Imperial College London

Prof. Jeremy Chittenden

Faculty of Natural SciencesDepartment of Physics

Professor of Plasma Physics
 
 
 
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Contact

 

+44 (0)20 7594 7654j.chittenden Website

 
 
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Location

 

744Blackett LaboratorySouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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358 results found

Datta R, Chandler K, Myers CE, Chittenden JP, Crilly AJ, Aragon C, Ampleford DJ, Banasek JT, Edens A, Fox WR, Hansen SB, Harding EC, Jennings CA, Ji H, Kuranz CC, Lebedev SV, Looker Q, Patel SG, Porwitzky A, Shipley GA, Uzdensky DA, Yager-Elorriaga DA, Hare JDet al., 2024, Radiatively cooled magnetic reconnection experiments driven by pulsed power, Physics of Plasmas, Vol: 31, ISSN: 1070-664X

<jats:p>We present evidence for strong radiative cooling in a pulsed-power-driven magnetic reconnection experiment. Two aluminum exploding wire arrays, driven by a 20 MA peak current, 300 ns rise time pulse from the Z machine (Sandia National Laboratories), generate strongly driven plasma flows (MA≈7) with anti-parallel magnetic fields, which form a reconnection layer (SL≈120) at the mid-plane. The net cooling rate far exceeds the Alfvénic transit rate (τcool−1/τA−1≫1), leading to strong cooling of the reconnection layer. We determine the advected magnetic field and flow velocity using inductive probes positioned in the inflow to the layer, and inflow ion density and temperature from analysis of visible emission spectroscopy. A sharp decrease in x-ray emission from the reconnection layer, measured using filtered diodes and time-gated x-ray imaging, provides evidence for strong cooling of the reconnection layer after its initial formation. X-ray images also show localized hotspots, regions of strong x-ray emission, with velocities comparable to the expected outflow velocity from the reconnection layer. These hotspots are consistent with plasmoids observed in 3D radiative resistive magnetohydrodynamic simulations of the experiment. X-ray spectroscopy further indicates that the hotspots have a temperature (170 eV) much higher than the bulk layer (≤75 eV) and inflow temperatures (about 2 eV) and that these hotspots generate the majority of the high-energy (&amp;gt;1 keV) emission.</jats:p>

Journal article

Datta R, Crilly A, Chittenden JP, Chowdhry S, Chandler K, Chaturvedi N, Myers CE, Fox WR, Hansen SB, Jennings CA, Ji H, Kuranz CC, Lebedev SV, Uzdensky DA, Hare JDet al., 2024, Simulations of radiatively cooled magnetic reconnection driven by pulsed power, Journal of Plasma Physics, Vol: 90, ISSN: 0022-3778

Magnetic reconnection is an important process in astrophysical environments, as it reconfigures magnetic field topology and converts magnetic energy into thermal and kinetic energy. In extreme astrophysical systems, such as black hole coronae and pulsar magnetospheres, radiative cooling modifies the energy partition by radiating away internal energy, which can lead to the radiative collapse of the reconnection layer. In this paper, we perform two- and three-dimensional simulations to model the MARZ (Magnetic Reconnection on Z) experiments, which are designed to access cooling rates in the laboratory necessary to investigate reconnection in a previously unexplored radiatively cooled regime. These simulations are performed in GORGON, an Eulerian two-temperature resistive magnetohydrodynamic code, which models the experimental geometry comprising two exploding wire arrays driven by 20 MA of current on the Z machine (Sandia National Laboratories). Radiative losses are implemented using non-local thermodynamic equilibrium tables computed using the atomic code Spk, and we probe the effects of radiation transport by implementing both a local radiation loss model and multi-group radiation transport. The load produces highly collisional, super-Alfvénic (Alfvén Mach number), supersonic (Sonic Mach number) strongly driven plasma flows which generate an elongated reconnection layer (Aspect Ratio, Lundquist number). The reconnection layer undergoes radiative collapse when the radiative losses exceed the rates of ohmic and compressional heating (cooling rate/hydrodynamic transit rate =); this generates a cold strongly compressed current sheet, leading to an accelerated reconnection rate, consistent with theoretical predictions. Finally, the current sheet is also unstable to the plasmoid instability, but the magnetic islands are extinguished by strong radiative cooling before ejection from the layer.

Journal article

Datta R, Chandler K, Myers CE, Chittenden JP, Crilly AJ, Aragon C, Ampleford DJ, Banasek JT, Edens A, Fox WR, Hansen SB, Harding EC, Jennings CA, Ji H, Kuranz CC, Lebedev SV, Looker Q, Patel SG, Porwitzky A, Shipley GA, Uzdensky DA, Yager-Elorriaga DA, Hare JDet al., 2024, Plasmoid formation and strong radiative cooling in a driven magnetic reconnection experiment, Physical Review Letters, Vol: 132, ISSN: 0031-9007

