Dynamics and spectral transmission of Al plasma produced by extreme ultraviolet(EUV)irradiation of 0.75-mm thick Al foil is investigated.The EUV radiation with the peak power density in the range of 0.19-0.54 TW/cm 2 ...Dynamics and spectral transmission of Al plasma produced by extreme ultraviolet(EUV)irradiation of 0.75-mm thick Al foil is investigated.The EUV radiation with the peak power density in the range of 0.19-0.54 TW/cm 2 is provided by Z-pinch formed by W multiwire array implosion in the Angara-5-1 facility.Geometry of the experiment ensures that there are no plasma fluxes from the pinch toward the Al foil and plasma.The same EUV source is used as a back illuminator for obtaining the absorption spectrum of Al plasma in the wavelength range of 5e24 nm.It comprises absorption lines of ions Al^(4+),Al^(5+),Al^(6+),Al^(7+).Analysis of relative intensities of the lines shows that those ions are formed in dense Al plasma with a temperature of~20 eV.Dynamics of Al plasma has been investigated with transverse laser probing.We have also performed radiation-gas-dynamics simulations of plasma dynamics affected by external radiation,which includes self-consistent radiation transport in a plasma shell.The simulations show good agreement with an experimental absorption spectrum and with experimental data concerning plasma dynamics,as well as with the analysis of line absorption spectrum.This confirms the correctness of the physical model underlying these simulations.展开更多
Background:Preservation of anatomic integrity and function of the cranial nerves during the removal of skull base tumors is one of the most challenging procedures in endoscopic endonasal surgery.It is possible to use ...Background:Preservation of anatomic integrity and function of the cranial nerves during the removal of skull base tumors is one of the most challenging procedures in endoscopic endonasal surgery.It is possible to use intraoperative mapping and identification of the cranial nerves in order to facilitate their preservation.The purpose of this study was to evaluate the effectiveness of intraoperative trigger electromyography in prevention of iatrogenic damage to the cranial nerves.Methods:Twenty three patients with various skull base tumors(chordomas,neuromas,pituitary adenomas,meningiomas,cholesteatomas)underwent mapping and identification of cranial nerves during tumor removal using the endoscopic endonasal approach in Department of Neurooncology of Federal State Autonomous Institution"N.N.Burdenko National Medical Research Center of Neurosurgery"of the Ministry of Health of the Russian Federation from 2013 to 2018.During the surgical interventions,mapping and identification of the cranial nerves were carried out using electromyography in triggered mode.The effectiveness of the method was evaluated based on a comparison with a control group(41 patients).Results:In the main group of patients,44 nerves were examined during surgery using triggered electromyography.During the study,the III,V,VI,VII,and XII cranial nerves were identified intraoperatively.Postoperative cranial nerve deficiency was observed in 5 patients in the study group and in 13 patients in the control group.The average length of hospitalization was 9 days.Conclusion:We did not receive statistically significant data supporting the fact that intraoperative identification of cranial nerves using trigger electromyography reduces the incidence of postoperative complications in the form of cranial nerve deficits(p=0.56),but the odds ratio(0.6)suggests a less frequent occurrence of complications in the study group.Based on our experience,the trigger electromyography methodology appears quite promising and requires further research.展开更多
Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the ...Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativisticlaser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In anexperiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 10^(19) W/cm^(2)laser intensity. The spectrum of directed x-raysin the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0°and 10°to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 10^(13) photons/sr withenergies >5 keV measured at 0°to the laser axis and a brilliance of 10^(21) photons s^(−1) mm^(−2) mrad−2(0.1%BW)−1. The angular distributionof the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emissiontime, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laserfacilities.展开更多
Direct laser acceleration(DLA)of electrons in a plasma of near-critical electron density(NCD)and the associated synchrotron-like radiation are discussed for moderate relativistic laser intensity(normalized laser ampli...Direct laser acceleration(DLA)of electrons in a plasma of near-critical electron density(NCD)and the associated synchrotron-like radiation are discussed for moderate relativistic laser intensity(normalized laser amplitude a0≤4.3)and ps length pulse.This regime is typical of kJ PW-class laser facilities designed for high-energy-density(HED)research.In experiments at the PHELIX facility,it has been demonstrated that interaction of a 1019 W/cm2 sub-ps laser pulse with a sub-mm length NCD plasma results in the generation of high-current well-directed superponderomotive electrons with an effective temperature ten times higher than the ponderomotive potential[Rosmej et al.,Plasma Phys.Controlled Fusion 62,115024(2020)].Three-dimensional particle-in-cell simulations provide good agreement with the measured electron energy distribution and are used in the current work to study synchrotron radiation from the DLA-accelerated electrons.The resulting x-ray spectrum with a critical energy of 5 keV reveals an ultrahigh photon number of 731011 in the 1–30 keV photon energy range at the focused laser energy of 20 J.Numerical simulations of betatron x-ray phase contrast imaging based on the DLA process for the parameters of a PHELIX laser are presented.The results are of interest for applications in HED experiments,which require a ps x-ray pulse and a high photon flux.展开更多
