Aluminum X-ray mass-ablation rate measurements

Measurements of the mass ablation rate of aluminum(Al)have been completed at the Omega Laser Facility.These measurements show that the mass-ablation rate of Al is higher than plastic(CH),comparable to high density carbon(HDC),and lower than beryllium.The mass-ablation rate is consistent with predictions using a 1D Lagrangian code,Helios.The results suggest Al capsules have a reasonable ablation pressure even with a higher albedo than beryllium or carbon ablators and further investigation into the viability of Al capsules for ignition should be pursued.

Effect of organo-modified montmorillonite nanoclay on mechanical,thermal and ablation behavior of carbon fiber/phenolic resin composites

The mechanical,thermal and ablation properties of carbon phenolic(C-Ph)composites(Type-I)reinforced with different weight percentages of organo-modified montmorillonite(o-MMT)nanoclay have been studied experimentally.Ball milling was used to disperse different weight(wt)percentages(0,1,2,4,6 wt.%)of nanoclay into phenolic resin.Viscosity changes to resin due to nanoclay was studied.On the other hand,nanoclay added phenolic matrix composites(Type-II)were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser(TGA).This data was used to understand the mechanical,thermal and ablation properties of Type-I composites.Inter laminar shear strength(ILSS),flexural strength and flexural modulus of Type I composites increased by about 29%,12%and 7%respectively at2 wt.%addition of nanoclay beyond which these properties decreased.This was attributed to reduced fiber volume fraction(%Vf)of Type-I composites due to nanoclay addition at such high loadings.Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux(125 W/cm^(2))and high heat flux levels(500 W/cm^(2)).Mass ablation rates have increased at both flux levels marginally up to 2 wt.%addition of nanoclay beyond which it has increased significantly.This is in contrast to increased thermal stability observed for Type-I and Type-II composites up to 2 wt.%addition of nanoclay.Increased ablation rates due to nanoclay addition was attributed to higher insulation efficiency of nanolcay,which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.

Experimental Investigation on Ablation Characteristic of EPDM Insulator in Different Gas Environments

Some ablation experiments of Ethylene-Propylene-Diene Monomer(EPDM)insulator were carried out in quasi-static low temperature gas environment,gas-phase environment,two-phase environment with Al2O3 grain and high concentration Al2O3 grain gas environments.Their charring ablation rate,thickness,surface morphology and main ingredient of the charring layer were analyzed.The experiment results show that the main influent factors for the charring ablation rate are the gas temperature,grain concentration and state of grain impact;the main influent factors for the charring layer thickness are the gas velocity and environment pressure;and the process of SiO2 migrating in the charring layer occur commonly in different gas environments.They provide a foundation for the ablation mechanism research and modeling of EPDM insulator.

Observation of hydrogen pellet ablation material flow by tomography

An Ha emission measurement array with 25 detection channels has been built on HL-1M tokamak. Reconstruction maps of Ha emission distribution in plasma cross-section have been obtained by using tomography, with a hydrogen pellet injected into the plasma. The dimension, the shape and the rotation characteristic of the cross-section of the pellet ablation material flow tube have been observed. These results have been analysed and explained tentatively by using the ‘tail＇ model and the linear expansion model.

Impact of Real-Time Contrast-Enhanced Ultrasound-Guided Radiofrequency Ablation on Progression-Free Survival in Patients with Hepatocellular Carcinoma:a Retrospective Case-Control Study

Objective To compare the value of contrast-enhanced ultrasound(CEUS)and conventional ultrasound(US)during radiofrequency ablation(RFA)for the treatment of hepatocellular carcinoma(HCC)≥3.0 cm in diameter.Methods A total of 149 HCC patients treated with RFA guided by either CEUS or conventional US between January 2012 and June 2013 were retrospectively analyzed.Patients were divided into different groups based on the type of ultrasound guidance(CEUS or conventional US)and tumor volume(diameter<3.0 or≥3.0 cm).The progressionfree survival(PFS)and complete ablation rates were compared between groups,and risk factors for the PFS were investigated.Results Seventy four patients received CEUS-guided RFA,and conventional US was performed in 75 patients.Among patients with a tumor<3.0 cm,the PFS and complete ablation rates were similar.However,for patients with a tumor≥3.0 cm,those treated with CEUS had a significantly longer PFS(17.3 vs.3.1 months,HR=2.73;95%CI,1.28~5.81;P=0.007)and higher complete ablation rates at 6-and 12-month post-treatment(87.5%vs.57.7%,P=0.042;75.0%vs.38.5%,P=0.009,respectively)than those treated with conventional US-guided RFA.The type of treatment(P=0.024)and maximum tumour size(P=0.011)were both found to be independent factors associated with the PFS.Conclusion Compared with conventional US,CEUS is more effective for guiding RFA in patients with HCC≥3.0 cm.CEUS-guided RFA could target HCC more accurately,and its ability to immediately detect any residual tumor during RFA might contribute to an increase in complete ablation rates and reduced progression.