We present the first experimental study of plasmoid formation in a magnetic reconnection layer undergoing rapid radiative cooling, a regime relevant to extreme astrophysical plasmas. Two exploding aluminum wire arrays, driven by the Z machine, generate a reconnection layer (S_{L}≈120) in which the cooling rate far exceeds the hydrodynamic transit rate (τ_{hydro}/τ_{cool}>100). The reconnection layer generates a transient burst of >1  keV x-ray emission, consistent with the formation and subsequent rapid cooling of the layer. Time-gated x-ray images show fast-moving (up to 50  km s^{-1}) hotspots in the layer, consistent with the presence of plasmoids in 3D resistive magnetohydrodynamic simulations. X-ray spectroscopy shows that these hotspots generate the majority of Al K-shell emission (around 1.6 keV) prior to the onset of cooling, and exhibit temperatures (170 eV) much greater than that of the plasma inflows and the rest of the reconnection layer, thus providing insight into the generation of high-energy radiation in radiatively cooled reconnection events.

Journal article

Crilly AJ, Schlossberg DJ, Appelbe BD, Moore AS, Jeet J, Kerr S, Rubery M, Lahmann B, O'Neill S, Forrest CJ, Mannion OM, Chittenden JPet al., 2024, Measurements of dense fuel hydrodynamics in the NIF burning plasma experiments using backscattered neutron spectroscopy, Physics of Plasmas, Vol: 31, ISSN: 1070-664X

The hydrodynamics of the dense confining fuel shell is of great importance in defining the behavior of the burning plasma and burn propagation regimes of inertial confinement fusion experiments. However, it is difficult to probe due to its low emissivity in comparison with the central fusion core. In this work, we utilize the backscattered neutron spectroscopy technique to directly measure the hydrodynamic conditions of the dense fuel during fusion burn. Experimental data are fit to obtain dense fuel velocities and apparent ion temperatures. Trends of these inferred parameters with yield and velocity of the burning plasma are used to investigate their dependence on alpha heating and low mode drive asymmetry. It is shown that the dense fuel layer has an increased outward radial velocity as yield increases, showing that burn has continued into re-expansion, a key signature of hotspot ignition. A comparison with analytic and simulation models shows that the observed dense fuel parameters are displaying signatures of burn propagation into the dense fuel layer, including a rapid increase in dense fuel apparent ion temperature with neutron yield.

Journal article

Abu-Shawareb H, Acree R, Adams P, Adams J, Addis B, Aden R, Adrian P, Afeyan BB, Aggleton M, Aghaian L, Aguirre A, Aikens D, Akre J, Albert F, Albrecht M, Albright BJ, Albritton J, Alcala J, Alday C, Alessi DA, Alexander N, Alfonso J, Alfonso N, Alger E, Ali SJ, Ali ZA, Allen A, Alley WE, Amala P, Amendt PA, Amick P, Ammula S, Amorin C, Ampleford DJ, Anderson RW, Anklam T, Antipa N, Appelbe B, Aracne-Ruddle C, Araya E, Archuleta TN, Arend M, Arnold P, Arnold T, Arsenlis A, Asay J, Atherton LJ, Atkinson D, Atkinson R, Auerbach JM, Austin B, Auyang L, Awwal AAS, Aybar N, Ayers J, Ayers S, Ayers T, Azevedo S, Bachmann B, Back CA, Bae J, Bailey DS, Bailey J, Baisden T, Baker KL, Baldis H, Barber D, Barberis M, Barker D, Barnes A, Barnes CW, Barrios MA, Barty C, Bass I, Batha SH, Baxamusa SH, Bazan G, Beagle JK, Beale R, Beck BR, Beck JB, Bedzyk M, Beeler RG, Beeler RG, Behrendt W, Belk L, Bell P, Belyaev M, Benage JF, Bennett G, Benedetti LR, Benedict LX, Berger RL, Bernat T, Bernstein LA, Berry B, Bertolini L, Besenbruch G, Betcher J, Bettenhausen R, Betti R, Bezzerides B, Bhandarkar SD, Bickel R, Biener J, Biesiada T, Bigelow K, Bigelow-Granillo J, Bigman V, Bionta RM, Birge NW, Bitter M, Black AC, Bleile R, Bleuel DL, Bliss E, Bliss E, Blue B, Boehly T, Boehm K, Boley CD, Bonanno R, Bond EJ, Bond T, Bonino MJ, Borden M, Bourgade J-L, Bousquet J, Bowers J, Bowers M, Boyd R, Boyle D, Bozek A, Bradley DK, Bradley KS, Bradley PA, Bradley L, Brannon L, Brantley PS, Braun D, Braun T, Brienza-Larsen K, Briggs R, Briggs TM, Britten J, Brooks ED, Browning D, Bruhn MW, Brunner TA, Bruns H, Brunton G, Bryant B, Buczek T, Bude J, Buitano L, Burkhart S, Burmark J, Burnham A, Burr R, Busby LE, Butlin B, Cabeltis R, Cable M, Cabot WH, Cagadas B, Caggiano J, Cahayag R, Caldwell SE, Calkins S, Callahan DA, Calleja-Aguirre J, Camara L, Camp D, Campbell EM, Campbell JH, Carey B, Carey R, Carlisle K, Carlson L, Carman L, Carmichael J, Carpenter A, Carr C, Carrera JA, Casavant D, Casey Aet al., 2024, Achievement of target gain larger than unity in an inertial fusion experiment, Physical Review Letters, Vol: 132, Pages: 1-16, ISSN: 0031-9007