The time-of-flight technique coupled with semiconductor detectors is a powerful instrument to provide real-time characterization of ions accelerated because of laser-matter interactions.Nevertheless,the presence of st...The time-of-flight technique coupled with semiconductor detectors is a powerful instrument to provide real-time characterization of ions accelerated because of laser-matter interactions.Nevertheless,the presence of strong electromagnetic pulses(EMPs)generated during the interactions can severely hinder its employment.For this reason,the diagnostic system must be designed to have high EMP shielding.Here we present a new advanced prototype of detector,developed at ENEA-Centro Ricerche Frascati(Italy),with a large-area(15 mm×15 mm)polycrystalline diamond sensor having 150 μm thickness.The tailored detector design and testing ensure high sensitivity and,thanks to the fast temporal response,high-energy resolution of the reconstructed ion spectrum.The detector was offline calibrated and then successfully tested during an experimental campaign carried out at the PHELIX laser facility(E_(L)~100 J,τ_(L)=750 fs,I_(L)(1-2.5)×10^(19)W/cm^(2))at GSI(Germany).The high rejection to EMP fields was demonstrated and suitable calibrated spectra of the accelerated protons were obtained.展开更多
Large-amplitude electromagnetic radiofrequency fields are created by the charge-separation induced in interactions of high-intensity,short-pulse lasers with solid targets and have intensity that decreases with the dis...Large-amplitude electromagnetic radiofrequency fields are created by the charge-separation induced in interactions of high-intensity,short-pulse lasers with solid targets and have intensity that decreases with the distance from the target.Alternatively,it was experimentally proved very recently that charged particles emitted by petawatt laser±target interactions can be deposited on a capacitor-collector structure,far away from the target,and lead to the rapid(nanosecond-scale)generation of large quasi-static electric fields(MV/m),over wide regions.We demonstrate here the generation of both these fields in experiments at the PHELIX laser facility,with approximately 20 J energy and approximately 10^(19)W/cm^(2)intensity,for picoseconds laser pulses,interacting with pre-ionized polymer foams of near critical density.Quasi-static fields,up to tens of k V/m,were here observed at distances larger than 1 m from the target,with results much higher than the radiofrequency component.This is of primary importance for inertial-confinement fusion and laser±plasma acceleration and also for promising applications in different scenarios.展开更多
We demonstrated experimentally the formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2×1017W/cm2onto the edge of an aluminum foil.The electrons...We demonstrated experimentally the formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2×1017W/cm2onto the edge of an aluminum foil.The electrons had energy distributions peaking in the 0.2–0.8 MeV range with energy spread less than 20%.The acceleration mechanism related to the generation of a plasma wave as a result of self-modulation instability of a laser pulse in a dense plasma formed by a prepulse(arriving 12 ns before the main pulse)is considered.One-dimensional and two-dimensional Particle in Cell(PIC)simulations of the laser–plasma interaction showed that effective excitation of a plasma wave as well as trapping and acceleration of an electron beam with an energy on the order of 1 MeV may occur in the presence of sharp gradients in plasma density and in the temporal shape of the pulse.展开更多
We have developed the two and half-dimension electromagnetic relativistic electron and mobile ion cloud-in-cell(CIC)code.Mechanisms of the fast ignition and interaction of ultra-intense and ultra-short pulse laser wit...We have developed the two and half-dimension electromagnetic relativistic electron and mobile ion cloud-in-cell(CIC)code.Mechanisms of the fast ignition and interaction of ultra-intense and ultra-short pulse laser with plasma are analysed theoretically and simulated numerically using CIC code.Strong flows of relativistic electron and form of the channel are observed.The results show that the temperature of superhot electron is about MeV to tens of MeV,and the boring velocity is 0.05c-0.1c with c being the light speed.Some preliminary scale laws are obtained.This simulation quantitatively reproduces the experimental results at early and long times.展开更多
基金The work was partially supported by RSF under Grant No.16-12-10487by the RFBR project 15-02-04411 and 15-01-06195.
