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The equation of state, melting line and metallization of helium have been studied by using quantum and classical molecular dynamics simulations. The melting line has been obtained by analyzing the radial distribution function and the diffusion parameter which is close to the experimental values. Equations of state when the temperature is less than 4.5 eV and the density is between 0.3 g/cm3 and 5.0 g/cm3 are also studied. Finally, it is found that the temperature can reduce the metallization density and metallization pressure of helium.

The laser-ion acceleration from the ultra-short and ultra-intense laser-matter interactions attracts more and more interest nowadays. When a laser pulse interacts with a target, relativistic electrons are generated in a period of few femtoseconds and driven away by the ponderomotive force, then a huge charge-separation field forms. In general cases, the ion acceleration is determined by this charge-separation field and the scale length of the plasma density. A general time-dependent solution is obtained to describe laser-plasma isothermal expansions into a vacuum, which is the fundamental theory of the laser-ion acceleration. It is adequate for non-quasi-neutral plasmas and different types of the scale length of the density gradient. The previous solutions are some special cases of our general solution. It is found that there exist both a compression layer of the ion velocity distribution and a potential well for some initial conditions. However, many unaccounted idiographic solutions, which may be used to reveal new mechanisms of ion acceleration, may be deduced from our general solutions.

The discharge-pumped KrF excimer was used to amplify ultraviolet ultrashort pulse laser with wavelength of 248.4 nm.The laser energy was amplified from 0.7 mJ to 15 mJ,and the pulse duration was broadened from 550 fs to 1 200 fs, with the beam diameter of 10 mm unchanged. To compress the output pulse duration, the effects of group velocity dispersion and self phase modulation were analyzed,and experimental schemes with four different prism pair were used to introduce negative frequency chirp into the pulse laser in order to compensate the positive frequency chirp introduced by group velocity dispersion and self phase modulation in the CaF2 windows of the amplifer.The results show that if the prism pair is put before the amplifier, the pulse duration can be compressed to 370 fs when the le

We investigate the kinetic energy of expanding plasma of a solid target heated by a ultra-short and ultra-intense laser pulse and the efficiency of energy coupling between the ultra-intense laser pulse and the solid target, in order to increase the utilization ratio of laser energy and to raise the neutron generation farther. Some new ideas about improving the energy utilization by head-on collisions between the expanding plasmas are proposed. The significance is the raise of generation of shorter duration neutron, of the order of picoseconds, which allows for an increase of energy resolution in time-of-flight experiments and also for the investigation of the dynamics of nuclear processes with high temporal resolution.

Precipitation of gold nanoparticles is achieved in silicate glass doped with Au ions by UV femtosecond laser irradiation and subsequent annealing treatment. The influences of different power and annealing temperature on the formation of Au nanoparticles are studied: the higher the laser power, the larger the diameter of Au nanoparticles. As the annealing temperatures increase, the colors of the samples are from light purple to purple-red. The peaks of absorption spectrum of the nanoparticles move to the long wavelength.

Laser-induced plasma spectroscopy (LIPS) made a great progress as a potential technology for nuclear analysis and detection. In this article, the instrumentation of LIPS for In-situ and stand-off application was introduced. The application of LIPS in nuclear industry was reviewed, such as international nuclear safeguard, nuclear materials analysis, hazard material detection and monitoring process, etc.

Stimulated Brillouin scattering (SBS) numerical mode for broadband multimode KrF laser pump with optical breakdown has been built up in this paper. The basic premises of the mode are that KrF spectrum is composed of a number of lines and SBS arises from these lines with coupling to some extent. The broadband SBS threshold strongly depends on pump bandwidth. SBS and optical breakdown occur nearly simultaneously when broadband SBS and breakdown have the same threshold. The decrease of saturation reflectivity for broadband pump radiation is explained with this model. Experimental results agree well with the model.

Proton acceleration experiments were performed by using an ultra-short laser to irradiate gold foils of 5 m and 2.1 m in thickness. The ultra-short laser pulse had the pulse duration of 120 fs and energy of 11 mJ. The peak focal intensity remained around 61016 W/cm2. A Thomson ion spectrometer with CR39 plastic nuclear track detectors were used to observe spectra of the accelerated protons. The spectrum of the 2.1 m foil featured a single peak around 74 keV due to the inefficiency of protons. The maximum energies and efficiencies of accelerated protons increased with decreasing the target thickness. The results were explained by the energy loss of electron transmission and a geometrical effect on hot electron recirculation.

