35 results on '"Guo-Bo Zhang"'
Search Results
2. One-dimensional steady-state model for stimulated Raman and Brillouin backscatter processes in laser-irradiated plasmas
- Author
-
Guo Bo Zhang, Yan Yun Ma, X. H. Yang, Fuyuan Wu, Yan Zhao Ke, Shi Jia Chen, and Zhe Yi Ge
- Subjects
Electron density ,Materials science ,Backscatter ,Physics::Optics ,Steady State theory ,Plasma ,Condensed Matter Physics ,Laser ,Atomic and Molecular Physics, and Optics ,law.invention ,Brillouin zone ,Physics::Plasma Physics ,law ,Irradiation ,Stimulated raman ,Electrical and Electronic Engineering ,Atomic physics - Abstract
A one-dimensional steady-state model for stimulated Raman backscatter (SRS) and stimulated Brillouin backscatter (SBS) processes in laser-irradiated plasmas is presented. Based on a novel “predictor-corrector” method, the model is capable to deal with broadband scattered light and inhomogeneous plasmas, exhibiting robustness and high efficiency. Influences of the electron density and temperature on the linear gains of both SRS and SBS are investigated, which indicates that the SRS gain is more sensitive to the electron density and temperature than that of the SBS. For the low-density case, the SBS dominates the scattering process, while the SRS exhibits much higher reflectivity in the high-density case. The nonlinear saturation mechanisms and competition between SRS and SBS are included in our model by a phenomenological method. The typical anti-correlation between SRS and SBS versus electron density is reproduced in the model. Calculations of the reflectivities are qualitatively in agreement with the typical results of experiments and simulations.
- Published
- 2020
3. Above-100 MeV proton beam generation from near-critical-density plasmas irradiated by moderate Laguerre–Gaussian laser pulses
- Author
-
Yan-Ting Hu, Yue Cao, Jie Zhao, Guo-Bo Zhang, Ke Liu, Li-Xiang Hu, and Tong-Pu Yu
- Subjects
Nuclear Energy and Engineering ,Condensed Matter Physics - Abstract
High-quality protons have many potential applications in tumor therapy, proton radiography, fast ignition and nuclear physics. Over recent decades, significant progress has been made in generating such proton beams with lasers. However, it is still challenging to achieve a compact proton beam with an energy of hundreds of MeV under the laser intensities currently available. Here, we propose a novel scheme to produce above-100 MeV protons in nonuniform near-critical-density (NCD) plasmas driven by a Laguerre–Gaussian (LG) laser pulse. When a linearly-polarized LG laser pulse with the intensity of ∼1020 W cm−2 enters the NCD plasmas with a trapezoidal density profile, a donut-like double-channel structure with an electron column on the axis is produced behind the laser pulse, together with a unique, strong magnetic field. At the end of the density plateau, the magnetic field begins to expand in both longitudinal and transverse directions. The magnetic pressure force displaces the electrons with regard to the protons, resulting in a quasi-static electric field E x S . This electrostatic field can remain robust and be sustaintained for a long time since the magnetic field decreases very slowly, i.e. E x S ∝ ▽ B z 2 . Thus, the protons can be accelerated by the longitudinal electrostatic field and confined by the generated transverse focusing field. Three dimensional particle-in-cell simulations confirmed that a well-defined above-100 MeV proton beam with a cut-off energy at least 3.5 times larger than that of the normal Gaussian laser could be obtained, making the proton beams a potential source for tumor therapy in the future.
- Published
- 2022
4. Radiation effects of electrons on multilayer FePS3 studied with laser plasma accelerator
- Author
-
Meng Peng, Jun-Bo Yang, Hao Chen, Bo-Yuan Li, Xu-Lei Ge, Xiao-Hu Yang, Guo-Bo Zhang, and Yan-Yun Ma
- Subjects
General Physics and Astronomy - Abstract
Space radiation with inherently broadband spectral flux poses a huge danger to astronauts and electronics on aircraft, but it is hard to simulate such feature with conventional radiation sources. Using a tabletop laser-plasma accelerator, we can reproduce exponential energy particle beams as similar as possible to these in space radiation. We used such an electron beam to study the electron radiation effects on the surface structure and performance of two-dimensional material (FePS3). Energetic electron beam led to bulk sample cleavage and damage between areas of uneven thickness. For the FePS3 sheet sample, electron radiation transformed it from crystalline state to amorphous state, causing the sample surface to rough. The full widths at the half maximum of characteristic Raman peaks became larger, and the intensities of characteristic Raman peaks became weak or even disappeared dramatically under electron radiation. This trend became more obvious for thinner samples, and this phenomenon was attributed to the cleavage of P–P and P–S bonds, destabilizing the bipyramid structure of [P2S6]4– unit. The results are of great significance for testing the maximum allowable radiation dose for the two-dimensional material, implying that FePS3 cannot withstand such energetic electron radiation without an essential shield.
- Published
- 2022
5. Enhancement of the conversion efficiency of soft x-ray by colliding gold plasmas
- Author
-
P. F. Zheng, M. Zi, Y. Y. Ma, S. Kawata, X. H. Yang, Wenpeng Wang, Guo-Bo Zhang, Y. Yuan, Y. Z. Ke, Y. Cui, F. Y. Wu, B. H. Xu, and S. J. Chen
- Subjects
Physics ,Opacity ,Physics::Instrumentation and Detectors ,Astrophysics::High Energy Astrophysical Phenomena ,Energy conversion efficiency ,Plasma ,Radiation ,Condensed Matter Physics ,Laser ,Instability ,law.invention ,Physics::Plasma Physics ,law ,Atomic physics ,Inertial confinement fusion ,FOIL method - Abstract
A new scheme is proposed to enhance the conversion efficiency (CE) of soft x-rays (0.1–1.5 keV) generated by irradiating a double-gold-foil target using double laser pulses to collide gold plasmas. A detailed analysis of the hydrodynamic evolution of the colliding plasmas is performed by using one-dimensional radiation hydrodynamic simulations. The results show that the total soft x-ray CE can be enhanced up to 71.5% by setting the foil thickness as d1 = 0.3 μm, and this is 14.5% higher than that for a single laser irradiating a single-gold-foil target. Most of the enhanced soft x-ray CEs are generated from a stagnation layer formed by plasma collisions. Such a scheme is simple and practical, which is beneficial for their applications in astrophysical opacity calculations, inertial confinement fusion, and hydrodynamic instability analyses.
