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Pulsed versus direct current calibration of a proximity focused x-ray streak camera

Description: The absolute sensitivity of a proximity focused x-ray streak tube was measured with dc Henke tube x-ray line sources. Calibration covered the photon energy range from 0.930 to 8.05 keV at five points. These data were compared to a model of sensitivity based on photocathode response and matched the model well on a relative scale. A pulsed comparison was performed using a laser-plasma x-ray source. The calculated camera sensitivity was folded with the measured spectrum and compared to measured film exposures. The predicted exposures were 6.5 times less than the measured exposures, verifying concerns that the proximity focused tube response is nonlinear with flux at low, dc flux levels. Results of dc recalibrations that varied flux levels determined the extent of this phenomenon.
Date: February 1, 1981
Creator: Rockett, P.D. & McGurn, J.S.
Partner: UNT Libraries Government Documents Department

Fast framing camera with independent frame adjustments

Description: We have designed, built and tested a fast framing camera that works in the visible and short infrared region of the spectrum, from 300 nm to 850 nm. The camera has four separate channels. Each framing channel has its own individual trigger input and individually adjustable framing gate width. Each channel is spatially separate from the other channels as well, thus allowing for complete independence among the four channels. The output from the four channels in the camera is recorded on one piece of 4 in. by 5 in. sheet of film. Each channel has a circular recording format with a useful diameter of 18 mm. The channels are positioned on the corners of a square with a center to center spacing of 4.45 cm (1.75 in.). The camera utilizes commercially available gated intensified microchannel-plate tubes. The camera contains its own power supply and gating circuits. It required four gating inputs (12 volts). The electronics occupy a volume of 27 cm x 33 cm x 14 cm. The framing part occupies a volume of 21 cm x 25 cm x 5 cm. Characteristics of the camera, such as: framing times, spatial modulation transfer functions, gate delay, and uniformity were studied utilizing a 35 picosecond long blue light pulse, generated by a nitrogen-pumped dye-laser system. A pulsed semiconductor laser at 820 nm was used as well for the setup.
Date: January 1, 1985
Creator: Kyrala, G.A.; McGurn, J.S.; Calligan, J. & Pallone, J.
Partner: UNT Libraries Government Documents Department

Radiation diagnostics in extremely harsh environments

Description: Some recent Trailmaster experiments have required to use of rather delicate radiation diagnostics in hostile environments. We have developed instrumentation for use high-explosive magnetic flux compression generators and near the noisy environment of high energy capacitor banks. These include some rather unique ''fly-away'' designs for x-ray imaging and spectroscopy, and other optical techniques for plasma temperature and field measurements. We will show some representative data and will also discuss an on-going program for the determination of magnetic field via atomic spectral line splitting and/or broadening.
Date: January 1, 1986
Creator: Dona, H.; Lee, P.H.Y.; Williams, A.H.; McGurn, J.L. & Veeser, L.R.
Partner: UNT Libraries Government Documents Department

Non-thermal effects in a hot dense plasma

Description: A hollow gas shell Z-pinch device is described, and some initial observations are shown to lead to the conclusion that there is an energetic electron beam produced along the axis of the collapsing gas shell. An experiment is summarized that directly measured some of the characteristics of this runaway electron beam. Finally, the results of an experiment which observed a new affect are presented along with a model that uses a runaway electron beam to explain this new effect. 9 refs., 17 figs.
Date: January 1, 1985
Creator: Jones, L.A.; Kania, D.R.; Hammel, B.A.; Kallne, E.; Maestas, M.D.; McGurn, J. et al.
Partner: UNT Libraries Government Documents Department

Fast Resistive Bolometry

Description: Resistive bolometry is an accurate, robust, spectrally broadband technique for measuring absolute x-ray fluence and flux. Bolometry is an independent technique for x-ray measurements that is based on a different set of physical properties than other diagnostics such as x-ray diodes, photoconducting detectors, and P-I-N diodes. Bolometers use the temperature-driven change in element resistivity to determine the total deposited energy. The calibration of such a device is based on fundamental material properties and its physical dimensions. We describe the use of nickel and gold bolometers to measure x rays generated by high-power z pinches on Sandia's Saturn and Z accelerators. The Sandia bolometer design described herein has a pulse response of {approximately}1 ns. We describe in detail the fabrication, fielding, and data analysis issues leading to highly accurate x-ray measurements. The fundamental accuracy of resistive bolometry will be discussed.
Date: February 1, 1999
Creator: Deeney, C.; Fehl, D.L.; Hanson, D.L.; Keltner, N.R.; McGurn, J.S.; McKenney, J.L. et al.
Partner: UNT Libraries Government Documents Department

