Giant Laser Research Articles

Density functional theory analysis and novel green chemical mechanical polishing for potassium dihydrogen phosphate

Potassium dihydrogen phosphate (KDP) has recently emerged as a promising candidate for the frequency converter and giant laser. Despite the great efforts to process the ultra-smooth surface of KDP, it is still elusive to remove the flaws precisely, resulting in fatal defects, such as cracks, dissolved cave and embedded grits, inducing the low performance of devices. In this study, a novel green chemical mechanical polishing (CMP) was developed for KDP, consisting of silica, graphene oxide, ethylene glycol and triethanolamine. The CMP developed effectively avoids the defects to KDP. Graphene oxide in slurry promotes the formation of complexes on KDP, which is proved by X-ray photoelectron spectroscopy and infrared Fourier transformation. The experimental results are in good agreement with those of density functional theory calculations using successive O-P bonds. Using the novel CMP, surface roughness Ra of 0.66 nm is achieved with a scanning area of 70 × 50 µm2, and the thickness of damaged layer is 18.27 nm. To the best of our knowledge, this is the lowest surface roughness on KDP after CMP under such a large area of measurement. These findings provide a new pathway to fabricate sub-nanometer ultrasmooth surface of KDP with soft-brittle, deliquescent and temperature-sensitive characteristics.

Modeling and Fault Analysis for Power Conditioning System of Giant Solid-State Laser Facility

Power conditioning system (PCS), which provides matched pulse energy for the amplifier, is the key subsystem of a giant solid-state laser facility. It consists of many power conditioning modules (PCMs). Some of the catastrophic faults such as capacitor short-circuit, high voltage cable head short-circuit, or high and low voltage busbar short-circuit, might occur when there is high voltage in the PCMs. To analyze these cases, first, the model of a PCM was proposed. Second, three main faults of a PCM were introduced and the models of them were built. Third, a PCM experimental device with ten xenon lamps in parallel was designed and built, and the experimental results verified the effectiveness of the proposed model. In this article, three fault simulation results were analyzed and the security design recommendations were presented, which can provide reference value for the design of such power system.

Effects of functional alkali in magnetorheological finishing fluid

Magnetorheological (MR) fluids can be utilized for ultra-precise finishing, for instance, in fused silica (FS) optics in giant laser system. However, few modification methods of MR fluid can improve the material removal rate (MRR) and surface quality of the finished optics simultaneously. In this study, we investigated the application of functional alkali additives in MR finishing fluid. MRR was doubled over the untreated MR fluid; meanwhile the surface roughness of the FS converged to 0.44 nm. Such excellent finishing performance can be mainly attributed to the dual functional effects of the triethanol amine (TEA) alkali, the hydroxides released by TEA contributes to the MRR increase and the steric hindrance effect of the ethanol ligands helps improve the surface quality.

High-precision shock equation of state measurements for metallic fluid carbon between 15 and 20 Mbar

Diamond is an efficient ablator material to convert the energy of high-power giant lasers into ablation pressure with applications for High-Energy-Density (HED) science, planetary science, and Inertial Confinement Fusion (ICF) research at the National Ignition Facility (NIF). Unfortunately, current theoretical equation of state models cannot reproduce all the observed experimental data in the multi-megabar regime particularly relevant for HED and ICF research. New experimental data on the behavior of carbon at extreme pressures and temperatures are, therefore, essential to improve our predictive capability to design and analyze dynamic compression experiments for HED or ICF research and build improved equation of state models in the future. Here, we report high-precision laser-driven shock compression measurements on diamond single crystals at the Omega Laser Facility. Using ultrafast Doppler optical Velocimetry Interferometer System for Any Reflector (VISAR) to track the leading shock front and a quartz plate as an in situ reference, we obtain relative pressure-density shock equation-of-state measurements between 15 and 20 Mbar with an impedance-matching procedure. We also report shock-and-release measurements in a spherical geometry at the NIF. The new data provide tight constraints on the compressibility of warm dense carbon along the Hugoniot of full density diamond, allowing us to discriminate between existing theoretical equation-of-state models. We find that both LLNL LEOS 9061 and LANL Sesame 7835 models capture well the shock compressibility in the explored range. LANL Sesame 7835 also reproduces well the observed shock-and-release behavior of diamond near 10–20 Mbar.

