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The inductance of imploding cylindrical wire array z-pinches has been determined from measurements of load voltage and current. A thorough analysis method is presented that explains how the load voltage of interest is found from raw signals obtained using a resistive voltage divider. This method is applied to voltage data obtained during z-pinch experiments carried out on the MAGPIE facility (1.4 MA, 240 ns rise-time) in order to calculate the load inductance and thereafter the radial trajectory of the effective current sheath during the snowplough implosion. Voltage and current are monitored very close to the load, allowing these calculations to be carried out without the need for circuit modelling. Measurements give a convergence ratio for the current of between 3.1 and 5.7 at stagnation of the pinch.

A series of experiments has been conducted in order to investigate the azimuthal structures formed by the interactions of cylindrically converging plasma flows during the ablation phase of aluminium wire array Z pinch implosions. These experiments were carried out using the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. The main diagnostic used in this study was a two-colour, end-on, Mach-Zehnder imaging interferometer, sensitive to the axially integrated electron density of the plasma. The data collected in these experiments reveal the strongly collisional dynamics of the aluminium ablation streams. The structure of the flows is dominated by a dense network of oblique shock fronts, formed by supersonic collisions between adjacent ablation streams. An estimate for the range of the flow Mach number (M = 6.2-9.2) has been made based on an analysis of the observed shock geometry. Combining this measurement with previously published Thomson Scattering measurements of the plasma flow velocity by H...

Experiments to study the ablation dynamics of coiled wire arrays were performed on the MAGPIE generator (1 MA, 240 ns) at Imperial College, and on the COBRA generator at Cornell University's Laboratory of Plasma Studies (1 MA, 100 ns). The MAGPIE generator was used to drive coiled wires in an inverse array configuration to study the distribution of ablated plasma. Using interferometry to study the plasma distribution during the ablation phase, absolute quantitative measurements of electron line density demonstrated very high density contrasts between coiled ablation streams and inter-stream regions many millimetres from the wire. The measured density contrasts for a coiled array were many times greater than that observed for a conventional array with straight wires, indicating that a much greater axial modulation of the ablated plasma may be responsible for the unique implosion dynamics of coiled arrays. Experiments on the COBRA generator were used to study the complex redirection of plasma around a coiled wire that gives rise to the ablation structure exhibited by coiled arrays. Observations of this complex 3D plasma structure were used to validate the current model of coiled array ablation dynamics [Hall et al., Phys. Rev. Lett. 100, 065003 (2008)], demonstrating irrefutably that plasma flow from the wires behaves as predicted. Coiled wires were observed to ablate and implode in the same manner on both machines, indicating that current rise time should not be an issue for the scaling of coiled arrays to larger machines with fast current rise times.

An Optical Thomson Scattering (OTS) diagnostic is currently being developed for the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory. This diagnostic is designed to make measurements of the hohlraum plasma parameters, such as the electron temperature and the density, during inertial confinement fusion (ICF) experiments. NIF ICF experiments present a very challenging environment for optical measurements; by their very nature, hohlraums produce intense soft x-ray emission, which can cause “blanking” (radiation induced opacity) of the radiation facing optical components. The soft x-ray fluence at the surface of the OTS blast shield, 60 cm from the hohlraum, is estimated to be ∼8 J cm−2. This is significantly above the expected threshold for the onset of “blanking” effects. A novel xenon plasma x-ray shield is proposed to protect the blast shield from x-rays and mitigate “blanking.” Estimates suggest that an areal density of 1019 cm−2 Xe atoms will be sufficient to absorb 99.5% of the soft x-ray flux. Two potential designs for this shield are presented.

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 rotationimaging 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 imagingmeasurements 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 imagingFaraday rotationdiagnostic. 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 Faradaymeasurements 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.

