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Diagnostics development plan for ZR.

Description: The Z Refurbishment (ZR) Project is a program to upgrade the Z machine at SNL with modern durable pulsed power technology, providing additional shot capacity and improved reliability as well as advanced capabilities for both pulsed x-ray production and high pressure generation. The development of enhanced diagnostic capabilities is an essential requirement for ZR to meet critical mission needs. This report presents a comprehensive plan for diagnostic instrument and infrastructure development for the first few years of ZR operation. The focus of the plan is on: (1) developing diagnostic instruments with high spatial and temporal resolution, capable of low noise operation and survival in the severe EMP, bremsstrahlung, and blast environments of ZR; and (2) providing diagnostic infrastructure improvements, including reduced diagnostic trigger signal jitter, more and flexible diagnostic line-of-sight access, and the capability for efficient exchange of diagnostics with other laboratories. This diagnostic plan is the first step in an extended process to provide enhanced diagnostic capabilities for ZR to meet the diverse programmatic needs of a broad range of defense, energy, and general science programs of an international user community into the next decade.
Date: September 1, 2003
Creator: Hanson, David Lester
Partner: UNT Libraries Government Documents Department

Scaling of X pinches from 1 MA to 6 MA.

Description: This final report for Project 117863 summarizes progress made toward understanding how X-pinch load designs scale to high currents. The X-pinch load geometry was conceived in 1982 as a method to study the formation and properties of bright x-ray spots in z-pinch plasmas. X-pinch plasmas driven by 0.2 MA currents were found to have source sizes of 1 micron, temperatures >1 keV, lifetimes of 10-100 ps, and densities >0.1 times solid density. These conditions are believed to result from the direct magnetic compression of matter. Physical models that capture the behavior of 0.2 MA X pinches predict more extreme parameters at currents >1 MA. This project developed load designs for up to 6 MA on the SATURN facility and attempted to measure the resulting plasma parameters. Source sizes of 5-8 microns were observed in some cases along with evidence for high temperatures (several keV) and short time durations (<500 ps).
Date: September 1, 2010
Creator: Bland, Simon Nicholas (Imperial College, London, United Kingdom); McBride, Ryan D.; Wenger, David Franklin; Sinars, Daniel Brian; Chittenden, Jeremy Paul (imperial College, London, United Kingdom); Pikuz, Sergei A. (Cornell University, Ithaca, NY) et al.
Partner: UNT Libraries Government Documents Department

Faraday Rotation Measurements on Z-Pinches Final Report

Description: The Campus Executive Program sponsored this research at Cornell University. The research was directed toward the implementation of laser-based diagnostics for wire-array Z-pinches. Under this contract we were able to carry out all the necessary preparations to setup the laser diagnostics to complement our x-ray backlighting measurements of the early phase of exploding wire z-pinch plasma formation.
Date: October 1, 1998
Creator: Greenley, J.B.
Partner: UNT Libraries Government Documents Department

High yield inertial fusion design for a z-pinch accelerator

Description: In this paper we discuss design calculations for high yield inertial fusion capsules, indirectly driven by a double-ended z-pinch-driven hohlraum radiation source. The z-pinches are imploded by a high current (- 60 MA) accelerator while enclosed within a hohlraum. Radial spoke arrays and shine shields isolate the capsule from the pinch plasma, magnetic field and direct x-ray shine. Our approach places minimal requirements on z-pinch uniformity and stability, usually problematic due to magneto- Rayleigh Taylor (MRT) instability. The hohlraum smooths the radiation field at the capsule, even in the presence of large millimeter scale inhomogeneities of the pinch and the high-spatial-frequency pertur- bation of the spoke array. The design requires simultaneity and reproducibility of the x-ray output to 5- 10%, however. Reproducibility at this level may be achievable based on experience with the Z and Sat- urn accelerators. Recent Z experiments also suggest a method for generating the required x-ray pulse shape, through implosion of a multi-shell z-pinch. X-ray bursts are calculated and observed to occur at each shell collision. Variation of shell masses and radii allows considerable latitude for creating the desired pulse shape. For the design considered, a capsule absorbing 1 MJ of x-rays at a peak drive tem- perature of 210 eV is found to have adequate stability and produces 400 MJ of yield. A larger capsule with slightly longer drive and similar peak temperature absorbs 2 MJ with a yield of 1200 MJ.
Date: October 1, 1998
Creator: Hammer, J H; Lindl, J; Porter, J L; Rambo, P W; Tabak, M; Toor, A et al.
Partner: UNT Libraries Government Documents Department

