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  • 1
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    Existence of a return direction for plasma escaping from a pinched column in a plasma focus discharge (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-05-16
    Description: 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 inside the pinched column, which has been published recently on the basis of observations from interferometry, neutron, and magnetic probe diagnostics on this device.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Filamentary structure of plasma produced by compression of puffing deuterium by deuterium or neon plasma sheath on plasma-focus discharge (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-12-12
    Description: The present experiments were performed on the PF-1000 plasma focus device at a current of 2 MA with the deuterium injected from the gas-puff placed in the axis of the anode face. The XUV frames showed, in contrast with the interferograms, the fine structure: filaments and spots up to 1 mm diameter. In the deuterium filling, the short filaments are registered mainly in the region of the internal plasmoidal structures and their number correlates with the intensity of neutron production. The longer filamentary structure was recorded close to the anode after the constriction decay. The long curve-like filaments with spots were registered in the big bubble formed after the pinch phase in the head of the umbrella shape of the plasma sheath. Filaments can indicate the filamentary structure of the current in the pinch. Together with the filaments, small compact balls a few mm in diameter were registered by both interferometry and XUV frame pictures. They emerge out of the dense column and their life-time can be greater than hundreds of ns.
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    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 3
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    Deuterium z-pinch as a powerful source of multi-MeV ions and neutrons for advanced applications (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-03-05
    Description: A novel configuration of a deuterium z-pinch has been used to generate a nanosecond pulse of fast ions and neutrons. At a 3 MA current, the peak neutron yield of (3.6 ± 0.5) × 10 12 was emitted within 20 ns implying the production rate of 10 20 neutrons/s. High neutron yields resulted from the magnetization of MeV deuterons inside plasmas. Whereas deuterons were trapped in the radial direction, a lot of fast ions escaped the z-pinch along the z-axis. A large number of 〉25 MeV ions were emitted into a 250 mrad cone. The cut-off energy of broad energy spectra of hydrogen ions approached 40 MeV. The total number of 〉1 MeV and 〉25 MeV deuterons were 10 16 and 10 13 , respectively. Utilizing these ions offers a real possibility of various applications, including the increase of neutron yields or the production of short-lived isotopes in samples placed in ion paths. On the basis of our experiments with various samples, we concluded that a single shot would have been sufficient to obtain GBq positron activity of 13 N isotopes via the 12 C(d,n) 13 N reaction. Furthermore, the first z-pinch generated neutron radiograph produced by ≈20 ns pulses is presented in this paper.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 4
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    Investigation of compression of puffing neon by deuterium current and plasma sheath in plasma focus discharge (2015)
    American Institute of Physics (AIP)
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    Publication Date: 2015-06-12
    Description: This paper presents the results of the research of the influence of compressed neon, injected by the gas-puff nozzle in front of the anode axis by the deuterium current and plasma sheath on the evolution of the pinch, and neutron production at the current of 2 MA. The intense soft X-ray emission shows the presence of neon in the central region of the pinch. During the implosion and stopping of the plasma sheath, the deuterium plasma penetrates into the internal neon layer. The total neutron yield of 10 10 –10 11 has a similar level as in the pure deuterium shots. The neutron and hard X-ray pulses from fusion D-D reaction are as well emitted both in the phase of the stopping implosion and during the evolution of instabilities at the transformation of plasmoidal structures and constrictions composed in this configuration from both gases. The fast deuterons can be accelerated at the decay of magnetic field of the current filaments in these structures.
    Print ISSN: 1070-664X
    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 5
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    The influence of the nitrogen admixture on the evolution of a deuterium pinch column (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-08-12
    Description: The application of a mixture of nitrogen and deuterium for the gas-puffing along the anode axis in deuterium plasma-focus discharges, as carried out at megaampere-level currents, enabled observations of the filamentary structure, and the decrease in the transformation velocity of the plasma column to be performed. It made possible to investigate the instability evolution during the production of hard X-rays and fast neutrons in more detail. The constriction of a plasma column transforms itself during the final phase of the compression into one or more small dense plasmoid-like structures which are separated by narrow necks. During the next phase, these structures start to decay by an expansion, in which a part of the plasma volume maintains its compactness. This evolution is explained by an increase and later decrease in the internal poloidal current component by reconnections of the associated magnetic lines, which are responsible for the acceleration of electron and ion beams.