On December 5, 2022, an indirect drive fusion implosion on the National Ignition Facility (NIF) achieved a target gain G_{target} of 1.5. This is the first laboratory demonstration of exceeding "scientific breakeven" (or G_{target}>1) where 2.05 MJ of 351 nm laser light produced 3.1 MJ of total fusion yield, a result which significantly exceeds the Lawson criterion for fusion ignition as reported in a previous NIF implosion [H. Abu-Shawareb et al. (Indirect Drive ICF Collaboration), Phys. Rev. Lett. 129, 075001 (2022)PRLTAO0031-900710.1103/PhysRevLett.129.075001]. This achievement is the culmination of more than five decades of research and gives proof that laboratory fusion, based on fundamental physics principles, is possible. This Letter reports on the target, laser, design, and experimental advancements that led to this result.

Journal article

Merlini S, Hare JD, Burdiak GC, Halliday JWD, Ciardi A, Chittenden JP, Clayson T, Crilly AJ, Eardley SJ, Marrow KE, Russell DR, Smith RA, Stuart N, Suttle LG, Tubman ER, Valenzuela-Villaseca V, Varnish TWO, Lebedev SVet al., 2023, Radiative cooling effects on reverse shocks formed by magnetized supersonic plasma flows, Physics of Plasmas, Vol: 30, ISSN: 1070-664X

We study the structure of reverse shocks formed by the collision of supersonic, magnetized plasma flows driven by an inverse (or exploding) wire array with a planar conducting obstacle. We observe that the structure of these reverse shocks varies dramatically with wire material, despite the similar upstream flow velocities and mass densities. For aluminum wire arrays, the shock is sharp and well-defined, consistent with magneto-hydrodynamic theory. In contrast, we do not observe a well-defined shock using tungsten wires, and instead we see a broad region dominated by density fluctuations on a wide range of spatial scales. We diagnose these two very different interactions using interferometry, Thomson scattering, shadowgraphy, and a newly developed imaging refractometer that is sensitive to small deflections of the probing laser corresponding to small-scale density perturbations. We conclude that the differences in shock structure are most likely due to radiative cooling instabilities, which create small-scale density perturbations elongated along magnetic field lines in the tungsten plasma. These instabilities grow more slowly and are smoothed by thermal conduction in the aluminum plasma.

Journal article

Datta R, Angel J, Greenly JB, Bland SN, Chittenden JP, Lavine ES, Potter WM, Robinson D, Varnish TWO, Wong E, Hammer DA, Kusse BR, Hare JDet al., 2023, Plasma flows during the ablation stage of an over-massed pulsed-power-driven exploding planar wire array, PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X

Journal article

Mannion OM, Taitano WT, Appelbe BD, Crilly AJ, Forrest CJ, Glebov VY, Knauer JP, McKenty PW, Mohamed ZL, Stoeckl C, Keenan BD, Chittenden JP, Adrian P, Frenje J, Kabadi N, Gatu Johnson M, Regan SPet al., 2023, Evidence of non-Maxwellian ion velocity distributions in spherical shock-driven implosions., Phys Rev E, Vol: 108

The ion velocity distribution functions of thermonuclear plasmas generated by spherical laser direct drive implosions are studied using deuterium-tritium (DT) and deuterium-deuterium (DD) fusion neutron energy spectrum measurements. A hydrodynamic Maxwellian plasma model accurately describes measurements made from lower temperature (<10 keV), hydrodynamiclike plasmas, but is insufficient to describe measurements made from higher temperature more kineticlike plasmas. The high temperature measurements are more consistent with Vlasov-Fokker-Planck (VFP) simulation results which predict the presence of a bimodal plasma ion velocity distribution near peak neutron production. These measurements provide direct experimental evidence of non-Maxwellian ion velocity distributions in spherical shock driven implosions and provide useful data for benchmarking kinetic VFP simulations.

Journal article

Russell DR, Burdiak GC, Carroll-Nellenback JJ, Halliday JWD, Hare JD, Merlini S, Suttle LG, Valenzuela-Villaseca V, Eardley SJ, Fullalove JA, Rowland GC, Smith RA, Frank A, Hartigan P, Velikovich AL, Chittenden JP, Lebedev SVet al., 2023, Observation of subcritical shocks in a collisional laboratory plasma: scale dependence near the resistive length, Journal of Plasma Physics, Vol: 89, ISSN: 0022-3778

We present a study of subcritical shocks in a highly collisional laboratory plasma with a dynamically significant magnetic field. Shocks were produced by placing cylindrical obstacles into the supermagnetosonic ( MMS∼1.9 ) outflow from an inverse wire array z-pinch at the MAGPIE pulsed power facility ( ne∼8.5×1017cm−3 , v∼45kms−1 ). We demonstrate the existence of subcritical shocks in this regime and find that secondary stagnation shocks form in the downstream which we infer from interferometry and optical Thomson scattering measurements are hydrodynamic in nature. The subcritical shock width is found to be approximately equal to the resistive diffusion length and we demonstrate the absence of a jump in hydrodynamic parameters. Temperature measurements by collective optical Thomson scattering showed little temperature change across the subcritical shock ( <10% of the ion kinetic energy) which is consistent with a balance between adiabatic and Ohmic heating and radiative cooling. We demonstrate the absence of subcritical shocks when the obstacle diameter is less than the resistive diffusion length due to decoupling of the magnetic field from the plasma. These findings are supported by magnetohydrodynamic simulations using the Gorgon and AstroBEAR codes and discrepancies between the simulations and experiment are discussed.

