Application of molybdenum target X-ray photography in imaging analysis of caudal intervertebral disc degeneration in rats

BACKGROUND Conventional plain X-ray images of rats,the most common animals used as degeneration models,exhibit unclear vertebral structure and blurry intervertebral disc spaces due to their small size,slender vertebral bodies.AIM To apply molybdenum target X-ray photography in the evaluation of caudal intervertebral disc(IVD)degeneration in rat models.METHODS Two types of rat caudal IVD degeneration models(needle-punctured model and endplate-destructed model)were established,and their effectiveness was verified using nuclear magnetic resonance imaging.Molybdenum target inspection and routine plain X-ray were then performed on these models.Additionally,four observers were assigned to measure the intervertebral height of degenerated segments on molybdenum target plain X-ray images and routine plain X-ray images,respectively.The degeneration was evaluated and statistical analysis was subsequently conducted.RESULTS Nine rats in the needle-punctured model and 10 rats in the endplate-destructed model were effective.Compared with routine plain X-ray images,molybdenum target plain X-ray images showed higher clarity,stronger contrast,as well as clearer and more accurate structural development.The McNemar test confirmed that the difference was statistically significant(P=0.031).In the two models,the reliability of the intervertebral height measured by the four observers on routine plain X-ray images was poor(ICC<0.4),while the data obtained from the molybdenum target plain X-ray images were more reliable.CONCLUSIONMolybdenum target inspection can obtain clearer images and display fine calcification in the imaging evaluation of caudal IVD degeneration in rats,thus ensuring a more accurate evaluation of degeneration.

L3-Edge Jump and Shift on White-Line of Pd Interlayer for Trilaminar Neutron Production Target under H2^＋ Irradiation

Interlayer Pd for the Li/Pd/Cu neutron target for BNCT （boron neutron capture therapy） was characterized after 0.1-5 keV H2^＋ irradiation by XAFS （X-ray absorption fine structure） technique, and following conclusions were derived： （1） from the XAFS observation of white line of Pd, remarkable Pd L3 edge jump was found in 1.1-3 times higher than before irradiation in low irradiation fluence; （2） this fact indicates increase of hole density in Pd 4d-band, whereas, no change was observed for XASF spectra of Ag sample under the same irradiation conditions; （3） remarkable Pd L3 edge shift of 0.12-0.66 eV was also found with increase of H2＋ irradiation energy in low fluence, and drastically decreased after peak in high irradiation energy and fluence; （4） implanted protons deposited in Pd as negative under the balance of electron population enhanced by proton irradiation and charge transfer.

Radiation Temperature Scaling Law for Gold Hohlraum Heated with Lasers at 0.35 mm Wavelength

We have carried out the hohlraum experiments about radiation temperature scaling on the Shenguang-Ⅱ （SG- Ⅱ） laser facility with eight laser beams of 0.35#m, pulse duration of about 1.0ns and total energy of 2000J. The reradiated x-ray flux through the laser entrance hole was measured using a soft x-ray spectrometer. The measured peak radiation temperature was 170eV for the standard hohlraum and 150 eV for the 1.5-scaled one. We have derived the radiation temperature scaling law, in which the laser hohlraum coupling efficiency is included. With an appropriate coupling efficiency, the coincidences between experimental and scaling hohlraum radiation temperatures are rather good.

Metrology for sub-Rayleigh-length target positioning in~10^(22)W/cm^(2)laser-plasma experiments

Tight focusing with very small f-numbers is necessary to achieve the highest at-focus irradiances.However,tight focusing imposes strong demands on precise target positioning in-focus to achieve the highest on-target irradiance We describe several near-infrared,visible,ultraviolet and soft and hard X-ray diagnostics employed in a~10^(22)W/cm^(2)laser±plasma experiment.We used nearly 10 J total energy femtosecond laser pulses focused into an approximately1.3-μm focal spot on 5±20μm thick stainless-steel targets.We discuss the applicability of these diagnostics to determine the best in-focus target position with approximately 5μm accuracy(i.e.,around half of the short Rayleigh length)and show that several diagnostics(in particular,3ωreflection and on-axis hard X-rays)can ensure this accuracy.We demonstrated target positioning within several micrometers from the focus,ensuring over 80%of the ideal peak laser intensity on-target.Our approach is relatively fast(it requires 10±20 laser shots)and does not rely on the coincidence of low-power and high-power focal planes.

Targets with cone-shaped microstructures from various materials for enhanced high-intensity laser-matter interaction

Targets with microstructured front surfaces have shown great potential in improving high-intensity laser–matter interaction.We present cone-shaped microstructures made out of silicon and titanium created by ultrashort laser pulse processing with different characteristics.In addition,we illustrate a process chain based on moulding to recreate the laser-processed samples out of polydimethylsiloxane,polystyrol and copper.With all described methods,samples of large sizes can be manufactured,therefore allowing time-efficient,cost-reduced and reliable ways to fabricate large quantities of identical targets.

EXPERIMENTS ON HIGH-GAIN SOFT X-RAY LASER IN Ne-LIKE Ge PLASMA

By means of a novel experimental design named the 'double target coupling', the ampli-fications of five lasing lines with wavelengths at 19.6, 23.2, 23.6, 24.7 and 28.6 nm fromthe 3p-3s transitions in Ne-like Ge plasmas were observed. The germanium slab targets wereirradiated by two opposite line-focused laser beams with the irradiance of 1.2×10^(13) W/cm^2.The values of GL (a gain-length product) for the lines at 23.2 and 23.6 nm exceed 13. Themeasurements of temporal resolution for the lasing lines were made with a soft X-ray streakcamera, and the measured results are presented. The divergence and refraction of X-ray laserbeam were also observed.

Investigation on non-LTE radiation emitted from a laser-irradiated Au disk

The spectral character of X-ray emitted from laser-irradiated gold disk is studied by using the one-dimensional non-LTE multigroup radiation transport hydrodynamics code RDMG. The applicability of the “three-temperature” model in which the radiation is described with thermal conduction approximation is checked. The simulation results show that the X-ray emitted from the laser-produced gold plasma is in non-LTE, and that the atom model has significant effect on the structure of X-ray spectrum. However, the plasma states, laser absorption efficiency and X-ray conversion efficiency, which are calculated with the “three-temperature” model, are almost the same as those with non-LTE multigroup radiation transport model. This fact indicates that the “three-temperature” model can be used to study plasma states and the energy distributions produced by a laser-irradiated high-Z target. This is meaningful to the 2-D or 3-D simulation.