Fielding and calibration issues for diamond photoconducting detectors

Description: Diamond photoconducting detectors are routinely fielded as soft x-ray diagnostics on Sandia`s Saturn facility. We have developed an improved detector mount that provides a 200-ps time response, is easily cleanable, and is very rugged. In addition, we have developed a new, fast insertion unit to apply bias voltage to the detectors. Absolute calibration of the PCDs is carried out either at the Brookhaven National Synchrotron Light Source or on Sandia`s laser calibration facility. We are now fielding diamond elements that have the dimensions 1x3x0.5 nun and 1x1xO.5 mm. We are neutron damaging some of the 1x1xO.5-mm detectors to reduce their sensitivity. We can tailor PCD sensitivity by adjusting element size and neutron damage level.
Date: December 1, 1996
Creator: Spielman, R.B.; Ruggles, L.E.; Pepping, R.E.; Breeze, S.F.; McGurn, J.S. & Struve, K.W.
Partner: UNT Libraries Government Documents Department

Fast resistive bolometry

Description: Resistive bolometry is an accurate, robust, spectrally broadband technique for measuring absolute x-ray fluence and flux. Bolometry is an independent technique for x-ray measurements that is based on a different set of physical properties than other diagnostics such as x-ray diodes, photoconducting detectors, and P-I-N diodes. Bolometers use the temperature-driven change in element resistivity to determine the total deposited energy. The calibration of such a device is based on fundamental material properties and its physical dimensions. The authors describe the use of nickel and gold bolometers to measure x rays generated by high power Z pinches on Sandia`s Saturn and Z accelerators. The Sandia bolometer design described herein has a pulse response of {approximately}1 ns. They describe in detail the fabrication, fielding, and data analysis issues leading to highly accurate x-ray measurements. The fundamental accuracy of resistive bolometry will be discussed.
Date: June 1, 1998
Creator: Spielman, R.B.; Deeney, C.; Fehl, D.L.; Hanson, D.L.; Keltner, N.R.; McGurn, J.S. et al.
Partner: UNT Libraries Government Documents Department

Fielding of the on-axis diagnostic package at Z

Description: The authors have developed a comprehensive diagnostic package for observing z-pinch radiation along the pinch axis on the Z accelerator. The instrumentation, which was fielded on the axial package, are x-ray diagnostics requiring direct lines of sight to the target. The diagnostics require vacuum access to the center of the accelerator. The environment is a hostile one, where one must deal with an intense, energetic photon flux (>100 keV), EMP, debris (e.g. bullets or shrapnel), and mechanical shock in order for the diagnostics to survive. In addition, practical constraints require the package be refurbished and utilized on a once a day shot schedule. In spite of this harsh environment, the authors have successfully fielded the diagnostic package with a high survivability of the data and the instruments. In this paper, they describe the environment and issues related to the re-entrant diagnostic package`s implementation and maintenance.
Date: June 1, 1998
Creator: Hurst, M.J.; Nash, T.J.; Derzon, M.; Kellogg, J.W.; Torres, J.; McGurn, J. et al.
Partner: UNT Libraries Government Documents Department

Spectroscopic diagnosis of foam z-pinch plasmas on SATURN

Description: Solid and annular silicon aerogel and agar foams were shot on the accelerator SATURN to study plasma initiation, acceleration, and stagnation. SATURN delivers 7 MA with a 50 nsec rise time to these foam loads. We fielded several spectroscopic diagnostics to measure plasma parameters throughout the z-pinch discharge. A spatially resolved single frame time-gated EUV spectrometer measured the extent of plasma ablation off the surface foam. A time integrated crystal spectrometer showed that characteristic K shell radiation of silicon in the aerogel and of S and Na impurities in the agar were all attenuated when the foam loads were coated with a conductive layer of gold. The time resolved pinhole camera showed that in general the quality of the pinch implosions was poor but improved with increasing efforts to improve current continuity such as prepulse and conductive coatings.
Date: June 1996
Creator: Nash, T. J.; Derzon, M. S.; Allshouse, G.; Deeney, C.; Jobe, D.; McGurn, J. et al.
Partner: UNT Libraries Government Documents Department