- Published
- 2021
6. Electrothermal effects on high-gain magnetized liner inertial fusion
- Author
-
Yan-Yun Ma, Fuyuan Wu, X. H. Yang, Rafael Ramis, Shijia Chen, Guo-Bo Zhang, Yun Yuan, and Ye Cui
- Subjects
Resistive touchscreen ,Materials science ,Magnetized Liner Inertial Fusion ,Mechanics ,Fusion power ,Condensed Matter Physics ,Magnetic field ,symbols.namesake ,Temperature gradient ,Nuclear Energy and Engineering ,Thermal ,symbols ,Nernst equation ,Magnetohydrodynamics - Abstract
High-gain magnetized liner inertial fusion (MagLIF) is a possible way to realize fusion. To investigate electrothermal effects on the transport of magnetic flux and thermal flux in MagLIF, this study has developed a resistive magnetohydrodynamics (MHD) module including an axial magnetic field using the code MULTI-IFE. MagLIF driven by a peak current of 60 MA releases 1080 MJ of fusion energy for a 1-cm-long liner, corresponding to an energy gain of approximately 180. The magnetic field is decompressed by electrothermal effects owing to the great temperature gradient in the fuel. This papers shows that a Nernst flux limiter of between 0.1 and 0.3 prevents the Nernst velocity from significantly decompressing the axial magnetic field and achieving a relative high yield. Compared with that of a simple gas target, the magnetic flux loss in the high-gain MagLIF target can be reduced from 70% to 30% owing to the magnetic insulation in the cryogenic deuterium-tritium. Most of the cryogenic DT layer in a high-gain MagLIF target is burned, resulting in a significant increase in the fusion yield.
- Published
- 2021
7. Optimization of the beam quality in ionization injection by a tailoring gas profile*
- Author
-
Li-Xiang Hu, Yan-Yun Ma, X. H. Yang, Ming Zi, Jing-Qi Yang, Jia-Yin Mu, Jie Zhou, Hai-Bo Yao, Li-Chao Tian, Guo-Bo Zhang, and Ye Cui
- Subjects
Materials science ,business.industry ,General Physics and Astronomy ,Laser ,law.invention ,Acceleration ,Quality (physics) ,Optics ,law ,Ionization ,Cathode ray ,Physics::Accelerator Physics ,Laser beam quality ,business ,Energy (signal processing) ,Beam (structure) - Abstract
A new scheme is proposed to improve the electron beam quality of ionization-induced injection by tailoring gas profile in laser wakefield acceleration. Two-dimensional particle-in-cell simulations show that the ionization-induced injection mainly occurs in high-density stage and automatically truncates in low-density stage due to the decrease of wakefield potential difference. The beam loading can be compensated by the elongated beam resulting from the density transition stage. The beam quality can be improved by shorter injection distance and beam loading effect. A quasi-monoenergetic electron beam with a central energy of 258 MeV and an energy spread of 5.1% is obtained under certain laser-plasma conditions.
- Published
- 2021
8. Transport of fast electron beam in mirror-field magnetized solid-density plasma
- Author
-
Y. Y. Ma, Li-Xiang Hu, Yibing Cao, M. Y. Yu, X. H. Yang, Heng Xu, Tong-Pu Yu, Guo-Bo Zhang, and Y. Lang
- Subjects
Physics ,Magnetic mirror ,Field (physics) ,Reflection (physics) ,Cathode ray ,Electron ,Plasma ,Atomic physics ,Condensed Matter Physics ,Electromagnetic induction ,Magnetic field - Abstract
In experiments on the effect of magnetic field on electron transportation in laser–plasma interaction, the magnetic field is often produced by two coils and is mirror-like. In this paper, the transport and the reflection of fast electron beam generated in laser–plasma interaction in solid-density plasma immersed in a mirror magnetic field are studied using particle-in-cell simulation. The helicoidal motion of fast electrons in the field and the convergence of magnetic induction lines leads to the collimated transport and focusing of the fast electrons. The reflection of the fast electrons can lead to the decrease in the transmission ratio, and this reflection increases with the magnetic mirror ratio, but saturates at a certain level.
- Published
- 2021
9. Generation and stopping of laser-driven two-component ion beam
- Author
-
Tong-Pu Yu, Jinqing Yu, X. H. Yang, Fu-Qiu Shao, Xiangrui Jiang, Guo-Bo Zhang, De-Bin Zou, Li-Xiang Hu, H. X. Deng, Wei-Quan Wang, and Na Zhao
- Subjects
Physics ,Ion beam ,Bragg peak ,Condensed Matter Physics ,law.invention ,Ion ,Ignition system ,Physics::Plasma Physics ,law ,Fusion ignition ,Stopping power (particle radiation) ,Atomic physics ,Penetration depth ,Beam (structure) - Abstract
The generation and stopping of a laser-driven two-component ion beam are investigated by three-dimensional particle-in-cell simulation and an extended stopping model. It is found that a two-component ion beam with the tunable composition ratio can be obtained from the two-species-ions sandwich target interacting with a relativistic laser pulse. When the generated proton beam mixed with a certain portion of carbon ions is transporting in fully ionized dense plasma, the beam stopping power is significantly enhanced compared to a pure proton beam. The maximum penetration depth is sharply reduced, and the Bragg peak with a higher magnitude appears earlier at the end of their paths, which is beneficial for achieving more localized energy deposition. The effect of heavy ion mixing on proton beam driven fast ignition is also discussed. A simple theoretical model is established, indicating that the required ignition time is relatively delayed for a heavy-ion doping case. For a small hot-spot size, it is possible to achieve the fusion ignition for a low mixed ratio. However, it is difficult to maintain a high fuel temperature due to the growing energy loss originating from mechanical work and thermal conduction.
