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Fundamental Physics At Extremes|20 Article(s)
Current status and highlights of the ELI-NP research program
K. A. Tanaka, K. M. Spohr, D. L. Balabanski, S. Balascuta, L. Capponi, M. O. Cernaianu, M. Cuciuc, A. Cucoanes, I. Dancus, A. Dhal, B. Diaconescu, D. Doria, P. Ghenuche, D. G. Ghita, S. Kisyov, V. Nastasa, J. F. Ong, F. Rotaru, D. Sangwan, P.-A. S?derstr?m, D. Stutman, G. Suliman, O. Tesileanu, L. Tudor, N. Tsoneva, C. A. Ur, D. Ursescu, and N. V. Zamfir
The emergence of a new era reaching beyond current state-of-the-art ultrashort and ultraintense laser technology has been enabled by the approval of around € 850 million worth of structural funds in 2011–2012 by the European Commission for the installation of Extreme Light Infrastructure (ELI). The ELI project consists of three pillars being built in the Czech Republic, Hungary, and Romania. This challenging proposal is based on recent technical progress allowing ultraintense laser fields in which intensities will soon be reaching as high as I0 ～ 1023 W cm?2. This tremendous technological advance has been brought about by the invention of chirped pulse amplification by Mourou and Strickland. Romania is hosting the ELI for Nuclear Physics (ELI-NP) pillar in M?gurele near Bucharest. The new facility, currently under construction, is intended to serve the broad national, European, and international scientific community. Its mission covers scientific research at the frontier of knowledge involving two domains. The first is laser-driven experiments related to NP, strong-field quantum electrodynamics, and associated vacuum effects. The second research domain is based on the establishment of a Compton-backscattering-based, high-brilliance, and intense γ beam with Eγ ? 19.5 MeV, which represents a merger between laser and accelerator technology. This system will allow the investigation of the nuclear structure of selected isotopes and nuclear reactions of relevance, for example, to astrophysics with hitherto unprecedented resolution and accuracy. In addition to fundamental themes, a large number of applications with significant societal impact will be developed. The implementation of the project started in January 2013 and is spearheaded by the ELI-NP/Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). Experiments will begin in early 2020. The emergence of a new era reaching beyond current state-of-the-art ultrashort and ultraintense laser technology has been enabled by the approval of around € 850 million worth of structural funds in 2011–2012 by the European Commission for the installation of Extreme Light Infrastructure (ELI). The ELI project consists of three pillars being built in the Czech Republic, Hungary, and Romania. This challenging proposal is based on recent technical progress allowing ultraintense laser fields in which intensities will soon be reaching as high as I0 ～ 1023 W cm?2. This tremendous technological advance has been brought about by the invention of chirped pulse amplification by Mourou and Strickland. Romania is hosting the ELI for Nuclear Physics (ELI-NP) pillar in M?gurele near Bucharest. The new facility, currently under construction, is intended to serve the broad national, European, and international scientific community. Its mission covers scientific research at the frontier of knowledge involving two domains. The first is laser-driven experiments related to NP, strong-field quantum electrodynamics, and associated vacuum effects. The second research domain is based on the establishment of a Compton-backscattering-based, high-brilliance, and intense γ beam with Eγ ? 19.5 MeV, which represents a merger between laser and accelerator technology. This system will allow the investigation of the nuclear structure of selected isotopes and nuclear reactions of relevance, for example, to astrophysics with hitherto unprecedented resolution and accuracy. In addition to fundamental themes, a large number of applications with significant societal impact will be developed. The implementation of the project started in January 2013 and is spearheaded by the ELI-NP/Horia Hulubei National Institute for Physics and Nuclear Engineering (IFIN-HH). Experiments will begin in early 2020.