Journal article

Sio H, Moody JD, Pollock BB, Strozzi DJ, Ho DDM, Walsh CA, Kemp GE, Lahmann B, Kucheyev SO, Kozioziemski B, Carroll EG, Kroll J, Yanagisawa DK, Angus J, Bachmann B, Baker AA, Bayu Aji LB, Bhandarkar SD, Bude JD, Divol L, Engwall AM, Ferguson B, Fry J, Hagler L, Hartouni E, Herrmann MC, Hsing W, Holunga DM, Javedani J, Johnson A, Khan S, Kalantar D, Kohut T, Logan BG, Masters N, Nikroo A, Izumi N, Orsi N, Piston K, Provencher C, Rowe A, Sater J, Shin SJ, Skulina K, Stygar WA, Tang V, Winters SE, Zimmerman G, Chittenden JP, Appelbe B, Boxall A, Crilly A, O'Neill S, Barnak D, Davies J, Peebles J, Bae JH, Clark K, Havre M, Mauldin M, Ratledge M, Vonhof S, Adrian P, Reichelt B, Fujioka S, Fraenkel Met al., 2023, Performance scaling with an applied magnetic field in indirect-drive inertial confinement fusion implosions, PHYSICS OF PLASMAS, Vol: 30, ISSN: 1070-664X

Journal article

Crilly AJ, Niasse NPL, Fraser AR, Chapman DA, McLean KW, Rose SJ, Chittenden JPet al., 2023, SpK: A fast atomic and microphysics code for the high-energy-density regime, High Energy Density Physics, Vol: 48, Pages: 1-12, ISSN: 1574-1818

SpK is part of the numerical codebase at Imperial College London used to model high energy density physics (HEDP) experiments. SpK is an efficient atomic and microphysics code used to perform detailed configuration accounting calculations of electronic and ionic stage populations, opacities and emissivities for use in post-processing and radiation hydrodynamics simulations. This is done using screened hydrogenic atomic data supplemented by the NIST energy level database. An extended Saha model solves for chemical equilibrium with extensions for non-ideal physics, such as ionisation potential depression, and non thermal equilibrium corrections. A tree-heap (treap) data structure is used to store spectral data, such as opacity, which is dynamic thus allowing easy insertion of points around spectral lines without a-priori knowledge of the ion stage populations. Results from SpK are compared to other codes and descriptions of radiation transport solutions which use SpK data are given. The treap data structure and SpK’s computational efficiency allows inline post-processing of 3D hydrodynamics simulations with a dynamically evolving spectrum stored in a treap.

Journal article

Valenzuela-Villaseca V, Suttle LG, Suzuki-Vidal F, Halliday JWD, Merlini S, Russell DR, Tubman ER, Hare JD, Chittenden JP, Koepke ME, Blackman EG, Lebedev SVet al., 2023, Characterization of quasi-Keplerian, differentially rotating, free-boundary laboratory plasmas, Physical Review Letters, Vol: 130, ISSN: 0031-9007

We present results from pulsed-power driven differentially rotating plasma experiments designed tosimulate physics relevant to astrophysical disks and jets. In these experiments, angular momentum is injectedby the ram pressure of the ablation flows from a wire array Z pinch. In contrast to previous liquid metal andplasma experiments, rotation is not driven by boundary forces. Axial pressure gradients launch a rotatingplasma jet upward, which is confined by a combination of ram, thermal, and magnetic pressure of asurrounding plasma halo. The jet has subsonic rotation, with a maximum rotation velocity 23 3 km=s. Therotational velocity profile is quasi-Keplerian with a positive Rayleigh discriminant κ2 ∝ r−2.8 0.8 rad2=s2.The plasma completes 0.5–2 full rotations in the experimental time frame (∼150 ns).