- Published
- 2021
10. Hundreds-GeV Au ion generation by 1022–24 W cm−2 laser pulses interacting with high-Z grain doped gas
- Author
-
Sizhong Wu, Na Zhao, Li-Xiang Hu, Xiangrui Jiang, Taiwu Huang, Guo-Bo Zhang, Yan Yin, Tong-Pu Yu, Cangtao Zhou, Fu-Qiu Shao, Hongbin Zhuo, Hua Zhang, Ke Liu, Mingyang Yu, and De-Bin Zou
- Subjects
Materials science ,Nuclear Energy and Engineering ,law ,Doping ,Plasma ,Atomic physics ,Condensed Matter Physics ,Laser ,Ion ,law.invention - Abstract
Collision of intermediate-energy heavy ions is an important way to investigate the state of high-density nuclear matter and formation of quark gluon plasmas. In this paper, we demonstrate from two-dimensional particle-in-cell simulations that hundreds-GeV Au79+ ions can be generated by ultrashort ∼1022–24 W cm−2 lasers interacting with high-Z grain doped gas. Under extremely intense laser field, strong γ-ray radiation has resulted in massive laser energy loss, and the invoked radiation reaction trapping of electrons weakens the heavy ion acceleration. However, due to hole-boring acceleration and multi-body expansion acceleration of high-Z grains, the energy conversion efficiency from laser to heavy ions is still up to 32%. Our results might provide an effective routine to carry out the experimental explorations of heavy-ion collisions by using hundreds-petawatt laser facilities.
- Published
- 2021
11. Betatron radiation polarization control by using an off-axis ionization injection in a laser wakefield acceleration
- Author
-
Min Chen, Tong-Pu Yu, X. H. Yang, Feng Liu, De-Bin Zou, Fu-Qiu Shao, Yan-Yun Ma, Suming Weng, Zheng-Ming Sheng, and Guo-Bo Zhang
- Subjects
Physics ,business.industry ,Physics::Optics ,Synchrotron radiation ,02 engineering and technology ,Plasma ,Electron ,Radiation ,021001 nanoscience & nanotechnology ,Laser ,Betatron ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,law.invention ,Pulse (physics) ,010309 optics ,Optics ,law ,Ionization ,0103 physical sciences ,Physics::Accelerator Physics ,0210 nano-technology ,business ,QC - Abstract
Tunable X-ray sources from a laser-driven wakefield have wide applications. However, due to the difficulty of electron dynamics control, currently the tunability of laser wakefield–based X-ray sources is still difficult. By using three-dimensional particle-in-cell simulations, we propose a scheme to realize controllable electron dynamics and X-ray radiation. In the scheme, a long wavelength drive pulse excites a plasma wake and an off-axis laser pulse with a short wavelength co-propagates with the drive pulse and ionizes the K-shell electrons of the background high-Z gas. The electrons can be injected in the wakefield with controllable transverse positions and residual momenta. These injected electrons experience controllable oscillations in the wake, leading to tunable radiations both in intensity and polarization.
- Published
- 2020
12. Generation of high-energy-density collimated electron-positron beam by a linear polarized laser-plasma interaction from a cone
- Author
-
Peng Han, Fei Shan, Yun Yuan, Y. Q. Ma, Long Ma, Li-Chao Tian, Jing Jiang, Xiaoxiao Li, Ye Cui, X. H. Yang, and Guo-Bo Zhang
- Subjects
Physics ,History ,Astrophysics::High Energy Astrophysical Phenomena ,Electron ,Plasma ,Ponderomotive force ,Laser ,Collimated light ,Computer Science Applications ,Education ,law.invention ,Transverse plane ,Acceleration ,Positron ,Physics::Plasma Physics ,law ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Atomic physics - Abstract
Electron-positron plasma has attracted much attention recently due to their unique properties. In this paper, we study the acceleration of electron-positron plasma in a cone by using PIC method. The electrons and positrons will be scattered by transverse ponderomotive force during the interaction between laser and electron-positron plasma. A new scheme is proposed to obtain high-energy dense collimated electron-positron plasma by a hollow gold cone. Transverse scattered electrons and positrons are pinched in the gold cone. Both electrons and positrons can be accelerated by ponderomotive force continuously and a dense collimated electron-positron plasma is produced. The energy of electrons and positrons obtained in the cone is much higher than the upper limit of electron energy obtained by ponderomotive force acceleration. The high quality electron and positron beam has great potential value in further research.
- Published
- 2020
13. Tunable proton stopping power of deuterium-tritium by mixing heavy ion dopants for fast ignition
- Author
-
Li-Xiang Hu, Tong-Pu Yu, X.H. Yang, Guo-Bo Zhang, J. M. Ouyang, De-Bin Zou, Wei-Quan Wang, Fu-Qiu Shao, and H. B. Zhuo
- Subjects
Nuclear and High Energy Physics ,Radiation ,Materials science ,Proton ,Bragg peak ,Plasma ,Penetration (firestop) ,Thermal conduction ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Ignition system ,Minimum ignition energy ,Deuterium ,Physics::Plasma Physics ,law ,0103 physical sciences ,Atomic physics ,010306 general physics - Abstract
The theoretical model of charged-particle stopping power for the Coulomb logarithm lnΛb ≥ 2 plasma [Phys. Rev. Lett., 20, 3059 (1993)] is extended to investigate the transport of the energetic protons in a compressed deuterium-tritium (DT) pellet mixed with heavy ion dopants. It shows that an increase of mixed-ion charge state and density ratio results in the substantial enhancement of the proton stopping power, which leads to a shorter penetration distance and an earlier appearance of the Bragg peak with a higher magnitude. The effect of hot-spot mix on the proton-driven fast ignition model is discussed. It is found that ignition time required for a small mixed hot-spot can be significantly reduced with slightly increased beam energy. Nevertheless, the ignition cannot maintain for a long time due to increasing alpha-particle penetration distance and energy loss from mechanical work and thermal conduction at high temperatures.