Matter and Radiation at Extremes
- Publication Date: Apr. 01, 2020
- Vol. 5, Issue 2, 24402 (2020)
High pressure effects on the excitation spectra and dipole properties of Li, Be+, and B2+ atoms under confinement
C. Martínez-Flores, and R. Cabrera-Trujillo
Properties of atoms and molecules undergo significant changes when subjected to spatial confinement. We study the excitation spectra of lithium-like atoms in the initial 1s22s electronic configuration when confined by an impenetrable spherical cavity. We implement Slater’s X-α method in Hartree–Fock theory to obtain the excitation spectrum. We verify that as the cavity size decreases, the total, 2s, 2p, and higher excited energy levels increase. Furthermore, we confirm the existence of crossing points between ns–np states for low values of the confinement radius such that the ns → np dipole transition becomes zero at that critical pressure. The crossing points of the s–p states imply that instead of photon absorption, one observes photon emission for cavities with radius smaller than the critical radius. Hence, the dipole oscillator strength associated with the 2s → 2p transition becomes negative, and for higher pressures, the 2s → 3p dipole oscillator strength transition becomes larger than unity. We validate the completeness of the spectrum by calculating the Thomas–Reiche–Kuhn sum rule, as well as the static dipole polarizability and mean excitation energy of lithium-like atoms. We find that the static dipole polarizability decreases and exhibits a sudden change at the critical pressure for the absorption-to-emission transition. The mean excitation energy increases as the pressure rises. However, as a consequence of the critical transition from absorption to emission, the mean excitation energy becomes undetermined for higher pressures, with implications for material damage under extreme conditions. For unconfined systems, our results show good to excellent agreement with data found in the literature. Properties of atoms and molecules undergo significant changes when subjected to spatial confinement. We study the excitation spectra of lithium-like atoms in the initial 1s22s electronic configuration when confined by an impenetrable spherical cavity. We implement Slater’s X-α method in Hartree–Fock theory to obtain the excitation spectrum. We verify that as the cavity size decreases, the total, 2s, 2p, and higher excited energy levels increase. Furthermore, we confirm the existence of crossing points between ns–np states for low values of the confinement radius such that the ns → np dipole transition becomes zero at that critical pressure. The crossing points of the s–p states imply that instead of photon absorption, one observes photon emission for cavities with radius smaller than the critical radius. Hence, the dipole oscillator strength associated with the 2s → 2p transition becomes negative, and for higher pressures, the 2s → 3p dipole oscillator strength transition becomes larger than unity. We validate the completeness of the spectrum by calculating the Thomas–Reiche–Kuhn sum rule, as well as the static dipole polarizability and mean excitation energy of lithium-like atoms. We find that the static dipole polarizability decreases and exhibits a sudden change at the critical pressure for the absorption-to-emission transition. The mean excitation energy increases as the pressure rises. However, as a consequence of the critical transition from absorption to emission, the mean excitation energy becomes undetermined for higher pressures, with implications for material damage under extreme conditions. For unconfined systems, our results show good to excellent agreement with data found in the literature.
Matter and Radiation at Extremes
- Publication Date: Apr. 01, 2020
- Vol. 5, Issue 2, 24401 (2020)
X-ray emission characteristics in magnetically driven plasma jet experiments on PTS facility
Qiang Xu, Shaotong Zhou, Kun-lun Wang, Siqun Zhang, Hongchun Cai, Xiao Ren, Pan Liu, Xian bin Huang, Li Zhao, and Wenkang Zou
Jets are commonly observed astrophysical phenomena. To study the x-ray emission characteristics of jets, a series of radial foil Z-pinch experiments are carried out on the Primary Test Stand at the Institute of Fluid Physics, China Academy of Engineering Physics. In these experiments, x-ray emission ranging from the soft region (0.1–10 keV) to the hard region (10 keV–500 keV) is observed when the magnetic cavity breaks. The radiation flux of soft x-rays is measured by an x-ray diode and the dose rate of the hard x-rays by an Si-PIN detector. The experimental results indicate that the energy of the soft x-rays is several tens of kilojoules and that of the hard x-rays is ～200 J. The radiation mechanism of the x-ray emission is briefly analyzed. This analysis indicates that the x-ray energy and the plasma kinetic energy come from the magnetic energy when the magnetic cavity breaks. The soft x-rays are thought to be produced by bremsstrahlung of thermal electrons (～100 eV), and the hard x-rays by bremsstrahlung of super-hot electrons (～mega-electron-volt). These results may be helpful to explain the x-ray emission by the jets from young stellar objects. Jets are commonly observed astrophysical phenomena. To study the x-ray emission characteristics of jets, a series of radial foil Z-pinch experiments are carried out on the Primary Test Stand at the Institute of Fluid Physics, China Academy of Engineering Physics. In these experiments, x-ray emission ranging from the soft region (0.1–10 keV) to the hard region (10 keV–500 keV) is observed when the magnetic cavity breaks. The radiation flux of soft x-rays is measured by an x-ray diode and the dose rate of the hard x-rays by an Si-PIN detector. The experimental results indicate that the energy of the soft x-rays is several tens of kilojoules and that of the hard x-rays is ～200 J. The radiation mechanism of the x-ray emission is briefly analyzed. This analysis indicates that the x-ray energy and the plasma kinetic energy come from the magnetic energy when the magnetic cavity breaks. The soft x-rays are thought to be produced by bremsstrahlung of thermal electrons (～100 eV), and the hard x-rays by bremsstrahlung of super-hot electrons (～mega-electron-volt). These results may be helpful to explain the x-ray emission by the jets from young stellar objects.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2020