Journal article

Strucka J, Lukic B, Koerner M, Halliday JWD, Yao Y, Mughal K, Maler D, Efimov S, Skidmore J, Rack A, Krasik Y, Chittenden J, Bland SNet al., 2023, Synchrotron radiography of Richtmyer–Meshkov instability driven by exploding wire arrays, Physics of Fluids, Vol: 35, Pages: 1-11, ISSN: 1070-6631

We present a new technique for the investigation of shock-driven hydrodynamic phenomena in gases, liquids, and solids in arbitrary geometries. The technique consists of a pulsed power-driven resistive wire array explosion in combination with multi-MHz synchrotron radiography. Compared to commonly used techniques, it offers multiple advantages: (1) the shockwave geometry can be shaped to the requirements of the experiment, (2) the pressure (P > 300 MPa) generated by the exploding wires enables the use of liquid and solid hydrodynamic targets with well-characterized initial conditions (ICs), (3) the multi-MHz radiography enables data acquisition to occur within a single experiment, eliminating uncertainties regarding repeatability of the ICs and subsequent dynamics, and (4) the radiographic measurements enable estimation of compression ratios from the x-ray attenuation. In addition, the use of a synchrotron x-ray source allows the hydrodynamic samples to be volumetrically characterized at a high spatial resolution with synchrotron-based microtomography. This experimental technique is demonstrated by performing a planar Richtmyer–Meshkov instability (RMI) experiment on an aerogel–water interface characterized by Atwood number A 0 ∼ − 0.8 and Mach number M ∼ 1.5. The qualitative and quantitative features of the experiment are discussed, including the energy deposition into the exploding wires, shockwave generation, compression of the interface, startup phase of the instability, and asymptotic growth consistent with Richtmyer's impulsive theory. Additional effects unique to liquids and solids—such as cavitation bubbles caused by rarefaction flows or initial jetting due to small perturbations—are observed. It is also demonstrated that the technique is not shape dependent by driving a cylindrically convergent RMI experiment.

Journal article

Mundy T, Bland S, Lebedev S, Chittenden J, Marrow K, Suttle L, Halliday J, Rose Cet al., 2023, Novel Experiment for Scaled Power Flow Studies Towards Next-Generation Pulsed Power, ISSN: 2158-4915

In order to develop a better understanding of current losses in the magnetically insulated region of high-power pulsed power machines, it is crucial to be able to conduct experiments at scale in smaller facilities. Here, we present a novel experiment that has been tested on the MAGPIE driver at Imperial College. The targets are inexpensive and easy to customize for experiments ranging from power flow to warm dense matter. Simulations in COMSOL indicated electric fields of up to 600 MV/m and magnetic fields of up to 300 T could be produced on MAGPIE. In initial testing, Electric fields exceeding 100 MV/m and magnetic fields exceeding 50 T were generated, and both magnetically insulated transmission and plasma-shorted transmission were demonstrated.

Conference paper

Merlini S, Hare JD, Burdiak GC, Halliday JWD, Marrow K, Suttle LG, Russell DR, Crilly AJ, Chittenden JP, Lebedev SVet al., 2023, Investigate Electron Density Perturbations in Supersonic Magnetised HED Plasmas Using Imaging Refractometer and Thomson Scattering Diagnostics, ISSN: 0730-9244

Shock structures formed in supersonic plasmas colliding against conducting obstacles can be significantly affected by radiative cooling and magnetic fields, leading to instabilities and turbulence. Under these conditions, experimental measurements of plasma parameters are very difficult to perform using conventional laser-based diagnostics, such as shadowgraphy, schlieren and interferometry.

Conference paper

Hare J, Datta R, Chandler K, Hansen S, Looker Q, Edens A, Chaturvedi N, Chittenden J, Crilly A, Fox W, Jennings C, Ji H, Kuranz C, Lebedev S, Myers C, Uzdensky Det al., 2023, X-ray Observations of Radiatively Cooled Magnetic Reconnection Driven by Pulsed-Power on the Z Machine, ISSN: 0730-9244

Magnetic reconnection is a ubiquitous process throughout the Universe, which changes the topology of magnetic fields and releases magnetic energy impulsively in the form of heat, directed flows and fast particles. In extreme astrophysical environments, radiative cooling further modifies this partition of energy, leading to cooling instabilities which modify the reconnection process. The MARZ (Magnetically Ablated Reconnection on Z) collaboration carried out three shots on the Z Machine as part of the Z Fundamental Science Program to study radiatively cooled magnetic reconnection in the laboratory.

Conference paper

Marrow K, Mundy T, Halliday J, Crilly A, Chittenden J, Mancini R, Merlini S, Rose S, Russell D, Strucka J, Suttle L, Valenzuela-Villaseca V, Bland S, Lebedev Set al., 2023, Radiative Instabilities in the Stagnation Layer of Colliding, X-Ray Driven Plasma Flows, ISSN: 0730-9244

We summarise existing results and future avenues of research from a novel experimental platform [1] fielded on the MAGPIE pulsed-power generator (1.4 MA, 240 ns rise time). This platform uses the x-ray pulse emitted from a wire array z-pinch to drive plasma ablation from a target. The radiatively driven outflow has a uniform (quasi-1D) structure and expands into the ambient magnetic field produced by the z-pinch.

