Jack Davies Hare

Jack Davies Hare
Massachusetts Institute of Technology | MIT · Plasma Science and Fusion Center (PSFC)

PhD

About

41
Publications
3,556
Reads
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322
Citations
Introduction
I am an assistant professor at the Nuclear Science and Engineering department at MIT, using pulsed-power to study fundamental processes in plasmas. Previously, I was a Research Associate at Imperial College London, working on the Mega Ampere Generator for Plasma Implosion Experiments (MAGPIE). I completed my PhD in 2017, in which I studied magnetic reconnection studies in pulsed power driven plasmas. As part of my post doc I looked at generating magnetised turbulence using pulsed power.
Additional affiliations
January 2021 - present
Massachusetts Institute of Technology
Position
  • Professor (Assistant)
March 2019 - present
Max Planck Institute for Plasma Physics
Position
  • PostDoc Position
March 2017 - March 2019
Imperial College London
Position
  • Research Associate
Education
September 2013 - March 2017
Imperial College London
Field of study
  • Plasma Physics
September 2011 - June 2013
Princeton University
Field of study
  • Plasma Physics
October 2007 - June 2011
University of Cambridge
Field of study
  • Natural Sciences

Publications

Publications (41)
Article
We present a detailed study of magnetic reconnection in a quasi-two-dimensional pulsed-power driven laboratory experiment. Oppositely directed magnetic fields $(B=3$ T), advected by supersonic, sub-Alfv\'enic carbon plasma flows $(V_{in}=50$ km/s), are brought together and mutually annihilate inside a thin current layer ($\delta=0.6$ mm). Temporall...
Article
We describe magnetic reconnection experiments using a new, pulsed-power driven experimental platform in which the inflows are super-sonic but sub-Alfv\'enic.The intrinsically magnetised plasma flows are long lasting, producing a well-defined reconnection layer that persists over many hydrodynamic time scales.The layer is diagnosed using a suite of...
Article
Full-text available
We describe a versatile pulsed-power driven platform for magnetic reconnection experiments, based on exploding wire arrays driven in parallel [Suttle, L. G. et al. PRL, 116, 225001]. This platform produces inherently magnetised plasma flows for the duration of the generator current pulse (250 ns), resulting in a long-lasting reconnection layer. The...
Preprint
We present experimental measurements of a pulsed plasma gun, using two-colour imaging laser interferometry and spatially resolved Thomson scattering. Interferometry measurements give an electron density $n_e\approx2.7\times10^{17}$ cm$^{-3}$ at the centre of the plasma plume, at 5 mm from the plasma gun nozzle. The Thomson scattered light is collec...
Preprint
Magnetic reconnection is a ubiquitous and fundamental process in plasmas by which magnetic fields change their topology and release magnetic energy. Despite decades of research, the physics governing the reconnection process in many parameter regimes remains controversial. Contemporary reconnection theories predict that long, narrow current sheets...
Preprint
Full-text available
We present a technique to measure the time-resolved velocity and ion sound speed in magnetized, supersonic high-energy-density plasmas. We place an inductive (`b-dot') probe in a supersonic pulsed-power-driven plasma flow and measure the magnetic field advected by the plasma. As the magnetic Reynolds number is large ($R_M > 10$), the plasma flow ad...
Preprint
Full-text available
We present results from pulsed-power driven differentially rotating plasma experiments designed to simulate physics relevant to astrophysical disks and jets. In these experiments, angular momentum is injected by the ram pressure of the ablation flows from a wire array Z pinch. In contrast to previous liquid metal and plasma experiments, rotation is...
Preprint
Full-text available
We present a study of perpendicular subcritical shocks in a collisional laboratory plasma. Shocks are produced by placing obstacles into the super-magnetosonic outflow from an inverse wire array z-pinch. We demonstrate the existence of subcritical shocks in this regime and find that secondary shocks form in the downstream. Detailed measurements of...
Article
A diagnostic capable of recording spatially and temporally resolved x-ray self-emission data was developed to characterize experiments on the MAGPIE pulsed-power generator. The diagnostic used two separate imaging systems: a pinhole imaging system with two-dimensional spatial resolution and a slit imaging system with one-dimensional spatial resolut...
Preprint
Full-text available