文摘Dynamics and spectral transmission of Al plasma produced by extreme ultraviolet(EUV)irradiation of 0.75-mm thick Al foil is investigated.The EUV radiation with the peak power density in the range of 0.19-0.54 TW/cm 2 is provided by Z-pinch formed by W multiwire array implosion in the Angara-5-1 facility.Geometry of the experiment ensures that there are no plasma fluxes from the pinch toward the Al foil and plasma.The same EUV source is used as a back illuminator for obtaining the absorption spectrum of Al plasma in the wavelength range of 5e24 nm.It comprises absorption lines of ions Al^(4+),Al^(5+),Al^(6+),Al^(7+).Analysis of relative intensities of the lines shows that those ions are formed in dense Al plasma with a temperature of~20 eV.Dynamics of Al plasma has been investigated with transverse laser probing.We have also performed radiation-gas-dynamics simulations of plasma dynamics affected by external radiation,which includes self-consistent radiation transport in a plasma shell.The simulations show good agreement with an experimental absorption spectrum and with experimental data concerning plasma dynamics,as well as with the analysis of line absorption spectrum.This confirms the correctness of the physical model underlying these simulations.
文摘Background:Preservation of anatomic integrity and function of the cranial nerves during the removal of skull base tumors is one of the most challenging procedures in endoscopic endonasal surgery.It is possible to use intraoperative mapping and identification of the cranial nerves in order to facilitate their preservation.The purpose of this study was to evaluate the effectiveness of intraoperative trigger electromyography in prevention of iatrogenic damage to the cranial nerves.Methods:Twenty three patients with various skull base tumors(chordomas,neuromas,pituitary adenomas,meningiomas,cholesteatomas)underwent mapping and identification of cranial nerves during tumor removal using the endoscopic endonasal approach in Department of Neurooncology of Federal State Autonomous Institution"N.N.Burdenko National Medical Research Center of Neurosurgery"of the Ministry of Health of the Russian Federation from 2013 to 2018.During the surgical interventions,mapping and identification of the cranial nerves were carried out using electromyography in triggered mode.The effectiveness of the method was evaluated based on a comparison with a control group(41 patients).Results:In the main group of patients,44 nerves were examined during surgery using triggered electromyography.During the study,the III,V,VI,VII,and XII cranial nerves were identified intraoperatively.Postoperative cranial nerve deficiency was observed in 5 patients in the study group and in 13 patients in the control group.The average length of hospitalization was 9 days.Conclusion:We did not receive statistically significant data supporting the fact that intraoperative identification of cranial nerves using trigger electromyography reduces the incidence of postoperative complications in the form of cranial nerve deficits(p=0.56),but the odds ratio(0.6)suggests a less frequent occurrence of complications in the study group.Based on our experience,the trigger electromyography methodology appears quite promising and requires further research.
基金supported by the Czech Ministry of Education,Youth and Sports(Project No.CZ.02.2.69/0.0/0.0/18_053/0016980)the Grant Agency of the Czech Republic(Grant No.GM23-05027M).
文摘Directed x-rays produced in the interaction of sub-picosecond laser pulses of moderate relativistic intensity with plasma of near-critical density are investigated. Synchrotron-like (betatron) radiation occurs in the process of direct laser acceleration (DLA) of electrons in a relativisticlaser channel when the electrons undergo transverse betatron oscillations in self-generated quasi-static electric and magnetic fields. In anexperiment at the PHELIX laser system, high-current directed beams of DLA electrons with a mean energy ten times higher than the ponderomotive potential and maximum energy up to 100 MeV were measured at 10^(19) W/cm^(2)laser intensity. The spectrum of directed x-raysin the range of 5–60 keV was evaluated using two sets of Ross filters placed at 0°and 10°to the laser pulse propagation axis. The differential x-ray absorption method allowed for absolute measurements of the angular-dependent photon fluence. We report 10^(13) photons/sr withenergies >5 keV measured at 0°to the laser axis and a brilliance of 10^(21) photons s^(−1) mm^(−2) mrad−2(0.1%BW)−1. The angular distributionof the emission has an FWHM of 14°–16°. Thanks to the ultra-high photon fluence, point-like radiation source, and ultra-short emissiontime, DLA-based keV backlighters are promising for various applications in high-energy-density research with kilojoule petawatt-class laserfacilities.
基金the DFG(Project No.PU 213/9),EPSRC Grant No.EP/P026796/1the Ministry of Science and Higher Education of the Russian Federation(Agreement with Joint Institute for High Temperatures RAS No 075-15-2020-785,dated September 23,2020).
文摘Direct laser acceleration(DLA)of electrons in a plasma of near-critical electron density(NCD)and the associated synchrotron-like radiation are discussed for moderate relativistic laser intensity(normalized laser amplitude a0≤4.3)and ps length pulse.This regime is typical of kJ PW-class laser facilities designed for high-energy-density(HED)research.In experiments at the PHELIX facility,it has been demonstrated that interaction of a 1019 W/cm2 sub-ps laser pulse with a sub-mm length NCD plasma results in the generation of high-current well-directed superponderomotive electrons with an effective temperature ten times higher than the ponderomotive potential[Rosmej et al.,Plasma Phys.Controlled Fusion 62,115024(2020)].Three-dimensional particle-in-cell simulations provide good agreement with the measured electron energy distribution and are used in the current work to study synchrotron radiation from the DLA-accelerated electrons.The resulting x-ray spectrum with a critical energy of 5 keV reveals an ultrahigh photon number of 731011 in the 1–30 keV photon energy range at the focused laser energy of 20 J.Numerical simulations of betatron x-ray phase contrast imaging based on the DLA process for the parameters of a PHELIX laser are presented.The results are of interest for applications in HED experiments,which require a ps x-ray pulse and a high photon flux.