Conference paper

Mughal K, Bland S, Strucka J, Yao Y, Chittenden J, Caballero Bendixsen LS, Suzuki-Vidal F, Skidmore J, Read J, Dobranszki C, Doyle H, Krasik Y, Maler Det al., 2023, High Speed Convergent Shockwaves Driven in Dielectrics Driven by Exploding Wires on the 14MA M3 Pulse-Powered Facility, ISSN: 0730-9244

The implosion of fast, convergent shock waves driven via the electrical explosion of cylindrical wire arrays embedded in insulator offers a highly efficient method of generating extreme pressures. At low currents (30kA) the increased density on axis was directly observed at the ESRF synchroton; at higher currents - up to 2.5MA on the Cepage generator at First Light Fusion - the implosion dynamics imply pressures >Mbar exist in warm dense plasma on axis. How this process scales to currents >5MA is unclear - a limit could exist on the speed at which the shockwaves are initially projected from the wires, set by the rate of energy deposition into the wires.

Conference paper

Datta R, Crilly A, Chaturvedi N, Chandler K, Chowdhry S, Fox W, Jennings C, Ji H, Kuranz C, Lebedev S, Myers C, Uzdensky D, Chittenden J, Hare Jet al., 2023, Simulations of Radiatively Cooled Magnetic Reconnection Driven by Pulsed-Power on the Z Machine, ISSN: 0730-9244

Magnetic reconnection-the abrupt change in magnetic field topology accompanied by the explosive release of heat and kinetic energy-is an important process in astrophysical plasmas. In high-energy-density astrophysical environments, strong radiative cooling can modify the reconnection process, by rapidly removing the magnetic energy dissipated in the current sheet. The MARZ (Magnetically Ablated Reconnection on Z) collaboration investigates radiatively-cooled reconnection in the laboratory on the Z pulsed-power machine, as part of the Z Fundamental Science Program.

Conference paper

Strucka J, Lukic B, Koerner M, Halliday J, Yao Y, Mughal K, Maler D, Efimov S, Skidmore J, Rack A, Krasik Y, Chittenden J, Bland Set al., 2023, Exploding Wire Arrays for Single-Shot Hydrodynamic Instability Experiments, ISSN: 0730-9244

The dynamics of high-energy-density plasmas are dominated by the formation of instabilities. These can be seen on at all scales, from the structure of proto-stellar jets and nebulae, to the inertial confinement fusion experiments where instabilities can mix cold, dense, high Z plasma into fusion fuel significantly reducing yield. Measuring how the hydrodynamic instabilities evolve is crucial to providing quantitative comparison to theory and simulations, yet many experiments are limited to exploring relatively small region of parameter space in Mach and Atwood numbers, or provide only a few measurements per experiment, requiring control of the initial conditions (ICs).

Conference paper

Crilly AJ, Appelbe BD, Mannion OM, Taitano W, Hartouni EP, Moore AS, Gatu-Johnson M, Chittenden JPet al., 2022, Constraints on ion velocity distributions from fusion product spectroscopy, NUCLEAR FUSION, Vol: 62, ISSN: 0029-5515

Journal article

Datta R, Russell DR, Tang I, Clayson T, Suttle LG, Chittenden JP, Lebedev S, Hare JDet al., 2022, The structure of 3-D collisional magnetized bow shocks in pulsed-power-driven plasma flows, Journal of Plasma Physics, Vol: 88, ISSN: 0022-3778

We investigate three-dimensional (3-D) bow shocks in a highly collisional magnetized aluminium plasma, generated during the ablation phase of an exploding wire array on the MAGPIE facility (1.4 MA, 240 ns). Ablation of plasma from the wire array generates radially diverging, supersonic ( MS∼7 ), super-Alfvénic ( MA>1 ) magnetized flows with frozen-in magnetic flux ( RM≫1 ). These flows collide with an inductive probe placed in the flow, which serves both as the obstacle that generates the magnetized bow shock, and as a diagnostic of the advected magnetic field. Laser interferometry along two orthogonal lines of sight is used to measure the line-integrated electron density. A detached bow shock forms ahead of the probe, with a larger opening angle in the plane parallel to the magnetic field than in the plane normal to it. Since the resistive diffusion length of the plasma is comparable to the probe size, the magnetic field decouples from the ion fluid at the shock front and generates a hydrodynamic shock, whose structure is determined by the sonic Mach number, rather than the magnetosonic Mach number of the flow. The 3-D simulations performed using the resistive magnetohydrodynamic (MHD) code Gorgon confirm this picture, but under-predict the anisotropy observed in the shape of the experimental bow shock, suggesting that non-MHD mechanisms may be important for modifying the shock structure.

Journal article

Russell D, Burdiak G, Carroll-Nellenback JJ, Halliday J, Hare J, Merlini S, Suttle L, Valenzuela-Villaseca V, Eardley S, Fullalove J, Rowland G, Smith R, Frank A, Hartigan P, Velikovich AL, Chittenden J, Lebedev Set al., 2022, Perpendicular subcritical shock structure in a collisional plasma experiment, Physical Review Letters, Vol: 129, ISSN: 0031-9007

We present a study of perpendicular subcritical shocks in a collisional laboratory plasma. Shocks areproduced by placing obstacles into the supermagnetosonic outflow from an inverse wire array z pinch. Wedemonstrate the existence of subcritical shocks in this regime and find that secondary shocks form in thedownstream. Detailed measurements of the subcritical shock structure confirm the absence of ahydrodynamic jump. We calculate the classical (Spitzer) resistive diffusion length and show that it isapproximately equal to the shock width. We measure little heating across the shock (< 10% of the ionkinetic energy) which is consistent with an absence of viscous dissipation.

