 ns. To date, such implosions have been found to produce lower-than-predicted yields. Lack of uniformity in the initial current flow through the neutral gas is offered as one of the possible reasons. If so, sufficient pre-ionization of the gas should mitigate this problem.A uv source was designed to pre-ionize a 7-cm diameter argon gas puff to be employed on the DM2 generator at Primex Physics International Company. The source is a 19-cm diameter cylinder consisting of two flashboards bent into semi-circles. The flashboard plasma is directed toward the axis of the cylinder which is co-linear with the axis of the gas nozzle. The plane of the flashboard is located 18 cm from the nozzle exit so that the ionizing uv is emitted at 60-80" angles and promptly illuminates the gas while the flashboard plasma arrives at the PRS load region about 4 ps later. The pre-ionization is measured absolutely using a high-sensitivity interferometer with which we can discriminate between phase shifts due to neutral argon and those due to free electrons as a function of space and time. Pre-ionization levels in the I-10% range were measured near the outer edge of the DM2 nozzle rendering this outer layer sufficiently conductive to carry the DM2 current.In addition to the DM2 application, it is anticipated that a version of this uv pre-ionization scheme will be utilized on neon gas puffs driven by the NRL Hawk generator.An innovative fusion scheme, embodying the principles of magnetized target fusion (MTF), in which the initial magnetized target and a plasma liner containing a cold fuel layer are introduced into the reactor vessel in a stand-off manner, is discussed. Two compact toroids containing fusionable materials are introduced into a spherical reactor target chamber in a diametrically opposing maimer. Embedded in the compact toroids are force-free magnetic fields in Woltjer-Wells-Taylor's state of minimum energy, which are known experimentally to be extraordinarily stable. They collide in the center to form an initial magnetized target plasma. A spherical distribution of plasma jets are then launched fiom the periphery of the vessel, coalescing to form a converging spherical plasma liner. On impact with the central plasma, the plasma liner sends a shock wave through it, shock heating it to some elevated temperature (above 100 eV) which sets the initial adiabat for subsequent compression. The high temperature immediately raises the electrical conductivity of the plasma to the extent that it traps the magnetic flux inside the central plasma. The central plasma is further compressed by the plasma liner and heated nearly adiabatically to conditions for thermonuclear burn, the magnetic flux being compressed with it. The thermal loss rate, greatly reduced by the high magnetic fields, are sufficiently lo...