- Published
- 2016
14. Energetic deuterium-ion beams and neutron source driven by multiple-laser interaction with pitcher-catcher target
- Author
-
Tong-Pu Yu, Mingyang Yu, Li-Xiang Hu, Cangtao Zhou, Taiwu Huang, Xiangrui Jiang, Hongbin Zhuo, De-Bin Zou, Xiaoyang Guo, Sizhong Wu, Yan Yin, Guo-Bo Zhang, Fu-Qiu Shao, and H. Zhang
- Subjects
Nuclear and High Energy Physics ,Materials science ,Monte Carlo method ,Energy conversion efficiency ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Ion ,Deuterium ,law ,0103 physical sciences ,Neutron source ,Nuclear fusion ,Neutron ,Atomic physics ,010306 general physics - Abstract
Multiple lasers interacting with a deuterated (D) pitcher-catcher target and neutron generation are investigated using two-dimensional hybrid particle-in-cell and Monte Carlo simulations. It is found that when multiple laser pulses are focused on the front surface of the pitcher layer, D+ ion acceleration by target normal sheath acceleration (TNSA) is enhanced by the interfering overlapped light fields and the resulting periodic target-surface structure. With three laser pulses each of 4.5×1019 W/cm2 intensity, 33 fs duration and ~160 mJ energy, focusing at suitable angles on the pitcher layer, one can obtain 15 MeV D+ ions and ~25% laser-to-D+ ions energy conversion efficiency. As the resulting high-energy-density D+ ions bombard the catcher layer, D-D fusion reactions are triggered. About 3.6×107 neutrons can be produced, with the maximum neutron production rate as high as 3.1×1036 m-3s-1, almost an order of magnitude higher than that from a single laser of the same total energy.
- Published
- 2020
15. Generation of energetic ring-shaped ion beam from relativistic Laguerre–Gaussian laser pulse interacting with micro-structure targets
- Author
-
Yan Yin, Heng Zhou, Hao Zhang, Ke Liu, Wei-Quan Wang, Fu-Qiu Shao, Tong-Pu Yu, Li-Xiang Hu, X. R. Xu, H. B. Zhuo, Guo-Bo Zhang, and De-Bin Zou
- Subjects
Physics ,Ion beam ,Energy conversion efficiency ,Electron ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,Ion ,Pulse (physics) ,law.invention ,Planar ,law ,0103 physical sciences ,Energy transformation ,Atomic physics ,010306 general physics - Abstract
By using three-dimensional particle-in-cell simulations, we demonstrate that an energetic ring-shaped ion beam can be generated by an ultra-intense circularly polarized Laguerre–Gaussian laser pulse interacting with micro-structure targets. The electron and ion dynamics of three different targets including a sleeve–wire target, wire target, and common planar target are investigated. It is found that an optimized sleeve–wire target can provide a remarkable increase in the maximum ion energy and laser-to-ion energy conversion efficiency. The reason can be attributed to the matched transverse profiles between the electric-field distribution of Laguerre–Gaussian laser and sleeve–wire structure, resulting in efficient laser-target energy coupling. In fact, using a laser pulse of intensity 2.74 × 1 0 20 W/cm2, duration 66.7 fs, and energy ∼1 J, one can obtain ∼35 MeV protons, ∼5.8 MeV/u carbon ions, and ∼15% laser-to-ion energy conversion.
- Published
- 2020
16. Acceleration and radiation of externally injected electrons in laser plasma wakefield driven by a Laguerre-Gaussian pulse
- Author
-
Xiaohui Yuan, Suming Weng, Zheng-Ming Sheng, Zhong-Chen Shen, Min Chen, Ji Luo, Guo-Bo Zhang, and Feng Liu
- Subjects
Physics ,QC717 ,General Physics and Astronomy ,Near and far field ,Electron ,Plasma ,Radiation ,Betatron ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Acceleration ,law ,0103 physical sciences ,Cathode ray ,Physics::Accelerator Physics ,Atomic physics ,010306 general physics - Abstract
By using three-dimensional particle-in-cell simulations, externally injected electron beam acceleration and radiation in donut-like wake fields driven by a Laguerre–Gaussian pulse are investigated. Studies show that in the acceleration process the total charge and azimuthal momenta of electrons can be stably maintained at a distance of a few hundreds of micrometers. Electrons experience low-frequency spiral rotation and high-frequency betatron oscillation, which leads to a synchrotron-like radiation. The radiation spectrum is mainly determined by the betatron motion of electrons. The far field distribution of radiation intensity shows axial symmetry due to the uniform transverse injection and spiral rotation of electrons. Our studies suggest a new way to simultaneously generate hollow electron beam and radiation source from a compact laser plasma accelerator.
- Published
- 2017
17. Directional enhancement of selected high-order-harmonics from intense laser irradiated blazed grating targets
- Author
-
Fu-Qiu Shao, Zheng-Ming Sheng, Suming Weng, Y. Q. Ma, Jun Zheng, Feng Liu, Min Chen, Jie Zhang, Xiaohui Yuan, and Guo-Bo Zhang
- Subjects
Materials science ,business.industry ,Physics::Optics ,Plasma ,Grating ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Spectral line ,010305 fluids & plasmas ,law.invention ,QC350 ,Optics ,law ,Harmonics ,0103 physical sciences ,Blazed grating ,010306 general physics ,business ,Ultrashort pulse ,Radiant intensity - Abstract
Relativistically intense laser solid target interaction has been proved to be a promising way to generate high-order harmonics, which can be used to diagnose ultrafast phenomena. However, their emission direction and spectra still lack tunability. Based upon two-dimensional particle-in-cell simulations, we show that directional enhancement of selected high-order-harmonics can be realized using blazed grating targets. Such targets can select harmonics with frequencies being integer times of the grating frequency. Meanwhile, the radiation intensity and emission area of the harmonics are increased. The emission direction is controlled by tailoring the local blazed structure. Theoretical and electron dynamics analysis for harmonics generation, selection and directional enhancement from the interaction between multi-cycle laser and grating target are carried out. These studies will benefit the generation and application of laser plasma-based high order harmonics.