A diagnostic capable of recording spatially and temporally resolved X-ray self emission data was developed to characterise experiments on the MAGPIE pulsed-power generator. The diagnostic used two separate imaging systems: A pinhole imaging system with two dimensional spatial resolution and a slit imaging system with one dimensional spatial resolut...
Article
Full-text available
We analyze, using experiments and 3D MHD numerical simulations, the dynamic and radiative properties of a plasma ablated by a laser (1 ns, 10 $$^{12}$$ 12 –10 $$^{13}$$ 13 W/cm $$^2$$ 2 ) from a solid target as it expands into a homogeneous, strong magnetic field (up to 30 T) that is transverse to its main expansion axis. We find that as early as 2...
Article
We report on a recently developed laser-probing diagnostic, which allows direct measurements of ray-deflection angles in one axis while retaining imaging capabilities in the other axis. This allows us to measure the spectrum of angular deflections from a laser beam, which passes through a turbulent high-energy-density plasma. This spectrum contains...
Article
Full-text available
Optical collective Thomson scattering (TS) is used to diagnose magnetized high energy density physics experiments at the Magpie pulsed-power generator at Imperial College London. The system uses an amplified pulse from the second harmonic of a Nd:YAG laser (3 J, 8 ns, 532 nm) to probe a wide diversity of high-temperature plasma objects, with densit...
Preprint
Full-text available
Magnetic reconnection underlies many explosive phenomena in the heliosphere and in laboratory plasmas. The new research capabilities in theory/simulations, observations, and laboratory experiments provide the opportunity to solve the grand scientific challenges summarized in this whitepaper. Success will require enhanced and sustained investments f...
Preprint
We report on a recently developed laser-based diagnostic which allows direct measurements of ray-deflection angles in one axis, whilst retaining imaging capabilities in the other axis. This allows us to measure the spectrum of angular deflections from a laser beam which passes though a turbulent high-energy-density plasma. This spectrum contains in...
Preprint
Full-text available
We analyze, using experiments and 3D MHD numerical simulations, the dynamics and radiative properties of a plasma ablated by a laser (1 ns, 10$^{12}$-10$^{13}$ W/cm$^2$) from a solid target, as it expands into a homogeneous, strong magnetic field (up to 30 T) transverse to its main expansion axis. We find that as soon as 2 ns after the start of the...
Article
Full-text available
A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the J × B acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving curr...
Preprint
Full-text available
A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the JxB acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving curren...
Article
We present a new experimental platform for studying radiative shocks using an “inverse liner z-pinch” configuration. This platform was tested on the MAGPIE pulsed power facility (~1 MA with a rise time of ~240 ns) at Imperial College London, U.K. Current is discharged through a thin-walled metal tube (a liner) embedded in a low-density gas-fill and...
Article
Full-text available
This work presents a magnetic reconnection experiment in which the kinetic, magnetic and thermal properties of the plasma each play an important role in the overall energy balance and structure of the generated reconnection layer. Magnetic reconnection occurs during the interaction of continuous and steady flows of super-Alfvenic, magnetized, alumi...
Article
We present an experimental study of the development and structure of bow shocks produced by the interaction of a magnetised, collisional, super-Alfvénic plasma flow with conducting cylindrical obstacles. The plasma flow with an embedded, frozen-in magnetic field (ReM ∼ 20) is produced by the current-driven ablation of fine aluminium wires in an inv...
Article
The paper presents short summaries and a synopsis of two completely independent discoveries of a fast flow braking process, one realized by a laboratory experiment (Lebedev et al 2014 Phys. Plasmas 21 056305), the other by theoretical reasoning stimulated by auroral observation (Haerendel 2015a J. Geophys. Res. Space Phys. 120 1697–714). The first...
Conference Paper
We present results from magnetised bow shock experiments performed on the Magpie (∼1 MA, 250 ns) pulsed-power facility. Bow shocks are formed around cylindrical conducting obstacles (diameter ∼0.5 mm) positioned in a supersonic, super-Alfenic, plasma flow (MS > 3, MA > 2.5, Vflow ∼70 km/s). This radially diverging flow is produced by an exploding w...
Conference Paper