- Vol. 5, Issue 1, 014401 (2020)
Gamma photons and electron-positron pairs from ultra-intense laser-matter interaction: A comparative study of proposed configurations
Yan-Jun Gu, Martin Jirka, Ondrej Klimo, and Stefan Weber
High-energy γ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled, and a number of mechanisms are proposed. Owing to the small cross section, these processes require both an ultra-intense laser field and a relativistic electron bunch. The extreme conditions for such scenarios can be achieved through recent developments in laser technology. Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally. High-energy positron beams generated via a multiphoton process have recently been observed too. This paper reviews the principles of γ-ray emission and e+e? pair creation in the context of laser–plasma interaction. Several proposed experimental setups for γ-ray emission and e+e? pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of the γ-photon and positron beams produced for ultrashort (15 fs) and longer (150 fs) multi-petawatt laser beams. High-energy γ-photon generation via nonlinear Compton scattering and electron–positron pair creation via the Breit–Wheeler process driven by laser–plasma interaction are modeled, and a number of mechanisms are proposed. Owing to the small cross section, these processes require both an ultra-intense laser field and a relativistic electron bunch. The extreme conditions for such scenarios can be achieved through recent developments in laser technology. Photon emission via nonlinear Thomson and Compton scattering has been observed experimentally. High-energy positron beams generated via a multiphoton process have recently been observed too. This paper reviews the principles of γ-ray emission and e+e? pair creation in the context of laser–plasma interaction. Several proposed experimental setups for γ-ray emission and e+e? pair creation by ultra-intense laser pulses are compared in terms of their efficiency and the quality of the γ-photon and positron beams produced for ultrashort (15 fs) and longer (150 fs) multi-petawatt laser beams.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 6, 064403 (2019)
X-ray spectroscopy evidence for plasma shell formation in experiments modeling accretion columns in young stars
E. D. Filippov, I. Yu. Skobelev, G. Revet, S. N. Chen, B. Khiar, A. Ciardi, D. Khaghani, D. P. Higginson, S. A. Pikuz, and J. Fuchs
Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation. In particular, we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars [G. Revet et al., Sci. Adv. 3, e1700982 (2017)]. The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments. We demonstrate that we can infer the formation of a plasma shell, surrounding the accretion column at the location of impact with the stellar surface, and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object. In our experiments, the accretion column is modeled by having a collimated narrow (1 mm diameter) plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle, mimicking the high-density region of the stellar chromosphere. A combined approach using steady-state and quasi-stationary models was successfully applied to measure the parameters of the plasma all along its propagation, at the impact site, and in the structure surrounding the impact region. The formation of a hot plasma shell, surrounding the denser and colder core, formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy. Recent achievements in laboratory astrophysics experiments with high-power lasers have allowed progress in our understanding of the early stages of star formation. In particular, we have recently demonstrated the possibility of simulating in the laboratory the process of the accretion of matter on young stars [G. Revet et al., Sci. Adv. 3, e1700982 (2017)]. The present paper focuses on x-ray spectroscopy methods that allow us to investigate the complex plasma hydrodynamics involved in such experiments. We demonstrate that we can infer the formation of a plasma shell, surrounding the accretion column at the location of impact with the stellar surface, and thus resolve the present discrepancies between mass accretion rates derived from x-ray and optical-radiation astronomical observations originating from the same object. In our experiments, the accretion column is modeled by having a collimated narrow (1 mm diameter) plasma stream first propagate along the lines of a large-scale external magnetic field and then impact onto an obstacle, mimicking the high-density region of the stellar chromosphere. A combined approach using steady-state and quasi-stationary models was successfully applied to measure the parameters of the plasma all along its propagation, at the impact site, and in the structure surrounding the impact region. The formation of a hot plasma shell, surrounding the denser and colder core, formed by the incoming stream of matter is observed near the obstacle using x-ray spatially resolved spectroscopy.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 6, 064402 (2019)
Photonuclear production of medical isotopes 62,64Cu using intense laser-plasma electron source
ZhiGuo Ma, HaoYang Lan, WeiYuan Liu, ShaoDong Wu, Yi Xu, ZhiChao Zhu, and Wen Luo