- Published
- 2017
18. Beam quality improvement of ionization injected electrons by using chirped pulse in wakefield acceleration
- Author
-
Yan-Yun Ma, Jian-Xun Liu, Li-Chao Tian, Z. Y. Ge, Guo-Bo Zhang, Fu-Qiu Shao, Ye Cui, X. H. Yang, De-Bin Zou, Min Chen, and Long-Fei Gan
- Subjects
Physics ,business.industry ,Physics::Optics ,Electron ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Pulse (physics) ,Acceleration ,Optics ,Nuclear Energy and Engineering ,law ,Ionization ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,Cathode ray ,Chirp ,Physics::Accelerator Physics ,Physics::Atomic Physics ,Laser beam quality ,010306 general physics ,business - Abstract
Ionization-induced electron injection in a chirped laser pulse driven wakefield acceleration is investigated through particle-in-cell simulations. We find that negative (positive) chirp can longitudinally stretch (compress) laser pulse, and the wakefield amplitude can be enhanced regardless of the chirp sign. On the other hand, the rapid compression of a positively chirped pulse leads to the decrease of the wakefield potential difference, which breaks the ionization injection condition and consequent injection truncation occurs. The effective injection only lasts for a few hundred micrometers and the detailed injection length is determined by the chirp parameter. As a result, a highly tunable quasi-monoenergetic electron beam with narrow energy spread, hundreds of MeV central energy and tens of pC charge can be stably produced by this scheme.
- Published
- 2019
19. Tens GeV positron generation and acceleration in a compact plasma channel
- Author
-
Liang-Qiang Cao, Jun Zhao, Tong-Pu Yu, Jian-Xun Liu, Shi Qu, Liang Ma, Yan-Yun Ma, Fu-Qiu Shao, Guo-Bo Zhang, and Yuan Zhao
- Subjects
Physics ,Electron density ,Antiparticle ,Astrophysics::High Energy Astrophysical Phenomena ,Plasma ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Nuclear physics ,Acceleration ,Positron ,Nuclear Energy and Engineering ,law ,Antimatter ,0103 physical sciences ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Plasma channel ,010306 general physics - Abstract
We propose a compact scheme for high-density and high-energy positron generation. In the scheme, the generation, compression and acceleration of positrons are encompassed in a plasma channel irradiated by an ultra intense laser. In about 20 μm, positrons are accelerated with their energy beyond 20 GeV, and are compressed with a maximal density of 4.1n c . The obtained positron beam with a wave-like density profile is accelerated via the direct laser acceleration.
- Published
- 2019
20. Dynamics of the interaction of relativistic Laguerre–Gaussian laser pulses with a wire target
- Author
-
Li-Xiang Hu, Z. Y. Ge, Fu-Qiu Shao, De-Bin Zou, Guo-Bo Zhang, Hao Zhang, Yu Lu, Tong-Pu Yu, and Yan Yin
- Subjects
Physics ,Angular momentum ,Gaussian ,Dynamics (mechanics) ,Plasma ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,symbols.namesake ,Nuclear Energy and Engineering ,law ,Quantum electrodynamics ,Electric field ,0103 physical sciences ,symbols ,Laguerre polynomials ,010306 general physics - Published
- 2018
21. High-flux positrons generation via two counter-propagating laser pulses irradiating near-critical-density plasmas
- Author
-
Jun Zhao, Fu-Qiu Shao, X. H. Yang, Tong-Pu Yu, Xin-ping Wang, Y. Q. Ma, Yuan Zhao, Jian-Xun Liu, Jian-zhou Quan, and Guo-Bo Zhang
- Subjects
Physics ,Near critical ,Astrophysics::High Energy Astrophysical Phenomena ,Photon radiation ,Plasma ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Computational physics ,High flux ,Positron ,law ,0103 physical sciences ,Physics::Accelerator Physics ,High Energy Physics::Experiment ,Current (fluid) ,010306 general physics ,Intensity (heat transfer) - Abstract
A scheme for generating high-flux positrons by two counter-propagating laser pulses colliding in near-critical-density plasmas is proposed, which might be realized with current laser facilities. Positrons of number 2.79 × 105 and with a maximum density of 9.63 × 1024 m−3 can be generated for a laser with an intensity of 1022 W cm−2. This is attributed to the increase in the cross sections for photon radiation and positron generation in the colliding scheme. In order to improve the positron generation, the relevant parameters are discussed in detail. This scheme will facilitate the observation of the Breit-Wheeler positrons in the laboratory.
- Published
- 2018
22. Acceleration and evolution of a hollow electron beam in wakefields driven by a Laguerre-Gaussian laser pulse
- Author
-
Suming Weng, Yan-Yun Ma, Carl Schroeder, Tong-Pu Yu, Eric Esarey, Zheng-Ming Sheng, Ming Zeng, Min Chen, Lu-Le Yu, Feiyu Li, Ji Luo, and Guo Bo Zhang
- Subjects
Physics ,Beam diameter ,Ion beam ,business.industry ,Physics::Optics ,Condensed Matter Physics ,Plasma acceleration ,Laser ,01 natural sciences ,Beam parameter product ,010305 fluids & plasmas ,law.invention ,Optics ,Physics::Plasma Physics ,law ,0103 physical sciences ,Physics::Accelerator Physics ,Relativistic electron beam ,Laser beam quality ,Atomic physics ,010306 general physics ,business ,Beam (structure) ,QC - Abstract
We show that a ring-shaped hollow electron beam can be injected and accelerated by using a Laguerre-Gaussian laser pulse and ionization-induced injection in a laser wakefield accelerator. The acceleration and evolution of such a hollow, relativistic electron beam are investigated through three-dimensional particle-in-cell simulations. We find that both the ring size and the beam thickness oscillate during the acceleration. The beam azimuthal shape is angularly dependent and evolves during the acceleration. The beam ellipticity changes resulting from the electron angular momenta obtained from the drive laser pulse and the focusing forces from the wakefield. The dependence of beam ring radius on the laser-plasma parameters (e.g., laser intensity, focal size, and plasma density) is studied. Such a hollow electron beam may have potential applications for accelerating and collimating positively charged particles.