Journal article

Moody JD, Pollock BB, Sio H, Strozzi DJ, Ho DD-M, Walsh CA, Kemp GE, Lahmann B, Kucheyev SO, Kozioziemski B, Carroll EG, Kroll J, Yanagisawa DK, Angus J, Bachmann B, Bhandarkar SD, Bude JD, Divol L, Ferguson B, Fry J, Hagler L, Hartouni E, Herrmann MC, Hsing W, Holunga DM, Izumi N, Javedani J, Johnson A, Khan S, Kalantar D, Kohut T, Logan BG, Masters N, Nikroo A, Orsi N, Piston K, Provencher C, Rowe A, Sater J, Skulina K, Stygar WA, Tang V, Winters SE, Zimmerman G, Adrian P, Chittenden JP, Appelbe B, Boxall A, Crilly A, O'Neill S, Davies J, Peebles J, Fujioka Set al., 2022, Increased ion temperature and neutron yield observed in magnetized indirectly driven D_{2}-filled capsule implosions on the national ignition facility, Physical Review Letters, Vol: 129, ISSN: 0031-9007

The application of an external 26 Tesla axial magnetic field to a D_{2} gas-filled capsule indirectly driven on the National Ignition Facility is observed to increase the ion temperature by 40% and the neutron yield by a factor of 3.2 in a hot spot with areal density and temperature approaching what is required for fusion ignition [1]. The improvements are determined from energy spectral measurements of the 2.45 MeV neutrons from the D(d,n)^{3}He reaction, and the compressed central core B field is estimated to be ∼4.9  kT using the 14.1 MeV secondary neutrons from the D(T,n)^{4}He reactions. The experiments use a 30 kV pulsed-power system to deliver a ∼3  μs current pulse to a solenoidal coil wrapped around a novel high-electrical-resistivity AuTa_{4} hohlraum. Radiation magnetohydrodynamic simulations are consistent with the experiment.

Journal article

Datta R, Russell DR, Tang I, Clayson T, Suttle LG, Chittenden JP, Lebedev S, Hare JDet al., 2022, Time-resolved velocity and ion sound speed measurements from simultaneous bow shock imaging and inductive probe measurements, REVIEW OF SCIENTIFIC INSTRUMENTS, Vol: 93, ISSN: 0034-6748

Journal article

Crilly A, Garin-Fernandez I, Appelbe B, Chittenden Jet al., 2022, Efficacy of ICF experiments in light ion fusion cross section measurement at nucleosynthesis relevant energies, Frontiers in Physics, Vol: 10, Pages: 1-11, ISSN: 2296-424X

Inertial confinement fusion (ICF) experiments create a unique laboratory environment in which thermonuclear fusion reactionsoccur within a plasma, with conditions comparable to stellar cores and the early universe. In contrast, accelerator-basedmeasurements must compete with bound electron screening effects and beam stopping when measuring fusion cross sections atnucleosynthesis-relevant energies. Therefore, ICF experiments are a natural place to study nuclear reactions relevant to nuclearastrophysics. However, analysis of ICF-based measurements must address its own set of complicating factors. These include: theinherent range of reaction energies, spatial and temporal thermal temperature variation, and kinetic effects such as speciesseparation. In this work we examine these phenomena and develop an analysis to quantify and, when possible, compensate fortheir effects on our inference. Error propagation in the analyses are studied using synthetic data combined with Markov ChainMonte Carlo (MCMC) machine learning. The novel inference techniques will aid in the extraction of valuable and accurate data fromICF-based nuclear astrophysics experiments.

Journal article

Eggington J, Coxon J, Shore R, Desai R, Mejnertsen L, Chittenden J, Eastwood Jet al., 2022, Response timescales of the magnetotail current sheet during a geomagnetic storm: global MHD simulations, Frontiers in Astronomy and Space Sciences, Vol: 9, Pages: 1-17, ISSN: 2296-987X

The response of the Earth’s magnetotail current sheet to the external solar wind driver is highly time-dependent and asymmetric. For example, the current sheet twists in response to variations in the By component of the interplanetary magnetic field (IMF), and is hinged by the dipole tilt. Understanding the timescales over which these asymmetries manifest is of particular importance during geomagnetic storms when the dynamics of the tail control substorm activity. To investigate this, we use the Gorgon MHD model to simulate a geomagnetic storm which commenced on 3 May 2014, and was host to multiple By and Bz reversals and a prolonged period of southward IMF driving. We find that the twisting of the current sheet is well-correlated to IMF By throughout the event, with the angle of rotation increasing linearly with downtail distance and being morepronounced when the tail contains less open flux. During periods of southward IMF the twisting of the central current sheet responds most strongly at a timelag of ∼ 100 min for distances beyond 20 RE, consistent with the 1-2 hr convection timescale identified in the open flux content. Under predominantly northward IMF the response of the twisting is bimodal, with the strongest correlations between 15-40 RE downtail being at a shorter timescale of ∼ 30 min consistent with that estimated for induced By due to wave propagation, compared to a longer timescale of ∼ 3 hr further downtail again attributed to convection. This indicates that asymmetries in the magnetotail communicated by IMF By are influenced mostly by global convection during strong solar wind driving, but that more prompt induced By effects can dominate in the near-Earth tail and during periods of weaker driving. These results provide new insight into the characteristic timescales of solar wind-magnetosphere-ionosphere coupling.