基金funding from the Euratom research and training program 2014-2018 and 2019-2020 under grant agreement No.633053funding from LASERLAB-EUROPE(grant agreement No.654148,European Union’s Horizon 2020 research and innovation program)supported by the Ministry of Science and Higher Education of the Russian Federation(Agreement with Joint Institute for High Temperatures RAS No.075-15-2020-785,dated 23 September 2020).
文摘The time-of-flight technique coupled with semiconductor detectors is a powerful instrument to provide real-time characterization of ions accelerated because of laser-matter interactions.Nevertheless,the presence of strong electromagnetic pulses(EMPs)generated during the interactions can severely hinder its employment.For this reason,the diagnostic system must be designed to have high EMP shielding.Here we present a new advanced prototype of detector,developed at ENEA-Centro Ricerche Frascati(Italy),with a large-area(15 mm×15 mm)polycrystalline diamond sensor having 150 μm thickness.The tailored detector design and testing ensure high sensitivity and,thanks to the fast temporal response,high-energy resolution of the reconstructed ion spectrum.The detector was offline calibrated and then successfully tested during an experimental campaign carried out at the PHELIX laser facility(E_(L)~100 J,τ_(L)=750 fs,I_(L)(1-2.5)×10^(19)W/cm^(2))at GSI(Germany).The high rejection to EMP fields was demonstrated and suitable calibrated spectra of the accelerated protons were obtained.
基金funding from the Euratom research and training programs 2014-2018 and 2019-2020 under grant agreement No.633053funding from LASERLAB EUROPE(grant agreement No.654148,European Union’s Horizon 2020 research and innovation program)supported by the Ministry of Science and Higher Education of the Russian Federation(Agreement with Joint Institute for High Temperatures RAS No.075-15-2020-785,dated September 23,2020)。
文摘Large-amplitude electromagnetic radiofrequency fields are created by the charge-separation induced in interactions of high-intensity,short-pulse lasers with solid targets and have intensity that decreases with the distance from the target.Alternatively,it was experimentally proved very recently that charged particles emitted by petawatt laser±target interactions can be deposited on a capacitor-collector structure,far away from the target,and lead to the rapid(nanosecond-scale)generation of large quasi-static electric fields(MV/m),over wide regions.We demonstrate here the generation of both these fields in experiments at the PHELIX laser facility,with approximately 20 J energy and approximately 10^(19)W/cm^(2)intensity,for picoseconds laser pulses,interacting with pre-ionized polymer foams of near critical density.Quasi-static fields,up to tens of k V/m,were here observed at distances larger than 1 m from the target,with results much higher than the radiofrequency component.This is of primary importance for inertial-confinement fusion and laser±plasma acceleration and also for promising applications in different scenarios.
基金supported by the programme ‘Extreme Light Fields and Their Applications’ of the Presidium of the Russian Academy of Sciences
文摘We demonstrated experimentally the formation of monoenergetic beams of accelerated electrons by focusing femtosecond laser radiation with an intensity of 2×1017W/cm2onto the edge of an aluminum foil.The electrons had energy distributions peaking in the 0.2–0.8 MeV range with energy spread less than 20%.The acceleration mechanism related to the generation of a plasma wave as a result of self-modulation instability of a laser pulse in a dense plasma formed by a prepulse(arriving 12 ns before the main pulse)is considered.One-dimensional and two-dimensional Particle in Cell(PIC)simulations of the laser–plasma interaction showed that effective excitation of a plasma wave as well as trapping and acceleration of an electron beam with an energy on the order of 1 MeV may occur in the presence of sharp gradients in plasma density and in the temporal shape of the pulse.
基金Supported by the National High-Tech ICF Commit tee in China,the National Natural Science Foundation of China under Grant No.19735002Sci.&Tech.Funds of CAEP,and Russian Foundation for Basic Research.
文摘We have developed the two and half-dimension electromagnetic relativistic electron and mobile ion cloud-in-cell(CIC)code.Mechanisms of the fast ignition and interaction of ultra-intense and ultra-short pulse laser with plasma are analysed theoretically and simulated numerically using CIC code.Strong flows of relativistic electron and form of the channel are observed.The results show that the temperature of superhot electron is about MeV to tens of MeV,and the boring velocity is 0.05c-0.1c with c being the light speed.Some preliminary scale laws are obtained.This simulation quantitatively reproduces the experimental results at early and long times.