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    Electronic ISSN: 1089-7674
    Topics: Physics
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  • 6
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    Influence of the Al wire placed in the anode axis on the transformation of the deuterium plasma column in the plasma focus discharge (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-06-14
    Description: In this paper, we describe the influence of an Al wire of 270  μ m in diameter placed along the anode axis on the transformation of the deuterium pinch column in a megaampere (MA) plasma focus device. The evolution of the pinched column and of the wire corona was investigated by means of the multiframe interferometry, neutron and X-ray diagnostics. The wire corona did not influence considerably on the evolution of dense plasma structures and neutron production, but it increased the plasma density and consequently, the currents around its surface. The distribution of the closed internal currents (ranging hundreds of kA) and associated magnetic fields amounting to 5 T were also estimated in the dense plasma column and in plasmoidal structures at the near-equilibrium state. The description is based on the balance of the plasma pressure and the pressure of the internal poloidal and toroidal current components compressed by the external pinched column. The dominant number of fusion deuterium-deuterium (D-D) neutrons is produced during the evolution of instabilities, when the uninterrupted wire corona (containing deuterium) connects the dense structures of the pinch, and it did not allow the formation of a constriction of the sub-millimeter diameter.
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    Electronic ISSN: 1089-7674
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  • 7
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    Measurement of the target current by inductive probe during laser interaction on terawatt laser system PALS (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-10-18
    Description: Measurements of the return-current flowing through a solid target irradiated with the sub-nanosecond kJ-class Prague Asterix Laser System is reported. A new inductive target probe was developed which allows us measuring the target current derivative in a kA/ns range. The dependences of the target current on the laser pulse energy for cooper, graphite, and polyethylene targets are reported. The experiment shows that the target current is proportional to the deposited laser energy and is strongly affected by the shot-to-shot fluctuations. The corresponding maximum target charge exceeded a value of 10 μC. A return-current dependence of the electromagnetic pulse produced by the laser-target interaction is presented.
    Print ISSN: 0034-6748
    Electronic ISSN: 1089-7623
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
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  • 8
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    Neutron production from puffing deuterium in plasma focus device (2014)
    American Institute of Physics (AIP)
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    Publication Date: 2014-08-08
    Description: The current research has continued on the PF-1000 plasma focus device at the current of 2 MA by comparison of the shots with and without injected deuterium. The increase of the total neutron yield at the level of 10 10 –10 11 per shot was achieved after the compression of about 10  μ g/cm of the deuterium from the gas-valve by about 46  μ g/cm of the neon or deuterium plasma sheath. It increases five times at the decrease of the puffing deuterium mass to one-half. In shots with neon in the chamber and with puffing deuterium, a considerable decrease was confirmed of the soft X-ray emission in comparison with shots without deuterium injection. This decrease can be explained by the absence of the neon in the region of the compressed and hot plasma. The deuterium plasma from the gas-puff should then be confined in the internal structures both in the phase of implosion as well as during their formation and transformation. In shots with puffing deuterium, the evolution of instabilities in the plasma column was suppressed. The deuterium plasma has a higher conductance and better ability to form expressive and dense plasmoids and to transport the internal current in comparison with neon plasma. Neutrons were produced both at the initial phase of stagnation, as well as at a later time at the evolution of the constrictions and dense plasmoids.