The National Ignition Facility (NIF) is a 192 laser beam facility designed to support the Stockpile Stewardship, High Energy Density and Inertial Confinement Fusion programs. We report on the preliminary design of an Optical Thomson Scattering (OTS) diagnostic that has the potential to transform the community's understanding of NIF hohlraum physics by providing first principle, local, time-resolved measurements of under-dense plasma conditions. The system design allows operation with different probe laser wavelengths by manual selection of the appropriate beamsplitter and gratings before the shot. A deep-UV probe beam (λ0 between 185-215 nm) will optimally collect Thomson scattered light from plasma densities of 5 x 1020 electrons/cm3 while a 3ω probe will optimally collect Thomson scattered light from plasma densities of 1 x 1019 electrons/cm3. We report the phase I design of a two phase design strategy. Phase I includes the OTS recording system to measure background levels at NIF and phase II will include the integration of a probe laser.

Summary form only given. Experimental data from gas-filled cylindrical liner z-pinch experiments is presented. The MAGPIE current (1.4 MA, 240 ns) is applied to a thin walled (80um) aluminium tube with a static gas-fill inside. The system is diagnosed axially using laser interferometry, optical streak photography and optical spectroscopy. We observe a series of cylindrically converging shock waves driven into the gas-fill from the inside liner surface. No bulk motion of the liner occurs.

Summary form only given. The use of plastic formers coated in a thin film of Aluminium for the purposes of tailoring pulsed power driven radiative shock waves is discussed.

Summary form only given. A supersonic (Mach∼3–5), radiatively cooled plasma jet is produced by the ablation of plasma from a radial foil1, a metallic disk subjected to a ∼1.4 MA, 250 ns current pulse from the MAGPIE generator. The ablated plasma converges on axis, producing a steady and collimated jet with a typical axial velocity of ∼100 km/s.

Summary form only given. Coiled arrays, a cylindrical array in which each wire is formed into a single helix, suppress the modulation of ablation at the fundamental wavelength. Instead, ablation flow is modulated at the wavelength of the coil, and arrays with large coil wavelength produce an organized mode of implosion in which the global instability can be controlled. The ablation and implosion dynamics of coiled arrays in this regime were studied using a combination of resistive voltage probes and Faraday rotation. These experiments were carried out on the MAGPIE generator at Imperial College. This research was sponsored by the DOE under Cooperative Agreements DEF03-02NA00057 and the Imperial College Junior Research Fellowship scheme.

Summary form only given. End-On interferometric measurements of the areal electron density distribution of wire array z-pinches has revealed striking differences in the behaviour of ablation plasmas. A change in wire material from aluminium to tungsten results in a change from a highly collisional structure dominated by shock formations to a much less collisional regime.

Summary form only given. We will present experiments on the MAGPIE facility (1.5MA, 250ns) in which an inverse wire array1 (with the wires acting as a return current cage placed around a central current conductor) operated as a fast current switch. This allowed to significantly reduce the rise-time of the current pulse (

Preliminary results of the interaction of a supersonic, radiatively cooled plasma jet with an ambient gas are presented. The experimental setup consists of a radial foil, a mum-thick aluminium disc held between two concentric electrodes and subjected to a 1.4 MA, 250-ns current pulse from the MAGPIE generator. The plasma flow, with typical velocities of ~70–90 km/s, is produced by the J × B force acting on the plasma ablated from the foil. A jet is formed from the convergence of this ablated plasma on the axis of the system. A new setup allows the jet to interact with an argon ambient (particle density N ~1016-17 cm−3) from a supersonic gas nozzle (Mach ~9). First results are characterised by the presence of several (previously unseen) shock structures, which are formed from the interaction of the jet with the argon ambient.

A Thomson scattering diagnostic has been used to measure the parameters of cylindrical wire array Z pinch plasmas during the ablation phase. The scattering operates in the collective regime (α>1) allowing spatially localized measurements of the ion or electron plasma temperatures and of the plasma bulk velocity. The ablation flow is found to accelerate towards the axis reaching peak velocities of 1.2-1.3×10(7) cm/s in aluminium and ∼1×10(7) cm/s in tungsten arrays. Precursor ion temperature measurements made shortly after formation are found to correspond to the kinetic energy of the converging ablation flow.

