Miguel Escalona

Gas-puff Z pinches are pulsed-power-driven plasma implosions used as compact laboratory sources of soft X rays and fusion neutrons and as a platform for magneto-inertial fusion research. When a pre-embedded axial magnetic field is applied, the implosion becomes intrinsically three-dimensional, with radial compression, self-generated rotation, and (in the presence of zippering) axial flow all contributing to the dynamics and to the energy balance of the pinch. Simultaneous resolution of all three velocity components is therefore essential for a complete description. We present the first simultaneous, spatially resolved measurement of all three velocity components (radial, azimuthal, and axial) in an annular magnetized argon gas-puff Z-pinch, performed using collective Thomson scattering along three orthogonal lines of sight from the same scattering volume at each time step. Measurements were carried out on the Llampüdkeñ pulse-power generator (400 kA peak, 200 ns rise time), for applied axial fields ranging from 0.04 to 0.26 T using two coil configurations: a double coil with negligible initial radial field at the probed plane (z = 8 mm) and a single coil that imposes a finite initial radial field. Three principal results are reported. First, the axial velocity component, which had not previously been measured experimentally in this configuration, reaches 60–70 km/s near the axis at low applied fields (Bz0 < 0.1 T) and is suppressed to within ±20 km/s for stronger applied fields, in correlation with the reduction of the zippering angle, with direct implications for the implosion energy balance. Second, the self-generated rotation extends across the full plasma diameter, not only at the periphery, and the diametrical profile of the azimuthal velocity decreases toward the axis nonlinearly, consistent with the underlying current density distribution; this feature was not visible in previous edge-localized measurements. Third, rotation persists in the double-coil case (Br0 ≈ 0) and is enhanced in the single-coil case (finite Br0), supporting the interpretation that Br develops self-consistently during the implosion and drives the rotation through a Jz × Br torque. These results constrain the role of each magnetic-field component and motivate direct measurement of Br and the current density distribution as the next step.

The influence of conical wire array geometry on the formation and dynamics of pulsed-power driven plasma jets is investigated. In the experiments, the jet becomes isolated from the inflows as it passes through an aperture, allowing the study of its intrinsic evolution for different conical angles. Our results show that, regardless of the array opening angle, the jets are supersonic, highly collisional, and exhibit an exponential axial density decay with a characteristic scale length of L_{n}≈3mm, significantly shorter than the overall length of the jet. In contrast, axial velocity systematically increases with larger array opening angles. The near invariance of the density profile is attributed to a compensating mechanism between geometric divergence and axial acceleration, consistent with an asymptotically steady flow regime. Additionally, temperature measurements reveal ion-electron thermal decoupling near the base of the jet, with equilibration downstream. Analysis of radiative cooling and collisional energy exchange timescales indicates that the plasma evolves in a radiatively stable regime and that the two-temperature profile is fully described by the competition between both methods. These findings provide valuable information into the internal structure and evolution of pulsed-power plasma jets in regimes dominated by geometric shaping and radiative cooling, demonstrating experimental control over flow acceleration and collimation relevant to both laboratory and astrophysical contexts.

Currently, one of the main interests of the plasma physics community that reproduces astrophysical scenarios on a laboratory scale is the characterization of the magnetization and dynamics of plasmas. Due to its advantages in spatial resolution, the Faraday rotation technique is one of the most widely used techniques for characterizing the magnetic field within the plasma. However, the technique requires knowledge of the density map along the direction of the scene beam, which imposes the challenge of implementing simultaneous interferometric and polarimetric setups, along with additional reference recordings. This manuscript proposes a digital recording interferometric setup, in addition to a digital processing and analysis technique, based on two simultaneous digital interferometric recording, with which information on phase shift and the polarization rotation angle of a coherent beam passing through a magnetized plasma can be obtained. The reconstruction technique for the interferometric phase and the polarogram proposed here is independent of the wavefront intensities in each arm of the interferometer, thus eliminating the need for a second exposure without the influence of the magnetized plasma. The technique is digitally tested with simulated wavefronts, where the scene beam passes through a plasma column, as expected in the pinch phase of a plasma focus discharge of a few hundred joules. In this way, the results allow us to evaluate the application of the technique in small PF discharges, with currents around 100 kA and plasma column diameters of sub-millimeter size.

