The effects of the cathode array on emitted hard x-ray from a small plasma focus device

NASA Astrophysics Data System (ADS)

Piriaei, D.; Mahabadi, T. D.; Javadi, S.; Ghoranneviss, M.

2017-08-01

In this study, the effects of the cathode array variations on emitted hard x-rays from a small Mather type plasma focus device (450 J) were investigated. The gradual elimination of the cathode rods inside the cathode array of the device lowered the quality and quantity of the emitted hard x-rays at different pressure values of argon gas. We theorized that the variations of the cathode array were able to change some discharge parameters that could vary the number of the energetic runaway electrons generated during the pinch phase which were responsible for the created features of the emitted hard x-rays. On the other hand, we hypothesized that the removal of the cathode rods could influence the current sheath dynamics during all the phases of a shot including its average axial velocity which was demonstrated by using two axial magnetic probes. We also theorized that cathode rod omission from the cathode array could also increase the initial inductance and the impedance of the system, and the impurities inside the plasma during the pinch phase which could lead to the growth of the instabilities. Moreover, by using the wavelet technique and studying the Mirnov signals, it was shown that the decrease of the cathode rod number increased the plasma magnetic field fluctuations or instabilities (MHD activities) that adversely affected the pinch quality, and reduced the emitted hard x-rays.

Understanding Why Students Participate in Multiple Surveys: Who are the Hard-Core Responders?

ERIC Educational Resources Information Center

Porter, Stephen R.; Whitcomb, Michael E.

2004-01-01

What causes a student to participate in a survey? This paper looks at survey response across multiple surveys to understand who the hard-core survey responders and non-responders are. Students at a selective liberal arts college were administered four different surveys throughout the 2002-2003 academic year, and we use the number of surveys…

Measurements of high-current electron beams from X pinches and wire array Z pinches.

PubMed

Shelkovenko, T A; Pikuz, S A; Blesener, I C; McBride, R D; Bell, K S; Hammer, D A; Agafonov, A V; Romanova, V M; Mingaleev, A R

2008-10-01

Some issues concerning high-current electron beam transport from the X pinch cross point to the diagnostic system and measurements of the beam current by Faraday cups are discussed. Results of computer simulation of electron beam propagation from the pinch to the Faraday cup give limits for the measured current for beams having different energy spreads. The beam is partially neutralized as it propagates from the X pinch to a diagnostic system, but within a Faraday cup diagnostic, space charge effects can be very important. Experimental results show evidence of such effects.

Random phase approximation and cluster mean field studies of hard core Bose Hubbard model

NASA Astrophysics Data System (ADS)

Alavani, Bhargav K.; Gaude, Pallavi P.; Pai, Ramesh V.

2018-04-01

We investigate zero temperature and finite temperature properties of the Bose Hubbard Model in the hard core limit using Random Phase Approximation (RPA) and Cluster Mean Field Theory (CMFT). We show that our RPA calculations are able to capture quantum and thermal fluctuations significantly better than CMFT.

Recent advances in theoretical and numerical studies of wire array Z-pinch in the IAPCM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ding, Ning, E-mail: ding-ning@iapcm.ac.cn; Zhang, Yang, E-mail: ding-ning@iapcm.ac.cn; Xiao, Delong, E-mail: ding-ning@iapcm.ac.cn

2014-12-15

Fast Z-pinch has produced the most powerful X-ray radiation source in laboratory and also shows the possibility to drive inertial confinement fusion (ICF). Recent advances in wire-array Z-pinch researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper. A typical wire array Z-pinch process has three phases: wire plasma formation and ablation, implosion and the MRT instability development, stagnation and radiation. A mass injection model with azimuthal modulation coefficient is used to describe the wire initiation, and the dynamics of ablated plasmas of wire-array Z-pinches in (r, θ) geometry is numerically studied. In the implosionmore » phase, a two-dimensional(r, z) three temperature radiation MHD code MARED has been developed to investigate the development of the Magneto-Rayleigh-Taylor(MRT) instability. We also analyze the implosion modes of nested wire-array and find that the inner wire-array is hardly affected before the impaction of the outer wire-array. While the plasma accelerated to high speed in the implosion stage stagnates on the axis, abundant x-ray radiation is produced. The energy spectrum of the radiation and the production mechanism are investigated. The computational x-ray pulse shows a reasonable agreement with the experimental result. We also suggest that using alloyed wire-arrays can increase multi-keV K-shell yield by decreasing the opacity of K-shell lines. In addition, we use a detailed circuit model to study the energy coupling between the generator and the Z-pinch implosion. Recently, we are concentrating on the problems of Z-pinch driven ICF, such as dynamic hohlraum and capsule implosions. Our numerical investigations on the interaction of wire-array Z-pinches on foam convertors show qualitative agreements with experimental results on the “Qiangguang I” facility. An integrated two-dimensional simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of

Pinch-off Scaling Law of Soap Bubbles

NASA Astrophysics Data System (ADS)

Davidson, John; Ryu, Sangjin

2014-11-01

Three common interfacial phenomena that occur daily are liquid drops in gas, gas bubbles in liquid and thin-film bubbles. One aspect that has been studied for these phenomena is the formation or pinch-off of the drop/bubble from the liquid/gas threads. In contrast to the formation of liquid drops in gas and gas bubbles in liquid, thin-film bubble pinch-off has not been well documented. Having thin-film interfaces may alter the pinch-off process due to the limiting factor of the film thickness. We observed the pinch-off of one common thin-film bubble, soap bubbles, in order to characterize its pinch-off behavior. We achieved this by constructing an experimental model replicating the process of a human producing soap bubbles. Using high-speed videography and image processing, we determined that the minimal neck radius scaled with the time left till pinch-off, and that the scaling law exponent was 2/3, similar to that of liquid drops in gas.

Fusion in a staged Z-pinch

NASA Astrophysics Data System (ADS)

Wessel, F. J.; Rahman, H. U.; Ney, P.; Valenzuela, J.; Beg, F.; McKee, E.; Darling, T.

2016-03-01

This paper is dedicated to Norman Rostoker, our (FJW and HUR) mentor and long-term collaborator, who will always be remembered for the incredible inspiration that he has provided us. Norman's illustrious career dealt with a broad range of fundamental-physics problems and we were fortunate to have worked with him on many important topics: intense-charged-particle beams, field-reversed configurations, and Z-pinches. Rostoker 's group at the University of CA, Irvine was well known for having implemented many refinements to the Z-pinch, that make it more stable, scalable, and efficient, including the development of: the gas-puff Z-pinch [1], which provides for the use of an expanded range of pinch-load materials; the gas-mixture Z-pinch [2], which enhances the pinch stability and increases its radiation efficiency; e-beam pre-ionization [3], which enhances the uniformity of the initial-breakdown process in a gas pinch; magnetic-flux-compression [4, 5], which allows for the amplification of an axial-magnetic field Bz; the Z-θ pinch [6], which predicts fusion in a pinch-on-fiber configuration; the Staged Z-pinch (SZP) [7], which allows for the amplification of the pinch self-magnetic field, Bθ , in addition to a Bz, and leads to a stable implosion and high-gain fusion [8, 9, 10]. This paper describes the physical basis for a magneto-inertial compression in a liner-on-target SZP [11]. Initially a high-atomic-number liner implodes under the action of the J →×B → , Lorentz Force. As the implosion becomes super Alfvénic, magnetosonic waves form, transporting current and magnetic field through the liner toward the interface of the low-atomic-number target. The target implosion remains subsonic with its surface bounded by a stable-shock front. Shock waves that pass into the target provide a source of target plasma pre-heat. At peak compression the assembly is compressed by liner inertia, with flux compression producing an intense-magnetic field near the target

Neutron generation from Z-pinches

NASA Astrophysics Data System (ADS)

Vikhrev, V. V.; Korolev, V. D.

2007-05-01

Recent advances in both experimental and theoretical studies on neutron generation in various Z-pinch facilities are reviewed. The main methods for enhancing neutron emission from the Z-pinch plasma are described, and the problems of igniting a thermonuclear burn wave in this plasma are discussed.

Z-Pinch Fusion for Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

SPIELMAN,RICK B.

2000-01-01

Z pinches, the oldest fusion concept, have recently been revisited in light of significant advances in the fields of plasma physics and pulsed power engineering. The possibility exists for z-pinch fusion to play a role in commercial energy applications. We report on work to develop z-pinch fusion concepts, the result of an extensive literature search, and the output for a congressionally-mandated workshop on fusion energy held in Snowmass, Co July 11-23,1999.

Pinch current limitation effect in plasma focus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, S.; Saw, S. H.; INTI International University College, 71800 Nilai

The Lee model couples the electrical circuit with plasma focus dynamics, thermodynamics, and radiation. It is used to design and simulate experiments. A beam-target mechanism is incorporated, resulting in realistic neutron yield scaling with pinch current and increasing its versatility for investigating all Mather-type machines. Recent runs indicate a previously unsuspected 'pinch current limitation' effect. The pinch current does not increase beyond a certain value however low the static inductance is reduced to. The results indicate that decreasing the present static inductance of the PF1000 machine will neither increase the pinch current nor the neutron yield, contrary to expectations.

Pulsed Flow Pinch

NASA Astrophysics Data System (ADS)

Hartman, Charles

2005-10-01

Formation of a Pulsed Flow Pinch is discussed, based on 2-D, MHD numerical calculations. The PFP utilizes the observed stable, Btheta magnetic ``bubble'' which propagates from breach to muzzle during the run-down phase of the coaxial Marshall gun. We consider two ways of launching a PFP onto a fiber or cylindrical gas cloud: 1) by propagating the bubble to small radius along an exponentially-decreasing-radius center conductor and, 2) by a radial launch to form reflex PFP's propagating in opposite directions along a fiber. We show that the bubble velocity increases to high values as the radius is decreased making the rise time of Btheta at an axial point very short. A bubble, launched into uniform gas is found to undergo unstable pinching of the front. Results will be presented of calculations of a PFP driven, neutron-producing, snow-plow pinch. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

RC64, a Rad-Hard Many-Core High- Performance DSP for Space Applications

NASA Astrophysics Data System (ADS)

Ginosar, Ran; Aviely, Peleg; Gellis, Hagay; Liran, Tuvia; Israeli, Tsvika; Nesher, Roy; Lange, Fredy; Dobkin, Reuven; Meirov, Henri; Reznik, Dror

2015-09-01

RC64, a novel rad-hard 64-core signal processing chip targets DSP performance of 75 GMACs (16bit), 150 GOPS and 38 single precision GFLOPS while dissipating less than 10 Watts. RC64 integrates advanced DSP cores with a multi-bank shared memory and a hardware scheduler, also supporting DDR2/3 memory and twelve 3.125 Gbps full duplex high speed serial links using SpaceFibre and other protocols. The programming model employs sequential fine-grain tasks and a separate task map to define task dependencies. RC64 is implemented as a 300 MHz integrated circuit on a 65nm CMOS technology, assembled in hermetically sealed ceramic CCGA624 package and qualified to the highest space standards.

RC64, a Rad-Hard Many-Core High-Performance DSP for Space Applications

NASA Astrophysics Data System (ADS)

Ginosar, Ran; Aviely, Peleg; Liran, Tuvia; Alon, Dov; Mandler, Alberto; Lange, Fredy; Dobkin, Reuven; Goldberg, Miki

2014-08-01

RC64, a novel rad-hard 64-core signal processing chip targets DSP performance of 75 GMACs (16bit), 150 GOPS and 20 single precision GFLOPS while dissipating less than 10 Watts. RC64 integrates advanced DSP cores with a multi-bank shared memory and a hardware scheduler, also supporting DDR2/3 memory and twelve 2.5 Gbps full duplex high speed serial links using SpaceFibre and other protocols. The programming model employs sequential fine-grain tasks and a separate task map to define task dependencies. RC64 is implemented as a 300 MHz integrated circuit on a 65nm CMOS technology, assembled in hermetically sealed ceramic CCGA624 package and qualified to the highest space standards.

Investigation on the pinch point position in heat exchangers

NASA Astrophysics Data System (ADS)

Pan, Lisheng; Shi, Weixiu

2016-06-01

The pinch point is important for analyzing heat transfer in thermodynamic cycles. With the aim to reveal the importance of determining the accurate pinch point, the research on the pinch point position is carried out by theoretical method. The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties. In most cases, the pinch point locates at the bubble point for the evaporator and the dew point for the condenser. However, the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator. Similarly, it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser. It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature. A wrong position for the pinch point may generate serious mistake. In brief, the pinch point should be founded by the iterative method in all conditions rather than taking for granted.

Self-pinched lithium beam transport experiments on SABRE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanson, D.L.; Olson, C.L.; Poukey, J.W.

Self-pinched transport of ion beams has many advantages for ion-driven ICF applications involving high yield and energy production. The authors are currently preparing for a self-pinched lithium beam transport experiment on the SABRE accelerator. There are three transport elements that must eventually be demonstrated: (1) efficient lithium beam generation and ballistic transport to a focus at the self-pinched transport channel entrance; (2) self-pinched transport in the channel, requiring optimized injection conditions and gas breakdown; and (3) self-pinched transport of the equilibrated beam from the channel into free space, with associated aiming and stability considerations. In the present experiment, a hollowmore » annular lithium beam from an applied-B extraction ion diode will be focused to small radius (r {le} 2 cm) in a 60 cm long ballistic focus section containing argon gas at a pressure of a few Torr. The self-pinched transport channel will contain a low pressure background gas of 10--40 mTorr argon to allow sufficient net current to confine the beam for long distance transport. IPROP simulations are in progress to optimize the design of the ballistic and self-pinched transport sections. Progress on preparation of this lithium self-pinched transport experiment, including a discussion of transport system design, important gas breakdown issues, and diagnostics, will be presented.« less

An inverse problem for Gibbs fields with hard core potential

NASA Astrophysics Data System (ADS)

Koralov, Leonid

2007-05-01

It is well known that for a regular stable potential of pair interaction and a small value of activity one can define the corresponding Gibbs field (a measure on the space of configurations of points in Rd). In this paper we consider a converse problem. Namely, we show that for a sufficiently small constant ρ¯1 and a sufficiently small function ρ¯2(x), x ∈Rd, that is equal to zero in a neighborhood of the origin, there exist a hard core pair potential and a value of activity such that ρ¯1 is the density and ρ¯2 is the pair correlation function of the corresponding Gibbs field.

Dual-core optical fiber based strain sensor for remote sensing in hard-to-reach areas

NASA Astrophysics Data System (ADS)

MÄ kowska, Anna; Szostkiewicz, Łukasz; Kołakowska, Agnieszka; Budnicki, Dawid; Bieńkowska, Beata; Ostrowski, Łukasz; Murawski, Michał; Napierała, Marek; Mergo, Paweł; Nasiłowski, Tomasz

2017-10-01

We present research on optical fiber sensors based on microstructured multi-core fiber. Elaborated sensor can be advantageously used in hard-to-reach areas by taking advantage of the fact, that optical fibers can play both the role of sensing elements and they can realize signal delivery. By using the sensor, it is possible to increase the level of the safety in the explosive endangered areas, e.g. in mine-like objects. As a base for the strain remote sensor we use dual-core fibers. The multi-core fibers possess a characteristic parameter called crosstalk, which is a measure of the amount of signal which can pass to the adjacent core. The strain-sensitive area is made by creating the tapered section, in which the level of crosstalk is changed. Due to this fact, we present broadened conception of fiber optic sensor designing. Strain measurement is realized thanks to the fact, that depending on the strain applied, the power distribution between the cores of dual-core fibers changes. Principle of operation allows realization of measurements both in wavelength and power domain.

Nonequilibrium dynamics of one-dimensional hard-core anyons following a quench: complete relaxation of one-body observables.

PubMed

Wright, Tod M; Rigol, Marcos; Davis, Matthew J; Kheruntsyan, Karén V

2014-08-01

We demonstrate the role of interactions in driving the relaxation of an isolated integrable quantum system following a sudden quench. We consider a family of integrable hard-core lattice anyon models that continuously interpolates between noninteracting spinless fermions and strongly interacting hard-core bosons. A generalized Jordan-Wigner transformation maps the entire family to noninteracting fermions. We find that, aside from the singular free-fermion limit, the entire single-particle density matrix and, therefore, all one-body observables relax to the predictions of the generalized Gibbs ensemble (GGE). This demonstrates that, in the presence of interactions, correlations between particles in the many-body wave function provide the effective dissipation required to drive the relaxation of all one-body observables to the GGE. This relaxation does not depend on translational invariance or the tracing out of any spatial domain of the system.

What can asymmetry tell us? Investigation of asymmetric versus symmetric pinch and swell structures in nature and simulation

NASA Astrophysics Data System (ADS)

Gardner, Robyn; Piazolo, Sandra; Daczko, Nathan

2015-04-01

Pinch and swell structures occur from microscopic to landscape scales where a more competent layer in a weaker matrix is deformed by pure shear, often in rifting environments. The Anita Shear Zone (ASZ) in Fiordland, New Zealand has an example of landscape scale (1 km width) asymmetric pinch and swell structures developed in ultramafic rocks. Field work suggests that the asymmetry is a result of variations in the surrounding 'matrix' flow properties as the ultramafic band is surrounded to the east by an orthogneiss (Milford Orthogneiss) and to the west by a paragneiss (Thurso Paragneiss). In addition, there is a narrow and a much wider shear zone between the ultramafics and the orthogneiss and paragneiss, respectively. Detailed EBSD analysis of samples from a traverse across the pinch and swell structure indicate the ultramafics in the shear zone on the orthogneiss side have larger grain size than the ultramafics in the shear zone on the paragneiss side. Ultramafic samples from the highly strained paragneiss and orthogneiss shear zones show dislocation creep behaviour, and, on the paragneiss side, also significant deformation by grain boundary sliding. To test if asymmetry of pinch and swell structures can be used to derive the rheological properties of not only the pinch and swell lithologies, but also of the matrix, numerical simulations were performed. Numerical modelling of pure shear (extension) was undertaken with (I) initially three layers and then (II) five layers by adding soft high strain zones on both sides of the rheological hard layer. The matrix was given first symmetric, then asymmetric viscosity. Matrix viscosity was found to impact the formation of pinch and swell structures with the weaker layer causing increased tortuosity of the competent layer edge due to increased local differential stress. Results highlight that local, rheologically soft layers and the relative viscosity of matrix both impact significantly the shape and symmetry of developing

Pinch aperture proprioception: reliability and feasibility study

PubMed Central

Yahya, Abdalghani; von Behren, Timothy; Levine, Shira; dos Santos, Marcio

2018-01-01

[Purpose] To establish the reliability and feasibility of a novel pinch aperture device to measure proprioceptive joint position sense. [Subjects and Methods] Reliability of the pinch aperture device was assessed in 21 healthy subjects. Following familiarization with a 15° target position of the index finger and thumb, subjects performed 5 trials in which they attempted to actively reproduce the target position without visual feedback. This procedure was repeated at a testing session on a separate date, and the between-session intraclass correlation coefficient (ICC) was calculated. In addition, extensor tendon vibration was applied to 19 healthy subjects, and paired t-tests were conducted to compare performance under vibration and no-vibration conditions. Pinch aperture proprioception was also assessed in two individuals with known diabetic neuropathy. [Results] The pinch aperture device demonstrated excellent reliability in healthy subjects (ICC 0.88, 95% confidence interval 0.70–0.95). Tendon vibration disrupted pinch aperture proprioception, causing subjects to undershoot the target position (18.1 ± 2.6° vs. 14.8° ± 0.76, p<0.001). This tendency to undershoot the target position was also noted in individuals with diabetic neuropathy. [Conclusion] This study describes a reliable, feasible, and functional means of measuring finger proprioception. Further research should investigate the assessment and implications of pinch aperture proprioception in neurological and orthopedic populations. PMID:29765192

Z-Pinch Pulsed Plasma Propulsion Technology Development

NASA Technical Reports Server (NTRS)

Polsgrove, Tara; Adams, Robert B.; Fabisinski, Leo; Fincher, Sharon; Maples, C. Dauphne; Miernik, Janie; Percy, Tom; Statham, Geoff; Turner, Matt; Cassibry, Jason;

[Reliability and validity of the analysis of hand grip and pinch force in isometric and isokinetic conditions].

PubMed

Benaglia, P G; Franchignoni, F; Ferriero, G; Zebellin, G; Sartorio, F

1999-01-01

Strength measurement of the hand grip is at the core of most protocols of functional assessment of the upper limb and in rehabilitation plays a major role in the analysis of treatment efficacy and patients' occupational ability. The aims of this study were to: a) verify the repeatability of strength measurements made during performance of the hand grip and three types of pinch, carried out under isometric and isokinetic conditions; b) compare maximal isometric strength with the corresponding isokinetic value for each of the manoeuvres studied; c) investigate the correlations between the strength expressed in the different manoeuvres, under both isometric and isokinetic conditions. We studied 14 voluntary subjects over three sessions conducted at 48-hr intervals, employing a computerized isokinetic dynamometer Lido WorkSet equipped with device N(o) 21 for the study of pinch (lateral pinch, pulp pinch, chuck pinch) and device N(o) 52 for the grip study. Isometric contractions resulted stronger than isokinetic ones, and the hand grip was found to be the manoeuvre able to produce most strength. The repeatability of each strength measurement test over the three days was high (Intraclass Correlation Coefficients: 0.89-0.93). Correlations between the isometric and isokinetic performance for each of the manoeuvres examined were always high (Pearson's r coefficients: 0.89-0.95) as were those between the different manoeuvres, whether performed in isometric or isokinetic modality (r: 0.60-0.94).

Theoretical z -pinch scaling relations for thermonuclear-fusion experiments.

PubMed

Stygar, W A; Cuneo, M E; Vesey, R A; Ives, H C; Mazarakis, M G; Chandler, G A; Fehl, D L; Leeper, R J; Matzen, M K; McDaniel, D H; McGurn, J S; McKenney, J L; Muron, D J; Olson, C L; Porter, J L; Ramirez, J J; Seamen, J F; Speas, C S; Spielman, R B; Struve, K W; Torres, J A; Waisman, E M; Wagoner, T C; Gilliland, T L

2005-08-01

We have developed wire-array z -pinch scaling relations for plasma-physics and inertial-confinement-fusion (ICF) experiments. The relations can be applied to the design of z -pinch accelerators for high-fusion-yield (approximately 0.4 GJ/shot) and inertial-fusion-energy (approximately 3 GJ/shot) research. We find that (delta(a)/delta(RT)) proportional (m/l)1/4 (Rgamma)(-1/2), where delta(a) is the imploding-sheath thickness of a wire-ablation-dominated pinch, delta(RT) is the sheath thickness of a Rayleigh-Taylor-dominated pinch, m is the total wire-array mass, l is the axial length of the array, R is the initial array radius, and gamma is a dimensionless functional of the shape of the current pulse that drives the pinch implosion. When the product Rgamma is held constant the sheath thickness is, at sufficiently large values of m/l, determined primarily by wire ablation. For an ablation-dominated pinch, we estimate that the peak radiated x-ray power P(r) proportional (I/tau(i))(3/2)Rlphigamma, where I is the peak pinch current, tau(i) is the pinch implosion time, and phi is a dimensionless functional of the current-pulse shape. This scaling relation is consistent with experiment when 13 MA < or = I < or = 20 MA, 93 ns < or = tau(i) < or = 169 ns, 10 mm < or = R < or = 20 mm, 10 mm < or = l < or = 20 mm, and 2.0 mg/cm < or = m/l < or = 7.3 mg/cm. Assuming an ablation-dominated pinch and that Rlphigamma is held constant, we find that the x-ray-power efficiency eta(x) congruent to P(r)/P(a) of a coupled pinch-accelerator system is proportional to (tau(i)P(r)(7/9 ))(-1), where P(a) is the peak accelerator power. The pinch current and accelerator power required to achieve a given value of P(r) are proportional to tau(i), and the requisite accelerator energy E(a) is proportional to tau2(i). These results suggest that the performance of an ablation-dominated pinch, and the efficiency of a coupled pinch-accelerator system, can be improved substantially by decreasing the

Energy balance in a Z pinch with suppressed Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Baksht, R. B.; Oreshkin, V. I.; Rousskikh, A. G.; Zhigalin, A. S.

2018-03-01

At present Z-pinch has evolved into a powerful plasma source of soft x-ray. This paper considers the energy balance in a radiating metallic gas-puff Z pinch. In this type of Z pinch, a power-law density distribution is realized, promoting suppression of Rayleigh-Taylor (RT) instabilities that occur in the pinch plasma during compression. The energy coupled into the pinch plasma, is determined as the difference between the total energy delivered to the load from the generator and the magnetic energy of the load inductance. A calibrated voltage divider and a Rogowski coil were used to determine the coupled energy and the load inductance. Time-gated optical imaging of the pinch plasma showed its stable compression up to the stagnation phase. The pinch implosion was simulated using a 1D two-temperature radiative magnetohydrodynamic code. Comparison of the experimental and simulation results has shown that the simulation adequately describes the pinch dynamics for conditions in which RT instability is suppressed. It has been found that the proportion of the Ohmic heating in the energy balance of a Z pinch with suppressed RT instability is determined by Spitzer resistance and makes no more than ten percent.

Scaling in two-fluid pinch-off

NASA Astrophysics Data System (ADS)

Pommer, Chris; Harris, Michael; Basaran, Osman

2010-11-01

The physics of two-fluid pinch-off, which arises whenever drops, bubbles, or jets of one fluid are ejected from a nozzle into another fluid, is scientifically important and technologically relevant. While the breakup of a drop in a passive environment is well understood, the physics of pinch-off when both the inner and outer fluids are dynamically active remains inadequately understood. Here, the breakup of a compound jet whose core and shell are incompressible Newtonian fluids is analyzed computationally when the interior is a "bubble" and the exterior is a liquid. The numerical method employed is an implicit method of lines ALE algorithm which uses finite elements with elliptic mesh generation and adaptive finite differences for time integration. Thus, the new approach neither starts with a priori idealizations, as has been the case with previous computations, nor is limited to length scales above that set by the wavelength of visible light as in any experimental study. In particular, three distinct responses are identified as the ratio m of the outer fluid's viscosity to the inner fluid's viscosity is varied. For small m, simulations show that the minimum neck radius r initially scales with time τ before breakup as r ˜0.58° (in accord with previous experiments and inviscid fluid models) but that r ˜τ once r becomes sufficiently small. For intermediate and large values of m, r ˜&αcirc;, where the exponent α may not equal one, once again as r becomes sufficiently small.

On the Heating of Ions in Noncylindrical Z-Pinches

NASA Astrophysics Data System (ADS)

Svirsky, E. B.

2018-01-01

The method proposed here for analyzing processes in a hot plasma of noncylindrical Z-pinches is based on separation of the group of high-energy ions into a special fraction. Such ions constitute an insignificant fraction ( 10%) of the total volume of the Z-pinch plasma, but these ions contribute the most to the formation of conditions in which the pinch becomes a source of nuclear fusion products and X-ray radiation. The method allows a quite correct approach to obtaining quantitative estimates of the plasma parameters, the nuclear fusion energy yield, and the features of neutron fluxes in experiments with Z-pinches.

General process improvements through pinch technology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linnhoff, B.; Polley, G.T.; Sahdev, V.

1988-06-01

Over the last ten years pinch technology has emerged as somewhat of a ''maverick'' development in the process design and energy conservation scene. Running contrary to general trends by taking the computer out of the loop and putting the engineer back in control, it has been questioned by some and welcomed by others. Regardless of persuasion, however, critics and advocates alike have largely failed to notice that pinch technology is more than an energy conservation tool. This is probably because soon after the advent of pinch technology in the 1970s, the process design scene became dominated by the oil crisis.more » Energy savings became the primary task of process designers and, therefore, the primary focus of the technology. Application during this period typically demonstrated energy cost savings in the range of 20 to 50 percent and payback periods of one year or less. Only recently have the other benefits of the technology reemerged. While it is true that pinch technology is essentially a heat-flow-based technique it is also true that it can be used to address a very diverse range of objectives.« less

Asymptotics of quasi-classical localized states in 2D system of charged hard-core bosons

NASA Astrophysics Data System (ADS)

Panov, Yu. D.; Moskvin, A. S.

2018-05-01

The continuous quasi-classical two-sublattice approximation is constructed for the 2D system of charged hard-core bosons to explore metastable inhomogeneous states analogous to inhomogeneous localized excitations in magnetic systems. The types of localized excitations are determined by asymptotic analysis and compared with numerical results. Depending on the homogeneous ground state, the excitations are the ferro and antiferro type vortices, the skyrmion-like topological excitations or linear domain walls.

Critical parameters of hard-core Yukawa fluids within the structural theory

NASA Astrophysics Data System (ADS)

Bahaa Khedr, M.; Osman, S. M.

2012-10-01

A purely statistical mechanical approach is proposed to account for the liquid-vapor critical point based on the mean density approximation (MDA) of the direct correlation function. The application to hard-core Yukawa (HCY) fluids facilitates the use of the series mean spherical approximation (SMSA). The location of the critical parameters for HCY fluid with variable intermolecular range is accurately calculated. Good agreement is observed with computer simulation results and with the inverse temperature expansion (ITE) predictions. The influence of the potential range on the critical parameters is demonstrated and the universality of the critical compressibility ratio is discussed. The behavior of the isochoric and isobaric heat capacities along the equilibrium line and the near vicinity of the critical point is discussed in details.

Microturbulence studies of pulsed poloidal current drive discharges in the reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carmody, D., E-mail: dcarmody@wisc.edu; Pueschel, M. J.; Anderson, J. K.

2015-01-15

Experimental discharges with pulsed poloidal current drive (PPCD) in the Madison Symmetric Torus reversed field pinch are investigated using a semi-analytic equilibrium model in the gyrokinetic turbulence code GENE. PPCD cases, with plasma currents of 500 kA and 200 kA, exhibit a density-gradient-driven trapped electron mode (TEM) and an ion temperature gradient mode, respectively. Relative to expectations of tokamak core plasmas, the critical gradients for the onset of these instabilities are found to be greater by roughly a factor of the aspect ratio. A significant upshift in the nonlinear TEM transport threshold, previously found for tokamaks, is confirmed in nonlinear reversed fieldmore » pinch simulations and is roughly three times the threshold for linear instability. The simulated heat fluxes can be brought in agreement with measured diffusivities by introducing a small, resonant magnetic perturbation, thus modeling the residual fluctuations from tearing modes. These fluctuations significantly enhance transport.« less

Formation of a pinched electron beam and an intense x-ray source in radial foil rod-pinch diodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sorokin, S. A.

2016-04-15

Low-impedance rod-pinch diode experiments were performed on the MIG generator at Institute of High Current Electronics using an aluminum foil placed between concentric electrodes of a rod-pinch diode. The J × B force accelerates the foil plasma in the axial and radial directions. After the foil plasma is pushed beyond the tip of the rod, a vacuum gap and a pinched electron beam form. The anode and cathode plasmas expansion and the following plasmas sweeping up by the J × B force can result in repetitive gap formations and closures, which are evident in the several successive intense x-ray pulses. A 0.7-mm-size point-like x-raymore » source was realized using a 1-mm-diameter tungsten rod, tapered to a point over the last 10 mm. The results of experiments show that the foil-shorted rod-pinch diode configuration has the potential to form low-impedance diodes, to shorten x-ray pulse duration and to realize submillimeter spot-size x-ray sources.« less

Overview of the Fusion Z-Pinch Experiment FuZE

NASA Astrophysics Data System (ADS)

Weber, T. R.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; UW/LLNL Team

2016-10-01

Previously, the ZaP device, at the University of Washington, demonstrated sheared flow stabilized (SFS) Z-pinch plasmas. Instabilities that have historically plagued Z-pinch plasma confinement were mitigated using sheared flows generated from a coaxial plasma gun of the Marshall type. Based on these results, a new SFS Z-pinch experiment, the Fusion Z-pinch Experiment (FuZE), has been constructed. FuZE is designed to investigate the scaling of SFS Z-pinch plasmas towards fusion conditions. The experiment will be supported by high fidelity physics modeling using kinetic and fluid simulations. Initial plans are in place for a pulsed fusion reactor following the results of FuZE. Notably, the design relies on proven commercial technologies, including a modest discharge current (1.5 MA) and voltage (40 kV), and liquid metal electrodes. Supported by DoE FES, NNSA, and ARPA-E ALPHA.

Current redistribution and generation of kinetic energy in the stagnated Z pinch.

PubMed

Ivanov, V V; Anderson, A A; Papp, D; Astanovitskiy, A L; Talbot, B R; Chittenden, J P; Niasse, N

2013-07-01

The structure of magnetic fields was investigated in stagnated wire-array Z pinches using a Faraday rotation diagnostic at the wavelength of 266 nm. The distribution of current in the pinch and trailing material was reconstructed. A significant part of current can switch from the main pinch to the trailing plasma preheated by x-ray radiation of the pinch. Secondary implosions of trailing plasma generate kinetic energy and provide enhanced heating and radiation of plasma at stagnation. Hot spots in wire-array Z pinches also provide enhanced radiation of the Z pinch. A collapse of a single hot spot radiates 1%-3% of x-ray energy of the Z pinch with a total contribution of hot spots of 10%-30%.

Contribution of flexor pollicis longus to pinch strength: an in vivo study.

PubMed

Goetz, Thomas J; Costa, Joseph A; Slobogean, Gerard; Patel, Satyam; Mulpuri, Kishore; Travlos, Andrew

2012-11-01

To estimate the contribution of the flexor pollicis longus (FPL) to key pinch strength. Secondary outcomes include tip pinch, 3-point chuck pinch, and grip strength. Eleven healthy volunteers consented to participate in the study. We recorded baseline measures for key, 3-point chuck, and tip pinch and for grip strength. In order to control for instability of the interphalangeal (IP) joint after FPL paralysis, pinch measurements were repeated after immobilizing the thumb IP joint. Measures were repeated after subjects underwent electromyography-guided lidocaine blockade of the FPL muscle. Nerve conduction studies and clinical examinations were used to confirm FPL blockade and to rule out median nerve blockade. Paired t-tests were used to compare pre- and postblock means for both unsplinted and splinted measures. The difference in means was used to estimate the contribution of FPL to pinch strength. All 3 types of pinch strength showed a significant decrease between pre- and postblock measurements. The relative contribution of FPL for each pinch type was 56%, 44%, and 43% for key, chuck, and tip pinch, respectively. Mean grip strength did not decrease significantly. Splinting of the IP joint had no significant effect on pinch measurements. FPL paralysis resulted in a statistically significant decrease in pinch strength. IP joint immobilization to simulate IP joint fusion did not affect results. Reconstruction after acute or chronic loss of FPL function should be considered when restoration of pinch strength is important. Copyright © 2012 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Finite-Larmor-radius effects on z-pinch stability

NASA Astrophysics Data System (ADS)

Scheffel, Jan; Faghihi, Mostafa

1989-06-01

The effect of finite Larmor radius (FLR) on the stability of m = 1 small-axial-wavelength kinks in a z-pinch with purely poloidal magnetic field is investigated. We use the incompressible FLR MHD model; a collisionless fluid model that consistently includes the relevant FLR terms due to ion gyroviscosity, Hall effect and electron diamagnetism. With FLR terms absent, the Kadomtsev criterion of ideal MHD, 2r dp/dr + m2B2/μ0 ≥ 0 predicts instability for internal modes unless the current density is singular at the centre of the pinch. The same result is obtained in the present model, with FLR terms absent. When the FLR terms are included, a normal-mode analysis of the linearized equations yields the following results. Marginally unstable (ideal) modes are stabilized by gyroviscosity. The Hall term has a damping (but not absolutely stabilizing) effect - in agreement with earlier work. On specifying a constant current and particle density equilibrium, the effect of electron diamagnetism vanishes. For a z-pinch with parameters relevant to the EXTRAP experiment, the m = 1 modes are then fully stabilized over the crosssection for wavelengths λ/a ≤ 1, where a denotes the pinch radius. As a general z-pinch result a critical line-density limit Nmax = 5 × 1018 m-1 is found, above which gyroviscous stabilization near the plasma boundary becomes insufficient. This limit corresponds to about five Larmor radii along the pinch radius. The result holds for wavelengths close to, or smaller than, the pinch radius and for realistic equilibrium profiles. This limit is far below the required limit for a reactor with contained alpha particles, which is in excess of 1020 m-1.

Pair Formation of Hard Core Bosons in Flat Band Systems

NASA Astrophysics Data System (ADS)

Mielke, Andreas

2018-05-01

Hard core bosons in a large class of one or two dimensional flat band systems have an upper critical density, below which the ground states can be described completely. At the critical density, the ground states are Wigner crystals. If one adds a particle to the system at the critical density, the ground state and the low lying multi particle states of the system can be described as a Wigner crystal with an additional pair of particles. The energy band for the pair is separated from the rest of the multi-particle spectrum. The proofs use a Gerschgorin type of argument for block diagonally dominant matrices. In certain one-dimensional or tree-like structures one can show that the pair is localised, for example in the chequerboard chain. For this one-dimensional system with periodic boundary condition the energy band for the pair is flat, the pair is localised.

Influence of pinches on magnetic reconnection in turbulent space plasmas

NASA Astrophysics Data System (ADS)

Olshevsky, Vyacheslav; Lapenta, Giovanni; Markidis, Stefano; Divin, Andrey

A generally accepted scenario of magnetic reconnection in space plasmas is the breakage of magnetic field lines in X-points. In laboratory, reconnection is widely studied in pinches, current channels embedded into twisted magnetic fields. No model of magnetic reconnection in space plasmas considers both null-points and pinches as peers. We have performed a particle-in-cell simulation of magnetic reconnection in a three-dimensional configuration where null-points are present nitially, and Z-pinches are formed during the simulation. The X-points are relatively stable, and no substantial energy dissipation is associated with them. On contrary, turbulent magnetic reconnection in the pinches causes the magnetic energy to decay at a rate of approximately 1.5 percent per ion gyro period. Current channels and twisted magnetic fields are ubiquitous in turbulent space plasmas, so pinches can be responsible for the observed high magnetic reconnection rates.

X-Pinch And Its Applications In X-ray Radiograph

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zou Xiaobing; Wang Xinxin; Liu Rui

2009-07-07

An X-pinch device and the related diagnostics of x-ray emission from X-pinch were briefly described. The time-resolved x-ray measurements with photoconducting diodes show that the x-ray pulse usually consists of two subnanosecond peaks with a time interval of about 0.5 ns. Being consistent with these two peaks of the x-ray pulse, two point x-ray sources of size ranging from 100 mum to 5 mum and depending on cut-off x-ray photon energy were usually observed on the pinhole pictures. The x-pinch was used as x-ray source for backlighting of the electrical explosion of single wire and the evolution of X-pinch, andmore » for phase-contrast imaging of soft biological objects such as a small shrimp and a mosquito.« less

About plasma points' generation in Z-pinch

NASA Astrophysics Data System (ADS)

Afonin, V. I.; Potapov, A. V.; Lazarchuk, V. P.; Murugov, V. M.; Senik, A. V.

1997-05-01

The streak tube study results (at visible and x-ray ranges) of dynamics of fast Z-pinch formed at explosion of metal wire in diode of high current generator are presented. Amplitude of current in the load reached ˜180 kA at increase time ˜50 ns. The results' analysis points to capability of controlling hot plasma points generation process in Z-pinch.

Scaling of X pinches from 1 MA to 6 MA.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bland, Simon Nicholas; McBride, Ryan D.; Wenger, David Franklin

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 parametersmore » 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).« less

Effect of transcranial magnetic stimulation on force of finger pinch

NASA Astrophysics Data System (ADS)

Odagaki, Masato; Fukuda, Hiroshi; Hiwaki, Osamu

2009-04-01

Transcranial magnetic stimulation (TMS) is used to explore many aspects of brain function, and to treat neurological disorders. Cortical motor neuronal activation by TMS over the primary motor cortex (M1) produces efferent signals that pass through the corticospinal tracts. Motor-evoked potentials (MEPs) are observed in muscles innervated by the stimulated motor cortex. TMS can cause a silent period (SP) following MEP in voluntary electromyography (EMG). The present study examined the effects of TMS eliciting MEP and SP on the force of pinching using two fingers. Subjects pinched a wooden block with the thumb and index finger. TMS was applied to M1 during the pinch task. EMG of first dorsal interosseous muscles and pinch forces were measured. Force output increased after the TMS, and then oscillated. The results indicated that the motor control system to keep isotonic forces of the muscles participated in the finger pinch was disrupted by the TMS.

Multicolor, time-gated, soft x-ray pinhole imaging of wire array and gas puff Z pinches on the Z and Saturn pulsed power generators.

PubMed

Jones, B; Coverdale, C A; Nielsen, D S; Jones, M C; Deeney, C; Serrano, J D; Nielsen-Weber, L B; Meyer, C J; Apruzese, J P; Clark, R W; Coleman, P L

2008-10-01

A multicolor, time-gated, soft x-ray pinhole imaging instrument is fielded as part of the core diagnostic set on the 25 MA Z machine [M. E. Savage et al., in Proceedings of the Pulsed Power Plasma Sciences Conference (IEEE, New York, 2007), p. 979] for studying intense wire array and gas puff Z-pinch soft x-ray sources. Pinhole images are reflected from a planar multilayer mirror, passing 277 eV photons with <10 eV bandwidth. An adjacent pinhole camera uses filtration alone to view 1-10 keV photons simultaneously. Overlaying these data provides composite images that contain both spectral as well as spatial information, allowing for the study of radiation production in dense Z-pinch plasmas. Cu wire arrays at 20 MA on Z show the implosion of a colder cloud of material onto a hot dense core where K-shell photons are excited. A 528 eV imaging configuration has been developed on the 8 MA Saturn generator [R. B. Spielman et al., and A. I. P. Conf, Proc. 195, 3 (1989)] for imaging a bright Li-like Ar L-shell line. Ar gas puff Z pinches show an intense K-shell emission from a zippering stagnation front with L-shell emission dominating as the plasma cools.

Turbulent equipartition pinch of toroidal momentum in spherical torus

NASA Astrophysics Data System (ADS)

Hahm, T. S.; Lee, J.; Wang, W. X.; Diamond, P. H.; Choi, G. J.; Na, D. H.; Na, Y. S.; Chung, K. J.; Hwang, Y. S.

2014-12-01

We present a new analytic expression for turbulent equipartition (TEP) pinch of toroidal angular momentum originating from magnetic field inhomogeneity of spherical torus (ST) plasmas. Starting from a conservative modern nonlinear gyrokinetic equation (Hahm et al 1988 Phys. Fluids 31 2670), we derive an expression for pinch to momentum diffusivity ratio without using a usual tokamak approximation of B ∝ 1/R which has been previously employed for TEP momentum pinch derivation in tokamaks (Hahm et al 2007 Phys. Plasmas 14 072302). Our new formula is evaluated for model equilibria of National Spherical Torus eXperiment (NSTX) (Ono et al 2001 Nucl. Fusion 41 1435) and Versatile Experiment Spherical Torus (VEST) (Chung et al 2013 Plasma Sci. Technol. 15 244) plasmas. Our result predicts stronger inward pinch for both cases, as compared to the prediction based on the tokamak formula.

Beam heated linear theta-pinch device for producing hot plasmas

DOEpatents

Bohachevsky, Ihor O.

1981-01-01

A device for producing hot plasmas comprising a single turn theta-pinch coil, a fast discharge capacitor bank connected to the coil, a fuel element disposed along the center axis of the coil, a predetermined gas disposed within the theta-pinch coil, and a high power photon, electron or ion beam generator concentrically aligned to the theta-pinch coil. Discharge of the capacitor bank generates a cylindrical plasma sheath within the theta-pinch coil which heats the outer layer of the fuel element to form a fuel element plasma layer. The beam deposits energy in either the cylindrical plasma sheath or the fuel element plasma layer to assist the implosion of the fuel element to produce a hot plasma.

Analysis of Particle Transport in DIII-D H-mode Plasma with a Generalized Pinch-Diffusion Model

NASA Astrophysics Data System (ADS)

Owen, L. W.; Stacey, W. M.; Groebner, R. J.; Callen, J. D.; Bonnin, X.

2009-11-01

Interpretative analyses of particle transport in the pedestal region of H-mode plasmas typically yield diffusion coefficients that are very small (<0.1 m^2/s) in the steep gradient region when a purely diffusive particle flux is fitted to the experimental density gradients. Previous evaluation of the particle and momentum balance equations using the experimental data indicated that the pedestal profiles are consistent with transport described by a pinch-diffusion particle flux relation [1]. This type of model is used to calculate the diffusion coefficient and pinch velocity in the core for an inter-ELM H-mode plasma in the DIII-D discharge 98889. Full-plasma SOPLS simulations using neutral beam particle and energy sources from ONETWO calculations and the model transport coefficients show good agreement with the measured density pedestal profile. 6pt [1] W.M. Stacey and R.J. Groebner, Phys. Plasmas 12, 042504 (2005).

A mean spherical model for soft potentials: The hard core revealed as a perturbation

NASA Technical Reports Server (NTRS)

Rosenfeld, Y.; Ashcroft, N. W.

1978-01-01

The mean spherical approximation for fluids is extended to treat the case of dense systems interacting via soft-potentials. The extension takes the form of a generalized statement concerning the behavior of the direct correlation function c(r) and radial distribution g(r). From a detailed analysis that views the hard core portion of a potential as a perturbation on the whole, a specific model is proposed which possesses analytic solutions for both Coulomb and Yukawa potentials, in addition to certain other remarkable properties. A variational principle for the model leads to a relatively simple method for obtaining numerical solutions.

A Reactor Development Scenario for the FuZE Sheared-Flow Stabilized Z-pinch

NASA Astrophysics Data System (ADS)

McLean, Harry S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.

2017-10-01

We present a conceptual design, scaling calculations, and development path for a pulsed fusion reactor based on a flow-stabilized Z-pinch. Experiments performed on the ZaP and ZaP-HD devices have largely demonstrated the basic physics of sheared-flow stabilization at pinch currents up to 100 kA. Initial experiments on the FuZE device, a high-power upgrade of ZaP, have achieved 20 usec of stability at pinch current 100-200 kA and pinch diameter few mm for a pinch length of 50 cm. Scaling calculations based on a quasi-steady-state power balance show that extending stable duration to 100 usec at a pinch current of 1.5 MA and pinch length of 50 cm, results in a reactor plant Q 5. Future performance milestones are proposed for pinch currents of: 300 kA, where Te and Ti are calculated to exceed 1-2 keV; 700 kA, where DT fusion power would be expected to exceed pinch input power; and 1 MA, where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPA-E and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-734770.

Strong radial electric field shear and reduced fluctuations in a reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, B.E.; Chiang, C.S.; Prager, S.C.

1997-05-01

A strongly sheared radial electric field is observed in enhanced confinement discharges in the MST reversed-field pinch. The strong shear develops in a narrow region in the plasma edge. Electrostatic fluctuations are reduced over the entire plasma edge with an extra reduction in the shear region. Magnetic fluctuations, resonant in the plasma core but global in extent, are also reduced. The reduction of fluctuations in the shear region is presumably due to the strong shear, but the causes of the reductions outside this region have not been established.

Grazing incidence extreme ultraviolet spectrometer fielded with time resolution in a hostile z-pinch environment.

PubMed

Williamson, K M; Kantsyrev, V L; Safronova, A S; Wilcox, P G; Cline, W; Batie, S; LeGalloudec, B; Nalajala, V; Astanovitsky, A

2011-09-01

This recently developed diagnostic was designed to allow for time-gated spectroscopic study of the EUV radiation (4 nm < λ < 15 nm) present during harsh wire array z-pinch implosions. The spectrometer utilizes a 25 μm slit, an array of 3 spherical blazed gratings at grazing incidence, and a microchannel plate (MCP) detector placed in an off-Rowland position. Each grating is positioned such that its diffracted radiation is cast over two of the six total independently timed frames of the MCP. The off-Rowland configuration allows for a much greater spectral density on the imaging plate but only focuses at one wavelength per grating. The focal wavelengths are chosen for their diagnostic significance. Testing was conducted at the Zebra pulsed-power generator (1 MA, 100 ns risetime) at the University of Nevada, Reno on a series of wire array z-pinch loads. Within this harsh z-pinch environment, radiation yields routinely exceed 20 kJ in the EUV and soft x-ray. There are also strong mechanical shocks, high velocity debris, sudden vacuum changes during operation, energic ion beams, and hard x-ray radiation in excess of 50 keV. The spectra obtained from the precursor plasma of an Al double planar wire array contained lines of Al IX and AlX ions indicating a temperature near 60 eV during precursor formation. Detailed results will be presented showing the fielding specifications and the techniques used to extract important plasma parameters using this spectrometer. © 2011 American Institute of Physics

Depletion zones and crystallography on pinched spheres

NASA Astrophysics Data System (ADS)

Chen, Jingyuan; Xing, Xiangjun; Yao, Zhenwei

2018-03-01

Understanding the interplay between ordered structures and substrate curvature is an interesting problem with versatile applications, including functionalization of charged supramolecular surfaces and modern microfluidic technologies. In this work, we investigate the two-dimensional packing structures of charged particles confined on a pinched sphere. By continuously pinching the sphere, we observe cleavage of elongated scars into pleats, proliferation of disclinations, and subsequently, emergence of a depletion zone at the negatively curved waist that is completely void of particles. We systematically study the geometrics and energetics of the depletion zone, and reveal its physical origin as a finite size effect, due to the interplay between Coulomb repulsion and concave geometry of the pinched sphere. These results further our understanding of crystallography on curved surfaces, and have implications in design and manipulation of charged, deformable interfaces in various applications.

Low-Temperature Crystal Structures of the Hard Core Square Shoulder Model.

PubMed

Gabriëlse, Alexander; Löwen, Hartmut; Smallenburg, Frank

2017-11-07

In many cases, the stability of complex structures in colloidal systems is enhanced by a competition between different length scales. Inspired by recent experiments on nanoparticles coated with polymers, we use Monte Carlo simulations to explore the types of crystal structures that can form in a simple hard-core square shoulder model that explicitly incorporates two favored distances between the particles. To this end, we combine Monte Carlo-based crystal structure finding algorithms with free energies obtained using a mean-field cell theory approach, and draw phase diagrams for two different values of the square shoulder width as a function of the density and temperature. Moreover, we map out the zero-temperature phase diagram for a broad range of shoulder widths. Our results show the stability of a rich variety of crystal phases, such as body-centered orthogonal (BCO) lattices not previously considered for the square shoulder model.

Method for plasma formation for extreme ultraviolet lithography-theta pinch

DOEpatents

Hassanein, Ahmed [Naperville, IL; Konkashbaev, Isak [Bolingbrook, IL; Rice, Bryan [Hillsboro, OR

2007-02-20

A device and method for generating extremely short-wave ultraviolet electromagnetic wave, utilizing a theta pinch plasma generator to produce electromagnetic radiation in the range of 10 to 20 nm. The device comprises an axially aligned open-ended pinch chamber defining a plasma zone adapted to contain a plasma generating gas within the plasma zone; a means for generating a magnetic field radially outward of the open-ended pinch chamber to produce a discharge plasma from the plasma generating gas, thereby producing a electromagnetic wave in the extreme ultraviolet range; a collecting means in optical communication with the pinch chamber to collect the electromagnetic radiation; and focusing means in optical communication with the collecting means to concentrate the electromagnetic radiation.

A Reactor Development Scenario for the FUZE Shear-flow Stabilized Z-pinch

NASA Astrophysics Data System (ADS)

McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Golingo, R. P.; Weber, T. R.

2016-10-01

We present a conceptual design, scaling calculations, and a development path for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device have demonstrated stable operation for 40 us at 150 kA total discharge current (with 100 kA in the pinch) for pinches that are 1cm in diameter and 100 cm long. Scaling calculations show that achieving stabilization for a pulse of 100 usec, for discharge current 1.5 MA, in a shortened pinch 50 cm, results in a pinch diameter of 200 um and a reactor plant Q 5 for reasonable assumptions of the various system efficiencies. We propose several key intermediate performance levels in order to justify further development. These include achieving operation at pinch currents of 300 kA, where Te and Ti are calculated to exceed 1 keV, 700 kA where fusion power exceeds pinch input power, and 1 MA where fusion energy per pulse exceeds input energy per pulse. This work funded by USDOE ARPAe ALPHA Program and performed under the auspices of Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-697801.

Scaling the Shear-flow Stabilized Z-pinch to Reactor Conditions

NASA Astrophysics Data System (ADS)

McLean, H. S.; Schmidt, A.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Cleveau, E.

2015-11-01

We present a conceptual design along with scaling calculations for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device, at the University of Washington, have demonstrated stable operation for durations of 20 usec at ~100kA discharge current for pinches that are ~1 cm in diameter and 100 cm long. The inverse of the pinch diameter and plasma energy density scale strongly with pinch current and calculations show that maintaining stabilization durations of ~7 usec for increased discharge current (~15x) in a shortened pinch (10 cm) results in a pinch diameter of ~200 um and plasma conditions that approach those needed to support significant fusion burn and energy gain (Ti ~ 30keV, density ~ 3e26/m3, ntau ~1.4e20 sec/m3). Compelling features of the concept include operation at modest discharge current (1.5 MA) and voltage (40kV) along with direct adoption of liquid metals for at least one electrode--technological capabilities that have been proven in existing, commercial, pulse power devices such as large ignitrons. LLNL-ABS-674920. This work performed under the auspices of the U.S. Department of Energy ARPAe ALPHA Program by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

X-pinch dynamics: Neck formation and implosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oreshkin, V. I.; National Research Tomsk Polytechnic University, 30 Lenin Ave., Tomsk 634050; Chaikovsky, S. A.

2014-10-15

We propose a model that describes the neck formation and implosion in an X-pinch. The process is simulated to go in two stages. The first stage is neck formation. This stage begins with an electrical explosion of the wires forming the X-pinch, and at the end of the stage, a micropinch (neck) is formed in the region where the wires are crossed. The second stage is neck implosion. The implosion is accompanied by outflow of matter from the neck region, resulting in the formation of a “hot spot”. Analytical estimates obtained in the study under consideration indicate that these stagesmore » are approximately equal in duration. Having analyzed the neck implosion dynamics, we have verified a scaling which makes it possible to explain the observed dependences of the time of occurrence of an x-ray pulse on the X-pinch current and mass.« less

Overview of the FuZE Fusion Z-Pinch Experiment

NASA Astrophysics Data System (ADS)

Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Golingo, R. P.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Higginson, D. P.; Schmidt, A.; Tummel, K. K.

2017-10-01

Successful results of the sheared flow stabilized (SFS) Z-pinch from ZaP and ZaP-HD have motivated the new FuZE project to scale the plasma performance to fusion conditions. The SFS Z-pinch is immune to the instabilities that plague the conventional Z-pinch yet maintains the same favorable radial scaling. The plasma density and temperature increase rapidly with decreasing plasma radius, which naturally leads to a compact configuration at fusion conditions. The SFS Z-pinch is being investigated as a novel approach to a compact fusion device in a collaborative ARPA-E ALPHA project with the University of Washington and Lawrence Livermore National Laboratory. The project includes an experimental effort coupled with high-fidelity physics modeling using kinetic and fluid simulations. Along with scaling law analysis, computational and experimental results from the FuZE device are presented. This work is supported by an award from US ARPA-E.

Pinch technique and the Batalin-Vilkovisky formalism

NASA Astrophysics Data System (ADS)

Binosi, Daniele; Papavassiliou, Joannis

2002-07-01

In this paper we take the first step towards a nondiagrammatic formulation of the pinch technique. In particular we proceed into a systematic identification of the parts of the one-loop and two-loop Feynman diagrams that are exchanged during the pinching process in terms of unphysical ghost Green's functions; the latter appear in the standard Slavnov-Taylor identity satisfied by the tree-level and one-loop three-gluon vertex. This identification allows for the consistent generalization of the intrinsic pinch technique to two loops, through the collective treatment of entire sets of diagrams, instead of the laborious algebraic manipulation of individual graphs, and sets up the stage for the generalization of the method to all orders. We show that the task of comparing the effective Green's functions obtained by the pinch technique with those computed in the background field method Feynman gauge is significantly facilitated when employing the powerful quantization framework of Batalin and Vilkovisky. This formalism allows for the derivation of a set of useful nonlinear identities, which express the background field method Green's functions in terms of the conventional (quantum) ones and auxiliary Green's functions involving the background source and the gluonic antifield; these latter Green's functions are subsequently related by means of a Schwinger-Dyson type of equation to the ghost Green's functions appearing in the aforementioned Slavnov-Taylor identity.

Synthesis and magnetic properties of cobalt-iron/cobalt-ferrite soft/hard magnetic core/shell nanowires

NASA Astrophysics Data System (ADS)

Leandro Londoño-Calderón, César; Moscoso-Londoño, Oscar; Muraca, Diego; Arzuza, Luis; Carvalho, Peterson; Pirota, Kleber Roberto; Knobel, Marcelo; Pampillo, Laura Gabriela; Martínez-García, Ricardo

2017-06-01

A straightforward method for the synthesis of CoFe2.7/CoFe2O4 core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe2O4 shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).

Synthesis and magnetic properties of cobalt-iron/cobalt-ferrite soft/hard magnetic core/shell nanowires.

PubMed

Londoño-Calderón, César Leandro; Moscoso-Londoño, Oscar; Muraca, Diego; Arzuza, Luis; Carvalho, Peterson; Pirota, Kleber Roberto; Knobel, Marcelo; Pampillo, Laura Gabriela; Martínez-García, Ricardo

2017-06-16

A straightforward method for the synthesis of CoFe 2.7 /CoFe 2 O 4 core/shell nanowires is described. The proposed method starts with a conventional pulsed electrodeposition procedure on alumina nanoporous template. The obtained CoFe 2.7 nanowires are released from the template and allowed to oxidize at room conditions over several weeks. The effects of partial oxidation on the structural and magnetic properties were studied by x-ray spectrometry, magnetometry, and scanning and transmission electron microscopy. The results indicate that the final nanowires are composed of 5 nm iron-cobalt alloy nanoparticles. Releasing the nanowires at room conditions promoted surface oxidation of the nanoparticles and created a CoFe 2 O 4 shell spinel-like structure. The shell avoids internal oxidation and promotes the formation of bi-magnetic soft/hard magnetic core/shell nanowires. The magnetic properties of both the initial single-phase CoFe 2.7 nanowires and the final core/shell nanowires, reveal that the changes in the properties from the array are due to the oxidation more than effects associated with released processes (disorder and agglomeration).

Exit Exams Face Pinch in Common-Core Push

ERIC Educational Resources Information Center

Ujifusa, Andrew

2012-01-01

With many states crafting assessments based on the common-core standards--and an increasing emphasis on college and career readiness--some are rethinking the kind of tests high school students must pass to graduate, or whether to use such exit exams at all. Twenty-five states, enrolling a total of 34.1 million students, make exit exams a…

Age-Related and Sex-Related Differences in Hand and Pinch Grip Strength in Adults

ERIC Educational Resources Information Center

Puh, Urska

2010-01-01

The purpose of the study was to quantify age-related changes in hand grip strength and three types of pinch grip strength (key pinch, tip pinch, and palmar pinch) among male and female participants. The study included 199 healthy participants (100 females, 99 males) aged 20-79 years, who were divided into four age groups. The Baseline Hydraulic…

Effect of Initial Conditions on Gas-Puff Z-Pinch Dynamics.

NASA Astrophysics Data System (ADS)

Peterson, Gus Gordon

This dissertation concerns the effects initial conditions have on the dynamics of an imploded, annular gas-puff z-pinch. The influence of axial magnetic fields, nozzle size and composition, different gases, pre-ionization, and electrode design on pinch quality and x-ray yield is investigated. The experiment uses a 5-kJ capacitor bank to deliver 0.35 MA to the pinch load in 1.4 mu rm s. This research establishes parameters important to increasing the x-ray yield of dense z-pinches. The initial stage of the implosion is diagnosed with a framing camera that photographs visible light emitted from z-pinch gas breakdown. Data from subsequent stages of the pinch is recorded with a B-dot probe, filtered x-ray diodes, an x-ray filtered pinhole camera, and a nitrogen laser interferometer. Applied axial magnetic fields of ~100 gauss increase average x-ray yield by more than 20%. A substantial increase of K-shell x -ray yield of more than 200% was obtained by increasing the energy delivered to the plasma by enlarging the nozzle diameter from 4 to 5 cm. The use of a Teflon outer-mantle for the nozzle resulted in less uniform gas breakdown as compared to graphite and copper outer-mantles, but x-ray yield and final state uniformity were not reduced. Lower Z gases showed poorer breakdown uniformity. Pre-ionization improved the uniformity of helium and neon breakdown but did not appear to affect subsequent dynamics. X-ray yield was significantly higher using a knife-edge annular anode, as opposed to a flat stainless steel honeycomb anode. Annular anodes with diameters more than a few millimeters different than the nozzle diameter produced low quality pinches with substantially lower x-ray yield.

A flexible tactile sensitive sheet using a hetero-core fiber optic sensor

NASA Astrophysics Data System (ADS)

Fujino, S.; Yamazaki, H.; Hosoki, A.; Watanabe, K.

2014-05-01

In this report, we have designed a tactile sensitive sheet based on a hetero-core fiber-optic sensor, which realize an areal sensing by using single sensor potion in one optical fiber line. Recently, flexible and wide-area tactile sensing technology is expected to applied to acquired biological information in living space and robot achieve long-term care services such as welfare and nursing-care and humanoid technology. A hetero-core fiber-optic sensor has several advantages such as thin and flexible transmission line, immunity to EMI. Additionally this sensor is sensitive to moderate bending actions with optical loss changes and is independent of temperature fluctuation. Thus, the hetero-core fiber-optic sensor can be suitable for areal tactile sensing. We measure pressure characteristic of the proposed sensitive sheet by changing the pressure position and pinching characteristic on the surface. The proposed tactile sensitive sheet shows monotonic responses on the whole sensitive sheet surface although different sensitivity by the position is observed at the sensitive sheet surface. Moreover, the tactile sensitive sheet could sufficiently detect the pinching motion. In addition, in order to realize the discrimination between pressure and pinch, we fabricated a doubled-over sensor using a set of tactile sensitive sheets, which has different kinds of silicon robbers as a sensitive sheet surface. In conclusion, the flexible material could be given to the tactile sensation which is attached under proposed sensitive sheet.

Hybrid X-pinch Experiments on a MA Linear Transformer Driver

NASA Astrophysics Data System (ADS)

Patel, S. G.; Yager-Elorriaga, D. A.; Steiner, A. M.; Gilgenbach, R. M.; Jordan, N. M.; Chalenski, D. A.; Lau, Y. Y.

2013-10-01

X-pinch experiments have been conducted on the Linear Transformer Driver (LTD) at the University of Michigan. The x-pinch consists of a single wire separated by conical electrodes between two current return plates. The LTD was charged to +/-70 kV resulting in approximately 0.5 MA passing through a 35 μm Al wire. Multiple, short x-ray bursts were detected over the 400 ns current pulse. Ultimately the x-pinch will be located in parallel with a planar foil in order to backlight the Magneto-Rayleigh-Taylor instability. A smaller 100 kA driver is also in development and may be used to independently energize the x-pinch. The x-pinch chamber has been constructed and the results of these experiments will be presented. This work was supported by DoE award number DE-SC0002590, NSF grant number PHY 0903340, and US DoE through Sandia National Labs award numbers 240985 and 76822 to the U of Michigan. S.G Patel and A.M Steiner are supported by NPSC funded by Sandia National Labs. D.A. Yager-Elorriaga is supported by an NSF fellowship under grant number DGE 1256260.

