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Georg Korn

Publications and source records attributed to Georg Korn.

At least 19 recordsLinked to original sources
arXiv2025

Reply to "Comments to Marvel Fusions Mixed Fuels Reactor Concept"

In "arXiv:2312.13429" Lackner et al. use standard methods to decide if it is possible to ignite mixed fuels. They correctly identify that the increased radiation losses make ignition significantly more challenging than for pure DT fuels, since this leads to higher ignition temperatures. Further, they conclude that at those temperatures the reduced electronic $\alpha$-stopping makes ignition impossible. We show that this conclusion is not correct. The model used for $\alpha$-stopping by Lackner et al. is only approximately correct for low temperatures and hydrogen isotopes. By extending the $\alpha$-stopping model to include ionic $\alpha$-stopping we show in \cite{ruhlkornarXiv5} that the contribution of ionic $\alpha$-particle stopping cannot be neglected. The ionic $\alpha$-stopping together with the neutron stopping, which is also neglected by Lackner et al., lead to elevated ion temperatures implying $kT_i > kT_e$. Those three effects combined lead us to the conclusion, that ignition of mixed fuels is indeed possible with far reaching implications, contrary to the analysis by Lackner.

physics.plasm-ph↗
arXiv2024

Properties of non-cryogenic DTs and their relevance for fusion

In inertial confinement fusion, pure deuterium-tritium (DT) is usually used as a fusion fuel. In their paper \cite{gus2011effect}, Guskov et al. instead propose using low-Z compounds that contain DT and are non-cryogenic at room temperature. They suggest that these fuels (here called non-cryogenic DTs) can be ignited for $\rho_{DT} R \geq 0.35 \, gcm^{-2}$ and $kT_{e} \geq 14 \, keV$, i.e., parameters which are more stringent but still in the same order of magnitude as those for DT. In deriving these results the authors in \cite{gus2011effect} assume that ionic and electronic temperatures are equal and consider only electronic stopping power. Here, we show that at temperatures greater than 10 keV, ionic stopping power is not negligible compared to the electronic one. We demonstrate that this necessarily leads to higher ionic than electronic temperatures. Both factors facilitate ignition compared to the model used in \cite{gus2011effect} showing that non-cryogenic DT compounds are more versatile than previously known. In addition, we find that heavy beryllium borohydride ignites more easily than heavy beryllium hydride, the best-performing fuel found by Guskov et al. Our results are based on an analytical model that incorporates a detailed stopping power analysis, as well as on numerical simulations using an improved version of the community hydro code MULTI-IFE. Alleviating the constraints and costs of cryogenic technology and the fact that non-cryogenic DT fuels are solids at room temperature open up new design options for fusion targets with $Q>100$ and thus contribute to the larger goal of making inertial fusion energy an economically viable source of clean energy. In addition, the discussion presented here generalizes the analysis of fuels for energy production.

physics.plasm-ph↗
arXiv2023

Uniform volume heating of mixed fuels within the ICF paradigm

The paper investigates the feasibility of achieving uniform high-power volume heating for a fusion reactor concept employing a mixed fuel composition involving $\text{pBDT}$. The realm of mixed fuel fusion concepts remains relatively unexplored. The pursuit of uniform high-power volume heating presents a technological challenge, yet it bears ramifications for fusion reactor designs. In this study, we introduce the proposition of employing embedded nano-structures that represent structured foams. These structured foams interact with short-pulse lasers, thereby achieving ultra-high power volume heating both within the fuel and the adjacent hohlraums. Notably, structured foams exhibit superior efficiency compared to unstructured foams, plasma or surfaces when it comes to absorbing high-power, short-pulse lasers. The suggested incorporation of these embedded structured foams interacting with an array of ultra-short laser pulses offers a high laser absorption power density, along with meticulous control over energy and power distribution within the fuel, both in spatial and temporal dimensions. This holds the potential for the realization of fusion reactors characterized by straight-forward designs and low complexity, where $Q_F \approx Q_T > 1$ is expected for the fuel and target gains. Depending on the fuel composition they can be strong neutron sources.

physics.plasm-ph↗
arXiv2023

Numerical validation of a volume heated mixed fuel concept

While the underlying physics of the ICF approach to nuclear fusion is well understood and a technological implementation of the indirect drive variant of the ICF paradigm has recently been given at NIF commercially viable ICF concepts for energy production and beyond are still under investigation. In the present paper we propose core elements of a novel fast direct drive mixed fuel ICF concept that might be commercially viable. It makes use of ultra-short, ultra-intense laser pulses interacting with nano-structured accelerators embedded into the mixed fuel context. The embedded accelerator technology promises to be highly efficient and capable of fast fuel heating without fuel pre-compression but is not the focus of the paper. It is the predominant purpose of the mixed fuel concept to avoid cryogenic fuels since specific chemical compounds exist that are capable of chemically binding $\text{DT}$. To which extent mixed fuel concepts can work is investigated in the paper. Under the assumption that the proposed direct drive fast heating concept is capable of rapidly heating the fuel uniformly to sufficiently high temperatures it is found with the help of MULTI, an ICF community code, that a $\text{pBDT}$ mixed fuel design can reach a target yield $Q_T >1$ with $\text{MJ}$ level external isochoric heating. The simulations are used to validate a theoretical scaling model of the mixed fuel reactive hydro flows. The paper does not present a reactor point design.