Diagnostics for Pioneer I imploding plasma experiments

Description: The Pioneer I series of imploding plasma experiments are aimed at collapsing a thin aluminum foil with a multimegampere, submicrosecond electrical pulse produced by an explosive flux compression generator and fast plasma compression opening switch. Anticipated experimental conditions are bounded by implosion velocities of 2 x 10/sup 7/ cm/s and maximum plasma temperatures of 100 eV. A comprehensive array of diagnostics have been deployed to measure implosion symmetry (gated microchannel plate array and other time-resolved imaging), temperature of the imploding plasma (visible/uv spectroscopy), stagnation geometry (x-ray pinhole imaging), radiation emission characteristics at pinch (XRD's, fast bolometry), and electrical drive history (Rogowski loops, Faraday rotation current detectors, and capacitive voltage probes). Diagnostic performance is discussed and preliminary results are presented.
Date: January 1, 1985
Creator: Lee, P.H.Y.; Benjamin, R.F.; Brownell, J.H.; Erickson, D.J.; Goforth, J.H.; Greene, A.E. et al.
Partner: UNT Libraries Government Documents Department

High Temperature Dynamic Hohlraums on the Pulsed Power Driver Z

Description: In the concept of the dynamic hohlraum an imploding z-pinch is optically thick to its own radiation. Radiation may be trapped inside the pinch to give a radiation temperature inside the pinch greater than that outside the pinch. The radiation is typically produced by colliding an outer Z-pinch liner onto an inner liner. The collision generates a strongly radiating shock, and the radiation is trapped by the outer liner. As the implosion continues after the collision the radiation temperature may continue to increase due to ongoing PdV (pressure times change in volume) work done by the implosion. In principal the radiation temperature may increase to the point at which the outer liner burns through, becomes optically thin, and no longer traps the radiation. One application of the dynamic hohlraum is to drive an ICF (inertial confinement fusion) pellet with the trapped radiation field. Members of the dynamic hohlraum team at Sandia National Labs have used the pulsed power driver Z (20 LMA, 100 ns) to create a dynamic hohlraum with temperature linearly ramping from 100 to 180 eV over 5 ns. On this shot zp214 a nested tungsten wire array of 4 and 2 cm diameters with masses of 2 and 1 mg imploded onto a 2.5 mg plastic annulus at 5 mm diameter. The current return can on this shot was slotted. It is likely the radiation temperature may be increased to over 200 CV by stabilizing the pinch with a solid current return can. A current return can with 9 slots imprints 9 filaments onto the imploding pinch. This degrades the optical trapping and the quality of the liner collision. A 1.6 mm diameter capsule situated inside this dynamic hohlraum of zp214 would see 15 kJ of radiation impinging on its surface before the pinch itself collapses to ...
Date: January 4, 1999
Creator: Armijo, J.; Chandler, G.A.; Cooper, G.; Derzon, M.S.; Fehl, D.; Gilliland, T. et al.
Partner: UNT Libraries Government Documents Department

Soft X-Ray Measurements of Z-Pinch-Driven Vacuum Hohlraums

Description: This article reports the experimental characterization of a z-pinch driven-vacuum hohlraum. The authors have measured soft x-ray fluxes of 5 x 10{sup 12} W/cm{sup 2} radiating from the walls of hohlraums which are 2.4--2.5 cm in diameter by 1 cm tall. The x-ray source used to drive these hohlraums was a z-pinch consisting of a 300 wire tungsten array driven by a 2 MA, 100 ns current pulse. In this hohlraum geometry, the z-pinch x-ray source can produce energies in excess of 800 kJ and powers in excess of 100 TW to drive these hohlraums. The x-rays released in these hohlraums represent greater than a factor of 25 in energy and more than a factor of three in x-ray power over previous laboratory-driven hohlraums.
Date: July 21, 1999
Creator: Baker, K. L.; Porter, J. L.; Ruggles, L. E.; Chandler, G. A.; Deeney, Chris; Vargas, M. et al.
Partner: UNT Libraries Government Documents Department

Z-Pinch Driven Inertial Confinement Fusion Target Physics Research at Sandia National Laboratories

Description: Three hohlraum concepts are being pursued at Sandia National Laboratories (SNL) to investigate the possibility of using pulsed power driven magnetic implosions (z-pinches) to drive high gain targets capable of yields in the range of 200-1000 MJ. This research is being conducted on SNL'S.Z facility that is capable of driving peak currents of 20 MA in z-pinch loads producing implosion velocities as high as 7.5X 107 cm/s, x-ray energies approaching 2 MJ, and x-ray powers exceeding 200 TW. This paper will discuss each of these hohlraum concepts and will overview the experiments that have been conducted on these systems to date.
Date: October 27, 1998
Creator: Alberts, T.E.; Asay, J.R.; Baca, P.M.; Baker, K.L.; Breeze, S.P.; Chandler, G.A. et al.
Partner: UNT Libraries Government Documents Department