- Published
- 2016
23. $$D_{sJ}(2860)$$ D s J ( 2860 ) from the semileptonic decays of $$B_s$$ B s mesons
- Author
-
Jian-Rong Zhang, Jian-Xun Liu, Yan-Yun Ma, Guo-Bo Zhang, Ming-Qiu Huang, Hongbin Zhuo, Long-Fei Gan, and Qing-Jun Zhu
- Subjects
Quantum chromodynamics ,Physics ,Particle physics ,Physics and Astronomy (miscellaneous) ,Meson ,Excited state ,High Energy Physics::Phenomenology ,Heavy quark effective theory ,High Energy Physics::Experiment ,Sum rule in quantum mechanics ,Ground state ,Engineering (miscellaneous) - Abstract
In the framework of heavy quark effective theory, the leading order Isgur-Wise form factors relevant to semileptonic decays of the ground state $\bar{b}s$ meson $B_{s}$ into orbitally excited $D$-wave $\bar{c}s$ mesons, including the newly observed narrow $D^{*}_{s1}(2860)$ and $D^{*}_{s3}(2860)$ states by the LHCb Collaboration, are calculated with the QCD sum rule method. With these universal form factors, the decay rates and branching ratios are estimated. We find that the decay widths are $\Gamma(B_s\rightarrow D^{*}_{s1}\ell\bar{\nu}) =1.25^{+0.80}_{-0.60}\times10^{-19} \mbox{GeV}$, $\Gamma(B_s\rightarrow D^{'}_{s2}\ell\bar{\nu}) =1.49^{+0.97}_{-0.73}\times10^{-19} \mbox{GeV}$, $\Gamma(B_s\rightarrow D_{s2}\ell\bar{\nu}) =4.48^{+1.05}_{-0.94}\times10^{-17} \mbox{GeV}$, and $\Gamma(B_s\rightarrow D^{*}_{s3}\ell\bar{\nu}) = 1.52^{+0.35}_{-0.31}\times10^{-16} \mbox{GeV}$. The corresponding branching ratios are $\mathcal {B}(B_s\rightarrow D^{*}_{s1}\ell\bar{\nu}) =2.85^{+1.82}_{-1.36}\times 10^{-7}$, $\mathcal {B}(B_s\rightarrow D^{'}_{s2}\ell\bar{\nu}) =3.40^{+2.21}_{-1.66}\times 10^{-7}$, $\mathcal {B}(B_{s}\rightarrow D_{s2}\ell\bar{\nu}) =1.02^{+0.24}_{-0.21}\times 10^{-4}$, and $\mathcal {B}(B_s\rightarrow D^{*}_{s3}\ell\bar{\nu}) = 3.46^{+0.80}_{-0.70}\times 10^{-4}$. The decay widths and branching ratios of corresponding $B^{*}_{s}$ semileptonic processes are also predicted.
- Published
- 2015
24. Dense pair plasma generation by two laser pulses colliding in a cylinder channel
- Author
-
Guo-Bo Zhang, Shigeo Kawata, Tong-Pu Yu, Han-Zhen Li, Hongbin Zhuo, Jun Zhao, Y. Q. Ma, De-Bin Zou, Jian-Xun Liu, Yuan Zhao, Xiaohu Yang, Fu-Qiu Shao, and Jingkang Yang (杨靖康)
- Subjects
Physics ,Photon ,General Physics and Astronomy ,Plasma ,Electron ,Laser ,01 natural sciences ,010305 fluids & plasmas ,Cylinder (engine) ,law.invention ,Pair production ,law ,Antimatter ,0103 physical sciences ,Atomic physics ,010306 general physics ,Lepton - Published
- 2017
25. Influence of laser contrast on high-order harmonic generation from solid-density plasma surfaces
- Author
-
Wenqing Wei, Jie Zhang, Feng Liu, Xulei Ge, Yanqing Deng, Su Yang, Xiaohui Yuan, Yuan Fang, Guo-Bo Zhang, Jian Gao, Min Chen, and Zheng-Ming Sheng
- Subjects
QC717 ,Materials science ,business.industry ,media_common.quotation_subject ,Plasma ,Laser ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,010305 fluids & plasmas ,Electronic, Optical and Magnetic Materials ,law.invention ,Optics ,Physics::Plasma Physics ,law ,Harmonics ,Electric field ,0103 physical sciences ,Contrast (vision) ,High harmonic generation ,Irradiation ,Electrical and Electronic Engineering ,010306 general physics ,business ,Order of magnitude ,media_common - Abstract
The influence of laser temporal contrast on high-order harmonic generation from intense laser interactions with solid-density plasma surfaces is experimentally studied. A switchable plasma mirror system is set up to improve the contrast by two orders of magnitude at 10 ps prior to the main peak. By using the plasma mirror and tuning the prepulse, the dependence of high-order harmonic generation on laser contrast is investigated. Harmonics up to the 21st order via the mechanism of coherent wake emission are observed only when the targets are irradiated by high contrast laser pulses by applying the plasma mirror.
- Published
- 2017
26. High-energy-density electron beam generation in ultra intense laser-plasma interaction
- Author
-
Long-Fei Gan, Fu-Qiu Shao, Yuan Zhao, Xiaohu Yang, Jingkang Yang (杨靖康), Y. Q. Ma, Tong-Pu Yu, Guo-Bo Zhang, Jian-Xun Liu, Hongbin Zhuo, and Jun Zhao
- Subjects
Physics ,Ion beam ,business.industry ,Plasma ,Condensed Matter Physics ,Laser ,Kinetic energy ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Optics ,law ,0103 physical sciences ,Cathode ray ,Physics::Accelerator Physics ,High harmonic generation ,Laser beam quality ,Atomic physics ,010306 general physics ,business ,Beam divergence - Abstract
By using a two-dimensional particle-in-cell simulation, we demonstrate a scheme for high-energy-density electron beam generation by irradiating an ultra intense laser pulse onto an aluminum (Al) target. With the laser having a peak intensity of 4 × 1023 W cm−2, a high quality electron beam with a maximum density of 117nc and a kinetic energy density up to 8.79 × 1018 J m−3 is generated. The temperature of the electron beam can be 416 MeV, and the beam divergence is only 7.25°. As the laser peak intensity increases (e.g., 1024 W cm−2), both the beam energy density (3.56 × 1019 J m−3) and the temperature (545 MeV) are increased, and the beam collimation is well controlled. The maximum density of the electron beam can even reach 180nc. Such beams should have potential applications in the areas of antiparticle generation, laboratory astrophysics, etc.