Application of 2-D Simulations to Z-Pinch Experiment Design and Analysis

Description: The successful 2-D simulations of z-pinch experiments (reproducing such features as the measured experimental current drive, radiation pulse shape, peak power and total radiated energy) can lead to a better understanding of the underlying physics in z-pinch implosions and to the opportunity to use such simulations in the analysis of experimental data and in the design of new experiments. Such use has been made with LANL simulations of experiments on the Sandia Saturn and Z accelerators. Applications have included ''vacuum'' and ''dynamic'' hohlraum experiments; variations in mass, radius and length; and ''nested'' array configurations. Notable examples include the explanation of the power/length results in reduced length pinches and the prediction of the current best power and pulsewidth nested array experiment. Examples of circumstances where the simulation results do not match the experiments will be given along with a discussion of opportunities for improved simulation results.
Date: October 19, 1998
Creator: Peterson, D.L.; Bowers, R.L.; Matuska, W.; Chandler, G.A.; Deeney, C.; Derzon, M.S. et al.
Partner: UNT Libraries Government Documents Department

One-and-Two-Dimensional Simulations of Liner Performance at Atlas Parameters

Description: The authors report results of one-and-two-dimensional MHD simulations of an imploding heavy liner in Z-pinch geometry. The driving current has a pulse shape and peak current characteristic of the Atlas pulsed-power facility being constructed at Los Alamos National Laboratory. One-dimensional simulations of heavy composite liners driven by 30 MA currents can achieve velocities on the order of 14 km/sec. Used to impact a tungsten target, the liner produces shock pressures of approximately fourteen megabars. The first 2-D simulations of imploding liners driven at Atlas current parameters are also described. These simulations have focused on the interaction of the liner with the glide planes, and the effect of realistic surface perturbations on the dynamics of the pinch. It is found that the former interaction does not seriously affect the inner liner surface. Results from the second problem indicate that a surface perturbation having amplitude as small as 0.2 {micro}m can have a significant effect on the implosion dynamics.
Date: October 18, 1998
Creator: Keinigs, R.K.; Atchison, W.L.; Faehl, R.J.; Mclenithan, K.D. & Trainor, R.J.
Partner: UNT Libraries Government Documents Department

Z-Pinch Generated X-Rays Demonstrate Indirect-Drive ICF Potential

Description: Hohlraums (measuring 6-mm in diameter by 7-mm in height) have been heated by x-rays from a z-pinch. Over measured x-ray input powers P of 0.7 to 13 TW, the hohlraum radiation temperature T increases from {approximately}55 to {approximately}130 eV, and is in agreement with the Planckian relation P-T{sup 4}. The results suggest that indirect-drive ICF studies involving NIF relevant pulse shapes and <2-mm diameter capsules can he studied using this arrangement.
Date: June 16, 1999
Creator: Bowers, R.L.; Chandler, G.A.; Derzon, M.S.; Hebron, D.E.; Leeper, R.J.; Matzen, M.K. et al.
Partner: UNT Libraries Government Documents Department

Computational modeling of wall-supported dense Z-pinch

Description: In our previous computational modeling of deuterium-fiber-initiated Z-pinches intended for ohmic self-heating to fusion conditions, instability-driven expansion caused densities to drop far below those desired for fusion applications; such behavior has been observed on experiments such as Los Alamos` HDZP-II. A new application for deuterium-fiber-initiated Z-pinches is Magnetized Target Fusion (MTF), in which a preheated and magnetized target plasma is hydrodynamically compressed, by a separately driven liner, to fusion conditions. Although the conditions necessary for suitable target plasma--density O(10{sup 18} cm{sup -3}), temperature O(100 eV), magnetic field O(100 kG)--are less extreme than those required for the previous ohmically heated fusion scheme, the plasma must remain magnetically insulated and clean long enough to be compressed by the imploding liner to fusion conditions, e.g., several microseconds. A fiber-initiated Z-pinch in a 2-cm-radius, 2-cm long conducting liner has been built at Los Alamos to investigate its suitability as an MTF target plasma. Two-dimensional magnetohydrodynamic modeling of this experiment shows early instability similar to that seen on HDZP-II; however, when plasma finds support and stabilization at the outer radial wall, a relatively stable profile forms and persists. Comparison of experimental results and computations, and computational inclusion of additional experimental details is being done. Analytic and computational investigation is also being done on possible instability-driven cooling of the plasma by Benard-like convective cells adjacent to the cold wall.
Date: November 1, 1997
Creator: Sheehey, P.; Gerwin, R.A. & Kirkpatrick, R.
Partner: UNT Libraries Government Documents Department

The Physics of Long-Pulse Wire Array Z-Pinch Implosions

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.
Date: December 14, 1999
Partner: UNT Libraries Government Documents Department