A single-shot transient-grating frequency-resolved optical gating (TG-FROG) device was set up to measure UV ultrashort pulse laser with pulse duration within 10ps.The performance of the device was demonstrated by experimental data measured on discharge-pumped KrF laser which is operated in 10Hz repeated frequency mode,and on electronbeam- pumped KrF laser which is only operated in single-shot mode.For the former,the TG-FROG can distinguish the changes of the pulse shape,spectrum and phase when the pulse chirp is changed.For the later,the TG-FROG finds that the pulse shape has multiple peaks whose pulse duration is about 2ps,and the spectrum is modulated whose bandwidth is about 1.3nm,and the corresponding phases present parabolic structure.

The effort of ISI excimer pulse shaping based on gain depletion for inert confined fusion (ICF) in Heaven-I KrF laser system was introduced. The 24ns ISI pulse has been self-shortened to 10ns with a unique set-up call pulse feedback based on gain switch, which can be combined with the EFISI for the high uniformity beam profile. The shorter ISI pulses with the duration of 3~10ns have been obtained with laser quenching. The further proposal to generate a complex pulse shape for ICF based on gain depletion was discussed in this paper.

We experimentally investigate the generation of hot electrons from the interaction of a moderate-intensity (1016W/cm2) pre-pulsed-free femtosecond laser (6 mJ, 120 fs, at 744 nm) with a solid target. The temperature of the hot electrons is inferred from the hard x-ray (>30 keV) continuum. The measured hard x-ray continuum is fitted by the Maxwellian distribution with two hot-electron temperatures of 45 and 85 keV. Electrons with the lower temperature were accelerated by ``vacuum heating''. However it is necessary to carry out an accurate numerical simulation to explain the generation of hot electrons at higher temperatures.

Contrary to the superposition principle, it is well known that photorefraction exists in the vacuum with the presence of a strong static field, a laser field, or a rotational magnetic field. Different from the classical optical crystals, the refractive index also depends on the phase of the strong electromagnetic field. We obtain the phase and direction dependence of the refractive index of a probe wave incident in the strong field of a circular-polarized plane wave by solving the Maxwell equations corrected by the effective Lagrangian. It may provide a valuable theoretical basis to calculate the polarization evolution of waves in the strong electromagnetic circumstances of pulsar or neutron stars.

Heaven-1, a high power KrF excimer laser system is under development in the China Institute of Atomic Energy. As a first phase, the angular multiplexing master oscillator power amplifier (MOPA) will be completed and used for fundamental research of ICF driver and laser plasma interaction in the near future. This multiplexing MOPA system includes a front-end, two stage KrF excimer laser amplifier pumped by electron beams, an optical angular multiplexing system, synchronization trigger system, and controlling-data acquisition system and some diagnostic systems.

Ultrashort 1022–1024 W/cm2 laser pulses will offer the possibility of producing monoenergetic electron beams in the GeV—TeV level in the future. A laser-electron acceleration scheme is proposed by the interaction between a thin solid foil and an ultra-intense laser pulse for α0 ≥ 800σ0, where α0 is the normalized laser field and σ0 is the normalized plasma surface density. The energy of the electrons as a function of time can be described by a simple model which indicates that an exponential relationship exists between the energy and the normalized time τ. A quasi-monoenergetic high density electron beam with 1.3 GeV energy and a 2.2% energy spread has been predicted for α0 = 223.5 by particle-in-cell simulations. Characteristics of the ultra-high density electron layer formed in the early period of the acceleration are discussed.

A new laser-proton acceleration scheme consisting of two relativistic electron layers, a suprathermal electron layer and a thermal electron cloud is proposed for a0 80σ0, where a0 is the normalized laser field and σ0 is the normalized plasma surface density. This is essentially different from target normal sheath acceleration and radiation pressure acceleration. The persistent opaqueness of the first relativistic electron layer for the incident circular-polarization laser pulse and electron recirculation are key points in forming the new acceleration scheme. A proton beam with a uniform energy distribution in the energy range 1–2 GeV and a monoenergetic proton beam with hundreds of MeV have been predicted for a0 = 39.5.