Ling‐qing Zhang

Studies of Recombination X-Ray-Laser Gain and Gain-Medium Uniformity

The time evolution of the uniformity of the line-shaped X-ray-laser gain medium and the spatial characteristics of the recombination X-ray-laser gains of the Li-like ions are studied using long (∼900 ps) and short (∼100 ps) laser pulses.

Arbitrary spectral response fibre edge filters based on tilted chirped grating structures

Summary form only given. Optical edge-filters are useful devices for interrogating fibre Bragg grating (FBG) sensors based on optical intensity measurement, providing advantages of low-cost, fast response and ease of use. We report a novel method for fabricating fibre edge filters with arbitrary spectral response based upon tilted-chirped-grating (TCG) structures.

An alternative method for gain determination of recombination X-ray lasers

Abstract An improved method was proposed for gain determination of recombination X-ray lasers. The axial line intensity ratio of the lasing emission to an optically thin spontaneous emission is used to overcome the intensity fluctuations caused by shot-to-shot randomness in laser conditions. With this method, the gain of the Li-like Si 4f-3d lasers at 13.0 nm was measured, which is in agreement with theoretical simulations.

Emission from line‐focused laser‐heated multi‐groove target

Line‐shaped plasma was produced by ablating plasma from multi‐groove Aluminum surface of a groove period of 100 μm, on which the direction of groove (50 μm in depth and 50 μm in width) is perpendicular to the focal line of 1.05 μm 120 ps (FWHM) heating laser. Comparison with the results of flat‐slab target, different spatial profiles of electron density and temperature and line emission intensity were found. Enhancement of on‐axis emission of candidate lasing line of Al10+which maybe originate from enhanced GL value were observed.

Long-period fibre grating bend sensor based on measurement of resonance mode splitting

Summary form only given. Photoinduced long-period fiber gratings (LPGs) have been demonstrated as bend sensors measuring curvature by detecting the bending-induced wavelength shift. We report the realisation of an optical bend sensor based on the measurement of bending-induced resonance mode splitting of the LPG. This is a new approach to fibre optic bend sensing which exhibits a significantly higher sensitivity than the wavelength-shift detection method. We have also investigated the effect of the initial mode coupling strength on the spectral response of the sensor under bending yielding practical design information.

Space-resolved Spectral Diagnosis of Line-shaped Laser-produced Magnesium Plasmas

Space-resolved spectra of line-shaped laser-produced magnesium plasmas in the normal direction of the target have been obtained using a pinhole crystal spectrograph. These spectra are treated by a spectrum analyzing code for obtaining the true spectra and fine structures of overlapped lines. The spatial distributions of electron temperature and density along the normal direction of the target surface have been obtained with different spectral diagnostic techniques. Especially, the electron density plateaus beyond the critical surface in line-shaped magnesium plasmas have been obtained with a fitting technique applied to the Stark-broadened Ly-α wings of hydrogenic ions. The difference of plasma parameters between those obtained by different diagnostic techniques is discussed. Other phenomena, such as plasma satellites, population inversion, etc., which are observed in magnesium plasmas, are also presented.

An experimental study on the conduction region of nonlocalized absorption laser plasmas

Abstract A spectral diagnostic technique has been used to study the properties of conduction regions of laser plasmas. Electron densities beyond the critical surface have been obtained by fitting the Stark-broadened line wing of hydrogenic ions, and the results are in good agreement with the theoretical mode of planar laser-driven ablation. The electron temperature and flux-limited factor of electron thermal conduction have also been estimated.

Development of short-wavelength coherent XUV light sources at SIOFM

Recent progress on the development of short-wavelength coherent XUV light sources at SIOFM is presented, including the space- and time-resolved observation of short-wavelength lasing by lithium-like Si11+, Ca17+, and Ti19+ ions and H-like F8+ ion, and the theoretical design for new approaches, such as controlled expansion cooling, x-ray pumping and strongly radiative cooling.

Space-resolved electron density measurements using the stark-broadened line wings of hydrogenic ions in line-shaped laser plasmas

A program was developed using the Marquardt algorithm method to fit the Stark‐broadened line wings of hydrogenic ions, which can be conveniently used to measure electron density in laser‐produced plasma. Applications of the method are illustrated using space‐resolved 2p‐1s resonance lines in line‐shaped laser plasmas of Mg slab targets irradiated with different laser intensity. Space‐resolved electron densities higher than the critical density are obtained by fitting the Stark‐broadened line wings with the program.

An experimental study on line‐shaped laser‐plasma

Spectral diagnostic technique was used to study the properties of line‐shaped laser plasmas. Electron temperature and electron density profiles were deduced from the spectra obtained by a pinhole crystal spectrograph. The Stark‐broadened line‐wings of hydrogenic ions were used to deduce the electron density beyond the critical surface, and the results were compared with the theoretical model of planar laser‐driven ablation. Time integrated properties of line‐shaped laser plasma were also discussed and compared with those of spot‐shaped laser plasma and the laser absorption theoretical estimations.