An experimental investigation into the interaction of a supersonic, radiatively cooled plasma jet with argon gas is presented. The jet is formed by ablation of an aluminum foil driven by a 1.4 MA, 250 ns current pulse in a radial foil Z-pinch configuration. The outflow consists of a supersonic (Mach number ∼3–5), dense (ion density ni ∼ 1018 cm−3), highly collimated (half-opening angle ∼2°−5°) jet surrounded by a lower density halo plasma moving with the same axial velocity as the jet. The addition of argon above the foil leads to the formation of a shock driven by the ablation of halo plasma, together with a bow-shock driven by the dense jet. Experimental data with and without the presence of argon are compared with three-dimensional, magneto-hydrodynamic simulations using the GORGON code.

Summary form only given. A Thomson scattering diagnostic has been developed to probe plasmas produced using the MAGPIE generator (1.4MA, 240ns). The diagnostic uses a frequency doubled Nd:YAG laser delivering ∼2–4J in 8ns FWHM to the target plasma. The density and temperature of the wire array targets probed produces scattered light in the collective regime (α>1). Any bulk motion of the probed plasma Doppler shifts the scattered spectrum allowing the velocity of the probed plasma to be measured. Measurements of the ablation velocity and the implosion velocity in cylindrical wire arrays at different positions in the arrays and for different wire materials are presented. In addition, the ion acoustic features in this scattering regime can be used to take measurements of electron and ion temperatures in e.g. precursor plasmas.

Summary form only given. New end-on measurements have taken of the areal electron density distribution of wire array z-pinches during the ablation phase. These measurements have been used to investigate the differences in dynamics between aluminium and tungsten arrays. The experiments were carried out on the 1.4 MA peak current, 240ns rise-time MAGPIE generator at Imperial College, London. The measurements were taken using a two colour Mach-Zender style imaging interferometer. Probing is provided by the 2nd and 3rd harmonics (532nm and 355nm) of a pulsed Nd:YAG laser with a pulse duration of ~500ps. In addition, a time resolved Quadrature Interferometer, powered by a CW diode pumped Nd:YAG laser has been used to calibrate these measurements. The fringe shift due to a specific line through array is tracked in time. By comparing the fringe shift at the moment an image is taken with the shift at corresponding point in the image, the fringe shift and thus the electron density can be calibrated unambiguously over the entire array cross-section. Results are presented and comparisons made to both the rocket model and simulations produced using the GORGON MHD code.

Detailed knowledge of the opacity of warm, dense plasmas is critically important for many astrophysics phenomena e.g. the power output of Cepheid Variables, as well as for other radiative processes including inertial confinement fusion. We present preliminary experiments designed to measure the opacity of warm, dense plasmas (n i ∼10e17 – 10e19, T ∼5–50eV) on the MAGPIE 1.4MA facility at Imperial College London. The precursor plasma of a cylindrical wire array z-pinch is explored as a source of these plasmas, due to it being long-lived and stable for 100s of ns 1,2; which may allow even high Z elements to approach LTE. Probing radiation for the experiments was supplied via a high Z X-pinch which is capable of producing a high intensity, point burst of X-radiation, with a wide continuum.

The formation of highly supersonic, radiatively cooled plasma jets with applications to laboratory astrophysics has been an active area of research on the MAGPIE generator. Two experimental arrangements, radial wire arrays1 and radial foils2, can produce plasma flows with similar dimensionless numbers to those encountered in protostellar jets. In radial wire arrays, a magnetically driven jet on the axis of a cavity evolves into a “clumpy” outflow due to the formation of current-driven instabilities, which could be relevant to the spatial and temporal variability of features observed in protostellar jets. In radial foils, a hydrodynamic jet interacts with an argon ambient injected above the foil using a supersonic gas nozzle. The results are characterized by the formation of several shock features, opening the possibility of studying jet-ambient interactions in the laboratory. Experimental results from different diagnostics including laser probing and self-emission of protons will be presented. Theses results will be compared with first 3-D MHD simulations using the Gorgon code.

Results of several recent experiments with wire array Z-pinches on the MAGPIE facility (1.5MA, 250ns) will be presented. We will report on the use of Thomson scattering diagnostic for measurements of plasma parameters in Al and W cylindrical wire arrays and for measurements of velocities of supersonic radiatively cooled plasma jets in conical and radial wire arrays. We will also present measurements of the plasma distribution inside wire arrays during the ablation phase, obtained with laser interferometer.