Fine tuning of the default depth and rate of ablation of the epithelium in customized trans-epithelial one-step superficial refractive excimer laser ablation

Purpose:To fine tune the default depth and rate of ablation of the epithelium in cTen^(TM) customized trans-epithelial one-step superficial refractive surgery by the comparison between the attempted post-operative ideal corneal shape and the achieved corneal shape.Methods:88 consecutive eyes in 64 patients undergoing trans-epithelial superficial excimer ablation using the iVis laser Suite for either myopic/astigmatic or hyperopic/astigmatic refractive error.Each patient had at least 3 months of post-operative follow-up.Topographic examination of all eyes was carried out pre-operatively and at least 3 months post-operatively using the Precisio^(TM) surgical topographer.The comparison of these two measurements yielded values for depth,volumes and rates of ablated corneal tissue.By determining the different ablation rates of stroma and epithelium,a refinement of the depth of epithelium to be removed and a refinement of the stromal ablation were calculated.The mathematical model was applied on each one of the 88 clinical cases and the parameters for the fine tuning of the default depth and rate of ablation of the epithelium were determined using the least squares method.Results:The calculated pure stromal ablation rate was less than the average epithelium/stroma ablation rate used in planning the treatments by a factor of 0.96.The epithelial thickness predefined ablation assumption used to plan removal of the epithelium was adjusted considering the measured ablation and a radial adjustment function established for the fine tuning of the laser radial efficiency and allowing for the normal thickening of the epithelium in the peripheral cornea.From a clinical point of view,this methodology produces an improvement of the efficacy and a reduction of the variance of the clinical results.Conclusion:Comparison of accurately measured pre and postoperative topographies yields accurately established ablation rates of stroma and epithelium in trans-epithelial one step superficial ablation.

Growth of Niobium Thin Films on Si Substrates by Pulsed Nd:YAG Laser Deposition

The growth of Nb thin films on Si（100） substrates by different laser fluences （4-15 J/cm2） was reported, The pulsed Nd：YAG laser deposition （PLD） under influence of laser fluence on ablation rate and deposition rate was discussed. X-ray diffraction （XRD） investigations of the deposited films showed an amorphous structure. The droplet density on the film surface observed by scanning electron microscopy （SEM） analyses was extremely low. It was experimentally proved that the droplets on the film surface originated from liquid phase on the target surface, Profilometric measurements of the deposited Nb films revealed a substantial asymmetry in the film thickness related to the plume deflection effect. The measured electrical resistivity of the Nb film was higher than that of high purity Nb bulk. The present investigations of ablation and deposition process of Nb thin films are related to its potential application in superconducting radio-frequency （SRF） cavities.

Microperforation of the human nail plate by radiation of erbium lasers

The nail plate forms a barrier that limits the effectiveness of drug delivery in the treatment of nail diseases and prevents the outflow of fluid in the case of subungual hematoma formation. Microperforation of the nail plate through laser radiation can increase the effectiveness of drug delivery and ensure the possibility of blood outflow. This study detected and identified the type and threshold of effects that arise from exposing the nail plate to Yb,Er： Glass （λ = 1.54 μm） and Er：YLF （λ= 2.81 μm） laser radiation. The rate and efficiency of nail plate ablation by the radiation of these lasers were studied. The effect of the storage time of a freshly extracted nail plate in open air on its ablation rate by Er：YLF （ λ=2.81 μm） laser radiation was also investigated. The impact of the Yb,Er：Glass and Er：YLF laser pulses on the nail plate caused bleaching, carbonization, ablation with microcrater formation, and microperforation. The laser energy densities WE （thresholds） required for these effects were determined. The maximum ablation rate for Yb,Er：Glass laser radiation was 8 μm/pulse at WE = 91 ±2 J/cm2, whereas that for Er：YLF laser radiation was 12 μm/ pulse at WE= 10.5＋0.5 J/cm2. The maximum ablation efficiency for Yb,Er：Glass laser radiation was 0.1 μm/mJ at Ws = 10.5±0.5 J/cm2, whereas that for Er：YLF laser radiation was 4.6 μm/mJ at WE = 5.3±0.3 J/cm2. The laser ablation rate depends on the storage time and conditions of the freshly extracted nail plate. For example, when exposed to Er：YLF laser radiation, the laser ablation rate decreased by half from the initial maximum value in 96 h of air storage and returned to the initial value after 1 h of storage in distilled water.