62,64Cu are radioisotopes of medical interest that can be used for positron emission tomography (PET) imaging. Moreover, 64Cu has β? decay characteristics that allow for targeted radiotherapy of cancer. In the present work, a novel approach to experimentally demonstrate the production of 62,64Cu isotopes from photonuclear reactions is proposed in which large-current laser-based electron (e?) beams are generated from the interaction between sub-petawatt laser pulses and near-critical-density plasmas. According to simulations, at a laser intensity of 3.4 × 1021 W/cm2, a dense e? beam with a total charge of 100 nC can be produced, and this in turn produces bremsstrahlung radiation of the order of 1010 photons per laser shot, in the region of the giant dipole resonance. The bremsstrahlung radiation is guided to a natural Cu target, triggering photonuclear reactions to produce the medical isotopes 62,64Cu. An optimal target geometry is employed to maximize the photoneutron yield, and 62,64Cu with appropriate activities of 0.18 GBq and 0.06 GBq are obtained for irradiation times equal to their respective half-lives multiplied by three. The detection of the characteristic energy for the nuclear transitions of 62, 64Cu is also studied. The results of our calculations support the prospect of producing PET isotopes with gigabecquerel-level activity (equivalent to the required patient dose) using upcoming high-intensity laser facilities. 62,64Cu are radioisotopes of medical interest that can be used for positron emission tomography (PET) imaging. Moreover, 64Cu has β? decay characteristics that allow for targeted radiotherapy of cancer. In the present work, a novel approach to experimentally demonstrate the production of 62,64Cu isotopes from photonuclear reactions is proposed in which large-current laser-based electron (e?) beams are generated from the interaction between sub-petawatt laser pulses and near-critical-density plasmas. According to simulations, at a laser intensity of 3.4 × 1021 W/cm2, a dense e? beam with a total charge of 100 nC can be produced, and this in turn produces bremsstrahlung radiation of the order of 1010 photons per laser shot, in the region of the giant dipole resonance. The bremsstrahlung radiation is guided to a natural Cu target, triggering photonuclear reactions to produce the medical isotopes 62,64Cu. An optimal target geometry is employed to maximize the photoneutron yield, and 62,64Cu with appropriate activities of 0.18 GBq and 0.06 GBq are obtained for irradiation times equal to their respective half-lives multiplied by three. The detection of the characteristic energy for the nuclear transitions of 62, 64Cu is also studied. The results of our calculations support the prospect of producing PET isotopes with gigabecquerel-level activity (equivalent to the required patient dose) using upcoming high-intensity laser facilities.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 6, 064401 (2019)
Application of quantum-statistical methods to studies of thermodynamic and radiative processes in hot dense plasmas
Nikolay Yu. Orlov, Maxim A. Kadatskiy, Oleg B. Denisov, and Konstantin V. Khishchenko
Calculations of thermodynamic and radiative characteristics of hot dense plasmas within different quantum-statistical approaches, such as the use of the Hartree–Fock–Slater model and the ion model, are presented. Calculated equations of state of different substances are used to investigate findings from absolute and relative measurements of the compressibility of solid aluminum samples in strong shock waves. It is shown that our calculated Hugoniot adiabat of aluminum is in a good agreement with experimental data and other theoretical results from first principles. We also present a review of the most important applications of the quantum-statistical approach to the study of radiative properties of hot dense plasmas. It includes the optimization problem of hohlraum wall materials for laser inertial fusion, calculations of the radiative efficiency of complex materials for optically thin plasma in X-pinch, modeling of radiative and gas-dynamic processes in plasma for experiments, where both intense laser and heavy ion beams are used, and temperature diagnostics for X- and Z-pinch plasmas. Calculations of thermodynamic and radiative characteristics of hot dense plasmas within different quantum-statistical approaches, such as the use of the Hartree–Fock–Slater model and the ion model, are presented. Calculated equations of state of different substances are used to investigate findings from absolute and relative measurements of the compressibility of solid aluminum samples in strong shock waves. It is shown that our calculated Hugoniot adiabat of aluminum is in a good agreement with experimental data and other theoretical results from first principles. We also present a review of the most important applications of the quantum-statistical approach to the study of radiative properties of hot dense plasmas. It includes the optimization problem of hohlraum wall materials for laser inertial fusion, calculations of the radiative efficiency of complex materials for optically thin plasma in X-pinch, modeling of radiative and gas-dynamic processes in plasma for experiments, where both intense laser and heavy ion beams are used, and temperature diagnostics for X- and Z-pinch plasmas.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 5, 054403 (2019)
Extreme brightness laser-based neutron pulses as a pathway for investigating nucleosynthesis in the laboratory
S. N. Chen, F. Negoita, K. Spohr, E. d’Humières, I. Pomerantz, and J. Fuchs
