Extreme Energy Densities Research Articles

Optimization Methodology of Polar Direct-Drive Illumination for the National Ignition Facility.

Improved laser illumination uniformity drives shocks and implosions to create more extreme high energy density environments. Predominantly, the geometry of experiments that can be performed is dictated by the layout of beams at laser facilities, limiting interfacility and multiscale investigations. This Letter presents the first automated, algorithmic approach for generating illumination configurations for high energy density experiments. The method is demonstrated in comparison to a polar direct-drive solid target experiment at the National Ignition Facility. The new illumination configuration is simulated to create greater than ×3 higher peak pressure and almost ×2 higher density by maintaining better shock uniformity. The optimization process is performed with reduced computational expense and isotropic plasma profiles while accounting for the impact of cross-beam energy transfer.

Study of charged particle multiplicity with centrality in Au+Au collisions at SNN = 200 GeV

We have carried out methods of study to find the correlation between charged particle multiplicity and collision centrality of Au+Au collisions at SNN = 200 GeV. We have studied the open data from the ALICE experiment and arrived at the conclusion that central collisions produced a greater number of charged particles than peripheral collisions. This is done by reconstructing the three silicon layers inside the inner tracking system of the detector and studying the change in two spatial variables between layers: pseudorapidity with range || < 1 and azimuthal angle with acceptance , which can then be input into the sideband method to find the final multiplicity of each event. The study provides an insight into the transient nature of the Quark Gluon Plasma (QGP) produced in collisions by exploring how collision aftermaths vary with different conditions of the partons, which hopefully adds to the understanding of matter under the strong force at extreme energy density.

Ultra-intense femtosecond laser interactions with aligned nanostructures

The interaction of ultrafast laser pulses of relativistic intensity with high aspect ratio nanostructures can efficiently and volumetrically heat matter to an ultra-high-energy-density regime encountered in the center of stars and within the core of fusion capsules compressed by the world’s largest lasers. It also generates gigantic quasi-static electromagnetic fields that accelerate particles to very high energy. Here, we present an overview of the physics and applications of these dense relativistic plasmas that can be created with pulses of relatively modest energy from lasers that can operate at a high repetition rate. Recent nanowire array experiments produced near-solid density plasmas with an extreme degree of ionization (e.g., Au+72), converted ultrafast pulses of laser light into intense x-ray flashes with record efficiency, and accelerated ions to MeV energies, efficiently driving micro-scale fusion reactions that generate flashes of quasi-monoenergetic neutrons. These plasmas also serve as a platform for advancing the understanding of atomic processes in extreme environments and open a new pathway to laser-driven fusion energy. The irradiation of nanostructures at intensities of >1×1022Wcm−2 is predicted to lead to an extreme ultra-high energy density plasma regime characterized by terabar pressures that is virtually unexplored.

Enriched performance of practical device assisted asymmetric supercapacitor: NiO/Co3O4 intercalated with rGO nanocomposite electrodes

In this present report, we developed high performance supercapacitor electrode material of NiO/Co3O4/rGO ternary nanocomposites synthesized by a hydrothermal method with a different nickel and cobalt molar proportions. The phase formation, surface morphology and elemental information studies of binary NiO/Co3O4 and ternary NiO/Co3O4/rGO nanocomposites were investigated. The electrochemical investigations of the binary and ternary nanocomposites electrodes have been examined. Compare with various molar proportions, the ternary NiO/Co3O4(1,3)/rGO nanocomposites shows an extraordinary capacitance value of 980 Fg−1 at 1 Ag−1 as well as robust cycle life (cyclic retention of 92 % over the 5000 cycles at 10 Ag−1). In 0–1.4 V, an asymmetric supercapacitor attained a specific capacitance of 87.2 Fg−1 and large power density (1396.3 W/kg) with extreme energy density (23.7 Wh/kg). Moreover, assembled device reveals a great rate capability (89 % over the 5000 cycles in the electrolyte of PVA-KOH). The ternary electrode has high capacitance, capacitance retention and large energy density due to NiO and Co3O4 nanoparticles being intercalated with the high surface of rGO, as well as the synergetic effect of NiO/Co3O4 and rGO.

