Author: Essa KhooryPublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
Experimental Study of Plasma Implosion Dynamics in a Two-stage Wire Array Z-pinch Configuration
Author: Essa KhooryPhysics of High-Density Z-Pinch Plasmas
Author: Michael A. LibermanPublisher: Springer Science & Business Media
ISBN: 1461214246
Category : Science
Languages : en
Pages : 285
Book Description
A "z pinch" is a deceptively simple plasma configuration in which a longitudinal current produces a magnetic field that confines the plasma. Z-pinch research is currently one of the fastest growing areas of plasma physics, with revived interest in z-pinch controlled fusion reactors along with investigations of new z-pinch applications, such as very high power x-ray sources, high-energy neutrons sources, and ultra-high magnetic fields generators. This book provides a comprehensive review of the physics of dense z pinches and includes many recent experimental results.
The Physics of Long-Pulse Wire Array Z-Pinch Implosions
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 34
Book Description
Recent improvements in z-pinch wire array load design at Sandia National Laboratories have led to a substantial increase in pinch performance as measured by radiated powers of up to 280 TW in 4 ns and 1.8 MJ of total radiated energy. Next generation, higher current machines will allow for larger mass arrays and comparable or higher velocity implosions to be reached, possibly extending these result.dis the current is pushed above 20 MA, conventional machine design based on a 100 ns implosion time results in higher voltages, hence higher cost and power flow risk. Another approach, which shifts the risk to the load configuration, is to increase the implosion time to minimize the voltage. This approach is being investigated in a series of experimental campaigns on the Saturn and Z machines. In this paper, both experimental and two dimensional computational modeling of the fist long implosion Z experiments will be presented. The experimental data shows broader pulses, lower powers, and larger pinch diameters compared to the corresponding short pulse data. By employing a nested array configuration, the pinch diameter was reduced by 50% with a corresponding increase in power of> 30%. Numerical simulations suggest load velocity is the dominating mechanism behind these results.
Variation of High-power Aluminum-wire Array Z-pinch Dynamics with Wire Number, Array Radius, and Load Mass
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 18
Book Description
A systematic study of annular aluminum-wire z-pinches on the Saturn accelerator shows that the quality of the implosion, including the radiated power, increases with wire number. Radiation magnetohydrodynamic (RMEC) xy simulations suggest that the implosion transitions from that of individual wire plasmas to that of a continuous plasma shell when the interwire spacing is reduced below (approximately) 1.4 mm. In the plasma-shell regime, the experimental implosions exhibit 1D- and 2D-code characteristics as evidenced by the presence of a strong first and a weak second radiation pulse that correlates with a strong and weak radial convergence. In this regime, many of the radiation and plasma characteristics are in agreement with those simulated by 2D-RMHC rz simulations. Moreover, measured changes in the radiation pulse width with variations in array mass and radius are consistent with the simulations and are explained by the development of 2D fluid motion in the rz plane. Associated variations in the K-shell yield are qualitatively explained by simple K-shell radiation scaling models.
