Author: Ryan David McBride
Publisher:
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.
Implosion Dynamics, Radiation Characteristics, and Spectroscopic Measurements of Wire-array Z-pinches on the Cornell Beam Research Accelerator (COBRA)
Author: Ryan David McBride
Publisher:
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.
Publisher:
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.
Spectroscopic Measurements of Recent Aluminum Wire Array Z-Pinch Implosions on the Z-Accelerator
Measurement of Doppler Implosion Velocity in Wire Array Z Pinches
Streaked Visible-light Spectroscopy Measurements of Aluminum Wire-array Z-pinches on COBRA.
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.
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.
Experimental Studies of Implosion Characteristics and Radiation Properties of Planar and Cylindrical Wire Arrays and X-pinches
The relationship between implosion dynamics and stagnation structure in aluminium wire-array Z-pinches
Investigation of the Ablation and Implosion Phases in 1 MA Wire Array Z-pinches with UV and X-ray Diagnostics
Author: Austin Anderson
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 222
Book Description
Publisher:
ISBN:
Category : Electronic books
Languages : en
Pages : 222
Book Description
Wire-number Effects on High-power Annular Z-pinches and Some Characteristics at High Wire Number
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
Book Description
Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.
Publisher:
ISBN:
Category :
Languages : en
Pages : 44
Book Description
Characteristics of annular wire-array z-pinches as a function of wire number and at high wire number are reviewed. The data, taken primarily using aluminum wires on Saturn are comprehensive. The experiments have provided important insights into the features of wire-array dynamics critical for high x-ray power generation, and have initiated a renaissance in z-pinches when high numbers of wires are used. In this regime, for example, radiation environments characteristic of those encountered during the early pulses required for indirect-drive ICF ignition on the NIF have been produced in hohlraums driven by x-rays from a z-pinch, and are commented on here.
Numerical Simulations of Annular Wire-array Z-pinches in (x, Y), (r, [theta], and (r, Z) Geometries
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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.
Publisher:
ISBN:
Category :
Languages : en
Pages :
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.