Dynamical analysis of surface-insulated planar wire array Z-pinches

NASA Astrophysics Data System (ADS)

Li, Yang; Sheng, Liang; Hei, Dongwei; Li, Xingwen; Zhang, Jinhai; Li, Mo; Qiu, Aici

2018-05-01

The ablation and implosion dynamics of planar wire array Z-pinches with and without surface insulation are compared and discussed in this paper. This paper first presents a phenomenological model named the ablation and cascade snowplow implosion (ACSI) model, which accounts for the ablation and implosion phases of a planar wire array Z-pinch in a single simulation. The comparison between experimental data and simulation results shows that the ACSI model could give a fairly good description about the dynamical characteristics of planar wire array Z-pinches. Surface insulation introduces notable differences in the ablation phase of planar wire array Z-pinches. The ablation phase is divided into two stages: insulation layer ablation and tungsten wire ablation. The two-stage ablation process of insulated wires is simulated in the ACSI model by updating the formulas describing the ablation process.

Hard sphere packings within cylinders.

PubMed

Fu, Lin; Steinhardt, William; Zhao, Hao; Socolar, Joshua E S; Charbonneau, Patrick

2016-03-07

Arrangements of identical hard spheres confined to a cylinder with hard walls have been used to model experimental systems, such as fullerenes in nanotubes and colloidal wire assembly. Finding the densest configurations, called close packings, of hard spheres of diameter σ in a cylinder of diameter D is a purely geometric problem that grows increasingly complex as D/σ increases, and little is thus known about the regime for D > 2.873σ. In this work, we extend the identification of close packings up to D = 4.00σ by adapting Torquato-Jiao's adaptive-shrinking-cell formulation and sequential-linear-programming (SLP) technique. We identify 17 new structures, almost all of them chiral. Beyond D ≈ 2.85σ, most of the structures consist of an outer shell and an inner core that compete for being close packed. In some cases, the shell adopts its own maximum density configuration, and the stacking of core spheres within it is quasiperiodic. In other cases, an interplay between the two components is observed, which may result in simple periodic structures. In yet other cases, the very distinction between the core and shell vanishes, resulting in more exotic packing geometries, including some that are three-dimensional extensions of structures obtained from packing hard disks in a circle.

Studies of the Plasma Triggering Mechanism of Inverse Pinch Switch

DTIC Science & Technology

1993-11-10

plasma - focus driven plasma-puff was also discussed in comparison with the hypocycloidal pinch plasma-puff triggering. The main discharge of inverse pinch switch with plasma - focus driven plasma-puff trigger is found to be more azimuthally uniform than that with hypocycloidal pinch plasma-puff trigger in a gas pressure region between 80 mTorr and 1 Torr. A comparative study of the INPIStron and a spark gap also reveals that the INPIStron with a low impedance Z = 9 ohms can transfer a high voltage pulse with a superior pulse-shape fidelity over that with

Quasi-linear gyrokinetic predictions of the Coriolis momentum pinch in NSTX

DOE Data Explorer

Guttenfelder, W. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Kaye, S. M. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Ren, Y. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Solomon, W. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bell, R. E. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Candy, J. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Gerhardt, S. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); LeBlanc, B. P. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Yuh, H. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

2016-04-01

This paper presents quasi-linear gyrokinetic predictions of the Coriolis momentum pinch for low aspect-ratio NSTX H-modes where previous experimental measurements were focused. Local, linear calculations predict that in the region of interest (just outside the mid-radius) of these relatively high-beta plasmas, profiles are most unstable to microtearing modes that are only effective in transporting electron energy. However, sub-dominant electromagnetic and electrostatic ballooning modes are also unstable, which are effective at transporting energy, particles and momentum. The quasi-linear prediction of transport from these weaker ballooning modes, assuming they contribute transport in addition to that from microtearing modes in a nonlinear turbulent state, leads to a very small or outward convection of momentum, inconsistent with the experimentally measured inward pinch, and opposite to predictions in conventional aspect ratio tokamaks. Additional predictions of a low beta L-mode plasma, unstable to more traditional electrostatic ion temperature gradient-trapped electron mode instability, show that the Coriolis pinch is inward but remains relatively weak and insensitive to many parameter variations. The weak or outward pinch predicted in NSTX plasmas appears to be at least partially correlated to changes in the parallel mode structure that occur at finite beta and low aspect ratio, as discussed in previous theories. The only conditions identified where a stronger inward pinch is predicted occur either in the purely electrostatic limit or if the aspect ratio is increased. As the Coriolis pinch cannot explain the measured momentum pinch, additional theoretical momentum transport mechanisms are discussed that may be potentially important.

α Heating in a Stagnated Z-pinch

NASA Astrophysics Data System (ADS)

Appelbe, Brian; Chittenden, Jeremy

2009-01-01

A computational investigation of a scheme for magneto-inertial confinement fusion in a Z-pinch is carried out. In the scheme implosion of a deuterium-tritium fuel mass is preceded by formation of a hotspot containing warm, dense plasma on axis. The presence of the hotspot increases energy yield. Compression of the hotspot by the main fuel mass initiates thermonuclear burn. There is significant heating of the plasma by thermonuclear α particles which are confined by the strong magnetic field of the Z-pinch.

A kind of fast shutter for Z pinch diagnosis device.

PubMed

Wang, Liangping; Zhang, Xinjun; Sun, Tieping; Mao, Wentin

2016-09-01

A kind of fast shutter for protecting the diagnosis devices in Z pinch experiments is introduced in this paper. The shutter is composed of a pulling rod, a magnetic core, and a solenoid. Different from the traditional coils which were used at the voltage of 220 V, the solenoid we used must endure the high voltage of 5-10 kV and the deformation which maybe caused by the 5-10 T intense magnetic field. A creative configuration for the solenoid is developed including the winding guide, insulating sleeve, and stainless-steel sleeve. The experimental results show that the configuration of the solenoid is effective. The velocity of the valve is nearly 19 m/s and the time jitter of the shutdown is within 75 μs.

A kind of fast shutter for Z pinch diagnosis device

NASA Astrophysics Data System (ADS)

Wang, Liangping; Zhang, Xinjun; Sun, Tieping; Mao, Wentin

2016-09-01

A kind of fast shutter for protecting the diagnosis devices in Z pinch experiments is introduced in this paper. The shutter is composed of a pulling rod, a magnetic core, and a solenoid. Different from the traditional coils which were used at the voltage of 220 V, the solenoid we used must endure the high voltage of 5-10 kV and the deformation which maybe caused by the 5-10 T intense magnetic field. A creative configuration for the solenoid is developed including the winding guide, insulating sleeve, and stainless-steel sleeve. The experimental results show that the configuration of the solenoid is effective. The velocity of the valve is nearly 19 m/s and the time jitter of the shutdown is within 75 μs.

Bubble pinch-off and scaling during liquid drop impact on liquid pool

NASA Astrophysics Data System (ADS)

Ray, Bahni; Biswas, Gautam; Sharma, Ashutosh

2012-08-01

Simulations are performed to show entrapment of air bubble accompanied by high speed upward and downward water jets when a water drop impacts a pool of water surface. A new bubble entrapment zone characterised by small bubble pinch-off and long thick jet is found. Depending on the bubble and jet behaviour, the bubble entrapment zone is subdivided into three sub-regimes. The entrapped bubble size and jet height depends on the crater shape and its maximum depth. During the bubble formation, bubble neck develops an almost singular shape as it pinches off. The final pinch-off shape and the power law governing the pinching, rneck ∝ A(t0 - t)αvaries with the Weber number. Weber dependence of the function describing the radius of the bubble during the pinch-off only affects the coefficient A and not the power exponent α.

34. DESPATCH CORE OVENS, GREY IRON FOUNDRY CORE ROOM, BAKES ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

34. DESPATCH CORE OVENS, GREY IRON FOUNDRY CORE ROOM, BAKES CORES THAT ARE NOT MADE ON HEATED OR COLD BOX CORE MACHINES, TO SET BINDING AGENTS MIXED WITH THE SAND CREATING CORES HARD ENOUGH TO WITHSTAND THE FLOW OF MOLTEN IRON INSIDE A MOLD. - Stockham Pipe & Fittings Company, Grey Iron Foundry, 4000 Tenth Avenue North, Birmingham, Jefferson County, AL

Measurement of Radiation Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Hanson, David L.

2001-10-01

The z-pinch driven hohlraum (ZPDH) is a promising approach to high yield inertial confinement fusion currently being characterized in experiments on the Sandia Z accelerator [1]. In this concept [2], x rays are produced by an axial z-pinch in a primary hohlraum at each end of a secondary hohlraum. A fusion capsule in the secondary is imploded by a symmetric x-ray flux distribution, effectively smoothed by wall reemission during transport to the capsule position. Capsule radiation symmetry, a critical issue in the design of such a system, is influenced by hohlraum geometry, wall motion and time-dependent albedo, as well as power balance and pinch timing between the two z-pinch x-ray sources. In initial symmetry studies on Z, we used solid low density burnthrough spheres to diagnose highly asymmetric, single-sided-drive hohlraum geometries. We then applied this technique to the more symmetric double z-pinch geometry [3]. As a result of design improvements, radiation flux symmetry in Z double-pinch wire array experiments now exceeds the measurement sensitivity of this self-backlit foam ball symmetry diagnostic (15% max-min flux asymmetry). To diagnose radiation symmetry at the 2 - 5% level attainable with our present ZPDH designs, we are using high-energy x rays produced by the recently-completed Z-Beamlet laser backlighter for point-projection imaging of thin-wall implosion and symmetry capsules. We will present the results of polar flux symmetry measuremets on Z for several ZPDH capsule geometries together with radiosity and radiation-hydrodynamics simulations for comparison. [1] M. E. Cuneo et al., Phys. Plasmas 8,2257(2001); [2] J. H. Hammer et al., Phys. Plasmas 6,2129(1999); [3] D. L. Hanson et al., Bull. Am. Phys. Soc. 45,360(2000).

Retention of the Hard-to-Employ. Perspectives on Training the Disadvantaged--The Hard-to-Employ. Personnel Services Review Series 2.

ERIC Educational Resources Information Center

Harrison, Don K.; Brown, Dorothy R.

Although calculated by various statistical methods, retention (in this monograph) refers to the time that a former hard core member stays on the job. These rates may be tallied from the first day of pre-vocational training at a center, from the first day of a plant's vestibule training, or the first day of work at the job site. The hard core need…

Acute and repeated activation of male sexual behavior by tail pinch: opioid and dopaminergic mechanisms.

PubMed

Leyton, M; Stewart, J

1996-07-01

We studied the effect of tail pinch on male sexual behavior and its neurochemical basis. Male rats were gonadectomized and maintained on low doses of testosterone propionate (20.0 micrograms/day). Tail pinch significantly increased the percentage of males that mounted, intromitted, and ejaculated within a 30-min test, and these increases were attenuated by both pimozide (1.0 mg/kg, i.p.) and by naloxone (0.5, 1.0, and 2.0 mg/kg, s.c.). Moreover, tail pinch in the presence of an estrous female led to significantly increased female-directed behavior 48 h later during a test without tail pinch. Repeated tail pinch tests led to progressively more sexual activity, and the development of this behavioral sensitization was prevented by naloxone. These findings suggest that tail pinch increases the salience of the incentive characteristics of the female. Furthermore, during subsequent tests, with or without tail pinch, the increased salience of the female remains, as measured by the continued increases in sexual activity. These acute and sensitized behavioral increases might result from tail pinch-induced activation of the midbrain dopamine system via an opioid mechanism; either preventing tail pinch-induced dopamine activation (by an opioid antagonist) or blocking the effects of dopamine activation (by a dopamine antagonist) attenuated the long-term facilitation of sexual behavior seen after pairing the female with tail pinch.

Recent developments in linear theta-pinch research: experiment and theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

McKenna, K.F.; Bartsch, R.R.; Commisso, R.J.

1978-01-01

High energy plasmas offusion interest can be generated in linear theta pinches. However, end losses present a fundamental limitation on the plasma containment time. This paper discusses recent progress in end-loss and end-stoppering experiments and in the theoretical understanding of linear theta-pinch physics.

Pulse Power Compression by Cutting a Dense Z-Pinch with a Laser Beam

NASA Astrophysics Data System (ADS)

Winterberg, F.

1999-07-01

A thin cut made through a z-pinch by an intense laser beam can become a magnetically insulated diode crossed by an intense ion beam. For larger cuts, the gap is crossed by an intense relativistic electron beam, stopped by magnetic bremsstrahlung resulting in a pointlike intense x-ray source. In either case, the impedance of the pinch discharge is increased, with the power delivered rising in the same pro-portion. A magnetically insulated cut is advantageous for three reasons: First, with the ion current com-parable to the Alfvèn ion current, the pinch instabilities are reduced. Second, with the energy deposit-ed into fast ions, a non-Maxwellian velocity distribution is established increasing<σ ν> value for nuclear fusion reactions taking place in the pinch discharge. Third, in a high density z-pinch plasma, the intense ion beam can launch a thermonuclear detonation wave propagating along the pinch discharge channel. For larger cuts the soft x-rays produced by magnetic bremsstrahlung can be used to drive a thermonuclear hohlraum target. Finally, the proposed pulse power compression scheme permits to use a cheap low power d.c. source charging a magnetic storage coil delivering the magnetically stored energy to the pinch discharge load by an exploding wire opening switch.

Starting buoyant plumes and vortex ring pinch-off

NASA Astrophysics Data System (ADS)

Pottebaum, Tait; Gharib, Mory

2003-11-01

The vortex ring formation process of a starting buoyant plume was studied experimentally. Buoyant plumes were produced using a heating element at the base of a water tank. The velocity and temperature fields in the flow were measured using digital particle image thermometry and velocimetry (DPITV), allowing the density and vorticity fields to be determined. The vortex ring initially grew, with additional circulation being supplied by the trailing plume. At later times, the vortex ring became disconnected from the trailing plume. This is analogous to the pinch-off of a vortex ring produced by a piston-cylinder apparatus reported by Gharib et al (1998 JFM 360: 121-140). The existence of a pinch-off process for starting buoyant plumes has many implications for environmental flows. Of particular interest is the effect of vortex ring pinch-off on the dispersal of particulates and contaminants in intermittent or sudden convection events.

"Marginal pinching" in soap films

NASA Astrophysics Data System (ADS)

Aradian, A.; Raphaël, E.; de Gennes, P.-G.

2001-09-01

We discuss the behaviour of a thin soap film facing a frame element: the pressure in the Plateau border around the frame is lower than the film pressure, and the film thins out over a certain distance λ(t), due to the formation of a well-localized pinched region of thickness h(t) and extension w(t). We construct a hydrodynamic theory for this thinning process, assuming a constant surface tension: Marangoni effects are probably important only at late stages, where instabilities set in. We find λ(t) ~ t1/4, and for the pinch dimensions, h(t) ~ t-1/2 and w(t) ~ t-1/4. These results may play a useful role for the discussion of later instabilities leading to a global film thinning and drainage, as first discussed by K. Mysels under the name "marginal regeneration".

Study of a non-equilibrium plasma pinch with application for microwave generation

NASA Astrophysics Data System (ADS)

Al Agry, Ahmad Farouk

The Non-Equilibrium Plasma Pinch (NEPP), also known as the Dense Plasma Focus (DPF) is well known as a source of energetic ions, relativistic electrons and neutrons as well as electromagnetic radiation extending from the infrared to X-ray. In this dissertation, the operation of a 15 kJ, Mather type, NEPP machine is studied in detail. A large number of experiments are carried out to tune the machine parameters for best performance using helium and hydrogen as filling gases. The NEPP machine is modified to be able to extract the copious number of electrons generated at the pinch. A hollow anode with small hole at the flat end, and a mock magnetron without biasing magnetic field are built. The electrons generated at the pinch are very difficult to capture, therefore a novel device is built to capture and transport the electrons from the pinch to the magnetron. The novel cup-rod-needle device successfully serves the purpose to capture and transport electrons to monitor the pinch current. Further, the device has the potential to field emit charges from its needle end acting as a pulsed electron source for other devices such as the magnetron. Diagnostics tools are designed, modeled, built, calibrated, and implemented in the machine to measure the pinch dynamics. A novel, UNLV patented electromagnetic dot sensors are successfully calibrated, and implemented in the machine. A new calibration technique is developed and test stands designed and built to measure the dot's ability to track the impetus signal over its dynamic range starting and ending in the noise region. The patented EM-dot sensor shows superior performance over traditional electromagnetic sensors, such as Rogowski coils. On the other hand, the cup-rod structure, when grounded on the rod side, serves as a diagnostic tool to monitor the pinch current by sampling the actual current, a quantity that has been always very challenging to measure without perturbing the pinch. To the best of our knowledge, this method

One-pot synthesis of biocompatible Te@phenol formaldehyde resin core-shell nanowires with uniform size and unique fluorescent properties by a synergized soft-hard template process.

PubMed

Qian, Haisheng; Zhu, Enbo; Zheng, Shunji; Li, Zhengquan; Hu, Yong; Guo, Changfa; Yang, Xingyun; Li, Liangchao; Tong, Guoxiu; Guo, Huichen

2010-12-10

One-pot hydrothermal process has been developed to synthesize uniform Te@phenol formaldehyde resin core-shell nanowires with unique fluorescent properties. A synergistic soft-hard template mechanism has been proposed to explain the formation of the core-shell nanowires. The Te@phenol formaldehyde resin core-shell nanowires display unique fluorescent properties, which give strong luminescent emission in the blue-violet and green regions with excitation wavelengths of 270 nm and 402 nm, respectively.

Producing High-Performance, Stable, Sheared-Flow Z-Pinches in the FuZE project

NASA Astrophysics Data System (ADS)

Golingo, R. P.; Shumlak, U.,; Nelson, B. A.; Claveau, E. L.; Forbes, E. G.; Stepanov, A. D.; Weber, T. R.; Zhang, Y.; McLean, H. S.; Tummel, K. K.; Higginson, D. P.; Schmidt, A. E.; University of Washington (UW) Collaboration; Lawrence Livermore National Laboratory (LLNL) Collaboration

2017-10-01

The Fusion Z-Pinch Experiment (FuZE) has made significant strides towards generating high-performance, stable Z-pinch plasmas with goals of ne = 1018 cm-3 and T =1 keV. The Z-pinch plasmas are stabilized with a sheared axial flow that is driven by a coaxial accelerator. The new FuZE device has been constructed and reproduces the major scientific achievements the ZaP project at the University of Washington; ne = 1016 cm-3,T = 100 eV, r<1 cm, and tstable >20 μs. These parameters are measured with an array of magnetic field probes, spectroscopy, and fast framing cameras. The plasma parameters are achieved using a small fraction of the maximum energy storage and gas injection capability of the FuZE device. Higher density, ne = 5×1017 cm-3, and temperature, T = 500 eV, Z-pinch plasmas are formed by increasing the pinch current. At the higher voltages and currents, the ionization rates in the accelerator increase. By modifying the neutral gas profile in the accelerator, the plasma flow from the accelerator is maintained, driving the flow shear. Formation and sustainment of the sheared-flow Z-pinch plasma will be discussed. Experimental data demonstrating high performance plasmas in a stable Z-pinches will be shown. This work is supported by an award from US ARPA-E.

Resolving microstructures in Z pinches with intensity interferometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apruzese, J. P.; Kroupp, E.; Maron, Y.

2014-03-15

Nearly 60 years ago, Hanbury Brown and Twiss [R. Hanbury Brown and R. Q. Twiss, Nature 178, 1046 (1956)] succeeded in measuring the 30 nrad angular diameter of Sirius using a new type of interferometry that exploited the interference of photons independently emitted from different regions of the stellar disk. Its basis was the measurement of intensity correlations as a function of detector spacing, with no beam splitting or preservation of phase information needed. Applied to Z pinches, X pinches, or laser-produced plasmas, this method could potentially provide spatial resolution under one micron. A quantitative analysis based on the workmore » of Purcell [E. M. Purcell, Nature 178, 1449 (1956)] reveals that obtaining adequate statistics from x-ray interferometry of a Z-pinch microstructure would require using the highest-current generators available. However, using visible light interferometry would reduce the needed photon count and could enable its use on sub-MA machines.« less

Exchange coupling and microwave absorption in core/shell-structured hard/soft ferrite-based CoFe2O4/NiFe2O4 nanocapsules

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Xianguo; Or, Siu Wing; Ho, S. L.

2017-05-01

Core/shell-structured, hard/soft spinel-ferrite-based CoFe2O4/NiFe2O4 (CFO/NFO) nanocapsules with an average diameter of 17 nm are synthesized by a facile two-step hydrothermal process using CFO cores of ˜15 nm diameter as the hard magnetic phase and NFO shells of ˜1 nm thickness as the soft magnetic phase. The single-phase-like hysteresis loop with a high remnant-to-saturation magnetization ratio of 0.7, together with a small grain size of ˜16 nm, confirms the existence of exchange-coupling interaction between the CFO cores and the NFO shells. The effect of hard/soft exchange coupling on the microwave absorption properties is studied. Comparing to CFO and NFO nanoparticles, the finite-size NFO shells and the core/shell structure enable a significant reduction in electric resistivity and an enhancement in dipole and interfacial polarizations in the CFO/NFO nanocapsules, resulting in an obvious increase in dielectric permittivity and loss in the whole S-Ku bands of microwaves of 2-18 GHz, respectively. The exchange-coupling interaction empowers a more favorable response of magnetic moment to microwaves, leading to enhanced exchange resonances in magnetic permeability and loss above 10 GHz. As a result, strong absorption, as characterized by a large reflection loss (RL) of -20.1 dB at 9.7 GHz for an absorber thickness of 4.5 mm as well as a broad effective absorption bandwidth (for RL<-10 dB) of 8.4 GHz (7.8-16.2 GHz) at an absorber thickness range of 3.0-4.5 mm, is obtained.

Functional sensibility assessment. Part I: develop a reliable apparatus to assess momentary pinch force control.

PubMed

Chiu, Haw-Yen; Hsu, Hsiu-Yun; Kuo, Li-Chieh; Chang, Jer-Hao; Su, Fong-Chin

2009-08-01

A precise magnitude and timing control of pinch performance is based on accurate feed-forward and feedback control mechanisms. Ratio of peak pinch force and maximum load force during a functional performance is a sensitive parameter to reflect the ability to scale pinch force output according to actual loads. A pinch apparatus was constructed to detect momentary pinch force modulation of 20 subjects with normal hand sensation. The results indicated high intra-class correlation coefficient and small coefficient of variation of the detected force ratio among three repeated tests, which represented that the stability test of the measured response confirmed the feasibility of this apparatus. The force ratio for a 480 g object with a steel surface ranged between 1.77 and 1.98. Normal subjects were able to scale and contribute pinch force precisely to a pinch-holding-up test. This study may provide clinicians a reliable apparatus and method to analyze the recovery of functional sensibility in patients with nerve injuries. Copyright 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Compression mechanisms in the plasma focus pinch

NASA Astrophysics Data System (ADS)

Lee, S.; Saw, S. H.; Ali, Jalil

2017-03-01

The compression of the plasma focus pinch is a dynamic process, governed by the electrodynamics of pinch elongation and opposed by the negative rate of change of current dI/dt associated with the current dip. The compressibility of the plasma is influenced by the thermodynamics primarily the specific heat ratio; with greater compressibility as the specific heat ratio γ reduces with increasing degree of freedom f of the plasma ensemble due to ionization energy for the higher Z (atomic number) gases. The most drastic compression occurs when the emitted radiation of a high-Z plasma dominates the dynamics leading in extreme cases to radiative collapse which is terminated only when the compressed density is sufficiently high for the inevitable self-absorption of radiation to occur. We discuss the central pinch equation which contains the basic electrodynamic terms with built-in thermodynamic factors and a dQ/dt term; with Q made up of a Joule heat component and absorption-corrected radiative terms. Deuterium is considered as a thermodynamic reference (fully ionized perfect gas with f = 3) as well as a zero-radiation reference (bremsstrahlung only; with radiation power negligible compared with electrodynamic power). Higher Z gases are then considered and regimes of thermodynamic enhancement of compression are systematically identified as are regimes of radiation-enhancement. The code which incorporates all these effects is used to compute pinch radius ratios in various gases as a measure of compression. Systematic numerical experiments reveal increasing severity in radiation-enhancement of compressions as atomic number increases. The work progresses towards a scaling law for radiative collapse and a generalized specific heat ratio incorporating radiation.

Linear Transformer Drivers for Z-pinch Based Propulsion

NASA Technical Reports Server (NTRS)

Adams, Robert; Seidler, William; Giddens, Patrick; Fabisinski, Leo; Cassibry, Jason

2017-01-01

The MSFC/UAH team has been developing of a novel power management and distribution system called a Linear Transformer Driver (LTD). LTD's hold the promise of dramatically reducing the required mass to drive a z-pinch by replacing the capacitor banks which constitute half the mass of the entire system. The MSFC?UAH tea, is developing this technology in hope of integrating it with the Pulsed Fission Fusion (PuFF) propulsion concept. High-Voltage pulsed power systems used for Z-Pinch experimentation have in the past largely been based on Marx Generators. Marx generators deliver the voltage and current required for the Z-Pinch, but suffer from two significant drawbacks when applied to a flight system: they are very massive, consisting of high-voltage capacitor banks insulated in oil-filled tanks and they do not lend themselves to rapid pulsing. The overall goal of Phase 2 is to demonstrate the construction of a higher voltage stack from a number of cavities each of the design proven in Phase 1 and to characterize and understand the techniques for designing the stack. The overall goal of Phase 3 is to demonstrate the feasibility of constructing a higher energy cavity from a number of smaller LTD stacks, to characterize and understand the way in which the constituent stacks combine, and to extend this demonstration LTD to serve as the basis for a 64 kJ pulse generator for Z-Pinch experiments.

Electron density and plasma dynamics of a spherical theta pinch

NASA Astrophysics Data System (ADS)

Teske, C.; Liu, Y.; Blaes, S.; Jacoby, J.

2012-03-01

A spherical theta pinch for plasma stripper applications has been developed and investigated regarding the electron density and the plasma confinement during the pinching sequence. The setup consists of a 6 μH induction coil surrounding a 4000 ml spherical discharge vessel and a capacitor bank with interchangeable capacitors leading to an overall capacitance of 34 μF and 50 μF, respectively. A thyristor switch is used for driving the resonant circuit. Pulsed coil currents reached values of up to 26 kA with maximum induction of 500 mT. Typical gas pressures were 0.7 Pa up to 120 Pa with ArH2 (2.8% H2)-gas as a discharge medium. Stark broadening measurements of the Hβ emission line were carried out in order to evaluate the electron density of the discharge. In accordance with the density measurements, the transfer efficiency was estimated and a scaling law between electron density and discharge energy was established for the current setup. The densities reached values of up to 8 × 1022 m-3 for an energy of 1.6 kJ transferred into the plasma. Further, the pinching of the discharge plasma was documented and the different stages of the pinching process were analyzed. The experimental evidence suggests that concerning the recent setup of the spherical theta pinch, a linear scaling law between the transferred energy and the achievable plasma density can be applied for various applications like plasma strippers and pulsed ion sources.

Ion energy balance in enhanced-confinement reversed-field pinch plasmas

NASA Astrophysics Data System (ADS)

Xing, Z. A.; Nornberg, M. D.; Boguski, J.; Craig, D.; den Hartog, D. J.; McCollam, K.

2017-10-01

Testing the applicability of collisional ion transport theory using tearing suppressed RFP plasma in MST achieved through Pulsed Poloidal Current Drive (PPCD), we find that the ion temperature dynamics in the core to be well-predicted by classical and collisional terms. Prior work demonstrated that impurity ion particle transport in PPCD plasmas is classical. Neoclassical effects on ions in the RFP are small and the stochastic transport is greatly suppressed during PPCD. Recent neutral modelling with DEGAS2 suggests higher core neutral temperatures than expected due to the preferential penetration of higher temperature neutrals generated by charge exchange. Further, investigations through equilibrium reconstruction point to the existence of an inward pinch flow associated with ExB drift. The heat balance model pulls together a wide range of diagnostic data to forward model Ti evolution in PPCD, which is then compared to charge exchange spectroscopy measurements of Ti. Ion power balance is mostly driven by classical effects including compressional heating, electron collisional heating, and charge exchange transport. This understanding provides a good baseline for investigations of anomalous heating in plasmas with tearing mode activity. This work is supported by US DOE.

The Experimental Study of Characterized Noble Gas Puffs Irradiated by Ultra-Short Laser Pulses Compared with X-Pinches as an X-Ray Source

NASA Astrophysics Data System (ADS)

Schultz, Kimberly Ann

measured. Laser beam transmission through and absorption by the gas puff reveal the complexity of using laser-irradiated gas puffs as X-ray sources. A strong anisotropy of X-ray and electron emissions were observed at both laser facilities. X-pinch plasmas can provide intense hard X rays and strong electron beams originating from small sources with many applications. Recent research has been conducted into four-wire X-pinches at the UNR Zebra machine, a 1-MA pulsed power generator. Two different wire materials are considered in this study, Ag and Mo. We observe a relatively linear correlation between load mass and implosion time for Mo X-pinches; in fact, this relationship also extends to include Ag. Interestingly, X-ray burst features drastically change in shape when the load mass is varied. Advantages of laser-irradiated gas puffs include a lack of damaging debris, high repetition rate, and ease of control. Its disadvantages include its inefficiency at converting electrical energy to X-rays, which is mostly limited by laser efficiency, and relatively low total energy yield. X-pinches, on the other hand, produced kJ of energy in a broad spectral region. However, they create a large amount of debris, have a low repetition rate, and, at 1-MA, have hard-to-predict implosion times.

Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivanov, Vladimir V.

Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics,more » magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of

ZaP-HD: High Energy Density Z-Pinch Plasmas using Sheared Flow Stabilization

NASA Astrophysics Data System (ADS)

Golingo, R. P.; Shumlak, U.; Nelson, B. A.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Hughes, M. C.; Kim, B.; Ross, M. P.; Weed, J. R.

2015-11-01

The ZaP-HD flow Z-pinch project investigates scaling the flow Z-pinch to High Energy Density Plasma, HEDP, conditions by using sheared flow stabilization. ZaP used a single power supply to produce 100 cm long Z-pinches that were quiescent for many radial Alfven times and axial flow-through times. The flow Z-pinch concept provides an approach to achieve HED plasmas, which are dimensionally large and persist for extended durations. The ZaP-HD device replaces the single power supply from ZaP with two separate power supplies to independently control the plasma flow and current in the Z-pinch. Equilibrium is determined by diagnostic measurements of the density with interferometry and digital holography, the plasma flow and temperature with passive spectroscopy, the magnetic field with surface magnetic probes, and plasma emission with optical imaging. The diagnostics fully characterize the plasma from its initiation in the coaxial accelerator, through the pinch, and exhaust from the assembly region. The plasma evolution is modeled with high resolution codes: Mach2, WARPX, and NIMROD. Experimental results and scaling analyses are presented. This work is supported by grants from the U.S. Department of Energy and the U.S. National Nuclear Security Administration.

Strength training improves the tri-digit finger-pinch force control of older adults.

PubMed

Keogh, Justin W; Morrison, Steve; Barrett, Rod

2007-08-01

To investigate the effect of unilateral upper-limb strength training on the finger-pinch force control of older men. Pretest and post-test 6-week intervention study. Exercise science research laboratory. Eleven neurologically fit older men (age range, 70-80y). The strength training group (n=7) trained twice a week for 6 weeks, performing dumbbell bicep curls, wrist flexions, and wrists extensions, while the control group subjects (n=4) maintained their normal activities. Changes in force variability, targeting error, peak power frequency, proportional power, sample entropy, digit force sharing, and coupling relations were assessed during a series of finger-pinch tasks. These tasks involved maintaining a constant or sinusoidal force output at 20% and 40% of each subject's maximum voluntary contraction. All participants performed the finger-pinch tasks with both the preferred and nonpreferred limbs. Analysis of covariance for between-group change scores indicated that the strength training group (trained limb) experienced significantly greater reductions in finger-pinch force variability and targeting error, as well as significantly greater increases in finger-pinch force, sample entropy, bicep curl, and wrist flexion strength than did the control group. A nonspecific upper-limb strength-training program may improve the finger-pinch force control of older men.

Multi-scale characterization of an upcurrent turbiditic pinch-out

NASA Astrophysics Data System (ADS)

Daghdevirenian, L. J. P.; Migeon, S.; Rubino, J. L., Sr.; Raisson, F.

2017-12-01

Continental margins with a steep topographic profile between their continental shelf and the basin exhibit a sudden slope break at the base of their continental slope. This slope break favors strong erosion or a by-pass and a fast accumulation of sediments on the base of the continental slope due to the hydraulic jump phenomena. Such a process is responsible for the construction of thick accumulations of limited extension and generally disconnected from the feeding tributaries. These accumulations usually onlap against the continental slope but their modality of pinch out is still questioned and it is the subject of this work. The Tabernas basin is located in South East of Spain, in the continuity of the Sorbas basin. Recent field works allowed identifying a "sedimentary" onlap associated with a small-scale sandy turbidite system that we discovered near the so-called El Buho area. The superb quality of the outcrops revealed, the presence of three successive onlap structures consisting in each case of a direct contact between fluvial conglomerates / marines conglomerates / marine marls / turbidite sands. Reconstruction of paleo-current direction gives a flow direction around N00, from north to south, suggesting the outcrops are cutting the pinch out of the sandy system in a longitudinal direction. A longitudinal and vertical transition of facies can be thus observed from marines' conglomerates to turbidite sands, respectively over distances of 500 m and 70 m. The complete evolution of facies along the pinch out consists of thick conglomerates in the proximal part to sandy turbidite channels then lobes in the distal part. The three successive onlap structures are located inside the channelize part of the system, just above a slope break structure. The basal units of the pinch out consist of an alternation of conglomerates and sandy bed, while the overlying units exhibits more sandy dominated beds. In order to reconstruct the architecture of the pinch out and to

Controlling bridging and pinching with pixel-based mask for inverse lithography

NASA Astrophysics Data System (ADS)

Kobelkov, Sergey; Tritchkov, Alexander; Han, JiWan

2016-03-01

Inverse Lithography Technology (ILT) has become a viable computational lithography candidate in recent years as it can produce mask output that results in process latitude and CD control in the fab that is hard to match with conventional OPC/SRAF insertion approaches. An approach to solving the inverse lithography problem as a nonlinear, constrained minimization problem over a domain mask pixels was suggested in the paper by Y. Granik "Fast pixel-based mask optimization for inverse lithography" in 2006. The present paper extends this method to satisfy bridging and pinching constraints imposed on print contours. Namely, there are suggested objective functions expressing penalty for constraints violations, and their minimization with gradient descent methods is considered. This approach has been tested with an ILT-based Local Printability Enhancement (LPTM) tool in an automated flow to eliminate hotspots that can be present on the full chip after conventional SRAF placement/OPC and has been applied in 14nm, 10nm node production, single and multiple-patterning flows.

Effect of driver impedance on dense plasma focus Z-pinch neutron yield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sears, Jason, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Link, Anthony, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov; Schmidt, Andrea, E-mail: sears8@llnl.gov, E-mail: schmidt36@llnl.gov

2014-12-15

The Z-pinch phase of a dense plasma focus (DPF) heats the plasma by rapid compression and accelerates ions across its intense electric fields, producing neutrons through both thermonuclear and beam-target fusion. Driver characteristics have empirically been shown to affect performance, as measured by neutron yield per unit of stored energy. We are exploring the effect of driver characteristics on DPF performance using particle-in-cell (PIC) simulations of a kJ scale DPF. In this work, our PIC simulations are fluid for the run-down phase and transition to fully kinetic for the pinch phase, capturing kinetic instabilities, anomalous resistivity, and beam formation duringmore » the pinch. The anode-cathode boundary is driven by a circuit model of the capacitive driver, including system inductance, the load of the railgap switches, the guard resistors, and the coaxial transmission line parameters. It is known that the driver impedance plays an important role in the neutron yield: first, it sets the peak current achieved at pinch time; and second, it affects how much current continues to flow through the pinch when the pinch inductance and resistance suddenly increase. Here we show from fully kinetic simulations how total neutron yield depends on the impedance of the driver and the distributed parameters of the transmission circuit. Direct comparisons between the experiment and simulations enhance our understanding of these plasmas and provide predictive design capability for neutron source applications.« less

Normative Measurements of Grip and Pinch Strengths of 21st Century Korean Population

PubMed Central

Shim, Jin Hee; Kim, Jin Soo; Lee, Dong Chul; Ki, Sae Hwi; Yang, Jae Won; Jeon, Man Kyung; Lee, Sang Myung

2013-01-01

Background Measuring grip and pinch strength is an important part of hand injury evaluation. Currently, there are no standardized values of normal grip and pinch strength among the Korean population, and lack of such data prevents objective evaluation of post-surgical recovery in strength. This study was designed to establish the normal values of grip and pinch strength among the healthy Korean population and to identify any dependent variables affecting grip and pinch strength. Methods A cross-sectional study was carried out. The inclusion criterion was being a healthy Korean person without a previous history of hand trauma. The grip strength was measured using a Jamar dynamometer. Pulp and key pinch strength were measured with a hydraulic pinch gauge. Intra-individual and inter-individual variations in these variables were analyzed in a standardized statistical manner. Results There were a total of 336 healthy participants between 13 and 77 years of age. As would be expected in any given population, the mean grip and pinch strength was greater in the right hand than the left. Male participants (137) showed mean strengths greater than female participants (199) when adjusted for age. Among the male participants, anthropometric variables correlated positively with grip strength, but no such correlations were identifiable in female participants in a statistically significant way. Conclusions Objective measurements of hand strength are an important component of hand injury evaluation, and population-specific normative data are essential for clinical and research purposes. This study reports updated normative hand strengths of the South Korean population in the 21st century. PMID:23362480

Pinched-flow hydrodynamic stretching of single-cells.

PubMed

Dudani, Jaideep S; Gossett, Daniel R; Tse, Henry T K; Di Carlo, Dino

2013-09-21

Reorganization of cytoskeletal networks, condensation and decondensation of chromatin, and other whole cell structural changes often accompany changes in cell state and can reflect underlying disease processes. As such, the observable mechanical properties, or mechanophenotype, which is closely linked to intracellular architecture, can be a useful label-free biomarker of disease. In order to make use of this biomarker, a tool to measure cell mechanical properties should accurately characterize clinical specimens that consist of heterogeneous cell populations or contain small diseased subpopulations. Because of the heterogeneity and potential for rare populations in clinical samples, single-cell, high-throughput assays are ideally suited. Hydrodynamic stretching has recently emerged as a powerful method for carrying out mechanical phenotyping. Importantly, this method operates independently of molecular probes, reducing cost and sample preparation time, and yields information-rich signatures of cell populations through significant image analysis automation, promoting more widespread adoption. In this work, we present an alternative mode of hydrodynamic stretching where inertially-focused cells are squeezed in flow by perpendicular high-speed pinch flows that are extracted from the single inputted cell suspension. The pinched-flow stretching method reveals expected differences in cell deformability in two model systems. Furthermore, hydraulic circuit design is used to tune stretching forces and carry out multiple stretching modes (pinched-flow and extensional) in the same microfluidic channel with a single fluid input. The ability to create a self-sheathing flow from a single input solution should have general utility for other cytometry systems and the pinched-flow design enables an order of magnitude higher throughput (65,000 cells s(-1)) compared to our previously reported deformability cytometry method, which will be especially useful for identification of rare

PINCHED PLASMA REACTOR

DOEpatents

Phillips, J.A.; Suydam, R.; Tuck, J.L.

1961-07-01

BS>A plasma confining and heating reactor is described which has the form of a torus with a B/sub 2/ producing winding on the outside of the torus and a helical winding of insulated overlapping tunns on the inside of the torus. The inner helical winding performs the double function of shielding the plasma from the vitreous container and generating a second B/sub z/ field in the opposite direction to the first B/sub z/ field after the pinch is established.

Self-pinched transport for ion-driven inertial confinement fusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welch, D.R.; Olson, C.L.

Efficient transport of intense ion beams is necessary for ion-driven inertial confinement fusion (ICF). The self-pinched transport scheme involves the focusing of an ion beam to a radius of about 1 cm or less. At this radius, using the beam`s self-magnetic field for confinement, the ion beam propagates through the reactor chamber to an ICF target. A promising regime for self-pinched transport involves the injection of a high current beam into an initially neutral gas at about 200 mTorr less. A simple equilibrium theory of a beam with a temporally pinching radial envelope predicts that large confining magnetic fields aremore » possible with net currents of more than 50% of the beam current. The magnitude of these fields is strongly dependent on the rate of ionization of the given ion species. The authors have simulated ion-beam propagation, using the hybrid code IPROP, which self-consistently calculates the gas breakdown and electromagnetic fields. In agreement, with the theory, a propagation window of 20-200 mTorr of argon is calculated for a 50 kA, 5 MeV proton beam similar to the parameters of the SABRE accelerator at Sandia National Laboratories. The authors present simulations of the focusing and propagation of the SABRE beam, with the purpose of designing a self-pinch experiment.« less

Impact of grain size evolution on necking and pinch-and-swell formation in calcite layers

NASA Astrophysics Data System (ADS)

Schmalholz, Stefan Markus; Duretz, Thibault

2017-04-01

The formation of necking zones and the associated formation of pinch-and-swell structure is one form of strain localization in extending, competent layers. Natural pinch-and-swell structure in centimetre-thick calcite layers typically shows a reduction of grain size from swell towards pinch. However, the impact of grain size evolution on necking and pinch-and-swell formation is incompletely understood. We perform zero-dimensional (0D) and 2D thermo-mechanical numerical simulations to quantify the impact of grain size evolution on necking for extension rates between 10-12s^-1and10^-14 s-1 and temperatures around 350°C. For a combination of diffusion and dislocation creep we calculate grain size evolution according to the paleowattmeter (grain size is proportional to mechanical work rate) or the paleopiezometer (grain size is proportional to stress). Numerical results fit two observations: (i) grain size reduction from swells towards pinches, and (ii) dislocation creep dominated deformation in swells and significant contribution of diffusion creep in pinches. Modelled grain size in pinches (10 to 60 μm) and swells (70 to 800 μm) is close to observed grain size in pinches (15 to 27 μm) and in swells (250 to 1500 μm). Grain size evolution has only a minor impact on necking suggesting that grain size evolution is a consequence, and not the cause of necking. Viscous shear heating and grain size evolution had a negligible thermal impact in the simulations.

Toggle mechanism for pinching metal tubes

NASA Technical Reports Server (NTRS)

Stengard, E. O. (Inventor)

1979-01-01

A toggle mechanism pinches a metal tube and maintains the tube in a pinched condition, without fracturing. The toggle mechanism includes a plunger translatable along a longitudinal axis, as well as a pair of links pivoted about a common axis extending through an end of the plunger. One of the links also pivots about a fixed axis. A free end of the other link carries a push link which the other link translates at right angles to the plunger longitudinal axis. First and second sides of the tube bear against a first stop block and are engaged by the push link when a compression spring, attached to the plunger, is suddenly released to irreversibly drive the plunger along its longitudinal axis so the pivot point of the two links is driven to an over travel position.

Charge order-superfluidity transition in a two-dimensional system of hard-core bosons and emerging domain structures

NASA Astrophysics Data System (ADS)

Moskvin, A. S.; Panov, Yu. D.; Rybakov, F. N.; Borisov, A. B.

2017-11-01

We have used high-performance parallel computations by NVIDIA graphics cards applying the method of nonlinear conjugate gradients and Monte Carlo method to observe directly the developing ground state configuration of a two-dimensional hard-core boson system with decrease in temperature, and its evolution with deviation from a half-filling. This has allowed us to explore unconventional features of a charge order—superfluidity phase transition, specifically, formation of an irregular domain structure, emergence of a filamentary superfluid structure that condenses within of the charge-ordered phase domain antiphase boundaries, and formation and evolution of various topological structures.

Conformity of modified O-ring test and maximal pinch strength for cross tape application direction.

PubMed

Lee, Jung-Hoon; Choi, Hyun-Su

2018-06-01

Although cross tape has recently been used by clinicians for various musculoskeletal conditions, scientific studies on the direction of cross tape application are lacking. The present study aimed to investigate whether the direction of cross tape application affected the outcomes of the modified O-ring test and maximal pinch strength using a pinch gauge and the conformity between these 2 tests when cross tape was applied to the forearm muscles of individuals with no upper extremity pain and no restriction of joint range of motion.This study used a single-blinding crossover design. The subjects comprised 39 adults (16 men and 23 women). Cross tape was applied to the dominant hand so that the 4 rows were at an angle of 45° to the right or left of the direction of the flexor digitorum superficialis muscle fibers, and then the subjects underwent a modified O-ring test and a test of maximal pinch strength using a pinch gauge. Both tests were performed in both directions, and the order of the directions and tests was randomized. SPSS 18.0 was used for statistical analysis. Cohen's kappa coefficient was used to analyze the conformity of the results from the 2 tests. The statistical significance level was P < .05. A positive response in the modified O-ring test and maximal pinch strength were both affected by cross tape direction. The modified O-ring test and maximal pinch strength using pinch gauge results were in agreement (P < .00), and the kappa coefficient was significant at 1.00. The direction of cross tape application that produced a positive response in the modified O-ring test also produced greater maximal pinch strength. Thus, we propose that when applying cross tape to muscles, the direction of the 4 lines of the cross tape should be 45° relative to the direction of the muscle fibers, toward the side that produces a positive response in the modified O-ring test or produces the greatest maximal pinch strength using a pinch gauge.

The quest for a z-pinch based fusion energy source—a historical perspective

NASA Astrophysics Data System (ADS)

Sethian, John

1997-05-01

Ever since 1958, when Oscar Anderson observed copious neutrons emanating from a "magnetically self-constricted column of deuterium plasma," scientists have attempted to develop the simple linear pinch into a fusion power source. After all, simple calculations show that if one can pass a current of slightly less than 2 million amperes through a stable D-T plasma, then one could achieve not just thermonuclear break-even, but thermonuclear gain. Moreover, several reactor studies have shown that a simple linear pinch could be the basis for a very attractive fusion system. The problem is, of course, that the seemingly simple act of passing 2 MA through a stable pinch has proven to be quite difficult to accomplish. The pinch tends to disrupt due to instabilities, either by the m=0 (sausage) or m=1 (kink) modes. Curtailing the growth of these instabilities has been the primary thrust of z-pinch fusion research, and over the years a wide variety of formation techniques have been tried. The early pinches were driven by relatively slow capacitive discharges and were formed by imploding a plasma column. The advent of fast pulsed power technology brought on a whole new repertoire of formation techniques, including: fast implosions, laser or field-enhanced breakdown in a uniform volume of gas, a discharge inside a small capillary, a frozen deuterium fiber isolated by vacuum, and staged concepts in which one pinch implodes upon another. And although none of these have yet to be successful, some have come tantalizingly close. This paper will review the history of this four-decade long quest for fusion power.

Core/corona modeling of diode-imploded annular loads

NASA Astrophysics Data System (ADS)

Terry, R. E.; Guillory, J. U.

1980-11-01

The effects of a tenuous exterior plasma corona with anomalous resistivity on the compression and heating of a hollow, collisional aluminum z-pinch plasma are predicted by a one-dimensional code. As the interior ("core") plasma is imploded by its axial current, the energy exchange between core and corona determines the current partition. Under the conditions of rapid core heating and compression, the increase in coronal current provides a trade-off between radial acceleration and compression, which reduces the implosion forces and softens the pitch. Combined with a heuristic account of energy and momentum transport in the strongly coupled core plasma and an approximate radiative loss calculation including Al line, recombination and Bremsstrahlung emission, the current model can provide a reasonably accurate description of imploding annular plasma loads that remain azimuthally symmetric. The implications for optimization of generator load coupling are examined.

Comparison of grip and pinch strength in young women with and without hyperkyphosis: A cross-sectional study.

PubMed

Yoosefinejad, Amin Kordi; Ghaffarinejad, Farahnaz; Hemati, Mahbubeh; Jamshidi, Narges

2018-05-21

Hyperkyphosis is a common postural defect with high prevalence in the 20 to 50 year old population. It appears to compromise proximal scapular stability. Grip and pinch strength are used to evaluate general upper extremity function. The aim of this study was to compare pinch and grip strength between young women with and without hyperkyphosis. Thirty young women (18-40 years old) with hyperkyphosis and 30 healthy women matched for age and body mass index participated in the study. Hyperkyphosis was confirmed by measuring the kyphosis angle with a flexible ruler. Grip strength was measured with the Waisa method and a dynamometer. Pinch strength was assessed with a pinch meter. Grip (P= 0.03) and pinch strength (P= 0.04) were significantly lower in women with hyperkyphosis compared to the control group. Kyphosis angle correlated weakly with grip (r= 0.26) and pinch strength (r= 0.23). Hyperkyphotic posture has led to decreased grip and pinch strength compared to people without hyperkyphosis.

Radial and Azimuthal Velocity Profiles in Gas-Puff Z-Pinches

NASA Astrophysics Data System (ADS)

Rocco, Sophia; Engelbrecht, Joseph; Banasek, Jacob; de Grouchy, Philip; Qi, Niansheng; Hammer, David

2016-10-01

The dynamics of neon, argon, and krypton (either singly or in combination) gas puff z-pinch plasmas are studied on Cornell's 1MA, 100-200ns rise-time COBRA pulsed power generator. The triple-nozzle gas puff valve, consisting of two annular gas puffs and a central jet, allows radial tailoring of the gas puff mass-density profile and the use of 1, 2 or 3 different gases at different pressures. Interferometry supplies information on sheath thickness and electron density, variously filtered PCDs and silicon diodes measure hard and soft x-ray production, and multi frame visible and extreme UV imaging systems allow tracking of the morphology of the plasma. A 527nm, 10J Thomson scattering diagnostic system is used to determine radial and azimuthal velocities. Implosion velocities of 170km/s (Kr) and 300km/s (Ne/Ar) are observed. We are investigating the correlations between instability growth, plasma density profile, velocity partitioning as a function of radius, and radiation production. Research supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement No. DE-NA0001836.

The design and implementation of a windowing interface pinch force measurement system

NASA Astrophysics Data System (ADS)

Ho, Tze-Yee; Chen, Yuanu-Joan; Chung, Chin-Teng; Hsiao, Ming-Heng

2010-02-01

This paper presents a novel windowing interface pinch force measurement system that is basically based on an USB (Universal Series Bus) microcontroller which mainly processes the sensing data from the force sensing resistance sensors mounted on five digits. It possesses several friendly functions, such as the value and curve trace of the applied force by a hand injured patient displayed in real time on a monitoring screen, consequently, not only the physician can easily evaluate the effect of hand injury rehabilitation, but also the patients get more progressive during the hand physical therapy by interacting with the screen of pinch force measurement. In order to facilitate the pinch force measurement system and make it friendly, the detail hardware design and software programming flowchart are described in this paper. Through a series of carefully and detailed experimental tests, first of all, the relationship between the applying force and the FSR sensors are measured and verified. Later, the different type of pinch force measurements are verified by the oscilloscope and compared with the corresponding values and waveform traces in the window interface display panel to obtain the consistency. Finally, a windowing interface pinch force measurement system based on the USB microcontroller is implemented and demonstrated. The experimental results show the verification and feasibility of the designed system.

Properties of the edge plasma in the rebuilt Extrap-T2R reversed field pinch experiment

NASA Astrophysics Data System (ADS)

Vianello, N.; Spolaore, M.; Serianni, G.; Bergsåker, H.; Antoni, V.; Drake, J. R.

2002-12-01

The edge region of the rebuilt Extrap-T2R reversed field pinch experiment has been investigated using Langmuir probes. Radial profiles of main plasma parameters are obtained and compared with those of the previous device Extrap-T2. The spontaneous setting up of a double shear layer of E×B toroidal velocity is confirmed. The particle flux induced by electrostatic fluctuations is calculated and the resulting effective diffusion coefficient is consistent with the Bohm estimate. A close relationship between electrostatic fluctuations at the edge and non-linear coupling of MHD modes in the core is found.

Pinch-force-magnification mechanism of low degree of freedom EMG prosthetic hand for children.

PubMed

Ye, Hesong; Sakoda, Shintaro; Jiang, Yinlai; Morishita, Soichiro; Yokoi, Hiroshi

2015-01-01

EMG prosthetic hands are being extensively studied for the disabled who need them not only for cosmesis but also for the functions to help them with basic daily activities. However, most EMG prosthetic hands are developed for adults. Since the early use of prosthetic hands is important for the children to accept and adapt to them, we are developing low degrees of freedom (DoF) prosthetic hand that is suitable for children. Due to the limited size of a child's hand, the servo motor which drives the MP joint are small-sized and low-power. Hence, a pinch-force-magnification mechanism is required to improve the pinch force of the EMG prosthetic hand. In this paper we designed a wire-driven mechanism which can magnify pinch force by increasing the length of the MP joint's moment arm. Pinch force measurement experiment validated that the pinch force of the prosthetic hand with the mechanism is more than twice of that of the hand with direct drive.

Reynolds stress flow shear and turbulent energy transfer in reversed field pinch configuration

NASA Astrophysics Data System (ADS)

Vianello, Nicola; Spolaore, Monica; Serianni, Gianluigi; Regnoli, Giorgio; Spada, Emanuele; Antoni, Vanni; Bergsåker, Henric; Drake, James R.

2003-10-01

The role of Reynolds Stress tensor on flow generation in turbulent fluids and plasmas is still an open question and the comprehension of its behavior may assist the understanding of improved confinement scenario. It is generally believed that shear flow generation may occur by an interaction of the turbulent Reynolds stress with the shear flow. It is also generally believed that this mechanism may influence the generation of zonal flow shears. The evaluation of the complete Reynolds Stress tensor requires contemporary measurements of its electrostatic and magnetic part: this requirement is more restrictive for Reversed Field Pinch configuration where magnetic fluctuations are larger than in tokamak . A new diagnostic system which combines electrostatic and magnetic probes has been installed in the edge region of Extrap-T2R reversed field pinch. With this new probe the Reynolds stress tensor has been deduced and its radial profile has been reconstructed on a shot to shot basis exploring differen plasma conditions. These profiles have been compared with the naturally occurring velocity flow profile, in particular during Pulsed Poloidal Current Drive experiment, where a strong variation of ExB flow radial profile has been registered. The study of the temporal evolution of Reynolds stress reveals the appearance of strong localized bursts: these are considered in relation with global MHD relaxation phenomena, which naturally occur in the core of an RFP plasma sustaining its configuration.

First-order finite-Larmor-radius fluid modeling of tearing and relaxation in a plasma pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

King, J. R.; Tech-X Corporation, 5621 Arapahoe Ave., Suite A Boulder, Colorado 80303; Sovinec, C. R.

Drift and Hall effects on magnetic tearing, island evolution, and relaxation in pinch configurations are investigated using a non-reduced first-order finite-Larmor-radius (FLR) fluid model with the nonideal magnetohydrodynamics (MHD) with rotation, open discussion (NIMROD) code [C.R. Sovinec and J. R. King, J. Comput. Phys. 229, 5803 (2010)]. An unexpected result with a uniform pressure profile is a drift effect that reduces the growth rate when the ion sound gyroradius ({rho}{sub s}) is smaller than the tearing-layer width. This drift is present only with warm-ion FLR modeling, and analytics show that it arises from {nabla}B and poloidal curvature represented in themore » Braginskii gyroviscous stress. Nonlinear single-helicity computations with experimentally relevant {rho}{sub s} values show that the warm-ion gyroviscous effects reduce saturated-island widths. Computations with multiple nonlinearly interacting tearing fluctuations find that m = 1 core-resonant-fluctuation amplitudes are reduced by a factor of two relative to single-fluid modeling by the warm-ion effects. These reduced core-resonant-fluctuation amplitudes compare favorably to edge coil measurements in the Madison Symmetric Torus (MST) reversed-field pinch [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. The computations demonstrate that fluctuations induce both MHD- and Hall-dynamo emfs during relaxation events. The presence of a Hall-dynamo emf implies a fluctuation-induced Maxwell stress, and the simulation results show net transport of parallel momentum. The computed magnitude of force densities from the Maxwell and competing Reynolds stresses, and changes in the parallel flow profile, are qualitatively and semi-quantitatively similar to measurements during relaxation in MST.« less

Hydrodynamic mode associated with the pinch flow in RFP simulations

NASA Astrophysics Data System (ADS)

Delzanno, Gian Luca; Chacon, Luis; Finn, John

2007-11-01

We present a systematic study of single helicity (SH) states and quasi-single helicity (QSH) states in RFPs. We begin with cylindrical paramagnetic pinch equilibria with uniform resistivity, characterized by a single dimensionless parameter proportional to the toroidal electric field, or the RFP toroidal current parameter θ. For sufficiently high θ, there are several unstable m=1 ideal MHD instabilities, typically one of which is nonresonant, with 1/n just above q(r=0). We evolve these modes nonlinearly to saturation for low Hartmann number H. We show the existence of a new class of unstable modes [1], besides the electromagnetic kink modes typically responsible for the reversal of the axial magnetic field at the edge in RFPs. This new instability is hydrodynamic in nature and is due to the inward equilibrium pinch flow and suitable boundary conditions. In these circumstances, the total angular momentum of the system must grow in response to the flux of particles coming from the boundary. The hydrodynamic mode dominates the nonlinear phase of the velocity field but has little effect on the dynamics of the magnetic field. [1] G.L. Delzanno, L. Chac'on, J.M. Finn, Hydrodynamic mode associated with the pinch flow in Reversed Field Pinch simulations, submitted (2007).

Designs and Plans for MAIZE: a 1 MA LTD-Driven Z-Pinch

NASA Astrophysics Data System (ADS)

Gilgenbach, R. M.; Gomez, M. R.; Zier, J.; Tang, W.; French, D. M.; Hoff, B. W.; Jordan, N.; Cruz, E.; Lau, Y. Y.; Fowler-Guzzardo, T.; Meisel, J.; Mazarakis, M. G.; Cuneo, M. E.; Johnston, M. D.; Mehlhorn, T. A.; Kim, A. A.; Sinebryukhov, V. A.

2007-11-01

We present designs and experimental plans of the first 1 MA z-pinch in the USA to be driven by a Linear Transformer Driver (LTD). The Michigan Accelerator for Inductive Z-pinch Experiments, (MAIZE), is based on the LTD developed at the Institute for High Current Electronics, utilizing 80 capacitors and 40 spark gap switches to deliver a 1 MA, 100 kV pulse with <100 ns risetime. Designs will be presented of a low-inductance MITL terminated in a wire-array z-pinch. Initial, planned experiments will evaluate the LTD driving time-changing inductance of imploding 4-16 wire-array z-pinches. Wire ablation dynamics, axial-correlations and instability development will be explored. *This work was supported by U. S. DoE through Sandia National Laboratories award number 240985 to the University of Michigan. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Simulation of the radiation from the hot spot of an X-pinch

NASA Astrophysics Data System (ADS)

Oreshkin, V. I.; Artyomov, A. P.; Chaikovsky, S. A.; Oreshkin, E. V.; Rousskikh, A. G.

2017-01-01

The results of X-pinch experiments performed using a small-sized pulse generator are analyzed. The generator, capable of producing a 200-kA, 180-ns current, was loaded with an X-pinch made of four 35-μm-diameter aluminum wires. The analysis consists of a one-dimensional radiation magnetohydrodynamic simulation of the formation of a hot spot in an X-pinch, taking into account the outflow of material from the neck region. The radiation loss and the ion species composition of the pinch plasma are calculated based on a stationary collisional-radiative model, including balance equations for the populations of individual levels. With this model, good agreement between simulation predictions and experimental data has been achieved: the experimental and the calculated radiation power and pulse duration differ by no more than twofold. It has been shown that the x-ray pulse is formed in the radiative collapse region, near its boundary.

Magnetic pinch compression of silica glass

NASA Technical Reports Server (NTRS)

Bless, S. J.

1974-01-01

SiO2 glass has been irreversibly densified by pressures up to 250 kbar produced in a magnetic pinch apparatus. The threshold for significant densification was about 60 kbar. The recovered densities agree better with published shock wave results than with static results.

Self-Pinched Transport Theory for the SABRE Ion Diode

NASA Astrophysics Data System (ADS)

Welch, Dale R.; Olson, Craig L.; Hanson, David L.

1997-05-01

In anticipation of a 90 kA 4 MV SABRE ion diode experiment, we have been examining self-pinch transport of ions for application to ion-driven inertial confinement fusion. The Li^+3 beam will exit the diode with a 30-40 mradian divergence and a shallow focusing angle of 75 mradians. The beam is annular with an 4.6-cm inner radius and a 6.8-cm outer radius. Self-pinch theory and simulation predict that large residual currents are possible in 2-20 mtorr argon gas. The simulations suggest that ≈ 50 kA of Li particle current is necessary to contain the beam's transverse momentum. Some non-ideal effects include large beam divergence, large focusing angle and beam annularity. To address these problems, we have been studying the benefits of beam conditioning in the focus region between the diode and the self pinch region after the beam has reached a small radius. We have found some benefit from including a passive conical structure and a low-pressure gas. A significant lens effect can be attained using only the beam fields in vacuum or a low pressure gas. In this configuration, a large focusing force, that keeps the ions off an inner cone and outer wall as the beam converges, has been calculated using the numerical simulation code uc(iprop.) Results from integrated simulation of the condition cell and self-pinch region look encouraging.

Alpha effect of Alfv{acute e}n waves and current drive in reversed-field pinches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Litwin, C.; Prager, S.C.

Circularly polarized Alfv{acute e}n waves give rise to an {alpha}-dynamo effect that can be exploited to drive parallel current. In a {open_quotes}laminar{close_quotes} magnetic the effect is weak and does not give rise to significant currents for realistic parameters (e.g., in tokamaks). However, in reversed-field pinches (RFPs) in which magnetic field in the plasma core is stochastic, a significant enhancement of the {alpha} effect occurs. Estimates of this effect show that it may be a realistic method of current generation in the present-day RFP experiments and possibly also in future RFP-based fusion reactors. {copyright} {ital 1998 American Institute of Physics.}

Review of effects of dielectric coatings on electrical exploding wires and Z pinches

NASA Astrophysics Data System (ADS)

Wu, Jian; Li, Xingwen; Li, Mo; Li, Yang; Qiu, Aici

2017-10-01

As the most powerful x-ray source in the laboratories, the wire array Z pinches have been of great relevance to inertial confinement fusions, laboratory astrophysics, and other high-energy density applications. In order to produce x-ray with greater power and higher efficiency, the dynamics of wire array has been investigated extensively, and various methods have been proposed to improve the implosion quality of the wire array. This review focuses on the experimental and theoretical investigations regarding the effects of the dielectric coatings on electrical exploding wires and Z pinches. Since the early 2000, the electrical wire explosion related to the first stage of the wire array Z pinches has been studied extensively, and the results indicated that the dielectric coatings can significantly increase the joule energy deposition into a wire in the initial stage, and even the corona free explosion of tungsten wires can be achieved. Recently, there is an increasing interest in the dynamics of insulated wire array Z pinches. By applying dielectric coatings, the ablation process is suppressed, the x-ray start time is delayed, and the possibility of multi-peak radiation is decreased. This review is organized by the evolution dynamics of wire array Z pinches, and a broad introduction to relevant scientific concepts and various other applications are presented. According to the current research status, the challenges, opportunities and further developments of Z pinch loads using dielectric coatings are proposed to further promote the researches and their applications.