- Published
- 2016
27. Enhanced electron–positron pair production by ultra intense laser irradiating a compound target
- Author
-
Guo-Bo Zhang, X. H. Yang, Jian-Xun Liu, Jun Zhao, Tong-Pu Yu, Yuan Zhao, Long-Fei Gan, Jin-Jin Liu, Y. Q. Ma, Fu-Qiu Shao, Shigeo Kawata, Hongbin Zhuo, and Shi-Jie Zhang
- Subjects
Physics ,Antiparticle ,Photon ,Electron bubble ,business.industry ,Plasma ,Electron ,Condensed Matter Physics ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Pair production ,Positron ,Optics ,Nuclear Energy and Engineering ,law ,0103 physical sciences ,Physics::Accelerator Physics ,Atomic physics ,010306 general physics ,business - Abstract
High-energy-density electron–positron pairs play an increasingly important role in many potential applications. Here, we propose a scheme for enhanced positron production by an ultra intense laser irradiating a gas-Al compound target via the multi-photon Breit–Wheeler (BW) process. The laser pulse first ionizes the gas and interacts with a near-critical-density plasma, forming an electron bubble behind the laser pulse. A great deal of electrons are trapped and accelerated in the bubble, while the laser front hole-bores the Al target and deforms its front surface. A part of the laser wave is thus reflected by the inner curved target surface and collides with the accelerated electron bunch. Finally, a large number of γ photons are emitted in the forward direction via the Compton back-scattering process and the BW process is initiated. Dense electron–positron pairs are produced with a maximum density of m−3. Simulation results show that the positron generation is greatly enhanced in the compound target, where the positron yield is two orders of magnitude greater than that in only the solid slab case. The influences of the laser intensity, gas density and length on the positron beam quality are also discussed, which demonstrates the feasibility of the scheme in practice.
- Published
- 2016
28. Dynamics of boundary layer electrons around a laser wakefield bubble
- Author
-
Suming Weng, T. Yuan, Eric Esarey, J.-Y. Yu, Min Chen, Lu-Le Yu, Ji Luo, Guo-Bo Zhang, Z.-C. Shen, and Carl Schroeder
- Subjects
Physics ,Electron ,Wake ,Condensed Matter Physics ,Plasma acceleration ,Laser ,01 natural sciences ,010305 fluids & plasmas ,law.invention ,Pulse (physics) ,Boundary layer ,law ,Bow wave ,0103 physical sciences ,Electromagnetic electron wave ,Atomic physics ,010306 general physics - Abstract
The dynamics of electrons forming the boundary layer of a highly nonlinear laser wakefield driven in the so called bubble or blowout regime is investigated using particle-in-cell simulations. It is shown that when the driver pulse intensity increases or the focal spot size decreases, a significant amount of electrons initially pushed by the laser pulse can detach from the bubble structure at its tail, middle, or front and form particular classes of waves locally with high densities, referred to as the tail wave, lateral wave, and bow wave. The tail wave and bow wave correspond to real electron trajectories, while the lateral wave does not. The detached electrons can be ejected transversely, containing considerable energy, and reducing the efficiency of the laser wakefield accelerator. Some of the transversely emitted electrons may obtain MeV level energy. These electrons can be used for wake evolution diagnosis and producing high frequency radiation.
- Published
- 2016
29. Laser Wakefield Acceleration Using Mid-Infrared Laser Pulses
- Author
-
Zheng-Ming Sheng, Y. Q. Ma, Liejia Qian, Nasr A. M. Hafz, Fu-Qiu Shao, and Guo-Bo Zhang
- Subjects
Physics ,Active laser medium ,business.industry ,General Physics and Astronomy ,Laser pumping ,Injection seeder ,Laser ,01 natural sciences ,Beam parameter product ,010305 fluids & plasmas ,Round-trip gain ,law.invention ,Optics ,law ,0103 physical sciences ,Laser beam quality ,Laser power scaling ,010306 general physics ,business - Abstract
We study a laser wakefield acceleration driven by mid-infrared (mid-IR) laser pulses through two-dimensional particle-in-cell simulations. Since a mid-IR laser pulse can deliver a larger ponderomotive force as compared with the usual 0.8 μm wavelength laser pulse, it is found that electron self-injection into the wake wave occurs at an earlier time, the plasma density threshold for injection becomes lower, and the electron beam charge is substantially enhanced. Meanwhile, our study also shows that quasimonoenergetic electron beams with a narrow energy-spread can be generated by using mid-IR laser pulses. Such a mid-IR laser pulse can provide a feasible method for obtaining a high quality and high charge electron beam. Therefore, the current efforts on constructing mid-IR terawatt laser systems can greatly benefit the laser wakefield acceleration research.
- Published
- 2016
30. Acceleration of on-axis and ring-shaped electron beams in wakefields driven by Laguerre-Gaussian pulses
- Author
-
Guo Bo Zhang, Zheng-Ming Sheng, Lu Le Yu, Tong-Pu Yu, Ming Zeng, Ji Ye Yu, Suming Weng, T. Yuan, Min Chen, Ji Luo, and Yan Yun Ma
- Subjects
Physics ,General Physics and Astronomy ,Electron ,Laser ,Plasma acceleration ,01 natural sciences ,Collimated light ,010305 fluids & plasmas ,law.invention ,Acceleration ,Transverse plane ,Positron ,Physics::Plasma Physics ,law ,0103 physical sciences ,Cathode ray ,Physics::Accelerator Physics ,Atomic physics ,010306 general physics ,QC - Abstract
The acceleration of electron beams with multiple transverse structures in wakefields driven by Laguerre-Gaussian pulses has been studied through three-dimensional (3D) particle-in-cell simulations. Under different laser-plasma conditions, the wakefield shows different transverse structures. In general cases, the wakefield shows a donut-like structure and it accelerates the ring-shaped hollow electron beam. When a lower plasma density or a smaller laser spot size is used, besides the donut-like wakefield, a central bell-like wakefield can also be excited. The wake sets in the center of the donut-like wake. In this case, both a central on-axis electron beam and a ring-shaped electron beam are simultaneously accelerated. Further, reducing the plasma density or laser spot size leads to an on-axis electron beam acceleration only. The research is beneficial for some potential applications requiring special pulse beam structures, such as positron acceleration and collimation.
