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Summary form only given. The channel-guided, standard laser wakefield accelerator (CGS-LWFA) is a laser-driven plasma-based accelerator concept that has the potential to produce high quality accelerated electron bunches over extremely short acceleration distances. Operation in the short pulse or "standard" regime would provide strong, stable accelerating fields, and the use of a plasma channel...
Summary form only given. At Utsunomiya University, the radiation generation experiments and the laser guiding experiments with capillary discharge plasma using a short and ultra high intense laser (1 TW/100 fs) have been carried out. When the laser is tightly focused in the neutral gas, we observe the strong radiation in the microwave regime. The radiation generated from the focal region is strongly...
Summary form only given. Laser driven accelerators such as the laser wakefield accelerator (LWFA) have tremendous advantages over conventional radio-frequency accelerators because of the ultra-high acceleration gradients (>100 GV/m) provided by the large amplitude relativistic plasma waves that are excited by the intense ultra-short laser pulse. These ultra-high gradients were demonstrated in the...
Summary form only given. Applications of laser beams in many instances require a well-defined, tight focus, with high intensity. In other cases, especially in directed energy applications, it is necessary for the laser beam to propagate long distances. These two requirements are interrelated and are affected by the laser beam quality as measured by, for example, M-squared. For steady state propagation...
Summary form only given. We present a series of measured spectra, 200 nm-1090 nm with 1 nm resolution, for various target materials including: Al, Ti, Au, Si, Cu and Al coated Ti obtained during laser-solid interaction experiments performed at the ultra-intense short pulse laser facilities JanUSP (LLNL), Comet (LLNL) and Vulcan (RAL). Laser intensities ranged from moderately relativistic, ~1018 W/cm...
Summary form only given. Experimental data of electron energy distributions from ultra-intense (>1019 W/cm2) laser-solid interactions using a petawatt laser containing >300 Joules are presented. Clear signatures for the existence of three populations of energetic electrons, all with distinct effective temperatures, are seen in the spectra. We present simulations and theoretical calculations...
We investigate electron transport and ionization dynamics in solid targets driven by ultra-short intense laser pulses, i.e. with intensities I>1017 W/cm2 and pulse durations below 1 ps theoretically. Using multi-dimensional particle-in-cell models that include field- and electron impact ionization, as well as binary collisions between charged particles, we study the propagation of an electron beam-driven...
Summary form only given. The transversely coherent soft X-ray radiation with quasi-Gaussian intensity distribution and angle divergence of ~0.5 mrad was recently generated by a plasma-based waveguide Ar+8 laser with excitation by a slow (~200 ns) non-ablative Z-pinch discharge in a long (~0.5 m) ceramic capillary. In the present study, we present results of further experimental optimization of the...
Summary form only given. In the presence of non-ideal effects global MHD modes excited due to development of interchange type instabilities can have both an imaginary part of frequency (purely growing modes), and finite real frequency in the excited wave spectrum. This in turn can lead to significant changes in the non-linear processes which are responsible for the spectral wave energy transfer, convective...
Summary form only given. PRS implosion kinematics depend on the load current's time-dependent spatial distribution and magnitude. Time-dependent axial shunting of the load current to the return current posts can contribute to non-optimum assembly of the pinch on-axis, reducing the ideally achievable K-shell yield. The presence of plasma and the harsh environment in the PRS load region typically make...
Summary form only given. MHD modeling of plasma implosion in wire arrays is the part of the integrated theoretical study of the dynamics of high energy and density plasmas, created by X-pinch, wire array and single wire explosion discharges at the University of Nevada Reno. Together with the X-ray spectroscopic measurements and modeling and with optical plasma diagnostic this study reveals the important...
Summary form only given. Recent experimental data demonstrate that wire array loads (a) radiate more energy than could be coupled to them via a change of inductance, and (b) start radiating before the main mass stagnates on the axis. This indicates that the wire array plasma operates as a resistive rather than an inductive load. Recently it was suggested that it may be because of the wire array plasma...
Summary form only given. A Faraday rotation diagnostic was developed at the Nevada Terawatt Facility (NTF) for investigation of magnetic fields in plasma from 1-MA wire arrays and X-pinches. Optical diagnostics at the NTF includes a four-channel polaro-interferometer and four-frame shadowgraphy. The polaro-interferometer consists of identical shadow and Faraday channels, shearing air-wedge interferometer,...
Summary form only given. Z pinches are a well established method to produce pulsed X-rays (plasma radiating sources, PRS). Depending on the application, different spectral contents are desired which means that a range of atomic numbers should be available for use in the Z-pinch load. Gas puff loads complement the capabilities provided by wire array loads, offering the use of gases such as neon, argon...
Summary form only given. We will present results of recent experiments with wire array Z-pinches performed on the 1 MA MAGPIE generator. These will include measurements of the precursor plasma column by X-ray radiography, measurements of axially resolved K-shell Al spectra (both time-integrated and time-resolved), and measurements of the spatial structure of the stagnated plasma. We will discuss correlations...
Summary form only given. Recent experiments on the Z accelerator employing nested stainless steel wire arrays have produced K-shell X-ray yields in excess of 50 kJ in the range 5.5 to 8.0 keV. Stainless steel (Z=24-28) can barely be ionized to the K-shell on Z, and the spectra are thus sensitive to the implosion history. We have employed a detailed configuration non-LTE radiation hydrodynamics model...
Summary form only given. Radiographs of X-pinches driven by ~400 kA current pulses show jets of matter extending along the anode-cathode axis from both sides of the crossing point of the X pinch wires. The jets, formed by ablation of material from the heated wires of the X pinch, extend over a few mm of the 15 mm anode-cathode gap and persist over tens of ns during the X-pinch implosion. Spatially...
Summary form only given. Accurate determination of atomic data that have significant effects on line emission is crucial for reliable X-ray diagnostics of laboratory Z-pinch and astrophysical plasmas. An adequate description of the dynamics of ionization and X-ray production requires an extensive amount of atomic data that include important collisional and radiative processes such as collisional excitation...
Summary form only given. Recent 2-D MHD simulations of large diameter argon gas-puff Z-pinch loads using PLIF (planar laser induced fluorescence) initial density profiles have shown that the radiative emission and absorption characteristics of the plasmas are critically affected by the formation and evolution of nonuniform structures and inhomogeneities. In drive toward the design of large diameter...
Summary form only given. The X-ray satellite spectra arising due to 2p3/2-13x-1-3x-13d-1 (x = s, p, d) transition array, in elements with Z = 40 to 92, have been calculated. While the energies of various transitions of the array have been determined by using available Hartree Fock-Slater data on 1s-1 -2p-13x-1-1 and 2p3/2-1-3x-1 ,3x'-1, Auger transition energies and their relative intensities have...
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