Z-Pinch fusion-based nuclear propulsion

NASA Astrophysics Data System (ADS)

Miernik, J.; Statham, G.; Fabisinski, L.; Maples, C. D.; Adams, R.; Polsgrove, T.; Fincher, S.; Cassibry, J.; Cortez, R.; Turner, M.; Percy, T.

2013-02-01

Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human space flight missions. The Z-Pinch dense plasma focus method is a Magneto-Inertial Fusion (MIF) approach that may potentially lead to a small, low cost fusion reactor/engine assembly [1]. Recent advancements in experimental and theoretical understanding of this concept suggest favorable scaling of fusion power output yield [2]. The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this process can be pulsed over short timescales (10-6 s). This type of plasma formation is widely used in the field of Nuclear Weapons Effects testing in the defense industry, as well as in fusion energy research. A Z-Pinch propulsion concept was designed for a vehicle based on a previous fusion vehicle study called "Human Outer Planet Exploration" (HOPE), which used Magnetized Target Fusion (MTF) [3] propulsion. The reference mission is the transport of crew and cargo to Mars and back, with a reusable vehicle. The analysis of the Z-Pinch MIF propulsion system concludes that a 40-fold increase of Isp over chemical propulsion is predicted. An Isp of 19,436 s and thrust of 3812 N s/pulse, along with nearly doubling the predicted payload mass fraction, warrants further development of enabling technologies.

Results of core drilling for uranium-bearing lignites in the Bar H area, Slim Buttes, Harding County, South Dakota

USGS Publications Warehouse

Zeller, Howard D.

1953-01-01

Core drilling in the Car H area, Slim Buttes, Harding County, South Dakota, under a contract with the B. H. Mott Drilling Co., Huntington, West Virginia, was resumed June 12, 1952 after a 6-month recess during the winter and was completed July 18, 1952. The drilling was undertaken to obtain information on the distribution and extent of the uranium-bearing lignite beds along the southeast edge of the Bar H area. Eight holes totalling 885 feet were drilled and 52 feet of lignite core submitted for study and analysis. The report includes detailed lithographic descriptions of the lignite cores, Bureau of Mines coal analyses, and the results of 100 chemical analyses for uranium. The drilling showed that the thicker, more persistent lignite beds exposed in the northern part of the Bar H area were removed by erosion prior to the deposition of the overlaying White River formation in the south-eastern part of the area. The beds penetrated by drilling were not of sufficient thickness or uranium content to add to the previously known reserves.

High energy density Z-pinch plasmas using flow stabilization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shumlak, U., E-mail: shumlak@uw.edu; Golingo, R. P., E-mail: shumlak@uw.edu; Nelson, B. A., E-mail: shumlak@uw.edu

The ZaP Flow Z-Pinch research project[1] at the University of Washington investigates the effect of sheared flows on MHD instabilities. Axially flowing Z-pinch plasmas are produced that are 100 cm long with a 1 cm radius. The plasma remains quiescent for many radial Alfvén times and axial flow times. The quiescent periods are characterized by low magnetic mode activity measured at several locations along the plasma column and by stationary visible plasma emission. Plasma evolution is modeled with high-resolution simulation codes – Mach2, WARPX, NIMROD, and HiFi. Plasma flow profiles are experimentally measured with a multi-chord ion Doppler spectrometer. Amore » sheared flow profile is observed to be coincident with the quiescent period, and is consistent with classical plasma viscosity. Equilibrium is determined by diagnostic measurements: interferometry for density; spectroscopy for ion temperature, plasma flow, and density[2]; Thomson scattering for electron temperature; Zeeman splitting for internal magnetic field measurements[3]; and fast framing photography for global structure. Wall stabilization has been investigated computationally and experimentally by removing 70% of the surrounding conducting wall to demonstrate no change in stability behavior.[4] Experimental evidence suggests that the plasma lifetime is only limited by plasma supply and current waveform. The flow Z-pinch concept provides an approach to achieve high energy density plasmas,[5] which are large, easy to diagnose, and persist for extended durations. A new experiment, ZaP-HD, has been built to investigate this approach by separating the flow Z-pinch formation from the radial compression using a triaxial-electrode configuration. This innovation allows more detailed investigations of the sheared flow stabilizing effect, and it allows compression to much higher densities than previously achieved on ZaP by reducing the linear density and increasing the pinch current. Experimental results

Comparative study of millennials' (age 20-34 years) grip and lateral pinch with the norms.

PubMed

Fain, Elizabeth; Weatherford, Cara

Cross-sectional research design. Clinical practice continues to use normative data for grip and pinch measurements that were established in 1985. There is no updated norms despite different hand usage patterns in today's society. Measuring and comparing grip and pinch strengths with normative data is a valid method to determine hand function. This research was implemented to compare the grip and pinch measurements obtained from healthy millennials to the established norms and to describe hand usage patterns for millennials. Grip and lateral pinch measurements were obtained from a sample of 237 healthy millennials (ages 20-34 years). Strength scores were statistically lower that older normative data in all millennial grip strengths, with the exception of the women in the age group of 30-34 years. Specifically, this statistically significant trend was observed in all male grip strengths, as well as in women in the age group of 20-24 years (bilateral grip) and 25-29 years (right grip). However, the lateral pinch data reflected was similar to the older norms with variances of 0.5-1 kg. Current data reflect statistically significant differences from the norms for all male grip measurements, as well as for women in the age group of 20-24 years (bilateral grip) and 25-29 years (right grip). No statistical significance was observed in the independent-sample t tests for the lateral pinch in men of all age groups. Statistical significance was noted for lateral pinch for female age groups for the left hand (20-24 years) and for bilateral lateral pinches (30-34 years). IV. Copyright © 2016 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

Short-term hot-hardness characteristics of five case hardened steels

NASA Technical Reports Server (NTRS)

Anderson, N. E.; Zaretsky, E. V.

1975-01-01

Short-term hot-hardness studies were performed with carburized and hardened AISI 8620, CBS 1000, CBS 1000M, CBS 600, and Vasco X-2 steels. Case and core hardness measurements were made at temperatures from 294 to 811 K (70 to 1000 F). The data were compared with data for high-speed tool steels and AISI 52100. The materials tested can be ranked as follows in order of decreasing hot-hardness retention: (1) Vasco X-2; equivalent to through-hardened tool steels up to 644 K (700 F) above which Vasco X-2 is inferior; (2) CBS 1000, (3) CBS 1000M; (4) CBS 6000; better hardness retention at elevated temperatures than through-hardened AISI 52100; and (5) AISI 8620. For the carburized steels, the change in hardness with temperature of the case and core are similar for a given material. The short-term hot hardness of these materials can be predicted with + or - 1 point Rockwell C.

Functional sensibility assessment. Part II: Effects of sensory improvement on precise pinch force modulation after transverse carpal tunnel release.

PubMed

Hsu, Hsiu-Yun; Kuo, Li-Chieh; Chiu, Haw-Yen; Jou, I-Ming; Su, Fong-Chin

2009-11-01

Patients with median nerve compression at the carpal tunnel often have poor sensory afferents. Without adequate sensory modulation control, these patients frequently exhibit clumsy performance and excessive force output in the affected hand. We analyzed precision grip function after the sensory recovery of patients with carpal tunnel syndrome (CTS) who underwent carpal tunnel release (CTR). Thirteen CTS patients were evaluated using a custom-designed pinch device and conventional sensory tools before and after CTR to measure sensibility, maximum pinch strength, and anticipated pinch force adjustments to movement-induced load fluctuations in a pinch-holding-up activity. Based on these tests, five force-related parameters and sensory measurements were used to determine improvements in pinch performance after sensory recovery. The force ratio between the exerted pinch force and maximum load force of the lifting object was used to determine pinch force coordination and to prove that CTR enabled precision motor output. The magnitude of peak pinch force indicated an economic force output during manipulations following CTR. The peak pinch force, force ratio, and percentage of maximum pinch force also demonstrated a moderate correlation with the Semmes-Weinstein test. Analysis of these tests revealed that improved sensory function helped restore patients' performance in precise pinch force control evaluations. These results suggest that sensory information plays an important role in adjusting balanced force output in dexterous manipulation. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Measurements and modeling of transport and impurity radial profiles in the EXTRAP T2R reversed field pinch

NASA Astrophysics Data System (ADS)

Kuldkepp, M.; Brunsell, P. R.; Cecconello, M.; Dux, R.; Menmuir, S.; Rachlew, E.

2006-09-01

Radial impurity profiles of oxygen in the rebuilt reversed field pinch EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] have been measured with a multichannel spectrometer. Absolute ion densities for oxygen peak between 1-4×1010cm-3 for a central electron density of 1×1013cm-3. Transport simulations with the one-dimensional transport code STRAHL with a diffusion coefficient of 20m2 s-1 yield density profiles similar to those measured. Direct measurement of the ion profile evolution during pulsed poloidal current drive suggests that the diffusion coefficient is reduced by a factor ˜2 in the core but remains unaffected toward the edge. Core transport is not significantly affected by the radial magnetic field growth seen at the edge in discharges without feedback control. This indicates that the mode core amplitude remains the same while the mode eigenfunction increases at the edge.

Unusual Domain Structure and Filamentary Superfluidity for 2D Hard-Core Bosons in Insulating Charge-Ordered Phase

NASA Astrophysics Data System (ADS)

Panov, Yu. D.; Moskvin, A. S.; Rybakov, F. N.; Borisov, A. B.

2016-12-01

We made use of a special algorithm for compute unified device architecture for NVIDIA graphics cards, a nonlinear conjugate-gradient method to minimize energy functional, and Monte-Carlo technique to directly observe the forming of the ground state configuration for the 2D hard-core bosons by lowering the temperature and its evolution with deviation away from half-filling. The novel technique allowed us to examine earlier implications and uncover novel features of the phase transitions, in particular, look upon the nucleation of the odd domain structure, emergence of filamentary superfluidity nucleated at the antiphase domain walls of the charge-ordered phase, and nucleation and evolution of different topological structures.

Fourier heat conduction as a strong kinetic effect in one-dimensional hard-core gases

NASA Astrophysics Data System (ADS)

Zhao, Hanqing; Wang, Wen-ge

2018-01-01

For a one-dimensional (1D) momentum conserving system, intensive studies have shown that generally its heat current autocorrelation function (HCAF) tends to decay in a power-law manner and results in the breakdown of the Fourier heat conduction law in the thermodynamic limit. This has been recognized to be a dominant hydrodynamic effect. Here we show that, instead, the kinetic effect can be dominant in some cases and leads to the Fourier law for finite-size systems. Usually the HCAF undergoes a fast decaying kinetic stage followed by a long slowly decaying hydrodynamic tail. In a finite range of the system size, we find that whether the system follows the Fourier law depends on whether the kinetic stage dominates. Our Rapid Communication is illustrated by the 1D hard-core gas models with which the HCAF is derived analytically and verified numerically by molecular dynamics simulations.

Quasi-linear gyrokinetic predictions of the Coriolis momentum pinch in National Spherical Torus Experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guttenfelder, W.; Kaye, S. M.; Ren, Y.

This paper presents quasi-linear gyrokinetic predictions of the Coriolis momentum pinch for low aspect-ratio National Spherical Torus Experiment (NSTX) H-modes where previous experimental measurements were focused. Local, linear calculations predict that in the region of interest (just outside the mid-radius) of these relatively high-beta plasmas, profiles are most unstable to microtearing modes that are only effective in transporting electron energy. However, sub-dominant electromagnetic and electrostaticballooning modes are also unstable, which are effective at transporting energy, particles, and momentum. The quasi-linear prediction of transport from these weaker ballooning modes, assuming they contribute transport in addition to that from microtearing modes inmore » a nonlinear turbulent state, leads to a very small or outward convection of momentum, inconsistent with the experimentally measured inward pinch, and opposite to predictions in conventional aspect ratio tokamaks. Additional predictions of a low beta L-mode plasma, unstable to more traditional electrostatic ion temperature gradient-trapped electron mode instability, show that the Coriolis pinch is inward but remains relatively weak and insensitive to many parameter variations. The weak or outward pinch predicted in NSTX plasmas appears to be at least partially correlated to changes in the parallel mode structure that occur at a finite beta and low aspect ratio, as discussed in previous theories. The only conditions identified where a stronger inward pinch is predicted occur either in the purely electrostatic limit or if the aspect ratio is increased. Lastly, as the Coriolis pinch cannot explain the measured momentum pinch, additional theoretical momentum transport mechanisms are discussed that may be potentially important.« less

Quasi-linear gyrokinetic predictions of the Coriolis momentum pinch in National Spherical Torus Experiment

DOE PAGES

Guttenfelder, W.; Kaye, S. M.; Ren, Y.; ...

2016-05-11

This paper presents quasi-linear gyrokinetic predictions of the Coriolis momentum pinch for low aspect-ratio National Spherical Torus Experiment (NSTX) H-modes where previous experimental measurements were focused. Local, linear calculations predict that in the region of interest (just outside the mid-radius) of these relatively high-beta plasmas, profiles are most unstable to microtearing modes that are only effective in transporting electron energy. However, sub-dominant electromagnetic and electrostaticballooning modes are also unstable, which are effective at transporting energy, particles, and momentum. The quasi-linear prediction of transport from these weaker ballooning modes, assuming they contribute transport in addition to that from microtearing modes inmore » a nonlinear turbulent state, leads to a very small or outward convection of momentum, inconsistent with the experimentally measured inward pinch, and opposite to predictions in conventional aspect ratio tokamaks. Additional predictions of a low beta L-mode plasma, unstable to more traditional electrostatic ion temperature gradient-trapped electron mode instability, show that the Coriolis pinch is inward but remains relatively weak and insensitive to many parameter variations. The weak or outward pinch predicted in NSTX plasmas appears to be at least partially correlated to changes in the parallel mode structure that occur at a finite beta and low aspect ratio, as discussed in previous theories. The only conditions identified where a stronger inward pinch is predicted occur either in the purely electrostatic limit or if the aspect ratio is increased. Lastly, as the Coriolis pinch cannot explain the measured momentum pinch, additional theoretical momentum transport mechanisms are discussed that may be potentially important.« less

Design and experimental research on a self-magnetic pinch diode under MV

NASA Astrophysics Data System (ADS)

Pengfei, ZHANG; Yang, HU; Jiang, SUN; Yan, SONG; Jianfeng, SUN; Zhiming, YAO; Peitian, CONG; Mengtong, QIU; Aici, QIU

2018-01-01

A self-magnetic pinch diode (SMPD) integrating an anode foil-reinforced electron beam pinch focus and a small high-dose x-ray spot output was designed and optimized. An x-ray focal spot measuring system was developed in accordance with the principle of pinhole imaging. The designed SMPD and the corresponding measuring system were tested under ∼MV, with 1.75 × 2 mm2 oval x-ray spots (AWE defined) and forward directed dose 1.6 rad at 1 m. Results confirmed that the anode foil can significantly strengthen the electron beam pinch focus, and the focal spot measuring system can collect clear focal spot images. This finding indicated that the principle and method are feasible.

The influence of the self-consistent mode structure on the Coriolis pinch effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peeters, A. G.; Camenen, Y.; Casson, F. J.

This paper discusses the effect of the mode structure on the Coriolis pinch effect [A. G. Peeters, C. Angioni, and D. Strintzi, Phys. Rev. Lett. 98, 265003 (2007)]. It is shown that the Coriolis drift effect can be compensated for by a finite parallel wave vector, resulting in a reduced momentum pinch velocity. Gyrokinetic simulations in full toroidal geometry reveal that parallel dynamics effectively removes the Coriolis pinch for the case of adiabatic electrons, while the compensation due to the parallel dynamics is incomplete for the case of kinetic electrons, resulting in a finite pinch velocity. The finite flux inmore » the case of kinetic electrons is interpreted to be related to the electron trapping, which prevents a strong asymmetry in the electrostatic potential with respect to the low field side position. The physics picture developed here leads to the discovery and explanation of two unexpected effects: First the pinch velocity scales with the trapped particle fraction (root of the inverse aspect ratio), and second there is no strong collisionality dependence. The latter is related to the role of the trapped electrons, which retain some symmetry in the eigenmode, but play no role in the perturbed parallel velocity.« less

Diagnostics for Z-pinch implosion experiments on PTS

NASA Astrophysics Data System (ADS)

Ren, X. D.; Huang, X. B.; Zhou, S. T.; Zhang, S. Q.; Dan, J. K.; Li, J.; Cai, H. C.; Wang, K. L.; Ouyang, K.; Xu, Q.; Duan, S. C.; Chen, G. H.; Wang, M.; Feng, S. P.; Yang, L. B.; Xie, W. P.; Deng, J. J.

2014-12-01

The preliminary experiments of wire array implosion were performed on PTS, a 10 MA z-pinch driver with a 70 ns rise time. A set of diagnostics have been developed and fielded on PTS to study pinch physics and implosion dynamics of wire array. Radiated power measurement for soft x-rays was performed by multichannel filtered x-ray diode array, and flat spectral responses x-ray diode detector. Total x-ray yield was measured by a calibrated, unfiltered nickel bolometer which was also used to obtain pinch power. Multiple time-gated pinhole cameras were used to produce spatial-resolved images of x-ray self-emission from plasmas. Two time-integrated pinhole cameras were used respectively with 20-μm Be filter and with multilayer mirrors to record images produced by >1-keV and 277±5 eV self-emission. An optical streak camera was used to produce radial implosion trajectories, and an x-ray streak camera paired with a horizontal slit was used to record a continuous time-history of emission with one-dimensional spatial resolution. A frequency-doubled Nd:YAG laser (532 nm) was used to produce four frame laser shadowgraph images with 6 ns time interval. We will briefly describe each of these diagnostics and present some typical results from them.

Quantification of hand function by power grip and pinch strength force measurements in ulnar nerve lesion simulated by ulnar nerve block.

PubMed

Wachter, Nikolaus Johannes; Mentzel, Martin; Krischak, Gert D; Gülke, Joachim

2017-06-24

In the assessment of hand and upper limb function, grip strength is of the major importance. The measurement by dynamometers has been established. In this study, the effect of a simulated ulnar nerve lesion on different grip force measurements was evaluated. In 25 healthy volunteers, grip force measurement was done by the JAMAR dynamometer (Fabrication Enterprises Inc, Irvington, NY) for power grip and by a pinch strength dynamometer for tip pinch strength, tripod grip, and key pinch strength. A within-subject research design was used in this prospective study. Each subject served as the control by preinjection measurements of grip and pinch strength. Subsequent measurements after ulnar nerve block were used to examine within-subject change. In power grip, there was a significant reduction of maximum grip force of 26.9% with ulnar nerve block compared with grip force without block (P < .0001). Larger reductions in pinch strength were observed with block: 57.5% in tip pinch strength (P < .0001), 61.0% in tripod grip (P < .0001), and 58.3% in key pinch strength (P < .0001). The effect of the distal ulnar nerve block on grip and pinch force could be confirmed. However, the assessment of other dimensions of hand strength as tip pinch, tripod pinch and key pinch had more relevance in demonstrating hand strength changes resulting from an distal ulnar nerve lesion. The measurement of tip pinch, tripod grip and key pinch can improve the follow-up in hand rehabilitation. II. Copyright © 2017 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

To probe a core

NASA Astrophysics Data System (ADS)

2017-04-01

Hidden under many kilometres of silicate mantle material, the cores of Earth and other planets are hard to investigate. The Psyche spacecraft, designed to visit a metal body that may be a core stripped of its mantle, could bring a close-up view.

Non-Abelian fractional quantum Hall states for hard-core bosons in one dimension

NASA Astrophysics Data System (ADS)

Paredes, Belén

2012-05-01

I present a family of one-dimensional bosonic liquids analogous to non-Abelian fractional quantum Hall states. A new quantum number is introduced to characterize these liquids, the chiral momentum, which differs from the usual angular or linear momentum in one dimension. As their two-dimensional counterparts, these liquids minimize a k-body hard-core interaction with the minimum total chiral momentum. They exhibit global order, with a hidden organization of the particles in k identical copies of a one-dimensional Laughlin state. For k=2 the state is a p-wave paired phase corresponding to the Pfaffian quantum Hall state. By imposing conservation of the total chiral momentum, an exact parent Hamiltonian is derived which involves long-range tunneling and interaction processes with an amplitude decaying with the chord distance. This family of non-Abelian liquids is shown to be in formal correspondence with a family of spin-(k)/(2) liquids which are total singlets made out of k indistinguishable resonating valence bond states. The corresponding spin Hamiltonians are obtained.

Polar Radiation-Flux Symmetry Measurements in Z-Pinch-Driven Hohlraums with Symmetric Double-Pinch Drive

NASA Astrophysics Data System (ADS)

Hanson, D. L.; Vesey, R. A.; Cuneo Porter, M. E., Jr.; Chandler, G. A.; Ruggles, L. E.; Simpson, W. W.; Seamen, H.; Primm, P.; Torres, J.; McGurn, J.; Gilliland, T. L.; Reynolds, P.; Hebron, D. E.; Dropinski, S. C.; Schroen-Carey, D. G.; Hammer, J. H.; Landen, O.; Koch, J.

2000-10-01

We are currently exploring symmetry requirements of the z-pinch-driven hohlraum concept [1] for high-yield inertial confinement fusion. In experiments on the Z accelerator, the burnthrough of a low-density self-backlit foam ball has been used to diagnose the large time-dependent flux asymmetry of several single-sided-drive hohlraum geometries [2]. We are currently applying this technique to study polar radiation flux symmetry in a symmetric double z-pinch geometry. Wire arrays on opposite ends of the hohlraum, connected in series to a single current drive of 18 MA, implode and stagnate on axis, efficiently radiating about 100 TW of x rays which heat the secondary to 75 eV. Comparisons with 3-D radiosity and 2-D rad-hydro models of hohlraum symmetry performance will be presented. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000. 1 J. H. Hammer et al., Phys. Plasmas 6, 2129 (1999). 2 D. L. Hanson et al., Bull. Am. Phys. Soc. 44, 40 (1999).

Development and simulation study of a new inverse-pinch high Coulomb transfer switch

NASA Technical Reports Server (NTRS)

Choi, Sang H.

1989-01-01

The inverse-pinch plasma switch was studied using a computer simulation code. The code was based on a 2-D, 2-temperature magnetohydrodynamic (MHD) model. The application of this code was limited to the disk-type inverse-pinch plasma switch. The results of the computer analysis appear to be in agreement with the experimental results when the same parameters are used. An inverse-pinch plasma switch for closing has been designed and tested for high-power switching requirements. An azimuthally uniform initiation of breakdown is a key factor in achieving an inverse-pinch current path in the switch. Thus, various types of triggers, such as trigger pins, wire-brush, ring trigger, and hypocycloidal-pinch (HCP) devices have been tested for uniform breakdown. Recently, triggering was achieved by injection of a plasma-ring (plasma puff) that is produced separately with hypocycloidal-pinch electrodes placed under the cathode of the main gap. The current paths at switch closing, initiated by the injection of a plasma-ring from the HCP trigger are azimuthally uniform, and the local current density is significantly reduced, so that damage to the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes and the insulator surfaces is minimized. The test results indicate that electron bombardment on the electrodes is four orders of magnitude less than that of a spark-gap switch for the same switching power. Indeed, a few thousand shots with peak current exceeding a mega-ampere and with hold-off voltage up to 20 kV have been conducted without showing measurable damage to the electrodes and insulators.

Existence of a return direction for plasma escaping from a pinched column in a plasma focus discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kubes, P.; Cikhardt, J.; Klir, D.

2015-05-15

The use of multi-frame interferometry used on the PF-1000 device with the deuterium filling showed the existence of a return motion of the top of several lobules of the pinched column formed at the pinched plasma column. This phenomenon was observed in the presence of an over-optimal mass in front of the anode, which depressed the intensity of the implosion and the smooth surface of the pinched plasma column. The observed evolution was explored through the use of closed poloidal currents transmitted outside the pinched plasma. This interpretation complements the scenario of the closed currents flowing within the structures insidemore » the pinched column, which has been published recently on the basis of observations from interferometry, neutron, and magnetic probe diagnostics on this device.« less

Numerical simulation of fiber and wire array Z-pinches with Trac-II

NASA Astrophysics Data System (ADS)

Reisman, David Barton

Trac-II is a two dimensional axisymmetric resistive MHD code. It simulates all three spatial components (r, z, φ) of the magnetic field and fluid velocity vectors, and the plasma is treated as a single fluid with two temperatures (Te,Ti). In addition, it can optionally include a self-consistent external circuit. Recent modifications to the code include the addition of the 3-T radiation model, a 4-phase (solid- liquid-vapor-plasma) equation of state model (QEOS), a 4- phase electrical/thermal conductivity model, and an implicit solution of poloidal (Bz,Br) magnetic field diffusion. These changes permit a detailed study of fiber and wire array Z-pinches. Specifically, Trac-II is used to study the wire array Z-pinch at the PBFA-Z pulse power generator at Sandia National Laboratory. First, in 1-D we examine the behavior of a single wire in the Z-pinch. Then, using these results as initial radial conditions in 2-D, we investigate the dynamics of wire array configurations in the r-z and r-θ plane. In the r- z plane we examine the growth of the m = 0 or ``sausage'' instability in single wires within the array. In the r-θ plane we examine the merging behavior between neighboring wires. Special emphasis is placed on trying to explain how instability growth affects the performance of the Z-pinch. Lastly, we introduce Trac-III, a 3-D MHD code, and illustrate the m = 1 or ``kink'' instability. We also discuss how Trac-III can be modified to simulate the wire array Z-pinch.

Dynamics of conical wire array Z-pinch implosions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ampleford, D. J.; Lebedev, S. V.; Bland, S. N.

2007-10-15

A modification of the wire array Z pinch, the conical wire array, has applications to the understanding of wire array implosions and potentially to pulse shaping relevant to inertial confinement fusion. Results are presented from imploding conical wire array experiments performed on university scale 1 MA generators--the MAGPIE generator (1 MA, 240 ns) at Imperial College London [I. H. Mitchell et al., Rev. Sci Instrum. 67, 1533 (1996)] and the Nevada Terawatt Facility's Zebra generator (1 MA, 100 ns) at the University of Nevada, Reno [B. Bauer et al., in Dense Z-Pinches, edited by N. Pereira, J. Davis, and P.more » Pulsifer (AIP, New York, 1997), Vol. 409, p. 153]. This paper will discuss the implosion dynamics of conical wire arrays. Data indicate that mass ablation from the wires in this complex system can be reproduced with a rocket model with fixed ablation velocity. Modulations in the ablated plasma are present, the wavelength of which is invariant to a threefold variation in magnetic field strength. The axial variation in the array leads to a zippered precursor column formation. An initial implosion of a magnetic bubble near the cathode is followed by the implosion zippering upwards. Spectroscopic data demonstrating a variation of plasma parameters (e.g., electron temperature) along the Z-pinch axis is discussed, and experimental data are compared to magnetohydrodynamic simulations.« less

[Contrast of Z-Pinch X-Ray Yield Measure Technique].

PubMed

Li, Mo; Wang, Liang-ping; Sheng, Liang; Lu, Yi

2015-03-01

Resistive bolometer and scintillant detection system are two mainly Z-pinch X-ray yield measure techniques which are based on different diagnostic principles. Contrasting the results from two methods can help with increasing precision of X-ray yield measurement. Experiments with different load material and shape were carried out on the "QiangGuang-I" facility. For Al wire arrays, X-ray yields measured by the two techniques were largely consistent. However, for insulating coating W wire arrays, X-ray yields taken from bolometer changed with load parameters while data from scintillant detection system hardly changed. Simulation and analysis draw conclusions as follows: (1) Scintillant detection system is much more sensitive to X-ray photons with low energy and its spectral response is wider than the resistive bolometer. Thus, results from the former method are always larger than the latter. (2) The responses of the two systems are both flat to Al plasma radiation. Thus, their results are consistent for Al wire array loads. (3) Radiation form planar W wire arrays is mainly composed of sub-keV soft X-ray. X-ray yields measured by the bolometer is supposed to be accurate because of the nickel foil can absorb almost all the soft X-ray. (4) By contrast, using planar W wire arrays, data from scintillant detection system hardly change with load parameters. A possible explanation is that while the distance between wires increases, plasma temperature at stagnation reduces and spectra moves toward the soft X-ray region. Scintillator is much more sensitive to the soft X-ray below 200 eV. Thus, although the total X-ray yield reduces with large diameter load, signal from the scintillant detection system is almost the same. (5) Both Techniques affected by electron beams produced by the loads.

Efficient Neutron Production from a Novel Configuration of Deuterium Gas-Puff Z-Pinch

NASA Astrophysics Data System (ADS)

Klir, D.; Kubes, P.; Rezac, K.; Cikhardt, J.; Kravarik, J.; Sila, O.; Shishlov, A. V.; Kovalchuk, B. M.; Ratakhin, N. A.; Kokshenev, V. A.; Labetsky, A. Yu.; Cherdizov, R. K.; Fursov, F. I.; Kurmaev, N. E.; Dudkin, G. N.; Nechaev, B. A.; Padalko, V. N.; Orcikova, H.; Turek, K.

2014-03-01

A novel configuration of a deuterium z pinch has been used to generate fusion neutrons. Injecting an outer hollow cylindrical plasma shell around an inner deuterium gas puff, neutron yields from DD reactions reached Yn=(2.9±0.3)×1012 at 700 ns implosion time and 2.7 MA current. Such a neutron yield means a tenfold increase in comparison with previous deuterium gas puff experiments at the same current generator. The increase of beam-target yields was obtained by a larger amount of current assembled on the z-pinch axis, and subsequently by higher induced voltage and higher energies of deuterons. A stack of CR-39 track detectors on the z-pinch axis showed hydrogen ions up to 38 MeV. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial time-of-flight detectors, respectively. The number of DD neutrons per one joule of stored plasma energy approached 5×107. This implies that deuterium gas puff z pinches belong to the most efficient plasma-based sources of DD neutrons.

2D Kinetic Particle in Cell Simulations of a Shear-Flow Stabilized Z-Pinch

NASA Astrophysics Data System (ADS)

Tummel, Kurt; Higginson, Drew; Schmidt, Andrea; Link, Anthony; McLean, Harry; Shumlak, Uri; Nelson, Brian; Golingo, Raymond; Claveau, Elliot; Lawrence Livermore National Lab Team; University of Washington Team

2016-10-01

The Z-pinch is a relatively simple and attractive potential fusion reactor design, but attempts to develop such a reactor have consistently struggled to overcome Z-pinch instabilities. The ``sausage'' and ``kink'' modes are among the most robust and prevalent Z-pinch instabilities, but theory and simulations suggest that axial flow-shear, dvz / dr ≠ 0 , can suppress these modes. Experiments have confirmed that Z-pinch plasmas with embedded axial flow-shear display a significantly enhanced resilience to the sausage and kink modes at a demonstration current of 50kAmps. A new experiment is under way to test the concept at higher current, and efforts to model these plasmas are being expanded. The performance and stability of these devices will depend on features like the plasma viscosity, anomalous resistivity, and finite Larmor radius effects, which are most accurately characterized in kinetic models. To predict these features, kinetic simulations using the particle in cell code LSP are now in development, and initial benchmarking and 2D stability analyses of the sausage mode are presented here. These results represent the first kinetic modeling of the flow-shear stabilized Z-pinch. This work is funded by the USDOE/ARPAe Alpha Program. Prepared by LLNL under Contract DE-AC52-07NA27344.

The Pinch Pot Technique and Raku.

ERIC Educational Resources Information Center

Demery, Marie

Since the 16th century, the small Japanese raku tea bowl has reflected the merged cultural influences of art, religion, and other countries on the art of Japanese pottery. Artistically, the bowl is a combination of ceramics (pinching) and sculpture (carving). The dictates of the Zen Buddhist tea masters determine its sculptural process and steps,…

Observation of energetic electron confinement in a largely stochastic reversed-field pinch plasma

NASA Astrophysics Data System (ADS)

Clayton, D. J.; Chapman, B. E.; O'Connell, R.; Almagri, A. F.; Burke, D. R.; Forest, C. B.; Goetz, J. A.; Kaufman, M. C.; Bonomo, F.; Franz, P.; Gobbin, M.; Piovesan, P.

2010-01-01

Runaway electrons with energies >100 keV are observed with the appearance of an m =1 magnetic island in the core of otherwise stochastic Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field-pinch plasmas. The island is associated with the innermost resonant tearing mode, which is usually the largest in the m =1 spectrum. The island appears over a range of mode spectra, from those with a weakly dominant mode to those, referred to as quasi single helicity, with a strongly dominant mode. In a stochastic field, the rate of electron loss increases with electron parallel velocity. Hence, high-energy electrons imply a region of reduced stochasticity. The global energy confinement time is about the same as in plasmas without high-energy electrons or an island in the core. Hence, the region of reduced stochasticity must be localized. Within a numerical reconstruction of the magnetic field topology, high-energy electrons are substantially better confined inside the island, relative to the external region. Therefore, it is deduced that the island provides a region of reduced stochasticity and that the high-energy electrons are generated and well confined within this region.

A spin-liquid with pinch-line singularities on the pyrochlore lattice.

PubMed

Benton, Owen; Jaubert, L D C; Yan, Han; Shannon, Nic

2016-05-26

The mathematics of gauge theories lies behind many of the most profound advances in physics in the past 200 years, from Maxwell's theory of electromagnetism to Einstein's theory of general relativity. More recently it has become clear that gauge theories also emerge in condensed matter, a prime example being the spin-ice materials which host an emergent electromagnetic gauge field. In spin-ice, the underlying gauge structure is revealed by the presence of pinch-point singularities in neutron-scattering measurements. Here we report the discovery of a spin-liquid where the low-temperature physics is naturally described by the fluctuations of a tensor field with a continuous gauge freedom. This gauge structure underpins an unusual form of spin correlations, giving rise to pinch-line singularities: line-like analogues of the pinch points observed in spin-ice. Remarkably, these features may already have been observed in the pyrochlore material Tb2Ti2O7.

A spin-liquid with pinch-line singularities on the pyrochlore lattice

PubMed Central

Benton, Owen; Jaubert, L.D.C.; Yan, Han; Shannon, Nic

2016-01-01

The mathematics of gauge theories lies behind many of the most profound advances in physics in the past 200 years, from Maxwell's theory of electromagnetism to Einstein's theory of general relativity. More recently it has become clear that gauge theories also emerge in condensed matter, a prime example being the spin-ice materials which host an emergent electromagnetic gauge field. In spin-ice, the underlying gauge structure is revealed by the presence of pinch-point singularities in neutron-scattering measurements. Here we report the discovery of a spin-liquid where the low-temperature physics is naturally described by the fluctuations of a tensor field with a continuous gauge freedom. This gauge structure underpins an unusual form of spin correlations, giving rise to pinch-line singularities: line-like analogues of the pinch points observed in spin-ice. Remarkably, these features may already have been observed in the pyrochlore material Tb2Ti2O7. PMID:27225400

Relationship between grip, pinch strengths and anthropometric variables, types of pitch throwing among Japanese high school baseball pitchers.

PubMed

Tajika, Tsuyoshi; Kobayashi, Tsutomu; Yamamoto, Atsushi; Shitara, Hitoshi; Ichinose, Tsuyoshi; Shimoyama, Daisuke; Okura, Chisa; Kanazawa, Saeko; Nagai, Ayako; Takagishi, Kenji

2015-03-01

Grip and pinch strength are crucially important attributes and standard parameters related to the functional integrity of the hand. It seems significant to investigate normative data for grip and pinch strength of baseball players to evaluate their performance and condition. Nevertheless, few reports have explained the association between grip and pinch strength and anthropometric variables and types of pitch throwing for baseball pitchers. The aim of this study was to measure and evaluate clinical normative data for grip and tip, key, palmar pinch strength and to assess the relationship between these data and anthropometric variables and types of pitch throwing among Japanese high-school baseball pitchers. One hundred-thirty three healthy high school baseball pitchers were examined and had completed a self-administered questionnaire including items related to age, hand dominance, throwing ratio of type of pitch. A digital dynamometer was used to measure grip strength and a pinch gauge to measure tip, key and palmer pinch in both dominant and nondominant side. Body composition was measured by the multi frequency segmental body composition analyzer. Grip strength and tip and palmer pinch strength in dominant side were statistically greater than them in nondominant side (P < 0.05). There were significant associations between grip strength and height (r = 0.33, P < 0.001), body mass (r = 0.50, P < 0.001), BMI (r = 0.37, P < 0.001), muscle mass of upper extremity (r = 0.56, P < 0.001), fat free mass (r = 0.57, P < 0.001), fat mass (r = 0.22, P < 0.05) in dominant side. A stepwise multiple regression analysis revealed that fat free mass and tip, palmer, key pinch strength were predictors of grip strength in dominant side. No statistical significant correlations were found between the throwing ratio of types of pitches thrown and grip strength and tip, key, palmar pinch strength. Our result provides normative values and evidences for grip and pinch strengths in high

Observation of trapped-electron-mode microturbulence in reversed field pinch plasmas

NASA Astrophysics Data System (ADS)

Duff, J. R.; Williams, Z. R.; Brower, D. L.; Chapman, B. E.; Ding, W. X.; Pueschel, M. J.; Sarff, J. S.; Terry, P. W.

2018-01-01

Density fluctuations in the large-density-gradient region of improved confinement Madison Symmetric Torus reversed field pinch (RFP) plasmas exhibit multiple features that are characteristic of the trapped-electron mode (TEM). Core transport in conventional RFP plasmas is governed by magnetic stochasticity stemming from multiple long-wavelength tearing modes. Using inductive current profile control, these tearing modes are reduced, and global confinement is increased to that expected for comparable tokamak plasmas. Under these conditions, new short-wavelength fluctuations distinct from global tearing modes appear in the spectrum at a frequency of f ˜ 50 kHz, which have normalized perpendicular wavenumbers k⊥ρs≲ 0.2 and propagate in the electron diamagnetic drift direction. They exhibit a critical-gradient threshold, and the fluctuation amplitude increases with the local electron density gradient. These characteristics are consistent with predictions from gyrokinetic analysis using the Gene code, including increased TEM turbulence and transport from the interaction of remnant tearing magnetic fluctuations and zonal flow.

Toroidal momentum pinch velocity due to the coriolis drift effect on small scale instabilities in a toroidal plasma.

PubMed

Peeters, A G; Angioni, C; Strintzi, D

2007-06-29

In this Letter, the influence of the "Coriolis drift" on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torque on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiments.

The integrin effector PINCH regulates JNK activity and epithelial migration in concert with Ras suppressor 1

PubMed Central

Kadrmas, Julie L.; Smith, Mark A.; Clark, Kathleen A.; Pronovost, Stephen M.; Muster, Nemone; Yates, John R.; Beckerle, Mary C.

2004-01-01

Cell adhesion and migration are dynamic processes requiring the coordinated action of multiple signaling pathways, but the mechanisms underlying signal integration have remained elusive. Drosophila embryonic dorsal closure (DC) requires both integrin function and c-Jun amino-terminal kinase (JNK) signaling for opposed epithelial sheets to migrate, meet, and suture. Here, we show that PINCH, a protein required for integrin-dependent cell adhesion and actin–membrane anchorage, is present at the leading edge of these migrating epithelia and is required for DC. By analysis of native protein complexes, we identify RSU-1, a regulator of Ras signaling in mammalian cells, as a novel PINCH binding partner that contributes to PINCH stability. Mutation of the gene encoding RSU-1 results in wing blistering in Drosophila, demonstrating its role in integrin-dependent cell adhesion. Genetic interaction analyses reveal that both PINCH and RSU-1 antagonize JNK signaling during DC. Our results suggest that PINCH and RSU-1 contribute to the integration of JNK and integrin functions during Drosophila development. PMID:15596544

Decoherence in models for hard-core bosons coupled to optical phonons

NASA Astrophysics Data System (ADS)

Dey, A.; Lone, M. Q.; Yarlagadda, S.

2015-09-01

Understanding coherent dynamics of excitons, spins, or hard-core bosons (HCBs) has tremendous scientific and technological implications for quantum computation. Here, we study decay of excited-state population and decoherence in two models for HCBs, namely, a two-site HCB model with site-dependent strong potentials and subject to non-Markovian dynamics and an infinite-range HCB model governed by Markovian dynamics. Both models are investigated in the regimes of antiadiabaticity and strong HCB-phonon coupling with each site providing a different local optical phonon environment; furthermore, the HCB systems in both models are taken to be initially uncorrelated with the environment in the polaronic frame of reference. In the case of the two-site HCB model, we show clearly that the degree of decoherence and decay of excited state are enhanced by the proximity of the site-energy difference to the eigenenergy of phonons and are most pronounced when the site-energy difference is at resonance with twice the polaronic energy; additionally, the decoherence and the decay effects are reduced when the strength of HCB-phonon coupling is increased. For the infinite-range model, when the site energies are the same, we derive an effective many-body Hamiltonian that commutes with the long-range system Hamiltonian and thus has the same set of eigenstates; consequently, a quantum-master-equation approach shows that the quantum states of the system do not decohere.

Impedance Dynamics in the Self-Magnetic Pinch (SMP) Diode on the RITS-6 Accelerator

NASA Astrophysics Data System (ADS)

Renk, Timothy; Johnston, Mark; Leckbee, Joshua; Webb, Timothy; Mazarakis, Michael; Kiefer, Mark; Bennett, Nichelle

2014-10-01

The RITS-6 inductive voltage adder (IVA) accelerator (3.5-8.5 MeV) at Sandia National Laboratories produces high-power (TW) focused electron beams (<3 mm diameter) for flash x-ray radiography applications. The Self-Magnetic Pinch (SMP) diode utilizes a hollowed metal cathode to produce a pinched focus onto a high Z metal converter. The electron flow from the IVA driver into the load region complicates understanding of diode evolution. There is growing evidence that reducing cathode size below some ``optimum'' value in order to achieve desired spot size reduction results in pinch instabilities leading to either reduced dose-rate, early radiation power termination, or both. We are studying evolving pinch dynamics with current and x-ray monitors, optical diagnostics, and spectroscopy, as well as with LSP [1] code simulations. We are also planning changes to anode-cathode materials as well as changes to the diode aspect ratio in an attempt to mitigate the above trends and improve pinch stability while achieving simultaneous spot size reduction. Experiments are ongoing, and latest results will be reported [1]. LSP is a software product of ATK Mission Research, Albuquerque, NM. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Adminis-tration under Contract DE-AC04-94AL85000.

Effect of the axial magnetic field on a metallic gas-puff pinch implosion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rousskikh, A. G.; Zhigalin, A. S.; Frolova, V.

2016-06-15

The effect of an axial magnetic field B{sub z} on an imploding metallic gas-puff Z-pinch was studied using 2D time-gated visible self-emission imaging. Experiments were performed on the IMRI-5 generator (450 kA, 450 ns). The ambient field B{sub z} was varied from 0.15 to 1.35 T. It was found that the initial density profile of a metallic gas-puff Z-pinch can be approximated by a power law. Time-gated images showed that the magneto-Rayleigh–Taylor instabilities were suppressed during the run-in phase both without axial magnetic field and with axial magnetic field. Helical instability structures were detected during the stagnation phase for B{sub z} < 1.1 T. For B{submore » z} = 1.35 T, the pinch plasma boundary was observed to be stable in both run-in and stagnation phases. When a magnetic field of 0.3 T was applied to the pinch, the soft x-ray energy was about twice that generated without axial magnetic field, mostly due to longer dwell time at stagnation.« less

Toroidal Momentum Pinch Velocity due to the Coriolis Drift Effect on Small Scale Instabilities in a Toroidal Plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peeters, A. G.; Angioni, C.; Strintzi, D.

In this Letter, the influence of the ''Coriolis drift'' on small scale instabilities in toroidal plasmas is shown to generate a toroidal momentum pinch velocity. Such a pinch results because the Coriolis drift generates a coupling between the density and temperature perturbations on the one hand and the perturbed parallel flow velocity on the other. A simple fluid model is used to highlight the physics mechanism and gyro-kinetic calculations are performed to accurately assess the magnitude of the pinch. The derived pinch velocity leads to a radial gradient of the toroidal velocity profile even in the absence of a torquemore » on the plasma and is predicted to generate a peaking of the toroidal velocity profile similar to the peaking of the density profile. Finally, the pinch also affects the interpretation of current experiment000.« less

Z-Pinch Plasma Neutron Sources

DTIC Science & Technology

2006-03-24

deuterium into 9 to 14 keV (around 10 keV), which is well in the fusion energy range we are interested in. To make plasma radiation sources work, we...showing the 1-D dynamics of the pinch plasma implosion, temperature, fusion energy production and deposition for the conditions of shot Z1422. The minimum...histories of ion and electron temperatures, fusion energy production and energy deposition in ID RMHD run modeling deuterium shot Z1422. In our simulations

The inverse skin effect in the Z-pinch and plasma focus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usenko, P. L., E-mail: otd4@expd.vniief.ru; Gaganov, V. V.

The inverse skin effect and its influence on the dynamics of high-current Z-pinch and plasma focus discharges in deuterium are analyzed. It is shown that the second compression responsible for the major fraction of the neutron yield can be interpreted as a result of the inverse skin effect resulting in the axial concentration of the longitudinal current density and the appearance of a reversed current in the outer layers of plasma pinches. Possible conditions leading to the enhancement of the inverse skin effect and accessible for experimental verification by modern diagnostics are formulated.

Pinch-off syndrome: transection of implantable central venous access device.

PubMed

Sugimoto, Takuya; Nagata, Hiroshi; Hayashi, Ken; Kano, Nobuyasu

2012-11-30

As the population of people with cancer increases so does the number of patients who take chemotherapy. Majority of them are administered parentally continuously. Implantable central venous catheter device is a good choice for those patients; however, severe complication would occur concerning the devices. Pinch-off syndrome is one of the most severe complications. The authors report a severe case of pinch-off syndrome. The patient with the implantable central venous device could not take chemotherapy because the device occluded. Further examination revealed the transection of the catheter. The transected fragment of the catheter in the heart was successfully removed by using a loop snare placed through the right femoral vein.

Controlled injection using a channel pinch in a plasma-channel-guided laser wakefield accelerator

NASA Astrophysics Data System (ADS)

Liu, Jiaqi; Zhang, Zhijun; Liu, Jiansheng; Li, Wentao; Wang, Wentao; Yu, Changhai; Qi, Rong; Qin, Zhiyong; Fang, Ming; Wu, Ying; Feng, Ke; Ke, Lintong; Wang, Cheng; Li, Ruxin

2018-06-01

Plasma-channel-guided laser plasma accelerators make it possible to drive high-brilliance compact radiation sources and have high-energy physics applications. Achieving tunable internal injection of the electron beam (e beam) inside the plasma channel, which realizes a tunable radiation source, is a challenging method to extend such applications. In this paper, we propose the use of a channel pinch, which is designed as an initial reduction followed by an expansion of the channel radius along the plasma channel, to achieve internal controlled off-axis e beam injection in a channel-guided laser plasma accelerator. The off-axis injection is triggered by bubble deformation in the expansion region. The dynamics of the plasma wake is explored, and the trapping threshold is found to be reduced radially in the channel pinch. Simulation results show that the channel pinch not only triggers injection process localized at the pinch but also modulates the parameters of the e beam by adjusting its density profile, which can additionally accommodate a tunable radiation source via betatron oscillation.

Characteristics of plasma-puff trigger for a inverse-pinch plasma switch

NASA Technical Reports Server (NTRS)

Choi, Eun H.; Venable, Demetrius D.; Han, Kwang S.; Lee, Ja H.

1993-01-01

The plasma-puff triggering mechanism based on a hypocycloidal pinch geometry was investigated to determine the optimal operating conditions for the azimuthally uniform surface flashover which initiates plasma-puff under wide ranges of fill gas pressure of Ar, He and N2. The optimal fill-gas pressure range for the azimuthally uniform plasma-puff was about 120 mTorr less than or equal to P(sub op) less than or equal to 450 Torr for He and N2. For Argon 120 mTorr is less than or equal to P(sub op) is less than or equal to 5 Torr. The inverse-pinch switch was triggered with the plasma-puff and the switching capability under various electrical parameters and working gas pressures of Ar, He and N2 was determined. The azimuthally uniform switching discharges were dependent on the type of fill gas and its fill pressure. A new concept of plasma-focus driven plasma-puff will be discussed in comparison with the current hypocycloidal-pinch plasma-puff triggering.

Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

DOE PAGES

Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; ...

2014-12-10

A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface ofmore » the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.« less

A Pressure-Based Analysis of Vortex Ring Pinch-Off

NASA Astrophysics Data System (ADS)

Schlueter, Kristy; Braun, Noah; Dabiri, John

2014-11-01

This study investigated the development of vortex rings over a range of maximum stroke ratios, and analyzed vorticity and pressure data for clues to the physical mechanisms underlying vortex pinch-off. An impulsive piston velocity profile and Reynolds number of 3000 were used for all cases. The formation number was consistently found to be 3.6 +/-0.3. A recently developed algorithm was used to generate pressure fields by integrating the pressure gradient along several paths through the velocity field and taking the median to get explicit values for pressure. The formation time at the occurrence of a local maximum in the pressure between the vortex ring and the lip of the nozzle, known as the trailing pressure maximum, was found to occur concurrently with the formation number for each case, within the error associated with the temporal resolution of the data. This suggests that the trailing pressure maximum is an indicator of vortex ring pinch-off. This is consistent with the results of Lawson and Dawson (2014), who found that the appearance of the trailing pressure maximum was coincident with the formation number. This pressure based approach to determining vortex ring pinch-off will be applied to a biological flow to examine the efficiency of such a flow. This research was partially supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles.

PubMed

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-11-02

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

PubMed Central

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-01-01

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

Fault-Tolerant, Radiation-Hard DSP

NASA Technical Reports Server (NTRS)

Czajkowski, David

2011-01-01

Commercial digital signal processors (DSPs) for use in high-speed satellite computers are challenged by the damaging effects of space radiation, mainly single event upsets (SEUs) and single event functional interrupts (SEFIs). Innovations have been developed for mitigating the effects of SEUs and SEFIs, enabling the use of very-highspeed commercial DSPs with improved SEU tolerances. Time-triple modular redundancy (TTMR) is a method of applying traditional triple modular redundancy on a single processor, exploiting the VLIW (very long instruction word) class of parallel processors. TTMR improves SEU rates substantially. SEFIs are solved by a SEFI-hardened core circuit, external to the microprocessor. It monitors the health of the processor, and if a SEFI occurs, forces the processor to return to performance through a series of escalating events. TTMR and hardened-core solutions were developed for both DSPs and reconfigurable field-programmable gate arrays (FPGAs). This includes advancement of TTMR algorithms for DSPs and reconfigurable FPGAs, plus a rad-hard, hardened-core integrated circuit that services both the DSP and FPGA. Additionally, a combined DSP and FPGA board architecture was fully developed into a rad-hard engineering product. This technology enables use of commercial off-the-shelf (COTS) DSPs in computers for satellite and other space applications, allowing rapid deployment at a much lower cost. Traditional rad-hard space computers are very expensive and typically have long lead times. These computers are either based on traditional rad-hard processors, which have extremely low computational performance, or triple modular redundant (TMR) FPGA arrays, which suffer from power and complexity issues. Even more frustrating is that the TMR arrays of FPGAs require a fixed, external rad-hard voting element, thereby causing them to lose much of their reconfiguration capability and in some cases significant speed reduction. The benefits of COTS high

Failure analysis of pinch-torsion tests as a thermal runaway risk evaluation method of Li-ion cells

NASA Astrophysics Data System (ADS)

Xia, Yuzhi; Li, Tianlei; Ren, Fei; Gao, Yanfei; Wang, Hsin

2014-11-01

Recently a pinch-torsion test is developed for safety testing of Li-ion batteries. It has been demonstrated that this test can generate small internal short-circuit spots in the separator in a controllable and repeatable manner. In the current research, the failure mechanism is examined by numerical simulations and comparisons to experimental observations. Finite element models are developed to evaluate the deformation of the separators under both pure pinch and pinch-torsion loading conditions. It is discovered that the addition of the torsion component significantly increased the maximum first principal strain, which is believed to induce the internal short circuit. In addition, the applied load in the pinch-torsion test is significantly less than in the pure pinch test, thus dramatically improving the applicability of this method to ultra-thick batteries which otherwise require heavy load in excess of machine capability. It is further found that the separator failure is achieved in the early stage of torsion (within a few degree of rotation). Effect of coefficient of friction on the maximum first principal strain is also examined.

Resistive wall modes in the EXTRAP T2R reversed-field pinch

NASA Astrophysics Data System (ADS)

Brunsell, P. R.; Malmberg, J.-A.; Yadikin, D.; Cecconello, M.

2003-10-01

Resistive wall modes (RWM) in the reversed field pinch are studied and a detailed comparison of experimental growth rates and linear magnetohydrodynamic (MHD) theory is made. RWM growth rates are experimentally measured in the thin shell device EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43, 1 (2001)]. Linear MHD calculations of RWM growth rates are based on experimental equilibria. Experimental and linear MHD RWM growth rate dependency on the equilibrium profiles is investigated experimentally by varying the pinch parameter Θ=Bθ(a)/ in the range Θ=1.5-1.8. Quantitative agreement between experimental and linear MHD growth rates is seen. The dominating RWMs are the internal on-axis modes (having the same helicity as the central equilibrium field). At high Θ, external nonresonant modes are also observed. For internal modes experimental growth rates decrease with Θ while for external modes, growth rates increase with Θ. The effect of RWMs on the reversed-field pinch plasma performance is discussed.

Theta-Pinch Thruster for Piloted Deep Space Exploration

NASA Technical Reports Server (NTRS)

LaPointe, Mike R.; Reddy, Dhanireddy (Technical Monitor)

2000-01-01

A new high-power propulsion concept that combines a rapidly pulsed theta-pinch discharge with upstream particle reflection by a magnetic mirror was evaluated under a Phase 1 grant awarded through the NASA Institute for Advanced Concepts. Analytic and numerical models were developed to predict the performance of a theta-pinch thruster operated over a wide range of initial gas pressures and discharge periods. The models indicate that a 1 m radius, 10 m long thruster operated with hydrogen propellant could provide impulse-bits ranging from 1 N-s to 330 N-s with specific impulse values of 7,500 s to 2,500 s, respectively. A pulsed magnetic field strength of 2 T is required to compress and heat the preionized hydrogen over a 10(exp -3) second discharge period, with about 60% of the heated plasma exiting the chamber each period to produce thrust. The unoptimized thruster efficiency is low, peaking at approximately 16% for an initial hydrogen chamber pressure of 100 Torr. The specific impulse and impulse-bit at this operating condition are 3,500 s and 90 N-s, respectively, and the required discharge energy is approximately 9x10(exp 6) J. For a pulse repetition rate of 10 Hz, the engine would produce an average thrust of 900 N at 3,500 s specific impulse. Combined with the electrodeless nature of the device, these performance parameters indicate that theta-pinch thrusters could provide unique, long-life propulsion systems for piloted deep space mission applications.

Analysis of pinching in deterministic particle separation

NASA Astrophysics Data System (ADS)

Risbud, Sumedh; Luo, Mingxiang; Frechette, Joelle; Drazer, German

2011-11-01

We investigate the problem of spherical particles vertically settling parallel to Y-axis (under gravity), through a pinching gap created by an obstacle (spherical or cylindrical, center at the origin) and a wall (normal to X axis), to uncover the physics governing microfluidic separation techniques such as deterministic lateral displacement and pinched flow fractionation: (1) theoretically, by linearly superimposing the resistances offered by the wall and the obstacle separately, (2) computationally, using the lattice Boltzmann method for particulate systems and (3) experimentally, by conducting macroscopic experiments. Both, theory and simulations, show that for a given initial separation between the particle centre and the Y-axis, presence of a wall pushes the particles closer to the obstacle, than its absence. Experimentally, this is expected to result in an early onset of the short-range repulsive forces caused by solid-solid contact. We indeed observe such an early onset, which we quantify by measuring the asymmetry in the trajectories of the spherical particles around the obstacle. This work is partially supported by the National Science Foundation Grant Nos. CBET- 0731032, CMMI-0748094, and CBET-0954840.

A Multiple Z-Pinch Configuration for the Generation of High-Density, Magnetized Plasmas

NASA Astrophysics Data System (ADS)

Tarditi, Alfonso G.

2015-11-01

The z-pinch is arguably the most straightforward and economical approach for the generation and confinement of hot plasmas, with a long history of theoretical investigations and experimental developments. While most of the past studies were focused on countering the natural tendency of z-pinches to develop instabilities, this study attempts to take advantage of those unstable regimes to form a quasi-stable plasma, with higher density and temperature, possibly of interest for a fusion reactor concept. For this purpose, a configuration with four z-pinch discharges, with axis parallel to each other and symmetrically positioned, is considered. Electrodes for the generation of the discharges and magnetic coils are arranged to favor the formation of concave discharge patterns. The mutual attraction from the co-streaming discharge currents enhances this pattern, leading to bent plasma streams, all nearing towards the axis. This configuration is intended to excite and sustain a ``kink'' unstable mode for each z-pinch, eventually producing either plasmoid structures, detached from each discharge, or sustained kink patterns: both these cases appear to lead to plasmas merging in the central region. The feasibility of this approach in creating a higher density, hotter, meta-stable plasma regime is investigated computationally, addressing both the kink excitation phase and the dynamics of the converging plasma columns.

Preconditioned wire array Z-pinches driven by a double pulse current generator

NASA Astrophysics Data System (ADS)

Wu, Jian; Lu, Yihan; Sun, Fengju; Li, Xingwen; Jiang, Xiaofeng; Wang, Zhiguo; Zhang, Daoyuan; Qiu, Aici; Lebedev, Sergey

2018-07-01

Suppression of the core-corona structure and wire ablation in wire array Z-pinches is investigated using a novel double pulse current generator ‘Qin-1’ facility. The ‘Qin-1’ facility allows coupling a ∼10 kA 20 ns prepulse generator with a ∼0.8 MA 160 ns main current generator. The tailored prepulse current preheats wires to a gaseous state and the time interval between the prepulse and the main current pulse allows formation of a more uniform mass distribution for the implosion. The implosion of a gasified two aluminum-wire array showed no ablation phase and allowed all array mass to participate in the implosion. The initial perturbations formed from the inhomogeneous ablation were suppressed, however, the magneto Rayleigh–Taylor (MRT) instability during the implosion was still significant and further researches on the generation and development of the MRT instabilities of this gasified wire array are needed.

Pinching Solutions of Slender Cylindrical Jets

DTIC Science & Technology

1993-06-01

NASA Langley Research Center, Hampton, VA 23681.2This research was supported in part by Fondo Nacional de Desarrollo Cientifico y Tecnologico (FONDE...concentrate on inviscid irrotational flows of liquid jets. A review article has been written by Bogy [2]. Of relevance is also the work of Chandrasekhar...equations become elliptic and allow the possibility of admissible pinching solutions described in this article . It is interesting to find that for jets

The microscopic Z-pinch process of current-carrying rarefied deuterium plasma shell

NASA Astrophysics Data System (ADS)

Ning, Cheng; Feng, Zhixing; Xue, Chuang; Li, Baiwen

2015-02-01

For insight into the microscopic mechanism of Z-pinch dynamic processes, a code of two-dimensional particle-in-cell (PIC) simulation has been developed in cylindrical coordinates. In principle, the Z-pinch of current-carrying rarefied deuterium plasma shell has been simulated by means of this code. Many results related to the microscopic processes of the Z-pinch are obtained. They include the spatio-temporal distributions of electromagnetic field, current density, forces experienced by the ions and electrons, positions and energy distributions of particles, and trailing mass and current. In radial direction, the electric and magnetic forces exerted on the electrons are comparable in magnitude, while the forces exerted on the ions are mainly the electric forces. So in the Z-pinch process, the electrons are first accelerated in Z direction and get higher velocities; then, they are driven inwards to the axis at the same time by the radial magnetic forces (i.e., Lorentz forces) of them. That causes the separations between the electrons and ions because the ion mass is much larger than the electron's, and in turn a strong electrostatic field is produced. The produced electrostatic field attracts the ions to move towards the electrons. When the electrons are driven along the radial direction to arrive at the axis, they shortly move inversely due to the static repellency among them and their tiny mass, while the ions continue to move inertially inwards, and later get into stagnation, and finally scatter outwards. Near the stagnation, the energies of the deuterium ions mostly range from 0.3 to 6 keV, while the electron energies are mostly from 5 to 35 keV. The radial components, which can contribute to the pinched plasma temperature, of the most probable energies of electron and ion at the stagnation are comparable to the Bennett equilibrium temperature (about 1 keV), and also to the highest temperatures of electron and ion obtained in one dimensional radiation

Moderately reverberant learning ultrasonic pinch panel.

PubMed

Nikolovski, Jean-Pierre

2013-10-01

Tactile sensing is widely used in human-computer interfaces. However, mechanical integration of touch technologies is often perceived as difficult by engineers because it often limits the freedom of style or form factor requested by designers. Recent work in active ultrasonic touch technologies has made it possible to transform thin glass plates, metallic sheets, or plastic shells into interactive surfaces. The method is based on a learning process of touch-induced, amplitude-disturbed diffraction patterns. This paper proposes, first, an evolution in the design with multiple dipole transducers that improves touch sensitivity or maximum panel size by a factor of ten, and improves robustness and usability in moderately reverberant panels, and second, defines a set of acoustic variables in the signal processing for the evaluation of sensitivity and radiating features. For proof of concept purposes, the design and process are applied to 3.2- and 6-mm-thick glass plates with variable damping conditions. Transducers are bonded to only one short side of the rectangular substrates. Measurements show that the highly sensitive free lateral sides are perfectly adapted for pinch-touch and pinch-slide interactions. The advantage of relative versus absolute touch disturbance measurement is discussed, together with tolerance to abutting contaminants.

LC and ferromagnetic resonance in soft/hard magnetic microwires

NASA Astrophysics Data System (ADS)

Tian, Bin; Vazquez, Manuel

2015-12-01

The magnetic behavior of soft/hard biphase microwires is introduced here. The microwires consist of a Co59.1Fe14.8Si10.2B15.9 soft magnetic nucleus and a Co90Ni10 hard outer shell separated by an intermediate insulating Pyrex glass microtube. By comparing the resistance spectrums of welding the ends of metallic core (CC) or welding the metallic core and outer shell (CS) to the connector, it is found that one of the two peaks in the resistance spectrum is because the LC resonance depends on the inductor and capacitors in which one is the capacitor between the metallic core and outer shell, and the other is between the outer shell and connector. Correspondingly, another peak is for the ferromagnetic resonance of metallic core. After changing the capacitance of the capacitors, the frequency of LC resonance moves to high frequency band, and furthermore, the peak of LC resonance in the resistance spectrum disappeared. These magnetostatically coupled biphase systems are thought to be of large potential interest as sensing elements in sensor devices.

Particle pinch with fully noninductive lower hybrid current drive in Tore Supra.

PubMed

Hoang, G T; Bourdelle, C; Pégourié, B; Schunke, B; Artaud, J F; Bucalossi, J; Clairet, F; Fenzi-Bonizec, C; Garbet, X; Gil, C; Guirlet, R; Imbeaux, F; Lasalle, J; Loarer, T; Lowry, C; Travère, J M; Tsitrone, E

2003-04-18

Recently, plasmas exceeding 4 min have been obtained with lower hybrid current drive (LHCD) in Tore Supra. These LHCD plasmas extend for over 80 times the resistive current diffusion time with zero loop voltage. Under such unique conditions the neoclassical particle pinch driven by the toroidal electric field vanishes. Nevertheless, the density profile remains peaked for more than 4 min. For the first time, the existence of an inward particle pinch in steady-state plasma without toroidal electric field, much larger than the value predicted by the collisional neoclassical theory, is experimentally demonstrated.