- Published
- 2016
31. High-flux low-divergence positron beam generation from ultra-intense laser irradiated a tapered hollow target
- Author
-
Hongbin Zhuo, Tong-Pu Yu, Guo-Bo Zhang, X. H. Yang, Shigeo Kawata, Jin-Jin Liu, Y. Q. Ma, Jian-Feng Yan, Jun Zhao, Jian-Xun Liu, Long-Fei Gan, and Yuan Zhao
- Subjects
Physics ,business.industry ,Flux ,Condensed Matter Physics ,Laser ,Beam parameter product ,law.invention ,Positron ,Optics ,Orders of magnitude (time) ,law ,Electric field ,Physics::Accelerator Physics ,Laser beam quality ,Atomic physics ,business ,Intensity (heat transfer) - Abstract
By using two-dimensional particle-in-cell simulations, we demonstrate high-flux dense positrons generation by irradiating an ultra-intense laser pulse onto a tapered hollow target. By using a laser with an intensity of 4 × 1023 W/cm2, it is shown that the Breit-Wheeler process dominates the positron production during the laser-target interaction and a positron beam with a total number >1015 is obtained, which is increased by five orders of magnitude than in the previous work at the same laser intensity. Due to the focusing effect of the transverse electric fields formed in the hollow cone wall, the divergence angle of the positron beam effectively decreases to ∼15° with an effective temperature of ∼674 MeV. When the laser intensity is doubled, both the positron flux (>1016) and temperature (963 MeV) increase, while the divergence angle gets smaller (∼13°). The obtained high-flux low-divergence positron beam may have diverse applications in science, medicine, and engineering.
- Published
- 2015
32. [Prevention and treatment of deep vein thrombosis after pelvic fractures]
- Author
-
Yi-Zhen, Zhang, Huai-Wei, Gao, Guo-Bo, Zhang, and Mao-Ru, Liu
- Subjects
Adult ,Aged, 80 and over ,Male ,Radiography ,Venous Thrombosis ,Fractures, Bone ,Young Adult ,Humans ,Heparin, Low-Molecular-Weight ,Middle Aged ,Pelvic Bones ,Aged - Published
- 2010
33. Enhanced electron injection in laser-driven bubble acceleration by ultra-intense laser irradiating foil-gas targets
- Author
-
Min Chen, Tong-Pu Yu, Jian-Xun Liu, Guo-Bo Zhang, Yan Yin, Y. Q. Ma, Nasr A. M. Hafz, Fu-Qiu Shao, Shigeo Kawata, Long-Fei Gan, Li-Chao Tian, Xiaohu Yang, Jian-Feng Yan, De-Bin Zou, H. Xu, and Hongbin Zhuo
- Subjects
Physics ,business.industry ,Bubble ,Plasma ,Electron ,Condensed Matter Physics ,Laser ,law.invention ,Acceleration ,Optics ,Positron ,law ,Cathode ray ,Physics::Accelerator Physics ,Atomic physics ,business ,FOIL method - Abstract
A scheme for enhancing the electron injection charge in a laser-driven bubble acceleration is proposed. In this scheme, a thin foil target is placed in front of a gas target. Upon interaction with an ultra-intense laser pulse, the foil emits electrons with large longitudinal momenta, allowing them to be trapped into the transmitted shaped laser-excited bubble in the gaseous plasma target. Two-dimensional particle-in-cell simulation is used to demonstrate this scheme, and an electron beam with a total electron number of 4.21×108 μm−1 can be produced, which is twice the number of electrons produced without the foil. Such scheme may be widely used for applications that require high electron yields such as positron and gamma ray generation from relativistic electron beams interacting with solid targets.
- Published
- 2015
34. High-energy-density electron jet generation from an opening gold cone filled with near-critical-density plasma
- Author
-
W.D. Yu, Fu-Qiu Shao, Jiangwei Liu, Xipeng Li, Shixia Luan, J. M. Ouyang, W. Q. Wang, A. Y. Wong, De-Bin Zou, Tong-Pu Yu, Guo-Bo Zhang, Jinchang Wang, and Z. Y. Ge
- Subjects
Physics ,Electron density ,Jet (fluid) ,Relativistic plasma ,law ,General Physics and Astronomy ,Electron ,Plasma ,Ponderomotive force ,Atomic physics ,Laser ,Electromagnetic radiation ,law.invention - Abstract
By using two-dimensional particle-in-cell simulations, we propose a scheme for strong coupling of a petawatt laser with an opening gold cone filled with near-critical-density plasmas. When relevant parameters are properly chosen, most laser energy can be fully deposited inside the cone with only 10% leaving the tip opening. Due to the asymmetric ponderomotive acceleration by the strongly decayed laser pulse, high-energy-density electrons with net laser energy gain are accumulated inside the cone, which then stream out of the tip opening continuously, like a jet. The jet electrons are fully relativistic, with speeds around 0.98−0.998 c and densities at 1020/cm3 level. The jet can keep for a long time over 200 fs, which may have diverse applications in practice.
- Published
- 2015
35. Laser shaping of a relativistic circularly polarized pulse by laser foil interaction
- Author
-
Guo-Bo Zhang, Fu-Qiu Shao, P. Wang, Yan Yin, Y. Y. Ma, H. B. Zhuo, Xiaohu Yang, De-Bin Zou, Z. Y. Ge, J. M. Ouyang, and Tong-Pu Yu
- Subjects
Femtosecond pulse shaping ,Physics ,Distributed feedback laser ,business.industry ,Condensed Matter Physics ,Laser ,Pulse (physics) ,law.invention ,Optics ,Multiphoton intrapulse interference phase scan ,Relativistic plasma ,law ,Ultrafast laser spectroscopy ,Laser power scaling ,Atomic physics ,business - Abstract
Laser shaping of a relativistic circularly polarized laser pulse in ultra-intense laser thin-foil interaction is investigated by theoretical analysis and particle-in-cell simulations. It is found that the plasma foil as a nonlinear optical shutter has an obvious cut-out effect on the laser temporal and spatial profiles. Two-dimensional particle-in-cell simulations show that the high intensity part of a Gaussian laser pulse can be well extracted from the whole pulse. The transmitted pulse with longitudinal steep rise front and transverse super-Gaussian profile is thus obtained which would be beneficial for the radiation pressure acceleration regime. The Rayleigh-Taylor-like instability is observed in the simulations, which destroys the foil and results in the cut-out effect of the pulse in the rise front of a circularly polarized laser.
- Published
- 2013
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.