The propagation of pulses of a special shape in an inhomogeneous anisotropic medium with dispersion and torsion of the optical axis

An oblique incidence of polarized light pulses with different envelope shapes is considered: triangular, Gaussian, rectangular and in the form of giant laser pulses onto a flat inhomogeneous anisotropic layer with torsion of the optical axis and optical dispersion. The wavelength of an optical pulse carrier is close to the resonance wavelength of an inhomogeneous anisotropic layer. The problem of the propagation of s- and p-polarization waves through a layer, the reflection of impulses of cross-polarized components, the dependence of modulation coefficients during medium torsion and frequency detuning is considered.

Excluding Water Characteristics of Fairing Materials for Seeker Based on Giant Pulse Energy Medium Wave Infrared Laser

Excluding Water Characteristics of Fairing Materials for Seeker Based on Giant Pulse Energy Medium Wave Infrared Laser

Experimental and theoretical analysis of passively Q-switched lasers with a high output coupling

In this work, a passively Q-switched Nd:YAG laser resonator, with an output coupling of more than 90%, was demonstrated. Laser pulse energy, peak power and pulse width were found to increase with the increasing of dissipative loss of the laser resonator, and pulse energy was found to increase from 38.6 mJ to 113 mJ, which almost meant a 200% increase. However, according to previous theoretical analyses of passively Q-switched lasers, pulse energy and peak power would decrease with the increasing of dissipative loss when the second threshold was satisfied, and a giant Q-switched laser pulse would never occur if the second threshold was not satisfied. For the passively Q-switched laser resonator we established, the second threshold was found not to be satisfied because of the high output coupling. So, we modified the solutions of coupled rate equations when the second threshold was not satisfied. Numerical calculation results were carried out, and these calculation results were basically consistent with the experimental results and previous investigations.

Giant lasers in the US threatened with closure

Giant lasers in the US threatened with closure

A plan to seed life throughout the cosmos

The galaxy may contain billions of habitable but lifeless worlds. Claudius Gros at Goethe University Frankfurt, Germany, thinks that people should change it. He believes in directed panspermia: deliberately seeding life throughout the cosmos. To do so, he proposes people use a laser propulsion system that may not be technically out of reach. Breakthrough Starshot is an ambitious existing proposal to use giant lasers and light sails to send tiny probes to Alpha Centauri. The goal is to take pictures of this star. But these systems could also deliver much larger payloads, says Gros.

The effects of particle swarm optimization algorithm on volume ignition gain of Proton–Lithium (7) pellets

When it was found out that the ignition of nuclear fusion hinges upon input energy laser, the efforts in order to make giant lasers began, and energy gains of DT fuel were obtained. But due to the neutrons generation and emitted radioactivity from DT reaction, gains of fuels like Proton–Lithium (7) were also adverted. Therefore, making larger and powerful lasers was followed. Here, using new versions of particle swarm optimization algorithm, it will be shown that available maximum gain of Proton–Lithium (7) is reached only at energies about 1014 J, and not only the highest input energy is not helpful but the efficiency is also decreased.

Lord of the rings.

A giant ring laser, sensitive to the spin of the planet and the twist of earthquakes, will open new windows in earth science.

Formation of high-speed electron jets as the evidence for magnetic reconnection in laser-produced plasma

Experiments about the flow-driven magnetic reconnection in high-energy-density laser-produced plasmas have recently been conducted on different platforms of giant laser facilities. In this paper, we perform two-dimensional (2D) particle-in-cell simulations to study the interactions of two colliding laser-produced plasma bubbles with a self-generated toroidal magnetic field. Two cases are investigated: in one case, the two plasma bubbles have an anti-parallel magnetic field (AP-case) in the colliding region, and in the other case, the two interacting parts of the magnetic field are configured parallel to each other (P-case). In both cases, the quadrupole structure of the out-of-plane magnetic field is observed, as well as the Hall electric field and the electron energization in the colliding region. However, only in the AP-case, three well-collimated in-plane electron jets are observed. Two electron jets along the magnetic field at the edge of the plasma bubbles are formed because the electrons are trapped and accelerated by the out-of-plane electric field located between the two colliding bubbles and then move outward along the magnetic field. The high-speed electron jet in the middle of the outflow region is formed as the electrons are reflected and accelerated in the pileup region of the magnetic field, which is moving outward quickly. We demonstrate that besides the annihilation of the magnetic field in the colliding region between the two laser-produced plasma bubbles approaching each other, the three well-collimated electron jets can also be considered as the evidence for the magnetic reconnection.