An Experimental Investigation of the Azimuthal Structures Formed During the Ablation Phase of Wire Array Z-pinches
Author: Implosion Dynamics, Radiation Characteristics, and Spectroscopic Measurements of Wire-array Z-pinches on the Cornell Beam Research Accelerator (COBRA)
Author: Ryan David McBridePublisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
This dissertation presents the results of two experimental studies of wire-array z-pinches on the 1-MA, 100-ns rise-time Cornell Beam Research Accelerator (COBRA). In the first study, results are presented which characterize the implosion dynamics and radiation output of wire array z-pinches on COBRA. Here the load geometries investigated include 10- and 20-mm tall cylindrical arrays ranging from 4 to 16 mm in diameter, and consisting of 8, 16, or 32 wires of either tungsten, aluminum, or Invar (64% iron, 36% nickel). Diagnostics fielded include an optical streak camera, a time-gated extreme-ultraviolet framing camera, a laser shadowgraph system, time-integrated pinhole cameras, an x-ray wide-band focusing spectrograph with spatial resolution, an x-ray streak camera, a load voltage monitor, a Faraday cup, a bolometer, silicon diodes, and diamond photoconducting detectors. The data produced by the entire suite of diagnostics are analyzed and presented to provide a detailed picture of the overall implosion process and resulting radiation output on COBRA. The highest x-ray peak powers (300-500 GW) and total energy yields (6-10 kJ) were obtained using 4-mmdiameter arrays that stagnated before peak current. Additional findings include a decrease in soft x-ray radiation prior to stagnation as the initial wire spacing was changed from 1.6 mm to 785 [micro]m, and a timing correlation between the onset of energetic electrons, hard x-ray generation, and the arrival of trailing current on axis-a correlation that is likely due to the formation of micro-pinches. The details of these and other findings are presented and discussed. In the second study, a new diagnostic setup was developed to record the visible-light spectra emitted from aluminum wire-array plasmas as a continuous function of time. To accomplish this, a half-meter Czerny-Turner spectrometer was used in conjunction with the existing visible light streak camera system. The emitted spectra was seen to consist solely of continuum radiation. This continuum data is now being used to determine electron density. To determine electron density from the continuum data, an absolute calibration of the detection system was required. The details of these experiments, and the absolute calibration technique are presented.
Corona Real, publicada con el plausible motivo de la amnistia concedida por la Reina Nuestra Señora Doña María Cristina de Borbon
Author: Experimental Investigation of Sheared Flow Stabilization of Z-pinches
Author: David MartinezPublisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 250
Book Description
The wire array z-pinch is an efficient x-ray source [1] which has been proposed for use in indirect drive inertial confinement fusion schemes [2]. The z-pinch can become a more efficient x-ray source if its stability is improved. Cylindrical wire array z-pinch experiments where the Rayleigh-Taylor instability was suppressed showed increased x-ray yield and power [1]; however the pressure driven MHD instabilities (sausage and kink instabilities) were still present and possibly limited the x-ray production of the pinch. Linear MHD calculations of z-pinch stability with an axial velocity shear predict that a supersonic axial flow with a radial gradient is capable of stabilizing the MHD instabilities [3][4][5]. A sheared flow can be introduced to a pinch by using a conical wire array with a fine metallic wire on axis [6]. The wire on axis will carry a fraction of the total current during the implosion which will cause the center wire to create a conducting plasma column while a flow passes over it. This presentation will compare the experimental results of a z-pinch with and without a sheared flow. From this comparison it will be shown that the sheared flow in these experiments has a stabilizing effect on the MHD instabilities present in the z-pinch plasma column.
Numerical Simulations of Annular Wire-array Z-pinches in (x, Y), (r, [theta], and (r, Z) Geometries
![Numerical Simulations of Annular Wire-array Z-pinches in (x, Y), (r, [theta], and (r, Z) Geometries PDF](https://books.google.com/books/content/images/frontcover/jIZjnQAACAAJ?fife=w80-h100)
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 25
Book Description
The Total Immersion PIC (TIP) code has been used in several two-dimensional geometries to understand better the measured dynamics of annular, aluminum wire-array z-pinches. The areas investigated include the formation of the plasma sheath from current-induced individual wire explosions, the effects of wire number and symmetry on the implosion dynamics, and the dependence of the Rayleigh-Taylor instability growth on initial sheath thickness. A qualitative change in the dynamics with increasing wire number was observed, corresponding to a transition between a z-pinch composed of non-merging, self-pinching individual wires, and one characterized by the rapid formation and subsequent implosion of a continuous plasma sheath. A sharp increase in radiated power with increasing wire number has been observed experimentally near this calculated transition. Although two-dimensional codes have correctly simulated observed power pulse durations, there are indications that three dimensional effects are important in understanding the actual mechanism by which these pulse lengths are produced.
Author: Simon Nicholas Bland