Highly concentrated solvation structure for reversible high-voltage lithium-ion battery at low temperature

The commercial electrolytes exhibit subpar performance under low temperature and high voltage, severely limiting the application of lithium-ion batteries (LIBs) for extreme temperature and high energy density. As a groundbreaking advancement, the regulation of Li+ solvation structure was adopted and highly concentrated in this work, obtaining an improved electrolyte with excellent low-temperature and high-voltage performance. The electrolyte exhibited outstanding oxidation potential of 5.25 V and high ionic conductivity, maintaining transparency liquid even at −60 °C. Notably, the NCM811||Li cell exhibited high initial capacity (71.41 % of that at room temperature) at −40 °C 0.2C, with almost no capacity decay after 50 cycles. Impressively, the as-assembled NCM811||Graphite pouch battery (2.5 Ah) showed an initial capacity of 2.07 Ah at 0.1C under −30 °C, with an excellent capacity retention ratio of 84.53 % after 50 cycles. This work points out a promising approach for the practical application of high-voltage LIBs at low temperature.

Interfacial catalytic behaviors of atomic thin SnS2 layer in Li-O2 batteries

Li-O2 battery has been considered to be one of the promising energy storage devices due to its extreme large theoretical energy density. However, the severe electrochemical polarization and irreversible decomposition of the discharge product Li2O2 dramatically prevent its widely applications. In this article, a low-cost 2D atomic thin few-layer SnS2 catalysts synthesized via a modified hydrothermal method are employed as the catalyst cathode for the Li-O2 batteries. The catalytic properties of atomic thin SnS2 layer in the Li-O2 batteries are discussed through systematic experiments and theoretical calculations. It is found that the generation of Sn4+/Sn2+ redox couple in the SnS2 catalyst may act as the active catalytic sites on promoting formation/decomposition for the intermediate LiO2 and discharge product Li2O2 throughout the cycling processes. Moreover, it is calculated that the (001) plane for the SnS2 cathode can reduce the adsorption energy barrier and the catalytic reaction energy gaps for the interface electrochemical reaction in the Li-O2 batteries. Our work may not only reveal the catalystic mechanism of SnS2 for promoting ORR/OER processes in Li-O2 batteries, but also pave a way to explore new SnS2-based electrocatalysts for energy conversion and storage in the future.

5500 ГэВ/нуклон энергитэй Pb+Pb үйлчлэлээр үүссэн саармаг бөөмсийг загварчлах

The aim of high energy heavy ion physics is to study strong interacting matter at extreme energy densities. QCD predicts that, an sufficiently high energy density, there will be a phase transition from hadron matter to a plasma of deconfined quarks and gluons called a Quark-Glu Plasma(QGP). Such a phase transition would have taken place in the ea Universe some 10-5 seconds after the Big Bang and may still play a role in the core of collapsing neutron stars.

Burst timescales and luminosities as links between young pulsars and fast radio bursts

Fast radio bursts (FRBs) are extragalactic radio flashes of unknown physical origin. Their high luminosities and short durations require extreme energy densities, such as those found in the vicinity of neutron stars and black holes. Studying the burst intensities and polarimetric properties on a wide range of timescales, from milliseconds down to nanoseconds, is key to understanding the emission mechanism. However, high-time-resolution studies of FRBs are limited by their unpredictable activity levels, available instrumentation and temporal broadening in the intervening ionized medium. Here we show that the repeating FRB 20200120E can produce isolated shots of emission as short as about 60 nanoseconds in duration, with brightness temperatures as high as 3 × 1041 K (excluding relativistic effects), comparable with ‘nano-shots’ from the Crab pulsar. Comparing both the range of timescales and luminosities, we find that FRB 20200120E observationally bridges the gap between known Galactic young pulsars and magnetars and the much more distant extragalactic FRBs. This suggests a common magnetically powered emission mechanism spanning many orders of magnitude in timescale and luminosity. In this Article, we probe a relatively unexplored region of the short-duration transient phase space; we highlight that there probably exists a population of ultrafast radio transients at nanosecond to microsecond timescales, which current FRB searches are insensitive to. The range of timescales and luminosities measured from the nearby fast radio burst FRB 20200120E observationally connects these extreme extragalactic transients with studies of Galactic neutron stars.