Highly supersonic radiatively cooled plasma jets are produced by introducing a 1-MA 250-ns current pulse from the MAGPIE generator into a radial foil. The setup allows for the introduction of a neutral gas above the foil, in order to study the jet-ambient interaction. The dynamics are characterized by the formation of several shock features, which are imaged using laser interferometry. This diagnostic also allows to measure the electron density of the plasma, and examples of such results are presented here.

We will present experiments on the MAGPIE facility (1.5MA, 250ns) in which an inverse wire array [1] (with the wires acting as a return current cage placed around a central current conductor) operated as a fast current switch [2]. This allowed to significantly reduce the rise-time of the current pulse (< 100ns) delivered to a separate, standard imploding wire array z-pinch load. Experimental studies of the operation of this arrangement as a current switch will be discussed. In particular it was found that this arrangement generates a short current pre-pulse (∼5kA

End on Interferometric imaging is a useful technique for diagnosing the electron density distribution in the interior of wire array z-pinches during their ablation phase. These measurements are limited as there is often no known density reference point in the image. By using a time resolved, CW line integrated interferometry system, we can measure the electron density for a single point on the image. This allows us to calculate the density distribution across the remainder of the image. Two new quadrature interferometry systems are discussed, the first free space and the second fiber based. Also discussed is a new fiber based multipoint Heterodyne Velocimetry (HET-V) system, for the time resolved measurement of large velocities and accelerations, and a new faraday rotation current probe system, to measure rapidly rising currents in new switched mode wire arrays.

Coiled arrays, a cylindrical array in which each wire is formed into a single helix, suppress the modulation of ablation at the fundamental wavelength. Instead, ablation flow is modulated at the wavelength of the coil. Large wavelength coils produce wire beaks with sufficient axial separation that perturbations in the implosion sheath do not merge, producing an organized mode of implosion in which the global instability can be controlled and the perturbations correlated between all the wires in the array. The inductance of the current paths that may be established by an organized implosion are considered. This suggests that, for a given inductive voltage drop across the load, coiled arrays are capable of achieving significantly higher current convergence to the axis than straight arrays. These experiments were carried out on the MAGPIE generator at Imperial College. This research was sponsored by Sandia National Laboratories Albuquerque, the SSAA program of NNSA under DOE Cooperative Agreement DE-FC03-02NA00057.

Results of several recent experiments with wire array Z-pinches on the MAGPIE facility (1.5MA, 250ns) will be presented. This will include experiments with generation of supersonic radiatively cooled plasma jets using conical and radial wire arrays. We will also present measurements of the plasma parameters in standard wire arrays and wire arrays made of coiled wires, obtained with recently implemented diagnostics such as resistive voltage probe, CW laser interferometer and others.

International audience; We present experimental results of the formation of magnetically driven plasma jets, showing for the first time a way of producing episodic jet/ouflows in the laboratory. The jets are produced using a 6.5 mum thick aluminum disk (a radial foil), which is subjected to the 1 MA, 250 ns current pulse from the MAGPIE generator [I. H. Mitchell et al., Rev. Sci. Instrum. 67, 1533 (1996)]. The early time motion of the foil is characterized by the bulk motion of the mass due to the magnetic pressure, together with the formation of a surface plasma following the direction of the J×B force. A low density plasma fills the region above the foil preceding the formation of subsequent magnetically driven jets on the axis of expanding magnetic bubbles. The outflows emerge in timescales of ~30-40 ns and their episodic nature is the result of current reconnection in the foil, aided by the formation of current-driven instabilities in the jet and the distribution of mass available from the foil. The additional inductance due to the new current path inside the cavities was measured using an inductive probe, allowing to estimate the energy balance associated with the episodes. The measured temperature of the compressed jet resulted in Te~300 eV and a magnetic Reynolds number of ReM~200-1000, allowing the experiments to be in the regime relevant for scaled representations of astrophysical outflows.

