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Publisher: Cambridge University Press   (Total: 387 journals)

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 High Power Laser Science and EngineeringJournal Prestige (SJR): 0.901 Citation Impact (citeScore): 3Number of Followers: 3     Open Access journal ISSN (Print) 2095-4719 - ISSN (Online) 2052-3289 Published by Cambridge University Press  [387 journals]
• Deep-learning-based phase control method for tiled aperture coherent beam
combining systems

• Authors: Tianyue Hou; Yi An, Qi Chang, Pengfei Ma, Jun Li, Dong Zhi, Liangjin Huang, Rongtao Su, Jian Wu, Yanxing Ma, Pu Zhou
Abstract: We incorporate deep learning (DL) into tiled aperture coherent beam combining (CBC) systems for the first time, to the best of our knowledge. By using a well-trained convolutional neural network DL model, which has been constructed at a non-focal-plane to avoid the data collision problem, the relative phase of each beamlet could be accurately estimated, and then the phase error in the CBC system could be compensated directly by a servo phase control system. The feasibility and extensibility of the phase control method have been demonstrated by simulating the coherent combining of different hexagonal arrays. This DL-based phase control method offers a new way of eliminating dynamic phase noise in tiled aperture CBC systems, and it could provide a valuable reference on alleviating the long-standing problem that the phase control bandwidth decreases as the number of array elements increases.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.46
Issue No: Vol. 7 (2019)

• Burst behavior due to the quasimode excited by stimulated Brillouin
scattering in high-intensity laser–plasma interactions

• Authors: Q. S. Feng; L. H. Cao, Z. J. Liu, C. Y. Zheng, X. T. He
Abstract: The strong-coupling mode, called the “quasimode”, is excited by stimulated Brillouin scattering (SBS) in high-intensity laser–plasma interactions. Also SBS of the quasimode competes with SBS of the fast mode (or slow mode) in multi-ion species plasmas, thus leading to a low-frequency burst behavior of SBS reflectivity. Competition between the quasimode and the ion-acoustic wave (IAW) is an important saturation mechanism of SBS in high-intensity laser–plasma interactions. These results give a clear explanation of the low-frequency periodic burst behavior of SBS and should be considered as a saturation mechanism of SBS in high-intensity laser–plasma interactions.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.44
Issue No: Vol. 7 (2019)

• Monoenergetic proton beam accelerated by single reflection mechanism only
during hole-boring stage – ERRATUM

• Authors: Wenpeng Wang; Cheng Jiang, Shasha Li, Hao Dong, Baifei Shen, Yuxin Leng, Ruxin Li, Zhizhan Xu
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.42
Issue No: Vol. 7 (2019)

• Review on TNSA diagnostics and recent developments at SPARC_LAB

• Authors: Fabrizio Bisesto; Mario Galletti, Maria Pia Anania, Massimo Ferrario, Riccardo Pompili, Mordechai Botton, Elad Schleifer, Arie Zigler
Abstract: Interaction between high-intensity lasers with solid targets is the key process in a wide range of novel laser-based particle accelerator schemes, as well as electromagnetic radiation sources. Common to all the processes is the generation of femtosecond pulses of relativistic electrons emitted from the targets as forerunners of the later-time principal products of the interaction scheme. In this paper, some diagnostics employed in laser–solid matter interaction experiments related to electrons, protons, ions, electromagnetic pulses (EMPs) and X-rays are reviewed. Then, we present our experimental study regarding fast electrons and EMPs utilizing a femtosecond-resolution detector previously adopted only in accelerator facilities.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.41
Issue No: Vol. 7 (2019)

• Petawatt and exawatt class lasers worldwide

• Authors: Colin N. Danson; Constantin Haefner, Jake Bromage, Thomas Butcher, Jean-Christophe F. Chanteloup, Enam A. Chowdhury, Almantas Galvanauskas, Leonida A. Gizzi, Joachim Hein, David I. Hillier, Nicholas W. Hopps, Yoshiaki Kato, Efim A. Khazanov, Ryosuke Kodama, Georg Korn, Ruxin Li, Yutong Li, Jens Limpert, Jingui Ma, Chang Hee Nam, David Neely, Dimitrios Papadopoulos, Rory R. Penman, Liejia Qian, Jorge J. Rocca, Andrey A. Shaykin, Craig W. Siders, Christopher Spindloe, Sándor Szatmári, Raoul M. G. M. Trines, Jianqiang Zhu, Ping Zhu, Jonathan D. Zuegel
Abstract: In the 2015 review paper ‘Petawatt Class Lasers Worldwide’ a comprehensive overview of the current status of high-power facilities of ${>}200~\text{TW}$ was presented. This was largely based on facility specifications, with some description of their uses, for instance in fundamental ultra-high-intensity interactions, secondary source generation, and inertial confinement fusion (ICF). With the 2018 Nobel Prize in Physics being awarded to Professors Donna Strickland and Gerard Mourou for the development of the technique of chirped pulse amplification (CPA), which made these lasers possible, we celebrate by providing a comprehensive update of the current status of ultra-high-power lasers and demonstrate how the technology has developed. We are now in the era of multi-petawatt facilities coming online, with 100 PW lasers being proposed and even under construction. In addition to this there is a pull towards development of industrial and multi-disciplinary applications, which demands much higher repetition rates, delivering high-average powers with higher efficiencies and the use of alternative wavelengths: mid-IR facilities. So apart from a comprehensive update of the current global status, we want to look at what technologies are to be deployed to get to these new regimes, and some of the critical issues facing their development.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.36
Issue No: Vol. 7 (2019)

• Monoenergetic proton beam accelerated by single reflection mechanism only
during hole-boring stage

• Authors: Wenping Wang; Cheng Jiang, Shasha Li, Hao Dong, Baifei Shen, Yuxin Leng, Ruxin Li, Zhizhan Xu
Abstract: Multidimensional instabilities always develop with time during the process of radiation pressure acceleration, and are detrimental to the generation of monoenergetic proton beams. In this paper, a sharp-front laser is proposed to irradiate a triple-layer target (the proton layer is set between two carbon ion layers) and studied in theory and simulations. It is found that the thin proton layer can be accelerated once to hundreds of MeV with monoenergetic spectra only during the hole-boring (HB) stage. The carbon ions move behind the proton layer in the light-sail (LS) stage, which can shield any further interaction between the rear part of the laser and the proton layer. In this way, proton beam instabilities can be reduced to a certain extent during the entire acceleration process. It is hoped such a mechanism can provide a feasible way to improve the beam quality for proton therapy and other applications.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.40
Issue No: Vol. 7 (2019)

• ++++++++ ++++++++ ++++++++++++ ++++++++++++++++${\geqslant}$ ++++++++++++ ++++++++ +++++kHz)+targets+and+optics+from+liquid+microjets+for+high-intensity+laser–plasma+interactions&rft.title=High+Power+Laser+Science+and+Engineering&rft.issn=2095-4719&rft.date=2019&rft.volume=7&rft.aulast=George&rft.aufirst=K.&rft.au=K.+M.+George&rft.au=J.+T.+Morrison,+S.+Feister,+G.+K.+Ngirmang,+J.+R.+Smith,+A.+J.+Klim,+J.+Snyder,+D.+Austin,+W.+Erbsen,+K.+D.+Frische,+J.+Nees,+C.+Orban,+E.+A.+Chowdhury,+W.+M.+Roquemore&rft_id=info:doi/10.1017/hpl.2019.35">High-repetition-rate ( ${\geqslant}$ kHz) targets and optics from liquid
microjets for high-intensity laser–plasma interactions

• Authors: K. M. George; J. T. Morrison, S. Feister, G. K. Ngirmang, J. R. Smith, A. J. Klim, J. Snyder, D. Austin, W. Erbsen, K. D. Frische, J. Nees, C. Orban, E. A. Chowdhury, W. M. Roquemore
Abstract: High-intensity laser–plasma interactions produce a wide array of energetic particles and beams with promising applications. Unfortunately, the high repetition rate and high average power requirements for many applications are not satisfied by the lasers, optics, targets, and diagnostics currently employed. Here, we aim to address the need for high-repetition-rate targets and optics through the use of liquids. A novel nozzle assembly is used to generate high-velocity, laminar-flowing liquid microjets which are compatible with a low-vacuum environment, generate little to no debris, and exhibit precise positional and dimensional tolerances. Jets, droplets, submicron-thick sheets, and other exotic configurations are characterized with pump–probe shadowgraphy to evaluate their use as targets. To demonstrate a high-repetition-rate, consumable, liquid optical element, we present a plasma mirror created by a submicron-thick liquid sheet. This plasma mirror provides etalon-like anti-reflection properties in the low field of 0.1% and high reflectivity as a plasma, 69%, at a repetition rate of 1 kHz. Practical considerations of fluid compatibility, in-vacuum operation, and estimates of maximum repetition rate are addressed. The targets and optics presented here demonstrate a potential technique for enabling the operation of laser–plasma interactions at high repetition rates.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.35
Issue No: Vol. 7 (2019)

