Dynamic temperature measurements with embedded optical sensors.

This report summarizes LDRD project number 151365, %5CDynamic Temperature Measurements with Embedded Optical Sensors%22. The purpose of this project was to develop an optical sensor capable of detecting modest temperature states (<1000 K) with nanosecond time resolution, a recurring diagnostic need in dynamic compression experiments at the Sandia Z machine. Gold sensors were selected because the visible re ectance spectrum of gold varies strongly with temperature. A variety of static and dynamic measurements were performed to assess re ectance changes at di erent temperatures and pressures. Using a minimal optical model for gold, a plausible connection between static calibrations and dynamic measurements was found. With re nements to the model and diagnostic upgrades, embedded gold sensors seem capable of detecting minor (<50 K) temperature changes under dynamic compression

Optical properties of ultrafast laser heater solid

The regime of Warm Dense Matter (WDM) has emerged as an interdisciplinary field which has drawn broad interest from researchers in plasma physics, condensed matter physics, high pressure science, astrophysics, inertial confinement fusion, as well as material science under extreme conditions. Warm dense matter represents complex states at the convergence of condensed matter physics and plasma physics where neither conventional theoretical descriptions are valid. However, single-state experimental data for the direct testing of new theoretical models within this regime has been difficult to come by. To examine the WDM state, the optical properties of ultrafast laser heated solids were studied. Experiments were performed utilizing a femtosecond laser pump-probe technique to create and examine single-states of WDM. The isochoric heating of freestanding, ultrathin (30 nm), gold foils by a femtosecond pump laser produced uniform, solid-density states of energy densities from 0.25 to 20 MJ/kg. The AC conductivity of such states was determined from reflectivity and transmission measurements of a femtosecond probe as a direct benchmark for transport theory. In addition, observation of the time history of the probe reflectivity and transmission led to the discovery of a quasi-steady-state behavior of the heated sample that suggests the existence of a metastable, disordered phase prior to the disassembly of the solid. To further examine the dynamics of ultrafast laser heated solids, Frequency Domain Interferometry was used to provide an independent observation.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

Shock waves generated by intense femtosecond lasers

The advent of intense femtosecond lasers has created the exciting possibility of accessing regimes of extreme high pressure using a relatively small laser system. This stems from the lack of significant hydrodynamic expansion during the process of laser deposition in a solid via skin-depth absorption, which leads to extremely high energy densities in the irradiated sample. After the short-pulse laser energy has been absorbed, the laser-heated material begins to be released which drives a shock wave into the sample. However, unlike previous long-pulse laser driven shock waves, the shock wave driven by a intense short-pulse laser rapidly decays as it propagates through the sample. Before adopting such a shock wave as a new approach in the study of high density plasmas, its unique characteristics must be understood. A one-dimensional hydrodynamic code which is coupled to an electromagnetic wave solver is used to elucidate the basic properties of shock waves generated by intense femtosecond lasers. Using a unique experimental scheme, the electrical conductivity of silicon in the dense, plasma state can also be studied. Calculations were performed in which a shock wave was driven. into a silcion sample by a pump laser with a wavelength of 400 nm, pulse length of 120 fs (FWHM) and irradiances ranging from 10¹⁴ — 10¹⁵W/cm², while rear-side optical measurements were made by a 800 nm, 120 fs probe laser.Science, Faculty ofPhysics and Astronomy, Department ofGraduat

LIVA : a data reduction program for line-imaging ORVIS measurements.

LIVA (Line-Imaging Velocimetry Analysis) is a program for reducing data of a line-imaging optically recording velocity interferometer system (ORVIS) diagnostic. LIVA uses the Fourier transform method to extract phase information from recorded streak camera images. The extracted phase shift is used to infer target velocity as a function of space and time. The program can be run in any current version of MATLAB (2008a or later) or as a Windows XP executable

IWA : an analysis program for isentropic wave measurements.

IWA (Isentropic Wave Analysis) is a program for analyzing velocity profiles of isentropic compression experiments. IWA applies incremental impedance matching correction to measured velocity profiles to obtain in-situ particle velocity profiles for Lagrangian wave analysis. From the in-situ velocity profiles, material properties such as wave velocities, stress, strain, strain rate, and strength are calculated. The program can be run in any current version of MATLAB (2008a or later) or as a Windows XP executable

SIRHEN : a data reduction program for photonic Doppler velocimetry measurements.

SIRHEN (Sandia InfraRed HEtrodyne aNalysis) is a program for reducing data from photonic Doppler velocimetry (PDV) measurements. SIRHEN uses the short-time Fourier transform method to extract velocity information. The program can be run in MATLAB (2008b or later) or as a Windows executable. This report describes the new Sandia InfraRed HEtrodyne aNalysis program (SIRHEN; pronounced 'siren') that has been developed for efficient and robust analysis of PDV data. The program was designed for easy use within Sandia's dynamic compression community

Dynamic temperature measurements with embedded optical sensors.

This report summarizes LDRD project number 151365, %5CDynamic Temperature Measurements with Embedded Optical Sensors%22. The purpose of this project was to develop an optical sensor capable of detecting modest temperature states (<1000 K) with nanosecond time resolution, a recurring diagnostic need in dynamic compression experiments at the Sandia Z machine. Gold sensors were selected because the visible re ectance spectrum of gold varies strongly with temperature. A variety of static and dynamic measurements were performed to assess re ectance changes at di erent temperatures and pressures. Using a minimal optical model for gold, a plausible connection between static calibrations and dynamic measurements was found. With re nements to the model and diagnostic upgrades, embedded gold sensors seem capable of detecting minor (<50 K) temperature changes under dynamic compression

A new Augmin subunit, Msd1, demonstrates the importance of mitotic spindle-templated microtubule nucleation in the absence of functioning centrosomes

The Drosophila Augmin complex localizes γ-tubulin to the microtubules of the mitotic spindle, regulating the density of spindle microtubules in tissue culture cells. Here, we identify the microtubule-associated protein Msd1 as a new component of the Augmin complex and demonstrate directly that it is required for nucleation of microtubules from within the mitotic spindle. Although Msd1 is necessary for embryonic syncytial mitoses, flies possessing a mutation in msd1 are viable. Importantly, however, in the absence of centrosomes, microtubule nucleation from within the spindle becomes essential. Thus, the Augmin complex has a crucial role in the development of the fly