The use of plasma flows generated by pulsed power facilities provides a natural platform for designing magnetized HEDLA experiments. The plasma in this case is created and accelerated by the JxB force of the driving, ∼Mega-Ampere level currents, forming plasma flows with embedded, frozen-in magnetic fields. Here we present several recent experiment...
Article
We present experiments characterizing the detailed structure of a current layer, generated by the collision of two counterstreaming, supersonic and magnetized aluminum plasma flows. The antiparallel magnetic fields advected by the flows are found to be mutually annihilated inside the layer, giving rise to a bifurcated current structure—two narrow c...
Article
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. Thi...
Article
A gas-filled cylindrical liner z-pinch configuration has been used to drive convergent radiative shock waves into different gases at velocities of 20–50 km s −1 . On application of the 1.4 MA, 240 ns rise-time current pulse produced by the Magpie generator at Imperial College London, a series of cylindrically convergent shock waves are sequentially...
Article
We present data from the first Z-pinch experiments aiming to simulate aspects of accretion disk physics in the laboratory. Using off axis ablation flows from a wire array z-pinch we demonstrate the formation of a supersonically (M ∼ 2) rotating hollow plasma cylinder of height ∼4 mm and radius 2 mm. Using a combination of diagnostics we measure the...
Article
An experiment is presented in which the x-ray emission from a stagnated wire array z-pinch is used to photo-ionise gas inside a gas cell. Photo-ionisation studies with x-rays from wire array implosions on the Z facility at Sandia National Labs used a gas cell positioned side-on and at large distances from the pinch 1 . Due to the much smaller radia...
Article
Full-text available
We present data from the first z-pinch experiments aiming to simulate aspects of accretion disk physics in the laboratory. Using off axis ablation flows from a wire array z-pinch we demonstrate the formation of a hollow disk structure that rotates at 60 kms-1 for 150 ns. By analysing the Thomson scattered spectrum we make estimates for the ion and...
Article
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 spe...
Article
Full-text available
A new experimental platform was developed, based on the use of supersonic plasma flow from the ablation stage of an inverse wire array z-pinch, for studies of shocks in magnetized high energy density physics plasmas in a well-defined and diagnosable 1-D interaction geometry. The mechanism of flow generation ensures that the plasma flow (ReM ∼ 50, M...
Conference Paper
The latest data from gas-filled cylindrical liner z-pinch experiments performed on the MAGPIE facility at Imperial College London (1.4MA, 240ns) are presented. The MAGPIE current is applied to thin-walled (100um) tubes with a static gas-fill inside (initial gas density 1E-5 g/cc). The system is used to drive cylindrically converging strong shock wa...
Article
The Lithium Tokamak eXperiment (LTX) is a spherical tokamak with the unique capability of studying the low-recycling regime by coating nearly 90% of the first wall with lithium in either solid or liquid form. Several grams of lithium are evaporated onto the plasma-facing side of the first wall. Without lithium coatings, the plasma discharge is limi...
Article
Full-text available
The Lithium Tokamak eXperiment is a small, low aspect ratio tokamak [Majeski et al., Nucl. Fusion 49, 055014 (2009)], which is fitted with a stainless steel-clad copper liner, conformal to the last closed flux surface. The liner can be heated to 350 °C. Several gas fueling systems, including supersonic gas injection and molecular cluster injection,...
Presentation
The Lithium Tokamak eXperiment (LTX) is a spherical tokamak for investigating the low-recycling regime achieved with lithium plasma-facing components (PFCs). They consist of a stainless steel liner on copper plates that form a shell conformal to the last closed flux surface of the LTX design equilibrium. The liner is coated with lithium, and discha...
Presentation
The Lithium Tokamak Experiment (LTX) investigates Li coatings as the main plasma-facing component (PFC) which are expected to reduce ion impurity content in the plasmas. High densities of impurity ions, such as C, O, Fe, and even Li, may cool the plasmas by line radiation. Presently, solid lithium is used in LTX, but soon liquid Li will be tested a...
Article
Full-text available
We show that the positioning of a nanometer length scale dielectric object, such as a diamond nanocrystal, in the vicinity of a gold bowtie nanoantenna can be used to tune the plasmonic mode spectrum on the order of a linewidth. We further show that the intrinsic luminescence of gold enhanced in the presence of nanometer-scale roughness couples eff...

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