• Time evolution of stimulated Raman scattering and two-plasmon decay at
laser intensities relevant for shock ignition in a hot plasma

• Authors: G. Cristoforetti; L. Antonelli, D. Mancelli, S. Atzeni, F. Baffigi, F. Barbato, D. Batani, G. Boutoux, F. D’Amato, J. Dostal, R. Dudzak, E. Filippov, Y. J. Gu, L. Juha, O. Klimo, M. Krus, S. Malko, A. S. Martynenko, Ph. Nicolai, V. Ospina, S. Pikuz, O. Renner, J. Santos, V. T. Tikhonchuk, J. Trela, S. Viciani, L. Volpe, S. Weber, L. A. Gizzi
Abstract: Laser–plasma interaction (LPI) at intensities $10^{15}{-}10^{16}~\text{W}\cdot \text{cm}^{-2}$ is dominated by parametric instabilities which can be responsible for a significant amount of non-collisional absorption and generate large fluxes of high-energy nonthermal electrons. Such a regime is of paramount importance for inertial confinement fusion (ICF) and in particular for the shock ignition scheme. In this paper we report on an experiment carried out at the Prague Asterix Laser System (PALS) facility to investigate the extent and time history of stimulated Raman scattering (SRS) and two-plasmon decay (TPD) instabilities, driven by the interaction of an infrared laser pulse at an intensity ${\sim}1.2\times 10^{16}~\text{W}\cdot \text{cm}^{-2}$ with a ${\sim}100~\unicode[STIX]{x03BC}\text{m}$ scalelength plasma produced from irradiation of a flat plastic target. The laser pulse duration (300 ps) and the high value of plasma temperature ( ${\sim}4~\text{keV}$ ) expected from hydrodynamic simulations make these results interesting for a deeper understanding of LPI in shock ignition conditions. Experimental results show that absolute TPD/SRS, driven at a quarter of the critical density, and convective SRS, driven at lower plasma densities, are well separated in time, with absolute instabilities driven at early times of interaction and convective backward SRS emerging at the laser peak and persisting all over the tail of the pulse. Side-scattering SRS, driven at low plasma densities, is also clearly observed. Experimental results are compared to fully kinetic large-scale, two-dimensional simulations. Particle-in-cell results, beyond reproducing the framework delineated by the experimental measurements, reveal the importance of filamentation instability in ruling the onset of SRS and stimulated Brillouin scattering instabilities and confirm the crucial role of collisionless absorption in the LPI energy balance.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.37
Issue No: Vol. 7 (2019)

• Passive optimization of pump noise transfer function by narrow band-pass
filtering in femtosecond fiber lasers

• Authors: Peng Qin; Sijia Wang, Minglie Hu, Youjian Song
Abstract: Fluctuation of pump power is one of the major sources of temporal and intensity noise in femtosecond fiber lasers. In this work, the transfer functions between the relative intensity noise (RIN) of the pump laser diode (LD) and the output RIN, between the RIN of the pump LD and timing jitter of femtosecond fiber lasers are systematically studied. It is demonstrated, for the first time to our knowledge, that the amplitude of the pump RIN transfer function can be effectively decreased by an intra-cavity narrow band-pass filter. In particular, for normal-dispersion lasers, the 3-dB bandwidth of the transfer function can also be narrowed by two-thirds, with a steeper falling edge. Furthermore, with the narrow band-pass filtering, the transfer function is almost independent of the net intra-cavity dispersion due to amplifier similariton formation. The proposed scheme can effectively isolate the pump-induced noise without the need of complex active pump LD control and intra-cavity dispersion management, thus providing an easy way for practical high-power, high-stability femtosecond fiber laser design and related high-precision applications outside the laboratory.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.38
Issue No: Vol. 7 (2019)

• Single-shot electrons and protons time-resolved detection from
high-intensity laser–solid matter interactions at SPARC_LAB

• Authors: F. Bisesto; M. Galletti, M. P. Anania, M. Ferrario, R. Pompili, M. Botton, A. Zigler, F. Consoli, M. Salvadori, P. Andreoli, C. Verona
Abstract: Laser–plasma interactions have been studied in detail over the past twenty years, as they show great potential for the next generation of particle accelerators. The interaction between an ultra-intense laser and a solid-state target produces a huge amount of particles: electrons and photons (X-rays and $\unicode[STIX]{x03B3}$ -rays) at early stages of the process, with protons and ions following them. At SPARC_LAB Test Facility we have set up two diagnostic lines to perform simultaneous temporally resolved measurements on both electrons and protons.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.39
Issue No: Vol. 7 (2019)

• An online diagnosis technique for simultaneous measurement of the
fundamental, second and third harmonics in one snapshot

• Authors: Xue Dong; Xingchen Pan, Cheng Liu, Jianqiang Zhu
Abstract: A three-wavelength coherent-modulation-imaging (CMI) technique is proposed to simultaneously measure the fundamental, second and third harmonics of a laser driver in one snapshot. Laser beams at three wavelengths (1053 nm, 526.5 nm and 351 nm) were simultaneously incident on a random phase plate to generate hybrid diffraction patterns, and a modified CMI algorithm was adopted to reconstruct the complex amplitude of each wavelength from one diffraction intensity frame. The validity of this proposed technique was verified using both numerical simulation and experimental analyses. Compared to commonly used measurement methods, this proposed method has several advantages, including a compact structure, convenient operation and high accuracy.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.26
Issue No: Vol. 7 (2019)

• Calibration and verification of streaked optical pyrometer system used for
laser-induced shock experiments

• Authors: Zhiyu He; Guo Jia, Fan Zhang, Xiuguang Huang, Zhiheng Fang, Jiaqing Dong, Hua Shu, Junjian Ye, Zhiyong Xie, Yuchun Tu, Qili Zhang, Erfu Guo, Wenbing Pei, Sizu Fu
Abstract: Although the streaked optical pyrometer (SOP) system has been widely adopted in shock temperature measurements, its reliability has always been of concern. Here, two calibrated Planckian radiators with different color temperatures were used to calibrate and verify the SOP system by comparing the two calibration standards using both multi-channel and single-channel methods. A high-color-temperature standard lamp and a multi-channel filter were specifically designed for the measurement system. To verify the reliability of the SOP system, the relative deviation between the measured data and the standard value of less than 5% was calibrated out, which demonstrates the reliability of the SOP system. Furthermore, a method to analyze the uncertainty and sensitivity of the SOP system is proposed. A series of laser-induced shock experiments were conducted at the ‘Shenguang-II’ laser facility to verify the reliability of the SOP system for temperature measurements at tens of thousands of kelvin. The measured temperature of the quartz in our experiments agreed fairly well with previous works, which serves as evidence for the reliability of the SOP system.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.27
Issue No: Vol. 7 (2019)

• Environmentally stable Er-fiber mode-locked pulse generation and
amplification by spectrally filtered and phase-biased nonlinear amplifying
long-loop mirror

• Authors: Zhengru Guo; Qiang Hao, Junsong Peng, Heping Zeng
Abstract: We report on environmentally stable long-cavity ultrashort erbium-doped fiber lasers, which self-start mode-locking at quite low thresholds by using spectrally filtered and phase-biased nonlinear amplifying long-loop mirrors. By employing 100-m polarization-maintaining fiber (PMF) in the nonlinear loop, the fundamental repetition rate reaches 1.84 MHz and no practical limitation is found to further decrease the repetition rate. The filter used in the long loop not only suppresses Kelly sidebands of the solitons, but also eliminates the amplified spontaneous emission which exists widely in low-repetition-rate ultrafast fiber lasers. The bandwidth of the filter is optimized by using a numerical model. The laser emits approximately 3-ps pulses with an energy of 17.4 pJ, which is further boosted to $1.5~\unicode[STIX]{x03BC}\text{J}$ by using a fiber amplifier.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.29
Issue No: Vol. 7 (2019)

• Rapid growth and properties of large-aperture 98%-deuterated DKDP crystals

• Authors: Xumin Cai; Xiuqing Lin, Guohui Li, Junye Lu, Ziyu Hu, Guozong Zheng
Abstract: In this paper, a highly deuterated potassium dihydrogen phosphate (DKDP) crystal with sizes up to $318~\text{mm}\times 312~\text{mm}\times 265~\text{mm}$ was grown by the rapid-growth method. The synthesis tank device was specially designed to synthesize a higher deuterium concentration and high-purity DKDP solution. The deuterium content of the as-grown crystal, which was 97.9%, was determined by two methods, including infrared (IR) spectroscopy and thermo-gravimetric analysis (TGA) measurements. The performances of the 97.9% DKDP crystal, including transmission, absorption coefficient, and laser-induced damage threshold (LIDT) were measured. The results indicate that, in the near-infrared band, the transmission of the 97.9% DKDP crystal is higher than that of KDP and 70% DKDP crystals, and the absorption coefficient is lower. The LIDT of the crystal reached $23.2~\text{J}\cdot \text{cm}^{-2}$ (R-on-1, 1064 nm, 3 ns), which meets the engineering requirements for use in optical applications.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.24
Issue No: Vol. 7 (2019)