physics.plasm-ph↗
arXiv2022

High current ionic flows via ultra-fast lasers for fusion applications

In the present paper we introduce a new accelerator concept for ions. The accelerator is nano-structured and can consist of a range of materials. It is capable of generating large ionic currents at moderate ion energies. The nano-structures can be tailored towards the accelerator thus being capable of driving ion beams with very high efficiency. The accelerator is powered by laser arrays consisting of many repetitive and efficient lasers in the $100 \, \text{J}$ range with ultra-short intense laser pulses. Combining nano-structures and the proposed ultra-short pulse lasers can lead to new levels of spatio-temporal control and energy efficiency for fusion applications.

physics.acc-ph↗
arXiv2022

A laser-driven mixed fuel nuclear fusion micro-reactor concept

We propose a laser-driven near-solid density nano-structured micro-reactor concept operating with mixed nuclear fusion fuels. The micro-reactor is capable of making use of a range of neutronic and aneutronic fuels. Its core parts consists of an embedded nanoscopic nuclear fuel based laser-driven nano-accelerator that is capable of producing non-thermal fuel distributions almost instantly.

physics.plasm-ph↗
arXiv2021

Relativistic-flying laser focus by a laser-produced parabolic plasma mirror

The question of electromagnetic field intensification towards the values typical for strong field Quantum Electrodynamics is of fundamental importance. One of the most promising intensification schemes is based on the relativistic-flying mirror concept, which shows that the electromagnetic radiation reflected by the mirror will be frequency up-shifted by a factor of 4 gamma^2 (gamma: the Lorentz factor of the mirror). In laser-plasma interactions, such a mirror travels with relativistic velocities and typically has a parabolic form, which is advantageous for light intensification. Thus, a relativistic-flying parabolic mirror reflects the counter-propagating radiation in a form of focused and flying electromagnetic wave with a high frequency. The relativistic-flying motion of the laser focus makes the electric and magnetic field distributions of the focus complicated, and the mathematical expressions describing the field distributions of the focus is important. We present analytical expressions describing the field distribution formed by an ideal flying mirror having a perfect reflectance over the entire surface and wavelength range. The peak field strength of an incident laser pulse with a center wavelength of lambda_0 and an effective beam radius of w_e is enhanced by a factor proportional to gamma^3 (w_e/lambda_0) in the relativistic limit. Electron-positron pair production is investigated in the context of invariant fields based on the enhanced electromagnetic field. The pair production rate under the relativistic-flying laser focus is modified by the Lorentz gamma-factor and the beam radius-wavelength ratio (w_e/lambda_0). We show that the electron-positron pairs can be created by colliding two counter-propagating relativistic-flying laser focuses in vacuum, each of which is formed when a 180 TW laser pulse is reflected by a relativistic-flying parabolic mirror with a gamma = 12.2.

physics.plasm-ph↗
arXiv2021

Gamma-Ray Flash Generation in Irradiating Thin Foil Target by Single Cycle Tightly Focused Extreme Power Laser Pulse

We present a regime where an ultra-intense laser pulse interacting with a foil target results in high $γ$-photon conversion efficiency, obtained via three-dimensional quantum-electrodynamics particle-in-cell simulations. A single-cycle laser pulse is used under the tight-focusing condition for obtaining the $\mathrmλ^3$ regime. The simulations employ a radially polarized laser as it results in higher $γ$-photon conversion efficiency compared to both azimuthal and linear polarizations. A significant fraction of the laser energy is transferred to positrons, while a part of the electromagnetic wave escapes the target as attosecond single-cycle pulses.

physics.plasm-ph↗
arXiv2019

Properties of Finite Amplitude Electromagnetic Waves propagating in the Quantum Vacuum

We study two counter-propagating electromagnetic waves in the vacuum within the framework of the Heisenberg-Euler formalism in quantum electrodynamics. We show that the non-linear field equations decouple for ordinary wave case and can be solved exactly. We solve the non-linear field equations assuming the solution in a form of a Riemann wave. We discuss the properties of the nonlinear electromagnetic wave propagating in the quantum vacuum, such as the wave steepening, subsequent generation of high order harmonics and electromagnetic shock wave formation with electron-positron pair generation at the shock wave front.

physics.plasm-ph↗
arXiv2019

Wakefield Excited by Ultrashort Laser Pulses in Near-Critical Density Plasmas

Laser wakefield acceleration (LWFA) using high repetition rate mJ-class laser systems brings unique opportunities for a broad range of applications. In order to meet the conditions required for the electron acceleration with lasers operating at lower energies, one has to use high density plasmas and ultrashort pulses. In the case of a few-cycle pulse, the dispersion and the carrier envelope phase effects can no longer be neglected. In this work, the properties of the wake waves generated by ultrashort pulse lasers in near-critical density plasmas are investigated. The results obtained may lead to enhancement of the quality of LWFA electron beams using kHz laser systems.

