Commissioning of a Rotated Wire Array Configuration for Improved Diagnostic Access

Swadling, G. F.; Hall, G. N.; Lebedev, S. V.; Burdiak, G.; Suzuki-Vidal, F.; Grouchy, P. de; Suttle, L.; Bennett, M.; Sheng, Liang

doi:10.1109/tps.2015.2388863

Cited by 4 publications

(5 citation statements)

References 24 publications

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“…The arrays were mounted in the generator using a specially designed electrode hardware configuration which places the wire array on its side so that its axis lies perpendicular to the axis of the coaxial pulsed-power drive electrodes. 32 This arrangement does introduce some small current drive asymmetries; this disadvantage is however easily overcome by the advantage of the diagnostic access that this layout allows. Mounting the array in this manner provides an unobscured end-on view through the wire array interior, easing interferometry access, and allowing us to use a much improved Thomson scattering geometry.…”

Section: Methodsmentioning

confidence: 99%

“…18, except that the rotated array configuration used in these experiments removed the need for the cathode mounted mirror, allowing laser probing to be carried out at significantly later times. 32 These probe beams had pulse durations of $500 ps, diameters of $2 cm, and a total energy per pulse of $10 mJ. Interferograms were captured using Canon DSLR cameras.…”

Section: Methodsmentioning

confidence: 99%

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Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

et al. 2015

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Articles you may be interested inExperimental characterization of a transition from collisionless to collisional interaction between head-onmerging supersonic plasma jetsa) Phys. Plasmas 22, 055707 (2015); 10.1063/1.4920955 Diagnosing collisions of magnetized, high energy density plasma flows using a combination of collective Thomson scattering, Faraday rotation, and interferometry (invited)a) Rev. Sci. Instrum. 85, 11E502 (2014); 10.1063/1.4890564 Numerical study of transition to supersonic flows in the edge plasma Phys. Plasmas 21, 072510 (2014); 10.1063/1.4890026 The formation of reverse shocks in magnetized high energy density supersonic plasma flowsa) Phys. Plasmas 21, 056305 (2014); 10.1063/1.4874334Examination of the shock wave regular reflexion phenomenon in a rarefied supersonic plasma flow An optical Thomson scattering diagnostic has been used to investigate collisions between supersonic, magnetized plasma flows, in particular the transition from collisionless to collisional interaction dynamics. These flows were produced using tungsten wire array z-pinches, driven by the 1.4 MA 240 ns Magpie generator at Imperial College London. Measurements of the collectivemode Thomson scattering ion-feature clearly indicate that the ablation flows are interpenetrating at 100 ns (after current start), and this interpenetration continues until at least 140 ns. The Thomson spectrum at 150 ns shows a clear change in the dynamics of the stream interactions, transitioning towards a collisional, shock-like interaction of the streams near the axis. The Thomson scattering data also provide indirect evidence of the presence of a significant toroidal magnetic field embedded in the "precursor" plasma near the axis of the array over the period 100-140 ns; these observations are in agreement with previous measurements [Swadling et al., Phys. Rev. Lett. 113, 035003 (2014)]. The Thomson scattering measurements at 150 ns suggest that this magnetic field must collapse at around the time the dense precursor column begins to form. V C 2015 AIP Publishing LLC.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

et al. 2015

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“…In order to collect scattered light along the vectors indicated in Figure 3(c), the wire array load was rotated 90 with respect to the axis of the pulsed power drive electrodes; 19 a simplified diagram of this arrangement is provided in Figure 3(a). An end-on cartoon of the flow geometry is provided in (b), the diagnostic layout is shown in (c), and the scattering geometry is indicated in (d).…”

Section: Thomson Scattering Investigationsmentioning

confidence: 99%

“…The experimental setup used to make these measurements is similar to that shown in Figure 3(a). A tungsten wire array is mounted perpendicular to the drive electrodes 19 and diagnosed simultaneously using an "endon" interferometric imaging diagnostic and a "side-on" Faraday rotation diagnostic; details of the design of both of these diagnostics may be found in Ref. 7.…”

Section: Magnetic Field Measurementsmentioning

confidence: 99%

Experimental investigations of ablation stream interaction dynamics in tungsten wire arrays: Interpenetration, magnetic field advection, and ion deflection

et al. 2016

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Experiments have been carried out to investigate the collisional dynamics of ablation streams produced by cylindrical wire array z-pinches. A combination of laser interferometric imaging, Thomson scattering, and Faraday rotation imaging has been used to make a range of measurements of the temporal evolution of various plasma and flow parameters. This paper presents a summary of previously published data, drawing together a range of different measurements in order to give an overview of the key results. The paper focuses mainly on the results of experiments with tungsten wire arrays. Early interferometric imaging measurements are reviewed, then more recent Thomson scattering measurements are discussed; these measurements provided the first direct evidence of ablation stream interpenetration in a wire array experiment. Combining the data from these experiments gives a view of the temporal evolution of the tungsten stream collisional dynamics. In the final part of the paper, we present new experimental measurements made using an imaging Faraday rotation diagnostic. These experiments investigated the structure of magnetic fields near the array axis directly; the presence of a magnetic field has previously been inferred based on Thomson scattering measurements of ion deflection near the array axis. Although the Thomson and Faraday measurements are not in full quantitative agreement, the Faraday data do qualitatively supports the conjecture that the observed deflections are induced by a static toroidal magnetic field, which has been advected to the array axis by the ablation streams. It is likely that detailed modeling will be needed in order to fully understand the dynamics observed in the experiment. Published by AIP Publishing.

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“…V C 2015 AIP Publishing LLC 22, 072509-1 unintentionally due to asymmetries on the current distribution within the array produced by modifications on the generator parameters, such as changes on the load return current path 18,19 or asynchronous actuation of the different modules of the pulsed power device. 20 In this paper, the effects of non-axially symmetric temporal variations of the magnetic field topology on the ablation phase and on the ablation streams in wire arrays dynamics are investigated.…”

Section: Introductionmentioning

confidence: 99%

Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology

et al. 2015

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The dynamics of ablation streams and precursor plasma in cylindrical wire array Z-pinches under temporal variations of the global magnetic field topology is investigated through experiments and numerical simulations. The wire arrays in these experiments are modified by replacing a pair of consecutive wires with wires of a larger diameter. This modification leads to two separate effects, both of which impact the dynamics of the precursor plasma; firstly, current is unevenly distributed between the wires and secondly, the thicker wires take longer to fully ablate. The uneven distribution of current is evidenced in the experiments by the drift of the precursor off axis due to a variation in the global magnetic field topology which modifies the direction of the ablation streams tracking the precursor position. The variation of the global magnetic field due to the presence of thick wires is studied with three-dimensional magnetohydrodynamic (MHD) simulations, showing that the global field changes from the expected toroidal field to a temporally variable topology after breakages appear in the thin wires. This leads to an observed acceleration of the precursor column towards the region closer to the thick wires and later, when thick wires also present breakages, it continues moving away from the original array position as a complicated and disperse object subject to MHD instabilities

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Commissioning of a Rotated Wire Array Configuration for Improved Diagnostic Access

Cited by 4 publications

References 24 publications

Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

Interpenetration and deflection phenomena in collisions between supersonic, magnetized, tungsten plasma flows diagnosed using high resolution optical Thomson scattering

Experimental investigations of ablation stream interaction dynamics in tungsten wire arrays: Interpenetration, magnetic field advection, and ion deflection

Ablation dynamics in wire array Z-pinches under modifications on global magnetic field topology

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