• Simulation and analysis of the time evolution of laser power and
temperature in static pulsed XPALs

• Authors: Chenyi Su; Binglin Shen, Xingqi Xu, Chunsheng Xia, Bailiang Pan
Abstract: A theoretical model is established to describe the thermal dynamics and laser kinetics in a static pulsed exciplex pumped Cs–Ar laser (XPAL). The temporal behaviors of both the laser output power and temperature rise in XPALs with a long-time pulse and multi-pulse operation modes are calculated and analyzed. In the case of long-time pulse pumping, the results show that the initial laser power increases with a rise in the initial operating temperature, but the laser power decreases quickly due to heat accumulation. In the case of multi-pulse operation, simulation results show that the optimal laser output power can be obtained by appropriately increasing the initial temperature and reducing the thermal relaxation time.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.28
Issue No: Vol. 7 (2019)

• Effect of rear surface fields on hot, refluxing and escaping electron
populations via numerical simulations

• Authors: D. R. Rusby; C. D. Armstrong, G. G. Scott, M. King, P. McKenna, D. Neely
Abstract: After a population of laser-driven hot electrons traverses a limited thickness solid target, these electrons will encounter the rear surface, creating TV/m fields that heavily influence the subsequent hot-electron propagation. Electrons that fail to overcome the electrostatic potential reflux back into the target. Those electrons that do overcome the field will escape the target. Here, using the particle-in-cell (PIC) code EPOCH and particle tracking of a large population of macro-particles, we investigate the refluxing and escaping electron populations, as well as the magnitude, spatial and temporal evolution of the rear surface electrostatic fields. The temperature of both the escaping and refluxing electrons is reduced by 30%–50% when compared to the initial hot-electron temperature as a function of intensity between $10^{19}$ and $10^{21}~~\text{W}/\text{cm}^{2}$ . Using particle tracking we conclude that the highest energy internal hot electrons are guaranteed to escape up to a threshold energy, below which only a small fraction are able to escape the target. We also examine the temporal characteristic of energy changes of the refluxing and escaping electrons and show that the majority of the energy change is as a result of the temporally evolving electric field that forms on the rear surface.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.34
Issue No: Vol. 7 (2019)

• Amplification of 200-ps high-intensity laser pulses via frequency matching
stimulated Brillouin scattering

• Authors: Hang Yuan; Yulei Wang, Qiang Yuan, Dongxia Hu, Can Cui, Zhaohong Liu, Sensen Li, Yi Chen, Feng Jing, Zhiwei Lü
Abstract: Laser pulses of 200 ps with extremely high intensities and high energies are sufficient to satisfy the demand of shock ignition, which is an alternative path to ignition in inertial confinement fusion (ICF). This paper reports a type of Brillouin scheme to obtain high-intensity 200-ps laser pulses, where the pulse durations are a challenge for conventional pulsed laser amplification systems. In the amplification process, excited Brillouin acoustic waves fulfill the nonlinear optical effect through which the high energy of a long pump pulse is entirely transferred to a 200-ps laser pulse. This method was introduced and achieved within the SG-III prototype system in China. Compared favorably with the intensity of $2~\text{GW}/\text{cm}^{2}$ in existing ICF laser drivers, a 6.96- $\text{GW}/\text{cm}^{2}$ pulse with a width of 170 ps was obtained in our experiment. The practical scalability of the results to larger ICF laser drivers is discussed.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.31
Issue No: Vol. 7 (2019)

• ++++++++ ++++++++ ++++++++++++ ++++++++++++++++$\text{Yb}^{3+}$ ++++++++++++ ++++++++ ++++-based+laser+amplifiers&rft.title=High+Power+Laser+Science+and+Engineering&rft.issn=2095-4719&rft.date=2019&rft.volume=7&rft.aulast=Tamer&rft.aufirst=Issa&rft.au=Issa+Tamer&rft.au=Sebastian+Keppler,+Jörg+Körner,+Marco+Hornung,+Marco+Hellwing,+Frank+Schorcht,+Joachim+Hein,+Malte+C.+Kaluza&rft_id=info:doi/10.1017/hpl.2019.32">Modeling of the 3D spatio-temporal thermal profile of joule-class
$\text{Yb}^{3+}$ -based laser amplifiers

• Authors: Issa Tamer; Sebastian Keppler, Jörg Körner, Marco Hornung, Marco Hellwing, Frank Schorcht, Joachim Hein, Malte C. Kaluza
Abstract: Thermal profile modification of an active material in a laser amplifier via optical pumping results in a change in the material’s refractive index, and causes thermal expansion and stress, eventually leading to spatial phase aberrations, or even permanent material damage. For this purpose, knowledge of the 3D spatio-temporal thermal profile, which can currently only be retrieved via numerical simulations, is critical for joule-class laser amplifiers to reveal potentially dangerous thermal features within the pumped active materials. In this investigation, a detailed, spatio-temporal numerical simulation was constructed and tested for accuracy against surface thermal measurements of various end-pumped $\text{Yb}^{3+}$ -doped laser-active materials. The measurements and simulations show an excellent agreement and the model was successfully applied to a joule-class $\text{Yb}^{3+}$ -based amplifier currently operating in the POLARIS laser system at the Friedrich-Schiller-University and Helmholtz-Institute Jena in Germany.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.32
Issue No: Vol. 7 (2019)

• Selective generation of individual Raman Stokes lines using dissipative
soliton resonance pulses

• Authors: He Xu; Sheng-Ping Chen, Zong-Fu Jiang
Abstract: Pumped by rectangular-shaped dissipative soliton resonance (DSR) pulses at 1030 nm, selective excitations of Raman Stokes lines of up to third order with extinction ratios of 8 dB and fifth order with extinction ratios of 4 dB are demonstrated experimentally. The rectangular DSR pulses are generated from a dual-amplifier ytterbium-doped figure-of-eight mode-locked laser constructed using all $10~\unicode[STIX]{x03BC}\text{m}$ -core-diameter large-mode-area fibers. By varying the two pump powers, the peak power of the output DSR pulses can be continuously tuned from 10 W to 100 W and from 30 W to 200 W, respectively, for two different lengths of the nonlinear amplifying loop mirror inside the cavity. High-frequency components are found to correspond to parts of the pulse in the trailing edge when two bandpass filters are used to separate the propagated pulse. Consequently, it provides an all-fiber technique to achieve selective excitation of the Raman shift by adjusting the peak power of the DSR pulse.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.33
Issue No: Vol. 7 (2019)

• A demonstration of extracting the strength and wavelength of the magnetic
field generated by the Weibel instability from proton radiography

• Authors: Bao Du; Hong-Bo Cai, Wen-Shuai Zhang, Shi-Yang Zou, Jing Chen, Shao-Ping Zhu
Abstract: The Weibel instability and the induced magnetic field are of great importance for both astrophysics and inertial confinement fusion. Because of the stochasticity of this magnetic field, its main wavelength and mean strength, which are key characteristics of the Weibel instability, are still unobtainable experimentally. In this paper, a theoretical model based on the autocorrelation tensor shows that in proton radiography of the Weibel-instability-induced magnetic field, the proton flux density on the detection plane can be related to the energy spectrum of the magnetic field. It allows us to extract the main wavelength and mean strength of the two-dimensionally isotropic and stochastic magnetic field directly from proton radiography for the first time. Numerical calculations are conducted to verify our theory and show good consistency between pre-set values and the results extracted from proton radiography.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.30
Issue No: Vol. 7 (2019)

• Collective absorption of laser radiation in plasma
at sub-relativistic intensities

• Authors: Y. J. Gu; O. Klimo, Ph. Nicolaï, S. Shekhanov, S. Weber, V. T. Tikhonchuk
Abstract: Processes of laser energy absorption and electron heating in an expanding plasma in the range of irradiances $I\unicode[STIX]{x1D706}^{2}=10^{15}{-}10^{16}~\text{W}\,\cdot \,\unicode[STIX]{x03BC}\text{m}^{2}/\text{cm}^{2}$ are studied with the aid of kinetic simulations. The results show a strong reflection due to stimulated Brillouin scattering and a significant collisionless absorption related to stimulated Raman scattering near and below the quarter critical density. Also presented are parametric decay instability and resonant excitation of plasma waves near the critical density. All these processes result in the excitation of high-amplitude electron plasma waves and electron acceleration. The spectrum of scattered radiation is significantly modified by secondary parametric processes, which provide information on the spatial localization of nonlinear absorption and hot electron characteristics. The considered domain of laser and plasma parameters is relevant for the shock ignition scheme of inertial confinement fusion.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.25
Issue No: Vol. 7 (2019)