In this study, we present a novel method for fabricating semi-transparent electrodes by combining silver nanowires (AgNW) with titanium nitride (TiN) layers, resulting in conductive nanocomposite coatings with exceptional electromechanical properties. These nanocomposites were deposited on cellulose nanopaper (CNP) using a plasma-enhanced pulsed laser deposition (PE-PLD) technique at low temperatures (below 200 °C). Repetitive bending tests demonstrate that incorporating AgNW into TiN coatings significantly enhances the microstructure, increasing the electrode’s electromechanical robustness by up to four orders of magnitude compared to commercial PET/ITO substrates. Furthermore, the optical and electrical conductivities can be optimized by adjusting the AgNW network density and TiN synthesis temperature. Our results also indicate that the nanocomposite electrodes exhibit improved stability in air and superior adhesion compared to bare AgNW coatings.

In this study, we present a novel method for fabricating semi-transparent electrodes by combining silver nanowires (AgNW) with titanium nitride (TiN) layers, resulting in conductive nano-composite coatings with exceptional electro-mechanical properties. These nano-composites were deposited on cellulose nanopaper (CNP) using a plasma-enhanced pulsed laser deposition (PE-PLD) technique at low temperatures (below 200°C). Repetitive bending tests demonstrate that incorporating AgNW into TiN coatings significantly enhances the microstructure, increasing the electrodes electro-mechanical robustness by up to four orders of magnitude compared to commercial PET/ITO substrates. Furthermore, the optical and electrical conductivities can be optimized by adjusting the AgNW network density and TiN synthesis temperature. Our results also indicate that the nanocomposite electrodes exhibit improved stability in air and superior adhesion compared to bare AgNW coatings. These findings are crucial for advancing bio-compatible flexible electronics and could lead to the development of new wearable and implantable medical devices.

Experimental studies of the dynamics and properties of laser produced plasmas in different initial configurations, using a Titanium target and a Nitrogen background, are presented. First, an annular plasma, produced by focusing a 5 ns laser beam using a combination of axicon prism and convergent lens and expanding in neutral Nitrogen background, in the range 50-2000 mTorr, is characterized using 30 ps simultaneous Mach-Zehnder interferometry, shadowgraph and schlieren imaging. Second, a plasma plume, produced by point focusing of a 4.8 ns laser beam and expanding in 50-1000 mTorr Nitrogen background, either neutral or in a RF produced plasma, is characterized with 4 ns Mach-Zehnder interferometry. Detailed time resolved measurements of the plasma density, as a result of Abel inversion of the interferograms, with characteristic plasma densities ~5×10 15 -1×10 17 cm -3, , and plasma dynamics resulting from shadowgraph and schlieren imaging, will be presented and discussed.

The production of an interacting region of plasmas using laser-produced plasma plumes and jet-like plasma outflows emitted by a conical wire array Z-pinch is experimentally studied. The jet-like outflow is produced by a conical wire array of 16 aluminum wires (40μm diameter each) acting as load of the Llampudken generator (~400kA, ~350ns). The laser plasma plume (LPP) is produced by focusing a 10 10 W/cm 2 laser pulse onto an aluminum target. The target for LPP is located above the anode, parallel to the axis where jet-like plasma outflow propagates. To avoid direct exposure of the target from any emission aside from the jet-like plasma, a thick metallic lid is used as blockage for the array load. The primary diagnostic is laser interferometry aligned with the target surface. Our experimental results show that in the absence of LPP, there is no significant propagation nor interaction of the photoionized ablated target surface with the jet-like plasma. On the contrary, when combining both plasma sources, a new structure appears in the region where both plasmas interact. The thickness of this structure agrees with ion-ion mean free path calculations suggesting the presence of a shock layer created after the interaction. Further details and potential applications will be shown and discussed.

Preionization is believed to play an important role on the implosion of gas-puff Z-pinches. Some experiments have used an external preionization source, e.g., UV light or electron beam. In contrast, other experiments rely completely on overvoltage breakdown by the own generator’s voltage pulse. But the problem with this approach is that it might not produce reliable results because self-breakdown is mainly a stochastic process. In order to study reproducibility, we performed systematic studies on self-breakdown using two different cathode geometries: i) a smooth, round cathode to provide a homogenous electric field ii) a sharp, knife-edge-like geometry to enhance the electric field locally and eventually electron emission. The experiments were carried out on the Llampudken current generator, which provides a current pulse of ~400kA amplitude and 200ns rise time (10%-90%). We implemented gated XUV imaging, laser probing, filtered diodes and time-integrated X-ray imaging to obtain information about the implosion as well as the stagnation phase for the two cathode geometries. Preliminary analysis shows that erosion of the knife-edge cathode may be a serious problem, and on the contrary, the round cathode may have far more reliable results. Data is currently analyzed and further details will be shown and discussed.