Failure analysis of pinch-torsion tests as a thermal runaway risk evaluation method of Li-Ion Cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xia, Yuzhi; Li, Dr. Tianlei; Ren, Prof. Fei

2014-01-01

Recently a pinch-torsion test is developed for safety testing of Li-ion batteries (Ren et al., J. Power Source, 2013). It has been demonstrated that this test can generate small internal short-circuit spots in the separator in a controllable and repeatable manner. In the current research, the failure mechanism is examined by numerical simulations and comparisons to experimental observations. Finite element models are developed to evaluate the deformation of the separators under both pure pinch and pinch-torsion loading conditions. It is discovered that the addition of the torsion component significantly increased the maximum principal strain, which is believed to induce themore » internal short circuit. In addition, the applied load in the pinch-torsion test is significantly less than in the pure pinch test, thus dramatically improving the applicability of this method to ultra-thick batteries which otherwise require heavy load in excess of machine capability. It is further found that the separator failure is achieved in the early stage of torsion (within a few degree of rotation). Effect of coefficient of friction on the maximum principal strain is also examined.« less

Analysis of staged Z-pinch implosion trajectories from experiments on Zebra

NASA Astrophysics Data System (ADS)

Ross, Mike P.; Conti, F.; Darling, T. W.; Ruskov, E.; Valenzuela, J.; Wessel, F. J.; Beg, F.; Narkis, J.; Rahman, H. U.

2017-10-01

The Staged Z-pinch plasma confinement concept relies on compressing an annular liner of high-Z plasma onto a target plasma column of deuterium fuel. The interface between the liner and target is stable against the Magneto-Rayleigh-Taylor Instability, which leads to effective fuel compression and makes the concept interesting as a potential fusion reactor. The liner initiates as a neutral gas puff, while the target plasma is a partially ionized (Zeff < 10 percent column ejected from a coaxial plasma gun. The Zebra pulsed power generator (1 MA peak current, 100 ns rise time) provides the discharge that ionizes the liner and drives the Z-pinch implosion. Diverse diagnostics observe the 100-300 km/s implosions including silicon diodes, photo-conducting detectors (PCDs), laser shadowgraphy, an XUV framing camera, and a visible streak camera. The imaging diagnostics track instabilities smaller than 0.1 mm, and Z-pinch diameters below 2.5 mm are seen at peak compression. This poster correlates the data from these diagnostics to elucidate implosion behavior dependencies on liner gas, liner pressure, target pressure, and applied, axial-magnetic field. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

Optimization of Capsule Symmetry in Z-Pinch Driven Hohlraums

NASA Astrophysics Data System (ADS)

Vesey, R. A.; Cuneo, M.; Hanson, D.; Porter, J.; Mehlhorn, T.; Ruggles, L.; Simpson, W.; Vargas, M.; Hammer, J.; Landen, O.

1999-11-01

The uniformity of the radiation flux incident on the capsule is a critical issue for indirect drive fusion using the z-pinch driven hohlraum high-yield concept(J.H. Hammer et al., Phys. Plas. 6), 2129 (1999).. Experiments on the Z accelerator at Sandia have demonstrated the ability to diagnose the uniformity of the flux striking a foam ball (surrogate capsule)(P.A. Amendt et al., Phys. Plas. 4), 1862 (1997); S.G. Glendinning et al. Rev. Sci. Instrum. 70, 536 (1999).. These single-sided drive experiments have been modeled using radiosity and radiation-hydrodynamics codes, yielding agreement with the measured ablation rate vs. angle on the foam ball. Flux uniformity at the 1-2% level needed for high-convergence capsule implosions requires a 2-sided drive (top and bottom z-pinch) configuration. Constrained optimization methods have identified hohlraum geometries with improved symmetry.

Wire-number effects on high-power annular z-pinches and some characteristics at high wire number

DOE Office of Scientific and Technical Information (OSTI.GOV)

SANFORD,THOMAS W. L.

2000-05-23

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.

Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

NASA Astrophysics Data System (ADS)

Munaretto, S.; Chapman, B. E.; Nornberg, M. D.; Boguski, J.; DuBois, A. M.; Almagri, A. F.; Sarff, J. S.

2016-05-01

The orientation of 3D equilibria in the Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch can now be controlled with a resonant magnetic perturbation (RMP). Absent the RMP, the orientation of the stationary 3D equilibrium varies from shot to shot in a semi-random manner, making its diagnosis difficult. Produced with a poloidal array of saddle coils at the vertical insulated cut in MST's thick conducting shell, an m = 1 RMP with an amplitude br/B ˜ 10% forces the 3D structure into any desired orientation relative to MST's diagnostics. This control has led to improved diagnosis, revealing enhancements in both the central electron temperature and density. With sufficient amplitude, the RMP also inhibits the generation of high-energy (>20 keV) electrons, which otherwise emerge due to a reduction in magnetic stochasticity in the core. Field line tracing reveals that the RMP reintroduces stochasticity to the core. A m = 3 RMP of similar amplitude has little effect on the magnetic topology or the high-energy electrons.

Parameter scaling toward high-energy density in a quasi-steady flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.

2016-10-01

Sheared axial flows are utilized by the ZaP Flow Z-Pinch Experiment to stabilize MHD instabilities. The pinches formed are 50 cm long with radii ranging from 0.3 to 1.0 cm. The plasma is generated in a coaxial acceleration region, similar to a Marshall gun, which provides a steady supply of plasma for approximately 100 us. The power to the plasma is partially decoupled between the acceleration and pinch assembly regions through the use of separate power supplies. Adiabatic scaling of the Bennett relation gives targets for future devices to reach high-energy density conditions or fusion reactors. The applicability of an adiabatic assumption is explored and work is done experimentally to clarify the plasma compression process, which may be more generally polytropic. The device is capable of a much larger parameter space than previous machine iterations, allowing flexibility in the initial conditions of the compression process to preserve stability. This work is supported by DoE FES and NNSA.

Experimental investigation of the effect of insulator sleeve length on the time to pinch and multipinch formation in the plasma focus facility

NASA Astrophysics Data System (ADS)

Momenei, M.; Khodabakhshei, Z.; Panahi, N.; Mohammadi, M. A.

2017-03-01

The length of insulator sleeve is varied to investigate its effect on the pinch formation in the plasma focus facility. In this paper, the effect of insulator length on the time to pinch at various pressures and working voltages in the 1.15 kJ Mather type plasma focus is investigated. The results show that with 4.5 cm insulator length the time to pinch at all pressures is minimum. Other results also confirm that with increasing of pressure the time to pinch is increased. Moreover, with increasing working voltage the time to pinch is decreased. Pictures, captured using a digital single lens reflex (DSLR) Canon EOS 7D system, show that multipinch phenomenon is formed.

Implosion dynamics of condensed Z-pinch at the Angara-5-1 facility

NASA Astrophysics Data System (ADS)

Aleksandrov, V. V.; Grabovski, E. V.; Gritsuk, A. N.; Volobuev, I. V.; Kazakov, E. D.; Kalinin, Yu. G.; Korolev, V. D.; Laukhin, Ya. I.; Medovshchikov, S. F.; Mitrofanov, K. N.; Oleinik, G. M.; Pimenov, V. G.; Smirnova, E. A.; Ustroev, G. I.; Frolov, I. N.

2017-08-01

The implosion dynamics of a condensed Z-pinch at load currents of up to 3.5 MA and a current rise time of 100 ns was studied experimentally at the Angara-5-1 facility. To increase the energy density, 1- to 3-mm-diameter cylinders made of a deuterated polyethylene-agar-agar mixture or microporous deuterated polyethylene with a mass density of 0.03-0.5 g/cm3 were installed in the central region of the loads. The plasma spatiotemporal characteristics were studied using the diagnostic complex of the Angara-5-1 facility, including electron-optical streak and frame imaging, time-integrated X-ray imaging, soft X-ray (SXR) measurements, and vacuum UV spectroscopy. Most information on the plasma dynamics was obtained using a ten-frame X-ray camera ( E > 100 eV) with an exposure of 4 ns. SXR pulses were recorded using photoemissive vacuum X-ray detectors. The energy characteristics of neutron emission were measured using the time-offlight method with the help of scintillation detectors arranged along and across the pinch axis. The neutron yield was measured by activation detectors. The experimental results indicate that the plasma dynamics depends weakly on the load density. As a rule, two stages of plasma implosion were observed. The formation of hot plasma spots in the initial stage of plasma expansion from the pinch axis was accompanied by short pulses of SXR and neutron emission. The neutron yield reached (0.4-3) × 1010 neutrons/shot and was almost independent of the load density due to specific features of Z-pinch dynamics.

Evaluation of Particle Pinch and Diffusion Coefficients in the Edge Pedestal of DIII-D H-mode Discharges

NASA Astrophysics Data System (ADS)

Stacey, W. M.; Groebner, R. J.

2009-11-01

Momentum balance requires that the radial particle flux satisfy a pinch-diffusion relationship. The pinch can be evaluated in terms of measurable quantities (rotation velocities, Er, etc.) by the use of momentum and particle balance [1,2], the radial particle flux can be determined by momentum balance, and then the diffusion coefficient can be evaluated from the pinch diffusion relation using the measured density gradient. Applications to several DIII-D H-mode plasmas are presented. 6pt [1] W.M. Stacey, Contr. Plasma Phys. 48, 94 (2008). [2] W.M. Stacey and R.J. Groebner, Phys. Plasmas 15, 012503 (2008).

Parametric effects on pinch-off modes in liquid/liquid jet systems

NASA Astrophysics Data System (ADS)

Milosevic, Ilija N.

Many industries rely on liquid/liquid extraction systems, where jet pinch off occurs on a regular basis. Inherent short time and length scales make analytical and numerical simulation of the process very challenging. A main objective of this work was to document the details of various pinch-off modes at different length scales using Laser Induced Fluorescence and Particle Image Velocimetry. A water glycerine mixture was injected into ambient either silicone oil or 1-octanol. The resultant viscosity ratios, inner to outer fluid, were 1.6 and 2.8, respectively. Ohnesorge numbers were 0.013 for ambient silicone oil and 0.08 for ambient 1-octanol. Reynolds and Strouhal numbers ranged from 30 to 100 and 0.5 to 3.5, respectively. Decreasing the Strouhal number increased the number of drops formed per forcing. Increasing the Reynolds number suppressed satellite formation, and in some cases the number of drops decreased from two to one per cycle. Increasing the Ohnesorge number to 0.08 suppressed the pinch off yielding a longer jet with three-dimensional threads. At Ohnesorge number 0.013, increasing the forcing amplitude shortened the jet, and eventually led to a dripping mode. High-resolution measurements of pinch-off angles were compared to results from similarity theory. Two modes were investigated: drops breaking from the jet (jet/drop) and, one drop splitting into two (splitting drop). The jet/drop mode angle measurements agreed with similarity predictions. The splitting drop mode converged towards smaller angles. Scaling analysis showed that a Stokesian similarity regime applied for a neck radius of 6 microns or less. The smallest radius observed in experiments was 15 microns. Therefore, it is not known whether splitting drop mode might still converge to same behavior.

Increasing Plasma Parameters using Sheared Flow Stabilization of a Z-Pinch

NASA Astrophysics Data System (ADS)

Shumlak, Uri

2016-10-01

Recent experiments on the ZaP Flow Z-Pinch at the University of Washington have been successful in compressing the plasma column to smaller radii, producing the predicted increases in plasma density (1018 cm-3), temperature (200 eV), and magnetic fields (4 T), while maintaining plasma stability for many Alfven times (over 40 μs) using sheared plasma flows. These results indicate the suitability of the device as a discovery science platform for astrophysical and high energy density plasma research, and keeps open a possible path to achieving burning plasma conditions in a compact fusion device. Long-lived Z-pinch plasmas have been produced with dimensions of 1 cm radius and 100 cm long that are stabilized by sheared axial flows for over 1000 Alfven radial transit times. The observed plasma stability is coincident with the presence of a sheared flow as measured by time-resolved multi-chord ion Doppler spectroscopy applied to impurity ion radiation. These measurements yield insights into the evolution of the velocity profile and show that the stabilizing behavior of flow shear agrees with theoretical calculations and 2-D MHD computational simulations. The flow shear value, extent, and duration are shown to be consistent with theoretical models of the plasma viscosity, which places a design constraint on the maximum axial length of a sheared flow stabilized Z-pinch. Measurements of the magnetic field topology indicate simultaneous azimuthal symmetry and axial uniformity along the entire 100 cm length of the Z-pinch plasma. Separate control of plasma acceleration and compression have increased the accessible plasma parameters and have generated stable plasmas with radii below 0.5 cm, as measured with a high resolution digital holographic interferometer. This work was supported by Grants from U.S. DOE, NNSA, and ARPA-E.

Fusion Propulsion Z-Pinch Engine Concept

NASA Technical Reports Server (NTRS)

Miernik, J.; Statham, G.; Fabisinski, L.; Maples, C. D.; Adams, R.; Polsgrove, T.; Fincher, S.; Cassibry, J.; Cortez, R.; Turner, M.;

Hard X-ray Emission from the M87 AGN Detected with NuSTAR

NASA Astrophysics Data System (ADS)

Wong, Ka-Wah; Nemmen, Rodrigo; Irwin, Jimmy; Lin, Dacheng

2018-01-01

M87 hosts a 3–6 billion solar mass black hole with a remarkable relativistic jet that has been regularly monitored in radio to TeV bands. However, hard X-ray emission above 10keV expected to primarily come from the jet or the accretion flow had never been detected from its unresolved X-ray core. We report NuSTAR detection up to 40 keV from the the central regions of M87. Together with simultaneous Chandra observations, we have constrained the dominant hard X-ray emission to be from its unresolved X-ray core, presumably in its quiescent state. The core spectrum is well fitted by a power-law. The measured flux density at 40keV is consistent with a jet origin, although emission from the advection-dominated accretion flow cannot be completely ruled out. The detected hard X-ray emission is significantly lower than that predicted by synchrotron self-Compton models introduced to explain emission above a GeV.

Variation in work tasks in relation to pinch grip strength among middle-aged female dentists.

PubMed

Ding, Hebo; Leino-Arjas, Päivi; Murtomaa, Heikki; Takala, Esa-Pekka; Solovieva, Svetlana

2013-11-01

We aimed to investigate the relationship of task variation during dental work history with pinch grip strength among dentists. We measured pinch grip strength among 295 female Finnish dentists aged 45-63 years. Variation in dental work tasks during work history was empirically defined by cluster analysis. Three clusters of task variation emerged: low (most work time in restoration treatment/endodontics), moderate (about 50% in the former and 50% in prosthodontics/periodontics/surgery), and high (variable tasks including administrative duties). Hand radiographs were examined for the presence of OA in the wrist and each joint of the 1-3rd fingers. Information on hand-loading leisure-time activities, and joint pain was obtained by questionnaire. Glove size was used as a proxy for hand size. BMI (kg/m2) was based on measured weight and self-reported height. Dentists with low variation of work task history had an increased risk of low pinch grip strength in the right hand (OR 2.3, 95% CI 1.2-4.3), but not in the left (1.13, 0.62-2.08), compared to dentists with high task variation, independent of age, hand size, hand-loading leisure-time activities, BMI and symptomatic hand OA. The dentists with the most hand-loading tasks were at an increased risk of low pinch grip strength, independent of e.g. symptomatic hand OA. It is advisable among dentists to perform as diverse work tasks as possible to reduce the risk of decreased pinch grip strength. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Pinch-off dynamics, extensional viscosity and relaxation time of dilute and ultradilute aqueous polymer solutions

NASA Astrophysics Data System (ADS)

Biagioli, Madeleine; Dinic, Jelena; Jimenez, Leidy Nallely; Sharma, Vivek

Free surface flows and drop formation processes present in printing, jetting, spraying, and coating involve the development of columnar necks that undergo spontaneous surface-tension driven instability, thinning, and pinch-off. Stream-wise velocity gradients that arise within the thinning neck create and extensional flow field, which induces micro-structural changes within complex fluids that contribute elastic stresses, changing the thinning and pinch-off dynamics. In this contribution, we use dripping-onto-substrate (DoS) extensional rheometry technique for visualization and analysis of the pinch-off dynamics of dilute and ultra-dilute aqueous polyethylene oxide (PEO) solutions. Using a range of molecular weights, we study the effect of both elasticity and finite extensibility. Both effective relaxation time and the transient extensional viscosity are found to be strongly concentration-dependent even for highly dilute solutions.

The Ras suppressor Rsu-1 binds to the LIM 5 domain of the adaptor protein PINCH1 and participates in adhesion-related functions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dougherty, Gerard W.; Section on Structural Cell Biology, National Institute on Deafness and Communication Disorders; Chopp, Treasa

2005-05-15

Rsu-1 is a highly conserved leucine rich repeat (LRR) protein that is expressed ubiquitously in mammalian cells. Rsu-1 was identified based on its ability to inhibit transformation by Ras, and previous studies demonstrated that ectopic expression of Rsu-1 inhibited anchorage-independent growth of Ras-transformed cells and human tumor cell lines. Using GAL4-based yeast two-hybrid screening, the LIM domain protein, PINCH1, was identified as the binding partner of Rsu-1. PINCH1 is an adaptor protein that localizes to focal adhesions and it has been implicated in the regulation of adhesion functions. Subdomain mapping in yeast revealed that Rsu-1 binds to the LIM 5more » domain of PINCH1, a region not previously identified as a specific binding domain for any other protein. Additional testing demonstrated that PINCH2, which is highly homologous to PINCH1, except in the LIM 5 domain, does not interact with Rsu-1. Glutathione transferase fusion protein binding studies determined that the LRR region of Rsu-1 interacts with PINCH1. Transient expression studies using epitope-tagged Rsu-1 and PINCH1 revealed that Rsu-1 co-immunoprecipitated with PINCH1 and colocalized with vinculin at sites of focal adhesions in mammalian cells. In addition, endogenous P33 Rsu-1 from 293T cells co-immunoprecipitated with transiently expressed myc-tagged PINCH1. Furthermore, RNAi-induced reduction in Rsu-1 RNA and protein inhibited cell attachment, and while previous studies demonstrated that ectopic expression of Rsu-1 inhibited Jun kinase activation, the depletion of Rsu-1 resulted in activation of Jun and p38 stress kinases. These studies demonstrate that Rsu-1 interacts with PINCH1 in mammalian cells and functions, in part, by altering cell adhesion.« less

Combining hard and soft magnetism into a single core-shell nanoparticle to achieve both hyperthermia and image contrast

PubMed Central

Yang, Qiuhong; Gong, Maogang; Cai, Shuang; Zhang, Ti; Douglas, Justin T; Chikan, Viktor; Davies, Neal M; Lee, Phil; Choi, In-Young; Ren, Shenqiang; Forrest, M Laird

2015-01-01

Background A biocompatible core/shell structured magnetic nanoparticles (MNPs) was developed to mediate simultaneous cancer therapy and imaging. Methods & results A 22-nm MNP was first synthesized via magnetically coupling hard (FePt) and soft (Fe3O4) materials to produce high relative energy transfer. Colloidal stability of the FePt@Fe3O4 MNPs was achieved through surface modification with silane-polyethylene glycol (PEG). Intravenous administration of PEG-MNPs into tumor-bearing mice resulted in a sustained particle accumulation in the tumor region, and the tumor burden of treated mice was a third that of the mice in control groups 2 weeks after a local hyperthermia treatment. In vivo magnetic resonance imaging exhibited enhanced T2 contrast in the tumor region. Conclusion This work has demonstrated the feasibility of cancer theranostics with PEG-MNPs. PMID:26606855

Magnetoelectric confinement and stabilization of Z pinch in a soft-x-ray Ar(+8) laser.

PubMed

Szasz, J; Kiss, M; Santa, I; Szatmari, S; Kukhlevsky, S V

2013-05-03

Magnetoelectric confinement and stabilization of the plasma column in a soft-x-ray Ar(+8) laser, which is excited by a capillary Z pinch, via the combined magnetic and electric fields of the gliding surface discharge is experimentally demonstrated. Unlike soft-x-ray lasers excited by the conventional capillary Z pinches, the magnetoelectric confinement and stabilization of plasma do provide the laser operation without using any external preionization circuit.

Linking natural microstructures with numerical modeling of pinch-and-swell structures

NASA Astrophysics Data System (ADS)

Peters, Max; Berger, Alfons; Herwegh, Marco; Regenauer-Lieb, Klaus

2016-04-01

For a variety of geological problems, the change from homogeneous to localized deformation and the establishment of steady-state conditions are equally important. Here, we show that pinch-and-swell structures are ideal candidates for the study of the switch in deformation style and mechanism during ductile creep. We present an interdisciplinary approach to the onset of pinch-and-swell structures and to the flow conditions during pre- to post-localization stages in ductile rocks. For this reason, naturally boudinaged calcite veins, embedded in a calc-mylonite, and their microfabrics were investigated quantitatively. Remnants of slightly deformed calcite hosts build up the swells, showing twinning and minor dislocation glide as crystal plastic deformation mechanisms which are accompanied by subgrain rotation recrystallization (SGR). Towards the pinches, we find a gradient of severe grain size reduction through progressive SGR, developing a characteristic dislocation creep crystallographic preferred orientation (CPO). Along this gradient, the finest recrystallized calcite grains appear randomly oriented, expressed by a "smearing-out" of the CPO and missing systematics of misorientation angles in the most extended areas. We interpret this microstructure as a switch from dislocation dominated creep to grain boundary sliding processes. Further, we show that the onset of boudinage is independent on both the original orientation and grain size of calcite hosts. We implemented these microstructural observations into a layered elasto-visco-plastic finite element framework, tracing variations in grain size (Peters et al., 2015). We base the microstructural evolution on thermo-mechanical-chemical principles and end-member flow laws (Herwegh et al., 2014). The simulated pinch-and-swell structures indicate that low strain rates in the swells favor dislocation creep, whereas accelerated rates provoke continuous grain size reduction allowing strain accommodation by diffusion creep

The Pitt Innovation Challenge (PInCh): Driving Innovation in Translational Research Through an Incentive-Based, Problem-Focused Competition.

PubMed

Fitzpatrick, Nicole Edgar; Maier, John; Yasko, Laurel; Mathias, David; Qua, Kacy; Wagner, Erika; Miller, Elizabeth; Reis, Steven E

2017-05-01

Translational research aims to move scientific discoveries across the biomedical spectrum from the laboratory to humans, and to ultimately transform clinical practice and public health policies. Despite efforts to accelerate translational research through national initiatives, several major hurdles remain. The authors created the Pitt Innovation Challenge (PInCh) as an incentive-based, problem-focused approach to solving identified clinical or public health problems at the University of Pittsburgh Clinical and Translational Science Institute in spring 2014. With input from a broad range of stakeholders, PInCh leadership arrived at the challenge question: How do we empower individuals to take control of their own health outcomes? The authors developed the PInCh's three-round proposal submission and review process as well as an online contest management tool to support the process. Ninety-two teams submitted video proposals in round one. Proposals included mobile applications (29; 32%), other information technology (19; 21%), and community program (22; 24%) solutions. Ten teams advanced to the final round, where three were awarded $100,000 to implement their solution over 12 months. In a 6-month follow-up survey, 6/11 (55%) team leaders stated the PInCh helped to facilitate connections outside their normal sphere of collaborators. Additional educational training sessions related to problem-focused research will be developed. The PInCh will be expanded to engage investment and industry communities to facilitate the translation of solutions to clinical practice via commercialization pathways. External organizations and other universities will be engaged to use the PInCh as a mechanism to fuel innovation in their spaces.

Impact and hardness optimisation of composite materials inspired by the babassu nut (Orbignya speciosa).

PubMed

Staufenberg, Gerrit; Graupner, Nina; Müssig, Jörg

2015-08-20

The babassu nut is the fruit of the babassu palm Orbignya speciosa. The combination of hardness and impact strength is difficult to acquire for artificial materials, making the babassu nut a promising source for biomimetic inspiration. Unnotched Charpy impact tests, Shore D hardness tests and scanning electron microscopy were used for mechanical and microscopical analysis of the pericarp. Four major principles were found for a biomimetic approach: a hard core ((1); endocarp) is embedded in a soft outer layer of high impact strength ((2); epicarp) and is reinforced with fibres of variable fineness (3), some of which are oriented radial to the core (4). Biomimetic fibre-reinforced composites were produced using abstracted mechanisms of the babassu nut based on regenerated cellulose fibres (lyocell, L) with two different fineness values as reinforcement embedded in a polylactide (PLA) core matrix and polypropylene (PP) based outer layers. The biomimetic fibre composite reaches a significantly higher impact strength that is 1.6 times higher than the reference sample produced from a PLA/PP/L-blend. At the same time the hardness is slightly increased compared to PP/L.

Decreased short-interval intracortical inhibition correlates with better pinch strength in patients with stroke and good motor recovery.

PubMed

Ferreiro de Andrade, Karina Nocelo; Conforto, Adriana Bastos

2018-02-06

Deeper short-interval intracortical inhibition (SICI), a marker of GABA A activity, correlates with better motor performance in patients with moderate to severe hand impairments in the chronic phase after stroke. We evaluated the correlation between SICI in the affected hemisphere and pinch force of the paretic hand in well-recovered patients. We also investigated the correlation between SICI and pinch force in controls. Twenty-two subjects were included in the study. SICI was measured with a paired-pulse paradigm. The correlation between lateral pinch strength and SICI was assessed with Spearman's rho. There was a significant correlation (rho = 0.69, p = 0.014) between SICI and pinch strength in patients, but not in controls. SICI was significantly deeper in patients with greater hand weakness. These preliminary findings suggest that decreased GABA A activity in M1 AH correlates with better hand motor performance in well-recovered subjects with stroke in the chronic phase. Copyright © 2018 Elsevier Inc. All rights reserved.

Effect of Inductive Coil Geometry and Current Sheet Trajectory of a Conical Theta Pinch Pulsed Inductive Plasma Accelerator

NASA Technical Reports Server (NTRS)

Hallock, Ashley K.; Polzin, Kurt A.; Bonds, Kevin W.; Emsellem, Gregory D.

2011-01-01

Results are presented demonstrating the e ect of inductive coil geometry and current sheet trajectory on the exhaust velocity of propellant in conical theta pinch pulsed induc- tive plasma accelerators. The electromagnetic coupling between the inductive coil of the accelerator and a plasma current sheet is simulated, substituting a conical copper frustum for the plasma. The variation of system inductance as a function of plasma position is obtained by displacing the simulated current sheet from the coil while measuring the total inductance of the coil. Four coils of differing geometries were employed, and the total inductance of each coil was measured as a function of the axial displacement of two sep- arate copper frusta both having the same cone angle and length as the coil but with one compressed to a smaller size relative to the coil. The measured relationship between total coil inductance and current sheet position closes a dynamical circuit model that is used to calculate the resulting current sheet velocity for various coil and current sheet con gura- tions. The results of this model, which neglects the pinching contribution to thrust, radial propellant con nement, and plume divergence, indicate that in a conical theta pinch ge- ometry current sheet pinching is detrimental to thruster performance, reducing the kinetic energy of the exhausting propellant by up to 50% (at the upper bound for the parameter range of the study). The decrease in exhaust velocity was larger for coils and simulated current sheets of smaller half cone angles. An upper bound for the pinching contribution to thrust is estimated for typical operating parameters. Measurements of coil inductance for three di erent current sheet pinching conditions are used to estimate the magnetic pressure as a function of current sheet radial compression. The gas-dynamic contribution to axial acceleration is also estimated and shown to not compensate for the decrease in axial electromagnetic acceleration

Hotspot ignition using a Z-pinch precursor plasma in a magneto-inertial ICF scheme

NASA Astrophysics Data System (ADS)

Chittenden, J. P.; Vincent, P.; Jennings, C. A.; Ciardi, A.

2006-01-01

Precursor plasma flow is a common feature of wire array Z-pinches. The precursor flow represents a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the Z-pinch then compresses this precursor to substantially higher density. We show that if the same system can be generated with a Deuterium-Tritium plasma then the precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion. The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the pR required for ignition. A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with 50-100 MA currents and a few hundred nanosecond rise-times. This work was partially supported by the U.S. Department of Energy through cooperative agreement DE-FC03-02NA00057.

Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Munaretto, S., E-mail: smunaretto@wisc.edu; Chapman, B. E.; Nornberg, M. D.

2016-05-15

The orientation of 3D equilibria in the Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch can now be controlled with a resonant magnetic perturbation (RMP). Absent the RMP, the orientation of the stationary 3D equilibrium varies from shot to shot in a semi-random manner, making its diagnosis difficult. Produced with a poloidal array of saddle coils at the vertical insulated cut in MST's thick conducting shell, an m = 1 RMP with an amplitude b{sub r}/B ∼ 10% forces the 3D structure into any desired orientation relative to MST's diagnostics. This control has led to improvedmore » diagnosis, revealing enhancements in both the central electron temperature and density. With sufficient amplitude, the RMP also inhibits the generation of high-energy (>20 keV) electrons, which otherwise emerge due to a reduction in magnetic stochasticity in the core. Field line tracing reveals that the RMP reintroduces stochasticity to the core. A m = 3 RMP of similar amplitude has little effect on the magnetic topology or the high-energy electrons.« less

Characterisation of Plasma Filled Rod Pinch electron beam diode operation

NASA Astrophysics Data System (ADS)

MacDonald, James; Bland, Simon; Chittenden, Jeremy

2016-10-01

The plasma filled rod pinch diode (aka PFRP) offers a small radiographic spot size and a high brightness source. It operates in a very similar to plasma opening switches and dense plasma focus devices - with a plasma prefill, supplied via a number of simple coaxial plasma guns, being snowploughed along a thin rod cathode, before detaching at the end. The aim of this study is to model the PFRP and understand the factors that affect its performance, potentially improving future output. Given the dependence on the PFRP on the prefill, we are making detailed measurements of the density (1015-1018 cm-3), velocity, ionisation and temperature of the plasma emitted from a plasma gun/set of plasma guns. This will then be used to provide initial conditions to the Gorgon 3D MHD code, and the dynamics of the entire rod pinch process studied.

Geophysical Properties of Hard Rock for Investigation of Stress Fields in Deep Mines

NASA Astrophysics Data System (ADS)

Tibbo, M.; Young, R. P.; Schmitt, D. R.; Milkereit, B.

2014-12-01

A complication in geophysical monitoring of deep mines is the high-stress dependency of the physical properties of hard rocks. In-mine observations show anisotropic variability of the in situ P- and S-wave velocities and resistivity of the hard rocks that are likely related to stress field changes. As part of a comprehensive study in a deep, highly stressed mine located in Sudbury, Ontario, Canada, data from in situ monitoring of the seismicity, conductivity, stress, and stress dependent physical properties has been obtain. In-laboratory experiments are also being performed on borehole cores from the Sudbury mines. These experiments will measure the Norite borehole core's properties including elastic modulus, bulk modulus, P- and S-wave velocities, and density. Hydraulic fracturing has been successfully implemented in industries such as oil and gas and enhanced geothermal systems, and is currently being investigated as a potential method for preconditioning in mining. However, further research is required to quantify how hydraulic fractures propagate through hard, unfractured rock as well as naturally fractured rock typically found in mines. These in laboratory experiments will contribute to a hydraulic fracturing project evaluating the feasibility and effectiveness of hydraulic fracturing as a method of de-stressing hard rock mines. A tri-axial deformation cell equipped with 18 Acoustic Emission (AE) sensors will be used to bring the borehole cores to a tri-axial state of stress. The cores will then be injected with fluid until the the hydraulic fracture has propagated to the edge of the core, while AE waveforms will be digitized continuously at 10 MHz and 12-bit resolution for the duration of each experiment. These laboratory hydraulic fracture experiments will contribute to understanding how parameters including stress ratio, fluid injection rate, and viscosity, affect the fracturing process.

Optimization of a rod pinch diode radiography source at 2.3 MV

NASA Astrophysics Data System (ADS)

Menge, P. R.; Johnson, D. L.; Maenchen, J. E.; Rovang, D. C.; Oliver, B. V.; Rose, D. V.; Welch, D. R.

2003-08-01

Rod pinch diodes have shown considerable capability as high-brightness flash x-ray sources for penetrating dynamic radiography. The rod pinch diode uses a small diameter (0.4-2 mm) anode rod extended through a cathode aperture. When properly configured, the electron beam born off of the aperture edge can self-insulate and pinch onto the tip of the rod creating an intense, small x-ray source. Sandia's SABRE accelerator (2.3 MV, 40 Ω, 70 ns) has been utilized to optimize the source experimentally by maximizing the figure of merit (dose/spot diameter2) and minimizing the diode impedance droop. Many diode parameters have been examined including rod diameter, rod length, rod material, cathode aperture diameter, cathode thickness, power flow gap, vacuum quality, and severity of rod-cathode misalignment. The configuration producing the greatest figure of merit uses a 0.5 mm diameter gold rod, a 6 mm rod extension beyond the cathode aperture (diameter=8 mm), and a 10 cm power flow gap to produce up to 3.5 rad (filtered dose) at 1 m from a 0.85 mm x-ray on-axis spot (1.02 mm at 3° off axis). The resultant survey of parameter space has elucidated several physics issues that are discussed.

Mechanical Property Comparison of the Soviet BS-41 and the US M993 Armor-Penetrating Cores

DTIC Science & Technology

2016-11-23

influences the formation of cracks at the tips of hardness indentations. The observations from the optical and SEM micrographs allow one to better...core is a fine-grained WC cemented in cobalt. The M993 core was determined to have superior hardness and indentation toughness. The superior... hardness , toughness, microstructure, composition 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 20 19a

Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation.

PubMed

Rochau, Gregory A; Bailey, J E; Macfarlane, J J

2005-12-01

High-power Z pinches on Sandia National Laboratories' Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF2 were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution in each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s-->2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1sigma to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF2 samples is understood within the accuracy of the spectroscopic method.

Steric interactions determine side-chain conformations in protein cores.

PubMed

Caballero, D; Virrueta, A; O'Hern, C S; Regan, L

2016-09-01

We investigate the role of steric interactions in defining side-chain conformations in protein cores. Previously, we explored the strengths and limitations of hard-sphere dipeptide models in defining sterically allowed side-chain conformations and recapitulating key features of the side-chain dihedral angle distributions observed in high-resolution protein structures. Here, we show that modeling residues in the context of a particular protein environment, with both intra- and inter-residue steric interactions, is sufficient to specify which of the allowed side-chain conformations is adopted. This model predicts 97% of the side-chain conformations of Leu, Ile, Val, Phe, Tyr, Trp and Thr core residues to within 20°. Although the hard-sphere dipeptide model predicts the observed side-chain dihedral angle distributions for both Thr and Ser, the model including the protein environment predicts side-chain conformations to within 20° for only 60% of core Ser residues. Thus, this approach can identify the amino acids for which hard-sphere interactions alone are sufficient and those for which additional interactions are necessary to accurately predict side-chain conformations in protein cores. We also show that our approach can predict alternate side-chain conformations of core residues, which are supported by the observed electron density. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Optical Methods for Identifying Hard Clay Core Samples During Petrophysical Studies

NASA Astrophysics Data System (ADS)

Morev, A. V.; Solovyeva, A. V.; Morev, V. A.

2018-01-01

X-ray phase analysis of the general mineralogical composition of core samples from one of the West Siberian fields was performed. Electronic absorption spectra of the clay core samples with an added indicator were studied. The speed and availability of applying the two methods in petrophysical laboratories during sample preparation for standard and special studies were estimated.

Measurements of high energy photons in Z-pinch experiments on primary test stand

NASA Astrophysics Data System (ADS)

Si, Fenni; Zhang, Chuanfei; Xu, Rongkun; Yuan, Xi; Huang, Zhanchang; Xu, Zeping; Ye, Fan; Yang, Jianlun; Ning, Jiamin; Hu, Qingyuan; Zhu, Xuebin

2015-08-01

High energy photons are measured for the first time in wire-array Z-pinch experiments on the Primary Test Stand (PTS) which delivers a current up to 8 MA with a rise time of 70 ns. A special designed detecting system composed of three types of detectors is used to measure the average energy, intensity, and pulse waveform of high energy photons. Results from Pb-TLD (thermoluminescence dosimeter) detector indicate that the average energy is 480 keV (±15%). Pulse shape of high energy photons is measured by the photodiode detector consisted of scintillator coupled with a photodiode, and it is correlated with soft x-ray power by the same timing signal. Intensity is measured by both TLD and the photodiode detector, showing good accordance with each other, and it is 1010 cm-2 (±20%) at 2 m in the horizontal direction. Measurement results show that high energy photons are mainly produced in pinch regions due to accelerated electrons. PTS itself also produces high energy photons due to power flow electrons, which is one order smaller in amplitude than those from pinch region.

Measurements of high energy photons in Z-pinch experiments on primary test stand.

PubMed

Si, Fenni; Zhang, Chuanfei; Xu, Rongkun; Yuan, Xi; Huang, Zhanchang; Xu, Zeping; Ye, Fan; Yang, Jianlun; Ning, Jiamin; Hu, Qingyuan; Zhu, Xuebin

2015-08-01

High energy photons are measured for the first time in wire-array Z-pinch experiments on the Primary Test Stand (PTS) which delivers a current up to 8 MA with a rise time of 70 ns. A special designed detecting system composed of three types of detectors is used to measure the average energy, intensity, and pulse waveform of high energy photons. Results from Pb-TLD (thermoluminescence dosimeter) detector indicate that the average energy is 480 keV (±15%). Pulse shape of high energy photons is measured by the photodiode detector consisted of scintillator coupled with a photodiode, and it is correlated with soft x-ray power by the same timing signal. Intensity is measured by both TLD and the photodiode detector, showing good accordance with each other, and it is 10(10) cm(-2) (±20%) at 2 m in the horizontal direction. Measurement results show that high energy photons are mainly produced in pinch regions due to accelerated electrons. PTS itself also produces high energy photons due to power flow electrons, which is one order smaller in amplitude than those from pinch region.

Effects of smartphone overuse on hand function, pinch strength, and the median nerve.

PubMed

İnal, Esra Erkol; Demİrcİ, kadİr; Çetİntürk, Azİze; Akgönül, Mehmet; Savaş, Serpİl

2015-08-01

In this study we investigated the flexor pollicis longus (FPL) tendon and median nerve in smartphone users by ultrasonography to assess the effects of smartphone addiction on the clinical and functional status of the hands. One hundred two students were divided into 3 groups: non-users, and high or low smartphone users. Smartphone Addiction Scale (SAS) scores and grip and pinch strengths were recorded. Pain in thumb movement and rest and hand function were evaluated on the visual analog scale (VAS) and the Duruöz Hand Index (DHI), respectively. The cross-sectional areas (CSAs) of the median nerve and the FPL tendon were calculated bilaterally using ultrasonography. Significantly higher median nerve CSAs were observed in the dominant hands of the high smartphone users than in the non-dominant hands (P<0.001). SAS scores correlated with VAS pain for movement and rest, DHI scores, and pinch strength (P<0.05; r=0.345, 0.272, 0.245, and 0.281, respectively). Smartphone overuse enlarges the median nerve, causes pain in the thumb, and decreases pinch strength and hand functions. © 2015 Wiley Periodicals, Inc.

Scaling of confinement and profiles in the EXTRAP T2 reversed-field pinch

NASA Astrophysics Data System (ADS)

Welander, A.

1999-01-01

In the EXTRAP T2 reversed-field pinch the diagnostic techniques for the measurement of electron density and temperature include; Thomson scattering which gives values at three radial positions in the core (r/a = 0, 0.28, 0.56), Langmuir probes which give values at the edge (r/a > 0.9) and interferometry which gives a line-averaged density. The empirical scaling of electron density and temperature including profile information with global plasma parameters has been studied. The density profile is subject to large variations, with an average parabolic shape when the density is low and flatter shapes when the density is increased. The change in the profile shape can be attributed to a shift in the penetration length of neutrals from the vicinity of the wall. The temperature scales roughly as I/n1/2 where I is the plasma current and n is the density. The temperature profile is always quite flat with lower variations and there is a tendency for a flatter profile at higher temperatures.

Spontaneous quasi single helicity regimes in EXTRAP T2R reversed-field pinch

NASA Astrophysics Data System (ADS)

Frassinetti, L.; Brunsell, P. R.; Drake, J. R.; Menmuir, S.; Cecconello, M.

2007-11-01

In recent years, good progress toward a better understanding and control of the plasma performance in reversed-field pinch devices has been made. These improvements consist both of the discovery of spontaneous plasma regimes, termed the quasi single helicity (QSH) regime, in which part of the plasma core is no longer stochastic, and of the development of techniques for active control of plasma instabilities. In this paper, a systematic study of spontaneous QSH in the EXTRAP T2R device [P. R. Brunsell, H. Bergsaker, M. Cecconello et al., Plasma Phys. Control. Fusion 43, 1457 (2001)] is presented. In this device, QSH states can occur spontaneously and it is associated with magnetic and thermal structures. A statistical analysis to determine the most favorable experimental conditions to have a transition to the QSH regime will be presented. The results described here are useful to understand the underlying properties of QSH regimes in view of future applications of the QSH active control in EXTRAP T2R; they are also important to have a comparison with the QSH studied in other devices.

Tuning the bridging attraction between large hard particles by the softness of small microgels.

PubMed

Luo, Junhua; Yuan, Guangcui; Han, Charles C

2016-09-20

In this study, the attraction between large hard polystyrene (PS) spheres is studied by using three types of small microgels as bridging agents. One is a purely soft poly(N-isopropylacrylamide) (PNIPAM) microgel, the other two have a non-deformable PS hard core surrounded by a soft PNIPAM shell but are different in the core-shell ratio. The affinity for bridging the large PS spheres is provided and thus affected by the PNIPAM constituent in the microgels. The bridging effects caused by the microgels can be indirectly incorporated into their influence on the effective attraction interaction between the large hard spheres, since the size of the microgels is very small in comparison to the size of the PS hard spheres. At a given volume fraction of large PS spheres, they behave essentially as hard spheres in the absence of small microgels. By gradually adding the microgels, the large spheres are connected to each other through the bridging of small particles until the attraction strength reaches a maximum value, after which adding more small particles slowly decreases the effective attraction strength and eventually the large particles disperse individually when saturated adsorption is achieved. The aggregation and gelation behaviors triggered by these three types of small microgels are compared and discussed. A way to tune the strength and range of the short-range attractive potential via changing the softness of bridging microgels (which can be achieved either by using core-shell microgels or by changing the temperature) is proposed.

AN ACCELERATION MECHANISM FOR NEUTRON PRODUCTION IN Z-PINCH DISCHARGES,

DTIC Science & Technology

A model has been developed for the acceleration of deuterons in the tightly compressed column of a z-pinch discharge, in particular that of a plasma ... focus discharge. It was assumed that an annular current distribution undergoes a rapidly contracting transition to an axially peaked distribution, and

Theory and computer simulation of hard-core Yukawa mixtures: thermodynamical, structural and phase coexistence properties.

PubMed

Mkanya, Anele; Pellicane, Giuseppe; Pini, Davide; Caccamo, Carlo

2017-09-13

We report extensive calculations, based on the modified hypernetted chain (MHNC) theory, on the hierarchical reference theory (HRT), and on Monte Carlo simulations, of thermodynamical, structural and phase coexistence properties of symmetric binary hard-core Yukawa mixtures (HCYM) with attractive interactions at equal species concentration. The obtained results are throughout compared with those available in the literature for the same systems. It turns out that the MHNC predictions for thermodynamic and structural quantities are quite accurate in comparison with the MC data. The HRT is equally accurate for thermodynamics, and slightly less accurate for structure. Liquid-vapor (LV) and liquid-liquid (LL) consolute coexistence conditions as emerging from simulations, are also highly satisfactorily reproduced by both the MHNC and HRT for relatively long ranged potentials. When the potential range reduces, the MHNC faces problems in determining the LV binodal line; however, the LL consolute line and the critical end point (CEP) temperature and density turn out to be still satisfactorily predicted within this theory. The HRT also predicts with good accuracy the CEP position. The possibility of employing liquid state theories HCYM for the purpose of reliably determining phase equilibria in multicomponent colloidal fluids of current technological interest, is discussed.

Theory and computer simulation of hard-core Yukawa mixtures: thermodynamical, structural and phase coexistence properties

NASA Astrophysics Data System (ADS)

Mkanya, Anele; Pellicane, Giuseppe; Pini, Davide; Caccamo, Carlo

2017-09-01

We report extensive calculations, based on the modified hypernetted chain (MHNC) theory, on the hierarchical reference theory (HRT), and on Monte Carlo simulations, of thermodynamical, structural and phase coexistence properties of symmetric binary hard-core Yukawa mixtures (HCYM) with attractive interactions at equal species concentration. The obtained results are throughout compared with those available in the literature for the same systems. It turns out that the MHNC predictions for thermodynamic and structural quantities are quite accurate in comparison with the MC data. The HRT is equally accurate for thermodynamics, and slightly less accurate for structure. Liquid-vapor (LV) and liquid-liquid (LL) consolute coexistence conditions as emerging from simulations, are also highly satisfactorily reproduced by both the MHNC and HRT for relatively long ranged potentials. When the potential range reduces, the MHNC faces problems in determining the LV binodal line; however, the LL consolute line and the critical end point (CEP) temperature and density turn out to be still satisfactorily predicted within this theory. The HRT also predicts with good accuracy the CEP position. The possibility of employing liquid state theories HCYM for the purpose of reliably determining phase equilibria in multicomponent colloidal fluids of current technological interest, is discussed.

IB-LBM study on cell sorting by pinched flow fractionation.

PubMed

Ma, Jingtao; Xu, Yuanqing; Tian, Fangbao; Tang, Xiaoying

2014-01-01

Separation of two categories of cells in pinched flow fractionation(PFF) device is simulated by employing IB-LBM. The separation performances at low Reynolds number (about 1) under different pinched segment widths, flow ratios, cell features, and distances between neighboring cells are studied and the results are compared with those predicted by the empirical formula. The simulation indicates that the diluent flow rate should approximate to or more than the flow rate of particle solution in order to get a relatively ideal separation performance. The discrepancy of outflow position between numerical simulation and the empirical prediction enlarges, when the cells become more flexible. Too short distance between two neighboring cells could lead to cell banding which would result in incomplete separation, and the relative position of two neighboring cells influences the banding of cells. The present study will probably provide some new applications of PFF, and make some suggestions on the design of PFF devices.

Hard-X-Ray-Induced Multistep Ultrafast Dissociation

NASA Astrophysics Data System (ADS)

Travnikova, Oksana; Marchenko, Tatiana; Goldsztejn, Gildas; Jänkälä, Kari; Sisourat, Nicolas; Carniato, Stéphane; Guillemin, Renaud; Journel, Loïc; Céolin, Denis; Püttner, Ralph; Iwayama, Hiroshi; Shigemasa, Eiji; Piancastelli, Maria Novella; Simon, Marc

2016-05-01

Creation of deep core holes with very short (τ ≤1 fs ) lifetimes triggers a chain of relaxation events leading to extensive nuclear dynamics on a few-femtosecond time scale. Here we demonstrate a general multistep ultrafast dissociation on an example of HCl following Cl 1 s →σ* excitation. Intermediate states with one or multiple holes in the shallower core electron shells are generated in the course of the decay cascades. The repulsive character and large gradients of the potential energy surfaces of these intermediates enable ultrafast fragmentation after the absorption of a hard x-ray photon.

Mechanical properties of commercial high strength ceramic core materials.

PubMed

Rizkalla, A S; Jones, D W

2004-02-01

The objective of the present study is to evaluate and compare the flexural strength, dynamic elastic moduli and true hardness (H(o)) values of commercial Vita In-Ceram alumina core and Vita In-Ceram matrix glass with the standard aluminous porcelain (Hi-Ceram and Vitadur), Vitadur N and Dicor glass and glass-ceramic. The flexural strength was evaluated (n=5) using 3-point loading and a servo hydraulic Instron testing machine at a cross head speed of 0.5 mm/min. The density of the specimens (n=3) was measured by means of the water displacement technique. Dynamic Young's shear and bulk moduli and Poisson's ratio (n=3) were measured using a non-destructive ultrasonic technique using 10 MHz lithium niobate crystals. The true hardness (n=3) was measured using a Knoop indenter and the fracture toughness (n=3) was determined using a Vickers indenter and a Tukon hardness tester. Statistical analysis of the data was conducted using ANOVA and a Student-Newman-Keuls (SNK) rank order multiple comparative test. The SNK rank order test analysis of the mean flexural strength was able to separate five commercial core materials into three significant groups at p=0.05. Vita In-Ceram alumina and IPS Empress 2 exhibited significantly higher flexural strength than aluminous porcelains and IPS Empress at p=0.05. The dynamic elastic moduli and true hardness of Vita In-Ceram alumina core were significantly higher than the rest of the commercial ceramic core materials at p=0.05. The ultrasonic test method is a valuable mechanical characterization tool and was able to statistically discriminate between the chemical and structural differences within dental ceramic materials. Significant correlation was obtained between the dynamic Young's modulus and true hardness, p=0.05.

In vitro evaluation of five core materials.

PubMed

Gu, Steven; Rasimick, Brian J; Deutsch, Allan S; Musikant, Barry L

2007-01-01

This in vitro study determined the fracture strength of five core materials supported by two different endodontic dowels. Diametral tensile strength and microhardness of the three resin composite core materials used in this study were also tested. The fracture strength study used one lanthanide-reinforced flowable resin composite (Ti-Core Auto E), one titanium- and lanthanide-reinforced composite (Ti-Core), one lanthanide-reinforced composite (Ti-Core Natural), and two metal-reinforced glass ionomer core materials (Ketac Silver and GC Miracle Mix). Two types of dowels were used: a multitiered, split-shank threaded dowel with a flange (#1 Flexi-Flange) and one without a flange design (#1 Flexi-Post). The specimens were divided into ten groups. Each tooth/dowel and core specimen was placed in a special jig at 45 degrees and subjected to a load by a universal testing machine. The diametral tensile strength and the microhardness of the three resin composite core materials were measured by a universal testing machine and Barcol hardness tester, respectively. All test groups contained ten specimens. The fracture strength value of the resin composite core materials was significantly larger ( p < 0.0001) than those for the metal-reinforced glass-ionomer core materials. Analysis of variance (ANOVA) also showed that the Flexi-Flange dowel interacted with Ti-Core and Ti-Core Auto E to significantly ( p < 0.0013) increase the fracture strength relative to the Flexi-Post. One-way ANOVA revealed that there were no significant differences between them in terms of diametral tensile strength. The Barcol hardness values of the composite core materials were statistically different ( p < 0.0001), with the Ti-Core the highest, followed by Ti-Core Natural, then Ti-Core Auto E. Resin composite core material performed better than glass ionomer material in this in vitro study. The flowable composite core material performed about the same in terms of fracture strength and diametral tensile

Deconvolution of Stark broadened spectra for multi-point density measurements in a flow Z-pinch

DOE PAGES

Vogman, G. V.; Shumlak, U.

2011-10-13

Stark broadened emission spectra, once separated from other broadening effects, provide a convenient non-perturbing means of making plasma density measurements. A deconvolution technique has been developed to measure plasma densities in the ZaP flow Z-pinch experiment. The ZaP experiment uses sheared flow to mitigate MHD instabilities. The pinches exhibit Stark broadened emission spectra, which are captured at 20 locations using a multi-chord spectroscopic system. Spectra that are time- and chord-integrated are well approximated by a Voigt function. The proposed method simultaneously resolves plasma electron density and ion temperature by deconvolving the spectral Voigt profile into constituent functions: a Gaussian functionmore » associated with instrument effects and Doppler broadening by temperature; and a Lorentzian function associated with Stark broadening by electron density. The method uses analytic Fourier transforms of the constituent functions to fit the Voigt profile in the Fourier domain. The method is discussed and compared to a basic least-squares fit. The Fourier transform fitting routine requires fewer fitting parameters and shows promise in being less susceptible to instrumental noise and to contamination from neighboring spectral lines. The method is evaluated and tested using simulated lines and is applied to experimental data for the 229.69 nm C III line from multiple chords to determine plasma density and temperature across the diameter of the pinch. As a result, these measurements are used to gain a better understanding of Z-pinch equilibria.« less

Deconvolution of Stark broadened spectra for multi-point density measurements in a flow Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vogman, G. V.; Shumlak, U.

2011-10-15

Stark broadened emission spectra, once separated from other broadening effects, provide a convenient non-perturbing means of making plasma density measurements. A deconvolution technique has been developed to measure plasma densities in the ZaP flow Z-pinch experiment. The ZaP experiment uses sheared flow to mitigate MHD instabilities. The pinches exhibit Stark broadened emission spectra, which are captured at 20 locations using a multi-chord spectroscopic system. Spectra that are time- and chord-integrated are well approximated by a Voigt function. The proposed method simultaneously resolves plasma electron density and ion temperature by deconvolving the spectral Voigt profile into constituent functions: a Gaussian functionmore » associated with instrument effects and Doppler broadening by temperature; and a Lorentzian function associated with Stark broadening by electron density. The method uses analytic Fourier transforms of the constituent functions to fit the Voigt profile in the Fourier domain. The method is discussed and compared to a basic least-squares fit. The Fourier transform fitting routine requires fewer fitting parameters and shows promise in being less susceptible to instrumental noise and to contamination from neighboring spectral lines. The method is evaluated and tested using simulated lines and is applied to experimental data for the 229.69 nm C III line from multiple chords to determine plasma density and temperature across the diameter of the pinch. These measurements are used to gain a better understanding of Z-pinch equilibria.« less

An investigation of transient pressures and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with several plasma diagnostics; they were: a rapid response pressure transducer, a magnetic field probe, a voltage probe, and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior: (1) strong axial pressure asymmetry noted early in plasma column lifetime, (2) followed by plasma heating in which there is a rapid rise in static pressure, and (3) a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating could be attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity.

The quantum pinch effect in semiconducting quantum wires: A bird’s-eye view

NASA Astrophysics Data System (ADS)

Kushwaha, Manvir S.

2016-01-01

Those who measure success with culmination do not seem to be aware that life is a journey not a destination. This spirit is best reflected in the unceasing failures in efforts for solving the problem of controlled thermonuclear fusion for even the simplest pinches for over decades; and the nature keeps us challenging with examples. However, these efforts have permitted researchers the obtention of a dense plasma with a lifetime that, albeit short, is sufficient to study the physics of the pinch effect, to create methods of plasma diagnostics, and to develop a modern theory of plasma processes. Most importantly, they have impregnated the solid state plasmas, particularly the electron-hole plasmas in semiconductors, which do not suffer from the issues related with the confinement and which have demonstrated their potential not only for the fundamental physics but also for the device physics. Here, we report on a two-component, cylindrical, quasi-one-dimensional quantum plasma subjected to a radial confining harmonic potential and an applied magnetic field in the symmetric gauge. It is demonstrated that such a system, as can be realized in semiconducting quantum wires, offers an excellent medium for observing the quantum pinch effect at low temperatures. An exact analytical solution of the problem allows us to make significant observations: Surprisingly, in contrast to the classical pinch effect, the particle density as well as the current density display a determinable maximum before attaining a minimum at the surface of the quantum wire. The effect will persist as long as the equilibrium pair density is sustained. Therefore, the technological promise that emerges is the route to the precise electronic devices that will control the particle beams at the nanoscale.

Policy and science in children's health and environment: recommendations from the PINCHE project.

PubMed

van den Hazel, Peter; Zuurbier, Moniek; Bistrup, Marie Louise; Busby, Chris; Fucic, Aleksandra; Koppe, Janna G; Lundqvist, Christofer; Ronchetti, Roberto; ten Tusscher, Gavin

2006-10-01

Policy recommendations result from the discussions and analysis of the present situation in environment and health. Such analysis was performed in PINCHE. This led to recommendations based on the scientific literature. In the field of children's environmental health the policy process will follow more or less fixed rules, but this process is still at an early level of development. The link between science and policy still faces many challenges. Scientific assessment of environmental risk must recognize and tackle the problems of data sets, variability of human and environmental systems, the range, spatial and temporal diffusion of potential health effects and many biases and confounding factors. The PINCHE network recommends a general improvement of the supporting scientific fields in environment and health. Assessments from epidemiology or toxicology should play a key role in influencing science-policy decisions in programmes that are intended to inform the public policy process. Scientific committees at a local level could play a role. The relation between health and environment needs to be better incorporated in training and education. There is a need for harmonization of data production and use. The priorities in PINCHE focus on the most important issues. A classification of low, medium or high priority for action was used to describe a range of different environmental stressors. PINCHE provided recommendations to reduce exposure for children. Exposure reduction is not always linked to improved health in the short term, but it will reduce the body burden of accumulating chemicals in children. A strategic choice is reduction of exposure of children to compounds by changing production techniques or by increasing the distance of child specific settings to sources. The contribution of all players in the production, distribution and use of scientific knowledge in the field of children's environmental health is necessary.

Effects of the resistivity profile on the formation of a reversed configuration and single helicity states in compressible simulations of the reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Onofri, M.; Malara, F.

2013-10-15

Compressible magnetohydrodynamics simulations of the reversed-field pinch (RFP) are presented. Previous simulations of the RFP, including density and pressure evolution, showed that a stationary state with a reversed toroidal magnetic field could not be obtained, contrary to the results produced with numerical codes neglecting density and pressure dynamics. The simulations described in the present paper show that including density and pressure evolution, a stationary RFP configuration can be obtained if the resistivity has a radial profile steeply increasing close to the wall. Such resistivity profile is more realistic than a uniform resistivity, since the temperature at the wall is lowermore » than in the plasma core.« less

Measurement and analysis of x-ray absorption in Al and MgF2 plasmas heated by Z-pinch radiation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

MacFarlane, Joseph John; Rochau, Gregory Alan; Bailey, James E.

2005-06-01

High-power Z pinches on Sandia National Laboratories Z facility can be used in a variety of experiments to radiatively heat samples placed some distance away from the Z-pinch plasma. In such experiments, the heating radiation spectrum is influenced by both the Z-pinch emission and the re-emission of radiation from the high-Z surfaces that make up the Z-pinch diode. To test the understanding of the amplitude and spectral distribution of the heating radiation, thin foils containing both Al and MgF{sub 2} were heated by a 100-130 TW Z pinch. The heating of these samples was studied through the ionization distribution inmore » each material as measured by x-ray absorption spectra. The resulting plasma conditions are inferred from a least-squares comparison between the measured spectra and calculations of the Al and Mg 1s {yields} 2p absorption over a large range of temperatures and densities. These plasma conditions are then compared to radiation-hydrodynamics simulations of the sample dynamics and are found to agree within 1{sigma} to the best-fit conditions. This agreement indicates that both the driving radiation spectrum and the heating of the Al and MgF{sub 2} samples is understood within the accuracy of the spectroscopic method.« less

Ion heating during reconnection in the Madison Symmetric Torus reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangadhara, S.; Ennis, D. A.; Hartog, D. J. den

2008-05-15

Measurements of localized ion heating during magnetic reconnection in the Madison Symmetric Torus reversed field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] are presented using two beam-based diagnostics: Charge exchange recombination spectroscopy and Rutherford scattering. Data have been collected from three types of impulsive reconnection event, in which the resistive tearing mode activity associated with reconnection is present either in the edge plasma, the core plasma, or throughout the plasma volume. A drop in the stored magnetic energy is required for ion heating to bemore » observed during magnetic reconnection, and when this occurs, heating is concentrated in regions where reconnection is taking place. The magnitude of the observed temperature rise during reconnection varies with ion species, suggesting that the heating mechanism has a mass and/or charge dependence. Both the magnitude and spatial structure of the observed temperature rise also depend on the plasma current and density. Nonetheless, the fraction of released magnetic energy converted to ion thermal energy remains roughly constant over a range of plasma conditions.« less

Crossed-swords, capsule-pinch technique for capsulotomy in pediatric and/or loose lens cataract extraction.

PubMed

Snyder, Michael E; Lindsell, Luke B

2010-02-01

Puncturing the anterior capsule in a patient with a very soft lens, an elastic capsule, and/or deficient zonular countertraction can be challenging even with a sharp needle or blade. The crossed-swords, capsule-pinch technique capitalizes on opposing forces from 2 needles directed toward each other with a "pinch" of the capsule between their tips. This affords a controlled and facile puncture of the capsule without creating stress on the zonules or anteroposterior displacement of the lens. Copyright 2010 ASCRS and ESCRS. Published by Elsevier Inc. All rights reserved.

250 kA compact linear transformer driver for wire array z-pinch loads

NASA Astrophysics Data System (ADS)

Bott, S. C.; Haas, D. M.; Madden, R. E.; Ueda, U.; Eshaq, Y.; Collins, G., IV; Gunasekera, K.; Mariscal, D.; Peebles, J.; Beg, F. N.; Mazarakis, M.; Struve, K.; Sharpe, R.

2011-05-01

We present the application of a short rise (˜150ns) 250 kA linear transformer driver (LTD) to wire array z-pinch loads for the first time. The generator is a modification of a previous driver in which a new conical power feed provides a low inductance coupling to wire loads. Performance of the new design using both short circuit and plasma loads is presented and discussed. The final design delivers ˜200kA to a wire array load which is in good agreement with SCREAMER calculations using a simplified representative circuit. Example results demonstrate successful experiments using cylindrical, conical, and inverse wire arrays as well as previously published work on x-pinch loads.

Z-Pinch Magneto-Inertial Fusion Propulsion Engine Design Concept

NASA Technical Reports Server (NTRS)

Miernik, Janie H.; Statham, Geoffrey; Adams, Robert B.; Polsgrove, Tara; Fincher, Sharon; Fabisinski, Leo; Maples, C. Dauphne; Percy, Thomas K.; Cortez, Ross J.; Cassibry, Jason

2011-01-01

Fusion-based nuclear propulsion has the potential to enable fast interplanetary transportation. Due to the great distances between the planets of our solar system and the harmful radiation environment of interplanetary space, high specific impulse (Isp) propulsion in vehicles with high payload mass fractions must be developed to provide practical and safe vehicles for human spaceflight missions. Magneto-Inertial Fusion (MIF) is an approach which has been shown to potentially lead to a low cost, small fusion reactor/engine assembly (1). The Z-Pinch dense plasma focus method is an MIF concept in which a column of gas is compressed to thermonuclear conditions by an estimated axial current of approximately 100 MA. Recent advancements in experiments and the theoretical understanding of this concept suggest favorable scaling of fusion power output yield as I(sup 4) (2). The magnetic field resulting from the large current compresses the plasma to fusion conditions, and this is repeated over short timescales (10(exp -6) sec). This plasma formation is widely used in the field of Nuclear Weapons Effects (NWE) testing in the defense industry, as well as in fusion energy research. There is a wealth of literature characterizing Z-Pinch physics and existing models (3-5). In order to be useful in engineering analysis, a simplified Z-Pinch fusion thermodynamic model was developed to determine the quantity of plasma, plasma temperature, rate of expansion, energy production, etc. to calculate the parameters that characterize a propulsion system. The amount of nuclear fuel per pulse, mixture ratio of the D-T and nozzle liner propellant, and assumptions about the efficiency of the engine, enabled the sizing of the propulsion system and resulted in an estimate of the thrust and Isp of a Z-Pinch fusion propulsion system for the concept vehicle. MIF requires a magnetic nozzle to contain and direct the nuclear pulses, as well as a robust structure and radiation shielding. The structure

Anomalous pinch of turbulent plasmas driven by the magnetic-drift-induced Lorentz force through the Stokes-Einstein relation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shaojie, E-mail: wangsj@ustc.edu.cn

It is found that the Lorentz force generated by the magnetic drift drives a generic plasma pinch flux of particle, energy and momentum through the Stokes-Einstein relation. The proposed theoretical model applies for both electrons and ions, trapped particles, and passing particles. An anomalous parallel current pinch due to the electrostatic turbulence with long parallel wave-length is predicted.