The Prospects for High-Yield ICF with a Z-Pinch Driven Dynamic Hohlraum

Description: Recent success with the Sandia Z machine has renewed interest in utilizing fast z-pinenes for ICF. One promising concept places the ICF capsule internal to the imploding z-pinch. At machine parameters relevant to achieving high yield, the imploding z-pinch mass has sufficient opacity to trap radiation giving rise to a dynamic hohlraum. The concept utilizes a 12 MJ, 54 MA z-pinch driver producing a capsule drive temperature exceeding 300 eV to realize a 550 MJ thermonuclear yield. They present the current high-yield design and its development that supports high-yield ICF with a z-pinch driven dynamic hohlraum.
Date: September 7, 1999
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


Description: Z-PINCH PHYSICS RADIATION FROM WIRE ARRAYS. This report describes the theory support of DTRA's Plasma Radiation Source (PRS) program carried out by NRL's Radiation Hydrodynamics Branch (Code 6720) in FY 2002. Included is work called for in DTRA MIPR 02-2045M - ''Plasma Radiation Theory Support'' and in DOE's Interagency Agreement DE-AI03-02SF22562 - ''Spectroscopic and Plasma Theory Support for Sandia National Laboratories High Energy Density Physics Campaign''. Some of this year's work was presented at the Dense Z-Pinches 5th International Conference held June 23-28 in Albuquerque, New Mexico. A common theme of many of these presentations was a demonstration of the importance of correctly treating the radiation physics for simulating Plasma Radiation Source (PRS) load behavior and diagnosing load properties, e.g, stagnation temperatures and densities. These presentations are published in the AIP Conference Proceedings and, for reference, they are included in Section 1 of this report. Rather than describe each of these papers in the Executive Summary, they refer to the abstracts that accompany each paper. As a testament to the level of involvement and expertise that the Branch brings to DTRA as well as the general Z-Pinch community, eight first-authored presentations were contributed at this conference as well as a Plenary and an Invited Talk. The remaining four sections of this report discuss subjects either not presented at the conference or requiring more space than allotted in the Proceedings.
Date: May 1, 2003
Creator: Davis, J.; Apruzese, J; Chong, Y.; Clark, R.; Dasgupta, A.; Giuliani, J. 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

Low impedance z-pinch drivers without post-hole convolute current adders.

Description: Present-day pulsed-power systems operating in the terawatt regime typically use post-hole convolute current adders to operate at sufficiently low impedance. These adders necessarily involve magnetic nulls that connect the positive and negative electrodes. The resultant loss of magnetic insulation results in electron losses in the vicinity of the nulls that can severely limit the efficiency of the delivery of the system's energy to a load. In this report, we describe an alternate transformer-based approach to obtaining low impedance. The transformer consists of coils whose windings are in parallel rather than in series, and does not suffer from the presence of magnetic nulls. By varying the pitch of the coils windings, the current multiplication ratio can be varied, leading to a more versatile driver. The coupling efficiency of the transformer, its behavior in the presence of electron flow, and its mechanical strength are issues that need to be addressed to evaluate the potential of transformer-based current multiplication as a viable alternative to conventional current adder technology.
Date: September 1, 2009
Creator: Savage, Mark Edward; Seidel, David Bruce & Mendel, Clifford Will, Jr.
Partner: UNT Libraries Government Documents Department

Variation of high-power aluminum-wire array Z-pinch dynamics with wire number, array radius, and load mass

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.
Date: June 1, 1997
Creator: Sanford, T.W.L.; Mock, R.C. & Marder, B.M.
Partner: UNT Libraries Government Documents Department

Titanium K-Shell X-Ray Production from High Velocity Wire Arrays Implosions on the 20-MA Z Accelerator

Description: 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%.
Date: January 27, 1999
Creator: Apruzese, J.P.; Beg, F.N.; Clark, R.C.; Coverdale, C.A.; Davis, J.; Deeney, C. et al.
Partner: UNT Libraries Government Documents Department

Anomalous resistivity of high-Z plasma with hydrogen admixture

Description: Among microinstabilities that may affect the resistance of a Z>>1 plasma in fast Z pinches, are the ion acoustic and the lower hybrid instabilities. We discuss effects of hydrogen ions on these instabilities and find that, by properly adjusting the hydrogen concentration, one can considerably increase the threshold current density for the onset of the instability. In addition to a strong Landau damping on hydrogen ions; there is a collisional stabilizing mechanism related to a collisional friction between the two ion species. Another interesting aspect of the stability analysis is related to the fact that the magnetization (a product of the gyrofrequency and the collisional frequency) of the heavy ions and the hydrogen ions is very different. We discuss possible ways of adding the hydrogen to high-Z material. This is simple in case of gas-puff pinches, where the hydrogen could be added to the main gas before the puffing. For the wire arrays, one might try to saturate th e assembled array by hydrogen prior to the main discharge. One more possibility is using interwoven thin wires of a main component (say, tungsten) and polymer.
Date: November 6, 1998
Creator: Ryutov, D.D. & Toor, A.
Partner: UNT Libraries Government Documents Department