With the much-anticipated multi-petawatt (PW) laser facilities that are coming online, neutron sources with extreme fluxes could soon be in reach. Such sources would rely on spallation by protons accelerated by the high-intensity lasers. These high neutron fluxes would make possible not only direct measurements of neutron capture and β-decay rates related to the r-process of nucleosynthesis of heavy elements, but also such nuclear measurements in a hot plasma environment, which would be beneficial for s-process investigations in astrophysically relevant conditions. This could, in turn, finally allow possible reconciliation of the observed element abundances in stars and those derived from simulations, which at present show large discrepancies. Here, we review a possible pathway to reach unprecedented neutron fluxes using multi-PW lasers, as well as strategies to perform measurements to investigate the r- and s-processes of nucleosynthesis of heavy elements in cold matter, as well as in a hot plasma environment. With the much-anticipated multi-petawatt (PW) laser facilities that are coming online, neutron sources with extreme fluxes could soon be in reach. Such sources would rely on spallation by protons accelerated by the high-intensity lasers. These high neutron fluxes would make possible not only direct measurements of neutron capture and β-decay rates related to the r-process of nucleosynthesis of heavy elements, but also such nuclear measurements in a hot plasma environment, which would be beneficial for s-process investigations in astrophysically relevant conditions. This could, in turn, finally allow possible reconciliation of the observed element abundances in stars and those derived from simulations, which at present show large discrepancies. Here, we review a possible pathway to reach unprecedented neutron fluxes using multi-PW lasers, as well as strategies to perform measurements to investigate the r- and s-processes of nucleosynthesis of heavy elements in cold matter, as well as in a hot plasma environment.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 5, 054402 (2019)
A semi-classical model for the charge exchange and energy loss of slow highly charged ions in ultrathin materials
Xun Guo, Yanjun Fu, Xitong Zhang, Xinwei Wang, Yan Chen, and Jianming Xue
We present a simple and reliable method, based on the over-barrier model and Lindhard’s formula, to calculate the energy loss, charge transfer, and normalized intensity of highly charged ions penetrating through 2D ultrathin materials, including graphene and carbon nanomembranes. According to our results, the interaction between the ions and the 2D material can be simplified as an equivalent two-body collision, and we find that full consideration of the charge exchange effect is key to understanding the mechanism of ion energy deposition in an ultrathin target. Not only can this semiclassical model be used to evaluate the ion irradiation effect to a very good level of accuracy, but it also provides important guidance for tailoring the properties of 2D materials using ion beams. We present a simple and reliable method, based on the over-barrier model and Lindhard’s formula, to calculate the energy loss, charge transfer, and normalized intensity of highly charged ions penetrating through 2D ultrathin materials, including graphene and carbon nanomembranes. According to our results, the interaction between the ions and the 2D material can be simplified as an equivalent two-body collision, and we find that full consideration of the charge exchange effect is key to understanding the mechanism of ion energy deposition in an ultrathin target. Not only can this semiclassical model be used to evaluate the ion irradiation effect to a very good level of accuracy, but it also provides important guidance for tailoring the properties of 2D materials using ion beams.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 5, 054401 (2019)
Ejecta velocities in twice-shocked liquid metals under extreme conditions: A hydrodynamic approach
V. Karkhanis, and P. Ramaprabhu
We apply a hydrodynamic approach to analyze ejecta emanating from doubly shocked liquid metals. In particular, we are interested in characterizing ejecta velocities in such situations by treating the problem as a limiting case of the Richtmyer–Meshkov instability. We find existing models for ejecta velocities do not adequately capture all the relevant physics, including compressibility, nonlinearities, and nonstandard shapes. We propose an empirical model that is capable of describing ejecta behavior across the entire parameter range of interest. We then suggest a protocol to apply this model when the donor material is shocked twice in rapid succession. Finally, the model and the suggested approach are validated using detailed continuum hydrodynamic simulations. The results provide a baseline understanding of the hydrodynamic aspects of ejecta, which can then be used to interpret experimental data from target experiments. We apply a hydrodynamic approach to analyze ejecta emanating from doubly shocked liquid metals. In particular, we are interested in characterizing ejecta velocities in such situations by treating the problem as a limiting case of the Richtmyer–Meshkov instability. We find existing models for ejecta velocities do not adequately capture all the relevant physics, including compressibility, nonlinearities, and nonstandard shapes. We propose an empirical model that is capable of describing ejecta behavior across the entire parameter range of interest. We then suggest a protocol to apply this model when the donor material is shocked twice in rapid succession. Finally, the model and the suggested approach are validated using detailed continuum hydrodynamic simulations. The results provide a baseline understanding of the hydrodynamic aspects of ejecta, which can then be used to interpret experimental data from target experiments.
Matter and Radiation at Extremes
- Publication Date: Jan. 01, 2019
- Vol. 4, Issue 4, 044402 (2019)
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