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Development and preliminary results of phase contrast imaging diagnostic on HL-2A
摘要： Phase Contrast Imaging (PCI) diagnostic has been developed on HL-2 A tokamak. The chord integral density fluctuations of plasma can be obtained by measuring the phase shift of CO2 laser which has a wavelength of 10.6 μm after passing through plasma. The 32-channel detector array enables PCI to diagnose density fluctuations with wavenumbers ranging from 2 cm?1 to 15 cm?1. The temporal resolution of PCI is better than 2 μs which makes it suitable for broadband turbulence research. Calibration by the sound source confirms that PCI is able to discriminate a wide range of wavenumbers. The plasma density fluctuations measured by PCI on HL-2 A is presented for the first time. Comparison of MHD instability investigations with magnetic probe data shows the reliability of this PCI diagnostic.
关键词： Phase shift,Plasma density fluctuations,PCI
更新于2025-09-23 15:22:29
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The implementation and data analysis of an interferometer for intense short pulse laser experiments
摘要： We present an interferometry setup and the detailed fringe analysis method for intense short pulse (SP) laser experiments. The interferometry scheme was re?ned through multiple campaigns to investigate the effects of pre-plasmas on energetic electrons at the Jupiter Laser Facility at Lawrence Livermore National Laboratory. The interferometer used a frequency doubled (λ = 0.527 μm) 0.5 ps long optical probe beam to measure the pre-plasma density, an invaluable parameter to better understand how varying pre-plasma conditions affect the characteristics of the energetic electrons. The hardware of the diagnostic, data analysis and example data are presented. The diagnostic setup and the analysis procedure can be employed for any other SP laser experiments and interferograms, respectively.
关键词： short pulse laser,optical interferometry,Mach–Zehnder interferometer,picosecond probe,plasma density
更新于2025-09-19 17:13:59
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Time-resolved interference microscopy for studying nonideal plasma formed by high-power femtosecond laser pulses
摘要： Measurement results of characteristic size of plasma density inhomogeneity on the surface of bulk iron target formed under action of femtosecond laser pulses with intensity of 1016 W/cm2 are presented. Investigations are performed using time-resolved interference microscopy technique. Femtosecond laser pulses with high time contrast of 107 generated by chromium:forsterite laser system are applied. Efficacy of the chosen technique is demonstrated; the size of plasma inhomogeneity is shown to be less than 30 nm.
关键词： femtosecond laser pulses,time-resolved interference microscopy,plasma density inhomogeneity,nonideal plasma
更新于2025-09-16 10:30:52
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Characterization of the fast ionization wave induced by a CO <sub/>2</sub> laser pulse in argon
摘要： Fast ionization wave (FIW), a postbreakdown phenomenon of laser-induced plasma, is observed for a laser intensity of 1011–1013 W/m2 using the CO2 laser pulse in the atmospheric pressure condition. FIW is distinguishable as “overdriven detonation” according to Raizer’s Chapmann-Jouguet detonation theory because FIW is known as the type of laser-absorption wave that has a higher propagation velocity than the laser-supported detonation wave (LSDW). Some reports have described the expansion of FIW using a solid-state laser. Nevertheless, the threshold phenomena between FIW and LSDW are not fundamentally understood. This study used the high-speed visualization and optical emission spectroscopy to investigate the transition of the laser-absorption wave in argon gaseous form. To elucidate the physics of the transition threshold, a 5 J CO2 pulse laser, an Echelle spectrometer, and an intensi?ed CCD camera are used for the quantitative investigation of the plasma temperature and density. Results demonstrate that the FIW front had an electron temperature of 0.7 eV and an electron number density of 2.5 × 1023 m?3. At the FIW–LSDW transition, the electron temperature increased by 1 eV, and the density decreased by 2.2 × 1023 m?3. Besides, the transition threshold and the existence of local-thermodynamic equilibrium were evaluated based on the electron temperature, and the density was obtained from the spectroscopic experiments.