One- and two-dimensional density and temperature measurements of an argon-neon Z-pinch plasma at stagnation

Description: In order to benchmark and improve current 2D radiation magnetohydrodynamic (MHD) models of Z-pinch plasmas, we have performed experiments which characterize the plasma -conditions at stagnation. In the experiments the SATURN pulsed power facility at Sandia National Laboratory was used to create an imploding -Ar-Ne plasma. An absolutely calibrated, high resolution space- and time- resolving Johann crystal spectrometer was used to infer the electron temperature Te from the slope of the hydrogenlike Ne free-bound continuum, and the ion density ni from the Stark broadening of the Ar heliunlike Rydberg series. 2D electron temperature profiles of the plasma are obtained from a set of imaging crystals also focused on the Ne free-bound continuum. We shot two types of gas nozzles in the experiment, annular and uniform fill which varies the amount of mass in the plasma. 2D local thermodynamic equilibrium (LTE) and non-LTE MM models predict a radiating region denser and cooler than measured.
Date: October 1, 1996
Creator: Wong, K.L.; Springer, P.T.; Hammer, J.H.; Iglesias, C.A.; Osterheld, A.L.; Foord, M.E. et al.
Partner: UNT Libraries Government Documents Department

Wire number doubling in plasma-shell regime increases z-accelerator x-ray power

Description: Doubling the number of tungsten wires from 120 to 240, keeping the mass fixed, increased the radiated x-ray power relative to the electrical power at the insulator stack of the z accelerator by (40{+-}20)% for 8.75- and 20-mm-radii z-pinch wire arrays. Radiation-magneto-hydrodynamic calculations suggest that the arrays were operating in the {open_quotes}plasma shell{close_quotes} regime, where the plasmas generated by the individual wires merge prior to the inward implosion of the entire array.
Date: November 1, 1997
Creator: Sanford, T.W.L.; Spielman, R.B. & Chandler, G.A.
Partner: UNT Libraries Government Documents Department

Pulsed power performance of PBFA Z

Description: PBFA Z is a new 60-TW/5-MJ electrical driver located at Sandia National Laboratories. The authors use PBFA Z to drive z pinches. The pulsed power design of PBFA Z is based on conventional single-pulse Marx generator, water-line pulse-forming technology used on the earlier Saturn and PBFA II accelerators. PBFA Z stores 11.4 MJ in its 36 Marx generators, couples 5 MJ in a 60-TW/105-ns pulse to the output water transmission lines, and delivers 3.0 MJ and 50 TW of electrical energy to the z-pinch load. Depending on the initial load inductance and the implosion time, the authors attain peak currents of 16-20 MA with a rise time of 105 ns. Current is fed to the z-pinch load through self magnetically-insulated transmission lines (MITLs). Peak electric fields in the MITLs exceed 2 MV/cm. The current from the four independent conical-disk MITLs is combined together in a double post-hole vacuum convolute with an efficiency greater than 95%. The authors achieved x-ray powers of 200 TW and x-ray energies of 1.9 MJ from tungsten wire-array z-pinch loads.
Date: August 1, 1997
Creator: Spielman, R.B.; Stygar, W.A. & Seamen, J.F.
Partner: UNT Libraries Government Documents Department

On the Possible Equilibria in a Configuration of the Type of a Diffuse Pinch

Description: Consider an axisymmetric equilibrium in a configuration where the current density j has only r and z components, and the magnetic field, accordingly, has only the {var_phi} component. Such configurations are of interest for magnetized target fusion (MTF) [1]: they include a simple diffuse Z pinch configuration and a MAGO configuration. Both can be, in principle, imploded by conducting shells to create a plasma with fusion-grade parameters. To be of interest for fusion, these configurations have to provide MHD equilibria acceptable from the viewpoint of confinement requirements. In the present note the authors analyze possible equilibria and show that only equilibria where the plasma pressure is a function of a radial coordinate (no axial dependence) are possible. A framework for such an analysis is outlined, e.g., in Shafranov's survey in ``Reviews of Plasma Physics''. In an arbitrary geometry the analysis may be quite cumbersome. What the authors show here is, that in the geometry of the type of an axisymmetric Z pinch equilibrium analysis is reduced to a set of simple algebraic relations, and allows one to come to very robust and reliable conclusions with regard to the possible equilibria.
Date: June 9, 1999
Creator: Siemon, R.E. & Ryutov, D.
Partner: UNT Libraries Government Documents Department