Achim Seifter

TRIDENT high-energy-density facility experimental capabilities and diagnostics

The newly upgraded TRIDENT high-energy-density (HED) facility provides high-energy short-pulse laser-matter interactions with powers in excess of 200 TW and energies greater than 120 J. In addition, TRIDENT retains two long-pulse (nanoseconds to microseconds) beams that are available for simultaneous use in either the same experiment or a separate one. The facilitys flexibility is enhanced by the presence of two separate target chambers with a third undergoing commissioning. This capability allows the experimental configuration to be optimized by choosing the chamber with the most advantageous geometry and features. The TRIDENT facility also provides a wide range of standard instruments including optical, x-ray, and particle diagnostics. In addition, one chamber has a 10 in. manipulator allowing OMEGA and National Ignition Facility (NIF) diagnostics to be prototyped and calibrated.

Different methods of reconstructing spectra from filtered x-ray diode measurements.

Filtered x-ray diodes, sensitive in different spectral regions, are used to measure the emission spectrum of laser-driven hohlraums at the Omega laser facility in Rochester, NY. Here we present two new methods to reconstruct the emission spectra from the response of the x-ray diodes and compare them to the method currently used to extract a spectrum and a temperature in the hohlraum. We also use simulated spectra to characterize the different methods with respect to uncertainty, emission temperature, and the ability to reconstruct the input spectrum as closely as possible.

Tuning indirect-drive implosions using cone power balance

We demonstrate indirect-drive implosion symmetry tuning in a vacuum hohlraum 6.6 mm in length and 3.56 mm in diameter with a CH capsule 6.38 μm in thickness and 1414 μm in diameter, scaled roughly 0.7 × from a National ignition facility (NIF) [E. Moses and C. R. Wuest, Fusion Sci. Technol. 47, 314 (2005)] The hohlraums have radiation drives of 117 ± 4 eV relevant to conditions for the first ∼1 ns of ignition experiments. By varying the relative ratio of the energy between inner and outer beam cones illuminating the hohlraum at OMEGA [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. the shape of the x-ray self-emission, and hence the shape of the emitting object, can be tuned from prolate to oblate. The second-order Legendre coefficient, used to characterize the shape, changes from a negative to a positive value at the time of peak x-ray emission during the implosion through the variation of the cone power balance. With the appropriate selection of the cone power balance, the implosion can be tuned to p...

Explanation for Anomalous Shock Temperatures Measured by Neutron Resonance Spectroscopy

Neutron resonance spectrometry (NRS) has been used to measure the temperature inside Mo samples during shock loading. The temperatures obtained were significantly higher than predicted assuming ideal hydrodynamic loading, a discrepancy which we now explain. The effects of plastic flow and nonideal projectile behavior were assessed. Plastic flow was calculated self-consistently with the shock jump conditions: this is necessary for a rigorous estimate of the locus of shock states accessible. Plastic flow was estimated to contribute a temperature rise of 53 K compared with hydrodynamic flow. Simulations were performed of the operation of the explosively driven projectile system used to induce the shock in the Mo sample. The simulations, and related experiments, indicated that the projectile was significantly curved on impact, and still accelerating. The resulting spatial variations in load, including radial components of velocity, should increase the apparent temperature that would be deduced from the width of the neutron resonance by 160 K. These corrections are sufficient to reconcile the apparent temperatures deduced using NRS with the accepted properties of Mo, in particular, its equation of state.

Pyrometric measurement of the temperature of shocked molybdenum

Measurements of the temperature of Mo shocked to

Post‐Shock Temperature Measurements of Aluminum

\ensuremath{\sim}60\text{ }\text{GPa}

Shock and release temperatures in molybdenum : Experiment and theory

and then released to

Normal spectral emissivity near 680 nm at melting and in the liquid phase for 18 metallic elements

\ensuremath{\sim}28\text{ }\text{GPa}

Post‐Shock Temperature and Free Surface Velocity Measurements of Basalt

were previously attempted by using high explosive driven flyer plates and pyrometry. The analysis of the radiance traces at different wavelengths indicates that the temporal evolution of the radiance can be explained by a contribution from the LiF window to the measured thermal radiation. By fitting the radiance traces with a simple model, which is supported by continuum dynamics studies, which were able to relate structures in the radiance history to hydrodynamic events in the experiment, the contribution of the window, and hence the temperature of the Mo sample, was obtained. The shock and release temperature obtained in the Mo was

A high-speed, four-wavelength infrared pyrometer for low temperature shock physics experiments

762\ifmmode\pm\else\textpm\fi{}40\text{ }\text{K}