Journal article

Abu-Shawareb H, Acree R, Adams P, Adams J, Addis B, Aden R, Adrian P, Afeyan BB, Aggleton M, Aghaian L, Aguirre A, Aikens D, Akre J, Albert F, Albrecht M, Albright BJ, Albritton J, Alcala J, Alday C, Alessi DA, Alexander N, Alfonso J, Alfonso N, Alger E, Ali SJ, Ali ZA, Alley WE, Amala P, Amendt PA, Amick P, Ammula S, Amorin C, Ampleford DJ, Anderson RW, Anklam T, Antipa N, Appelbe B, Aracne-Ruddle C, Araya E, Arend M, Arnold P, Arnold T, Asay J, Atherton LJ, Atkinson D, Atkinson R, Auerbach JM, Austin B, Auyang L, Awwal AS, Ayers J, Ayers S, Ayers T, Azevedo S, Bachmann B, Back CA, Bae J, Bailey DS, Bailey J, Baisden T, Baker KL, Baldis H, Barber D, Barberis M, Barker D, Barnes A, Barnes CW, Barrios MA, Barty C, Bass I, Batha SH, Baxamusa SH, Bazan G, Beagle JK, Beale R, Beck BR, Beck JB, Bedzyk M, Beeler RG, Beeler RG, Behrendt W, Belk L, Bell P, Belyaev M, Benage JF, Bennett G, Benedetti LR, Benedict LX, Berger R, Bernat T, Bernstein LA, Berry B, Bertolini L, Besenbruch G, Betcher J, Bettenhausen R, Betti R, Bezzerides B, Bhandarkar SD, Bickel R, Biener J, Biesiada T, Bigelow K, Bigelow-Granillo J, Bigman V, Bionta RM, Birge NW, Bitter M, Black AC, Bleile R, Bleuel DL, Bliss E, Bliss E, Blue B, Boehly T, Boehm K, Boley CD, Bonanno R, Bond EJ, Bond T, Bonino MJ, Borden M, Bourgade J-L, Bousquet J, Bowers J, Bowers M, Boyd R, Bozek A, Bradley DK, Bradley KS, Bradley PA, Bradley L, Brannon L, Brantley PS, Braun D, Braun T, Brienza-Larsen K, Briggs TM, Britten J, Brooks ED, Browning D, Bruhn MW, Brunner TA, Bruns H, Brunton G, Bryant B, Buczek T, Bude J, Buitano L, Burkhart S, Burmark J, Burnham A, Burr R, Busby LE, Butlin B, Cabeltis R, Cable M, Cabot WH, Cagadas B, Caggiano J, Cahayag R, Caldwell SE, Calkins S, Callahan DA, Calleja-Aguirre J, Camara L, Camp D, Campbell EM, Campbell JH, Carey B, Carey R, Carlisle K, Carlson L, Carman L, Carmichael J, Carpenter A, Carr C, Carrera JA, Casavant D, Casey A, Casey DT, Castillo A, Castillo E, Castor JI, Castro C, Caugheyet al., 2022, Lawson criterion for ignition exceeded in an inertial fusion experiment, Physical Review Letters, Vol: 129, ISSN: 0031-9007

For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37 MJ of fusion for 1.92 MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion.

Journal article

Moody JD, Pollock BB, Sio H, Strozzi DJ, Ho DD-M, Walsh C, Kemp GE, Kucheyev SO, Kozioziemski B, Carroll EG, Kroll J, Yanagisawa DK, Angus J, Bhandarkar SD, Bude JD, Divol L, Ferguson B, Fry J, Hagler L, Hartouni E, Herrmann MC, Hsing W, Holunga DM, Javedani J, Johnson A, Kalantar D, Kohut T, Logan BG, Masters N, Nikroo A, Orsi N, Piston K, Provencher C, Rowe A, Sater J, Skulina K, Stygar WA, Tang V, Winters SE, Chittenden JP, Appelbe B, Boxall A, Crilly A, O'Neill S, Davies J, Peebles J, Fujioka Set al., 2022, The Magnetized Indirect Drive Project on the National Ignition Facility, JOURNAL OF FUSION ENERGY, Vol: 41, ISSN: 0164-0313

Journal article

Crilly AJ, Appelbe BD, Mannion OM, Forrest CJ, Knauer JP, Schlossberg DJ, Hartouni EP, Moore AS, Chittenden JPet al., 2022, Neutron backscatter edges as a diagnostic of burn propagation, PHYSICS OF PLASMAS, Vol: 29, ISSN: 1070-664X

Journal article

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