• ARCTURUS laser: a versatile high-contrast, high-power multi-beam laser
system

• Authors: M. Cerchez; R. Prasad, B. Aurand, A. L. Giesecke, S. Spickermann, S. Brauckmann, E. Aktan, M. Swantusch, M. Toncian, T. Toncian, O. Willi
Abstract: With the latest configuration, the Ti:Sa laser system ARCTURUS (Düsseldorf University, Germany) operates with a double-chirped pulse amplification (CPA) architecture delivering pulses with an energy of 7 J before compression in each of the two high-power beams. By the implementation of a plasma mirror system, the intrinsic laser contrast is enhanced up to $10^{-12}$ on a time scale of hundreds of picoseconds, before the main peak. The laser system has been used in various configurations for advanced experiments and different studies have been carried out employing the high-power laser beams as a single, high-intensity interaction beam ( $I\approx 10^{20}~\text{W}/\text{cm}^{2}$ ), in dual- and multi-beam configurations or in a pump–probe arrangement.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2019.21
Issue No: Vol. 7 (2019)

• Advanced fuel layering in line-moving, high-gain direct-drive cryogenic
targets

• Authors: I. V. Aleksandrova; E. R. Koresheva
Abstract: In inertial fusion energy (IFE) research, a number of technological issues have focused on the ability to inexpensively fabricate large quantities of free-standing targets (FSTs) by developing a specialized layering module with repeatable operation. Of central importance for the progress towards plasma generation with intense thermonuclear reactions is the fuel structure, which must be isotropic to ensure that fusion will take place. In this report, the results of modeling the FST layering time, $\unicode[STIX]{x1D70F}_{\text{Form}}$ , are presented for targets which are shells of ${\sim}4~\text{mm}$ in diameter with a wall made from compact and porous polymers. The layer thickness is ${\sim}200~\unicode[STIX]{x03BC}\text{m}$ for pure solid fuel and ${\sim}250~\unicode[STIX]{x03BC}\text{m}$ for in-porous solid fuel. Computation shows $\unicode[STIX]{x1D70F}_{\text{Form}} PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.23 Issue No: Vol. 7 (2019) • Enhancement of the surface emission at the fundamental frequency and the transmitted high-order harmonics by pre-structured targets • Authors: K. Q. Pan; D. Yang, L. Guo, Z. C. Li, S. W. Li, C. Y. Zheng, S. E. Jiang, B. H. Zhang, X. T. He Abstract: Laser interaction with an ultra-thin pre-structured target is investigated with the help of both two-dimensional and three-dimensional particle-in-cell simulations. With the existence of a periodic structure on the target surface, the laser seems to penetrate through the target at its fundamental frequency even if the plasma density of the target is much higher than the laser’s relativistically critical density. The particle-in-cell simulations show that the transmitted laser energy behind the pre-structured target is increased by about two orders of magnitude compared to that behind the flat target. Theoretical analyses show that the transmitted energy behind the pre-structured target is actually re-emitted by electron ‘islands’ formed by the surface plasma waves on the target surfaces. In other words, the radiation with the fundamental frequency is actually ‘surface emission’ on the target rear surface. Besides the intensity of the component with the fundamental frequency, the intensity of the high-order harmonics behind the pre-structured target is also much enhanced compared to that behind the flat target. The enhancement of the high-order harmonics is also related to the surface plasma waves generated on the target surfaces. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.20 Issue No: Vol. 7 (2019) • FM-to-AM conversion in angular filtering based on transmitted volume Bragg gratings • Authors: Fan Gao; Baoxing Xiong, Xiang Zhang, Xiao Yuan Abstract: FM-to-AM conversion for angular filtering based on transmitted volume Bragg gratings (TBGs) is discussed. Simulation results show that a narrower spectral selectivity of TBGs led to stronger FM-to-AM conversion. Good angular selectivity and a wide bandwidth for the TBGs can be obtained by controlling the grating period and thickness. FM-to-AM conversion can be effectively suppressed and the distortion criterion for the filtered beam reduces to less than 5%. FM-to-AM conversion of TBGs is demonstrated in the ‘Shenguang’ facility, and the results are in good agreement with the simulation. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.22 Issue No: Vol. 7 (2019) • 4+crystal&rft.title=High+Power+Laser+Science+and+Engineering&rft.issn=2095-4719&rft.date=2019&rft.volume=7&rft.aulast=Guo&rft.aufirst=Jie&rft.au=Jie+Guo&rft.au=Wei+Wang,+Hua+Lin,+Xiaoyan+Liang&rft_id=info:doi/10.1017/hpl.2019.16">High-repetition-rate and high-power picosecond regenerative amplifier based on a single bulk Nd:GdVO4 crystal • Authors: Jie Guo; Wei Wang, Hua Lin, Xiaoyan Liang Abstract: We report on a high-repetition-rate, high-power continuously pumped Nd:GdVO4 regenerative amplifier. Numerical simulations successfully pinpoint the optimum working point free of bifurcation instability with simultaneous efficient energy extraction. At a repetition rate of 100 kHz, a maximum output power of 23 W was obtained with a pulse duration of 27 ps, corresponding to a pulse energy of$230~\unicode[STIX]{x03BC}\text{J}$. The system displayed an outstanding stability with a root mean square power noise as low as 0.3%. The geometry of the optical resonator and the pumping scheme enhanced output power in the$\text{TEM}_{00}$mode with a single bulk crystal. Accordingly, nearly diffraction-limited beam quality was produced with$M^{2}\approx 1.2$at full pump power. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.16 Issue No: Vol. 7 (2019) • Comprehensive investigation on producing high-power orbital angular momentum beams by coherent combining technology • Authors: Dong Zhi; Tianyue Hou, Pengfei Ma, Yanxing Ma, Pu Zhou, Rumao Tao, Xiaolin Wang, Lei Si Abstract: High-power orbital angular momentum (OAM) beams have distinct advantages in improving capacity and data receiving for free-space optical communication systems at long distances. Utilizing the coherent combination of a beam array technique and helical phase approximation by a piston phase array, we have proposed a generating system for a novel high-power beam carrying OAM, which could overcome the power limitations of a common vortex phase modulator and a single beam. The characteristics of this generating method and the orthogonality of the generated OAM beams with different eigenstates have been theoretically analyzed and verified. Also a high-power OAM beam produced by coherent beam combination (CBC) of a six-element hexagonal fiber amplifier array has been experimentally implemented. Results show that the CBC technique utilized to control the piston phase differences among the array beams has a high efficiency of 96.3%. On the premise of CBC, we have obtained novel vortex beams carrying OAM of$\pm 1$by applying an additional piston phase array modulation on the corresponding beam array. The experimental results agree approximately with the theoretical analysis. This work could be beneficial to areas that need high-power OAM beams, such as ultra-long distance free-space optical communications, biomedical treatments, and powerful trapping and manipulation under deep potential wells. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.17 Issue No: Vol. 7 (2019) • High-repetition-rate, high-peak-power 1450 nm laser source based on optical parametric chirped pulse amplification • Authors: Pengfei Wang; Beijie Shao, Hongpeng Su, Xinlin Lv, Yanyan Li, Yujie Peng, Yuxin Leng Abstract: We present a high-peak-power, near-infrared laser system based on optical parametric chirped pulse amplification pumped by a home-built picosecond pumping laser, which can generate over 40 mJ energy at 1450 nm center wavelength and operate at 100 Hz repetition rate. Subsequently, the chirped laser pulses are compressed down to 60 fs with 26.5 mJ energy, corresponding to a peak power of 0.44 TW. This high-energy, long-wavelength laser source is highly suitable for driving various nonlinear optical phenomena, such as high-order harmonic generation and high-flux coherent extreme ultraviolet/soft X-ray radiation. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.19 Issue No: Vol. 7 (2019) • Fabrication of kW-level chirped and tilted fiber Bragg gratings and filtering of stimulated Raman scattering in high-power CW oscillators • Authors: Kerong Jiao; Jian Shu, Hua Shen, Zhiwen Guan, Feiyan Yang, Rihong Zhu Abstract: Suppression of stimulated Raman scattering (SRS) by means of chirped and tilted fiber Bragg gratings (CTFBGs) has become a key topic. However, research on high-power systems is still lacking due to two problems. Firstly, after the inscription, there are a large number of hydroxyl compounds and hydrogen molecules in CTFBGs that cause significant heating due to their strong infrared absorption. Secondly, CTFBGs can couple Stokes light from the core to the cladding and the coating, which causes serious heating in the coating of the CTFBG. Aimed at overcoming these bottlenecks, a process that combines constant-low-temperature and variable-high-temperature annealing is used to reduce the thermal slope of the CTFBG. Also, a segmented-corrosion cladding power stripping technology is used on the CTFBG to remove the Stokes light which is coupled to the cladding, which solves the problem of overheating in the coating of the CTFBG. Thereby, a CTFBG with both a kilowatt-level power-carrying load and the ability to suppress SRS in a fiber laser has been developed. Further, we establish a kW-level CW oscillator to test the CTFBG. Experimental results demonstrate that the power-carrying load of the CTFBG is close to 1 kW, the thermal slope is lower than$0.015\,^{\circ }\text{C}/\text{W}$, and the SRS suppression ratio is nearly 23 dB. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.18 Issue No: Vol. 7 (2019) • High-extraction-efficiency, nanosecond bidirectional ring amplifier with twin pulses • Authors: Tiancheng Yu; Jiangtao Guo, Gang Xia, Xiang Zhang, Fan Gao, Jiangfeng Wang, Wei Fan, Xiao Yuan Abstract: The output performances of a bidirectional ring amplifier with twin pulses are demonstrated. Compared to the extraction efficiency of 32% for single-pulse injection, the extraction efficiency of stored energy for twin-pulse injection with bidirectional propagation is increased to 60%. The maximum output energies of the twin pulses are 347 mJ and 351 mJ, and the output energy of a single pulse is only 373 mJ under the same amplifier operating conditions. The experimental results show that the bidirectional ring amplifier with twin pulses can achieve a higher extraction efficiency of stored energy at a lower operating fluence, and has potential applications in high-power and high-energy laser facilities. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.14 Issue No: Vol. 7 (2019) • Band-stop angular filtering with hump volume Bragg gratings • Authors: Fan Gao; Xin Wang, Tiancheng Yu, Xiang Zhang, Xiao Yuan Abstract: A band-stop angular filter (BSF) based on hump volume Bragg gratings (HVBGs) is proposed. Band-stop filtering in a two-stage amplifier laser system is discussed and simulated. Simulation results show that small-scale self-focusing effects in the laser system can be effectively suppressed with the BSF due to the control of fast nonlinear growth in a specific range of spatial frequencies in the laser beam. Near-field modulation of the output beam from the laser system was decreased from 2.69 to 1.37 by controlling the fast nonlinear growth of spatial frequencies ranging from$0.6~\text{mm}^{-1}$to$1.2~\text{mm}^{-1}$with the BSF. In addition, the BSF can be used in a plug-and-play scheme and has potential applications in high-power laser systems. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.12 Issue No: Vol. 7 (2019) • Generation of high energy laser-driven electron and proton sources with the 200 TW system VEGA 2 at the Centro de Laseres Pulsados • Authors: L. Volpe; R. Fedosejevs, G. Gatti, J. A. Pérez-Hernández, C. Méndez, J. Apiñaniz, X. Vaisseau, C. Salgado, M. Huault, S. Malko, G. Zeraouli, V. Ospina, A. Longman, D. De Luis, K. Li, O. Varela, E. García, I. Hernández, J. D. Pisonero, J. García Ajates, J. M. Alvarez, C. García, M. Rico, D. Arana, J. Hernández-Toro, L. Roso Abstract: The Centro de Laseres Pulsados in Salamanca, Spain has recently started operation phase and the first user access period on the 6 J 30 fs 200 TW system (VEGA 2) already started at the beginning of 2018. In this paper we report on two commissioning experiments recently performed on the VEGA 2 system in preparation for the user campaign. VEGA 2 system has been tested in different configurations depending on the focusing optics and targets used. One configuration (long focal length$F=130$cm) is for underdense laser–matter interaction where VEGA 2 is focused onto a low density gas-jet generating electron beams (via laser wake field acceleration mechanism) with maximum energy up to 500 MeV and an X-ray betatron source with a 10 keV critical energy. A second configuration (short focal length$F=40$cm) is for overdense laser–matter interaction where VEGA 2 is focused onto a$5~\unicode[STIX]{x03BC}\text{m}$thick Al target generating a proton beam with a maximum energy of 10 MeV and temperature of 2.5 MeV. In this paper we present preliminary experimental results. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.10 Issue No: Vol. 7 (2019) • Optical diagnostics for density measurement in high-quality laser-plasma electron accelerators • Authors: Fernando Brandi; Leonida Antonio Gizzi Abstract: Implementation of laser-plasma-based acceleration stages in user-oriented facilities requires the definition and deployment of appropriate diagnostic methodologies to monitor and control the acceleration process. An overview is given here of optical diagnostics for density measurement in laser-plasma acceleration stages, with emphasis on well-established and easily implemented approaches. Diagnostics for both neutral gas and free-electron number density are considered, highlighting real-time measurement capabilities. Optical interferometry, in its various configurations, from standard two-arm to more advanced common-path designs, is discussed, along with spectroscopic techniques such as Stark broadening and Raman scattering. A critical analysis of the diagnostics presented is given concerning their implementation in laser-plasma acceleration stages for the production of high-quality GeV electron bunches. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.11 Issue No: Vol. 7 (2019) • High-peak-power temporally shaped nanosecond fiber laser immune to SPM-induced spectral broadening • Authors: Rongtao Su; Pengfei Ma, Pu Zhou, Zilun Chen, Xiaolin Wang, Yanxing Ma, Jian Wu, Xiaojun Xu Abstract: High-peak-power transform-limited narrow-linewidth nanosecond all-fiber lasers are desired in a range of applications. However, their linewidths will be broadened by self-phase modulation (SPM). We propose a novel concept that generates transform-limited laser pulses by temporally shaping the pulse seed. The impact of the pulse shape on SPM-induced spectral broadening was studied numerically and experimentally. It was found theoretically that the square-shape pulsed laser is immune to SPM-induced spectral broadening. Based on this principle, we built a high-peak-power, linearly polarized, square-shape nanosecond all-fiber laser in a master oscillator power amplifier (MOPA) configuration. Stimulated Brillouin scattering (SBS) limited peak powers of 4.02 kW, 5.06 kW, 6.52 kW and 9.30 kW were obtained at pulse widths of 8 ns, 7 ns, 6 ns and 5 ns. Thanks to the square-shape pulsed seed, the linewidths at maximum peak power remained at 129.5 MHz, 137.6 MHz, 156.2 MHz and 200.1 MHz, respectively, close to the transform-limited values of 110.8 MHz, 126.6 MHz, 147.7 MHz and 177.3 MHz. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.13 Issue No: Vol. 7 (2019) • All-fiber high-power linearly polarized supercontinuum generation from polarization-maintaining photonic crystal fibers • Authors: Yue Tao; Sheng-Ping Chen Abstract: We demonstrate an all-fiber high-power linearly polarized supercontinuum source with polarization-maintaining photonic crystal fibers (PM-PCFs) as the nonlinear medium. The source exhibits an average output power of 3.8 W with a flat spectrum from 480 nm to 2100 nm at the$-$10 dB level, except for the residual pump peak. The polarization extinction ratio (PER) is measured to be greater than 20 dB at selected sample wavelength points (532 nm, 1064 nm and 1550 nm) at the highest pump power level and greater than 20 dB at all wavelengths from 800 nm to 1500 nm at the low pump power level. We also experimentally study the spectral properties when the pump light propagates along different axes of the PM-PCF. The results show that propagating parallel to the slow axis enables a broader spectrum in the PM-PCF in this case, probably due to matching of the dispersion properties with the pump light, which is qualitatively in accordance with the numerical simulation. To our best knowledge, this is the first demonstration of a watt-level linearly polarized supercontinuum source generated from PM-PCFs in an all-fiber structure. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.15 Issue No: Vol. 7 (2019) • Innovative Education and Training in high power laser plasmas (PowerLaPs) for plasma physics, high power laser–matter interactions and high energy density physics – theory and experiments • Authors: John Pasley; Georgia Andrianaki, Andreas Baroutsos, Dimitri Batani, Emmanouil P. Benis, Marco Borghesi, Eugene Clark, Donna Cook, Emmanuel D’Humieres, Vasilios Dimitriou, Brendan Dromey, Michael Ehret, Ioannis Fitilis, Anastasios Grigoriadis, Satya Kar, Evaggelos Kaselouris, Ondrej Klimo, Michel Koenig, Kyriaki Kosma, George Koundourakis, Milan Kucharik, Aveen Lavery, Jiri Limpouch, Yannis Orphanos, Nektarios A. Papadogiannis, Stelios Petrakis, Dave Riley, Maria Serena Rivetta, Laura Tejada Pascual, João Jorge Santos, Alexandros Skoulakis, Ioannis Tazes, Vladimir Tikhonchuk, Jocelain Trela, Calliope Tsitou, Luca Volpe, Steven White, Mark Yeung, Michael Tatarakis Abstract: The Erasmus Plus programme ‘Innovative Education and Training in high power laser plasmas’, otherwise known as PowerLaPs, is described. The PowerLaPs programme employs an innovative paradigm in that it is a multi-centre programme where teaching takes place in five separate institutes with a range of different aims and styles of delivery. The ‘in class’ time is limited to four weeks a year, and the programme spans two years. PowerLaPs aims to train students from across Europe in theoretical, applied and laboratory skills relevant to the pursuit of research in laser–plasma interaction physics and inertial confinement fusion (ICF). Lectures are intermingled with laboratory sessions and continuous assessment activities. The programme, which is led by workers from the Technological Educational Institute (TEI) of Crete, and supported by co-workers from the Queen’s University Belfast, the University of Bordeaux, the Czech Technical University in Prague, Ecole Polytechnique, the University of Ioannina, the University of Salamanca and the University of York, has just completed its first year. Thus far three Learning Teaching Training (LTT) activities have been held, at the Queen’s University Belfast, the University of Bordeaux and the Centre for Plasma Physics and Lasers (CPPL) of TEI Crete. The last of these was a two-week long Intensive Programme (IP), while the activities at the other two universities were each five days in length. Thus far work has concentrated upon training in both theoretical and experimental work in plasma physics, high power laser–matter interactions and high energy density physics. The nature of the programme will be described in detail and some metrics relating to the activities carried out to date will be presented. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.7 Issue No: Vol. 7 (2019) • Bremsstrahlung emission from high power laser interactions with constrained targets for industrial radiography • Authors: C. D. Armstrong; C. M. Brenner, C. Jones, D. R. Rusby, Z. E. Davidson, Y. Zhang, J. Wragg, S. Richards, C. Spindloe, P. Oliveira, M. Notley, R. Clarke, S. R. Mirfayzi, S. Kar, Y. Li, T. Scott, P. McKenna, D. Neely Abstract: Laser–solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging. A bright, energetic X-ray pulse can be driven from a small source, making it ideal for high resolution X-ray radiography. By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced, enabling imaging with enhanced resolution and contrast. Using constrained targets we demonstrate experimentally a$(20\pm 3)~\unicode[STIX]{x03BC}\text{m}$X-ray source, improving the image quality compared to unconstrained foil targets. Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target, driving a brighter source of X-rays. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.8 Issue No: Vol. 7 (2019) • Maximizing magnetic field generation in high power laser–solid interactions • Authors: L. G. Huang; H. Takabe, T. E. Cowan Abstract: In order to understand the transport of fast electrons within solid density targets driven by an optical high power laser, we have numerically investigated the dynamics and structure of strong self-generated magnetic fields in such experiments. Here we present a systematic study of the bulk magnetic field generation due to the ponderomotive current, Weibel-like instability and resistivity gradient between two solid layers. Using particle-in-cell simulations, we observe the effect of varying the laser and target parameters, including laser intensity, focal size, incident angle, preplasma scale length, target thickness and material and experimental geometry. The simulation results suggest that the strongest magnetic field is generated with laser incident angles and preplasma scale lengths that maximize laser absorption efficiency. The recent commissioning of experimental platforms equipped with both optical high power laser and X-ray free electron laser (XFEL), such as European XFEL-HED, LCLS-MEC and SACLA beamlines, provides unprecedented opportunities to probe the self-generated bulk magnetic field by X-ray polarimetry via Faraday rotation with simultaneous high spatial and temporal resolution. We expect that this systematic numerical investigation will pave the way to design and optimize near future experimental setups to probe the magnetic fields in such experimental platforms. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.9 Issue No: Vol. 7 (2019) • Analysis on FM-to-AM conversion of SSD beam induced by etalon effect in a high-power laser system • Authors: Ping Li; Wei Wang, Jingqin Su, Xiaofeng Wei Abstract: FM-to-AM (frequency modulation-to-amplitude modulation) conversion caused by nonuniform spectral transmission of broadband beam is harmful to high-power laser facility. Smoothing by spectral dispersion (SSD) beam is a special broadband beam for its monochromatic feature at the given time and space on the near field. The traditional method which uses the optical spectral transfer function as filters cannot accurately describe its AM characteristics. This paper presents the theoretical analysis of the etalon effect for SSD beam. With a low-order approximation, the analytic model of the temporal shape of SSD beam is obtained for the first time, which gives the detailed AM characteristics at local and integral aspects, such as the variation of ripples width and amplitude in general situation. We also analyze the FM-to-AM conversion on the focal plane; in the focusing process, the lens simply acts as an integrator to smooth the AM of SSD beam. Because AM control is necessary for the near field to avoid optics damage and for the far field to ensure an optimal interaction of laser–target, our investigations could provide some important phenomena and rules for pulse shape control. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.74 Issue No: Vol. 7 (2019) • Absolute instability modes due to rescattering of stimulated Raman scattering in a large nonuniform plasma • Authors: Yao Zhao; Zhengming Sheng, Suming Weng, Shengzhe Ji, Jianqiang Zhu Abstract: Absolute instability modes due to secondary scattering of stimulated Raman scattering (SRS) in a large nonuniform plasma are studied theoretically and numerically. The backscattered light of convective SRS can be considered as a pump light with a finite bandwidth. The different frequency components of the backscattered light can be coupled to develop absolute SRS instability near their quarter-critical densities via rescattering process. The absolute SRS mode develops a Langmuir wave with a high phase velocity of about$c/\sqrt{3}$with$c$the light speed in vacuum. Given that most electrons are at low velocities in the linear stage, the absolute SRS mode grows with very weak Landau damping. When the interaction evolves into the nonlinear regime, the Langmuir wave can heat abundant electrons up to a few hundred keV via the SRS rescattering. Our theoretical model is validated by particle-in-cell simulations. The absolute instabilities may play a considerable role in the experiments of inertial confinement fusion. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.5 Issue No: Vol. 7 (2019) • Editorial review of HPLSE special issue on laboratory astrophysics • Authors: Francisco Suzuki-Vidal; Yutong Li, Carolyn Kuranz, Colin Danson PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.2 Issue No: Vol. 7 (2019) • Mitigation of stimulated Raman scattering in kilowatt-level diode-pumped fiber amplifiers with chirped and tilted fiber Bragg gratings • Authors: Meng Wang; Le Liu, Zefeng Wang, Xiaoming Xi, Xiaojun Xu Abstract: The average power of diode-pumped fiber lasers has been developed deeply into the kW regime in the past years. However, stimulated Raman scattering (SRS) is still a major factor limiting the further power scaling. Here, we have demonstrated the mitigation of SRS in kilowatt-level diode-pumped fiber amplifiers using a chirped and tilted fiber Bragg grating (CTFBG) for the first time. The CTFBG is designed and inscribed in large-mode-area (LMA) fibers, matching with the operating wavelength of the fiber amplifier. With the CTFBG inserted between the seed laser and the amplifier stage, an SRS suppression ratio of${\sim}10~\text{dB}is achieved in spectrum at the maximum output laser power of 2.35 kW, and there is no reduction in laser slope efficiency and degradation in beam quality. This work proves the feasibility and practicability of CTFBGs for SRS suppression in high-power fiber lasers, which is very useful for the further power scaling. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.1 Issue No: Vol. 7 (2019) • Polarized proton beams from laser-induced plasmas • Authors: Anna Hützen; Johannes Thomas, Jürgen Böker, Ralf Engels, Ralf Gebel, Andreas Lehrach, Alexander Pukhov, T. Peter Rakitzis, Dimitris Sofikitis, Markus Büscher Abstract: We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the particle-in-cell (PIC) simulation code VLPL (Virtual Laser Plasma Lab) to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circularly polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM, Shanghai. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.73 Issue No: Vol. 7 (2019) • Maser radiation from collisionless shocks: application to astrophysical jets • Authors: D. C. Speirs; K. Ronald, A. D. R. Phelps, M. E. Koepke, R. A. Cairns, A. Rigby, F. Cruz, R. M. G. M. Trines, R. Bamford, B. J. Kellett, B. Albertazzi, J. E. Cross, F. Fraschetti, P. Graham, P. M. Kozlowski, Y. Kuramitsu, F. Miniati, T. Morita, M. Oliver, B. Reville, Y. Sakawa, S. Sarkar, C. Spindloe, M. Koenig, L. O. Silva, D. Q. Lamb, P. Tzeferacos, S. Lebedev, G. Gregori, R. Bingham Abstract: This paper describes a model of electron energization and cyclotron-maser emission applicable to astrophysical magnetized collisionless shocks. It is motivated by the work of Begelman, Ergun and Rees [Astrophys. J. 625, 51 (2005)] who argued that the cyclotron-maser instability occurs in localized magnetized collisionless shocks such as those expected in blazar jets. We report on recent research carried out to investigate electron acceleration at collisionless shocks and maser radiation associated with the accelerated electrons. We describe how electrons accelerated by lower-hybrid waves at collisionless shocks generate cyclotron-maser radiation when the accelerated electrons move into regions of stronger magnetic fields. The electrons are accelerated along the magnetic field and magnetically compressed leading to the formation of an electron velocity distribution having a horseshoe shape due to conservation of the electron magnetic moment. Under certain conditions the horseshoe electron velocity distribution function is unstable to the cyclotron-maser instability [Bingham and Cairns, Phys. Plasmas 7, 3089 (2000); Melrose, Rev. Mod. Plasma Phys. 1, 5 (2017)]. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2019.3 Issue No: Vol. 7 (2019) • Role of magnetic field evolution on filamentary structure formation in intense laser–foil interactions • Authors: M. King; N. M. H. Butler, R. Wilson, R. Capdessus, R. J. Gray, H. W. Powell, R. J. Dance, H. Padda, B. Gonzalez-Izquierdo, D. R. Rusby, N. P. Dover, G. S. Hicks, O. C. Ettlinger, C. Scullion, D. C. Carroll, Z. Najmudin, M. Borghesi, D. Neely, P. McKenna Abstract: Filamentary structures can form within the beam of protons accelerated during the interaction of an intense laser pulse with an ultrathin foil target. Such behaviour is shown to be dependent upon the formation time of quasi-static magnetic field structures throughout the target volume and the extent of the rear surface proton expansion over the same period. This is observed via both numerical and experimental investigations. By controlling the intensity profile of the laser drive, via the use of two temporally separated pulses, both the initial rear surface proton expansion and magnetic field formation time can be varied, resulting in modification to the degree of filamentary structure present within the laser-driven proton beam. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.75 Issue No: Vol. 7 (2019) • High-brightness all-fiber Raman lasers directly pumped by multimode laser diodes • Authors: S. A. Babin Abstract: High-brightness fiber laser sources usually utilize active rare-earth-doped fibers cladding-pumped by multimode laser diodes (LDs), but they operate in limited wavelength ranges. Singlemode-passive-fiber based Raman lasers are able to operate at almost any wavelength being pumped by high-power fiber lasers. One of the interesting possibilities is to directly pump graded-index (GRIN) multimode passive fibers by available high-power multimode LDs at 915–940 nm, thus achieving high-power Raman lasing in the wavelength range of 950–1000 nm, which is problematic for rare-earth-doped fiber lasers. Here we review the latest results on the development of all-fiber high-brightness LD-pumped sources based on GRIN fiber with in-fiber Bragg gratings (FBGs). The mode-selection properties of FBGs inscribed by fs pulses supported by the Raman clean-up effect result in efficient conversion of multimode pump into a high-quality output beam at 9xx nm. GRIN fibers with core diameters 62.5, 85 and100~\unicode[STIX]{x03BC}\text{m}$are compared. Further scaling capabilities and potential applications of such sources are discussed. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.76 Issue No: Vol. 7 (2019) • Accurate reconstruction of electric field of ultrashort laser pulse with complete two-step phase-shifting • Authors: Yi Cai; Zhenkuan Chen, Shuiqin Zheng, Qinggang Lin, Xuanke Zeng, Ying Li, Jingzhen Li, Shixiang Xu Abstract: This paper presents a complete two-step phase-shifting (TSPS) spectral phase interferometry for direct electric-field reconstruction (SPIDER) to improve the reconstruction of ultrafast optical fields. Here, complete TSPS acts as a balanced detection that can not only remove the effect of the dc term of the interferogram, but also reduce measurement noises, and thereby improve the capability of SPIDER to measure the pulses with narrow spectra or complex spectral structures. Some prisms are chosen to replace some environment-sensitive optical components, especially reflective optics to improve operating stability and improve signal-to-noise ratio further. Our experiments show that the available shear can be decreased to 1.5% of the spectral width, which is only about$1/3$compared with traditional SPIDER. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.71 Issue No: Vol. 7 (2019) • Review of special issue on high power facility and technical development at the NLHPLP • Authors: Jianqiang Zhu PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.70 Issue No: Vol. 7 (2019) • Quantum electrodynamics experiments with colliding petawatt laser pulses • Authors: I. C. E. Turcu; B. Shen, D. Neely, G. Sarri, K. A. Tanaka, P. McKenna, S. P. D. Mangles, T.-P. Yu, W. Luo, X.-L. Zhu, Y. Yin Abstract: A new generation of high power laser facilities will provide laser pulses with extremely high powers of 10 petawatt (PW) and even 100 PW, capable of reaching intensities of$10^{23}~\text{W}/\text{cm}^{2}$in the laser focus. These ultra-high intensities are nevertheless lower than the Schwinger intensity$I_{S}=2.3\times 10^{29}~\text{W}/\text{cm}^{2}$at which the theory of quantum electrodynamics (QED) predicts that a large part of the energy of the laser photons will be transformed to hard Gamma-ray photons and even to matter, via electron–positron pair production. To enable the investigation of this physics at the intensities achievable with the next generation of high power laser facilities, an approach involving the interaction of two colliding PW laser pulses is being adopted. Theoretical simulations predict strong QED effects with colliding laser pulses of${\geqslant}10~\text{PW}$focused to intensities${\geqslant}10^{22}~\text{W}/\text{cm}^{2}$. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.66 Issue No: Vol. 7 (2019) • High efficiency second harmonic generation of nanojoule-level femtosecond pulses in the visible based on BiBO • Authors: Mario Galletti; Hugo Pires, Victor Hariton, Celso Paiva João, Swen Künzel, Marco Galimberti, Gonçalo Figueira Abstract: We demonstrate high efficiency second harmonic generation (SHG) of near infrared femtosecond pulses using a$\text{BiB}_{3}\text{O}_{6}$crystal in a single-pass tight focusing geometry setup. A frequency doubling efficiency of$63\%is achieved, which is, to the best of our knowledge, the highest value ever reported in the femtosecond regime for such low energy (nJ-level) pumping pulses. Theoretical analyses of the pumping scheme focusing waist and the SHG efficiency are performed, by numerically solving the three wave mixing coupled equations in the plane-wave scenario and by running simulations with a commercial full 3D code. Simulations show a good agreement with the experimental data regarding both the efficiency and the pulse spectral profile. The simulated SHG pulse temporal profile presents the characteristic features of the group velocity mismatch broadening in a ‘thick’ crystal. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.72 Issue No: Vol. 7 (2019) • High damage threshold liquid crystal binary mask for laser beam shaping • Authors: Gang Xia; Wei Fan, Dajie Huang, He Cheng, Jiangtao Guo, Xiaoqin Wang Abstract: In order to improve the damage threshold and enlarge the aperture of a laser beam shaper, photolithographic patterning technology is adopted to design a new type of liquid crystal binary mask. The inherent conductive metal layer of commercial liquid crystal electro-optical spatial light modulators is replaced by azobenzene-based photoalignment layers patterned by noncontact photolithography. Using the azobenzene-based photoalignment layer, a liquid crystal binary mask for beam shaping is fabricated. In addition, the shaping ability, damage threshold, write/erase flexibility and stability of the liquid crystal binary mask are tested. Using a 1 Hz near-IR (1064 nm) laser, the multiple-shot nanosecond damage threshold of the liquid crystal mask is measured to be higher than15~\text{J}/\text{cm}^{2}. The damage threshold of the azobenzene-based photoalignment layer is higher than50~\text{J}/\text{cm}^{2}$under the same testing conditions. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.69 Issue No: Vol. 7 (2019) • Technology development for ultraintense all-OPCPA systems • Authors: J. Bromage; S.-W. Bahk, I. A. Begishev, C. Dorrer, M. J. Guardalben, B. N. Hoffman, J. B. Oliver, R. G. Roides, E. M. Schiesser, M. J. Shoup III, M. Spilatro, B. Webb, D. Weiner, J. D. Zuegel Abstract: Optical parametric chirped-pulse amplification (OPCPA) [Dubietis et al., Opt. Commun. 88, 437 (1992)] implemented by multikilojoule Nd:glass pump lasers is a promising approach to produce ultraintense pulses (${>}10^{23}~\text{W}/\text{cm}^{2}$). Technologies are being developed to upgrade the OMEGA EP Laser System with the goal to pump an optical parametric amplifier line (EP OPAL) with two of the OMEGA EP beamlines. The resulting ultraintense pulses (1.5 kJ, 20 fs,$10^{24}~\text{W}/\text{cm}^{2}$) would be used jointly with picosecond and nanosecond pulses produced by the other two beamlines. A midscale OPAL pumped by the Multi-Terawatt (MTW) laser is being constructed to produce 7.5-J, 15-fs pulses and demonstrate scalable technologies suitable for the upgrade. MTW OPAL will share a target area with the MTW laser (50 J, 1 to 100 ps), enabling several joint-shot configurations. We report on the status of the MTW OPAL system, and the technology development required for this class of all-OPCPA laser system for ultraintense pulses. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.64 Issue No: Vol. 7 (2019) • High-power, Joule-class, temporally shaped multi-pass ring laser amplifier with two Nd:glass laser heads • Authors: Jiangtao Guo; Jiangfeng Wang, Hui Wei, Wenfa Huang, Tingrui Huang, Gang Xia, Wei Fan, Zunqi Lin Abstract: A high-power, Joule-class, nanosecond temporally shaped multi-pass ring laser amplifier system with two neodymium-doped phosphate glass (Nd:glass) laser heads is demonstrated. The laser amplifier system consists of three parts: an all-fiber structure seeder, a diode-pumped Nd:glass regenerative amplifier and a multi-pass ring amplifier, where the thermally induced depolarization of two laser heads is studied experimentally and theoretically. Following the injection of a square pulse with the pulse energy of 0.9 mJ and pulse width of 6 ns, a 0.969-J high-energy laser pulse at 1 Hz was generated, which had the ability to change the waveform arbitrarily, based on the all-fiber structure front end. The experimental results show that the proposed laser system is promising to be adopted in the preamplifier of high-power laser facilities. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.68 Issue No: Vol. 7 (2019) • Cumulative material damage from train of ultrafast infrared laser pulses • Authors: A. Hanuka; K. P. Wootton, Z. Wu, K. Soong, I. V. Makasyuk, R. J. England, L. Schächter Abstract: We developed a systematic experimental method to demonstrate that damage threshold fluence (DTF) for fused silica changes with the number of femtosecond laser (800 nm,$65\pm 5~\text{fs}$, 10 Hz and 600 Hz) pulses. Based on the experimental data, we were able to develop a model which indicates that the change in DTF varies with the number of shots logarithmically up to a critical value. Above this value, DTF approaches an asymptotic value. Both DTF for a single shot and the asymptotic value as well as the critical value where this happens, are extrinsic parameters dependent on the configuration (repetition rate, pressure and geometry near or at the surface). These measurements indicate that the power of this dependence is an intrinsic parameter independent of the configuration. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.62 Issue No: Vol. 7 (2019) • Dual-wavelength bidirectional pumped high-power Raman fiber laser • Authors: Zehui Wang; Qirong Xiao, Yusheng Huang, Jiading Tian, Dan Li, Ping Yan, Mali Gong Abstract: In this paper, we reported both the experimental demonstration and theoretical analysis of a Raman fiber laser based on a master oscillator–power amplifier configuration. The Raman fiber laser adopted the dual-wavelength bidirectional pumping configuration, utilizing 976 nm laser diodes and 1018 nm fiber lasers as the pump sources. A 60-m-long$25/400~\unicode[STIX]{x03BC}\text{m}$ytterbium-doped fiber was used to convert the power from 1070 to 1124 nm, realizing a maximum power output of 3.7 kW with a 3 dB spectral width of 6.8 nm. Moreover, we developed a multi-frequency model taking into consideration the Raman gain spectrum and amplified spontaneous emission. The calculated spectral broadening of both the forward and backward laser was in good agreement with the experimental results. Finally, a 1.5 kW, 1183 nm second-order Raman fiber laser was further experimentally demonstrated by the addition of a 70-m-long germanium-doped passive fiber. PubDate: 2019-01-01T00:00:00.000Z DOI: 10.1017/hpl.2018.67 Issue No: Vol. 7 (2019) • Study of backward terahertz radiation from intense picosecond laser–solid interactions using a multichannel calorimeter system • Authors: H. Liu; G.-Q. Liao, Y.-H. Zhang, B.-J. Zhu, Z. Zhang, Y.-T. Li, G. G. Scott, D. Rusby, C. Armstrong, E. Zemaityte, P. Bradford, N. Woolsey, P. Huggard, P. McKenna, D. Neely Abstract: A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broad-band spectral measurement of terahertz (THz) radiation generated in intense laser–plasma interactions. The generation mechanism of backward THz radiation (BTR) is studied by using the multichannel calorimeter system in an intense picosecond laser–solid interaction experiment. The dependence of the BTR energy and spectrum on laser energy, target thickness and pre-plasma scale length is obtained. These results indicate that coherent transition radiation is responsible for the low-frequency component (${}\$ 3 THz) of BTR.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2018.60
Issue No: Vol. 7 (2019)