Quantum Electrodynamics vacuum polarization solver

The self-consistent modeling of vacuum polarization due to virtual electron-positron fluctuations is of relevance for many near term experiments associated with high intensity radiation sources and represents a milestone in describing scenarios of extreme energy density. We present a generalized finite-difference time-domain solver that can incorporate the modifications to Maxwell’s equations due to vacuum polarization. Our multidimensional solver reproduced in one-dimensional configurations the results for which an analytic treatment is possible, yielding vacuum harmonic generation and birefringence. The solver has also been tested for two-dimensional scenarios where finite laser beam spot sizes must be taken into account. We employ this solver to explore different types of laser configurations that can be relevant for future planned experiments aiming to detect quantum vacuum dynamics at ultra-high electromagnetic field intensities.

All femtosecond optical pump and x-ray probe: holey-axicon for free electron lasers

We put forward a co-axial pump (optical)-probe (x-rays) experimental concept and show performance of the optical component. A Bessel beam generator with a central 100 µm diameter hole (on the optical axis) was fabricated using femtosecond (fs) laser structuring inside a silica plate. This flat-axicon optical element produces a needle-like axial intensity distribution which can be used for the optical pump pulse. The fs-x-ray free electron laser (X-FEL) beam of sub-1 µm diameter can be introduced through the central hole along the optical axis onto a target as a probe. Different realisations of optical pump are discussed. Such optical elements facilitate alignment of ultra-short fs-pulses in space and time and can be used in light–matter interaction experiments at extreme energy densities on the surface and in the volume of targets. Full advantage of ultra-short 10 fs-X-FEL probe pulses with fs-pump (optical) opens an unexplored temporal dimension of phase transitions and the fastest laser-induced rates of material heating and quenching. A wider field of applications of fs-laser-enabled structuring of materials and design of specific optical elements for astrophotonics is presented.

The need for speed

This paper reviews the challenges posed by the physics of the interaction of high-peak power femtosecond lasers with ultrathin foil targets. Initially designed to produce warm solid-density plasmas through the isochoric heating of solid matter, the interaction of an ultrashort pulse with ultrathin foils is becoming more and more complex as the laser intensity is increased. The dream of achieving very hot solid density matter with extreme specific energy density faces several bottlenecks discussed here as related to the laser technology, to the complexity of the physical processes, and to the limits of our current time-resolved instrumentations.

Performance of the ALICE electromagnetic calorimeters in LHC Runs 1 and 2 and upgrade projects

ALICE (A Large Ion Collider Experiment) at the LHC is designed for studies of nuclear matter at extreme temperatures and energy densities, the so-called Quark-Gluon Plasma (QGP). Two detectors for measurements of electromagnetic signals, high-granularity photon spectrometer PHOS and large acceptance electromagnetic calorimeter EMCal/DCal, are incorporated into the ALICE detector. In order to enhance the data sample of the high-energy part of the spectra, dedicated triggers on high energetic photons or jets are used. High precision measurements of neutral mesons require fine energy and timing calibrations. Photon signal purity is improved using dedicated photon PID criteria based on cluster shape and anti-track matching with the ALICE central tracking system, as well as a special detector located in front of PHOS called CPV. PHOS and EMCal participated in LHC Run 1 (2009-2013) and Run 2 (2015-2018) during data taking periods of pp, p-Pb and Pb-Pb collisions. We give an overview of their performance in Runs 1 and 2 in low and high multiplicity environments as well as the upgrade plans for future LHC runs.

Correlation of Heavy and Light Flavors in Simulations

The ALICE experiment at the Large Hadron Collider (LHC) ring is designed to study the strongly interacting matter at extreme energy densities created in high-energy heavy-ion collisions. In this paper we investigate correlations of heavy and light flavors in simulations at LHC energies at mid-rapidity, with the primary purpose of proposing experimental applications of these methods. Our studies have shown that investigating the correlation images can aid the experimental separation of heavy quarks and help understanding the physics that create them. The shape of the correlation peaks can be used to separate the electrons stemming from b quarks. This could be a method of identification that, combined with identification in silicon vertex detectors, may provide much better sample purity for examining the secondary vertex shift. Based on a correlation picture it is also possible to distinguish between prompt and late contributions to D meson yields.

