20 research outputs found
The interaction of intense subpicosecond laser pulses with underdense plasmas
Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered
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Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator
The advent of the 20-MA Z accelerator [R.B. Spielman, C. Deeney, G.A. Chandler, et al., Phys. Plasmas 5, 2105, (1997)] has enabled implosions of large diameter, high-wire-number arrays of titanium to begin testing Z-pinch K-shell scaling theories. The 2-cm long titanium arrays, which were mounted on a 40-mm diameter, produced between 75{+-}15 to 125{+-}20 kJ of K-shell x-rays. Mass scans indicate that, as predicted, higher velocity implosions in the series produced higher x-ray yields. Spectroscopic analyses indicate that these high velocity implosions achieved peak electron temperatures from 2.7{+-}0.1 to 3.2{+-}0.2 keV and obtained a K-shell emission mass participation of up to 12%
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The interaction of intense subpicosecond laser pulses with underdense plasmas
Laser-plasma interactions have been of interest for many years not only from a basic physics standpoint, but also for their relevance to numerous applications. Advances in laser technology in recent years have resulted in compact laser systems capable of generating (psec), 10{sup 16} W/cm{sup 2} laser pulses. These lasers have provided a new regime in which to study laser-plasma interactions, a regime characterized by L{sub plasma} {ge} 2L{sub Rayleigh} > c{tau}. The goal of this dissertation is to experimentally characterize the interaction of a short pulse, high intensity laser with an underdense plasma (n{sub o} {le} 0.05n{sub cr}). Specifically, the parametric instability known as stimulated Raman scatter (SRS) is investigated to determine its behavior when driven by a short, intense laser pulse. Both the forward Raman scatter instability and backscattered Raman instability are studied. The coupled partial differential equations which describe the growth of SRS are reviewed and solved for typical experimental laser and plasma parameters. This solution shows the growth of the waves (electron plasma and scattered light) generated via stimulated Raman scatter. The dispersion relation is also derived and solved for experimentally accessible parameters. The solution of the dispersion relation is used to predict where (in k-space) and at what frequency (in {omega}-space) the instability will grow. Both the nonrelativistic and relativistic regimes of the instability are considered
Absolute X-ray yields from laser-irradiated, Ge-doped aerogel targets
We have measured the production of  10 keV x rays from
low-density, Ge-doped aerogel targets at the OMEGA laser (Laboratory
for Laser Energetics, University of Rochester). The targets were 1.2mm long by 1.5mm diameter beryllium cylinders filled with Ge-doped (20 atomic percent) SiO aerogel. The doped-aerogel density was 4.8 or 6.5Â mg/cm. Forty beams of the OMEGA laser ( = 351Â nm) illuminated the two cylindrical faces of the target with a total power of 18Â TW. Ge K-shell x-ray emission was spectrally resolved with a two-channel crystal spectrometer and recorded with temporal resolution with a set of calibrated photoconductive devices (PCDs)
Assessing the ZR Machine's Potential for Producing Multi-keV X-Ray Yields in K-Shell Line and Free-Bound Continuum Radiation
Radiation properties and implosion dynamics of planar and cylindrical wire arrays, asymmetric and symmetric, uniform and combined X-pinches on the UNR 1-MA zebra generator
Ultraintense Electromagnetic Radiation in Plasmas: Part II. Relativistic Electromagnetic Solitons and Laser-Driven Ion Acceleration
Alirocumab in Patients With Polyvascular Disease and Recent Acute Coronary Syndrome ODYSSEY OUTCOMES Trial
Cardiolog