Ding Yao-Nan

Measurement of the KLL Dielectronic Recombination Resonances in He-like to C-like Kr Ions

The KLL dielectronic recombination processes of highly charged He-like to C-like Kr ions have been studied experimentally. The measurement was performed on the newly developed Shanghai electron beam ion trap (Shanghai-EBIT) facility. Characteristic x-rays from both dielectronic recombination and radiative recombination are detected as the electron beam energy is scanned through the resonances. The KLL resonant strengths obtained are 5.41 × 10−19, 4.33 × 10−19, 3.59 × 10−19, 2.05 × 10−19 and 0.98 × 10−19 cm2 eV for He-like to C-like Kr ions, respectively.

Rosseland Mean Opacity of a High-Z Mixture Plasma

An eight-beam 0.351-µm laser with pulse duration of about 1.0ns and energy of 260 J per beam was injected into a cylindrical cavity to generate intense x-ray radiation on the Shengguang II high power laser facility. A mixture foil of gold and gadolinium and a gold foil were attached on portion of a diagnostic hole in the mid-plane of the cavity and ablated by the intense x-ray radiation. The propagating time of the radiation heat wave in the mixture and the pure gold foil were measured with soft-x-ray spectrometer and by adopting space- and time-resolved measurement technology, respectively. The results show that the mixture of gold and gadolinium has higher Rosseland mean opacity than the gold sample in our experiment.

Experimental observation of ionization and shock fronts in foam targets driven by thermal radiation

The behaviours of ionization and shock propagation in radiatively heated material is crucial for the understanding of indirect drive inertial confinement fusion as well as some astrophysics phenomena. In this work, radiation field with a peak temperature of up to 155 eV was generated in a gold cavity heated by four laser beams on the SG-II laser system and was used to irradiate a plastic foam cylinder at one end. The radiatively ablated foam cylinder was then backlighted side-on by x-ray from a laser-irradiated Ti disk. By observing the transmission decrease due to the shock compression of the foam cylinder, the trajectories of shock front were measured, and from the onset of the intense thermal emission from the side of the cylinder, the propagations of the ionization front were also observed on the same shot. The experimental measurements were compared to predictions of the radiation hydrodynamics code Multi-ID and reasonable agreements were found.

Hot electrons and fast ions produced by coupling of laser with cavity targets

A series of experiments of laser coupling with cavity targets have been carried out on Shenguang 12♯ laser equipment last two years. The measured results of the hard X‐rays have been analyzed in detail by means of the simplified theroretical models in the paper. According to the results of the hard X‐rays measured outside the cavity, the spectrum and energy of the hard X‐rays corrected inside the cavity have been given and based on it the temperature, energy, number, and distribution of the superthermal electrons (hot electrons) have been inferred.

Interaction of 1.05 μm and 0.53 μm lasers with gold disks

Gold disks were irradiated with 1.05 μm and 0.53 μm lasers at pulse duration of ∼0.8 ns, intensity ranging from 5×1013 W/cm2 to 4×1015 W/cm2 on the SHEN GUANG I laser facility in China. The experimental results of laser absorption, scattering light, x‐ray emission and plasma blow‐off are presented in this paper. When the laser irradiated the gold disk obliquely, the angular distribution of scattered lights produced by 0.53 μm lasers disagree with that predicted by the Brillouin scattering theory. The angular distribution is different from that reported previously by the others.

Experimental Scaling for Mass Ablation Rate in Planar Targets Irradiated by Smoothed 0.351 µm Laser Beam

Layered planar targets, consists of Al and Au layers, were irradiated by smoothed 0.351-µm-high power laser with relatively large focus spot on Xingguang II laser facility. The burn-through time of laser ablation to Al sample has been obtained by measuring the delay time of Au N-Band x-ray emission with respect to the Al K-Band x-ray emission. The scaling law of mass ablation rate with the laser flux has been obtained by only varying the laser energy on the target surface on different shots. The experimental scaling law is greatly different from the results of Key et al. [Phys. Fluids 23(1983) 2011] and is in good agreement with the analytical model.

High-Speed Photography Of Light Beams Transmitted Through Pinhole Targets

A method of high speed photography is presented. It was designed and performed in order to study temporal behaviours of plasma closure effects of pinhole targets in laser plasma experiments. A series of high speed photographs were taken for the laser beam transmitted through the pinhole targets. Spatially resolved and integrated temporal histories of closure effects were observed, respectively. Some physical information about closure effect, for example, closure speed and so on was studied.