From weapons to white dwarfs

Military research centres that use giant lasers to study conditions inside nuclear warheads are increasingly opening their doors to university students. Edwin Cartlidge asks what the labs and the researchers have to gain from the arrangement

Self-Q-switching of a loop laser cavity with a self-pumped four-wave phase-conjugate mirror in an active laser medium

Self-Q-switching of a loop laser cavity with a self-pumped four-wave phase-conjugate mirror in an active laser medium with the use of a Faraday isolator or a passive Q-switch is studied theoretically. It is found that, in contrast to passive Q-switching of an ordinary cavity, a passive Q-switch in a loop phase-conjugate cavity serves as an auxiliary unit that increases the self-Q-switching efficiency by gain gratings in the active laser medium, since it decreases the difference in the intensities of waves that write a phase-conjugate mirror in the active medium, which is similar to the use of a Faraday isolator. However, the passive Q-switch operates alternating the highly efficient writing of a phase-conjugate mirror in the closed state with the highly efficient generation of a giant laser pulse in the open state, which stabilizes the period of repetitive laser pulses.

Physicists x-ray virus with a giant laser

Physicists x-ray virus with a giant laser

Plutonium experiments at NIF draw fire

Groups claim that Department of Energy has failed to assess environmental impacts of nuclear weapons experiments that use giant laser. Groups claim that Department of Energy has failed to assess environmental impacts of nuclear weapons experiments that use giant laser.

Ignition with Laser

To develop a new ignition method, we carried out a series of experiments on ignition with excimer and Nd:YAG lasers. When we use an excimer laser, we can produce radicals in the focus point that advance the mixture’s ignition reaction. When we use a Nd:YAG laser, the focused giant laser pulse induced breakdowns in the mixture. In both cases, the laser ignited the mixture. In this paper, we show some results of our laser ignition studies from the past 20 years at AIST.

NIF Report Asks for More Time to Achieve Ignition

The National Ignition Facility faces an uncertain future after its managers admitted to Congress this month that they need at least another 3 years to try to identify what has prevented the giant laser fusion lab in California from achieving ignition.

Study on Technological Parameters of Polishing Large Aspheric Elements

Large aspheric elements in giant laser facility are fabricated using computer controlled rapid polishing technology. The technological parameters are main influencing factors of efficiency. Base on Preston hypothesis, linear relationship of material removal with polishing pressure, polishing velocity and other conditions are established. According to the material removal function model of computer controlled rapid polishing, the removal function is simulated using MATLAB software. The influencing factors of volume removal efficiency are analyzed. In practice, the optimum polishing parameters are eccentricity 0.4, rotational velocity of principal axis 330 rpm, rotational velocity of polishing pad -600 rpm.

Nonlinear Electron Heat Conduction Equation and Self-Similar Method for 1-D Thermal Waves in the Laser Heating of Solid Density DT Fuel

Electron heat conduction is one way that energy transports in laser heating of fusible target material. The aim of inertial confinement fusion (ICF) is to show that the thermal conductivity is strongly dependent on temperature and the equation of electron heat conduction is a nonlinear equation. In this article, we solve the one-dimensional (1-D) nonlinear electron heat conduction equation with a self-similar method (SSM). This solution has been used to investigate the propagation of 1-D thermal wave from a deuterium-tritium (DT) plane source, which occurs when a giant laser pulse impinges onto a solid DT target. It corresponds to the physical problem of rapid heating of a boundary layer of material, in which the energy of a laser pulse is released in a finite initial thickness.