We present experimental results on the formation of supersonic, radiatively cooled jets driven by pressure due to the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which a jet on the axis of a magnetic cavity is collimated by a toroidal magnetic field as it expands into the ambient medium. The jets in the experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets. Additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration allows for the generation of episodic magnetic cavities, suggesting that periodic fluctuations near the source may be responsible for some of the variability observed in astrophysical jets. Preliminary measurements of kinetic, magnetic and Poynting energy of the jets in our experiments are presented and discussed, together with estimates of their temperature and trapped toroidal magnetic field., Comment: 7 pages, 6 figures, accepted for publication in Astrophysics & Space Science

Recent wire-array Z-pinch experiments performed on the MAGPIE generator at Imperial College are presented at currents up to 1.5 MA. Experiments have been conducted using a variety of array configurations, including radial wire arrays, cylindrical arrays, and coiled arrays. This research was sponsored by Sandia National Laboratories, Albuquerque; and the NNSA under DOE Cooperative Agreement DE-F03-02NA00057

Summary form only given. Experiments with the aim of studying the dynamics of a ~mum thick radial metallic foil subject to the current from the MAGPEE generator (peak current of 1 MA in 250 ns) have been performed at Imperial College. After the start of the current pulse the foil is ohmically heated and then is driven by the JtimesB force in the axial direction, which is reasonably described by 0-D equations of motion. Data on the parameters of ablation from the foil will be presented as well as evidence of azimuthal current filamentation. The pressure of the toroidal magnetic field detaches the foil from the electrode creating a gap and allowing the formation of a "magnetic tower" similar to what it is observed on radial wire arrays. Current reconnection across the gap leads to the formation of subsequent outflows which are characterized by emission of soft x-rays as sharp pulses. This experimental configuration can be also used to drive strong shock waves through neutral gases. Results of these experiments will also be presented.

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 expe...

The formation and dynamics of cylindrical wire array Z-pinch plasmas using uneven mass distribution is studied through experiments and computer simulations. In this study, the initial mass distribution is modified using different wire sizes within the same array, in contrast to the most standard wire arrays. Since the ablation rate of a particular wire material is related to current driver characteristics but not to the wire size, the use of different wires within an array produces time differences for complete ablation of each size. This changes the plasma dynamics and precursor plasma formation as compared to standard arrays. The experiments have been carried out on the Llampudken pulsed power generator (~350kA in ~300ns) using a 1:6 mass ratio among different wires of a single array. Plasma dynamics are studied using time-resolved laser interferometry (532nm, 5ns FWHM) and XUV imaging (5ns exposure time) in both side-on and end-on directions respect to the array. Experimental results show the formation of a dense, precursor plasma column on the array axis at early times, which shifts its position toward the thicker wires at later times at velocities of the order of 104 m/s. Numerical simulations using the 3-D MHD code GORGON are able to reproduce the experimental observations. They show that the larger mass of thicker wires induces modifications in the global magnetic field topology, producing the shifting in the precursor position as observed in the experiments. Further details on the changes of ablation dynamics and precursor formation are presented and discussed.

A suite of laser based diagnostics is used to study interactions of magnetised, supersonic, radiatively cooled plasma flows produced using the Magpie pulse power generator (1.4 MA, 240 ns rise time). Collective optical Thomson scattering measures the time-resolved local flow velocity and temperature across 7-14 spatial positions. The scattering spectrum is recorded from multiple directions, allowing more accurate reconstruction of the flow velocity vectors. The areal electron density is measured using 2D interferometry; optimisation and analysis are discussed. The Faraday rotation diagnostic, operating at 1053 nm, measures the magnetic field distribution in the plasma. Measurements obtained simultaneously by these diagnostics are used to constrain analysis, increasing the accuracy of interpretation.

International audience; We present experimental results on the formation of supersonic, radiatively cooled jets driven by the toroidal magnetic field generated by the 1.5 MA, 250 ns current from the MAGPIE generator. The morphology of the jet produced in the experiments is relevant to astrophysical jet scenarios in which the jet on the axis of a magnetic cavity expanding into an ambient medium is collimated by a toroidal magnetic field. The jets in our experiments have similar Mach number, plasma beta and cooling parameter to those in protostellar jets and additionally the Reynolds, magnetic Reynolds and Peclet numbers are much larger than unity, allowing the experiments to be scaled to astrophysical flows. The experimental configuration generates episodic magnetic cavities, suggesting that periodic formation of jets in astrophysical situations could be responsible for some of the variability observed in astrophysical jets. The dynamics of the formation of laboratory jets are presented, together with new results including preliminary measurements of magnetic, kinetic and Poynting energy of the outflows. In addition first estimates of jet temperature and trapped toroidal magnetic field are presented and discussed.