• nELOPE+main+amplifier+HEPA I+using+broadband+nanosecond+pulses&rft.title=High+Power+Laser+Science+and+Engineering&rft.issn=2095-4719&rft.date=2019&rft.volume=7&rft.aulast=Albach&rft.aufirst=D.&rft.au=D.+Albach&rft.au=M.+Loeser,+M.+Siebold,+U.+Schramm&rft_id=info:doi/10.1017/hpl.2018.59">Performance demonstration of the PEnELOPE main amplifier HEPA I using

• Authors: D. Albach; M. Loeser, M. Siebold, U. Schramm
Abstract: We report on the energetic and beam quality performance of the second to the last main amplifier section HEPA I of the PEnELOPE laser project. A polarization coupled double-12-pass scheme to verify the full amplification capacity of the last two amplifiers HEPA I and II was used. The small signal gain for a narrow-band continuous wave laser was 900 and 527 for a broadband nanosecond pulse, demonstrating 12.6 J of output pulse energy. Those pulses, being spectrally wide enough to support equivalent 150 fs long ultrashort pulses, are shown with an excellent spatial beam quality. A first active correction of the wavefront using a deformable mirror resulted in a Strehl ratio of 76% in the single-12-pass configuration for HEPA I.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2018.59
Issue No: Vol. 7 (2019)