Crabs grab strongly depending on mechanical advantages of pinching and disarticulation of chela.

PubMed

Fujiwara, Shin-Ichi; Kawai, Hiroki

2016-10-01

A small morphological variation of an organ may cause a major change of its function in animal evolution. The function of decapod chela varies considerably among taxa, between sex, and even within an individual, but also retains a simple mechanism of motion. Therefore, the decapod chela is a suitable structure to study the evolutionary process of functional diversifications, although the relationship of form and function is inadequately understood, yet. We estimated the mechanical advantages of pinching and passive disarticulation resistance, and chela size relative to the carapace in 317 chelae of 168 decapod specimens, and compared these indices with the functions of each chela. Our study revealed that mechanical advantages of pinching efficiency and passive disarticulation resistance were greatest in shell-crushing chelae, followed by gripping and pinching chelae, whereas the chela size relative to the carapace was not related to differences among these functions. We also found that the chelae are designed to retain the ratio between depth and width of the proximal dactylus. In the evolutionary process of decapods, the diversifications of chela functions were accompanied by the diversifications of the mechanical advantages, and played an essential role in their ecological diversification. J. Morphol. 277:1259-1272, 2016. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

The functional link between tail-pinch-induced food intake and emotionality and its possible role in stress coping in rats.

PubMed

Aso-Someya, Nami; Narikiyo, Kimiya; Masuda, Akira; Aou, Shuji

2018-02-08

Tail pinch facilitates eating in rats. We investigated an unidentified link between tail-pinch-induced eating behavior and individual emotionality in male Sprague-Dawley rats. Anxiety-like behavior was assessed on the elevated plus maze (EPM) and in the open field test (OFT). Tail-pinch-induced eating was observed as follows: After a 30-min habituation period, the tail pinch was applied for 5 min, followed by a 30-min recovery period. During the habituation and recovery periods, rats were allowed to access food ad libitum. During the recovery period, 14 of 24 rats ate more food than during the habituation period. Thus, we named them "high responders" and the others as "low responders". The food intake was significantly greater, while the times spent in the open arms in the EPM and in the center area in the OFT were significantly shorter in high responders than in low responders. This result suggests that the rats consuming more food after mild stress have higher anxiety.

Interbrachial Pinch by Trapezius Transfer in Amyoplasia Congenita: A Case Report

PubMed Central

Thione, Alessandro; Cavadas, Pedro C.; Rubi, Carlo G.

2017-01-01

Summary: Amyoplasia congenita, or “classic distal arthrogryposis,” is the most common disorder among the congenital, non-progressive, multiple joint contractural conditions named arthrogryposis. The cause remains unknown, and it occurs sporadically. Abnormal neurological examination indicates that movement in utero was diminished as a result of an abnormality of the central or peripheral nervous system, the motor end plate, or muscle. The absence of central neural pathology indicates the origin in akinetic fetal condition. Three weeks are enough to cause muscle weakness and joint fibrosis. Joint contractures in amyoplasia are often rigid and refractory to nonoperative treatment such as passive stretching. Surgery is focused on each patient's need respecting adaptive maneuvers to accomplish daily tasks. We present a case in which pectoral major muscle had no strength for pinching; a trapezius muscle transfer was planned to obtain an interbrachial pinch useful for grasping. PMID:28607845

Improved confinement region without large magnetohydrodynamic activity in TPE-RX reversed-field pinch plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yambe, Kiyoyuki; Hirano, Yoichi; Sakakita, Hajime

2014-11-15

We found that spontaneous improved confinement was brought about depending on the operating region in the Toroidal Pinch Experiment-Reversed eXperiment (TPE-RX) reversed-field pinch plasma [Y. Yagi et al., Fusion Eng. Des. 45, 421 (1999)]. Gradual decay of the toroidal magnetic field at plasma surface B{sub tw} reversal makes it possible to realize a prolonged discharge, and the poloidal beta value and energy confinement time increase in the latter half of the discharge, where reversal and pinch parameters become shallow and low, respectively. In the latter half of the discharge, the plasma current and volume-averaged toroidal magnetic field 〈B{sub t}〉 increasemore » again, the electron density slowly decays, the electron temperature and soft X-ray radiation intensity increase, and the magnetic fluctuations are markedly reduced. In this period of improved confinement, the value of (〈B{sub t}〉-B{sub tw})/B{sub pw}, where B{sub pw} is the poloidal magnetic field at the plasma surface, stays almost constant, which indicates that the dynamo action occurs without large magnetohydrodynamic activities.« less

Capsule symmetry sensitivity and hohlraum symmetry calculations for the z-pinch driven hohlraum high-yield concept

NASA Astrophysics Data System (ADS)

Vesey, Roger; Cuneo, M. E.; Hanson Porter, D. L., Jr.; Mehlhorn, T. A.; Ruggles, L. E.; Simpson, W. W.; Hammer, J. H.; Landen, O.

2000-10-01

Capsule radiation symmetry is a crucial issue in the design of the z-pinch driven hohlraum approach to high-yield inertial confinement fusion [1]. Capsule symmetry may be influenced by power imbalance of the two z-pinch x-ray sources, and by hohlraum effects (geometry, time-dependent albedo, wall motion). We have conducted two-dimensional radiation-hydrodynamics calculations to estimate the symmetry sensitivity of the 220 eV beryllium ablator capsule that nominally yields 400 MJ in this concept. These estimates then determine the symmetry requirements to be met by the hohlraum design (for even Legendre modes) and by the top-bottom pinch imbalance and mistiming (for odd Legendre modes). We have used a combination of 2- and 3-D radiosity ("viewfactor"), and 2-D radiation-hydrodynamics calculations to identify hohlraum geometries that meet these symmetry requirements for high-yield, and are testing these models against ongoing Z foam ball symmetry experiments. 1. J. H. Hammer et al., Phys. Plas. 6, 2129 (1999).

An investigation of transient pressure and plasma properties in a pinched plasma column. M.S. Thesis

NASA Technical Reports Server (NTRS)

Stover, E. K.; York, T. M.

1971-01-01

The transient pinched plasma column generated in a linear Z-pinch was studied experimentally and analytically. The plasma column was investigated experimentally with the following plasma diagnostics: a special rapid response pressure transducer, a magnetic field probe, a voltage probe and discharge luminosity. Axial pressure profiles on the discharge chamber axis were used to identify three characteristic regions of plasma column behavior; they were in temporal sequence: strong axial pressure asymmetry noted early in plasma column lifetime followed by plasma heating in which there is a rapid rise in static pressure and a slight decrease static pressure before plasma column breakup. Plasma column lifetime was approximately 5 microseconds. The axial pressure asymmetry was attributed to nonsimultaneous pinching of the imploding current sheet along the discharge chamber axis. The rapid heating is attributed in part to viscous effects introduced by radial gradients in the axial streaming velocity. Turbulent heating arising from discharge current excitation of the ion acoustic wave instability is also considered a possible heating mechanism.

Beyond packing of hard spheres: The effects of core softness, non-additivity, intermediate-range repulsion, and many-body interactions on the glass-forming ability of bulk metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Kai; Fan, Meng; Liu, Yanhui

When a liquid is cooled well below its melting temperature at a rate that exceeds the critical cooling rate R{sub c}, the crystalline state is bypassed and a metastable, amorphous glassy state forms instead. R{sub c} (or the corresponding critical casting thickness d{sub c}) characterizes the glass-forming ability (GFA) of each material. While silica is an excellent glass-former with small R{sub c} < 10{sup −2} K/s, pure metals and most alloys are typically poor glass-formers with large R{sub c} > 10{sup 10} K/s. Only in the past thirty years have bulk metallic glasses (BMGs) been identified with R{sub c} approachingmore » that for silica. Recent simulations have shown that simple, hard-sphere models are able to identify the atomic size ratio and number fraction regime where BMGs exist with critical cooling rates more than 13 orders of magnitude smaller than those for pure metals. However, there are a number of other features of interatomic potentials beyond hard-core interactions. How do these other features affect the glass-forming ability of BMGs? In this manuscript, we perform molecular dynamics simulations to determine how variations in the softness and non-additivity of the repulsive core and form of the interatomic pair potential at intermediate distances affect the GFA of binary alloys. These variations in the interatomic pair potential allow us to introduce geometric frustration and change the crystal phases that compete with glass formation. We also investigate the effect of tuning the strength of the many-body interactions from zero to the full embedded atom model on the GFA for pure metals. We then employ the full embedded atom model for binary BMGs and show that hard-core interactions play the dominant role in setting the GFA of alloys, while other features of the interatomic potential only change the GFA by one to two orders of magnitude. Despite their perturbative effect, understanding the detailed form of the intermetallic potential is important

Observation of emission process in hydrogen-like nitrogen Z-pinch discharge with time integrated soft X-ray spectrum pinhole image

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sakai, Y.; Kumai, H.; Nakanishi, Y.

2013-02-15

The emission spectra of hydrogen-like nitrogen Balmer at the wavelength of 13.4 nm in capillary Z-pinch discharge plasma are experimentally examined. Ionization to fully strip nitrogen at the pinch maximum, and subsequent rapid expansion cooling are required to establish the population inversion between the principal quantum number of n = 2 and n = 3. The ionization and recombination processes with estimated plasma parameters are evaluated by utilizing a time integrated spectrum pinhole image containing radial spatial information. A cylindrical capillary plasma is pinched by a triangular pulsed current with peak amplitude of 50 kA and pulse width of 50more » ns.« less

Ultrasonic Drilling and Coring

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

1998-01-01

A novel drilling and coring device, driven by a combination, of sonic and ultrasonic vibration, was developed. The device is applicable to soft and hard objects using low axial load and potentially operational under extreme conditions. The device has numerous potential planetary applications. Significant potential for commercialization in construction, demining, drilling and medical technologies.

An optimized full-configuration-interaction nuclear orbital approach to a ``hard-core'' interaction problem: Application to (3He)N-Cl2(B) clusters (N<=4)

NASA Astrophysics Data System (ADS)

de Lara-Castells, M. P.; Villarreal, P.; Delgado-Barrio, G.; Mitrushchenkov, A. O.

2009-11-01

An efficient full-configuration-interaction nuclear orbital treatment has been recently developed as a benchmark quantum-chemistry-like method to calculate ground and excited "solvent" energies and wave functions in small doped ΔEest clusters (N ≤4) [M. P. de Lara-Castells, G. Delgado-Barrio, P. Villarreal, and A. O. Mitrushchenkov, J. Chem. Phys. 125, 221101 (2006)]. Additional methodological and computational details of the implementation, which uses an iterative Jacobi-Davidson diagonalization algorithm to properly address the inherent "hard-core" He-He interaction problem, are described here. The convergence of total energies, average pair He-He interaction energies, and relevant one- and two-body properties upon increasing the angular part of the one-particle basis set (expanded in spherical harmonics) has been analyzed, considering Cl2 as the dopant and a semiempirical model (T-shaped) He-Cl2(B) potential. Converged results are used to analyze global energetic and structural aspects as well as the configuration makeup of the wave functions, associated with the ground and low-lying "solvent" excited states. Our study reveals that besides the fermionic nature of H3e atoms, key roles in determining total binding energies and wave-function structures are played by the strong repulsive core of the He-He potential as well as its very weak attractive region, the most stable arrangement somehow departing from the one of N He atoms equally spaced on equatorial "ring" around the dopant. The present results for N =4 fermions indicates the structural "pairing" of two H3e atoms at opposite sides on a broad "belt" around the dopant, executing a sort of asymmetric umbrella motion. This pairing is a compromise between maximizing the H3e-H3e and the He-dopant attractions, and suppressing at the same time the "hard-core" repulsion. Although the He-He attractive interaction is rather weak, its contribution to the total energy is found to scale as a power of three and it thus

The Physics of the Dense Z-Pinch in Theory and in Experiment With Application to Fusion Reactor

NASA Astrophysics Data System (ADS)

Haines, M. G.

1982-01-01

A new generation of Z-pinches employing high voltage, high current pulsed lines as power sources produce dense hot plasmas with enhanced stability properties. Three methods of Z-pinch formation are currently in use: (1) cylindrical collapse and compression of a pre-ionised gas; (2) laser initiation and Joule heating of a gas embedded pinch, and (3) hollow gas puff and subsequent collapse to the axis. The first method shows no dynamic bounce and no instability over about ten radial Alfvén transit times. The laser initiated Z-pinch shows benign helical structures, whilst the gas puff experiments are known for their high X-ray energy conversion associated with m = 0 instabilities. The first two experimental conditions are relevant for fusion. A calculation of energy balance for satisfying Lawson conditions with axial and radial energy losses and radiation loss shows that a current I of ~ 106 A and a line density N of 6 × 1018m-1 are required. This leads to two coincidences of physical quantities that are very favourable for controlled fusion. The first is that at this line density and under pressure balance the ratio of the ion Larmor radius to pinch radius is of order 1 so that a marked stabilisation of the configuration is expected. The second coincidence is that the current is only just below the Pease-Braginskii limit; this will permit the possibility of radiative collapse to attain the high density (~ 4 × 1027 m-3) and small radius (~ 20 μm) required for a compact (0.1 m long) discharge. The confining self-magnetic field is 104 T, the confinement time ~ 100 ns, and a matrix of pulsed discharges is envisaged in a moderator and breeding medium which does not have the wall-loading limitations of tokamaks.

Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas.

PubMed

Ross, M P; Shumlak, U

2016-10-01

The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 μs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 10 20 m -2 with spatial resolution near 10 μm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.

A short-pulse mode for the SPHINX LTD Z-pinch driver

NASA Astrophysics Data System (ADS)

D'Almeida, Thierry; Lassalle, Francis; Zucchini, Frederic; Loyen, Arnaud; Morell, Alain; Chuvatin, Alexander

2015-11-01

The SPHINX machine is a 6MA, 1 μs, LTD Z-pinch driver at CEA Gramat (France) and primarily used for studying radiation effects. Different power amplification concepts were examined in order to reduce the current rise time without modifying the generator discharge scheme, including the Dynamic Load Current Multiplier (DLCM) proposed by Chuvatin. A DLCM device, capable of shaping the current pulse without reducing the rise time, was developed at CEA. This device proved valuable for isentropic compression experiments in cylindrical geometry. Recently, we achieved a short pulse operation mode by inserting a vacuum closing switch between the DLCM and the load. The current rise time was reduced to ~300 ns. We explored the use of a reduced-height wire array for the Dynamic Flux Extruder in order to improve the wire array compression rate and increase the efficiency of the current transfer to the load. These developments are presented. Potential benefits of these developments for future Z pinch experiments are discussed.

Capillary Thinning and Pinch-off Dynamics and Printability of Polyelectrolyte Solutions

NASA Astrophysics Data System (ADS)

Sharma, Vivek; Jimenez, Leidy N.; Dinic, Jelena; Parsi, Nikila

Biological macromolecules like proteins, DNA and polysaccharides, and many industrial polymers, are classified together as polyelectrolytes for in solution, the repeat units in their backbone are decorated with disassociated, charge-bearing ionic groups, surrounded by counter-ions. In diverse applications like inkjet printing, sprayable cosmetics and insecticides, paints and coatings that involve formation of fluid columns or sheets that undergo progressive thinning and pinch-off into drops, the dominant flow within the necking filament is extensional in nature. The extensional rheology response of the charged macromolecular solutions is not as well understood as that of their uncharged counterparts. Here focus on the characterization of capillary thinning and pinch-off dynamics, extensional rheology and printability of two model systems: sodium (polystyrene sulfonate) and poly(acrylic acid) by using dripping-onto-substrate (DoS) rheometry technique. Both the measured extensional relaxation times and the extensional viscosity values show salt- and polymer concentration-dependent behavior that is not expected or anticipated from the typical shear rheology response.

Long implosion time (240 ns) Z-pinch experiments with a large diameter (12 cm) double-shell nozzle

NASA Astrophysics Data System (ADS)

Levine, J. S.; Banister, J. W.; Failor, B. H.; Qi, N.; Song, Y.; Sze, H. M.; Fisher, A.

2004-05-01

Recently, an 8 cm diameter double-shell nozzle has produced argon Z pinches with high K-shell yields with implosion time of 210 ns. To produce even longer implosion time Z pinches for facilities such as Decade Quad [D. Price, et al., "Electrical and Mechanical Design of the Decade Quad in PRS Mode," in Proceedings of the 12th IEEE Pulsed Power Conference, Monterey, CA, edited by C. Stallings and H. Kirbie (IEEE, New York, 1999), p. 489] (9 MA short circuit current at 300 ns), a larger nozzle (12 cm outer diameter) was designed and fabricated. During initial testing on Double-EAGLE [P. Sincerny et al., Proceedings of the 5th IEEE Pulsed Power Conference, Arlington, VA, edited by M. F. Rose and P. J. Turchi (IEEE, New York, 1985), p. 151], 9 kJ of argon K-shell radiation in a 6 ns full width at half maximum pulse was produced with a 240 ns implosion. The initial gas distributions produced by various nozzle configurations have been measured and their impact on the final radiative characteristics of the pinch are presented. The addition of a central jet to increase the initial gas density near the axis is observed to enhance the pinch quality, increasing K-shell yield by 17% and power by 40% in the best configuration tested.

Preliminary experimental results of tungsten wire-array Z-pinches on primary test stand

NASA Astrophysics Data System (ADS)

Huang, Xian-Bin; Zhou, Shao-Tong; Dan, Jia-Kun; Ren, Xiao-Dong; Wang, Kun-Lun; Zhang, Si-Qun; Li, Jing; Xu, Qiang; Cai, Hong-Chun; Duan, Shu-Chao; Ouyang, Kai; Chen, Guang-Hua; Ji, Ce; Wei, Bing; Feng, Shu-Ping; Wang, Meng; Xie, Wei-Ping; Deng, Jian-Jun; Zhou, Xiu-Wen; Yang, Yi

2015-07-01

The Primary Test Stand (PTS) developed at the China Academy of Engineering Physics is a 20 TW pulsed power driver, which can deliver a ˜10 MA, 70 ns rise-time (10%-90%) current to a short-circuit load and has important applications in Z-pinch driven inertial confinement fusion and high energy density physics. Preliminary results of tungsten wire-array Z-pinch experiments on PTS are presented. The load geometries investigated include 15-mm-tall cylindrical single and nested arrays with diameter ranging from 13 mm to 30 mm, consisting of 132-300 tungsten wires with 5-10 μm in diameter. Multiple diagnostics were fielded to characterize the x-ray radiation from wire-array Z pinches. The x-ray peak power (˜50 TW) and total radiated energy (˜500 kJ) were obtained from a single 20-mm-diam array with 80-ns stagnation time. The highest x-ray peak power up to 80 TW with 2.4 ns FWHM was achieved by using a nested array with 20-mm outer diameter, and the total x-ray energy from the nested array is comparable to that of single array. Implosion velocity estimated from the time-resolved image measurement exceeds 30 cm/μs. The detailed experimental results and other findings are presented and discussed.

The Pitt Innovation Challenge (PInCh): Driving Innovation in Translational Research Through an Incentive-Based, Problem-Focused Competition

PubMed Central

Fitzpatrick, Nicole Edgar; Maier, John; Yasko, Laurel; Mathias, David; Qua, Kacy; Wagner, Erika; Miller, Elizabeth; Reis, Steven E.

2017-01-01

Problem Translational research aims to move scientific discoveries across the biomedical spectrum from the laboratory to humans, and to ultimately transform clinical practice and public health policies. Despite efforts to accelerate translational research through national initiatives, several major hurdles remain. Approach The authors created the Pitt Innovation Challenge (PInCh) as an incentive-based, problem-focused approach to solving identified clinical or public health problems at the University of Pittsburgh Clinical and Translational Science Institute in spring 2014. With input from a broad range of stakeholders, PInCh leadership arrived at the challenge question: How do we empower individuals to take control of their own health outcomes? The authors developed the PInCh’s three-round proposal submission and review process as well as an online contest management tool to support the process. Outcomes Ninety-two teams submitted videos proposals in round one. Proposals included mobile applications (29, 32%), other information technology (19, 21%), and community program (22, 24%) solutions. Ten teams advanced to the final round, where three were awarded $100,000 to implement their solution over twelve months. In a six-month follow-up survey, 6/11 (55%) team leaders stated the PInCh helped to facilitate connections outside their normal sphere of collaborators. Next Steps Additional educational training sessions related to problem-focused research will be developed. The PInCh will be expanded to engage investment and industry communities to facilitate the translation of solutions to clinical practice via commercialization pathways. External organizations and other universities will be engaged to use the PInCh as a mechanism to fuel innovation in their spaces. PMID:27508341

Estimations of Mo X-pinch plasma parameters on QiangGuang-1 facility by L-shell spectral analyses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Jian; Qiu, Aici; State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024

2013-08-15

Plasma parameters of molybdenum (Mo) X-pinches on the 1-MA QiangGuang-1 facility were estimated by L-shell spectral analysis. X-ray radiation from X-pinches had a pulsed width of 1 ns, and its spectra in 2–3 keV were measured with a time-integrated X-ray spectrometer. Relative intensities of spectral features were derived by correcting for the spectral sensitivity of the spectrometer. With an open source, atomic code FAC (flexible atomic code), ion structures, and various atomic radiative-collisional rates for O-, F-, Ne-, Na-, Mg-, and Al-like ionization stages were calculated, and synthetic spectra were constructed at given plasma parameters. By fitting the measured spectramore » with the modeled, Mo X-pinch plasmas on the QiangGuang-1 facility had an electron density of about 10{sup 21} cm{sup −3} and the electron temperature of about 1.2 keV.« less

A conservative MHD scheme on unstructured Lagrangian grids for Z-pinch hydrodynamic simulations

NASA Astrophysics Data System (ADS)

Wu, Fuyuan; Ramis, Rafael; Li, Zhenghong

2018-03-01

A new algorithm to model resistive magnetohydrodynamics (MHD) in Z-pinches has been developed. Two-dimensional axisymmetric geometry with azimuthal magnetic field Bθ is considered. Discretization is carried out using unstructured meshes made up of arbitrarily connected polygons. The algorithm is fully conservative for mass, momentum, and energy. Matter energy and magnetic energy are managed separately. The diffusion of magnetic field is solved using a derivative of the Symmetric-Semi-Implicit scheme, Livne et al. (1985) [23], where unconditional stability is obtained without needing to solve large sparse systems of equations. This MHD package has been integrated into the radiation-hydrodynamics code MULTI-2D, Ramis et al. (2009) [20], that includes hydrodynamics, laser energy deposition, heat conduction, and radiation transport. This setup allows to simulate Z-pinch configurations relevant for Inertial Confinement Fusion.

Modulation of thermal conductivity in kinked silicon nanowires: phonon interchanging and pinching effects.

PubMed

Jiang, Jin-Wu; Yang, Nuo; Wang, Bing-Shen; Rabczuk, Timon

2013-04-10

We perform molecular dynamics simulations to investigate the reduction of the thermal conductivity by kinks in silicon nanowires. The reduction percentage can be as high as 70% at room temperature. The temperature dependence of the reduction is also calculated. By calculating phonon polarization vectors, two mechanisms are found to be responsible for the reduced thermal conductivity: (1) the interchanging effect between the longitudinal and transverse phonon modes and (2) the pinching effect, that is, a new type of localization, for the twisting and transverse phonon modes in the kinked silicon nanowires. Our work demonstrates that the phonon interchanging and pinching effects, induced by kinking, are brand-new and effective ways in modulating heat transfer in nanowires, which enables the kinked silicon nanowires to be a promising candidate for thermoelectric materials.

Radiation characteristics and implosion dynamics of tungsten wire array Z-pinches on the YANG accelerator

NASA Astrophysics Data System (ADS)

Huang, Xian-Bin; Yang, Li-Bing; Li, Jing; Zhou, Shao-Tong; Ren, Xiao-Dong; Zhang, Si-Qun; Dan, Jia-Kun; Cai, Hong-Chun; Duan, Shu-Chao; Chen, Guang-Hua; Zhang, Zheng-Wei; Ouyang, Kai; Li, Jun; Zhang, Zhao-Hui; Zhou, Rong-Guo; Wang, Gui-Lin

2012-05-01

We investigated the radiation characteristics and implosion dynamics of low-wire-number cylindrical tungsten wire array Z-pinches on the YANG accelerator with a peak current 0.8-1.1 MA and a rising time ~ 90 ns. The arrays are made up of (8-32) × 5 μm wires 6/10 mm in diameter and 15 mm in height. The highest X-ray power obtained in the experiments was about 0.37 TW with the total radiation energy ~ 13 kJ and the energy conversion efficiency ~ 9% (24 × 5 μm wires, 6 mm in diameter). Most of the X-ray emissions from tungsten Z-pinch plasmas were distributed in the spectral band of 100-600 eV, peaked at 250 and 375 eV. The dominant wavelengths of the wire ablation and the magneto-Rayleigh—Taylor instability were found and analyzed through measuring the time-gated self-emission and laser interferometric images. Through analyzing the implosion trajectories obtained by an optical streak camera, the run-in velocities of the Z-pinch plasmas at the end of the implosion phase were determined to be about (1.3-2.1) × 107 cm/s.

Double salt décollements: Effect of pinch-out overlapping in experimental thrust wedges

NASA Astrophysics Data System (ADS)

Santolaria, P.; Vendeville, B.; Graveleau, F.; Casas, A.; Soto, R.

2013-12-01

The presence of one or more evaporitic horizons acting as detachment levels in fold-and-thrust belts is common. Numerous works have dealt with the analysis of the role played by basal detachments on the deformation style of fold-and-thrust belts, but less attention has been paid to the interaction between two décollements and strain transfer between them. In this study, 10 sand-silicone analogue experiments with two detachment levels and different stratigraphic pinch-out configurations were carried out: the basal décollement was located hinterlandwards, and the upper one was located forelandwards, with or without geographic underlap or overlap. These geometrical arrangements simulate evaporites deposited in foreland basins progressively involved in shortening. To analyze their influence on the geometry and kinematics of thrust wedges, we tested successively the following parameters: i) the amount of vertical overlapping between the two décollement pinch-outs, ii) the total amount of shortening, and iii) the geometry of the intermediate décollement (pinch-out line parallel or oblique with respect to the pinch-out line of the basal décollement). All experiments were quantitatively monitored by carrying DEM (Digital Elevation Models) and PIV (Particle Image Velocimetry) measurements. All models had a similar style: (i) an inner domain, characterized by a thicker sand cover, with three forward verging thrusts rooted in the basal décollement, (ii) an outer domain with thinner sand cover, whose deformation pattern was characterized by 2 to 6 structures detaching on the upper décollement and (iii) a 'step zone' located between the inner and outer domains having varying geometry and kinematics. In longer-lived models, structures were reworked and salt migration deformed the early emplaced folds and thrusts. Our experimental results point out that the amount of vertical overlapping between the two décollement pinch outs is a first order parameter that conditions not

Numerical characterization of plasma breakdown in reversed field pinches

NASA Astrophysics Data System (ADS)

Peng, Yanli; Zhang, Ya; Mao, Wenzhe; Yang, Zhoujun; Hu, Xiwei; Jiang, Wei

2018-02-01

In the reversed field pinch, there is considerable interest in investigating the plasma breakdown. Indeed, the plasma formed during the breakdown may have an influence on the confinement and maintenance in the latter process. However, up to now there has been no related work, experimentally or in simulation, regarding plasma breakdown in reversed field pinch (RFP). In order to figure out the physical mechanism behind plasma breakdown, the effects of the toroidal and error magnetic field, as well as the loop voltage have been studied. We find that the error magnetic field cannot be neglected even though it is quite small in the short plasma breakdown phase. As the toroidal magnetic field increases, the averaged electron energy is reduced after plasma breakdown is complete, which is disadvantageous for the latter process. In addition, unlike the voltage limits in the tokamak, loop voltages can be quite high because there are no requirements for superconductivity. Volt-second consumption has a small difference under different loop voltages. The breakdown delay still exists in various loop voltage cases, but it is much shorter compared to that in the tokamak case. In all, successful breakdowns are possible in the RFP under a fairly broad range of parameters.

Radial distribution function for hard spheres in fractal dimensions: A heuristic approximation.

PubMed

Santos, Andrés; de Haro, Mariano López

2016-06-01

Analytic approximations for the radial distribution function, the structure factor, and the equation of state of hard-core fluids in fractal dimension d (1≤d≤3) are developed as heuristic interpolations from the knowledge of the exact and Percus-Yevick results for the hard-rod and hard-sphere fluids, respectively. In order to assess their value, such approximate results are compared with those of recent Monte Carlo simulations and numerical solutions of the Percus-Yevick equation for a fractal dimension [M. Heinen et al., Phys. Rev. Lett. 115, 097801 (2015)PRLTAO0031-900710.1103/PhysRevLett.115.097801], a good agreement being observed.

A z-pinch photo-pumped pulsed atomic iodine laser

NASA Astrophysics Data System (ADS)

Stone, D. H.; Saunders, D. P.; Clark, M. C.

1984-03-01

A pulsed atomic iodine laser (CF3I) was designed and constructed using a coaxial xenon flash lamp as a pump source. The flash lamp was operated at low pressure to obtain pulse compression via xenon self-pinch. Electrical and optical diagnostics were performed for various xenon and CF3I pressures. Calorimeter data and burn patterns were obtained for the laser. Time-resolved spectroscopic data were taken throughout the CF3I pump band.

High-Power Pinched-Beam Diode Development for Radiographic Applications

DTIC Science & Technology

2007-06-01

reentrant rods. II. X-RAY DIAGNOSTICS The x-ray dose is measured using CaF2 thermoluminescent dosimeters ( TLDs ) enclosed in 1-cm- diam...1.5-mm spot size. This paper reports on studies of the rod-pinch (RP) diode [3], comprising a small anode rod and an annular cathode. Electrons ...because the electrons impact the rod primarily in the backwards direction. As the voltage increases, the x- radiation becomes more forward-peaked

Evaluation of the Rod-Pinch Diode as a High-Resolution Source for Flashradiography at 2 to 4 MV

DTIC Science & Technology

2001-06-01

Research Laboratory, Washington, DC 20375 Abstract The ASTERIX generator is used to obtain the first evaluation of the rod-pinch electron -beam diode... dosimeters on a few shots are consistent with the RPL doses. Doses are measured at 36 cm from the tungsten tip, and inverse- square scaling is used to...Arrangement of the rod-pinch diode on ASTERIX. Radiation diagnostics include RPLs and TLDs for dose, tungsten rolled-edge and film for source size, and

Enhanced Densification and Hardness of Titanium Bodies Sintered by Advanced Hydrogen Sintering Process

NASA Astrophysics Data System (ADS)

Oh, Jung-Min; Koo, Ja-Geon; Lim, Jae-Won

2018-05-01

A new sintering technique for enhancing a densification and hardness of sintered titanium body by supplying hydrogen was developed (Hydrogen Sintering Process, HSP). The HSP was developed by only injecting hydrogen into an argon atmosphere during the core time. As a result, sound titanium sintered bodies with high density and hardness were obtained by the HSP. In addition, a pore size and number of the HSP specimens were smaller than those of the argon atmosphere specimen. It was found that the injecting hydrogen into the argon atmosphere by HSP can prevent the formation of oxide layers, resulting in enhanced densification and hardness.

Primary experimental results of wire-array Z-pinches on PTS

NASA Astrophysics Data System (ADS)

Huang, X. B.; Zhou, S. T.; Ren, X. D.; Dan, J. K.; Wang, K. L.; Zhang, S. Q.; Li, J.; Xu, Q.; Cai, H. C.; Duan, S. C.; Ouyang, K.; Chen, G. H.; Ji, C.; Wang, M.; Feng, S. P.; Yang, L. B.; Xie, W. P.; Deng, J. J.

2014-12-01

The Primary Test Stand (PTS) developed at the China Academy of Engineering Physics is a multiterawatt pulsed power driver, which can deliver a ˜10 MA, 70 ns rise-time (10%-90%) current to a short circuit load and has important applications in Z-pinch driven inertial confinement fusion and high energy density physics. In this paper, primary results of tungsten wire-array Z-pinch experiments on PTS are presented. The load geometries investigated include 15-mm-tall cylindrical single and nested arrays with diameter ranging from 14.4-26.4 mm, and consisting of 132˜276 tungsten wires with 5˜10 μm in diameter. Multiple diagnostics were fielded to determine the characteristics of x-ray radiations and to obtain self-emitting images of imploding plasmas. X-ray power up to 80 TW with ˜3 ns FWMH is achieved by using nested wire arrays. The total x-ray energy exceeds 500 kJ and the peak radiation temperature is about 150 eV. Typical velocity of imploding plasmas goes around 3˜5×107 cm/s and the radial convergence ratio is between 10 and 20.

Fully kinetic simulations of dense plasma focus Z-pinch devices.

PubMed

Schmidt, A; Tang, V; Welch, D

2012-11-16

Dense plasma focus Z-pinch devices are sources of copious high energy electrons and ions, x rays, and neutrons. The mechanisms through which these physically simple devices generate such high-energy beams in a relatively short distance are not fully understood. We now have, for the first time, demonstrated a capability to model these plasmas fully kinetically, allowing us to simulate the pinch process at the particle scale. We present here the results of the initial kinetic simulations, which reproduce experimental neutron yields (~10(7)) and high-energy (MeV) beams for the first time. We compare our fluid, hybrid (kinetic ions and fluid electrons), and fully kinetic simulations. Fluid simulations predict no neutrons and do not allow for nonthermal ions, while hybrid simulations underpredict neutron yield by ~100x and exhibit an ion tail that does not exceed 200 keV. Only fully kinetic simulations predict MeV-energy ions and experimental neutron yields. A frequency analysis in a fully kinetic simulation shows plasma fluctuations near the lower hybrid frequency, possibly implicating lower hybrid drift instability as a contributor to anomalous resistivity in the plasma.

Hard Core Pharmacology: How Much Is Taught in Pharmacy Schools?

ERIC Educational Resources Information Center

Bachmann, Kenneth A.; And Others

1990-01-01

A survey was sent to eighty-five American Association of Colleges of Pharmacy-member schools and affiliates to learn how many lectures are accorded to core sequences in pharmacology. The data were intended to provide a frame of reference for the University of Toledo College of Pharmacy. (Author/MLW)

The effectiveness of orthoses in the conservative management of thumb CMC joint osteoarthritis: An analysis of functional pinch strength.

PubMed

Grenier, Marie-Lyne; Mendonca, Rochelle; Dalley, Peter

2016-01-01

The study was a retrospective cohort analysis for a 19-month period from May 2013 to December 2014. Although the use of orthoses has long been a staple of conservative treatment measures for individuals with osteoarthritis of the thumb carpometacarpal (CMC) joint, there remains little evidence exploring its effectiveness in improving functional outcomes for this client population. The purpose of this study was to assess the effectiveness of 3 frequently used orthoses in improving the functional pinch strength of adults with a diagnosis of thumb CMC joint osteoarthritis. A retrospective cohort analysis was conducted to determine whether pinch strength improved after orthotic fabrication, and fitting in patients referred to a hand therapy clinic. Patients who received a Colditz design orthosis had a mean increase of 2.64 lb with regard to functional pinch strength after orthotic fabrication and fitting. Patients who received a Comfort Cool orthosis (North Coast Medical, Morgan Hill, CA) had a mean increase of 2.47 lb, whereas patients who received a Thumb Spica orthosis had a mean increase of 3.25 lb. There was no evidence of any statistically significant difference in the average improvements in pinch strength between the Colditz design orthosis and the Comfort Cool orthosis. Results from this study demonstrate that orthosis wear consistently increases the functional pinch strength of individuals with thumb CMC joint osteoarthritis. Large-scale multisite research studies comparing various orthotic designs are necessary to help therapists determine best practice interventions for the conservative management of thumb CMC joint osteoarthritis. 2(c). Copyright © 2016 Hanley & Belfus. Published by Elsevier Inc. All rights reserved.

["The hard core". Science between politics and philosophy by Carl Friedrich von Weizsäcker and in the finalization theory].

PubMed

Krohn, Wolfgang

2014-01-01

In the Starnberg Max-Planck Institute one of the working groups was concerned with science as the formative condition--or "hard core"--of societal modernity, and with science as potential resource for solving social problems and addressing future goals. More precisely, the group intended to differentiate between phases in which scientific disciplines predominantly care for their own paradigmatic completion and those allowing their theoretical potential resonate with external needs. The conceptual model was coined "finalization in science". It soon provoked a heated controversy on the dangers of social control of science. The paper analyses Carl Friedrich von Weizsäcker's views on the relation between philosophy and policy of science including his interpretation of Thomas Kuhn and reconstructs the impact of his ideas on the finalization model. It finally reflects on the relationship between science development and change of consciousness in the context of scientific responsibility for (the use of) research outcomes.

Étude spectrale d'un micro-plasma d'implosion X-pinch

NASA Astrophysics Data System (ADS)

Aranchuk, L. E.

2006-12-01

Le pincement magnétique de type X-pinch permet de réaliser un micro-plasma chaud et dense bien positionné dans l'espace qui présente une applicabilité pour la radiographie X d'objets peu denses de petite taille. Une batterie de diagnostics ayant tous une résolution spectrale a été installée autour d'un X-pinch alimenté par un banc de condensateurs rapide. Les résultats présentés portent sur la taille de la source intégrée en temps, sur la durée d'impulsion et sur le spectre d'émission X. Des exemples de radiographie confortent la détermination de la taille. Des spectres à haute résolution spectrale intégrés en temps (1 à 3 keV) montrent que les ions multichargés présents dans le plasma (Al hydrogénoïde et héliumoïde, Cu et Mo néonoïdes) sont les mêmes que dans les X-pinches alimentés par des générateurs pulsés bien plus puissants. Une spectroscopie large bande à haute résolution temporelle, basée sur des détecteurs innovants, a permis de mettre en évidence une émission dure sub-nanoseconde et de chiffrer la puissance spectrale instantanée et l'énergie X émise entre 20eV et 8keV. La puissance maximale peut dépasser 1GW pendant 0,4-0,7ns. La source émet 10 à 30J pendant 100-150ns en dessous de 400eV.

An RXTE Study of M87 and the Core of the Virgo Cluster

NASA Technical Reports Server (NTRS)

Reynolds, Christopher S.; Heinz, Sebastian; Fabian, Andrew C.; Begelman, Mitchell C.

1998-01-01

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray Timing Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC 4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum indicative of kT approx. = 2.5 keV plasma with approximately 25% cosmic abundances. No non-thermal (power-law) emission from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic X-ray Background being the limiting factor. Combining with ROSAT data, we infer that the X-ray spectrum of the M87 core and jet must be steep (Gamma(sub core) greater than 1.90 and Gamma(sub jet) greater than 1.75), and we discuss the implications of this result. In particular, these results are consistent with M87 being a mis-aligned BL-Lac object.

An RXTE Study of M87 and the Core of the Virgo Cluster

NASA Technical Reports Server (NTRS)

Reynolds, Christopher S.; Heinz, Sebastian; Fabian, Andrew C.; Begelman, Mitchell C.

1998-01-01

We present hard X-ray observations of the nearby radio galaxy M87 and the core of the Virgo cluster using the Rossi X-ray 7Tming Explorer. These are the first hard X-ray observations of M87 not affected by contamination from the nearby Seyfert 2 galaxy NGC 4388. Thermal emission from Virgo's intracluster medium is clearly detected and has a spectrum indicative of kT is approximately equal to 2.5 keV plasma with approximately 25% cosmic abundances. No non-thermal (power-law) emission from M87 is detected in the hard X-ray band, with fluctuations in the Cosmic X-ray Background being the limiting factor. Combining with ROSAT data, we infer that the X-ray spectrum of the M87 core and jet must be steep (Gamma (sub core) > 1.90 and Gamma (sub jet) > 1.75), and we discuss the implications of this result. In particular, these results are consistent with M87 being a mis-aligned BL-Lac object.

Mongoose: Creation of a Rad-Hard MIPS R3000

NASA Technical Reports Server (NTRS)

Lincoln, Dan; Smith, Brian

1993-01-01

This paper describes the development of a 32 Bit, full MIPS R3000 code-compatible Rad-Hard CPU, code named Mongoose. Mongoose progressed from contract award, through the design cycle, to operational silicon in 12 months to meet a space mission for NASA. The goal was the creation of a fully static device capable of operation to the maximum Mil-883 derated speed, worst-case post-rad exposure with full operational integrity. This included consideration of features for functional enhancements relating to mission compatibility and removal of commercial practices not supported by Rad-Hard technology. 'Mongoose' developed from an evolution of LSI Logic's MIPS-I embedded processor, LR33000, code named Cobra, to its Rad-Hard 'equivalent', Mongoose. The term 'equivalent' is used to infer that the core of the processor is functionally identical, allowing the same use and optimizations of the MIPS-I Instruction Set software tool suite for compilation, software program trace, etc. This activity was started in September of 1991 under a contract from NASA-Goddard Space Flight Center (GSFC)-Flight Data Systems. The approach affected a teaming of NASA-GSFC for program development, LSI Logic for system and ASIC design coupled with the Rad-Hard process technology, and Harris (GASD) for Rad-Hard microprocessor design expertise. The program culminated with the generation of Rad-Hard Mongoose prototypes one year later.

High brightness electrodeless Z-Pinch EUV source for mask inspection tools

NASA Astrophysics Data System (ADS)

Horne, Stephen F.; Partlow, Matthew J.; Gustafson, Deborah S.; Besen, Matthew M.; Smith, Donald K.; Blackborow, Paul A.

2012-03-01

Energetiq Technology has been shipping the EQ-10 Electrodeless Z-pinchTM light source since 1995. The source is currently being used for metrology, mask inspection, and resist development. Energetiq's higher brightness source has been selected as the source for pre-production actinic mask inspection tools. This improved source enables the mask inspection tool suppliers to build prototype tools with capabilities of defect detection and review down to 16nm design rules. In this presentation we will present new source technology being developed at Energetiq to address the critical source brightness issue. The new technology will be shown to be capable of delivering brightness levels sufficient to meet the HVM requirements of AIMS and ABI and potentially API tools. The basis of the source technology is to use the stable pinch of the electrodeless light source and have a brightness of up to 100W/mm(carat)2-sr. We will explain the source design concepts, discuss the expected performance and present the modeling results for the new design.

Shot-by-shot Spectrum Model for Rod-pinch, Pulsed Radiography Machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wood, William Monford

A simplified model of bremsstrahlung production is developed for determining the x-ray spectrum output of a rod-pinch radiography machine, on a shot-by-shot basis, using the measured voltage, V(t), and current, I(t). The motivation for this model is the need for an agile means of providing shot-by-shot spectrum prediction, from a laptop or desktop computer, for quantitative radiographic analysis. Simplifying assumptions are discussed, and the model is applied to the Cygnus rod-pinch machine. Output is compared to wedge transmission data for a series of radiographs from shots with identical target objects. Resulting model enables variation of parameters in real time, thusmore » allowing for rapid optimization of the model across many shots. “Goodness of fit” is compared with output from LSP Particle-In-Cell code, as well as the Monte Carlo Neutron Propagation with Xrays (“MCNPX”) model codes, and is shown to provide an excellent predictive representation of the spectral output of the Cygnus machine. In conclusion, improvements to the model, specifically for application to other geometries, are discussed.« less

Shot-by-shot Spectrum Model for Rod-pinch, Pulsed Radiography Machines

DOE PAGES

Wood, William Monford

2018-02-07

A simplified model of bremsstrahlung production is developed for determining the x-ray spectrum output of a rod-pinch radiography machine, on a shot-by-shot basis, using the measured voltage, V(t), and current, I(t). The motivation for this model is the need for an agile means of providing shot-by-shot spectrum prediction, from a laptop or desktop computer, for quantitative radiographic analysis. Simplifying assumptions are discussed, and the model is applied to the Cygnus rod-pinch machine. Output is compared to wedge transmission data for a series of radiographs from shots with identical target objects. Resulting model enables variation of parameters in real time, thusmore » allowing for rapid optimization of the model across many shots. “Goodness of fit” is compared with output from LSP Particle-In-Cell code, as well as the Monte Carlo Neutron Propagation with Xrays (“MCNPX”) model codes, and is shown to provide an excellent predictive representation of the spectral output of the Cygnus machine. In conclusion, improvements to the model, specifically for application to other geometries, are discussed.« less

Shot-by-shot spectrum model for rod-pinch, pulsed radiography machines

NASA Astrophysics Data System (ADS)

Wood, Wm M.

2018-02-01

A simplified model of bremsstrahlung production is developed for determining the x-ray spectrum output of a rod-pinch radiography machine, on a shot-by-shot basis, using the measured voltage, V(t), and current, I(t). The motivation for this model is the need for an agile means of providing shot-by-shot spectrum prediction, from a laptop or desktop computer, for quantitative radiographic analysis. Simplifying assumptions are discussed, and the model is applied to the Cygnus rod-pinch machine. Output is compared to wedge transmission data for a series of radiographs from shots with identical target objects. Resulting model enables variation of parameters in real time, thus allowing for rapid optimization of the model across many shots. "Goodness of fit" is compared with output from LSP Particle-In-Cell code, as well as the Monte Carlo Neutron Propagation with Xrays ("MCNPX") model codes, and is shown to provide an excellent predictive representation of the spectral output of the Cygnus machine. Improvements to the model, specifically for application to other geometries, are discussed.

Optical Pumping of High Power Lasers with an Array of Plasma Pinches.

DTIC Science & Technology

1986-04-01

Two dense plasma focus systems, the hypocycloidal pinch and the Mather type were investigated as the potential excitation light sources for high...was also performed for the first time using the Mather type dense plasma focus (MDPF) sucsessfully. Results thus fare indicate that both HCP and MDPF

The impact of plasma dynamics on the self-magnetic-pinch diode impedance

DOE PAGES

Bennett, Nichelle; Crain, M. Dale; Droemer, Darryl W.; ...

2015-03-20

In this study, the self-magnetic-pinch diode is being developed as an intense electron beam source for pulsed-power-driven x-ray radiography. The basic operation of this diode has long been understood in the context of pinched diodes, including the dynamic effect that the diode impedance decreases during the pulse due to electrode plasma formation and expansion. Experiments being conducted at Sandia National Laboratories' RITS-6 accelerator are helping to characterize these plasmas using time-resolved and time-integrated camera systems in the x-ray and visible. These diagnostics are analyzed in conjunction with particle-in-cell simulations of anode plasma formation and evolution. The results confirm the long-standingmore » theory of critical-current operation with the addition of a time-dependent anode-cathode gap length. Finally, the results may suggest that anomalous impedance collapse is driven by increased plasma radial drift, leading to larger-than-average ion v r × B θ acceleration into the gap.« less

THE STABILITY OF THE PINCH WITH ANISOTROPIC PRESSURE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jaggi, R.K.

1961-12-01

A dispersion equation was obtained for the stability of the pinch from the hydromagnetic equations supplemented by an equation for the pressure tensor of the ions. The dispersion equation was obtained for the marginal instability case only. It was observed that this dispersion equation coincides with the dispersion equation obtained from the Chew, Goldberger, and Low equations for the marginal instability case. It was concluded that the region of stability predicted from the equations that were used is slightly more than given by the kinetic equation used by Chandrasekhar, Kaufmann, and Watson. (auth)

A Critical Fast Ion Beta in the Madison Symmetric Torus Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Capecchi, William J.

The first fast-ion profile measurements have been made in a reversed-field pinch (RFP) plasma. A large population of fast-ions are deposited in the core of the Madison Symmetric Torus (MST) through use of a 1 MW neutral beam injector (NBI) giving rise to a variety of beam-driven instabilities. One such mode, the energetic-particle mode (EPM) has been shown to reduce fast-ion content in MST, evident through drops in signal levels of the advanced neutral particle analyzer (ANPA). EPMs in MST appear as bursts of magnetic fluctuations at a lab frequency of ˜100 kHz reaching peak amplitude and decaying away within 100 microseconds. A burst ensemble of the neutron data does not reveal a drop in neutron emission across a burst, implying the population of fast-ions transported by a burst constitute a small fraction of the total. The burst may also pitch-angle scatter out of the ANPA phase space or be transported to mid-radius where charge-exchange with the background neutrals or fast-ion orbit stochasticity may reduce fast-ion confinement. Data gathered from the expanded neutron diagnostic suite including a new collimated neutron detector (CiNDe) was used to reconstruct the fast-ion profile in MST and measure critical fast-ion beta quantities. Measurements were made in plasma conditions with varying magnetic field strength in order to investigate the interplay between the energetic particle (EP) drive and Alfven continuum damping. The measured values of the core fast-ion beta (7.5% (1.2%) in 300 (500) kA plasmas) are reduced from classical predictions (TRANSP predicts up to 10% core value) due to EPM activity. The frequency, magnitude, and rate of occurrence of the bursts depends on the tearing mode amplitude, Alfven continuum damping rate, fast-ion profile shape, and resonant orbit dynamics. Marginal stability was reached in both moderate- (300 kA) and high- (500 kA) current discharges, marked by sustained EPM activity and a saturated global neutron signal during NBI

Hardness characteristic of dental porcelain synthesized from Indonesian natural sand

NASA Astrophysics Data System (ADS)

Gunawan, J.; Taufik, D.; Takarini, V.; Hasratiningsih, Z.; Ramelan, A.

2018-02-01

Porcelain has been one of dental biomaterials which can be used to restore tooth structure. Veneer and jacket crown were the examples of dental porcelain restoration. Since wear resistance is related to the strength on its surface, then Vickers Hardness Test of the synthesized porcelain was applied subsequently. If the porcelain hardness number is too high, it should be considered that an abrasion of the opposing teeth could occur. On previous research, dental porcelain had been successfully synthesized from Indonesian natural sand. In this experiment, 5 samples were prepared from a mixture of 65w/o Pangaribuan feldspar, 25w/o Belitung silica, 5w/o Sukabumi kaolinite, and 5w/o potassium salt. This synthesized porcelain samples were invested on 5 cm diameter resin each. A kilogram of load was placed on top of each sample for 10 seconds on 7 different indented areas using ZwickRoell Indentec ZHVμ Micro Vickers. The average hardness number of synthesized dental porcelain made from Indonesian natural sand was 936.06 VHN which was higher than the average hardness number of porcelain restoration. In conclusion of the hardness test, synthesized dental porcelain made from Indonesian natural sand can potentially be used as a core, which shall support hardness and strength of the crown restoration.

Dynamics of current sheath in a hollow electrode Z-pinch discharge using slug model

NASA Astrophysics Data System (ADS)

Abd Al-Halim, Mohamed A.; Afify, M. S.

2017-03-01

The hollow electrode Z-pinch (HEZP) experiment is a new construction for the electromagnetic propulsion application in which the plasma is formed by the discharge between a plate and ring electrodes through which the plasma is propelled. The experimental results for 8 kV charging voltage shows that the peak discharge current is about 109 kA, which is in good agreement with the value obtained from the simulation in the slug model that simulates the sheath dynamics in the HEZP. The fitting of the discharge current from the slug model indicates that the total system inductance is 238 nH which is relatively a high static inductance accompanied with a deeper pinch depth indicating that the fitted anomalous resistance would be about 95 mΩ. The current and mass factors vary with the changing the gas pressure and the charging voltage. The current factor is between 0.4 and 0.5 on average which is relatively low value. The mass factor decreases by increasing the gas pressure indicating that the sheath is heavy to be driven by the magnetic pressure, which is also indicated from the decreases of the drive factor, hence the radial sheath velocity decreases. The plasma inductance and temperature increase with the increase of the drive factor while the minimum pinch radius decreases.

Experimental study of surface insulated-standard hybrid tungsten planar wire array Z-pinches at "QiangGuang-I" facility

NASA Astrophysics Data System (ADS)

Sheng, Liang; Peng, Bodong; Li, Yang; Yuan, Yuan; Li, Mo; Zhang, Mei; Zhao, Chen; Zhao, Jizhen; Wang, Liangping

2016-01-01

The experimental results of the insulated-standard hybrid wire array Z pinches carried out on "QiangGuang-I" facility at Northwest Institute of Nuclear Technology were presented and discussed. The surface insulating can impose a significant influence on the dynamics and radiation characteristics of the hybrid wire array Z pinches, especially on the early stage (t/timp < 0.6). The expansion of insulated wires at the ablation stage is suppressed, while the streams stripped from the insulated wires move faster than that from the standard wires. The foot radiation of X-ray is enhanced by increment of the number of insulated wires, 19.6 GW, 33.6 GW, and 68.6 GW for shots 14037S, 14028H, and 14039I, respectively. The surface insulation also introduces nonhomogeneity along the single wire—the streams move much faster near the electrodes. The colliding boundary of the hybrid wire array Z pinches is bias to the insulated side approximately 0.6 mm.

Scoring Dawg Core Breakoff and Retention Mechanism

NASA Technical Reports Server (NTRS)

Badescu, Mircea; Sherrit, Stewart; Bar-Cohen, Yoseph; Bao, Xiaoqi; Backes, Paul G.

2011-01-01

This novel core break-off and retention mechanism consists of a scoring dawg controlled by a set of two tubes (a drill tube and an inner tube). The drill tube and the inner tube have longitudinal concentric holes. The solution can be implemented in an eccentric tube configuration as well where the tubes have eccentric longitudinal holes. The inner tube presents at the bottom two control surfaces for controlling the orientation of the scoring dawg. The drill tube presents a sunk-in profile on the inside of the wall for housing the scoring dawg. The inner tube rotation relative to the drill tube actively controls the orientation of the scoring dawg and hence its penetration and retrieval from the core. The scoring dawg presents a shaft, two axially spaced arms, and a tooth. The two arms slide on the control surfaces of the inner tube. The tooth, when rotated, can penetrate or be extracted from the core. During drilling, the two tubes move together maintaining the scoring dawg completely outside the core. After the desired drilling depth has been reached the inner tube is rotated relative to the drill tube such that the tooth of the scoring dawg moves toward the central axis. By rotating the drill tube, the scoring dawg can score the core and so reduce its cross sectional area. The scoring dawg can also act as a stress concentrator for breaking the core in torsion or tension. After breaking the core, the scoring dawg can act as a core retention mechanism. For scoring, it requires the core to be attached to the rock. If the core is broken, the dawg can be used as a retention mechanism. The scoring dawg requires a hard-tip insert like tungsten carbide for scoring hard rocks. The relative rotation of the two tubes can be controlled manually or by an additional actuator. In the implemented design solution the bit rotation for scoring was in the same direction as the drilling. The device was tested for limestone cores and basalt cores. The torque required for breaking the

Multiple Core Galaxies

NASA Technical Reports Server (NTRS)

Miller, R.H.; Morrison, David (Technical Monitor)

1994-01-01

Nuclei of galaxies often show complicated density structures and perplexing kinematic signatures. In the past we have reported numerical experiments indicating a natural tendency for galaxies to show nuclei offset with respect to nearby isophotes and for the nucleus to have a radial velocity different from the galaxy's systemic velocity. Other experiments show normal mode oscillations in galaxies with large amplitudes. These oscillations do not damp appreciably over a Hubble time. The common thread running through all these is that galaxies often show evidence of ringing, bouncing, or sloshing around in unexpected ways, even though they have not been disturbed by any external event. Recent observational evidence shows yet another phenomenon indicating the dynamical complexity of central regions of galaxies: multiple cores (M31, Markarian 315 and 463 for example). These systems can hardly be static. We noted long-lived multiple core systems in galaxies in numerical experiments some years ago, and we have more recently followed up with a series of experiments on multiple core galaxies, starting with two cores. The relevant parameters are the energy in the orbiting clumps, their relative.masses, the (local) strength of the potential well representing the parent galaxy, and the number of cores. We have studied the dependence of the merger rates and the nature of the final merger product on these parameters. Individual cores survive much longer in stronger background potentials. Cores can survive for a substantial fraction of a Hubble time if they travel on reasonable orbits.

Investigating radial wire array Z pinches as a compact x-ray source on the Saturn generator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ampleford, David J.; Bland, S. N.; Jennings, Christopher A.

2015-08-27

Radial wire array z pinches, where wires are positioned radially outward from a central cathode to a concentric anode, can act as a compact bright x-ray source that could potentially be used to drive a hohlraum. Experiments were performed on the 7-MA Saturn generator using radial wire arrays. These experiments studied a number of potential risks in scaling radial wire arrays up from the 1-MA level, where they have been shown to be a promising compact X-ray source. Data indicates that at 7 MA, radial wire arrays can radiate ~9 TW with 10-ns full-width at half-maximum from a compact pinch.

Few-body modes of binary formation in core collapse

NASA Astrophysics Data System (ADS)

Tanikawa, Ataru; Heggie, Douglas C.; Hut, Piet; Makino, Junichiro

2013-11-01

At the moment of deepest core collapse, a star cluster core contains less than ten stars. This small number makes the traditional treatment of hard binary formation, assuming a homogeneous background density, suspect. In a previous paper, we have found that indeed the conventional wisdom of binary formation, based on three-body encounters, is incorrect. Here we refine that insight, by further dissecting the subsequent steps leading to hard binary formation. For this purpose, we add some analysis tools in order to make the study less subjective. We find that the conventional treatment does remain valid for direct three-body scattering, but fails for resonant three-body scattering. Especially democratic resonance scattering, which forms an important part of the analytical theory of three-body binary formation, takes too much space and time to be approximated as being isolated, in the context of a cluster core around core collapse. We conclude that, while three-body encounters can be analytically approximated as isolated, subsequent strong perturbations typically occur whenever those encounters give rise to democratic resonances. We present analytical estimates postdicting our numerical results. If we only had been a bit more clever, we could have predicted this qualitative behaviour.

Characteristics of switching plasma in an inverse-pinch switch

NASA Technical Reports Server (NTRS)

Lee, Ja H.; Choi, Sang H.; Venable, Demetrius D.; Han, Kwang S.; Nam, Sang H.

1993-01-01

Characteristics of the plasma that switches on tens of giga volt-ampere in an inverse-pinch plasma switch (INPIStron) have been made. Through optical and spectroscopic diagnostics of the current carrying plasma, the current density, the motion of current paths, dominant ionic species have been determined in order to access their effects on circuit parameters and material erosion. Also the optimum operational condition of the plasma-puff triggering method required for azimuthally uniform conduction in the INPIStron has been determined.

Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etchessahar, Bertrand; Bicrel, Beatrice; Cassany, Bruno

2012-09-15

The negative polarity rod pinch diode (NPRPD) is a potential millimeter spot size radiography source for high voltage generators (4 to 8 MV) [Cooperstein et al., 'Considerations of rod-pinch diode operation in negative polarity for radiography,' in Proceedings of the 14th IEEE Pulsed Power Conference, 2003, pp. 975-978]. The NPRPD consists of a small diameter (few mm) cylindrical anode extending from the front end of the vacuum cell through a thin annular cathode, held by a central conductor. The polarity has been inverted when compared to the original rod pinch diode [Cooperstein et al., 'Theoretical modeling and experimental characterization ofmore » a rod-pinch diode,' Phys. Plasmas 8(10), 4618-4636 (2001)] in order to take advantage from the maximal x-ray emission toward the anode holder at such a voltage [Swanekamp et al., 'Evaluation of self-magnetically pinched diodes up to 10 MV as high resolution flash X-ray sources,' IEEE Trans. Plasma Sci. 32(5), 2004-2016 (2004). We have studied this diode at 4.5 MV, driven by the ASTERIX generator [Raboisson et al., 'ASTERIX, a high intensity X-ray generator,' in Proceedings of the 7th IEEE Pulsed Power Conference, 1989, pp. 567-570.]. This generator, made up of a capacitor bank and a Blumlein line, was initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode has been modified in order to set up flash a radiographic diode [Etchessahar et al., 'Negative polarity rod pinch diode experiments on the ASTERIX generator,' in Conference Records-Abstracts, 37th IEEE International Conference on Plasma Science, 2010]. The experiments and numerical simulations presented here allowed the observation and analysis of various physical phenomena associated with the diode operation. Also, the influence of several experimental parameters, such as cathode and anode diameters, materials and surface states, was examined. In order to achieve the most comprehensive

Effect of particle pinch on the fusion performance and profile features of an international thermonuclear experimental reactor-like fusion reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Shijia, E-mail: wangsg@mail.ustc.edu.cn; Wang, Shaojie

2015-04-15

The evolution of the plasma temperature and density in an international thermonuclear experimental reactor (ITER)-like fusion device has been studied by numerically solving the energy transport equation coupled with the particle transport equation. The effect of particle pinch, which depends on the magnetic curvature and the safety factor, has been taken into account. The plasma is primarily heated by the alpha particles which are produced by the deuterium-tritium fusion reactions. A semi-empirical method, which adopts the ITERH-98P(y,2) scaling law, has been used to evaluate the transport coefficients. The fusion performances (the fusion energy gain factor, Q) similar to the ITERmore » inductive scenario and non-inductive scenario (with reversed magnetic shear) are obtained. It is shown that the particle pinch has significant effects on the fusion performance and profiles of a fusion reactor. When the volume-averaged density is fixed, particle pinch can lower the pedestal density by ∼30%, with the Q value and the central pressure almost unchanged. When the particle source or the pedestal density is fixed, the particle pinch can significantly enhance the Q value by  60%, with the central pressure also significantly raised.« less

Implosion dynamics of a megampere wire-array Z-pinch with an inner low-density foam shell at the Angara-5-1 facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aleksandrov, V. V.; Bolkhovitinov, E. A.; Volkov, G. S., E-mail: volkov@triniti.ru

The implosion dynamics of a pinch with a highly inhomogeneous initial axial distribution of the load mass was studied experimentally. A cascade array consisting of a double nested tungsten wire array and a coaxial inner cylindrical shell located symmetrically with respect to the high-voltage electrodes was used as a load of the Angara-5-1 high-current generator. The cylindrical foam shell was half as long as the cathode− anode gap, and its diameter was equal to the diameter of the inner wire array. It is shown experimentally that two stages are typical of the implosion dynamics of such a load: the formationmore » of two separate pinches formed as a result of implosion of the wire array near the cathode and anode and the subsequent implosion of the central part of the load containing the cylindrical foam shell. The conditions are determined at which the implosion of the central part of the pinch with the foam cylinder is preceded by intense irradiation of the foam with the soft X-ray (SXR) emission generated by the near-electrode pinches and converting it into the plasma state. Using such a load, which models the main elements of the scheme of a dynamic hohlraum for inertial confinement fusion, it is possible to increase the efficiency of interaction between the outer accelerated plasma sheath and the inner foam shell by preionizing the foam with the SXR emission of the near-electrode pinches.« less

Pinching parameters for open (super) strings

NASA Astrophysics Data System (ADS)

Playle, Sam; Sciuto, Stefano

2018-02-01

We present an approach to the parametrization of (super) Schottky space obtained by sewing together three-punctured discs with strips. Different cubic ribbon graphs classify distinct sets of pinching parameters; we show how they are mapped onto each other. The parametrization is particularly well-suited to describing the region within (super) moduli space where open bosonic or Neveu-Schwarz string propagators become very long and thin, which dominates the IR behaviour of string theories. We show how worldsheet objects such as the Green's function converge to graph theoretic objects such as the Symanzik polynomials in the α ' → 0 limit, allowing us to see how string theory reproduces the sum over Feynman graphs. The (super) string measure takes on a simple and elegant form when expressed in terms of these parameters.