Investigation of Lithium-Ion Battery Interface Degradation Mechanism through EIS Analysis Under Various Cycling Conditions

Lithium-ion batteries have attracted enormous attention in the past decade both in the academia and in the industry due to their extreme high energy and power density compared with the conventional battery systems. Stepping into 2019, the lithium-ion battery industry unprecedentedly focuses on the fast charging and diagnosis solutions, especially for the dynamic battery systems. However, the complicated environmental conditions, such as vibration, extreme temperature change, overcharging or overdischraging, fast charging, various testing techniques, combined with insufficient understanding of the State of Health (SOH) of the commercial batteries lead to thermal runaway, aging and explosion issues to the batteries. Stemmed from that fact, EIS (Electrochemical Impedance Spectroscopy) technique has been proposed to accurately determine the SOH of the commercial batteries. EIS has been proved to be an effective approach to investigate the electrochemical, structual and dynamical properties of the electrochemical systems, especially the interfaces. The study focuses on the effects of one of the most concerning technique "fast charging" and one testing technique, GITT (Galvanostatic Intermittent Titration Technique). Under pre-design conditions, EIS with pre-built equivalent circuit is then implemented at specific conditions to further gather the electrochemical and structural properties of the interfaces inside the battery at proper voltages. Finally, the electrochemical and structual degradation mechanism especially of the interfaces under various conditions is achieved, which inspires further investigation on the comprehensive analysis and determination of the SOH of the lithium-ion batteries. The proposed approach has shown better accuracy and more in-depth analysis compared with the existing techniques.

Marx Generators Based on MOS-Gated Switches With Magnetic Assist for Accelerator Applications

In the field of pulsed power, gas switches have been widely used due to their high operating voltages and currents. One example of these gas switches is the thyratron, which is in use for some particle accelerators even today. At the Extreme Energy-Density Research Institute, the Nagaoka University of Technology, Nagaoka, Japan, such devices are in use. In recent times, semiconductor switches have been considered as possible replacements due to their ease of maintenance and control. In general, it is difficult to achieve the same ratings for maximum switching current and voltage of a gas switch with a single semiconductor device, so connecting many in series, parallel, or a different scheme is often applied. We propose a study to evaluate a Marx topology using MOS-gated thyristors capable of high current output. The attractive factors of these semiconductors are the low gate current required for turning ON, a low resistance during the ON-state, a four-stage prototype was built, and it achieved a peak output of 1 kV and 1 kA with a $2~\mu \text{s}$ pulsewidth. To improve the output voltage and current, a ferrite core was implemented as a magnetic switch on every stage; this method has been used before to improve the efficiency of thyristors, however, not combined with circuit topologies like a Marx generator. Adding these magnetic switches increased the efficiency to 89% (from 70%) and allowed an output of 2.2 kV and 2.2 kA without changing the shape of the pulse or the rise time.

Quarkonium production in Pb-Pb collisions at √SNN = 5.02 TeV with ALICE

Ultra-relativistic heavy-ion collisions at the Large Hadron Collider provide a unique opportunity to study the properties of matter at extreme energy densities where a phase transition from the hadronic matter to a deconfined medium of quarks and gluons, the Quark-Gluon Plasma (QGP) is predicted. Among the prominent probes of the QGP, heavy quarks play a crucial role since they are created during the initial stages of the collision, before the QGP formation, and their number is conserved throughout the partonic and hadronic phases of the collision. The azimuthal anisotropy of charmonium production, quantified using the second harmonic Fourier coefficient (referred to as elliptic flow), provides important information on the magnitude and dynamics of charmonium production. Measurements of the quarkonium nuclear modification factor at forward rapidity and J/ψ elliptic flow in Pb-Pb collisions as a function of centrality, transverse momentum and rapidity will be presented and compared to different collision energy results and available theoretical calculations.