• Reflection of intense laser light from microstructured targets as a
potential diagnostic of laser focus and plasma temperature

• Authors: J. Jarrett; M. King, R. J. Gray, N. Neumann, L. Döhl, C. D. Baird, T. Ebert, M. Hesse, A. Tebartz, D. R. Rusby, N. C. Woolsey, D. Neely, M. Roth, P. McKenna
Abstract: The spatial-intensity profile of light reflected during the interaction of an intense laser pulse with a microstructured target is investigated experimentally and the potential to apply this as a diagnostic of the interaction physics is explored numerically. Diffraction and speckle patterns are measured in the specularly reflected light in the cases of targets with regular groove and needle-like structures, respectively, highlighting the potential to use this as a diagnostic of the evolving plasma surface. It is shown, via ray-tracing and numerical modelling, that for a laser focal spot diameter smaller than the periodicity of the target structure, the reflected light patterns can potentially be used to diagnose the degree of plasma expansion, and by extension the local plasma temperature, at the focus of the intense laser light. The reflected patterns could also be used to diagnose the size of the laser focal spot during a high-intensity interaction when using a regular structure with known spacing.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2018.63
Issue No: Vol. 7 (2019)

• Dynamic stabilization of plasma instability

• Authors: S. Kawata; T. Karino, Y. J. Gu
Abstract: The paper presents a review of dynamic stabilization mechanisms for plasma instabilities. One of the dynamic stabilization mechanisms for plasma instability was proposed in the paper [Kawata, Phys. Plasmas 19, 024503 (2012)], based on a perturbation phase control. In general, instabilities emerge from the perturbations. Normally the perturbation phase is unknown, and so the instability growth rate is discussed. However, if the perturbation phase is known, the instability growth can be controlled by a superimposition of perturbations imposed actively. Based on this mechanism we present the application results of the dynamic stabilization mechanism to the Rayleigh–Taylor instability (RTI) and to the filamentation instability as typical examples in this paper. On the other hand, in the paper [Boris, Comments Plasma Phys. Control. Fusion 3, 1 (1977)] another mechanism was proposed to stabilize RTI, and was realized by the pulse train or the laser intensity modulation in laser inertial fusion [Betti et al., Phys. Rev. Lett. 71, 3131 (1993)]. In this latter mechanism, an oscillating strong force is applied to modify the basic equation, and consequently the new stabilization window is created. Originally the latter was proposed by Kapitza. We review the two stabilization mechanisms, and present the application results of the former dynamic stabilization mechanism.
PubDate: 2019-01-01T00:00:00.000Z
DOI: 10.1017/hpl.2018.61
Issue No: Vol. 7 (2019)

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