Time-resolved VUV spectroscopy in the EXTRAP-T2 reversed field pinch

NASA Astrophysics Data System (ADS)

Hedqvist, Anders; Rachlew-Källne, Elisabeth

1998-09-01

Time-resolved VUV spectroscopy has been used to investigate the effects of impurities in a reversed field pinch operating with a resistive shell. Results of electron temperature, impurity ion densities, particle confinement time and 0741-3335/40/9/004/img1 together with a description of the interpretation and the equipment are presented.

The Effect of Tool Handle Shape on Hand Muscle Load and Pinch Force in a Simulated Dental Scaling Task

PubMed Central

Dong, Hui; Loomer, Peter; Barr, Alan; LaRoche, Charles; Young, Ed; Rempel, David

2007-01-01

Work-related upper extremity musculoskeletal disorders, including carpal tunnel syndrome, are prevalent among dentists and dental hygienists. An important risk factor for developing these disorders is forceful pinching which occurs during periodontal work such as dental scaling. Ergonomically designed dental scaling instruments may help reduce the prevalence of carpal tunnel syndrome among dental practitioners. In this study, 8 custom-designed dental scaling instruments with different handle shapes were used by 24 dentists and dental hygienists to perform a simulated tooth scaling task. The muscle activity of two extensors and two flexors in the forearm was recorded with electromyography while thumb pinch force was measured by pressure sensors. The results demonstrated that the instrument handle with a tapered, round shape and a 10 mm diameter required the least muscle load and pinch force when performing simulated periodontal work. The results from this study can guide dentists and dental hygienists in selection of dental scaling instruments. PMID:17156742

Scaling and Instabilities in Bubble Pinch-Off

NASA Astrophysics Data System (ADS)

Burton, J. C.; Waldrep, R.; Taborek, P.

2005-05-01

We have used a 100 000 frame-per-second video to analyze the pinch-off of nitrogen gas bubbles in fluids with a wide range of viscosity. If the external fluid is highly viscous (ηext>100 cP), the bubble neck radius is proportional to the time before break, τ, and decreases smoothly to zero. If the external fluid has low viscosity (ηext<10 cP), the radius scales as τ1/2 until an instability develops in the gas bubble, which causes the neck to rupture and tear apart. Finally, if the viscosity of the external fluid is in an intermediate range, an elongated thread is formed, which breaks apart into micron-sized bubbles.

Model for the loop voltage of reversed field pinches

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jarboe, T.R.; Alper, B.

1987-04-01

A simple model is presented that uses the concept of helicity balance to predict the toroidal loop voltage of reversed field pinches (RFP's). Data from the RFP's at Culham (Plasma Phys. Controlled Fusion 27, 1307 (1985)) are used to calibrate and verify the model. The model indicates that most of the helicity dissipation occurs in edge regions that are outside the limiters or in regions where field lines contact the walls. The value of this new interpretation to future RFP and spheromak experiments is discussed.

Investigation of trailing mass in Z-pinch implosions and comparison to experiment

NASA Astrophysics Data System (ADS)

Yu, Edmund

2007-11-01

Wire-array Z pinches represent efficient, high-power x-ray sources with application to inertial confinement fusion, high energy density plasmas, and laboratory astrophysics. The first stage of a wire-array Z pinch is described by a mass ablation phase, during which stationary wires cook off material, which is then accelerated radially inwards by the JxB force. The mass injection rate varies axially and azimuthally, so that once the ablation phase concludes, the subsequent implosion is highly 3D in nature. In particular, a network of trailing mass and current is left behind the imploding plasma sheath, which can significantly affect pinch performance. In this work we focus on the implosion phase, electing to model the mass ablation via a mass injection scheme. Such a scheme has a number of injection parameters, but this freedom also allows us to gain understanding into the nature of the trailing mass network. For instance, a new result illustrates the role of azimuthal correlation. For an implosion which is 100% azimuthally correlated (corresponding to an azimuthally symmetric 2D r-z problem), current is forced to flow on the imploding plasma sheath, resulting in strong Rayleigh-Taylor (RT) growth. If, however, the implosion is not azimuthally symmetric, the additional azimuthal degree of freedom opens up new conducting paths of lower magnetic energy through the trailing mass network, effectively reducing RT growth. Consequently the 3D implosion experiences lower RT growth than the 2D r-z equivalent, and actually results in a more shell-like implosion. A second major goal of this work is to constrain the injection parameters by comparison to a well-diagnosed experimental data set, in which array mass was varied. In collaboration with R. Lemke, M. Desjarlais, M. Cuneo, C. Jennings, D. Sinars, E. Waisman

Application of pinch-and-swell structure rheology gauge to determine rock paleo-rheological parameters in Taili, western Liaoning, NE China

NASA Astrophysics Data System (ADS)

Sun, Zhengquan; Zeng, Zuoxun; Wu, Linbo; Xu, Shaopeng; Yang, Shuang; Chen, Deli; Wang, Jianxiu

2017-05-01

New results, in combination with previously published ones, reveal that when the Stress Exponent of the Competent layer (SEC) ranges from 1 to 10 (1 < n < 10), Pinch-and-Swell structure Rheology Gauge (PSRG) can only be available under the condition that the Viscosity ratio between the Competent layer and its corresponding Matrix layer (VCM) is larger than 10. Therefore, we made the attempt to calculate the viscosity ratio of pinch-and-swell structure of competent layer to the related matrix and stress exponent. Based on this knowledge, we applied this gauge to calculate SECs and VCMs of eight types of pinch-and-swell structures, which are widely developed in the Taili area of the west Liaoning Province in China. Statistical analysis of the SEC resulted in intervals of four types of competent layers, that is, Medium-scale Granitic coarse-to-pegmatitic Veins, Small-scale Augen Granite aplite Veins, Small-scale Granite aplite Veins, and Small-scale Augen Quartz-K-feldspar veins, with intervals of [3.50, 4.63], [2.64, 4.29], [2.70, 3.51], and [2.50, 3.36] respectively. The preferred intervals of VCM of the five types of pinch-and-swell structures, Small-scale Augen Granite aplite Veins + Fine-grained Biotite-Hornblende-plagioclase Gneiss, Medium-scale Granitic coarse-to-pegmatitic Veins + Fine-grained Biotite-Hornblende-plagioclase Gneiss, Small-scale Augen Granite aplite Veins + medium-to-fine-grained granitic gneiss, Medium-scale Granitic coarse-to-pegmatitic Veins + medium-to-fine-grained granitic gneiss, and Small-scale Augen Granite aplite Veins + fine-grained biotite-plagioclase gneiss, are [19.98, 62.51], [15.90, 61.17], [26.72, 93.27], [22.21, 107.26], and [76.33, 309.39] respectively. The similarities between these calculated SEC statistical preferred intervals and the physical experimental results verify the validity of the PSRG. The competent layers of the pinch-and-swell structures were presented in this study as power-law flow with SEC values that

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas

NASA Astrophysics Data System (ADS)

Wallace, M. S.; Haque, S.; Neill, P.; Pereira, N. R.; Presura, R.

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Spatially resolved single crystal x-ray spectropolarimetry of wire array z-pinch plasmas.

PubMed

Wallace, M S; Haque, S; Neill, P; Pereira, N R; Presura, R

2018-01-01

A recently developed single-crystal x-ray spectropolarimeter has been used to record paired sets of polarization-dependent and axially resolved x-ray spectra emitted by wire array z-pinches. In this measurement, two internal planes inside a suitable crystal diffract the x-rays into two perpendicular directions that are normal to each other, thereby separating incident x-rays into their linearly polarized components. This paper gives considerations for fielding the instrument on extended sources. Results from extended sources are difficult to interpret because generally the incident x-rays are not separated properly by the crystal. This difficulty is mitigated by using a series of collimating slits to select incident x-rays that propagate in a plane of symmetry between the polarization-splitting planes. The resulting instrument and some of the spatially resolved polarized x-ray spectra recorded for a 1-MA aluminum wire array z-pinch at the Nevada Terawatt Facility at the University of Nevada, Reno will be presented.

Performance of a Liner-on-Target Injector for Staged Z-Pinch Experiments

NASA Astrophysics Data System (ADS)

Conti, F.; Valenzuela, J. C.; Narkis, J.; Krasheninnikov, I.; Beg, F.; Wessel, F. J.; Ruskov, E.; Rahman, H. U.; McGee, E.

2016-10-01

We present the design and characterization of a compact liner-on-target injector, used in the Staged Z-pinch experiments conducted on the UNR-NTF Zebra Facility. Previous experiments and analysis indicate that high-Z gas liners produce a uniform and efficient implosion on a low-Z target plasma. The liner gas shell is produced by an annular solenoid valve and a converging-diverging nozzle designed to achieve a collimated, supersonic, Mach-5 flow. The on-axis target is produced by a coaxial plasma gun, where a high voltage pulse is applied to ionize neutral gas and accelerate the plasma by the J-> × B-> force. Measurements of the liner and target dynamics, resolved by interferometry in space and time, fast imaging, and collection of the emitted light, are presented. The results are compared to the predictions from Computational Fluid Dynamics and MHD simulations that model the injector. Optimization of the design parameters, for upcoming Staged Z-pinch experiments, will be discussed. Advanced Research Projects Agency - Energy, DE-AR0000569.

Impurity transport in enhanced confinement regimes in RFX-mod Reversed Field Pinch

NASA Astrophysics Data System (ADS)

Carraro, Lorella; Menmuir, Sheena; Fassina, Alessandro

2010-11-01

The results of impurity transport studies in RFX-mod enhanced confinement quasi-single helicity (QSH) and single helical axis (SHAx) regimes are presented and discussed. The impurity diffusion coefficient and pinch velocity are obtained through comparing experimental emission pattern (line emission and SXR time evolutions, SXR profiles) with the results of a 1-D impurity transport code. Previous analysis [S. Menmuir et al. to be published in Plasma Phys. Contr. Fus.] of impurity transport in RFX-mod standard discharges showed that the impurity pinch velocity, always directed outwards, features a barrier with high values around r/a = 0.8, where the diffusion coefficient decreases by one order of magnitude. In the QSH regime, the transition region in D and v is more internal and the barrier in velocity is wider and stronger. New results have been obtained in experiments with Ni laser blow-off (LBO) injection in high current discharges (Ip>1.5 MA) with long lasting QSH, to better characterize the Ni behavior inside the helical magnetic topology.

Mode- and plasma rotation in a resistive shell reversed-field pinch

NASA Astrophysics Data System (ADS)

Malmberg, J.-A.; Brzozowski, J.; Brunsell, P. R.; Cecconello, M.; Drake, J. R.

2004-02-01

Mode rotation studies in a resistive shell reversed-field pinch, EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Control. Fusion 43, 1 (2001)] are presented. The phase relations and nonlinear coupling of the resonant modes are characterized and compared with that expected from modeling based on the hypothesis that mode dynamics can be described by a quasi stationary force balance including electromagnetic and viscous forces. Both m=0 and m=1 resonant modes are studied. The m=1 modes have rotation velocities corresponding to the plasma flow velocity (20-60 km/s) in the core region. The rotation velocity decreases towards the end of the discharge, although the plasma flow velocity does not decrease. A rotating phase locked m=1 structure is observed with a velocity of about 60 km/s. The m=0 modes accelerate throughout the discharges and reach velocities as high as 150-250 km/s. The observed m=0 phase locking is consistent with theory for certain conditions, but there are several conditions when the dynamics are not described. This is not unexpected because the assumption of quasi stationarity for the mode spectra is not fulfilled for many conditions. Localized m=0 perturbations are formed in correlation with highly transient discrete dynamo events. These perturbations form at the location of the m=1 phase locked structure, but rotate with a different velocity as they spread out in the toroidal direction.

Hard sphere perturbation theory for fluids with soft-repulsive-core potentials

NASA Astrophysics Data System (ADS)

Ben-Amotz, Dor; Stell, George

2004-03-01

The thermodynamic properties of fluids with very soft repulsive-core potentials, resembling those of some liquid metals, are predicted with unprecedented accuracy using a new first-order thermodynamic perturbation theory. This theory is an extension of Mansoori-Canfield/Rasaiah-Stell (MCRS) perturbation theory, obtained by including a configuration integral correction recently identified by Mon, who evaluated it by computer simulation. In this work we derive an analytic expression for Mon's correction in terms of the radial distribution function of the soft-core fluid, g0(r), approximated using Lado's self-consistent extension of Weeks-Chandler-Andersen (WCA) theory. Comparisons with WCA and MCRS predictions show that our new extended-MCRS theory outperforms other first-order theories when applied to fluids with very soft inverse-power potentials (n⩽6), and predicts free energies that are within 0.3kT of simulation results up to the fluid freezing point.

A reassessment study of multi-material-shell gas puff z-pinches as a pulsed neutron source on the sandia ZR

NASA Astrophysics Data System (ADS)

Chong, Y. K.; Velikovich, A. L.; Thornhil, J. W.; Giuliani, J. L.; Knapp, P.; Jennings, C.

2013-10-01

Over the last few years, numerous 1D and 2D MHD simulation studies of deuterium (D) based double-shell gas-puff Z-pinch implosions driven by the Sandia ZR accelerator have been carried out to assess the Z-pinch as a pulsed thermal fusion neutron source. In these studies, an ad-hoc time-dependent shunt impedance model was used within the external driving circuit model in order to account for the unresolved current loss in the MITL and the load. In this study, we incorporate an improved ZR circuit model recently formulated based on the recent Sandia argon gas-puff experiment circuit data into the multi-material version of the Mach +DDTCRE RMHD code. We reinvestigate the effects of multidimensional structure and nonuniform gradients as well as the outer- and inner-shell material interaction on the implosion physics and dynamics of both D-on-D and argon-on-D Z-pinch loads using the model. Then, we characterize the neutron production performance of the Z-pinch loads as a function of total mass, mass ratio and/or radius toward their optimization as a pulsed thernonuclear neutron source. Work supported by DOE/NNSA. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. DOE's NNSA under contract DE-AC04-94AL85000.

Diagnosis from functional perspectives: usefulness of a manual tactile test for predicting precision pinch performance and disease severity in subjects with carpal tunnel syndrome.

PubMed

Hsu, Hsiu-Yun; Kuo, Yao-Lung; Jou, I-Ming; Su, Fong-Chin; Chiu, Haw-Yen; Kuo, Li-Chieh

2014-04-01

To investigate how the severity levels revealed in a nerve conduction study (NCS) affect the results of the Manual Tactile Test (MTT) for patients with carpal tunnel syndrome (CTS), and to examine the relationships between the results of the MTT and precision pinch performance. Case-control studies. Hospital and local community. Patients with CTS (N=70) with 119 affected hands were studied. A control group matched by age, sex, and hand dominance was also recruited. Not applicable. CTS severity was determined based on NCS findings. The MTT, traditional sensory tests, and precision pinch performance were used to examine the functional sensory status of the hand from different perspectives. The patients with CTS exhibited deterioration in all of the sensibility tests (P<.001). The results showed that the MTT could classify subgroups of severity in CTS (P<.001). A moderate correlation was found between the results of the MTT and precision pinch performance (r=.526-.585, P<.001). Multiple linear regression analysis showed that the MTT results were useful indicators for predicting precision pinch performance and differentiating severity in subjects with CTS (r(2)=.376 and .323, respectively). The findings indicate that the MTT could be a valid and useful assessment for hand sensibility and prehensile pinch performance in patients with CTS. Copyright © 2014 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Experimental study of self magnetic pinch diode as flash radiography source at 4 megavolt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Etchessahar, Bertrand; Bicrel, Béatrice; Cassany, Bruno

2013-10-15

The Self Magnetic Pinch (SMP) diode is a potential high-brightness X-ray source for high voltage generators (2–10 MV) that has shown good reliability for flash radiography applications [D. D. Hinchelwood et al., “High power self-pinch diode experiments for radiographic applications” IEEE Trans. Plasma Sci. 35(3), 565–572 (2007)]. We have studied this diode at about 4 MV, driven by the ASTERIX generator operated at the CEA/GRAMAT [G. Raboisson et al., “ASTERIX, a high intensity X-ray generator,” in Proceedings of the 7th IEEE Pulsed Power Conference (1989), pp. 567–570]. This generator, made up of a capacitor bank and a Blumlein line, wasmore » initially designed to test the behavior of electronic devices under irradiation. In our experiments, the vacuum diode is modified in order to set up flash radiographic diodes. A previous set of radiographic experiments was carried out on ASTERIX with a Negative Polarity Rod Pinch (NPRP) diode [B. Etchessahar et al., “Study and optimization of negative polarity rod pinch diode as flash radiography source at 4.5 MV,” Phys. Plasmas 19(9), 093104 (2012)]. The SMP diode which is examined in the present study provides an alternative operating point on the same generator and a different radiographic performance: 142 ± 11 rad at 1 m dose (Al) for a 3.46 ± 0.42 mm spot size (1.4× FWHM of the LSF). This performance is obtained in a reproducible and robust nominal configuration. However, several parametric variations were also tested, such as cathode diameter and anode/cathode gap. They showed that an even better performance is accessible after optimization, in particular, a smaller spot size (<3 mm). Numbers of electrical, optical, and X-ray diagnostics have been implemented in order to gain more insight in the diode physics and to optimize it further. For the first time in France, visible and laser imaging of the SMP diode has been realized, from a radial point of view, thus, providing key information on the

Dynamic characteristics of azimuthally correlated structures of axial instability of wire-array Z pinches

NASA Astrophysics Data System (ADS)

Dan, Jia Kun; Huang, Xian Bin; Ren, Xiao Dong; Chen, Guang Hua; Xu, Qiang; Wang, Kun Lun; Ouyang, Kai; Wei, Bing

2017-04-01

Particular attention was placed on observations of dynamic properties of the azimuthally correlated structures of axial instability of wire-array Z pinches, which were conducted at 10-MA (for short circuit load) pulsed power generator-the Primary Test Stand facility. Not well fabricated loads, which were expected to preset bubble or spike in plasma, were used to degrade the implosion symmetry in order to magnify the phenomenon of instability. The side-view sequence of evolution of correlation given by laser shadowgraphy clearly demonstrates the dynamic processes of azimuthal correlation of the bubble and spike. A possible mechanism presented here suggests that it is the substantial current redistribution especially in regions surrounding the bubble/spike resulting from change of inductance due to the presence of the bubble/spike that plays an essential part in establishment of azimuthal correlation of wire array and liner Z pinches.

Axisymmetric bubble pinch-off at high Reynolds numbers.

PubMed

Gordillo, J M; Sevilla, A; Rodríguez-Rodríguez, J; Martínez-Bazán, C

2005-11-04

Analytical considerations and potential-flow numerical simulations of the pinch-off of bubbles at high Reynolds numbers reveal that the bubble minimum radius, rn, decreases as tau proportional to r2n sqrt[1lnr2n], where tau is the time to break up, when the local shape of the bubble near the singularity is symmetric. However, if the gas convective terms in the momentum equation become of the order of those of the liquid, the bubble shape is no longer symmetric and the evolution of the neck changes to a rn proportional to tau1/3 power law. These findings are verified experimentally.

Electron beam generation in the turbulent plasma of Z-pinch discharges

NASA Astrophysics Data System (ADS)

Vikhrev, Victor V.; Baronova, Elena O.

1997-05-01

Numerical modeling of the process of electron beam generation in z-pinch discharges are presented. The proposed model represents the electron beam generation under turbulent plasma conditions. Strong current distribution inhomogeneity in the plasma column has been accounted for the adequate generation process investigation. Electron beam is generated near the maximum of compression due to run away mechanism and it is not related with the current break effect.

Experimental study of surface insulated-standard hybrid tungsten planar wire array Z-pinches at “QiangGuang-I” facility

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sheng, Liang; Peng, Bodong; Yuan, Yuan

The experimental results of the insulated-standard hybrid wire array Z pinches carried out on “QiangGuang-I” facility at Northwest Institute of Nuclear Technology were presented and discussed. The surface insulating can impose a significant influence on the dynamics and radiation characteristics of the hybrid wire array Z pinches, especially on the early stage (t/t{sub imp} < 0.6). The expansion of insulated wires at the ablation stage is suppressed, while the streams stripped from the insulated wires move faster than that from the standard wires. The foot radiation of X-ray is enhanced by increment of the number of insulated wires, 19.6 GW, 33.6 GW, and 68.6 GWmore » for shots 14037S, 14028H, and 14039I, respectively. The surface insulation also introduces nonhomogeneity along the single wire—the streams move much faster near the electrodes. The colliding boundary of the hybrid wire array Z pinches is bias to the insulated side approximately 0.6 mm.« less

The visceromotor responses to colorectal distension and skin pinch are inhibited by simultaneous jejunal distension.

PubMed

Shafton, Anthony D; Furness, John B; Ferens, Dorota; Bogeski, Goce; Koh, Shir Lin; Lean, Nicholas P; Kitchener, Peter D

2006-07-01

Noxious stimuli that are applied to different somatic sites interact; often one stimulus diminishes the sensation elicited from another site. By contrast, inhibitory interactions between visceral stimuli are not well documented. We investigated the interaction between the effects of noxious distension of the colorectum and noxious stimuli applied to the jejunum, in the rat. Colorectal distension elicited a visceromotor reflex, which was quantified using electromyographic (EMG) recordings from the external oblique muscle of the upper abdomen. The same motor units were activated when a strong pinch was applied to the flank skin. Distension of the jejunum did not provoke an EMG response at this site, but when it was applied during colorectal distension it blocked the EMG response. Jejunal distension also inhibited the response to noxious skin pinch. The inhibition of the visceromotor response to colorectal distension was prevented by local application of tetrodotoxin to the jejunum, and was markedly reduced when nicardipine was infused into the local jejunal circulation. Chronic sub-diaphragmatic vagotomy had no effect on the colorectal distension-induced EMG activity or its inhibition by jejunal distension. The nicotinic antagonist hexamethonium suppressed phasic contractile activity in the jejunum, had only a small effect on the inhibition of visceromotor response by jejunal distension. It is concluded that signals that arise from skin pinch and colorectal distension converge in the central nervous system with pathways that are activated by jejunal spinal afferents; the jejunal signals strongly inhibit the abdominal motor activity evoked by noxious stimuli.

Solar Hard X-ray Observations with NuSTAR

NASA Astrophysics Data System (ADS)

Marsh, Andrew; Smith, D. M.; Krucker, S.; Hudson, H. S.; Hurford, G. J.; White, S. M.; Mewaldt, R. A.; Harrison, F. A.; Grefenstette, B. W.; Stern, D.

2012-05-01

High-sensitivity imaging of coronal hard X-rays allows detection of freshly accelerated nonthermal electrons at the acceleration site. A few such observations have been made with Yohkoh and RHESSI, but a leap in sensitivity could help pin down the time, place, and manner of reconnection. Around the time of this meeting, the Nuclear Spectroscopic Telescope ARray (NuSTAR), a NASA Small Explorer for high energy astrophysics that uses grazing-incidence optics to focus X-rays up to 80 keV, will be launched. Three weeks will be dedicated to solar observing during the baseline two-year mission. NuSTAR will be 200 times more sensitive than RHESSI in the hard X-ray band. This will allow the following new observations, among others: 1) Extrapolation of the micro/nanoflare distribution by two orders of magnitude down in flux; 2) Search for hard X-rays from network nanoflares (soft X-ray bright points) and evaluation of their role in coronal heating; 3) Discovery of hard X-ray bremsstrahlung from the electron beams driving type III radio bursts, and measurement of their electron spectrum; 4) Hard X-ray studies of polar soft X-ray jets and impulsive solar energetic particle events at the edge of coronal holes; 5) Study of coronal bremsstrahlung from particles accelerated by coronal mass ejections as they are first launched; 6) Study of particles at the coronal reconnection site when flare footpoints and loops are occulted; 7) Search for weak high-temperature coronal plasmas in active regions that are not flaring; and 8) Search for hypothetical axion particles created in the solar core via the hard X-ray signal from their conversion to X-rays in the coronal magnetic field. NuSTAR will also serve as a pathfinder for a future dedicated space mission with enhanced capabilities, such as a satellite version of the FOXSI sounding rocket.

Grip force regulation during pinch grip lifts under somatosensory guidance: comparison between people with stroke and healthy controls.

PubMed

Blennerhassett, Jannette M; Carey, Leeanne M; Matyas, Thomas A

2006-03-01

To compare the timing and grip force application in a pinch grip task performed under somatosensory guidance in stroke and matched controls and to identify characteristics of impaired grip force regulation after stroke. Matched-pairs control group. University research laboratory. Forty-five people with stroke who could pick up a pen lid using a pinch grip and actively participated in rehabilitation and 45 adults without neurologic conditions or musculoskeletal or skin impairments affecting the hand, matched for age, sex, and hand dominance. Not applicable. Timing and magnitude of grip forces applied during pinch grip lift and hold. Prolonged time to grip and lift objects, and excessive grip force prior to commencing the lift occurred in approximately half of the contralesional (involved) hands of people with stroke. Fluctuating irregular forces and reduced adaptation of the grip safety margin were also observed. Excessive safety margins were not predominant after stroke. Extreme slowing and disorganized sequencing of the grip and lifting forces and difficulty maintaining a stable grip characterized severe dysfunction. Delayed grip formulation and variable grip force application are key characteristics of grip dysfunction after stroke.

Evaluating Core Quality for a Mars Sample Return Mission

NASA Technical Reports Server (NTRS)

Weiss, D. K.; Budney, C.; Shiraishi, L.; Klein, K.

2012-01-01

Sample return missions, including the proposed Mars Sample Return (MSR) mission, propose to collect core samples from scientifically valuable sites on Mars. These core samples would undergo extreme forces during the drilling process, and during the reentry process if the EEV (Earth Entry Vehicle) performed a hard landing on Earth. Because of the foreseen damage to the stratigraphy of the cores, it is important to evaluate each core for rock quality. However, because no core sample return mission has yet been conducted to another planetary body, it remains unclear as to how to assess the cores for rock quality. In this report, we describe the development of a metric designed to quantitatively assess the mechanical quality of any rock cores returned from Mars (or other planetary bodies). We report on the process by which we tested the metric on core samples of Mars analogue materials, and the effectiveness of the core assessment metric (CAM) in assessing rock core quality before and after the cores were subjected to shocking (g forces representative of an EEV landing).

Pinching solutions of slender cylindrical jets

NASA Technical Reports Server (NTRS)

Papageorgiou, Demetrios T.; Orellana, Oscar

1993-01-01

Simplified equations for slender jets are derived for a circular jet of one fluid flowing into an ambient second fluid, the flow being confined in a circular tank. Inviscid flows are studied which include both surface tension effects and Kelvin-Helmholtz instability. For slender jets a coupled nonlinear system of equations is found for the jet shape and the axial velocity jump across it. The equations can break down after a finite time and similarity solutions are constructed, and studied analytically and numerically. The break-ups found pertain to the jet pinching after a finite time, without violation of the slender jet ansatz. The system is conservative and admissible singular solutions are those which conserve the total energy, mass, and momentum. Such solutions are constructed analytically and numerically, and in the case of vortex sheets with no surface tension certain solutions are given in closed form.

The Role of Body Crystallization in Asteroidal Cores

NASA Astrophysics Data System (ADS)

Wasson, J. T.

1993-07-01

Large fractionations (factors of 2000-6000) in Ir/Ni and other ratios demonstrate that the magmatic groups of iron meteorites formed by fractional crystallization, and thus that the residual liquid remained well stirred during core crystallization. Past models have relied on solidification at the base or the top of the core, but body crystallization offers an attractive alternative. The simplest of the earlier models involved convective maxing induced by the liberation of heat and light elements (especially S) during upward crystallization from the center of the core. Other models involving downward crystallization from the core-mantle interface are based on the fact that temperatures at this location are slightly lower than those at the center; no whole-core stirring mechanism is provided by these models. Haack and Scott recently published a variant of the downward crystallization model involving the growth of giant (kilometer-scale) dendrites. Because crystallization creates a boundary layer enriched in S that does not participate in the convection, these models require several K of supercooling to induce crystallization (this undercooling is much greater than the temperature difference between the center of the core and the core-mantle interface). Buoyant forces will occasionally remove droplets of the basal boundary fluid; thus it was thinner and its degree of undercooling less than in that at the ceiling of the magma chamber. Homogeneous nucleation of metals is difficult to achieve; generally 200-300 K of undercooling is required, much more than could possibly occur in an asteroidal core. Crystals could, however, nucleate in the magma body on chromite, probably the first liquidus phase (A. Kracher, personal communication, notes that this is required to explain why Cr behaved like a compatible element despite having a solid/liquid D < 1). In addition, some tiny, submillimeter dendrites that formed at the top of the core must have pinched off and fallen into the

Z pinches as intense x-ray sources for high-energy density physics applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Matzen, M.K.

1997-05-01

Fast Z-pinch implosions can efficiently convert the stored electrical energy in a pulsed-power accelerator into x rays. These x rays are produced when an imploding cylindrical plasma, driven by the magnetic field pressure associated with very large axial currents, stagnates upon the cylindrical axis of symmetry. On the Saturn pulsed-power accelerator [R. B. Spielman {ital et al.}, in {ital Proceedings of the 2nd International Conference on Dense Z Pinches}, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] at Sandia National Laboratories, for example, currents ofmore » 6{endash}8 MA with a rise time of less than 50 ns are driven through cylindrically symmetric loads, producing implosion velocities as high as 10{sup 8}cm/s and x-ray energies exceeding 400 kJ. Hydromagnetic Rayleigh{endash}Taylor instabilities and cylindrical load symmetry are critical, limiting factors in determining the assembled plasma densities and temperatures, and thus in the x-ray energies and pulse widths that can be produced on these accelerators. In recent experiments on the Saturn accelerator, these implosion nonuniformities have been minimized by using wire arrays with as many as 192 wires. Increasing the wire number produced significant improvements in the pinched plasma quality, reproducibility, and x-ray output power. X-ray pulse widths of less than 5 ns and peak powers of 75{plus_minus}10TW have been achieved with arrays of 120 tungsten wires. Similar loads have recently been fielded on the Particle Beam Fusion Accelerator (PBFA II), producing x-ray energies in excess of 1.8 MJ at powers in excess of 160 TW. These intense x-ray sources offer the potential for performing many new basic physics and fusion-relevant experiments. {copyright} {ital 1997 American Institute of Physics.}« less

Radiation characteristics and implosion dynamics of Z-pinch dynamic hohlraums performed on PTS facility

NASA Astrophysics Data System (ADS)

Huang, Xian Bin; Ren, Xiao Dong; Dan, Jia Kun; Wang, Kun Lun; Xu, Qiang; Zhou, Shao Tong; Zhang, Si Qun; Cai, Hong Chun; Li, Jing; Wei, Bing; Ji, Ce; Feng, Shu Ping; Wang, Meng; Xie, Wei Ping; Deng, Jian Jun

2017-09-01

The preliminary experimental results of Z-pinch dynamic hohlraums conducted on the Primary Test Stand (PTS) facility are presented herein. Six different types of dynamic hohlraums were used in order to study the influence of load parameters on radiation characteristics and implosion dynamics, including dynamic hohlraums driven by single and nested arrays with different array parameters and different foams. The PTS facility can deliver a current of 6-8 MA in the peak current and 60-70 ns in the 10%-90% rising time to dynamic hohlraum loads. A set of diagnostics monitor the implosion dynamics of plasmas, the evolution of shock waves in the foam and the axial/radial X-ray radiation, giving the key parameters characterizing the features of dynamic hohlraums, such as the trajectory and related velocity of shock waves, radiation temperature, and so on. The experimental results presented here put our future study on Z-pinch dynamic hohlraums on the PTS facility on a firm basis.

Composite nanoplatelets combining soft-magnetic iron oxide with hard-magnetic barium hexaferrite

NASA Astrophysics Data System (ADS)

Primc, D.; Makovec, D.

2015-01-01

By coupling two different magnetic materials inside a single composite nanoparticle, the shape of the magnetic hysteresis can be engineered to meet the requirements of specific applications. Sandwich-like composite nanoparticles composed of a hard-magnetic Ba-hexaferrite (BaFe12O19) platelet core in between two soft-magnetic spinel iron oxide maghemite (γ-Fe2O3) layers were synthesized using a new, simple and inexpensive method based on the co-precipitation of Fe3+/Fe2+ ions in an aqueous suspension of hexaferrite core nanoparticles. The required close control of the supersaturation of the precipitating species was enabled by the controlled release of the Fe3+ ions from the nitrate complex with urea ([Fe((H2N)2C&z.dbd;O)6](NO3)3) and by using Mg(OH)2 as a solid precipitating agent. The platelet Ba-hexaferrite nanoparticles of different sizes were used as the cores. The controlled coating resulted in an exclusively heterogeneous nucleation and the topotactic growth of the spinel layers on both basal surfaces of the larger hexaferrite nanoplatelets. The direct magnetic coupling between the core and the shell resulted in a strong increase of the energy product |BH|max. Ultrafine core nanoparticles reacted with the precipitating species and homogeneous product nanoparticles were formed, which differ in terms of the structure and composition compared to any other compound in the BaO-Fe2O3 system.By coupling two different magnetic materials inside a single composite nanoparticle, the shape of the magnetic hysteresis can be engineered to meet the requirements of specific applications. Sandwich-like composite nanoparticles composed of a hard-magnetic Ba-hexaferrite (BaFe12O19) platelet core in between two soft-magnetic spinel iron oxide maghemite (γ-Fe2O3) layers were synthesized using a new, simple and inexpensive method based on the co-precipitation of Fe3+/Fe2+ ions in an aqueous suspension of hexaferrite core nanoparticles. The required close control of the

Turbulent energy transfer in electromagnetic turbulence: hints from a Reversed Field Pinch plasma

NASA Astrophysics Data System (ADS)

Vianello, N.; Bergsaker, H.

2005-10-01

The relationship between electromagnetic turbulence and sheared plasma flow in a Reversed Field Pinch is addressed. ExB sheared flows and turbulence at the edge tends to organize themeselves near marginal stability, suggesting an underlying energy exchange process between turbulence and mean flow. In MHD this process is well described through the quantity P which represents the energy transfer (per mass and time unit) from turbulence to mean fields. In the edge region of RFP configuration, where magnetic field is mainly poloidal and the mean ExB is consequently toroidal, the quantity P results: P =[ -ρμ0 + ]Vφr where Vφ is the mean ExB toroidal flow, ρ the mean mass density and b and v the fluctuations of velocity and magnetic field respectively. Both the radial profiles and the temporal evolution of P have been measured in the edge region of Extrap-T2R Reversed Field Pinch experiment. The results support the existence of oscillating energy exchange process between fluctuations and mean flow.

Drop formation, pinch-off dynamics and liquid transfer of simple and complex fluids

NASA Astrophysics Data System (ADS)

Dinic, Jelena; Sharma, Vivek

Liquid transfer and drop formation processes underlying jetting, spraying, coating, and printing - inkjet, screen, roller-coating, gravure, nanoimprint hot embossing, 3D - often involve formation of unstable columnar necks. Capillary-driven thinning of such necks and their pinchoff dynamics are determined by a complex interplay of inertial, viscous and capillary stresses for simple, Newtonian fluids. Micro-structural changes in response to extensional flow field that arises within the thinning neck give rise to additional viscoelastic stresses in complex, non- Newtonian fluids. Using FLOW-3D, we simulate flows realized in prototypical geometries (dripping and liquid bridge stretched between two parallel plates) used for studying pinch-off dynamics and influence of microstructure and viscoelasticity. In contrast with often-used 1D or 2D models, FLOW-3D allows a robust evaluation of the magnitude of the underlying stresses and extensional flow field (both uniformity and magnitude). We find that the simulated radius evolution profiles match the pinch-off dynamics that are experimentally-observed and theoretically-predicted for model Newtonian fluids and complex fluids.

Turbulence, flow and transport: hints from reversed field pinch

NASA Astrophysics Data System (ADS)

Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.

2006-04-01

The interplay between sheared E × B flows and turbulence has been experimentally investigated in the edge region of the Extrap-T2R reversed field pinch experiment. Electrostatic fluctuations are found to rule the momentum balance equation representing the main driving term for sheared flows which counterbalances anomalous viscous damping. The driving role of electrostatic fluctuations is proved by the spatial structure of the Reynolds stress and by the time behaviour of the mean energy production term which supports the existence of an energy exchange from the small scales of turbulence to the larger scales of the mean flow.

Non-Laminar Flow Model for the Impedance of a Rod-Pinch Diode

NASA Astrophysics Data System (ADS)

Ottinger, Paul F.; Schumer, Joseph W.; Strasburg, Sean D.; Swanekamp, Stephen B.; Oliver, Bryan V.

2002-12-01

A previous laminar flow model for the rod-pinch diode is extended to include a transverse pressure term to study the effects of non-laminar flow. The non-laminar nature of the flow has a significant impact on the diode impedance. Results show that the introduction of the transverse pressure decreases the diode impedance predicted by the model bringing it into better agreement with experimental data.

Magnetization processes in core/shell exchange-spring structures.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, J. S.

2015-03-27

The magnetization reversal processes in cylindrical and spherical soft core/hard shell exchange-spring structures are investigated via the analytical nucleation theory, and are verified with numerical micromagnetic simulations. At small core sizes, the nucleation of magnetic reversal proceeds via the modified bulging mode, where the transverse component of the magnetization is only semi-coherent in direction and the nucleation field contains a contribution from self-demagnetization. For large core sizes, the modified curling mode, where the magnetization configuration is vortex-like, is favored at nucleation. The preference for the modified curling mode is beneficial in that the fluxclosure allows cylindrical and spherical core/shell exchange-springmore » elements to be densely packed into bulk permanent magnets without affecting the nucleation field, thereby offering the potential for high energy product.« less

Shape evolution of a core-shell spherical particle under hydrostatic pressure.

PubMed

Colin, Jérôme

2012-03-01

The morphological evolution by surface diffusion of a core-shell spherical particle has been investigated theoretically under hydrostatic pressure when the shear modulii of the core and shell are different. A linear stability analysis has demonstrated that depending on the pressure, shear modulii, and radii of both phases, the free surface of the composite particle may be unstable with respect to a shape perturbation. A stability diagram finally emphasizes that the roughness development is favored in the case of a hard shell with a soft core.

System for phase-contrast x-ray radiography using X pinch radiation and a method thereof

DOEpatents

Chandler, Katherine; Chelkovenko, Tatiana; Hammer, David; Pikuz, Sergei; Sinars, Daniel; Song, Byungmoo

2007-11-06

A radiograph system with an anode plate, a cathode plate, and a power source coupled to said anode plate and the cathode plate. At least two wires coupled between the anode plate and the cathode plate provide a configuration to form an X-pinch having a photon source size of less than five microns at energies above 2.5 keV. Material at the configuration forming the X-pinch vaporizes upon application of a suitable current to the wires forming a dense hot plasma and emitting a single x-ray pulse with sufficient photons having energies in the range of from about 2.5 keV to about 20 keV to provide a phase contrast image of an object in the path of the photons. Multiple simultaneous images may be formed of a plurality of objects. Suitable filters and x-ray detectors are provided.

Feasibility of a Novel Functional Sensibility Test as an Assisted Examination for Determining Precision Pinch Performance in Patients with Carpal Tunnel Syndrome

PubMed Central

Hsu, Hsiu-Yun; Kuo, Li-Chieh; Kuo, Yao-Lung; Chiu, Haw-Yen; Jou, I-Ming; Wu, Po-Ting; Su, Fong-Chin

2013-01-01

To understand the feasibility of a novel functional sensibility test for determining precision pinch performance in patients with carpal tunnel syndrome, this study investigates the validity, sensitivity and specificity of functional sensibility derived from a pinch-holding-up activity (PHUA) test. Participants include 70 clinically defined carpal tunnel syndrome (CTS) patients with 119 involved hands and 70 age- and gender-matched controls. To examine the discriminating ability of the functional sensibility test, the differences in the ability of pinch force adjustments to the inertial load of handling object between CTS and control subjects are analyzed. The results of functional sensibility are correlated with the severity of CTS to establish concurrent validity. The receiver operating characteristic (ROC) curve is constructed to demonstrate the accuracy of the proposed test. The functional sensibility score significantly discriminates the patients and control groups (respectively, 12.94±1.72 vs. 11.51±1.15N in peak pinch force (FPPeak), p<0.001; 2.92±0.41 vs. 2.52±0.24 in force ratio, p<0.001) and is moderately correlated (r = 0.42–0.54, p<0.001) with the results of traditional sensibility tests (touch-pressure threshold and two-point discrimination test). In addition, there is a statistical difference in the results of functional sensibility (p<0.001) among the subgroups of CTS severity based on electrophysiological study. The sensitivity and specificity are 0.79 and 0.76, respectively, for the functional sensibility test. The areas under the ROC curve are 0.85 and 0.80 for the force ratio and FPPeak, respectively. In conclusion, the functional sensibility test could be feasibly used as a clinical tool for determining both the sensibility and precision pinch performance of hands for the patients with CTS. PMID:23977209

Bilateral deficits in fine motor control and pinch grip force are not associated with electrodiagnostic findings in women with carpal tunnel syndrome.

PubMed

de la Llave-Rincón, Ana Isabel; Fernández-de-Las-Peñas, César; Pérez-de-Heredia-Torres, Marta; Martínez-Perez, Almudena; Valenza, Marie Carmen; Pareja, Juan A

2011-06-01

: The aim of this study was to analyze the differences in deficits in fine motor control and pinch grip force between patients with minimal, moderate/mild, or severe carpal tunnel syndrome (CTS) and healthy age- and hand dominance-matched controls. : A case-control study was conducted. The subtests of the Purdue Pegboard Test (one-hand and bilateral pin placements and assemblies) and pinch grip force between the thumb and the remaining four fingers of the hand were bilaterally evaluated in 66 women with minimal (n = 16), moderate (n = 16), or severe (n = 34) CTS and in 20 age- and hand-matched healthy women. The differences among the groups were analyzed using different mixed models of analysis of variance. : A two-way mixed analysis of variance revealed significant differences between groups, not depending on the presence of unilateral or bilateral symptoms (side), for the one-hand pin placement subtest: patients showed bilateral lower scores compared with controls (P < 0.001), without differences among those with minimal, moderate, or severe CTS (P = 0.946). The patients also exhibited lower scores in bilateral pin placement (P < 0.001) and assembly (P < 0.001) subtests, without differences among them. The three-way analysis of variance revealed significant differences among groups (P < 0.001) and fingers (P < 0.001), not depending on the presence of unilateral/bilateral symptoms (P = 0.684), for pinch grip force: patients showed bilateral lower pinch grip force in all fingers compared with healthy controls, without differences among those with minimal, moderate, or severe CTS. : The current study revealed similar bilateral deficits in fine motor control and pinch grip force in patients with minimal, moderate, or severe CTS, supporting that fine motor control deficits are a common feature of CTS not associated with electrodiagnostic findings.

Generating unstructured nuclear reactor core meshes in parallel

DOE PAGES

Jain, Rajeev; Tautges, Timothy J.

2014-10-24

Recent advances in supercomputers and parallel solver techniques have enabled users to run large simulations problems using millions of processors. Techniques for multiphysics nuclear reactor core simulations are under active development in several countries. Most of these techniques require large unstructured meshes that can be hard to generate in a standalone desktop computers because of high memory requirements, limited processing power, and other complexities. We have previously reported on a hierarchical lattice-based approach for generating reactor core meshes. Here, we describe efforts to exploit coarse-grained parallelism during reactor assembly and reactor core mesh generation processes. We highlight several reactor coremore » examples including a very high temperature reactor, a full-core model of the Korean MONJU reactor, a ¼ pressurized water reactor core, the fast reactor Experimental Breeder Reactor-II core with a XX09 assembly, and an advanced breeder test reactor core. The times required to generate large mesh models, along with speedups obtained from running these problems in parallel, are reported. A graphical user interface to the tools described here has also been developed.« less

Compression of an Applied Bz field by a z-pinch onto a Tamped DT Fiber for Inertial Confinement Fusion

NASA Astrophysics Data System (ADS)

Nash, Tom

2009-11-01

Simulations of a z-pinch compressing an applied 100 kG Bz field onto an on-axis DT fiber tamped with beryllium show the field reaching over 100 MG in the tamp, sufficient to confine DT alpha particles and to form a thermal barrier. The barrier allows the DT plasma to burn at a rho*r value as low as 0.045 g/cm^2, and at temperatures over 50 keV for a 63 MA drive current. Driving currents between 21 and 63 MA are considered with cryogenic DT fiber diameters between 600 μm and 1.6 mm. Pinch implosion times are 120 ns with a peak implosion velocity of 35 cm/μs. 1D simulations are of a foil pinch, but for improved stability we propose a nested wire-array. Simulated fusion yields with this system scale as the sixth power of the current, with burn fractions scaling as the fourth power of the current. At 63 MA the simulated yield is 521 MJ from 4.2 mg/cm of DT with a 37% burn fraction at a rho*r of only 0.18 g/cm^2.

Spectroscopic and Kinetic Characterization of Peroxidase-Like π-Cation Radical Pinch-Porphyrin-Iron(III) Reaction Intermediate Models of Peroxidase Enzymes.

PubMed

Hernández Anzaldo, Samuel; Arroyo Abad, Uriel; León García, Armando; Ramírez Rosales, Daniel; Zamorano Ulloa, Rafael; Reyes Ortega, Yasmi

2016-06-27

The spectroscopic and kinetic characterization of two intermediates from the H₂O₂ oxidation of three dimethyl ester [(proto), (meso), (deuteroporphyrinato) (picdien)]Fe(III) complexes ([FePPPic], [FeMPPic] and [FeDPPic], respectively) pinch-porphyrin peroxidase enzyme models, with s = 5/2 and 3/2 Fe(III) quantum mixed spin (qms) ground states is described herein. The kinetic study by UV/Vis at λmax = 465 nm showed two different types of kinetics during the oxidation process in the guaiacol test for peroxidases (1-3 + guaiacol + H₂O₂ → oxidation guaiacol products). The first intermediate was observed during the first 24 s of the reaction. When the reaction conditions were changed to higher concentration of pinch-porphyrins and hydrogen peroxide only one type of kinetics was observed. Next, the reaction was performed only between pinch-porphyrins-Fe(III) and H₂O₂, resulting in only two types of kinetics that were developed during the first 0-4 s. After this time a self-oxidation process was observed. Our hypotheses state that the formation of the π-cation radicals, reaction intermediates of the pinch-porphyrin-Fe(III) family with the ligand picdien [N,N'-bis-pyridin-2-ylmethyl-propane-1,3-diamine], occurred with unique kinetics that are different from the overall process and was involved in the oxidation pathway. UV-Vis, ¹H-NMR and ESR spectra confirmed the formation of such intermediates. The results in this paper highlight the link between different spectroscopic techniques that positively depict the kinetic traits of artificial compounds with enzyme-like activity.

Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions.

PubMed

Chattaraj, Pratim K; Ayers, Paul W; Melin, Junia

2007-08-07

Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition.

Residual stress control and design of next-generation ultra-hard gear steels

NASA Astrophysics Data System (ADS)

Qian, Yana

In high power density transmission systems, Ni-Co secondary hardening steels have shown great potential for next-generation gear applications due to their excellent strength, toughness and superior fatigue performance. Study of residual stress generation and evolution in Ferrium C61 and C67 gear steels revealed that shot peening and laser peening processes effectively produce desired beneficial residual stress in the steels for enhanced fatigue performance. Surface residual stress levels of -1.4GPa and -1.5GPa were achieved in shot peened C61 and laser peened C67, respectively, without introducing large surface roughness or defects. Higher compressive residual stress is expected in C67 according to a demonstrated correlation between attainable residual stress and material hardness. Due to the lack of appropriate shot media, dual laser peening is proposed for future peening optimization in C67. A novel non-destructive synchrotron radiation technique was implemented and applied for the first time for residual stress distribution analysis in gear steels with large composition and property gradients. Observed substantial residual stress redistribution and material microstructure change during the rolling contact fatigue screening test with extremely high 5.4GPa load indicates the unsuitability of the test as a fatigue life predictor. To exploit benefits of higher case hardness and associated residual stress, a new material and process (CryoForm70) aiming at 70Rc surface hardness was designed utilizing the systems approach based on thermodynamics and secondary hardening mechanisms. The composition design was first validated by the excellent agreement between experimental and theoretical core martensite start temperature in the prototype. A novel cryogenic deformation process was concurrently designed to increase the case martensite volume fraction from 76% to 92% for enhanced strengthening efficiency and surface hardness. High temperature vacuum carburizing was

History of HERMES III diode to z-pinch breakthrough and beyond :

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanford, Thomas Williamlou.

HERMES III and Z are two flagship accelerators of Sandias pulsed-power program developed to generate intense -ray fields for the study of nuclear radiation effects, and to explore high energy-density physics (including the production of intense x-ray fields for Inertia Confinement Fusion [ICF]), respectively. A diode at the exit of HERMES III converts its 20-MeV electron beam into -rays. In contrast, at the center of Z, a z-pinch is used to convert its 20-MA current into an intense burst of x-rays. Here the history of how the HERMES III diode emerged from theoretical considerations to actual hardware is discussed. Next,more » the reverse process of how the experimental discovery of wire-array stabilization in a z-pinch, led to a better theory of wirearray implosions and its application to one of the ICF concepts on Z--the DH (Dynamic Hohlraum) is reviewed. Lastly, the report concludes with how the unexpected axial radiation asymmetry measured in the DH is understood. The first discussion illustrates the evolution of physics from theory-to-observationto- refinement. The second two illustrate the reverse process of observationto- theory-to refinement. The histories are discussed through the vehicle of my research at Sandia, illustrating the unique environment Sandia provides for personal growth and development into a scientific leader.« less

Recombination-pumped XUV lasing in capillary discharges and dynamic z-pinches

NASA Astrophysics Data System (ADS)

Pöckl, M.; Hebenstreit, M.; Fertner, R.; Neger, T.; Aumayr, F.

1996-08-01

A fully time-dependent collisional - radiative model is employed to calculate relevant population densities in a recombining carbon/hydrogen z-pinch plasma. In particular, the dependence of the small signal gain G on the maximum electron temperature and cooling rate, as well as the influence of Lyman-0022-3727/29/8/005/img8 reabsorption, are studied. Although in conditions typical for dynamic z-pinches the maximum electron temperature and cooling rates would, in principle, be sufficiently high, gain on the Balmer-0022-3727/29/8/005/img8 transition is strongly reduced by Lyman-0022-3727/29/8/005/img8 reabsorption. In order to investigate vacuum spark capillary discharges, the system of rate equations is coupled with balance equations of the plasma energy and the total number of heavy particles. The resulting set of equations is solved self-consistently. Results are presented that show the systematic dependence of the small signal gain on electrical input power, wall material, and capillary geometry. High gain coefficients 0022-3727/29/8/005/img11 could be achieved by modelling high-voltage discharges with short ringing periods through capillaries containing boron or carbon. While the maximum achievable gain coefficient for lithium is rather poor 0022-3727/29/8/005/img12 the duration of population inversion would be long enough (a few tens of nanoseconds) to make multi-pass operation possible.

The application of high-speed photography in z-pinch high-temperature plasma diagnostics

NASA Astrophysics Data System (ADS)

Wang, Kui-lu; Qiu, Meng-tong; Hei, Dong-wei

2007-01-01

This invited paper is presented to discuss the application of high speed photography in z-pinch high temperature plasma diagnostics in recent years in Northwest Institute of Nuclear Technology in concentrative mode. The developments and applications of soft x-ray framing camera, soft x-ray curved crystal spectrometer, optical framing camera, ultraviolet four-frame framing camera and ultraviolet-visible spectrometer are introduced.

Stability of a diffuse linear pinch with axial boundaries

NASA Technical Reports Server (NTRS)

Einaudi, G.; Van Hoven, G.

1981-01-01

A formulation of the stability behavior of a finite-length pinch is presented. A general initial perturbation is expressed as a uniformly convergent sum over a complete discrete k set. A variational calculation is then performed, based on the energy principle, in which the end-boundary conditions appear as constraints. The requisite Lagrange multipliers mutually couple the elemental periodic excitations. The resulting extended form of delta-W still admits a proper second-variation treatment so that the minimization and stability considerations of Newcomb remain applicable. Comparison theorems are discussed as is the relevance of this end-effect model to the stability of solar coronal loops.

Analytic model to estimate thermonuclear neutron yield in z-pinches using the magnetic Noh problem

NASA Astrophysics Data System (ADS)

Allen, Robert C.

The objective was to build a model which could be used to estimate neutron yield in pulsed z-pinch experiments, benchmark future z-pinch simulation tools and to assist scaling for breakeven systems. To accomplish this, a recent solution to the magnetic Noh problem was utilized which incorporates a self-similar solution with cylindrical symmetry and azimuthal magnetic field (Velikovich, 2012). The self-similar solution provides the conditions needed to calculate the time dependent implosion dynamics from which batch burn is assumed and used to calculate neutron yield. The solution to the model is presented. The ion densities and time scales fix the initial mass and implosion velocity, providing estimates of the experimental results given specific initial conditions. Agreement is shown with experimental data (Coverdale, 2007). A parameter sweep was done to find the neutron yield, implosion velocity and gain for a range of densities and time scales for DD reactions and a curve fit was done to predict the scaling as a function of preshock conditions.

X-ray source characterization of aluminum X-pinch plasmas driven by the 0. 5 TW LION accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qi, N.; Hammer, D.A.; Kalantar, D.H.

1989-12-01

Recent experiments at Cornell have been performed to investigate X-pinch plasmas as intense x-ray sources which might be used to pump resonant photoexcitation lasers. Crossed Al wires have been driven by up to 600 kA current for 40 ns. High density bright spots are observed at the crossing point(s). Various diagnostics were used to characterize the X-pinch plasmas as a function of initial mass loading for several specific wire configurations. The optimum mass loading for different ionization stages of Al, and the total x-ray energy yields, which are on the order of hundreds of Joules, were examined. Estimates of plasmamore » density, {similar to}10{sup 20} cm{sup {minus}3}, and temperature, about 400 eV, were obtained.« less

Dynamics of deformation and pinch-off of a migrating compound droplet in a tube

NASA Astrophysics Data System (ADS)

Borthakur, Manash Pratim; Biswas, Gautam; Bandyopadhyay, Dipankar

2018-04-01

A computational fluid dynamic investigation has been carried out to study the dynamics of a moving compound droplet inside a tube. The motions associated with such a droplet is uncovered by solving the axisymmetric Navier-Stokes equations in which the spatiotemporal evolution of a pair of twin-deformable interfaces has been tracked employing the volume-of-fluid approach. The deformations at the interfaces and their subsequent dynamics are found to be stimulated by the subtle interplay between the capillary and viscous forces. The simulations uncover that when a compound drop composed of concentric inner and outer interfaces migrates inside a tube, initially in the unsteady domain of evolution, the inner drop shifts away from the concentric position to reach a morphology of constant eccentricity at the steady state. The coupled motions of the droplets in the unsteady regime causes a continuous deformation of the inner and outer interfaces to obtain a configuration with a (an) prolate (oblate) shaped outer (inner) interface. The magnitudes of capillary number and viscosity ratio are found to have significant influence on the temporal evolution of the interfacial deformations as well as the eccentricity of the droplets. Further, the simulations uncover that, following the asymmetric deformation of the interfaces, the migrating compound droplet can undergo an uncommon breakup stimulated by a rather irregular pinch-off of the outer shell. The breakup is found to initiate with the thinning of the outer shell followed by the pinch-off. Interestingly, the kinetics of the thinning of outer shell is found to follow two distinct power-law regimes—a swiftly thinning stage at the onset followed by a rate limiting stage before pinch-off, which eventually leads to the uncommon breakup of the migrating compound droplets.

LETTER TO THE EDITOR: Anisotropy of ion temperature in a reversed-field-pinch plasma

NASA Astrophysics Data System (ADS)

Sasaki, K.; Hörling, P.; Fall, T.; Brzozowski, J. H.; Brunsell, P.; Hokin, S.; Tennfors, E.; Sallander, J.; Drake, J. R.; Inoue, N.; Morikawa, J.; Ogawa, Y.; Yoshida, Z.

1997-03-01

Anomalous heating of ions has been observed in the EXTRAP-T2 reversed-field-pinch (RFP) plasma. Ions are heated primarily in the parallel direction (with respect to the magnetic field), resulting in an appreciable anisotropy of the ion temperature. This observation suggests that the magnetohydrodynamic fluctuations are dissipated primarily by the ion viscosity.

Evaluating the Usability of Pinchigator, a system for Navigating Virtual Worlds using Pinch Gloves

NASA Technical Reports Server (NTRS)

Hamilton, George S.; Brookman, Stephen; Dumas, Joseph D. II; Tilghman, Neal

2003-01-01

Appropriate design of two dimensional user interfaces (2D U/I) utilizing the well known WIMP (Window, Icon, Menu, Pointing device) environment for computer software is well studied and guidance can be found in several standards. Three-dimensional U/I design is not nearly so mature as 2D U/I, and standards bodies have not reached consensus on what makes a usable interface. This is especially true when the tools for interacting with the virtual environment may include stereo viewing, real time trackers and pinch gloves instead of just a mouse & keyboard. Over the last several years the authors have created a 3D U/I system dubbed Pinchigator for navigating virtual worlds based on the dVise dV/Mockup visualization software, Fakespace Pinch Gloves and Pohlemus trackers. The current work is to test the usability of the system on several virtual worlds, suggest improvements to increase Pinchigator s usability, and then to generalize about what was learned and how those lessons might be applied to improve other 3D U/I systems.

Solar Hard X-ray Observations with NuSTAR

NASA Astrophysics Data System (ADS)

Smith, David M.; Krucker, S.; Hudson, H. S.; Hurford, G. J.; White, S. M.; Mewaldt, R. A.; Stern, D.; Grefenstette, B. W.; Harrison, F. A.

2011-05-01

High-sensitivity imaging of coronal hard X-rays allows detection of freshly accelerated nonthermal electrons at the acceleration site. A few such observations have been made with Yohkoh and RHESSI, but a leap in sensitivity could help pin down the time, place, and manner of reconnection. In 2012, the Nuclear Spectroscopic Telescope Array (NuSTAR), a NASA Small Explorer for high energy astrophysics that uses grazing-incidence optics to focus X-rays up to 80 keV, will be launched. NuSTAR is capable of solar pointing, and three weeks will be dedicated to solar observing during the baseline two-year mission. NuSTAR will be 200 times more sensitive than RHESSI in the hard X-ray band. This will allow the following new observations, among others: 1) Extrapolation of the micro/nanoflare distribution by two orders of magnitude down in flux 2) Search for hard X-rays from network nanoflares (soft X-ray bright points) and evaluation of their role in coronal heating 3) Discovery of hard X-ray bremsstrahlung from the electron beams driving type III radio bursts, and measurement of their electron spectrum 4) Hard X-ray studies of polar soft X-ray jets and impulsive solar energetic particle events at the edge of coronal holes, and comparison of these events with observations of 3He and other particles in interplanetary space 5) Study of coronal bremsstrahlung from particles accelerated by coronal mass ejections as they are first launched 6) Study of particles at the coronal reconnection site when flare footpoints are occulted; and 7) Search for hypothetical axion particles created in the solar core via the hard X-ray signal from their conversion to X-rays in the coronal magnetic field. NuSTAR will also serve as a pathfinder for a future dedicated space mission with enhanced capabilities, such as a satellite version of the FOXSI sounding rocket.

Mapping coexistence lines via free-energy extrapolation: application to order-disorder phase transitions of hard-core mixtures.

PubMed

Escobedo, Fernando A

2014-03-07

In this work, a variant of the Gibbs-Duhem integration (GDI) method is proposed to trace phase coexistence lines that combines some of the advantages of the original GDI methods such as robustness in handling large system sizes, with the ability of histogram-based methods (but without using histograms) to estimate free-energies and hence avoid the need of on-the-fly corrector schemes. This is done by fitting to an appropriate polynomial function not the coexistence curve itself (as in GDI schemes) but the underlying free-energy function of each phase. The availability of a free-energy model allows the post-processing of the simulated data to obtain improved estimates of the coexistence line. The proposed method is used to elucidate the phase behavior for two non-trivial hard-core mixtures: a binary blend of spheres and cubes and a system of size-polydisperse cubes. The relative size of the spheres and cubes in the first mixture is chosen such that the resulting eutectic pressure-composition phase diagram is nearly symmetric in that the maximum solubility of cubes in the sphere-rich solid (∼20%) is comparable to the maximum solubility of spheres in the cube-rich solid. In the polydisperse cube system, the solid-liquid coexistence line is mapped out for an imposed Gaussian activity distribution, which produces near-Gaussian particle-size distributions in each phase. A terminal polydispersity of 11.3% is found, beyond which the cubic solid phase would not be stable, and near which significant size fractionation between the solid and isotropic phases is predicted.

Acceleration of Hydrogen Ions up to 30 MeV and Generation of 3 × 1012 Neutrons in Megaampere Deuterium Gas-Puff Z-Pinch

NASA Astrophysics Data System (ADS)

Klir, D.; Cikhardt, J.; Kravarik, J.; Kubes, P.; Rezac, K.; Sila, O.; Shishlov, A.; Cherdizov, R.; Fursov, F.; Kokshenev, V.; Kovalchuk, B.; Kurmaev, N.; Labetsky, A.; Ratakhin, N.; Orcikova, H.; Turek, K.

2013-10-01

Fusion neutrons were produced with a deuterium gas-puff z-pinch on the GIT-12 generator at the Institute of High Current Electronics in Tomsk. The peak neutron yield from DD reactions reached Yn = (2 . 9 +/- 0 . 3) ×1012 at 100 μg/cm linear mass density of deuterium, 700 ns implosion time and 2.7 MA current. Such a neutron yield means that the scaling law of deuterium z-pinches Yn ~I4 was extended to 3 MA currents. The further increase of neutron yields up to (3 . 7 +/- 0 . 4) ×1012 was achieved by placing a deuterated polyethylene catcher onto the axis. Maximum neutron energies of 15 and 22 MeV were observed by radial and axial nToF detectors, respectively. A stack of CR-39 track detectors showed up to 40 MeV deuterons (or 30 MeV protons) on the z-pinch axis. Since the energy input into plasmas was 70 kJ, the number of DD neutrons per one joule of stored plasma energy exceeded the value of 5 ×107 . This value implies that deuterium gas-puff z-pinches belong to the most efficient plasma-based sources of DD neutrons. This work was partially supported by the GACR grant No. P205/12/0454 and by the RFBR research project No. 13-08-00479-a.

Associations of work activities requiring pinch or hand grip or exposure to hand-arm vibration with finger and wrist osteoarthritis: a meta-analysis.