physics.plasm-ph↗
arXiv2019

Imprint of the stochastic nature of photon emission by electrons on the proton energy spectra in the laser-plasma interaction

The impact of stochasticity effects (SEs) in photon emissions on the proton energy spectra during laser-plasma interaction is theoretically investigated in the quantum radiation-dominated regime, which may facilitate SEs experimental observation. We calculate the photon emissions quantum mechanically and the plasma dynamics semiclassically via two-dimensional particle-in-cell simulations. An ultrarelativistic plasma generated and driven by an ultraintense laser pulse head-on collides with another strong laser pulse, which decelerates the electrons due to radiation-reaction effect and results in a significant compression of the proton energy spectra because of the charge separation force. In the considered regime the SEs are demonstrated in the shift of the mean energy of the protons up to hundreds of MeV. This effect is robust with respect to the laser and target parameters and measurable in soon available strong laser facilities.

physics.plasm-ph↗
arXiv2019

Synergic Cherenkov-Compton Radiation

In vacuum with an induced by strong electromagnetic wave refraction index larger than unity, an ultra-relativistic electron emits Cherenkov radiation. During the interaction with this wave the electron also radiates photons via the Compton scattering. Synergic Cherenkov-Compton process can be observed by colliding laser accelerated electrons with a high intensity electromagnetic pulse. Extremely high energy photons cannot be emitted via the Cherenkov radiation because the vacuum refraction index tends to unity at these energies. Experiments on studying these phenomena will reveal the properties of vacuum predicted by nonlinear quantum electrodynamics.

physics.plasm-ph↗
arXiv2019

Boosted High Order Harmonics from Electron Density Singularity Formed at the Relativistic Laser Bow Wave

We demonstrate coherent hard electromagnetic radiation generation from reflection by the electron density singularity formed at the relativistic bow wave in laser plasma via particle-in-cell simulations. Wake and bow waves driven by an intense laser pulse form an electron density singularity at the laser pulse front where they join. A counter-propagating laser pulse is reflected at the electron density modulations moving with relativistic velocity. The reflected electromagnetic pulse is compressed and its frequency is upshifted. Its frequency spectrum contains relativistic harmonics of the driver pulse frequency generated at the bow wave front, all upshifted with the same factor as the fundamental mode of the incident light.

physics.plasm-ph↗
arXiv2019

Feasibility of optical probing of relativistic plasma singularities

Singularities in multi-stream flows of relativistic plasmas can efficiently produce coherent high-frequency radiation, as exemplified in the concepts of Relativistic Flying Mirror [S. V. Bulanov, et al., Phys. Rev. Lett. 91, 085001 (2003)] and Burst Intensification by Singularity Emitting Radiation (BISER) [Pirozhkov, et al., Scientific Reports 7, 17968 (2017)]. Direct observation of these singularities is challenging due to their extreme sharpness (tens of nanometers), relativistic velocity, and transient non-local nature. We propose to use ultrafast (a few light cycles) optical probe for identifying relativistic plasma singularities. Our Particle-in-Cell (PIC) simulations show that this diagnostic is feasible.

physics.plasm-ph↗
arXiv2017

Multi-GeV electron-positron beam generation from laser-electron scattering

The new generation of laser facilities is expected to deliver short (10 fs - 100 fs) laser pulses with 10 - 100 PW of peak power. This opens an opportunity to study matter at extreme intensities in the laboratory and provides access to new physics. Here we propose to scatter GeV-class electron beams from laser-plasma accelerators with a multi-PW laser at normal incidence. In this configuration, one can both create and accelerate electron-positron pairs. The new particles are generated in the laser focus and gain relativistic momentum in the direction of laser propagation. Short focal length is an advantage, as it allows the particles to be ejected from the focal region with a net energy gain in vacuum. Electron-positron beams obtained in this setup have a low divergence, are quasi-neutral and spatially separated from the initial electron beam. The pairs attain multi-GeV energies which are not limited by the maximum energy of the initial electron beam. We present an analytical model for the expected energy cutoff, supported by 2D and 3D particle-in-cell simulations. The experimental implications, such as the sensitivity to temporal synchronisation and laser duration is assessed to provide guidance for the future experiments.

physics.plasm-ph↗
arXiv2017

Laser boron fusion reactor with picosecond petawatt block ignition

For developing a laser boron fusion reactor driven by picosecond laser pulses of more than 30 petawatts power, advances are reported about computations for the plasma block generation by the dielectric explosion of the interaction. Further results are about the direct drive ignition mechanism by a single laser pulse without the problems of spherical irradiation. For the sufficiently large stopping lengths of the generated alpha particles in the plasma results from other projects can be used.

physics.plasm-ph↗
arXiv2017

Gravitational wave generation by interaction of high power lasers with matter using shock waves

Gravitational wave generation by a strong shock wave in the interaction of high power laser with matter is analyzed in linear approximation of gravitational theory. The analytical formulas and estimates are derived for the metric perturbations and the radiated power of the generated gravitational waves. Furthermore the characteristics of polarization and the behavior of test particles are investigated in the presence of gravitational wave which will be important for the detection.

gr-qc↗