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    Topics: Physics
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  • 9
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    Intravascular danger signals guide neutrophils to sites of sterile inflammation (2010)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2010-10-16
    Description: Neutrophils are recruited from the blood to sites of sterile inflammation, where they contribute to wound healing but may also cause tissue damage. By using spinning disk confocal intravital microscopy, we examined the kinetics and molecular mechanisms of neutrophil recruitment to sites of focal hepatic necrosis in vivo. Adenosine triphosphate released from necrotic cells activated the Nlrp3 inflammasome to generate an inflammatory microenvironment that alerted circulating neutrophils to adhere within liver sinusoids. Subsequently, generation of an intravascular chemokine gradient directed neutrophil migration through healthy tissue toward foci of damage. Lastly, formyl-peptide signals released from necrotic cells guided neutrophils through nonperfused sinusoids into the injury. Thus, dynamic in vivo imaging revealed a multistep hierarchy of directional cues that guide neutrophil localization to sites of sterile inflammation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McDonald, Braedon -- Pittman, Keir -- Menezes, Gustavo B -- Hirota, Simon A -- Slaba, Ingrid -- Waterhouse, Christopher C M -- Beck, Paul L -- Muruve, Daniel A -- Kubes, Paul -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2010 Oct 15;330(6002):362-6. doi: 10.1126/science.1195491.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Immunology Research Group, University of Calgary, Alberta T2N 4N1, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20947763" target="_blank"〉PubMed〈/a〉
    Keywords: Adenosine Triphosphate/metabolism ; Animals ; Carrier Proteins/metabolism ; Cell Adhesion ; Chemokine CXCL2/metabolism ; Chemokines/metabolism ; Chemotaxis, Leukocyte ; Cues ; Endothelium, Vascular/physiology ; Inflammation/*immunology/metabolism/*pathology ; Kinetics ; Liver/blood supply/*immunology/metabolism/*pathology ; Liver Diseases/*immunology/metabolism/*pathology ; Macrophage-1 Antigen/physiology ; Mice ; Microscopy/methods ; Microscopy, Confocal ; Microvessels/physiology ; Necrosis ; *Neutrophil Infiltration ; Neutrophils/physiology ; Peptides/metabolism ; Receptors, Formyl Peptide/metabolism ; Receptors, Interleukin-8B/metabolism ; Receptors, Purinergic P2/metabolism ; Receptors, Purinergic P2X7 ; Signal Transduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Functional innervation of hepatic iNKT cells is immunosuppressive following stroke (2011)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2011-09-17
    Description: Systemic immunosuppression has been associated with stroke for many years, but the underlying mechanisms are poorly understood. In this study, we demonstrated that stroke induced profound behavioral changes in hepatic invariant NKT (iNKT) cells in mice. Unexpectedly, these effects were mediated by a noradrenergic neurotransmitter rather than a CD1d ligand or other well-characterized danger signals. Blockade of this innervation was protective in wild-type mice after stroke but had no effect in mice deficient in iNKT cells. Selective immunomodulation of iNKT cells with a specific activator (alpha-galactosylceramide) promoted proinflammatory cytokine production and prevented infections after stroke. Our results therefore identify a molecular mechanism that leads to immunosuppression after stroke and suggest an attractive potential therapeutic alternative to antibiotics, namely, immunomodulation of iNKT cells to prevent stroke-associated infections.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wong, Connie H Y -- Jenne, Craig N -- Lee, Woo-Yong -- Leger, Caroline -- Kubes, Paul -- Canadian Institutes of Health Research/Canada -- New York, N.Y. -- Science. 2011 Oct 7;334(6052):101-5. doi: 10.1126/science.1210301. Epub 2011 Sep 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Calvin, Phoebe, and Joan Snyder Institute for Infection, Immunity, and Inflammation, University of Calgary, Calgary, Alberta, Canada.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21921158" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenergic Agents/pharmacology ; Animals ; Anti-Bacterial Agents/administration & dosage ; Bacterial Infections/etiology/immunology/prevention & control ; Brain Ischemia/complications/*immunology ; Cell Movement ; Cytokines/metabolism ; Galactosylceramides/immunology/pharmacology ; *Immune Tolerance ; Immunomodulation ; Infarction, Middle Cerebral Artery/complications/*immunology ; Liver/blood supply/*immunology/*innervation ; Lymphocyte Activation ; Mice ; Mice, Inbred BALB C ; Microvessels/cytology ; Natural Killer T-Cells/*immunology/physiology ; Norepinephrine/pharmacology ; Propranolol/pharmacology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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