PubMed

Hammer, Paula E C; Shiri, Rahman; Kryger, Ann I; Kirkeskov, Lilli; Bonde, Jens Peter

2014-03-01

We systematically reviewed the epidemiologic evidence linking finger and wrist osteoarthritis (OA) with work activities requiring pinch or hand grip or exposure to hand-arm vibration (HAV). PubMed and Embase databases were searched up to June 2013. We selected studies assessing the associations of radiographic diagnosed finger and/or wrist joint OA with work activities involving pinch or hand grip or exposure to HAV. We used specific criteria to evaluate completeness of reporting, potential confounding, and bias. Pooled odds ratios (OR) were computed using random-effects meta-analyses. Of the 19 studies included, 17 were cross-sectional, 1 was a prospective cohort, and 1 a case-control study. The meta-analyses of studies that controlled their estimates for at least age and gender showed the associations of pinch grip work with proximal interphalangeal joint [OR 1.56, 95% confidence interval (95% CI) 1.09-2.23] and the first carpometacarpal joint OA (OR 2.10, 95% CI 1.06-4.17), but not with distal interphalangeal, metacarpalphalangeal, or wrist joints OA. Hand grip work and exposure to HAV were not associated with any finger or wrist OA. Epidemiological studies provide limited evidence that pinch grip may increase the risk of wrist or finger OA, but causal relation cannot be resolved because of cross-sectional designs and inadequate characterization of biomechanical strain to the hand and wrist.

Investigating plasma viscosity with fast framing photography in the ZaP-HD Flow Z-Pinch experiment

NASA Astrophysics Data System (ADS)

Weed, Jonathan Robert

The ZaP-HD Flow Z-Pinch experiment investigates the stabilizing effect of sheared axial flows while scaling toward a high-energy-density laboratory plasma (HEDLP > 100 GPa). Stabilizing flows may persist until viscous forces dissipate a sheared flow profile. Plasma viscosity is investigated by measuring scale lengths in turbulence intentionally introduced in the plasma flow. A boron nitride turbulence-tripping probe excites small scale length turbulence in the plasma, and fast framing optical cameras are used to study time-evolved turbulent structures and viscous dissipation. A Hadland Imacon 790 fast framing camera is modified for digital image capture, but features insufficient resolution to study turbulent structures. A Shimadzu HPV-X camera captures the evolution of turbulent structures with great spatial and temporal resolution, but is unable to resolve the anticipated Kolmogorov scale in ZaP-HD as predicted by a simplified pinch model.

Improved diamond coring bits developed for dry and chip-flush drilling

NASA Technical Reports Server (NTRS)

Decker, W. E.; Hampe, W. R.; Hampton, W. H.; Simon, A. B.

1971-01-01

Two rotary diamond bit designs, one operating with a chip-flushing fluid, the second including auger section to remove drilled chips, enhance usefulness of tool for exploratory and industrial core-drilling of hard, abrasive mineral deposits and structural masonry.

Computing with volatile memristors: an application of non-pinched hysteresis

NASA Astrophysics Data System (ADS)

Pershin, Y. V.; Shevchenko, S. N.

2017-02-01

The possibility of in-memory computing with volatile memristive devices, namely, memristors requiring a power source to sustain their memory, is demonstrated theoretically. We have adopted a hysteretic graphene-based field emission structure as a prototype of a volatile memristor, which is characterized by a non-pinched hysteresis loop. A memristive model of the structure is developed and used to simulate a polymorphic circuit implementing stateful logic gates, such as the material implication. Specific regions of parameter space realizing useful logic functions are identified. Our results are applicable to other realizations of volatile memory devices, such as certain NEMS switches.

Effect of anode shape on correlation of neutron emission with pinch energy for a 2.7 kJ Mather-type plasma focus device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hussain, S. S.; Murtaza, Ghulam; Zakaullah, M.

Correlation of neutron emission with pinch energy for a Mather-type plasma focus energized by a single capacitor 12.5 muF, 21 kV (2.7 kJ) is investigated by employing time resolved and time integrated detectors for two different anode shapes. The maximum average neutron yield of about 1.3x10{sup 8} per shot is recorded with cylindrical anode, that increases to 1.6x10{sup 8} per shot for tapered anode. At optimum pressure the input energy converted to pinch energy is about 24% for cylindrical anode as compared to 36% for tapered anode. It is found that the tapered anode enhances neutron flux about 25+-5% bothmore » in axial and radial directions and also broadens the pressure range for neutron emission as well as pinch energy. The neutron yield and optimum gas filling pressures are found strongly dependent on the anode shape.« less

Charger 1: A New Facility for Z-Pinch Research

NASA Technical Reports Server (NTRS)

Taylor, Brian; Cassibry, Jason; Cortez, Ross; Doughty, Glen; Adams, Robert; DeCicco, Anthony

2017-01-01

Charger 1 is a multipurpose pulsed power laboratory located on Redstone Arsenal, with a focus on fusion propulsion relevant experiments involving testing z-pinch diodes, pulsed magnetic nozzle and other related physics experiments. UAH and its team of pulsed power researchers are investigating ways to increase and optimize fusion production from Charger 1. Currently the team has reached high-power testing. Due to the unique safety issues related to high power operations the UAH/MSFC team has slowed repair efforts to develop safety and operations protocols. The facility is expected to be operational by the time DZP 2017 convenes. Charger 1 began life as the Decade Module 2, an experimental prototype built to prove the Decade Quad pinch configuration. The system was donated to UAH by the Defense Threat Reduction Agency (DRTA) in 2012. For the past 5 years a UAH/MSFC/Boeing team has worked to refurbish, assemble and test the system. With completion of high power testing in summer 2017 Charger 1 will become operational for experimentation. Charger 1 utilizes a Marx Bank of 72 100-kV capacitors that are charged in parallel and discharged in series. The Marx output is compressed to a pulse width of approximately 200 ns via a pulse forming network of 32 coaxial stainless steel tubes using water as a dielectric. After pulse compression a set of SF6 switches are triggered, allowing the wave front to propagate through the output line to the load. Charger 1 is capable of storing 572-kJ of energy and time compressing discharge to less than 250 ns discharge time producing a discharge of about 1 TW of discharge with 1 MV and 1 MA peak voltage and current, respectively. This capability will be used to study energy yield scaling and physics from solid density target as applied to advanced propulsion research.

Liquid crystalline phase behavior in systems of hard-sphere chains

NASA Astrophysics Data System (ADS)

Williamson, Dave C.; Jackson, George

1998-06-01

A study of the liquid crystalline phase transitions in a system of hard-sphere chains is presented. The chains comprise m=7 tangentially bonded hard-sphere segments in a linear conformation (LHSC). The isothermal-isobaric Monte Carlo simulation technique is used to obtain the equation of state of the system both by compressing the isotropic (I) liquid and by expanding the solid (K). As well as the usual isotropic and solid phases, nematic and smectic-A liquid crystalline states are seen. A large degree of hysteresis is found in the neighborhood of the I-N transition. The results for the rigid LHSC system were compared with existing data for the corresponding semiflexible hard-sphere chains (FHSC): the flexibility has a large destabilizing effect on the nematic phase and consequently it postpones the I-N transition. The results of the simulations are also compared with rescaled Onsager theories for the I-N transition. It is rather surprising to find that the Parsons approach, which has been so successful for other hard-core models such as spherocylinders and ellipsoids, gives very poor results. The related approach of Vega and Lago gives a good description of the I-N phase transition. The procedure of Vega and Lago, as with all two-body resummations of the Onsager theory, only gives a qualitative description of the nematic order.

A non-LTE kinetic model for quick analysis of K-shell spectra from Z-pinch plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, J., E-mail: s.duan@163.com; Huang, X. B., E-mail: s.duan@163.com; Cai, H. C., E-mail: s.duan@163.com

Analyzing and modeling K-shell spectra emitted by low-to moderate-atomic number plasma is a useful and effective way to retrieve temperature density of z-pinch plasmas. In this paper, a non-LTE population kinetic model for quick analysis of K-shell spectra was proposed. The model contains ionization stages from bare nucleus to neutral atoms and includes all the important atomic processes. In the present form of the model, the plasma is assumed to be both optically thin and homogeneous with constant temperature and density, and only steady-state situation is considered. According to the detailed calculations for aluminum plasmas, contours of ratios of certainmore » K-shell lines in electron temperature and density plane as well as typical synthesized spectra were presented and discussed. The usefulness of the model is demonstrated by analyzing the spectrum from a neon gas-puff Z-pinch experiment performed on a 1 MA pulsed-power accelerator.« less

PINCH WELD TESTING TO SUPPORT CHANGE IN MANUFACTURING OIL AT THE KCP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korinko, P; David Maxwell, D

2008-02-28

This task supports the change from an oil mixture termed 50:50 oil (an equal parts mixture of Milpro 634 and Pennex N47) to a new oil mixture (Castrol Illocut 334). This change was necessitated by a KCP vendor no longer supplying the Pennex N47 component of the 50-50. In order to continue production of machined parts, a detailed process was followed to ensure that high quality parts could be manufactured and that the cutting oil selected would provide acceptable human performance characteristics, e.g., skin irritability, smell, etc. A prime consideration in changing the oil was that no apparent change inmore » the pinch weldability of the fill stems fabricated using the new oil and process parameters, if any, be observed. A two part approach, as detailed in the plan shown in Appendix B, was used to qualify the effect of the process on pinch weld characteristics. In the first phase, ref. 1., the weld parameter window was defined using fill stems made from 304L, 21-6-9, and 316 stainless steel. These weld conditions were then subsequently used for the Castrol Illocut 334 machined fill stems. The results of this activity are reported in this document. A follow-on task of welding in the facility was requested by one of the design agencies and this will be completed and reported separately.« less

Using a Z-pinch precursor plasma to produce a cylindrical, hotspot ignition, ICF

NASA Astrophysics Data System (ADS)

Chittenden, Jeremy

2005-10-01

We show that if the same precursor plasma that exists in metal wire arrays can be generated with a Deuterium-Tritium plasma then this precursor provides an ideal target for a cylindrical magneto-inertial ICF scheme. The precursor is generated from a fraction of the mass of the array which arrives on the axis early in time and remains confined at high density by the inertia of further material bombarding the axis. Later on, the main implosion of the DT Z-pinch produces a dense, low temperature shell which compressively heats the precursor target to high temperatures and tamps its expansion. The azimuthal magnetic field in the hotspot is sufficient to reduce the Larmor radius for the alpha particles to much less than the hotspot size, which dramatically reduces the ρR required for ignition. A computational analysis of this approach is presented, including a study of the thermonuclear burn wave propagation. The robustness of the scheme with respect to instabilities, confinement time and drive parameters is examined. The results indicate that a high energy gain can be achieved using Z-pinches with 50-100 MA currents and a few hundred nanosecond rise-times. This work was partially supported by the U.S. Department of Energy through cooperative agreement DE-FC03-02NA00057.

Staged Z-pinch Experiments at the 1MA Zebra pulsed-power generator: Neutron measurements

NASA Astrophysics Data System (ADS)

Ruskov, Emil; Darling, T.; Glebov, V.; Wessel, F. J.; Anderson, A.; Beg, F.; Conti, F.; Covington, A.; Dutra, E.; Narkis, J.; Rahman, H.; Ross, M.; Valenzuela, J.

2017-10-01

We report on neutron measurements from the latest Staged Z-pinch experiments at the 1MA Zebra pulsed-power generator. In these experiments a hollow shell of argon or krypton gas liner, injected between the 1 cm anode-cathode gap, compresses a deuterium plasma target of varying density. Axial magnetic field Bz <= 2 kGs, applied throughout the pinch region, stabilizes the Rayleigh-Taylor instability. The standard silver activation diagnostics and 4 plastic scintillator neutron Time of Flight (nTOF) detectors are augmented with a large area ( 1400 cm2) liquid scintillator detector to which fast gatedPhotek photomultipliers are attached. Sample data from these neutron diagnostics systems is presented. Consistently high neutron yields YDD >109 are measured, with highest yield of 2.6 ×109 . A pair of horizontally and vertically placed plastic scintillator nTOFs suggest isotropic i.e. thermonuclear origin of the neutrons produced. nTOF data from the liquid scintillator detector was cross-calibrated with the silver activation detector, and can be used for accurate calculation of the neutron yield. Funded by the Advanced Research Projects Agency - Energy, under Grant Number DE-AR0000569.

Effects of geometry and fluid elasticity during polymeric droplet pinch-off in microfluidic environments

NASA Astrophysics Data System (ADS)

Steinhaus, Ben; Shen, Amy; Sureshkumar, Radhakrishna

2006-11-01

We investigate the effects of fluid elasticity and channel geometry on polymeric droplet pinch-off by performing systematic experiments using viscoelastic polymer solutions which possess practically shear rate-independent viscosity (Boger fluids). Four different geometric sizes (width and depth are scaled up proportionally at the ratio of 0.5, 1, 2, 20) are used to study the effect of the length scale, which in turn influences the ratio of elastic to viscous forces as well as the Rayleigh time scale associated with the interfacial instability of a cylindrical column of liquid. We observe a power law relationship between the dimensionless (scaled with respect to the Rayleigh time scale) capillary pinch-off time, T, and the elasticity number, E, defined as the ratio of the fluid relaxation time to the time scale of viscous diffusion. In general, T increases dramatically with increasing E. The inhibition of ``bead-on-a-string'' formation is observed for flows with effective Deborah number, De, defined as the ratio of the fluid relaxation time to the Rayleigh time scale becomes greater than 10. For sufficiently large values of De, the Rayleigh instability may be modified substantially by fluid elasticity.

Simulation of K-α Emission from Highly Charged Cu ions for Pinches on ZR

NASA Astrophysics Data System (ADS)

Dasgupta, A.; Giuliani, J. L.; Clark, R. W.; Ouart, N. D.; Jones, B.; Ampleford, D. J.

2012-10-01

Recent spectral data of Cu shots Z1975 and Z2122 from Sandia's ZR machine are believed to show strong K-α emissions. As these K-α lines provide good diagnostics, a detailed spectral model will be developed to investigate these line emissions for analyzing the data. In a Z pinch plasma, K-α emission can occur due to e-beams, hot electrons at the tail of a Maxwellian and also pumping from hot photons emitted near the axis. K-α emission that originates from collisional processes involving hot electrons in the final phase of the pinching plasmas are associated with radiationless electron capture, inner-shell electron collisional excitation and ionization. K-α lines from various ionization stages of various materials such as Fe, Cr, Ni, and Mn were also observed in the ZR data. Contributions from ions with strong K-α transitions will be included for this study which is a preliminary attempt to investigate Cu K-α lines due to hot electrons and photons. Photo-pumped K-α emission from an outer shell is spatially distinguishable from that produced by e-beam on axis.

Lower Bound on the Mean Square Displacement of Particles in the Hard Disk Model

NASA Astrophysics Data System (ADS)

Richthammer, Thomas

2016-08-01

The hard disk model is a 2D Gibbsian process of particles interacting via pure hard core repulsion. At high particle density the model is believed to show orientational order, however, it is known not to exhibit positional order. Here we investigate to what extent particle positions may fluctuate. We consider a finite volume version of the model in a box of dimensions 2 n × 2 n with arbitrary boundary configuration, and we show that the mean square displacement of particles near the center of the box is bounded from below by c log n. The result generalizes to a large class of models with fairly arbitrary interaction.

Energy required to pinch a DNA plectoneme

NASA Astrophysics Data System (ADS)

Barde, Céline; Destainville, Nicolas; Manghi, Manoel

2018-03-01

DNA supercoiling plays an important role from a biological point of view. One of its consequences at the supramolecular level is the formation of DNA superhelices named plectonemes. Normally separated by a distance on the order of 10 nm, the two opposite double strands of a DNA plectoneme must be brought closer if a protein or protein complex implicated in genetic regulation is to be bound simultaneously to both strands, as if the plectoneme was locally pinched. We propose an analytic calculation of the energetic barrier, of elastic nature, required to bring closer the two loci situated on the opposed double strands. We examine how this energy barrier scales with the DNA supercoiling. For physically relevant values of elastic parameters and of supercoiling density, we show that the energy barrier is in the kBT range under physiological conditions, thus demonstrating that the limiting step to loci encounter is more likely the preceding plectoneme slithering bringing the two loci side by side.

Proposal to Produce Novel, Transparent Radiation Hard Low Refractive Index

DTIC Science & Technology

1994-02-09

or ainy nht.at NX ftU 1.AECY USE a EP....3RFPfT TYP’E AND DATES~ COV-ERED-- 4. TITLE AND SUBTITLE . . FjUNDING NUMBERS PROPOSAL TO PRODUCE NOVEL...cladding use . our research resulted in identifying a radiation hard, low refractive index polymer, poly (heptafluorobutyl methacrylate), P(MFBM) as the best...candidate for a novel ~. cladding material. P(HFB) has a refractive index of 1.387. When used to clada styrene core, the theoretical light propagation

Hard sphere perturbation theory of dense fluids with singular perturbation

NASA Astrophysics Data System (ADS)

Mon, K. K.

2000-02-01

Hard sphere perturbation theories (HSPT) played a significant role in the fundamental understanding of fluids and continues to be a popular method in a wide range of applications. The possibility of difficulty with singular perturbation for some classical soft core model fluids appears to have been overlooked or ignored in the literature. We address this issue in this short note and show by analysis that a region of phase space has been neglected in the standard application of HSPT involving singular perturbation.

JPIC-Rad-Hard JPEG2000 Image Compression ASIC

NASA Astrophysics Data System (ADS)

Zervas, Nikos; Ginosar, Ran; Broyde, Amitai; Alon, Dov

2010-08-01

JPIC is a rad-hard high-performance image compression ASIC for the aerospace market. JPIC implements tier 1 of the ISO/IEC 15444-1 JPEG2000 (a.k.a. J2K) image compression standard [1] as well as the post compression rate-distortion algorithm, which is part of tier 2 coding. A modular architecture enables employing a single JPIC or multiple coordinated JPIC units. JPIC is designed to support wide data sources of imager in optical, panchromatic and multi-spectral space and airborne sensors. JPIC has been developed as a collaboration of Alma Technologies S.A. (Greece), MBT/IAI Ltd (Israel) and Ramon Chips Ltd (Israel). MBT IAI defined the system architecture requirements and interfaces, The JPEG2K-E IP core from Alma implements the compression algorithm [2]. Ramon Chips adds SERDES interfaces and host interfaces and integrates the ASIC. MBT has demonstrated the full chip on an FPGA board and created system boards employing multiple JPIC units. The ASIC implementation, based on Ramon Chips' 180nm CMOS RadSafe[TM] RH cell library enables superior radiation hardness.

Advanced spectroscopic analysis of 0.8-1.0-MA Mo x pinches and the influence of plasma electron beams on L-shell spectra of Mo ions.

PubMed

Shlyaptseva, A S; Hansen, S B; Kantsyrev, V L; Fedin, D A; Ouart, N; Fournier, K B; Safronova, U I

2003-02-01

This paper presents a detailed investigation of the temporal, spatial, and spectroscopic properties of L-shell radiation from 0.8 to 1.0 MA Mo x pinches. Time-resolved measurements of x-ray radiation and both time-gated and time-integrated spectra and pinhole images are presented and analyzed. High-current x pinches are found to have complex spatial and temporal structures. A collisional-radiative kinetic model has been developed and used to interpret L-shell Mo spectra. The model includes the ground state of every ionization stage of Mo and detailed structure for the O-, F-, Ne-, Na-, and Mg-like ionization stages. Hot electron beams generated by current-carrying electrons in the x pinch are modeled by a non-Maxwellian electron distribution function and have significant influence on L-shell spectra. The results of 20 Mo x-pinch shots with wire diameters from 24 to 62 microm have been modeled. Overall, the modeled spectra fit the experimental spectra well and indicate for time-integrated spectra electron densities between 2 x 10(21) and 2 x 10(22) cm(-3), electron temperatures between 700 and 850 eV, and hot electron fractions between 3% and 7%. Time-gated spectra exhibit wide variations in temperature and density of plasma hot spots during the same discharge.

The Effect of Driver Rise-Time on Pinch Current and its Impact on Plasma Focus Performance and Neutron Yield

NASA Astrophysics Data System (ADS)

Sears, Jason; Schmidt, Andrea; Link, Anthony; Welch, Dale

2016-10-01

Experiments have suggested that dense plasma focus (DPF) neutron yield increases with faster drivers [Decker NIMP 1986]. Using the particle-in-cell code LSP [Schmidt PRL 2012], we reproduce this trend in a kJ DPF [Ellsworth 2014], and demonstrate how driver rise time is coupled to neutron output. We implement a 2-D model of the plasma focus including self-consistent circuit-driven boundary conditions. Driver capacitance and voltage are varied to modify the current rise time, and anode length is adjusted so that run-in coincides with the peak current. We observe during run down that magnetohydrodynamic (MHD) instabilities of the sheath shed blobs of plasma that remain in the inter-electrode gap during run in. This trailing plasma later acts as a low-inductance restrike path that shunts current from the pinch during maximum compression. While the MHD growth rate increases slightly with driver speed, the shorter anode of the fast driver allows fewer e-foldings and hence reduces the trailing mass between electrodes. As a result, the fast driver postpones parasitic restrikes and maintains peak current through the pinch during maximum compression. The fast driver pinch therefore achieves best simultaneity between its ion beam and peak target density, which maximizes neutron production. Prepared by LLNL under Contract DE-AC52-07NA27344.

Evaluation of HardSys/HardDraw, An Expert System for Electromagnetic Interactions Modelling

DTIC Science & Technology

1993-05-01

interactions ir complex systems. This report gives a description of HardSys/HardDraw and reviews the main concepts used in its design. Various aspects of its ...HardDraw, an expert system for the modelling of electromagnetic interactions in complex systems. It consists of two main components: HardSys and HardDraw...HardSys is the advisor part of the expert system. It is knowledge-based, that is it contains a database of models and properties for various types of

Study of long-range orders of hard-core bosons coupled to cooperative normal modes in two-dimensional lattices

NASA Astrophysics Data System (ADS)

Ghosh, A.; Yarlagadda, S.

2017-09-01

Understanding the microscopic mechanism of coexisting long-range orders (such as lattice supersolidity) in strongly correlated systems is a subject of immense interest. We study the possible manifestations of long-range orders, including lattice-supersolid phases with differently broken symmetry, in a two-dimensional square lattice system of hard-core bosons (HCBs) coupled to archetypal cooperative/coherent normal-mode distortions such as those in perovskites. At strong HCB-phonon coupling, using a duality transformation to map the strong-coupling problem to a weak-coupling one, we obtain an effective Hamiltonian involving nearest-neighbor, next-nearest-neighbor, and next-to-next-nearest-neighbor hoppings and repulsions. Using stochastic series expansion quantum Monte Carlo, we construct the phase diagram of the system. As coupling strength is increased, we find that the system undergoes a first-order quantum phase transition from a superfluid to a checkerboard solid at half-filling and from a superfluid to a diagonal striped solid [with crystalline ordering wave vector Q ⃗=(2 π /3 ,2 π /3 ) or (2 π /3 ,4 π /3 )] at one-third filling without showing any evidence of supersolidity. On tuning the system away from these commensurate fillings, checkerboard supersolid is generated near half-filling whereas a rare diagonal striped supersolid is realized near one-third filling. Interestingly, there is an asymmetry in the extent of supersolidity about one-third filling. Within our framework, we also provide an explanation for the observed checkerboard and stripe formations in La2 -xSrxNiO4 at x =1 /2 and x =1 /3 .

Anomalous transport theory for the reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terry, P.W.; Hegna, C.C; Sovinec, C.R.

1996-09-01

Physically motivated transport models with predictive capabilities and significance beyond the reversed field pinch (RFP) are presented. It is shown that the ambipolar constrained electron heat loss observed in MST can be quantitatively modeled by taking account of the clumping in parallel streaming electrons and the resultant self-consistent interaction with collective modes; that the discrete dynamo process is a relaxation oscillation whose dependence on the tearing instability and profile relaxation physics leads to amplitude and period scaling predictions consistent with experiment; that the Lundquist number scaling in relaxed plasmas driven by magnetic turbulence has a weak S{sup {minus}1/4} scaling; andmore » that radial E{times}B shear flow can lead to large reductions in the edge particle flux with little change in the heat flux, as observed in the RFP and tokamak. 24 refs.« less

Conceptual Design of a Z-Pinch Fusion Propulsion System

NASA Technical Reports Server (NTRS)

Adams, Robert; Polsgrove, Tara; Fincher, Sharon; Fabinski, Leo; Maples, Charlotte; Miernik, Janie; Stratham, Geoffrey; Cassibry, Jason; Cortez, Ross; Turner, Matthew;

Gas Bubble Pinch-off in Viscous and Inviscid Liquids

NASA Astrophysics Data System (ADS)

Taborek, P.

2005-11-01

We have used high-speed video to analyze pinch-off of nitrogen gas bubbles in fluids with a wide range of viscosity. If the external fluid is highly viscous (ηext>100 cP), the radius is proportional to the time before break, τ, and decreases smoothly to zero. If the external fluid has low viscosity (ηext<10 cP), the neck radius scales as &1/2circ; until an instability develops in the gas bubble which causes the neck to rupture and tear apart. Finally, if the viscosity of the external fluid is in an intermediate range, an elongated thread is formed which breaks apart into micron-sized bubbles. 100,000 frame-per-second videos will be presented which illustrate each of these flow regimes.

Optical properties and indentation hardness of thin-film acrylated epoxidized oil

NASA Astrophysics Data System (ADS)

Rahman, Mohammad Syuhaimi Ab.; Shaktur, Khaled Mohamed; Mohammad, Rahmah; Zalikha, Wan Aimi; Nawi, Norwimie; Mohd, Ahmad Faiza

2012-02-01

Epoxy acrylate has been widely used as optical resin for applications such as cladding, the core of a waveguide, and other photonic devices. In this study, sustainable resin from edible oil was used as an alternative to epoxy acrylate. Structural features and the transmission of planar thin-film resin from an ultraviolet-visible spectroscopy (UV-VIS) spectrometer were investigated upon UV exposure. It was found that high transmission still persists for all samples with and without an UV absorber for exposed and unexposed samples. The film was found to absorb strongly below 400 nm. A change in the cut-off wavelength was observed upon exposure. Thin-film hardness and its dynamic indentation in the load-unload mode with different test forces were evaluated. Vickers hardness and the elastic modulus were determined for unacrylated epoxidized soybean oil (ESO) and acrylated epoxidized soybean oil (AESO). It was found that the AESO has a higher Vickers hardness and elastic modulus than those of unacrylated thin film. The Vickers hardness and elastic modulus were found to increase as the applied test force increased. The refractive index, thickness, and modes present were characterized from a spin-coated planar thin film. The refractive index in the transverse electric mode (TE) and transverse magnetic mode (TM) were determined and compared for unacrylated and acrylated epoxidized oil.

A possible mechanism of current termination in a reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagata, A.; Masamune, S.; Arimoto, H.

1989-10-01

A rapid growth of magnetic fluctuations resulting from the {ital m}=1 and {ital m}=2 modes and succeeding stop of rotation of these modes have been found as the precursor phenomena of current termination in the STP-3(M) (Trans. Inst. Elec. Eng. Jpn. {bold 107}-{bold B}, 469 (1987)) reversed field pinch. By deepening the field reversal at the wall, these precursors disappear and the current duration becomes much longer. It is found that sudden current termination is caused by a rapid growth of resistive tearing modes mainly because of nonlinear coupling of the {ital m}=1 mode.

Warming rays in cluster cool cores

NASA Astrophysics Data System (ADS)

Colafrancesco, S.; Marchegiani, P.

2008-06-01

Context: Cosmic rays are confined in the atmospheres of galaxy clusters and, therefore, they can play a crucial role in the heating of their cool cores. Aims: We discuss here the thermal and non-thermal features of a model of cosmic ray heating of cluster cores that can provide a solution to the cooling-flow problems. To this aim, we generalize a model originally proposed by Colafrancesco, Dar & DeRujula (2004) and we show that our model predicts specific correlations between the thermal and non-thermal properties of galaxy clusters and enables various observational tests. Methods: The model reproduces the observed temperature distribution in clusters by using an energy balance condition in which the X-ray energy emitted by clusters is supplied, in a quasi-steady state, by the hadronic cosmic rays, which act as “warming rays” (WRs). The temperature profile of the intracluster (IC) gas is strictly correlated with the pressure distribution of the WRs and, consequently, with the non-thermal emission (radio, hard X-ray and gamma-ray) induced by the interaction of the WRs with the IC gas and the IC magnetic field. Results: The temperature distribution of the IC gas in both cool-core and non cool-core clusters is successfully predicted from the measured IC plasma density distribution. Under this contraint, the WR model is also able to reproduce the thermal and non-thermal pressure distribution in clusters, as well as their radial entropy distribution, as shown by the analysis of three clusters studied in detail: Perseus, A2199 and Hydra. The WR model provides other observable features of galaxy clusters: a correlation of the pressure ratio (WRs to thermal IC gas) with the inner cluster temperature (P_WR/P_th) ˜ (kT_inner)-2/3, a correlation of the gamma-ray luminosity with the inner cluster temperature Lγ ˜ (kT_inner)4/3, a substantial number of cool-core clusters observable with the GLAST-LAT experiment, a surface brightness of radio halos in cool-core clusters

Conversion of electromagnetic energy in Z-pinch process of single planar wire arrays at 1.5 MA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liangping, Wang; Mo, Li; Juanjuan, Han

The electromagnetic energy conversion in the Z-pinch process of single planar wire arrays was studied on Qiangguang generator (1.5 MA, 100 ns). Electrical diagnostics were established to monitor the voltage of the cathode-anode gap and the load current for calculating the electromagnetic energy. Lumped-element circuit model of wire arrays was employed to analyze the electromagnetic energy conversion. Inductance as well as resistance of a wire array during the Z-pinch process was also investigated. Experimental data indicate that the electromagnetic energy is mainly converted to magnetic energy and kinetic energy and ohmic heating energy can be neglected before the final stagnation. Themore » kinetic energy can be responsible for the x-ray radiation before the peak power. After the stagnation, the electromagnetic energy coupled by the load continues increasing and the resistance of the load achieves its maximum of 0.6–1.0 Ω in about 10–20 ns.« less

Testing Numerical Models of Cool Core Galaxy Cluster Formation with X-Ray Observations

NASA Astrophysics Data System (ADS)

Henning, Jason W.; Gantner, Brennan; Burns, Jack O.; Hallman, Eric J.

2009-12-01

Using archival Chandra and ROSAT data along with numerical simulations, we compare the properties of cool core and non-cool core galaxy clusters, paying particular attention to the region beyond the cluster cores. With the use of single and double β-models, we demonstrate a statistically significant difference in the slopes of observed cluster surface brightness profiles while the cluster cores remain indistinguishable between the two cluster types. Additionally, through the use of hardness ratio profiles, we find evidence suggesting cool core clusters are cooler beyond their cores than non-cool core clusters of comparable mass and temperature, both in observed and simulated clusters. The similarities between real and simulated clusters supports a model presented in earlier work by the authors describing differing merger histories between cool core and non-cool core clusters. Discrepancies between real and simulated clusters will inform upcoming numerical models and simulations as to new ways to incorporate feedback in these systems.

Enhanced energy coupling and x-ray emission in Z-pinch plasma implosions

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Thornhill, J. W.; Apruzese, J. P.; Davis, J.; Deeney, C.; Coverdale, C. A.

2004-08-01

Recent experiments conducted on the Saturn pulsed-power generator at Sandia National Laboratories [R. B. Spielman et al., in Proceedings of the Second International Conference on Dense Z Pinches, Laguna Beach, CA, 1989, edited by N. R. Pereira, J. Davis, and N. Rostoker (American Institute of Physics, New York, 1989), p. 3] have produced large amounts of x-ray output, which cannot be accounted for in conventional magnetohydrodynamic (MHD) calculations. In these experiments, the Saturn current had a rise time of ~180 ns in contrast to a rise time of ~60 ns in Saturn's earlier mode of operation. In both aluminum and tungsten wire-array Z-pinch implosions, 2-4 times more x-ray output was generated than could be supplied according to one-dimensional (1D) magnetohydrodynamic calculations by the combined action of the j×B acceleration forces and ohmic heating (as described by a classical Braginskii resistivity). In this paper, we reexamine the problem of coupling transmission line circuits to plasma fluid equations and derive expressions for the Z-pinch load circuit resistance and inductance that relate these quantities in a 1D analysis to the surface resistivity of the fluid, and to the magnetic field energy that is stored in the vacuum diode, respectively. Enhanced energy coupling in this analysis, therefore, comes from enhancements to the surface resistivity, and we show that plasma resistivities approximately three orders of magnitude larger than classical are needed in order to achieve energy inputs that are comparable to the Saturn experiment x-ray outputs. Large enhancements of the plasma resistivity increase the rate of magnetic field and current diffusion, significantly modify the qualitative features of the MHD, and raise important questions as to how the plasma fluid dynamics converts enhanced energy inputs into enhanced x-ray outputs. One-dimensional MHD calculations in which resistivity values are adjusted phenomenologically are used to illustrate how

Bond-orientational analysis of hard-disk and hard-sphere structures.

PubMed

Senthil Kumar, V; Kumaran, V

2006-05-28

We report the bond-orientational analysis results for the thermodynamic, random, and homogeneously sheared inelastic structures of hard-disks and hard-spheres. The thermodynamic structures show a sharp rise in the order across the freezing transition. The random structures show the absence of crystallization. The homogeneously sheared structures get ordered at a packing fraction higher than the thermodynamic freezing packing fraction, due to the suppression of crystal nucleation. On shear ordering, strings of close-packed hard-disks in two dimensions and close-packed layers of hard-spheres in three dimensions, oriented along the velocity direction, slide past each other. Such a flow creates a considerable amount of fourfold order in two dimensions and body-centered-tetragonal (bct) structure in three dimensions. These transitions are the flow analogs of the martensitic transformations occurring in metals due to the stresses induced by a rapid quench. In hard-disk structures, using the bond-orientational analysis we show the presence of fourfold order. In sheared inelastic hard-sphere structures, even though the global bond-orientational analysis shows that the system is highly ordered, a third-order rotational invariant analysis shows that only about 40% of the spheres have face-centered-cubic (fcc) order, even in the dense and near-elastic limits, clearly indicating the coexistence of multiple crystalline orders. When layers of close-packed spheres slide past each other, in addition to the bct structure, the hexagonal-close-packed (hcp) structure is formed due to the random stacking faults. Using the Honeycutt-Andersen pair analysis and an analysis based on the 14-faceted polyhedra having six quadrilateral and eight hexagonal faces, we show the presence of bct and hcp signatures in shear ordered inelastic hard-spheres. Thus, our analysis shows that the dense sheared inelastic hard-spheres have a mixture of fcc, bct, and hcp structures.

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Calamy, H.; Hamann, F.; Lassalle, F.

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1{mu}s rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim ofmore » giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-{theta} simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.« less

Wire Array Z-pinches on Sphinx Machine: Experimental Results and Relevant Points of Microsecond Implosion Physics

NASA Astrophysics Data System (ADS)

Calamy, H.; Hamann, F.; Lassalle, F.; Bayol, F.; Mangeant, C.; Morell, A.; Huet, D.; Bedoch, J. P.; Chittenden, J. P.; Lebedev, S. V.; Jennings, C. A.; Bland, S. N.

2006-01-01

Centre d'Etudes de Gramat (France) has developed an efficient long implosion time (800 ns) Aluminum plasma radiation source (PRS). Based on the LTD technology, the SPHINX facility is developed as a 1-3MJ, 1μs rise time, 4-10 MA current driver. In this paper, it was used in 1MJ, 4MA configuration to drive Aluminum nested wire arrays Z-pinches with K-shell yield up to 20 kJ and a FWHM of the x-ray pulse of about 50 ns. We present latest SPHINX experiments and some of the main physic issues of the microsecond regime. Experimental setup and results are described with the aim of giving trends that have been obtained. The main features of microsecond implosion of wire arrays can be analyzed thanks to same methods and theories as used for faster Z-pinches. The effect of load polarity was examined. The stability of the implosion , one of the critical point of microsecond wire arrays due to the load dimensions imposed by the time scale, is tackled. A simple scaling from 100 ns Z-pinch results to 800 ns ones gives good results and the use of nested arrays improves dramatically the implosion quality and the Kshell yield of the load. However, additional effects such as the impact of the return current can geometry on the implosion have to be taken into account on our loads. Axial inhomogeneity of the implosion the origin of which is not yet well understood occurs in some shots and impacts the radiation output. The shape of the radiative pulse is discussed and compared with the homogeneity of the implosion. Numerical 2D R-Z and R-θ simulations are used to highlight some experimental results and understand the plasma conditions during these microsecond wire arrays implosions.

Effect of pinching-evoked pain on jaw-stretch reflexes and exteroceptive suppression periods in healthy subjects.

PubMed

Biasiotta, A; Peddireddy, A; Wang, K; Romaniello, A; Frati, A; Svensson, P; Arendt-Nielsen, L

2007-10-01

To investigate the influence of conditioning cutaneous nociceptive inputs by a new "pinch" model on the jaw-stretch reflex and the exteroceptive suppression periods (ES1 and ES2) in jaw muscles. The jaw-stretch reflex was evoked with the use of a custom-made muscle stretcher and electrical stimuli were used to evoke an early and late exteroceptive suppression period (ES1 and ES2) in the jaw-closing muscles. Electromyographic (EMG) activity was recorded bilaterally from the masseter and temporalis muscles. These brainstem reflexes were recorded in 19 healthy men (28.8+/-1.1 years) during three different conditions: one painful clip applied to the earlobe; one painful clip applied to the nostril, and four painful clips applied simultaneously to the earlobe, nostril, eyebrow, and lower lip. Pain intensity induced by the application of the clips was scored continuously by the subjects on a 100mm visual analogue scale (VAS). The highest VAS pain scores were evoked by placement of four clips (79+/-0.5mm). There was no significant modulation of the jaw-stretch reflex (ANOVAs: P=0.929), the ES1 (P=0.298) or ES2 (P=0.082) in any of the three painful conditions. Intense and tonic cutaneous pain could be elicited by this new "pinch" pain model; however, there was no significant modulation on either excitatory or inhibitory brainstem reflex responses. The novel observation that high-intensity pinch stimuli applied to the craniofacial region fail to modulate two different brainstem reflexes is in contrast to other experimental pain studies documented facilitation of the jaw-stretch reflexes or inhibition of exteroceptive suppression periods. The clinical implication of the present findings is that only some craniofacial pain conditions could be expected to show perturbation of the brainstem reflex responses.

Pinch-off mechanism in double-lateral-gate junctionless transistors fabricated by scanning probe microscope based lithography

PubMed Central

Dehzangi, Arash; Abedini, Alam; Abdullah, Ahmad Makarimi; Saion, Elias; Hutagalung, Sabar D; Hamidon, Mohd N; Hassan, Jumiah

2012-01-01

Summary A double-lateral-gate p-type junctionless transistor is fabricated on a low-doped (1015) silicon-on-insulator wafer by a lithography technique based on scanning probe microscopy and two steps of wet chemical etching. The experimental transfer characteristics are obtained and compared with the numerical characteristics of the device. The simulation results are used to investigate the pinch-off mechanism, from the flat band to the off state. The study is based on the variation of the carrier density and the electric-field components. The device is a pinch-off transistor, which is normally in the on state and is driven into the off state by the application of a positive gate voltage. We demonstrate that the depletion starts from the bottom corner of the channel facing the gates and expands toward the center and top of the channel. Redistribution of the carriers due to the electric field emanating from the gates creates an electric field perpendicular to the current, toward the bottom of the channel, which provides the electrostatic squeezing of the current. PMID:23365794

Electron temperature diagnostics of aluminium plasma in a z-pinch experiment at the “QiangGuang-1" facility

NASA Astrophysics Data System (ADS)

Li, Mo; Wu, Jian; Wang, Liang-Ping; Wu, Gang; Han, Juan-Juan; Guo, Ning; Qiu, Meng-Tong

2012-12-01

Two curved crystal spectrometers are set up on the “QiangGuang-1" generator to measure the z-pinch plasma spectra emitted from planar aluminum wire array loads. Kodak Biomax-MS film and an IRD AXUVHS5# array are employed to record time-integrated and time-resolved free-bound radiation, respectively. The photon energy recorded by each detector is ascertained by using the L-shell lines of molybdenum plasma. Based on the exponential relation between the continuum power and photon energies, the aluminum plasma electron temperatures are measured. For the time-integrated diagnosis, several “bright spots" indicate electron temperatures between (450 eV ~ 520 eV) ± 35%. And for the time-resolved ones, the result shows that the electron temperature reaches about 800 eV ± 30% at peak power. The system satisfies the demand of z-pinch plasma electron temperature diagnosis on a ~ 1 MA facility.

Design of Z-Pinch and Dense Plasma Focus Powered Vehicles

NASA Technical Reports Server (NTRS)

Polsgrove, Tara; Fincher, Sharon; Adams, Robert B.; Cassibry, Jason; Cortez, Ross; Turner, Matthew; Maples, C. Daphne; Miermik, Janie N.; Statham, Geoffrey N.; Fabisinski, Leo;

Incremental k-core decomposition: Algorithms and evaluation

DOE PAGES

Sariyuce, Ahmet Erdem; Gedik, Bugra; Jacques-SIlva, Gabriela; ...

2016-02-01

A k-core of a graph is a maximal connected subgraph in which every vertex is connected to at least k vertices in the subgraph. k-core decomposition is often used in large-scale network analysis, such as community detection, protein function prediction, visualization, and solving NP-hard problems on real networks efficiently, like maximal clique finding. In many real-world applications, networks change over time. As a result, it is essential to develop efficient incremental algorithms for dynamic graph data. In this paper, we propose a suite of incremental k-core decomposition algorithms for dynamic graph data. These algorithms locate a small subgraph that ismore » guaranteed to contain the list of vertices whose maximum k-core values have changed and efficiently process this subgraph to update the k-core decomposition. We present incremental algorithms for both insertion and deletion operations, and propose auxiliary vertex state maintenance techniques that can further accelerate these operations. Our results show a significant reduction in runtime compared to non-incremental alternatives. We illustrate the efficiency of our algorithms on different types of real and synthetic graphs, at varying scales. Furthermore, for a graph of 16 million vertices, we observe relative throughputs reaching a million times, relative to the non-incremental algorithms.« less

Post-pinch generation of electron beam in a low energy Mather-type plasma focus device

NASA Astrophysics Data System (ADS)

Behbahani, R. A.; Aghamir, F. M.; Aghamir

2013-10-01

The post-pinch generation of electron beam in a low energy Mather-type plasma focus (PF) device has been investigated. A fast-calibrated Rogowski coil was used to monitor the emission of electron beam. A two-channel diode X-ray spectrometer along with suitable filters provided the records of energy spectrum of X-ray radiation. Single time-period emissions of electron beam with duration of 100 to 20 ns were recorded in the high range of the device operating pressure (0.8-2 mbar). However, in the low range regime (0.2-0.8 mbar), occurrence of single spike electron beam with duration of 150 +/- 50 ns, as well as multi-emission of electrons with duration of 400 +/- 50 ns, was visible. A multi-peak of tube voltage along with multi-time-period radiation of X-rays dominated by copper lines (Cukα and Cukβ) was noticeable in the low-pressure range. The generated electron beam during the post-pinch phase of anomalous resistances is suspected to be the main source of X-ray radiation. This can also be related to the turbulence of the plasma column during the occurrence of anomalous resistances.

Measurements of the momentum and current transport from tearing instability in the Madison Symmetric Torus reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuritsyn, A.; Fiksel, G.; Almagri, A. F.

2009-05-15

In this paper measurements of momentum and current transport caused by current driven tearing instability are reported. The measurements are done in the Madison Symmetric Torus reversed-field pinch [R. N. Dexter, D. W. Kerst, T. W. Lovell, S. C. Prager, and J. C. Sprott, Fusion Technol. 19, 131 (1991)] in a regime with repetitive bursts of tearing instability causing magnetic field reconnection. It is established that the plasma parallel momentum profile flattens during these reconnection events: The flow decreases in the core and increases at the edge. The momentum relaxation phenomenon is similar in nature to the well established relaxationmore » of the parallel electrical current and could be a general feature of self-organized systems. The measured fluctuation-induced Maxwell and Reynolds stresses, which govern the dynamics of plasma flow, are large and almost balance each other such that their difference is approximately equal to the rate of change of plasma momentum. The Hall dynamo, which is directly related to the Maxwell stress, drives the parallel current profile relaxation at resonant surfaces at the reconnection events. These results qualitatively agree with analytical calculations and numerical simulations. It is plausible that current-driven instabilities can be responsible for momentum transport in other laboratory and astrophysical plasmas.« less

SuperHERO: The Next Generation Hard X-Ray HEROES Telescope

NASA Technical Reports Server (NTRS)

Wilson-Hodge, Colleen A.; Gaskin, Jessica A.; Christe, Steven D.; Elsner, Ronald F.; Ramsey, Brian D.; Seller, Paul; Shih, Albert Y.; Stuchlik, David W.; Swartz, Douglas A.; Tenant, Allyn F.;

SuperHERO: The Next Generation Hard X-ray HEROES Telescope

NASA Technical Reports Server (NTRS)

Gaskin, Jessica A.; Christe, Steven D.; Wilson-Hodge, Colleen; Shih, Albert Y. M.; Ramsey, Brian D.; Tennant, Allyn F.; Swartz, Douglas A.

2014-01-01

SuperHERO is a new high-sensitivity Long Duration Balloon (LDB)-capable, hard-x-ray (20-75 keV) telescope for making novel astrophysics and heliophysics observations. The proposed SuperHERO payload will be developed jointly by the Astrophysics Office at NASA Marshall Space Flight Center, the Solar Physics Laboratory and Wallops Flight Facility at NASA Goddard Space Flight Center. SuperHERO is a follow-on payload to the High Energy Replicated Optics to Explore the Sun (HEROES) balloon-borne telescope that recently launched from Fort Sumner, NM in September of 2013. The HEROES core instrument is a hard x-ray telescope consisting of x-ray 109 optics configured into 8 modules. Each module is aligned to a matching gas-filled detector at a focal length of 6 m. SuperHERO will make significant improvements to the HEROES payload, including: new solid-state multi-pixel CdTe detectors, additional optics, the Wallops Arc-Second Pointer, alignment monitoring systems and lighter gondola.

Locked modes in two reversed-field pinch devices of different size and shell system

NASA Astrophysics Data System (ADS)

Malmberg, J.-A.; Brunsell, P. R.; Yagi, Y.; Koguchi, H.

2000-10-01

The behavior of locked modes in two reversed-field pinch devices, the Toroidal Pinch Experiment (TPE-RX) [Y. Yagi et al., Plasma Phys. Control. Fusion 41, 2552 (1999)] and Extrap T2 [J. R. Drake et al., in Plasma Physics and Controlled Nuclear Fusion Research 1996, Montreal (International Atomic Energy Agency, Vienna, 1996), Vol. 2, p. 193] is analyzed and compared. The main characteristics of the locked mode are qualitatively similar. The toroidal distribution of the mode locking shows that field errors play a role in both devices. The probability of phase locking is found to increase with increasing magnetic fluctuation levels in both machines. Furthermore, the probability of phase locking increases with plasma current in TPE-RX despite the fact that the magnetic fluctuation levels decrease. A comparison with computations using a theoretical model estimating the critical mode amplitude for locking [R. Fitzpatrick et al., Phys. Plasmas 6, 3878 (1999)] shows a good correlation with experimental results in TPE-RX. In Extrap T2, the magnetic fluctuations scale weakly with both plasma current and electron densities. This is also reflected in the weak scaling of the magnetic fluctuation levels with the Lundquist number (˜S-0.06). In TPE-RX, the corresponding scaling is ˜S-0.18.

A plasma model for reversed field pinch circuit design

NASA Astrophysics Data System (ADS)

Johnston, J. W.

1981-03-01

A plasma model has been developed for use in the design of circuits for reversed field pinch experiments. The magnetic field is assumed to evolve through a given series of relaxed states with the plasma resistivity specified as a function of time. At any instant the magnetic field configuration is determined by the field energy and the toroidal flux. If the Bessel function model is chosen as the relaxed state then the magnetic helicity can be used as an alternative to the magnetic energy without altering the results. Simulations of discharges on ZETA and ETA BETA II are presented. By suitable choices of the relaxed field configuration and plasma resistivity it is possible to obtain close agreement with the experimental waveforms. Application to the proposed RFX device is discussed.

Diffusion of finite-sized hard-core interacting particles in a one-dimensional box: Tagged particle dynamics.

PubMed

Lizana, L; Ambjörnsson, T

2009-11-01

We solve a nonequilibrium statistical-mechanics problem exactly, namely, the single-file dynamics of N hard-core interacting particles (the particles cannot pass each other) of size Delta diffusing in a one-dimensional system of finite length L with reflecting boundaries at the ends. We obtain an exact expression for the conditional probability density function rhoT(yT,t|yT,0) that a tagged particle T (T=1,...,N) is at position yT at time t given that it at time t=0 was at position yT,0. Using a Bethe ansatz we obtain the N -particle probability density function and, by integrating out the coordinates (and averaging over initial positions) of all particles but particle T , we arrive at an exact expression for rhoT(yT,t|yT,0) in terms of Jacobi polynomials or hypergeometric functions. Going beyond previous studies, we consider the asymptotic limit of large N , maintaining L finite, using a nonstandard asymptotic technique. We derive an exact expression for rhoT(yT,t|yT,0) for a tagged particle located roughly in the middle of the system, from which we find that there are three time regimes of interest for finite-sized systems: (A) for times much smaller than the collision time ttaucoll but times smaller than the equilibrium time ttaue , rhoT(yT,t|yT,0) approaches a polynomial-type equilibrium probability density function. Notably, only regimes (A) and (B) are found in the previously considered infinite systems.

Hard TiCx/SiC/a-C:H nanocomposite thin films using pulsed high energy density plasma focus device

NASA Astrophysics Data System (ADS)

Umar, Z. A.; Rawat, R. S.; Tan, K. S.; Kumar, A. K.; Ahmad, R.; Hussain, T.; Kloc, C.; Chen, Z.; Shen, L.; Zhang, Z.

2013-04-01

Thin films of TiCx/SiC/a-C:H were synthesized on Si substrates using a complex mix of high energy density plasmas and instability accelerated energetic ions of filling gas species, emanated from hot and dense pinched plasma column, in dense plasma focus device. The conventional hollow copper anode of Mather type plasma focus device was replaced by solid titanium anode for synthesis of TiCx/SiC/a-C:H nanocomposite thin films using CH4:Ar admixture of (1:9, 3:7 and 5:5) for fixed 20 focus shots as well as with different number of focus shots with fixed CH4:Ar admixture ratio 3:7. XRD results showed the formation of crystalline TiCx/SiC phases for thin film synthesized using different number of focus shots with CH4:Ar admixture ratio fixed at 3:7. SEM results showed that the synthesized thin films consist of nanoparticle agglomerates and the size of agglomerates depended on the CH4:Ar admixture ratio as well as on the number of focus shots. Raman analysis showed the formation of polycrystalline/amorphous Si, SiC and a-C for different CH4:Ar ratio as well as for different number of focus shots. The XPS analysis confirmed the formation of TiCx/SiC/a-C:H composite thin film. Nanoindentation results showed that the hardness and elastic modulus values of composite thin films increased with increasing number of focus shots. Maximum values of hardness and elastic modulus at the surface of the composite thin film were found to be about 22 and 305 GPa, respectively for 30 focus shots confirming the successful synthesis of hard composite TiCx/SiC/a-C:H coatings.

Study of the hard-disk system at high densities: the fluid-hexatic phase transition.

PubMed

Mier-Y-Terán, Luis; Machorro-Martínez, Brian Ignacio; Chapela, Gustavo A; Del Río, Fernando

2018-06-21

Integral equations of uniform fluids have been considered unable to predict any characteristic feature of the fluid-solid phase transition, including the shoulder that arises in the second peak of the fluid-phase radial distribution function, RDF, of hard-core systems obtained by computer simulations, at fluid densities very close to the structural two-step phase transition. This reasoning is based on the results of traditional integral approximations, like Percus-Yevick, PY, which does not show such a shoulder in hard-core systems, neither in two nor three dimensions. In this work, we present results of three Ansätze, based on the PY theory, that were proposed to remedy the lack of PY analytical solutions in two dimensions. This comparative study shows that one of those Ansätze does develop a shoulder in the second peak of the RDF at densities very close to the phase transition, qualitatively describing this feature. Since the shoulder grows into a peak at still higher densities, this integral equation approach predicts the appearance of an orientational order characteristic of the hexatic phase in a continuous fluid-hexatic phase transition.

Analytic model for the dynamic Z-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piriz, A. R., E-mail: roberto.piriz@uclm.es; Sun, Y. B.; Tahir, N. A.

2015-06-15

A model is presented for describing the cylindrical implosion of a shock wave driven by an accelerated piston. It is based in the identification of the acceleration of the shocked mass with the acceleration of the piston. The model yields the separate paths of the piston and the shock. In addition, by considering that the shocked region evolves isentropically, the approximate profiles of all the magnitudes in the shocked region are obtained. The application to the dynamic Z-pinch is presented and the results are compared with the well known snowplow and slug models which are also derived as limiting casesmore » of the present model. The snowplow model is seen to yield a trajectory in between those of the shock and the piston. Instead, the neglect of the inertial effects in the slug model is seen to produce a too fast implosion, and the pressure uniformity is shown to lead to an unphysical instantaneous piston stopping when the shock arrives to the axis.« less

Dense plasma focus production in a hypocycloidal pinch

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.; Hohl, F.

1975-01-01

A type of high-power pinch apparatus consisting of disk electrodes was developed, and diagnostic measurements to study its mechanism of dense plasma production were made. The collapse fronts of the current sheets are well organized, and dense plasma focuses are produced on the axis with radial stability in excess of 5 microns. A plasma density greater than 10 to the 18th power/cubic cm was determined with Stark broadening and CO2 laser absorption. A plasma temperature of approximately 1 keV was measured with differential transmission of soft X-rays through thin foils. Essentially complete absorption of a high-energy CO2 laser beam was observed. The advantages of this apparatus over the coaxial plasma focus are in (1) the plasma volume, (2) the stability, (3) the containment time, (4) the easy access to additional heating by laser or electron beams, and (5) the possibility of scaling up to a multiple array for high-power operation.

Generation of mechanical vibrations in metal samples by the use of the pinch effect

NASA Astrophysics Data System (ADS)

Troitskiy, O. A.; Skvortsov, O. B.; Stashenko, V. I.

2017-07-01

The article presents the recent research in electrodynamic processes for metal samples exposed to current pulses. The pinch effect and the skin effect cause the vibration of the metal rods. The results of these studies show how current and magnetic field interact with material samples of gold, silver and copper. The analysis allowed establishing the dependences of peak acceleration on current density and conductor diameter. The dependencies can be used in metal workings and for nondestructive testing.

Effect of Pressure Anisotropy on the m = 1 Small Wavelength Modes in Z-Pinches

NASA Astrophysics Data System (ADS)

Faghihi, M.

1987-05-01

A generalization of Freidberg's perpendicular MHD model is used to investigate the effect of pressure anisotropy on the small wavelength internal kink (m = 1) mode instability in a Z-Pinch. A normal mode analysis of perturbed motion of an incompressible, collisionless and cylindrical plasma is performed. The stability criterion is (rΣB2)' <= 0, where Σ = 1 - (P|| - P⊥)/B2. It cannot be fulfilled without violation of the fire hose stability condition Σ >= 0.

Coherent structures and anomalous transport in reversed field pinch plasmas

NASA Astrophysics Data System (ADS)

Antoni, V.; Drake, J. R.; Spada, E.; Spolaore, M.; Vianello, N.; Bergsåker, H.; Cavazzana, R.; Cecconello, M.; Martines, E.; Serianni, G.

2006-02-01

The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is discussed focusing on the analysis tools applied. The role of these structures in the particle anomalous transport is addressed, showing that their collisions can contribute up to 50% the total particle losses.This process is shown to be responsible for bursts in particle flux and it is found to set a characteristic collision time, which is in agreement with the statistical properties of laminar times for particle flux bursts.

Remember Hard But Think Softly: Metaphorical Effects of Hardness/Softness on Cognitive Functions.

PubMed

Xie, Jiushu; Lu, Zhi; Wang, Ruiming; Cai, Zhenguang G

2016-01-01

Previous studies have found that bodily stimulation, such as hardness biases social judgment and evaluation via metaphorical association; however, it remains unclear whether bodily stimulation also affects cognitive functions, such as memory and creativity. The current study used metaphorical associations between "hard" and "rigid" and between "soft" and "flexible" in Chinese, to investigate whether the experience of hardness affects cognitive functions whose performance depends prospectively on rigidity (memory) and flexibility (creativity). In Experiment 1, we found that Chinese-speaking participants performed better at recalling previously memorized words while sitting on a hard-surface stool (the hard condition) than a cushioned one (the soft condition). In Experiment 2, participants sitting on a cushioned stool outperformed those sitting on a hard-surface stool on a Chinese riddle task, which required creative/flexible thinking, but not on an analogical reasoning task, which required both rigid and flexible thinking. The results suggest the hardness experience affects cognitive functions that are metaphorically associated with rigidity or flexibility. They support the embodiment proposition that cognitive functions and representations can be grounded in bodily states via metaphorical associations.

Room-temperature ferromagnetic Cr-doped Ge/GeOx core-shell nanowires.

PubMed

Katkar, Amar S; Gupta, Shobhnath P; Seikh, Md Motin; Chen, Lih-Juann; Walke, Pravin S

2018-06-08

The Cr-doped tunable thickness core-shell Ge/GeO x nanowires (NWs) were synthesized and characterized using x-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy and magnetization studies. The shell thickness increases with the increase in synthesis temperature. The presence of metallic Cr and Cr 3+ in core-shell structure was confirmed from XPS study. The magnetic property is highly sensitive to the core-shell thickness and intriguing room temperature ferromagnetism is realized only in core-shell NWs. The magnetization decreases with an increase in shell thickness and practically ceases to exist when there is no core. These NWs show remarkably high Curie temperature (T C  > 300 K) with the dominating values of its magnetic remanence (M R ) and coercivity (H C ) compared to germanium dilute magnetic semiconductor nanomaterials. We believe that our finding on these Cr-doped Ge/GeO X core-shell NWs has the potential to be used as a hard magnet for future spintronic devices, owing to their higher characteristic values of ferromagnetic ordering.

Ultra-fast magnetic vortex core reversal by a local field pulse

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rückriem, R.; Albrecht, M., E-mail: manfred.albrecht@physik.uni-augsburg.de; Schrefl, T.

2014-02-03

Magnetic vortex core reversal of a 20-nm-thick permalloy disk with a diameter of 100 nm was studied by micromagnetic simulations. By applying a global out-of-plane magnetic field pulse, it turned out that the final core polarity is very sensitive to pulse width and amplitude, which makes it hard to control. The reason for this phenomenon is the excitation of radial spin waves, which dominate the reversal process. The excitation of spin waves can be strongly suppressed by applying a local field pulse within a small area at the core center. With this approach, ultra-short reversal times of about 15 ps weremore » achieved, which are ten times faster compared to a global pulse.« less

SMALLER FOOTPRINT DRILLING SYSTEM FOR DEEP AND HARD ROCK ENVIRONMENTS; FEASIBILITY OF ULTRA-HIGH SPEED DIAMOND DRILLING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alan Black; Arnis Judzis

2004-10-01

The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high (greater than 10,000 rpm) rotational speeds. The work includes a feasibility of concept research effort aimed at development and test results that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with rigs having a smaller footprint to be more mobile. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration rockmore » cutting with substantially lower inputs of energy and loads. The project draws on TerraTek results submitted to NASA's ''Drilling on Mars'' program. The objective of that program was to demonstrate miniaturization of a robust and mobile drilling system that expends small amounts of energy. TerraTek successfully tested ultrahigh speed ({approx}40,000 rpm) small kerf diamond coring. Adaptation to the oilfield will require innovative bit designs for full hole drilling or continuous coring and the eventual development of downhole ultra-high speed drives. For domestic operations involving hard rock and deep oil and gas plays, improvements in penetration rates is an opportunity to reduce well costs and make viable certain field developments. An estimate of North American hard rock drilling costs is in excess of $1,200 MM. Thus potential savings of $200 MM to $600 MM are possible if drilling rates are doubled [assuming bit life is reasonable]. The net result for operators is improved profit margin as well as an improved position on reserves. The significance of the ''ultra-high rotary speed drilling system'' is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining

SMALLER FOOTPRINT DRILLING SYSTEM FOR DEEP AND HARD ROCK ENVIRONMENTS; FEASIBILITY OF ULTRA-HIGH SPEED DIAMOND DRILLING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alan Black; Arnis Judzis

2004-10-01

The two phase program addresses long-term developments in deep well and hard rock drilling. TerraTek believes that significant improvements in drilling deep hard rock will be obtained by applying ultra-high (greater than 10,000 rpm) rotational speeds. The work includes a feasibility of concept research effort aimed at development and test results that will ultimately result in the ability to reliably drill ''faster and deeper'' possibly with rigs having a smaller footprint to be more mobile. The principle focus is on demonstration testing of diamond bits rotating at speeds in excess of 10,000 rpm to achieve high rate of penetration rockmore » cutting with substantially lower inputs of energy and loads. The project draws on TerraTek results submitted to NASA's ''Drilling on Mars'' program. The objective of that program was to demonstrate miniaturization of a robust and mobile drilling system that expends small amounts of energy. TerraTek successfully tested ultrahigh speed ({approx}40,000 rpm) small kerf diamond coring. Adaptation to the oilfield will require innovative bit designs for full hole drilling or continuous coring and the eventual development of downhole ultra-high speed drives. For domestic operations involving hard rock and deep oil and gas plays, improvements in penetration rates is an opportunity to reduce well costs and make viable certain field developments. An estimate of North American hard rock drilling costs is in excess of $1,200 MM. Thus potential savings of $200 MM to $600 MM are possible if drilling rates are doubled [assuming bit life is reasonable]. The net result for operators is improved profit margin as well as an improved position on reserves. The significance of the ''ultra-high rotary speed drilling system'' is the ability to drill into rock at very low weights on bit and possibly lower energy levels. The drilling and coring industry today does not practice this technology. The highest rotary speed systems in oil field and mining

Neutron Activation Diagnostics in Deuterium Gas-Puff Experiments on the 3 MA GIT-12 Z-Pinch

NASA Astrophysics Data System (ADS)

Cikhardt, J.; Klir, D.; Rezac, K.; Cikhardtova, B.; Kravarik, J.; Kubes, P.; Sila, O.; Shishlov, A. V.; Cherdizov, R. K.; Fursov, F. I.; Kokshenev, V. A.; Kurmaev, N. E.; Labetsky, A. Yu; Ratakhin, N. A.; Dudkin, G. N.; Garapatsky, A. A.; Padalko, V. N.; Varlachev, V. A.; Turek, K.

2016-10-01

The experiments with a deuterium z-pinch on the GIT-12 generator at IHCE in Tomsk were performed in the frame of the Czech-Russian agreement. A set of neutron diagnostics included scintillation time-of-flight detectors, bubble detectors, and several kinds of threshold nuclear activation detectors in the order to obtain information about the yield, anisotropy, and spectrum of the neutrons produced by a deuterium gas-puff. The average neutron yield in these experiments was of the order of 1012 neutrons per a single shot. The energy spectrum of the produced neutrons was evaluated using neutron time-of-flight detectors and a set of neutron activation detectors. Because the deuterons in the pinch achieve multi-MeV energies, non-DD neutrons are produced by nuclear reactions of deuterons with a stainless steel vacuum chamber and aluminum components of diagnostics inside the chamber. An estimated number of the non-DD was of the order of 1011. GACR (Grant No. 16-07036S), CME (Grant Nos. LD14089, LG13029, and LH13283), MESRF (Grant No. RFMEFI59114X0001), IAEA (Grant No. RC17088), CTU (Grant No. SGS 16/223/OHK3/3T/13).