Search for a Λnn bound state in Pb-Pb collisions with ALICE at the LHC

The extreme energy densities reached at the LHC lead to the production of a significant amount of baryons and strangeness. Such a regime allows for an increased production of potentially existing exotic QCD bound states containing nuclei and strange hadrons. An interesting measurement for the phenomenology of the nuclear interaction is the presence of a neutral bound state constituted by one Λ and two neutrons. The excellent particle identification, tracking and vertexing performance of the ALICE experiment allow for the search of this exotic bound state in the decay channel Λnn →3H+π- in Pb-Pb collisions. In order to improve detection of this state despite the presence of a huge combinatorial background, the extraction of the signal is performed by means of a multivariate approach with the TMVA (Toolkit for Multivariate Data Analysis with ROOT). So far the indication for the existence of the Λnn state was reported only by the HypHI Collaboration, so the observation by ALICE would crucially contribute to the study of such an exotic state.

Global Λ hyperon polarization in nuclear collisions

The extreme energy densities generated by ultra-relativistic collisions between heavy atomic nuclei produce a state of matter that behaves surprisingly like a fluid, with exceptionally high temperature and low viscosity. Non-central collisions have angular momenta of the order of 1,000ћ, and the resulting fluid may have a strong vortical structure that must be understood to describe the fluid properly. The vortical structure is also of particular interest because the restoration of fundamental symmetries of quantum chromodynamics is expected to produce novel physical effects in the presence of strong vorticity. However, no experimental indications of fluid vorticity in heavy ion collisions have yet been found. Since vorticity represents a local rotational structure of the fluid, spin-orbit coupling can lead to preferential orientation of particle spins along the direction of rotation. Here we present measurements of an alignment between the global angular momentum of a non-central collision and the spin of emitted particles (in this case the collision occurs between gold nuclei and produces Λ baryons), revealing that the fluid produced in heavy ion collisions is the most vortical system so far observed. (At high energies, this fluid is a quark-gluon plasma.) We find that Λ and hyperons show a positive polarization of the order of a few per cent, consistent with some hydrodynamic predictions. (A hyperon is a particle composed of three quarks, at least one of which is a strange quark; the remainder are up and down quarks, found in protons and neutrons.) A previous measurement that reported a null result, that is, zero polarization, at higher collision energies is seen to be consistent with the trend of our observations, though with larger statistical uncertainties. These data provide experimental access to the vortical structure of the nearly ideal liquid created in a heavy ion collision and should prove valuable in the development of hydrodynamic models that quantitatively connect observations to the theory of the strong force.

Implications of quantum ambiguities in k=1 loop quantum cosmology: Distinct quantum turnarounds and the super-Planckian regime

The spatially closed Friedmann-Lema\^{i}tre-Robertson-Walker model in loop quantum cosmology admits two inequivalent consistent quantizations: one based on expressing the field strength in terms of the holonomies over closed loops, and, another using a connection operator and open holonomies. Using the effective dynamics, we investigate the phenomenological differences between the two quantizations for the single fluid and the two fluid scenarios with various equations of state, including the phantom matter. We show that a striking difference between the two quantizations is the existence of two distinct quantum turnarounds, either bounces or recollapses, in the connection quantization, in contrast to a single distinct quantum bounce or a recollapse in the holonomy quantization. These results generalize an earlier result on the existence of two distinct quantum bounces for stiff matter by Corichi and Karami. However, we find that in certain situations two distinct quantum turnarounds can become virtually indistinguishable. And depending on the initial conditions, a pure quantum cyclic universe can also exist undergoing a quantum bounce and a quantum recollapse. We show that for various equations of states, connection based quantization leads to super-Planckian values of the energy density and the expansion scalar at quantum turnarounds. Interestingly, we find that very extreme energy densities can also occur for the holonomy quantization, breaching the maximum allowed density in the spatially flat loop quantized model. However, the expansion scalar in all these cases is bounded by a universal value.

ϒ production measurements in pp, p–Pb and Pb–Pb collisions with ALICE

The ϒ production measurement provide an important tool to study the color dissociation properties of matter at extreme energy densities, which is measured using the nuclear modification factor in heavy-ion collisions. In the present paper, the measurement of the nuclear modification factor of ϒ is discussed using the data collected in pp, p-Pb and Pb-Pb collisions with ALICE at LHC energies.