A detailed study of the radiative precursor that develops ahead of converging blast waves in gas-filled cylindrical liner z-pinch experiments is presented. The experiment is capable of magnetically driving 20 km s−1 blast waves through gases of densities of the order 10−5 g cm−3 (see Burdiak et al. [High Energy Density Phys. 9(1), 52–62 (2013)] for a thorough description). Data were collected for Ne, Ar, and Xe gas-fills. The geometry of the setup allows a determination of the plasma parameters both in the precursor and across the shock, along a nominally uniform line of sight that is perpendicular to the propagation of the shock waves. Radiation from the shock was able to excite NeI, ArII, and XeII/XeIII precursor spectral features. It is shown that the combination of interferometry and optical spectroscopy data is inconsistent with upstream plasmas being in LTE. Specifically, electron density gradients do not correspond to any apparent temperature change in the emission spectra. Experimental data are compared to 1D radiation hydrodynamics HELIOS-CR simulations and to PrismSPECT atomic physics calculations to assist in a physical interpretation of the observations. We show that upstream plasma is likely in the process of being radiatively heated and that the emission from a small percentage of ionised atoms within a cool background plasma dominates the emission spectra. Experiments were carried out on the MAGPIE and COBRA pulsed-power facilities at Imperial College London and Cornell University, respectively.

Shock-less dynamics were observed during the ablation phase in tungsten wire array experiments carried out on the 1.4 MA, 240 ns MAGPIE generator at Imperial College London. This behaviour contrasts with the shock structures which were seen to dominate in previous experiments on aluminium arrays [Swadling et al., Phys. Plasmas 20, 022705 (2013)]. In this paper, we present experimental results and make comparisons both with calculations of the expected mean free paths for collisions between the ablation streams and with previously published Thomson scattering measurements of the plasma parameters in these arrays [Harvey-Thompson et al., Phys. Plasmas 19, 056303 (2012)].

International audience; Laboratory astrophysics is a novel approach to study different types of astrophysical phenomena by the means of carefully scaled laboratory experiments. Particularly, the formation of highly supersonic, radiatively cooled plasma jets for the study of protostellar jets is an active area of research at present. At Imperial College London, different experimental configurations allow producing plasma flows which are scalable to protostellar jets. The plasma is produced by introducing a ~1.4 MA, 250 ns current pulse from the MAGPIE generator into a load. By varying the geometry of the load it is possible to study different regions of interest in the jet. For instance, the effect of magnetic fields in the launching and collimation of the jet, and the propagation of the jet far away from the launching region as it interacts with the ambient medium. Two main experiments can address such regions of interest: radial wire arrays and radial foils. By using a radial wire array it is possible to produce a jet driven by a predominant toroidal magnetic field on the axis of a magnetic "bubble", which expands with velocities up to ~300 km/s. In a radial foil the wires are replaced by a continuous disk allowing to produce a hydrodynamic jet, i.e. a jet in which magnetic fields are not dynamically significant. With this particular configuration it is possible to introduce a neutral gas above the foil in order to study jet-ambient interactions. Experimental results from different diagnostics will be presented together with 3-D MHD simulations using the GORGON code.

A Thomson scattering diagnostic has been used to measure the parameters of cylindrical wire array Z pinch plasmas. The scattering operates in the collective regime (α>1) allowing spatially localised measurements of the ion or electron plasma temperatures and of the plasma bulk velocity. The ablation flow is found to accelerate towards the axis reaching peak velocities of 1.2–1.3 × 107 cm/s in aluminium and ∼1 × 107 cm/s in tungsten arrays. Measurements of the precursor ion temperature shortly after formation are found to correspond to the kinetic energy of the converging ablation flow. Measurements during the implosion phase of tungsten arrays show the main imploding mass reaches velocities of ∼1.4–1.7 × 107 cm/s and is non-zero even at large radii close to the start of the x-ray pulse indicating current flow in the trailing mass.