Heavy ion beam probe operation in time varying equilibria of improved confinement reversed field pinch discharges.

PubMed

Demers, D R; Chen, X; Schoch, P M; Fimognari, P J

2010-10-01

Operation of a heavy ion beam probe (HIBP) on a reversed field pinch is unique from other toroidal applications because the magnetic field is more temporal and largely produced by plasma current. Improved confinement, produced through the transient application of a poloidal electric field which leads to a reduction of dynamo activity, exhibits gradual changes in equilibrium plasma quantities. A consequence of this is sweeping of the HIBP trajectories by the dynamic magnetic field, resulting in motion of the sample volume. In addition, the plasma potential evolves with the magnetic equilibrium. Measurement of the potential as a function of time is thus a combination of temporal changes of the equilibrium and motion of the sample volume. A frequent additional complication is a nonideal balance of ion current on the detectors resulting from changes in the beam trajectory (magnetic field) and energy (plasma potential). This necessitates use of data selection criteria. Nevertheless, the HIBP on the Madison Symmetric Torus has acquired measurements as a function of time throughout improved confinement. A technique developed to infer the potential in the improved confinement reversed field pinch from HIBP data in light of the time varying plasma equilibrium will be discussed.

Inference of the electron temperature in ICF implosions from the hard X-ray spectral continuum

NASA Astrophysics Data System (ADS)

Kagan, Grigory; Landen, O. L.; Svyatsky, D.; Sio, H.; Kabadi, N. V.; Simpson, R. A.; Gatu Johnson, M.; Frenje, J. A.; Petrasso, R. D.; Shah, R. C.; Joshi, T. R.; Hakel, P.; Weber, T. E.; Rinderknecht, H. G.; Thorn, D.; Schneider, M.; Bradley, D.; Kilkenny, J.

2017-10-01

The NIF Continuum Spectrometer, scheduled to be first deployed in Fall of 2017, will infer the imploded core electron temperature from the free-free continuum self-emission spectra of photons with energies of 20 to 30 keV. However, this hard X-ray radiation is emitted by the tail of the electron distribution, which likely deviates from Maxwellian and thus obscures interpretation of the data. We investigate resulting modifications to the X-ray spectra. The logarithmic slope of the spectrum from the more realistic, non-thermal tail of the electron distribution is found to decrease more rapidly at higher photon energies, as compared to the perfectly Maxwellian case. Interpreting the spectrum with assumption of Maxwellian electrons enforced is shown to give an electron temperature that is lower than the actual one. Conversely, due to its connection with the non-thermal features in the electron distribution, hard X-ray emission can provide unprecedented information about kinetic processes in the hot DT core. This work was performed under the auspices of the U.S. Dept. of Energy by the Los Alamos National Security, LLC, Los Alamos National Laboratory under Contract No. DE-AC52-06NA25396.

Parametric study of rod-pinch diode using particle-in-cell simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, R.; Biswas, D., E-mail: raghav@barc.gov.in; Chandra, R.

2014-07-01

We perform Particle-In-Cell (PIC) simulation of KALI-30 GW pulsed power generator based rod-pinch diode. It is shown that ions emitted from the anode-plasma play a crucial role in diode dynamics. It is found that ions not only help in compensating the space charge due to electron beam, but also lead to enhancement of the local electric field at the side walls of the cathode leading to additional electron emission from the side wall. Electrons emanating from one side wall of the cathode tend to converge at the anode tip. This can be used to design an improved Flash X-ray source.more » (author)« less

Particle drift model for Z-pinch-driven magneto-Rayleigh-Taylor instability

NASA Astrophysics Data System (ADS)

Dan, Jia Kun; Xu, Qiang; Wang, Kun Lun; Ren, Xiao Dong; Huang, Xian Bin

2016-09-01

A theoretical model of Z-pinch driven magneto-Rayleigh-Taylor instability is proposed based on the particle drift point of view, which can explain the helical instability structure observed in premagnetized imploding liner experiments. It is demonstrated that all possible drift motions, including polarization drift, gradient drift, and curvature drift, which can lead to charge separations, each will attribute to an effective gravity acceleration. Theoretical predictions given by this model are dramatically different from those given by previous theories which have been readily recovered in the theory presented here as a limiting case. The theory shows qualitative agreement with available experimental data of the pitch angle and provides certain predictions to be verified.

30 CFR 75.1720-1 - Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Distinctively colored hard hats, or hard caps... STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1720-1 Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color...

30 CFR 75.1720-1 - Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Distinctively colored hard hats, or hard caps... STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1720-1 Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color...

30 CFR 75.1720-1 - Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Distinctively colored hard hats, or hard caps... STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1720-1 Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color...

30 CFR 75.1720-1 - Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Distinctively colored hard hats, or hard caps... STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1720-1 Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color...

30 CFR 75.1720-1 - Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Distinctively colored hard hats, or hard caps... STANDARDS-UNDERGROUND COAL MINES Miscellaneous § 75.1720-1 Distinctively colored hard hats, or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color...

30 CFR 77.1710-1 - Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Distinctively colored hard hats or hard caps... Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color from those worn by experienced miners shall be worn at...

30 CFR 77.1710-1 - Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Distinctively colored hard hats or hard caps... Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color from those worn by experienced miners shall be worn at...

30 CFR 77.1710-1 - Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Distinctively colored hard hats or hard caps... Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color from those worn by experienced miners shall be worn at...

30 CFR 77.1710-1 - Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Distinctively colored hard hats or hard caps... Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color from those worn by experienced miners shall be worn at...

30 CFR 77.1710-1 - Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced...

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Distinctively colored hard hats or hard caps... Distinctively colored hard hats or hard caps; identification for newly employed, inexperienced miners. Hard hats or hard caps distinctively different in color from those worn by experienced miners shall be worn at...

Percolation in suspensions of hard nanoparticles: From spheres to needles

NASA Astrophysics Data System (ADS)

Schilling, Tanja; Miller, Mark A.; van der Schoot, Paul

2015-09-01

We investigate geometric percolation and scaling relations in suspensions of nanorods, covering the entire range of aspect ratios from spheres to extremely slender needles. A new version of connectedness percolation theory is introduced and tested against specialised Monte Carlo simulations. The theory accurately predicts percolation thresholds for aspect ratios of rod length to width as low as 10. The percolation threshold for rod-like particles of aspect ratios below 1000 deviates significantly from the inverse aspect ratio scaling prediction, thought to be valid in the limit of infinitely slender rods and often used as a rule of thumb for nanofibres in composite materials. Hence, most fibres that are currently used as fillers in composite materials cannot be regarded as practically infinitely slender for the purposes of percolation theory. Comparing percolation thresholds of hard rods and new benchmark results for ideal rods, we find that i) for large aspect ratios, they differ by a factor that is inversely proportional to the connectivity distance between the hard cores, and ii) they approach the slender rod limit differently.

3D MHD Simulations of Radial Wire Array Z-pinches

NASA Astrophysics Data System (ADS)

Niasse, N.; Chittenden, J. P.; Bland, S. N.; Suzuki-Vidal, F. A.; Hall, G. N.; Lebedev, S. V.; Calamy, H.; Zucchini, F.; Lassalle, F.; Bedoch, J. P.

2009-01-01

Recent experiments carried out on the MAGPIE (1 MA, 250 ns), OEDIPE (730 kA, 1.5 μs) and SPHINX (4 MA, 700 ns)[1] facilities have shown the relatively high level of scalability of the Radial Wire Array Z-pinches. These configurations where the wires stretch radially outwards from a central cathode offer numerous advantages over standard cylindrical arrays. In particular, imploding in a very stable and compact way, they seem suitable for coupling to small scale hohlraums. Making use of the 3D resistive magneto-hydrodynamic code GORGON[2] developed at Imperial College, the dynamic of the radial wire arrays is investigated. Influence of the cathode hotspots and wires angle on the x-ray emissions is also discussed. Comparison with experiments is offered to validate the numerical studies.

Effect of the Mandibular Orthopedic Repositioning Appliance (MORA) on Forearm Muscle Activation and Grasping Power during Pinch and Hook Grip.

PubMed

Lee, Sang-Yeol; Park, Yi-Jeong; Park, Hye-Min; Bae, Hae-Jin; Yu, Min-Ji; Choi, Hee-Won; Hwang, Na-Young

2014-02-01

[Purpose] This study verified the changes in muscle activities and grasping power during maximal isometric exercise of the forearm and masseter muscle with and without a mandibular orthopedic repositioning appliance (MORA). It also offers basic data for defining the correlation of function of hand with mouth. [Methods] EMG was used to measure masticatory muscle, flexor bundle and extensor bundle activities with or without MORA while subjects performed the hook grip and pinch grip. The measuring tool used for measuring grip strength was the same as that used for measuring pinch and hook strength. The subjects were 28 healthy young adults. [Result] Muscle activity and grasping power significantly increased when wearing the MORA. [Conclusion] The result indicates that wearing MORA can increase muscle activity and grasping power of forearm and masseter muscle. We think wearing MORA might help improve the function of the forearm because it activates the function of the masseter.

Lipid-coated mannitol core microparticles for sustained release of protein.

PubMed

Wang, Bifeng; Friess, Wolfgang

2018-07-01

Parenteral sustained release systems for proteins which provide therapeutic levels over a longer period avoiding frequent administration, which preserve protein stability during manufacturing, storage and application and which are biodegradable and highly biocompatible in the body are intensively sought after. The aim of this study was to generate and study mannitol core microparticles loaded with a monoclonal antibody IgG1 and coated with lipid either hard fat or glyceryl stearate at different coating levels. The protein was stabilized with 22.5 mg/mL sucrose, 0.1% PS 80, 10 mM methionine in 10 mM His buffer pH 7.2 during the spray loading process. 30 g protein-loaded mannitol carrier microparticles were coated with 5 g, 10 g, 20 g and 30 g of lipid, respectively. Placing more lipid onto the protein-loaded microparticles reduced both burst and release rate, and the particles maintained their geometric form during the release test. The IgG1 release from microparticles covered with a hard fat layer extended up to 6 weeks. The IgG1 was released in its monomeric form and maintained its secondary structure as shown by FTIR. Incomplete release of IgG1 from glyceryl stearate-coated microparticles was observed, which may be due to the small pore sizes of the glyceryl stearate layer or a detrimental surfactant character of glyceryl stearate to protein. Hence, these hard fat-coated mannitol core microparticles have high potential for protein delivery. Copyright © 2018 Elsevier B.V. All rights reserved.

Criticality in charge-asymmetric hard-sphere ionic fluids.

PubMed

Aqua, Jean-Noël; Banerjee, Shubho; Fisher, Michael E

2005-10-01

Phase separation and criticality are analyzed in z:1 charge-asymmetric ionic fluids of equisized hard spheres by generalizing the Debye-Hückel approach combined with ionic association, cluster solvation by charged ions, and hard-core interactions, following lines developed by Fisher and Levin for the 1:1 case (i.e., the restricted primitive model). Explicit analytical calculations for 2:1 and 3:1 systems account for ionic association into dimers, trimers, and tetramers and subsequent multipolar cluster solvation. The reduced critical temperatures, Tc* (normalized by z), decrease with charge asymmetry, while the critical densities increase rapidly with . The results compare favorably with simulations and represent a distinct improvement over all current theories such as the mean spherical approximation, symmetric Poisson-Boltzmann theory, etc. For z not equal to 1, the interphase Galvani (or absolute electrostatic) potential difference, Deltaphi(T), between coexisting liquid and vapor phases is calculated and found to vanish as absolute value (T-Tc) beta when T-->Tc-with, since our approximations are classical, beta = (1/2). Above Tc, the compressibility maxima and so-called k-inflection loci (which aid the fast and accurate determination of the critical parameters) are found to exhibit a strong z dependence.

Diagnosing x-ray power and energy of tungsten wire array z-pinch with a flat spectral response x-ray diode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Kun-lun; Ren, Xiao-dong; Huang, Xian-bin, E-mail: caephxb2003@aliyun.com

2015-11-15

Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter tomore » yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%.« less

Grounding by Attention Simulation in Peripersonal Space: Pupils Dilate to Pinch Grip But Not Big Size Nominal Classifier.

PubMed

Lobben, Marit; Bochynska, Agata

2018-03-01

Grammatical categories represent implicit knowledge, and it is not known if such abstract linguistic knowledge can be continuously grounded in real-life experiences, nor is it known what types of mental states can be simulated. A former study showed that attention bias in peripersonal space (PPS) affects reaction times in grammatical congruency judgments of nominal classifiers, suggesting that simulated semantics may include reenactment of attention. In this study, we contrasted a Chinese nominal classifier used with nouns denoting pinch grip objects with a classifier for nouns with big object referents in a pupil dilation experiment. Twenty Chinese native speakers read grammatical and ungrammatical classifier-noun combinations and made grammaticality judgment while their pupillary responses were measured. It was found that their pupils dilated significantly more to the pinch grip classifier than to the big object classifier, indicating attention simulation in PPS. Pupil dilations were also significantly larger with congruent trials on the whole than in incongruent trials, but crucially, congruency and classifier semantics were independent of each other. No such effects were found in controls. Copyright © 2017 Cognitive Science Society, Inc.

Fluctuation reduction and enhanced confinement in the MST reversed-field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chapman, Brett Edward

1997-10-01

Plasmas with a factor of ≥3 improvement in energy confinement have been achieved in the MST reversed-field pinch (RFP). These plasmas occur spontaneously, following sawtooth crashes, subject to constraints on, eg, toroidal magnetic field reversal and wall conditioning. Possible contributors to the improved confinement include a reduction of core-resonant, global magnetic fluctuations and a reduction of electrostatic fluctuations over the entire plasma edge. One feature of these plasmas is a region of strong ExB flow shear in the edge. Never before observed in conjunction with enhanced confinement in the RFP, such shear is common in enhanced confinement discharges in tokamaks and stellarators. Another feature of these plasmas is a new type of discrete dynamo event. Like sawtooth crashes, a common form of discrete dynamo, these events correspond to bursts of edge parallel current. The reduction of electrostatic fluctuations in these plasmas occurs within and beyond the region of strong ExB flow shear, similar to what is observed in tokamaks and stellarators. However, the reductions in the MST include fluctuations whose correlation lengths are larger than the width of the shear region. The reduction of the global magnetic fluctuations is most likely due to flattening of the μ=μ 0more » $$\\vec{J}$$∙$$\\vec{B}$$/B 2 profile. Flattening can occur, eg, due to the new type of discrete dynamo event and reduced edge resistivity. Enhanced confinement plasmas are also achieved in the MST when auxiliary current is applied to flatten the μ profile and reduce magnetic fluctuations. Unexpectedly, these plasmas also exhibit a region (broader than in the case above) of strong ExB flow shear in the edge, an edge-wide reduction of electrostatic fluctuations, and the new type of discrete dynamo event. Auxiliary current drive has historically been viewed as the principal route to fusion reactor viability for the RFP.« less

Improved Thermoplastic/Iron-Particle Transformer Cores

NASA Technical Reports Server (NTRS)

Wincheski, Russell A.; Bryant, Robert G.; Namkung, Min

2004-01-01

A method of fabricating improved transformer cores from composites of thermoplastic matrices and iron-particles has been invented. Relative to commercially available laminated-iron-alloy transformer cores, the cores fabricated by this method weigh less and are less expensive. Relative to prior polymer-matrix/ iron-particle composite-material transformer cores, the cores fabricated by this method can be made mechanically stronger and more magnetically permeable. In addition, whereas some prior cores have exhibited significant eddy-current losses, the cores fabricated by this method exhibit very small eddy-current losses. The cores made by this method can be expected to be attractive for use in diverse applications, including high-signal-to-noise transformers, stepping motors, and high-frequency ignition coils. The present method is a product of an experimental study of the relationships among fabrication conditions, final densities of iron particles, and mechanical and electromagnetic properties of fabricated cores. Among the fabrication conditions investigated were molding pressures (83, 104, and 131 MPa), and molding temperatures (250, 300, and 350 C). Each block of core material was made by uniaxial-compression molding, at the applicable pressure/temperature combination, of a mixture of 2 weight percent of LaRC (or equivalent high-temperature soluble thermoplastic adhesive) with 98 weight percent of approximately spherical iron particles having diameters in the micron range. Each molded block was cut into square cross-section rods that were used as core specimens in mechanical and electromagnetic tests. Some of the core specimens were annealed at 900 C and cooled slowly before testing. For comparison, a low-carbon-steel core was also tested. The results of the tests showed that density, hardness, and rupture strength generally increased with molding pressure and temperature, though the correlation was rather weak. The weakness of the correlation was attributed to

Applications of liquid state physics to the earth's core

NASA Technical Reports Server (NTRS)

Stevenson, D. J.

1980-01-01

New results derived for application to the earth's outer core using the modern theory of liquids and the hard-sphere model of liquid structure are presented. An expression derived in terms of the incompressibility and pressure is valid for a high-pressure liquid near its melting point, provided that the pressure is derived from a strongly repulsive pair potential; a relation derived between the melting point and density leads to a melting curve law of essentially the same form as Lindemann's law. Finally, it is shown that the 'core paradox' of Higgins and Kennedy (1971) can occur only if the Gruneisen parameter is smaller than 2/3, and this constant is larger than this value in any liquid for which the pair potential is strongly repulsive.

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Evolution of skin grafting for treatment of burns: Reverdin pinch grafting to Tanner mesh grafting and beyond.

PubMed

Singh, Mansher; Nuutila, Kristo; Collins, K C; Huang, Anne

2017-09-01

Skin grafting is the current standard care in the treatment of full thickness burns. It was first described around 1500 BC but the vast majority of advancements have been achieved over the past 200 years. An extensive literature review was conducted on Pubmed, Medline and Google Scholar researching the evolution of skin grafting techniques. The authors concentrated on the major landmarks of skin grafting and also provide an overview of ongoing research efforts in this field. The major innovations of skin grafting include Reverdin pinch grafting, Ollier grafting, Thiersch grafting, Wolfe grafting, Padgett dermatome and modifications, Meek-wall microdermatome and Tanner mesh grafting. A brief description of the usage, advantages and limitations of each technique is included in the manuscript. Skin grafting technique have evolved significantly over past 200 years from Reverdin pinch grafting to modern day meshed skin grafts using powered dermatome. Increasing the expansion ratio and improving the cosmetic and functional outcome are the main focus of ongoing skin grafting research and emerging techniques (such as Integra ® , Recell ® , Xpansion ® ) are showing promise. Copyright © 2017 Elsevier Ltd and ISBI. All rights reserved.

Controlling Rayleigh-Taylor Instabilities in Magnetically Driven Solid Metal Shells by Means of a Dynamic Screw Pinch

DOE PAGES

Schmit, P. F.; Velikovich, A. L.; McBride, R. D.; ...

2016-11-11

Magnetically driven implosions of solid metal shells are an effective vehicle to compress materials to extreme pressures and densities. Rayleigh-Taylor instabilities (RTI) are ubiquitous, yet typically undesired features in all such experiments where solid materials are rapidly accelerated to high velocities. In cylindrical shells (“liners”), the magnetic field driving the implosion can exacerbate the RTI. Here, we suggest an approach to implode solid metal liners enabling a remarkable reduction in the growth of magnetized RTI (MRTI) by employing a magnetic drive with a tilted, dynamic polarization, forming a dynamic screw pinch. Our calculations, based on a self-consistent analytic framework, demonstratemore » that the cumulative growth of the most deleterious MRTI modes may be reduced by as much as 1 to 2 orders of magnitude. One key application of this technique is to generate increasingly stable, higher-performance implosions of solid metal liners to achieve fusion [M. R. Gomez et al., Phys. Rev. Lett. 113, 155003 (2014)]. Finally, we weigh the potentially dramatic benefits of the solid liner dynamic screw pinch against the experimental tradeoffs required to achieve the desired drive field history and identify promising designs for future experimental and computational studies.« less

Dynamic hardness of metals

NASA Astrophysics Data System (ADS)

Liang, Xuecheng

Dynamic hardness (Pd) of 22 different pure metals and alloys having a wide range of elastic modulus, static hardness, and crystal structure were measured in a gas pulse system. The indentation contact diameter with an indenting sphere and the radius (r2) of curvature of the indentation were determined by the curve fitting of the indentation profile data. r 2 measured by the profilometer was compared with that calculated from Hertz equation in both dynamic and static conditions. The results indicated that the curvature change due to elastic recovery after unloading is approximately proportional to the parameters predicted by Hertz equation. However, r 2 is less than the radius of indenting sphere in many cases which is contradictory to Hertz analysis. This discrepancy is believed due to the difference between Hertzian and actual stress distributions underneath the indentation. Factors which influence indentation elastic recovery were also discussed. It was found that Tabor dynamic hardness formula always gives a lower value than that directly from dynamic hardness definition DeltaE/V because of errors mainly from Tabor's rebound equation and the assumption that dynamic hardness at the beginning of rebound process (Pr) is equal to kinetic energy change of an impact sphere over the formed crater volume (Pd) in the derivation process for Tabor's dynamic hardness formula. Experimental results also suggested that dynamic to static hardness ratio of a material is primarily determined by its crystal structure and static hardness. The effects of strain rate and temperature rise on this ratio were discussed. A vacuum rotating arm apparatus was built to measure Pd at 70, 127, and 381 mum sphere sizes, these results exhibited that Pd is highly depended on the sphere size due to the strain rate effects. P d was also used to substitute for static hardness to correlate with abrasion and erosion resistance of metals and alloys. The particle size effects observed in erosion were

Staged Z-pinch Experiments on Cobra and Zebra

NASA Astrophysics Data System (ADS)

Wessel, Frank J.; Anderson, A.; Banasek, J. T.; Byvank, T.; Conti, F.; Darling, T. W.; Dutra, E.; Glebov, V.; Greenly, J.; Hammer, D. A.; Potter, W. M.; Rocco, S. V.; Ross, M. P.; Ruskov, E.; Valenzuela, J.; Beg, F.; Covington, A.; Narkis, J.; Rahman, H. U.

2017-10-01

A Staged Z-pinch (SZP), configured as a pre-magnetized, high-Z (Ar, or Kr) annular liner imploding onto a low-Z (H, or D) target, was tested on the Cornell University, Cobra Facility and the University of Nevada, Reno, Zebra Facility; each characterized similarly by a nominal 1-MA current and 100-ns risetime while possessing different diagnostic packages. XUV-fast imaging reveals that the SZP implosion dynamics is similar on both machines and that it is more stable with an axial (Bz) magnetic field, a target, or both, than without. On Zebra, where neutron production is possible, reproducible thermonuclear (DD) yields were recorded at levels in excess of 109/shot. Flux compression in the SZP is also expected to produce magnetic field intensities of the order of kilo-Tesla. Thus, the DD reaction produced tritions should also yield secondary DT neutrons. Indeed, secondaries are measured above the noise threshold at levels approaching 106/shot. Funded by the Advanced Research Projects Agency - Energy, under Grant Number DE-AR0000569.

Evaluation of Internal Brushing on Pinch Weld Quality

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korinko, P

2005-12-01

Post machining operations such as borescope inspection can cause linear indications down the length of the bore of fill stems. Often these indications are removed or obscured using rotary wire brushing. This study evaluated the effect this mechanical operation may have on pinch weld quality when relatively cold welds were made. A total of four stems with two levels of brushing of both Type 304L and 21-6-9 stainless steels were tested. In addition, two each of the Type 304L stems were Nitradd cleaned and the other two were aqueously cleaned; all four 21-6-9 stems were aqueously cleaned. All of themore » brushed stem areas exhibited more surface anomalies based on borescope evaluation. On average, the bond rating was a higher value (worse) for the brushed areas than the unadulterated areas for both Type 304L and 21-6-9 stems. The test method used may have biased the results towards a lesser quality bond for the brushed areas so additional testing is recommended.« less

Electron-Beam-Pinch Experiment at Harry Diamond Laboratories: Providing for a High-Dose-Rate Flash X-Ray Facility for Transient Radiation Effects on Electronics (TREE) Testing of Pieceparts

DTIC Science & Technology

1991-08-01

The outer perimeter of the converter was attached to the C ring with copper tape. Thermoluminescent dosimeters ( TLDs )* and a coaxial x-ray diode...CaF2) TLDs in Al pillboxes for electronic equilibrium. 7 Figure 2. HIFX beam 400 pinch at 0.05 Torr, Y4 38o in. from face. _360O E 340 d 320 - .~. 300...AD-A239 558Hu D L M-91 -111, 1𔃻, 1 ,11I Aucr,, 1991 Electron -Beam-Pinch Experiment at Harry Diamond Laboratories: Providing for a High-Dose-Rate

Two-fluid and finite Larmor radius effects on helicity evolution in a plasma pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sauppe, J. P., E-mail: jpsauppe@gmail.com; Department of Physics, University of Wisconsin-Madison, 1150 University Avenue, Madison, Wisconsin 53706; Sovinec, C. R., E-mail: csovinec@wisc.edu

2016-03-15

The evolution of magnetic energy, helicity, and hybrid helicity during nonlinear relaxation of a driven-damped plasma pinch is compared in visco-resistive magnetohydrodynamics and two-fluid models with and without the ion gyroviscous stress tensor. Magnetic energy and helicity are supplied via a boundary electric field which initially balances the resistive dissipation, and the plasma undergoes multiple relaxation events during the nonlinear evolution. The magnetic helicity is well conserved relative to the magnetic energy over each event, which is short compared with the global resistive diffusion time. The magnetic energy decreases by roughly 1.5% of its initial value over a relaxation event,more » while the magnetic helicity changes by at most 0.2% of the initial value. The hybrid helicity is dominated by magnetic helicity in low-β pinch conditions and is also well conserved. Differences of less than 1% between magnetic helicity and hybrid helicity are observed with two-fluid modeling and result from cross helicity evolution. The cross helicity is found to change appreciably due to the first-order finite Larmor radius effects which have not been included in contemporary relaxation theories. The plasma current evolves towards the flat parallel current state predicted by Taylor relaxation theory but does not achieve it. Plasma flow develops significant structure for two-fluid models, and the flow perpendicular to the magnetic field is much more substantial than the flow along it.« less

Hard-on-hard lubrication in the artificial hip under dynamic loading conditions.

PubMed

Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S; Heitzmann, Daniel W W; Kretzer, J Philippe

2013-01-01

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal.

Hard-on-Hard Lubrication in the Artificial Hip under Dynamic Loading Conditions

PubMed Central

Sonntag, Robert; Reinders, Jörn; Rieger, Johannes S.; Heitzmann, Daniel W. W.; Kretzer, J. Philippe

2013-01-01

The tribological performance of an artificial hip joint has a particularly strong influence on its success. The principle causes for failure are adverse short- and long-term reactions to wear debris and high frictional torque in the case of poor lubrication that may cause loosening of the implant. Therefore, using experimental and theoretical approaches models have been developed to evaluate lubrication under standardized conditions. A steady-state numerical model has been extended with dynamic experimental data for hard-on-hard bearings used in total hip replacements to verify the tribological relevance of the ISO 14242-1 gait cycle in comparison to experimental data from the Orthoload database and instrumented gait analysis for three additional loading conditions: normal walking, climbing stairs and descending stairs. Ceramic-on-ceramic bearing partners show superior lubrication potential compared to hard-on-hard bearings that work with at least one articulating metal component. Lubrication regimes during the investigated activities are shown to strongly depend on the kinematics and loading conditions. The outcome from the ISO gait is not fully confirmed by the normal walking data and more challenging conditions show evidence of inferior lubrication. These findings may help to explain the differences between the in vitro predictions using the ISO gait cycle and the clinical outcome of some hard-on-hard bearings, e.g., using metal-on-metal. PMID:23940772

The column density distribution of hard X-ray radio galaxies

NASA Astrophysics Data System (ADS)

Panessa, F.; Bassani, L.; Landi, R.; Bazzano, A.; Dallacasa, D.; La Franca, F.; Malizia, A.; Venturi, T.; Ubertini, P.

2016-09-01

In order to investigate the role of absorption in active galactic nuclei (AGN) with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/Imager on Board the Integral Satellite (IBIS) and Swift/The Burst Alert Telescope (BAT) AGN catalogues (˜7-10 per cent of the total AGN population). The 64 radio galaxies have a typical FR II radio morphology and are characterized by high 20-100 keV luminosities (from 1042 to 1046 erg s-1) and high Eddington ratios (log LBol/LEdd typically larger than ˜0.01). The observed fraction of absorbed AGN (NH > 1022 cm-2) is around 40 per cent among the total sample, and ˜75 per cent among type 2 AGN. The majority of obscured AGN are narrow-line objects, while unobscured AGN are broad-line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ˜2-3 per cent, in comparison with the 5-7 per cent found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non-radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

Investigation of a staged plasma-focus apparatus. [pinch construction and current sheet dynamics investigation

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.; Harries, W. L.

1978-01-01

A new staged plasma-focus geometry combining two Mather-type plasma-focus guns was constructed, and the current-sheet dynamics were investigated. The production of simultaneous pairs of plasma foci was achieved. The intensities of X-ray and fusion-neutron emission were measured and found to agree with the scaling law for a plasma focus. Advantages of this new geometry include the possibility of using plasma-focus type pinches in multiple arrays at power levels beyond the validity regime of the current scaling law for a single gun.

Spontaneous Generation of a Sheared Plasma Rotation in a Field-Reversed θ-Pinch Discharge

NASA Astrophysics Data System (ADS)

Omelchenko, Y. A.; Karimabadi, H.

2012-08-01

By conducting two-dimensional hybrid simulations of an infinitely long field-reversed θ-pinch discharge we discover a new type of plasma rotation, which rapidly develops at the plasma edge in the ion diamagnetic direction due to the self-consistent generation of a Hall-driven radial electric field. This effect is different from the previously identified end-shorting and particle-loss mechanisms. We also demonstrate flutelike perturbations frequently inferred in experiments and show that in the absence of axial contraction effects they may quickly alter the toroidal symmetry of the plasma.

Collective acceleration of ions in picosecond pinched electron beams

NASA Astrophysics Data System (ADS)

Baryshnikov, V. I.; Paperny, V. L.; Shipayev, I. V.

2017-10-01

Сharacteristics of intense electron-ion beams emitted by a high-voltage (280 kV) electron accelerator with a pulse duration of 200 ps and current 5 kA are studied. The capture phenomena and the subsequent collective acceleration of multi charged ions of the cathode material by the electric field of the electron beam are observed. It is shown that the electron-ion beam diameter does not exceed 30 µm therein in the case of lighter ions, and the decay of the pinched beam occurs at a shorter distance from the cathode. It is established that the ions of the cathode material Tin+ captured by the electron beam are accelerated up to an energy of  ⩽10 MeV, and the ion fluence reaches 1017 ion cm-2 in the pulse. These ions are effectively embedded into the lattice sites of the irradiated substrate (sapphire crystal), forming the luminescent areas of the micron scale.

Production of dense plasmas in a hypocycloidal pinch apparatus

NASA Technical Reports Server (NTRS)

Lee, J. H.; Mcfarland, D. R.; Hohl, F.

1977-01-01

A high-power pinch apparatus consisting of disk electrodes was developed, and diagnostic measurements to study its mechanism of dense plasma production have been made. The collapse fronts of the current sheets are well organized, and dense plasma foci are produced on the axis with radial stability in excess of 5 microsec. A plasma density greater than 10 to the 18th power per cu cm is determined with Stark broadening and CO2 laser absorption. Essentially complete absorption of a high-energy CO2 laser beam has been observed. A plasma temperature of approximately 1 keV is measured with differential transmission of soft X-rays through thin foils. The advantages of this apparatus over the coaxial plasma focus are improvements in (1) plasma volume, (2) stability, (3) containment time, (4) access to additional heating by laser or electron beams, and (5) the possibility of scaling up to a multiple array for high-power operation.

Effects of Controlled-Release Fertilizer on Leaf Area Index and Fruit Yield in High-Density Soilless Tomato Culture Using Low Node-Order Pinching

PubMed Central

Kinoshita, Takafumi; Yano, Takayoshi; Sugiura, Makoto; Nagasaki, Yuji

2014-01-01

To further development of a simplified fertigation system using controlled-release fertilizers (CRF), we investigated the effects of differing levels of fertilizers and plant density on leaf area index (LAI), fruit yields, and nutrient use in soilless tomato cultures with low node-order pinching and high plant density during spring-summer (SS), summer-fall (SF), and fall-winter (FW) seasons. Plants were treated with 1 of 3 levels of CRF in a closed system, or with liquid fertilizer (LF) with constant electrical conductivity (EC) in a drip-draining system. Two plant densities were examined for each fertilizer treatment. In CRF treatments, LAI at pinching increased linearly with increasing nutrient supply for all cropping seasons. In SS, both light interception by plant canopy at pinching and total marketable fruit yield increased linearly with increasing LAI up to 6 m2·m−2; the maximization point was not reached for any of the treatments. In FW, both light interception and yield were maximized at an LAI of approximately 4. These results suggest that maximizing the LAI in SS and FW to the saturation point for light interception is important for increasing yield. In SF, however, the yield maximized at an LAI of approximately 3, although the light interception linearly increased with increasing LAI, up to 4.5. According to our results, the optimal LAI at pinching may be 6 in SS, 3 in SF, and 4 in FW. In comparing LAI values with similar fruit yield, we found that nutrient supply was 32−46% lower with the CRF method than with LF. In conclusion, CRF application in a closed system enables growers to achieve a desirable LAI to maximize fruit yield with a regulated amount of nutrient supply per unit area. Further, the CRF method greatly reduced nutrient use without decreasing fruit yield at similar LAIs, as compared to the LF method. PMID:25402478

Research in the Hard Sciences, and in Very Hard "Softer" Domains

ERIC Educational Resources Information Center

Phillips, D. C.

2014-01-01

The author of this commentary argues that physical scientists are attempting to advance knowledge in the so-called hard sciences, whereas education researchers are laboring to increase knowledge and understanding in an "extremely hard" but softer domain. Drawing on the work of Popper and Dewey, this commentary highlights the relative…

Core-core and core-valence correlation

NASA Technical Reports Server (NTRS)

Bauschlicher, Charles W., Jr.; Langhoff, Stephen R.; Taylor, Peter R.

1988-01-01

The effect of (1s) core correlation on properties and energy separations was analyzed using full configuration-interaction (FCI) calculations. The Be 1 S - 1 P, the C 3 P - 5 S and CH+ 1 Sigma + or - 1 Pi separations, and CH+ spectroscopic constants, dipole moment and 1 Sigma + - 1 Pi transition dipole moment were studied. The results of the FCI calculations are compared to those obtained using approximate methods. In addition, the generation of atomic natural orbital (ANO) basis sets, as a method for contracting a primitive basis set for both valence and core correlation, is discussed. When both core-core and core-valence correlation are included in the calculation, no suitable truncated CI approach consistently reproduces the FCI, and contraction of the basis set is very difficult. If the (nearly constant) core-core correlation is eliminated, and only the core-valence correlation is included, CASSCF/MRCI approached reproduce the FCI results and basis set contraction is significantly easier.

Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.

PubMed

Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao

2010-12-28

The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.

Must "Hard Problems" Be Hard?

ERIC Educational Resources Information Center

Kolata, Gina

1985-01-01

To determine how hard it is for computers to solve problems, researchers have classified groups of problems (polynomial hierarchy) according to how much time they seem to require for their solutions. A difficult and complex proof is offered which shows that a combinatorial approach (using Boolean circuits) may resolve the problem. (JN)

Experimental study of z-pinch driven radiative shocks in low density gases

NASA Astrophysics Data System (ADS)

Skidmore, Jonathan; Lebedev, S. V.; Suzuki-Vidal, F.; Swadling, G.; Bland, S. N.; Burdiak, G.; Chittenden, J. P.; de Grouchy, P.; Hall, G. N.; Pickworth, L.; Suttle, L.; Bennett, M.; Ciardi, A.

2012-10-01

Results of experiments performed on MAGPIE pulsed power facility (1.4MA, 250ns) will be presented. Shocks with velocities of 50-70km/s are driven in Ar, Xe and He gases at density ˜10-5g/cc using radial foil z-pinch configuration [1]. Measurements of the structure of the shocks obtained with laser probing will be presented and observations of the development of instabilities will be discussed. It was found that the structure of the shocks and the development of instabilities strongly depend on the rate of radiative cooling, increasing for gases with higher atomic numbers.[4pt] [1] F. Suzuki-Vidal et al., PoP 19, 022708 (2012)

Core-shell carbon nanosphere-TiO2 composite and hollow TiO2 nanospheres prepared by atomic layer deposition

NASA Astrophysics Data System (ADS)

Bakos, L. P.; Justh, N.; Hernádi, K.; Kiss, G.; Réti, B.; Erdélyi, Z.; Parditka, B.; Szilágyi, I. M.

2016-10-01

Core-shell carbon-TiO2 composite and hollow TiO2 nanospheres were prepared using carbon nanospheres as hard-templates, coating them with TiO2 using atomic layer deposition, and subsequent burning out of the carbon cores. The bare carbon, the composite carbon-TiO2 and the hollow TiO2 nanospheres were characterized with TG/DTA-MS, FTIR, XRD and SEM-EDX.

Inhomogeneous hard homonuclear molecules

NASA Astrophysics Data System (ADS)

Quintana, Jacqueline

A review is given of some features of theories for inhomogeneous fluids of nonspherical molecules that take as input the direct correlation function of the corresponding homogeneous system. Two different methods are described for defining the structure of hard homonuclear molecules close to a hard planar wall. A spherical harmonics expanison (SHE) within the integral equation (IE) method is presented and, for comparison, a version of density functional theory for orientable hard bodies. In both cases the Pynn-Lado model is employed and a comparison is made with Monte Carlo data. The results indicate that for hard molecules the IE approach does not always capture the effects of orientation due to the characteristics of the SHE for the step function. This disadvantage is particularly true in the case of the orientationally averaged density profile.

Fabrication of polyacrylate core-shell nanoparticles via spray drying method

NASA Astrophysics Data System (ADS)

Chen, Pengpeng; Cheng, Zenghui; Chu, Fuxiang; Xu, Yuzhi; Wang, Chunpeng

2016-05-01

Fine polyacrylate particles are thought to be environmental plastisols for car industry. However, these particles are mainly dried through demulsification of the latexes, which is not reproducible and hard to be scaled up. In this work, a spray drying method had been applied to the plastisols-used acrylate latex. By adjusting the core/shell ratio, spray drying process of the latex was fully studied. Scanning electronic microscopy observation of the nanoparticles before and after spray drying indicated that the core-shell structures could be well preserved and particles were well separated by spray drying if the shell was thick enough. Otherwise, the particles fused into each other and core-shell structures were destroyed. Polyacrylate plastisols were developed using diisononylphthalate as a plasticizer, and plastigels were obtained after heat treatment of the sols. Results showed that the shell thickness also had a great influence on the storage stability of the plastisols and mechanical properties of the plastigels.

Constraining axion-like-particles with hard X-ray emission from magnetars

NASA Astrophysics Data System (ADS)

Fortin, Jean-François; Sinha, Kuver

2018-06-01

Axion-like particles (ALPs) produced in the core of a magnetar will convert to photons in the magnetosphere, leading to possible signatures in the hard X-ray band. We perform a detailed calculation of the ALP-to-photon conversion probability in the magnetosphere, recasting the coupled differential equations that describe ALP-photon propagation into a form that is efficient for large scale numerical scans. We show the dependence of the conversion probability on the ALP energy, mass, ALP-photon coupling, magnetar radius, surface magnetic field, and the angle between the magnetic field and direction of propagation. Along the way, we develop an analytic formalism to perform similar calculations in more general n-state oscillation systems. Assuming ALP emission rates from the core that are just subdominant to neutrino emission, we calculate the resulting constraints on the ALP mass versus ALP-photon coupling space, taking SGR 1806-20 as an example. In particular, we take benchmark values for the magnetar radius and core temperature, and constrain the ALP parameter space by the requirement that the luminosity from ALP-to-photon conversion should not exceed the total observed luminosity from the magnetar. The resulting constraints are competitive with constraints from helioscope experiments in the relevant part of ALP parameter space.

Pinched flow coupled shear-modulated inertial microfluidics for high-throughput rare blood cell separation.

PubMed

Bhagat, Ali Asgar S; Hou, Han Wei; Li, Leon D; Lim, Chwee Teck; Han, Jongyoon

2011-06-07

Blood is a highly complex bio-fluid with cellular components making up >40% of the total volume, thus making its analysis challenging and time-consuming. In this work, we introduce a high-throughput size-based separation method for processing diluted blood using inertial microfluidics. The technique takes advantage of the preferential cell focusing in high aspect-ratio microchannels coupled with pinched flow dynamics for isolating low abundance cells from blood. As an application of the developed technique, we demonstrate the isolation of cancer cells (circulating tumor cells (CTCs)) spiked in blood by exploiting the difference in size between CTCs and hematologic cells. The microchannel dimensions and processing parameters were optimized to enable high throughput and high resolution separation, comparable to existing CTC isolation technologies. Results from experiments conducted with MCF-7 cells spiked into whole blood indicate >80% cell recovery with an impressive 3.25 × 10(5) fold enrichment over red blood cells (RBCs) and 1.2 × 10(4) fold enrichment over peripheral blood leukocytes (PBL). In spite of a 20× sample dilution, the fast operating flow rate allows the processing of ∼10(8) cells min(-1) through a single microfluidic device. The device design can be easily customized for isolating other rare cells from blood including peripheral blood leukocytes and fetal nucleated red blood cells by simply varying the 'pinching' width. The advantage of simple label-free separation, combined with the ability to retrieve viable cells post enrichment and minimal sample pre-processing presents numerous applications for use in clinical diagnosis and conducting fundamental studies.

Experimental development of rod pinch diode radiographic source using modified KALI 1000 pulsed power system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Satyanarayana, N.; Basu, Shibaji; Rajawat, R.K., E-mail: satya_3026@yahoo.com

2014-07-01

This paper highlights the development of Rod Pinch (RP) diode for flash X-ray generation as intense radiographic source at BARC, Vizag. The typical RP diode employed used a small diameter (1-2 mm) anode rod extended through a cathode circular aperture (5-6 mm inner diameter). The diode chamber is maintained at 10{sup -5} Torr vacuum by a rotary backed diffusion pump. Experiments performed on a modified Kali 1000 Pulsed Power System (300 kV, 30 kA, 100 ns) were aimed at optimizing the source by maximizing the figure of merit (dose @ 1m in rad/spot diameter{sup 2} in mm{sup 2}) with minimizingmore » of the diode impedance. The typical electron beam parameters used in the experiments are 240-270 kV, 20-25 kA, 100 ns, with a few hundreds of kA/cm{sup 2} current density. The optimization resulted in a configuration with tungsten anode rod having dimensions of a 1.6 mm diameter, tapering extension length 5-25 mm beyond the graphite cathode aperture (Cathode disk ID = 5 mm, thickness = 3mm) to produce a radiation dose of 150-200 milli rad at 1 m distance having an estimated spot-size of 1-2 mm. The radiation emitted from a rod-pinch diode is measured using Thermoluminescence dosimeters (TLDs) at an angular interval of 15° on either side of the rod in horizontal and vertical plane. (author)« less

Hard Water and Soft Soap: Dependence of Soap Performance on Water Hardness

ERIC Educational Resources Information Center

Osorio, Viktoria K. L.; de Oliveira, Wanda; El Seoud, Omar A.; Cotton, Wyatt; Easdon, Jerry

2005-01-01

The demonstration of the performance of soap in different aqueous solutions, which is due to water hardness and soap formulation, is described. The demonstrations use safe, inexpensive reagents and simple glassware and equipment, introduce important everyday topics, stimulates the students to consider the wider consequences of water hardness and…

Radiation hardness of Ce-doped sol-gel silica fibers for high energy physics applications.

PubMed

Cova, Francesca; Moretti, Federico; Fasoli, Mauro; Chiodini, Norberto; Pauwels, Kristof; Auffray, Etiennette; Lucchini, Marco Toliman; Baccaro, Stefania; Cemmi, Alessia; Bártová, Hana; Vedda, Anna

2018-02-15

The results of irradiation tests on Ce-doped sol-gel silica using x- and γ-rays up to 10 kGy are reported in order to investigate the radiation hardness of this material for high-energy physics applications. Sol-gel silica fibers with Ce concentrations of 0.0125 and 0.05 mol. % are characterized by means of optical absorption and attenuation length measurements before and after irradiation. The two different techniques give comparable results, evidencing the formation of a main broad radiation-induced absorption band, peaking at about 2.2 eV, related to radiation-induced color centers. The results are compared with those obtained on bulk silica. This study reveals that an improvement of the radiation hardness of Ce-doped silica fibers can be achieved by reducing Ce content inside the fiber core, paving the way for further material development.

Effects of exogenous galanin on neuropathic pain state and change of galanin and its receptors in DRG and SDH after sciatic nerve-pinch injury in rat.

PubMed

Xu, Xiaofeng; Yang, Xiangdong; Zhang, Ping; Chen, Xiuying; Liu, Huaxiang; Li, Zhenzhong

2012-01-01

A large number of neuroanatomical, neurophysiologic, and neurochemical mechanisms are thought to contribute to the development and maintenance of neuropathic pain. However, mechanisms responsible for neuropathic pain have not been completely delineated. It has been demonstrated that neuropeptide galanin (Gal) is upregulated after injury in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) where it plays a predominantly antinociceptive role. In the present study, sciatic nerve-pinch injury rat model was used to determine the effects of exogenous Gal on the expression of the Gal and its receptors (GalR1, GalR2) in DRG and SDH, the alterations of pain behavior, nerve conduction velocity (NCV) and morphology of sciatic nerve. The results showed that exogenous Gal had antinociceptive effects in this nerve-pinch injury induced neuropathic pain animal model. It is very interesting that Gal, GalR1 and GalR2 change their expression greatly in DRG and SDH after nerve injury and intrathecal injection of exougenous Gal. Morphological investigation displays a serious damage after nerve-pinch injury and an amendatory regeneration after exogenous Gal treatment. These findings imply that Gal, via activation of GalR1 and/or GalR2, may have neuroprotective effects in reducing neuropathic pain behaviors and improving nerve regeneration after nerve injury.

Studying Hardness Meter Spring Strength to Understand Hardness Distribution on Body Surfaces.

PubMed

Arima, Yoshitaka

2017-10-01

For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK). We measured the hardness of three-layered sheets of six types of gel sheets (90 mm × 60 mm × 6 mm) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart. Using 4.90 N spring strength, we could obtain measurement loads of ≤3.0 N, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0-10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength. Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model. Copyright © 2017. Published by Elsevier B.V.

If it’s pinched it’s a memristor

NASA Astrophysics Data System (ADS)

Chua, Leon

2014-10-01

This paper presents an in-depth review of the memristor from a rigorous circuit-theoretic perspective, independent of the material the device is made of. From an experimental perspective, a memristor is best defined as any two-terminal device that exhibits a pinched hysteresis loop in the voltage-current plane when driven by any periodic voltage or current signal that elicits a periodic response of the same frequency. This definition greatly broadens the scope of memristive devices to encompass even non-semiconductor devices, both organic and inorganic, from many unrelated disciplines, including biology, botany, brain science, etc. For pedagogical reasons, the broad terrain of memristors is partitioned into three classes of increasing generality, dubbed Ideal Memristors, Generic Memristors, and Extended Memristors. Each class is distinguished from the others via unique fingerprints and signatures. This paper clarifies many confusing issues, such as non-volatility, dc V-I curves, high-frequency v-i curves, local activity, as well as nonlinear dynamical and bifurcation phenomena that are the hallmarks of memristive devices. Above all, this paper addresses several fundamental issues and questions that many memristor researchers do not comprehend but are afraid to ask.

Towards Reconfigurable, Separable and Hard Real-Time Hybrid Simulation and Test Systems

NASA Astrophysics Data System (ADS)

Quartier, F.; Delatte, B.; Joubert, M.

2009-05-01

Formation flight needs several new technologies, new disciplines, new approaches and above all, more concurrent engineering by more players. One of the problems to be addressed are more complex simulation and test systems that are easy to re-configure to include parts of the target hardware and that can provide sufficient power to handle simulation cores that are requiring one to two orders of magnitude more processing power than the current technology provides. Critical technologies that are already addressed by CNES and Spacebel are study model reuse and simulator reconfigurability (Basiles), model portability (SMP2) and the federation of several simulators using HLA. Two more critical issues are addressed in ongoing R&D work by CNES and Spacebel and are covered by this paper and concern the time engineering and management. The first issue concerns separability (characterisation, identification and handling of separable subsystems) and the consequences on practical systems. Experiments on the Pleiades operational simulator have shown that adding precise simulation of instruments such as Doris and the Star Tracker can be added without significantly impacting overall performance. Improved time analysis leads to better system understanding and testability. The second issue concerns architectures for distributed hybrid simulators systems that provide hard real-time capabilities and can react with a relative time precision and jitter that is in the 10 to 50 µsecond range using mainstream PC's and mainstream Operating Systems. This opens a way to make smaller economic hardware test systems that can be reconfigured to make large hardware test systems without restarting development. Although such systems were considered next to impossible till now, distributed hard real-time systems are getting in reach when modern but mainstream electronics are used and when processor cores can be isolated and reserved for real-time cores. This requires a complete rethinking of the

The effects of pre-ionization on the impurity and x-ray level in a dense plasma focus device

NASA Astrophysics Data System (ADS)

Piriaei, D.; Yousefi, H. R.; Mahabadi, T. D.; Salar Elahi, A.; Ghoranneviss, M.

2017-02-01

In this study, the effects of pre-ionization on the reduction of the impurities and non-uniformities, the increased stability of the pinch plasma, the enhancement of the total hard x-ray yield, the plasmoid x-ray yield, and the current sheath dynamics of the argon gas at different pressures in a Mather type plasma focus device were investigated. For this purpose, different shunt resistors together with two x-ray detectors were used, and the data gathered from the x-ray signals showed that the optimum shunt resistor could cause the maximum total hard and plasmoid hard x-ray emissions. Moreover, in order to calculate the average speed of the current sheath, two axial magnetic probes were used. It was revealed that the pre-ionization could increase the whole range of the emitted x-rays and produce a more uniform current sheath layer, which moved faster, and this technique could lead to the reduction of the impurities, creating a more stabilized pinched plasma, which was capable of emitting more x-rays than the usual case without using pre-ionization.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement

NASA Astrophysics Data System (ADS)

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A.; Jackson, George

2018-04-01

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Demixing, surface nematization, and competing adsorption in binary mixtures of hard rods and hard spheres under confinement.

PubMed

Wu, Liang; Malijevský, Alexandr; Avendaño, Carlos; Müller, Erich A; Jackson, George

2018-04-28

A molecular simulation study of binary mixtures of hard spherocylinders (HSCs) and hard spheres (HSs) confined between two structureless hard walls is presented. The principal aim of the work is to understand the effect of the presence of hard spheres on the entropically driven surface nematization of hard rod-like particles at surfaces. The mixtures are studied using a constant normal-pressure Monte Carlo algorithm. The surface adsorption at different compositions is examined in detail. At moderate hard-sphere concentrations, preferential adsorption of the spheres at the wall is found. However, at moderate to high pressure (density), we observe a crossover in the adsorption behavior with nematic layers of the rods forming at the walls leading to local demixing of the system. The presence of the spherical particles is seen to destabilize the surface nematization of the rods, and the degree of demixing increases on increasing the hard-sphere concentration.

Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

NASA Astrophysics Data System (ADS)

Weber, T. E.; Intrator, T. P.; Smith, R. J.

2015-04-01

Injection of plasma via an annular array of coaxial plasma guns during the pre-ionization phase of field-reversed configuration (FRC) formation is shown to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. This approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ˜350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densities and higher temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.

Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

DOE PAGES

Weber, T. E.; Intrator, T. P.; Smith, R. J.

2015-04-29

We show through injection of plasma via an annular array of coaxial plasma guns, during the pre-ionization phase of field-reversed configuration (FRC) formation how to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. Our approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ~350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densitiesmore » and higher temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.« less

Plasma-gun-assisted field-reversed configuration formation in a conical θ-pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, T. E., E-mail: tweber@lanl.gov; Intrator, T. P.; Smith, R. J.

2015-04-15

Injection of plasma via an annular array of coaxial plasma guns during the pre-ionization phase of field-reversed configuration (FRC) formation is shown to catalyze the bulk ionization of a neutral gas prefill in the presence of a strong axial magnetic field and change the character of outward flux flow during field-reversal from a convective process to a much slower resistive diffusion process. This approach has been found to significantly improve FRC formation in a conical θ-pinch, resulting in a ∼350% increase in trapped flux at typical operating conditions, an expansion of accessible formation parameter space to lower densities and highermore » temperatures, and a reduction or elimination of several deleterious effects associated with the pre-ionization phase.« less

A Compact Soft X-Ray Microscope using an Electrode-less Z-Pinch Source.

PubMed

Horne, S F; Silterra, J; Holber, W

2009-01-01

Soft X-rays (< 1Kev) are of medical interest both for imaging and microdosimetry applications. X-ray sources at this low energy present a technological challenge. Synchrotrons, while very powerful and flexible, are enormously expensive national research facilities. Conventional X-ray sources based on electron bombardment can be compact and inexpensive, but low x-ray production efficiencies at low electron energies restrict this approach to very low power applications. Laser-based sources tend to be expensive and unreliable. Energetiq Technology, Inc. (Woburn, MA, USA) markets a 92 eV, 10W(2pi sr) electrode-less Z-pinch source developed for advanced semiconductor lithography. A modified version of this commercial product has produced 400 mW at 430 eV (2pi sr), appropriate for water window soft X-ray microscopy. The US NIH has funded Energetiq to design and construct a demonstration microscope using this source, coupled to a condenser optic, as the illumination system. The design of the condenser optic matches the unique characteristics of the source to the illumination requirements of the microscope, which is otherwise a conventional design. A separate program is underway to develop a microbeam system, in conjunction with the RARAF facility at Columbia University, NY, USA. The objective is to develop a focused, sub-micron beam capable of delivering > 1 Gy/second to the nucleus of a living cell. While most facilities of this type are coupled to a large and expensive particle accelerator, the Z-pinch X-ray source enables a compact, stand-alone design suitable to a small laboratory. The major technical issues in this system involve development of suitable focusing X-ray optics. Current status of these programs will be reported.

A Compact Soft X-Ray Microscope using an Electrode-less Z-Pinch Source

PubMed Central

Silterra, J; Holber, W

2009-01-01

Soft X-rays (< 1Kev) are of medical interest both for imaging and microdosimetry applications. X-ray sources at this low energy present a technological challenge. Synchrotrons, while very powerful and flexible, are enormously expensive national research facilities. Conventional X-ray sources based on electron bombardment can be compact and inexpensive, but low x-ray production efficiencies at low electron energies restrict this approach to very low power applications. Laser-based sources tend to be expensive and unreliable. Energetiq Technology, Inc. (Woburn, MA, USA) markets a 92 eV, 10W(2pi sr) electrode-less Z-pinch source developed for advanced semiconductor lithography. A modified version of this commercial product has produced 400 mW at 430 eV (2pi sr), appropriate for water window soft X-ray microscopy. The US NIH has funded Energetiq to design and construct a demonstration microscope using this source, coupled to a condenser optic, as the illumination system. The design of the condenser optic matches the unique characteristics of the source to the illumination requirements of the microscope, which is otherwise a conventional design. A separate program is underway to develop a microbeam system, in conjunction with the RARAF facility at Columbia University, NY, USA. The objective is to develop a focused, sub-micron beam capable of delivering > 1 Gy/second to the nucleus of a living cell. While most facilities of this type are coupled to a large and expensive particle accelerator, the Z-pinch X-ray source enables a compact, stand-alone design suitable to a small laboratory. The major technical issues in this system involve development of suitable focusing X-ray optics. Current status of these programs will be reported. PMID:20198115

Janka hardness using nonstandard specimens

Treesearch

David W. Green; Marshall Begel; William Nelson

2006-01-01

Janka hardness determined on 1.5- by 3.5-in. specimens (2×4s) was found to be equivalent to that determined using the 2- by 2-in. specimen specified in ASTM D 143. Data are presented on the relationship between Janka hardness and the strength of clear wood. Analysis of historical data determined using standard specimens indicated no difference between side hardness...

Simulation study of a new inverse-pinch high Coulomb transfer switch

NASA Technical Reports Server (NTRS)

Choi, S. H.

1984-01-01

A simulation study of a simplified model of a high coulomb transfer switch is performed. The switch operates in an inverse pinch geometry formed by an all metal chamber, which greatly reduces hot spot formations on the electrode surfaces. Advantages of the switch over the conventional switches are longer useful life, higher current capability and lower inductance, which improves the characteristics required for a high repetition rate switch. The simulation determines the design parameters by analytical computations and comparison with the experimentally measured risetime, current handling capability, electrode damage, and hold-off voltages. The parameters of initial switch design can be determined for the anticipated switch performance. Results are in agreement with the experiment results. Although the model is simplified, the switch characteristics such as risetime, current handling capability, electrode damages, and hold-off voltages are accurately determined.

Determining the Effect of Material Hardness During the Hard Turning of AISI4340 Steel

NASA Astrophysics Data System (ADS)

Kambagowni, Venkatasubbaiah; Chitla, Raju; Challa, Suresh

2018-05-01

In the present manufacturing industries hardened steels are most widely used in the applications like tool design and mould design. It enhances the application range of hard turning of hardened steels in manufacturing industries. This study discusses the impact of workpiece hardness, feed and depth of cut on Arithmetic mean roughness (Ra), root mean square roughness (Rq), mean depth of roughness (Rz) and total roughness (Rt) during the hard turning. Experiments have been planned according to the Box-Behnken design and conducted on hardened AISI4340 steel at 45, 50 and 55 HRC with wiper ceramic cutting inserts. Cutting speed is kept constant during this study. The analysis of variance was used to determine the effects of the machining parameters. 3-D response surface plots drawn based on RSM were utilized to set up the input-output relationships. The results indicated that the feed rate has the most significant parameter for Ra, Rq and Rz and hardness has the most critical parameter for the Rt. Further, hardness shows its influence over all the surface roughness characteristics.

Lower hybrid accessibility in a large, hot reversed field pinch

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dziubek, R.A.; Harvey, R.W.; Hokin, S.A.

1995-11-01

Accessibility and damping of the slow wave in a reversed field pinch (RFP) plasma is investigated theoretically, using projected Reversed Field Experiment (RFX) plasma parameters. By numerically solving the hot plasma dispersion relation, regions of propagation are found and the possibility of mode conversion is analyzed. If the parallel index of refraction of the wave is chosen judiciously at the edge of the plasma, the slow wave is accessible to a target region located just inside the reversal surface without mode conversion. Landau damping is also optimized in this region. A representative fast electron population is then added in ordermore » to determine its effect on accessibility and damping. The presence of these electrons, whose parameters were estimated by extrapolation of Madison Symmetric Torus (MST) data, does not affect the accessibility of the wave. However, the initial phase velocity of the wave needs to be increased somewhat in order to maintain optimal damping in the target zone.« less

EQ-10 electrodeless Z-pinch EUV source for metrology applications

NASA Astrophysics Data System (ADS)

Gustafson, Deborah; Horne, Stephen F.; Partlow, Matthew J.; Besen, Matthew M.; Smith, Donald K.; Blackborow, Paul A.

2011-11-01

With EUV Lithography systems shipping, the requirements for highly reliable EUV sources for mask inspection and resist outgassing are becoming better defined, and more urgent. The sources needed for metrology applications are very different than that needed for lithography; brightness (not power) is the key requirement. Suppliers for HVM EUV sources have all resources working on high power and have not entered the smaller market for metrology. Energetiq Technology has been shipping the EQ-10 Electrodeless Z-pinchTM light source since 19951. The source is currently being used for metrology, mask inspection, and resist development2-4. These applications require especially stable performance in both output power and plasma size and position. Over the last 6 years Energetiq has made many source modifications which have included better thermal management to increase the brightness and power of the source. We now have introduced a new source that will meet requirements of some of the mask metrology first generation tools; this source will be reviewed.

Small-amplitude magnetic Rayleigh-Taylor instability growth in cylindrical liners and Z-pinches imploded in an axial magnetic field

NASA Astrophysics Data System (ADS)

Velikovich, A. L.; Giuliani, J. L.; Clark, R. W.; Mikitchuk, D.; Kroupp, E.; Maron, Y.; Fisher, A.; Schmit, P. F.

2014-10-01

Recent progress in developing the MagLIF approach to pulsed-power driven inertial confinement fusion has stimulated the interest in observation and mitigation of the magnetic Rayleigh-Taylor instability (MRTI) of liners and Z-pinches imploded in an axial magnetic field. Theoretical analysis of these issues is particularly important because direct numerical simulation of the MRTI development is challenging due to intrinsically 3D helical structure of the fastest-growing modes. We review the analytical small-amplitude theory of the MRTI perturbation development and the weakly nonlinear theory of MRTI mode interaction, emphasizing basic physics, opportunity for 3D code verification against exact analytical solutions, and stabilization criteria. The theory is compared to the experimental results obtained at Weizmann Institute with gas-puff Z pinches and on the Z facility at Sandia with solid liners imploded in an axial magnetic field. Work supported by the US DOE/NNSA, and by the US-Israel Binational Science Foundation. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

Impurity profiles and radial transport in the EXTRAP-T2 reversed field pinch

NASA Astrophysics Data System (ADS)

Sallander, J.

1999-05-01

Radially resolved spectroscopy has been used to measure the radial distribution of impurity ions (O III-O V and C III-CVI) in the EXTRAP-T2 reversed field pinch (RFP). The radial profile of the emission is reconstructed from line emission measured along five lines of sight. The ion density profile is the fitted quantity in the reconstruction of the brightness profile and is thus obtained directly in this process. These measurements are then used to adjust the parameters in transport calculations in order to obtain consistency with the observed ion density profiles. Comparison between model and measurements show that a radial dependence in the diffusion is needed to explain the measured ion densities.

Determination of plasma pinch time and effective current radius of double planar wire array implosions from current measurements on a 1-MA linear transformer driver

NASA Astrophysics Data System (ADS)

Steiner, Adam M.; Yager-Elorriaga, David A.; Patel, Sonal G.; Jordan, Nicholas M.; Gilgenbach, Ronald M.; Safronova, Alla S.; Kantsyrev, Victor L.; Shlyaptseva, Veronica V.; Shrestha, Ishor; Schmidt-Petersen, Maximillian T.

2016-10-01

Implosions of planar wire arrays were performed on the Michigan Accelerator for Inductive Z-pinch Experiments, a linear transformer driver (LTD) at the University of Michigan. These experiments were characterized by lower than expected peak currents and significantly longer risetimes compared to studies performed on higher impedance machines. A circuit analysis showed that the load inductance has a significant impact on the current output due to the comparatively low impedance of the driver; the long risetimes were also attributed to high variability in LTD switch closing times. A circuit model accounting for these effects was employed to measure changes in load inductance as a function of time to determine plasma pinch timing and calculate a minimum effective current-carrying radius. These calculations showed good agreement with available shadowgraphy and x-ray diode measurements.

Simulations of Ar gas-puff Z-pinch radiation sources with double shells and central jets on the Z generator

DOE PAGES

Tangri, V.; Harvey-Thompson, Adam James; Giuliani, J. L.; ...

2016-10-19

Radiation-magnetohydrodynamic simulations using the non-LTE Mach2-TCRE code in (r,z) geometry are performed for two pairs of recent Ar gas-puff Z-pinch experiments on the refurbished Z generator with an 8 cm diameter nozzle. One pair of shots had an outer-to-inner shell mass ratio of 1:1.6 and a second pair had a ratio of 1:1.