关键词： plasma temperature,optical emission spectroscopy,fast ionization wave,plasma density,CO2 laser,laser-induced plasma
更新于2025-09-12 10:27:22
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Attosecond pulse generation by relativistic flying mirrors in laser-plasma interaction: Effect of plasma density and driver amplitude on the generated pulse
摘要： The generation of high-intensity attosecond pulses by the interaction of two counterpropagating short laser pulses with underdense plasma is investigated. By using parallel fully kinetic particles in cell simulation, which shows the formation of relativistic ?ying mirrors in the wake wave of the intense driver laser pulse and the focusing re?ection of the weak source pulse, it is demonstrated that intense attosecond pulses can be produced under the optimized conditions of plasma density and driver laser amplitude according to the relativistic similarity theory. In addition, it is shown that the frequency of the source pulse is upshifted by a factor from 10 to 80 corresponding to a re?ected radiation wavelength from 20 to 164 nm which lies in the extreme ultraviolet region, while most of the energy lies around a frequency upshift of 20, in agreement with the measured Lorentz factor. The intensity of the main attosecond pulse is two orders higher than the source pulse intensity.
关键词： plasma density,driver amplitude,attosecond pulse generation,relativistic flying mirrors,laser-plasma interaction
更新于2025-09-12 10:27:22
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Strong self-focusing of a chirped pulse laser in thermal quantum plasma under density transition
摘要： In the present manuscript, an analysis has been done on strong self-focusing of a chirped pulse laser in thermal quantum plasma under exponential plasma density transition. It is observed that the beam width parameter reduces up to great extent which in turns enhances the process of self-focusing. It is observed that in the embellishment of self-focusing of laser beam, thermal quantum plasma contributes significantly. Further, it is seen that with change in different parameters like intensity of the laser beam, chirped parameter value and plasma frequency, self-focusing is sensitive and becomes stronger at higher values of these parameters. The present work may have important applications in field of laser interaction with the quantum plasma, laser driven particle accelerators etc.
关键词： thermal quantum plasma,Chirped pulse Laser,self-focusing,exponential plasma density transition
更新于2025-09-12 10:27:22
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Estimation of plasma density perturbation from dusty plasma injection by laser irradiation on tungsten target in DiPS
摘要： To investigate the interaction of dusty plasma with magnetized plasmas at divertor plasma simulator (DiPS), radial profiles of plasma density (ne) and electron temperature (Te) were measured in terms of plasma discharge currents and magnetic flux intensity by using a fast scanning probes (FSP) system with triple tips. Dusty plasma with dusts (a generation rate of 3 μg/s and a size of 1–10 μm) was produced via interactions between a high-power laser beam and a full tungsten target. As ne increases due to dusty plasma injection, the result was ~ 10% at a core region of the magnetized plasma with ne of (2 – 5) × 1011 cm?3 at steady state condition.
关键词： dusty plasma,DiPS,plasma density perturbation,tungsten dust
更新于2025-09-12 10:27:22
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Pump-Probe Study of Plasma Dynamics in Gas-Filled Photonic Crystal Fiber Using Counterpropagating Solitons
摘要： We present a pump-probe technique for monitoring ultrafast polarizability changes. In particular, we use it to measure the plasma density created at the temporal focus of a self-compressing higher-order pump soliton in a gas-?lled hollow-core photonic crystal ?ber. This is done by monitoring the wavelength of the dispersive wave emission from a counterpropagating probe soliton. By varying the relative delay between pump and probe, the plasma density distribution along the ?ber can be mapped out. Compared with recently introduced interferometric side probing for monitoring the plasma density, our technique is relatively immune to instabilities caused by air turbulence and mechanical vibration. The results of two experiments on argon- and krypton-?lled ?ber are presented and compared to numerical simulations. The technique provides an important tool for probing photoionization in many di?erent gases and gas mixtures, as well as ultrafast changes in dispersion in many other contexts.
关键词： photoionization,solitons,plasma density,photonic crystal fiber,pump-probe technique
更新于2025-09-11 14:15:04
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A mixture of vortex terahertz radiation generation in inhomogeneous plasma by considering pump depletion
摘要： An attempt to extend helical terahertz radiation generation based on pump depletion is presented here. By considering an upward plasma density ramp, such a reasonable extension is examined to improve the results. It is claimed that the output terahertz energy is saturated which is attributed to laser pump divergence. The saturation effect is enhanced by considering suitable laser and plasma parameters. The adjustable slope of the density ramp is an important parameter for tuning terahertz generation efficiency, which is restricted to the up and down limit. For the resonant excitation of terahertz radiation, the ripple wave number is suitably chosen to satisfy the phase matching condition. Furthermore, as plasma frequency increases and approaches beat frequency, terahertz generation efficiency increases. Various laser and plasma parameters are employed and we report an efficiency of the order of 5×10?3 for the current scheme.
关键词： Laguerre–Gaussian beam,plasma density ramp,pump depletion,terahertz radiation generation,cross-focusing
更新于2025-09-11 14:15:04