Neutron irradiation influence on high-power thyristor device under fusion environment

Because of their economy and applicability,high-power thyristor devices are widely used in the power supply systems for large fusion devices.When high-dose neutrons produced by deuterium–tritium(D–T)fusion reactions are irradiated on a thyristor device for a long time,the electrical characteristics of the device change,which may eventually cause irreversible damage.In this study,with the thyristor switch of the commutation circuit in the quench protection system(QPS)of a fusion device as the study object,the relationship between the internal physical structure and external electrical parameters of the irradiated thyristor is established.Subsequently,a series of targeted thyristor physical simulations and neutron irradiation experiments are conducted to verify the accuracy of the theoretical analysis.In addition,the effect of irradiated thyristor electrical characteristic changes on the entire QPS is studied by accurate simulation,providing valuable guidelines for the maintenance and renovation of the QPS.

Irradiation effect on strain sensitivity coefficient of strain sensing fiber Bragg gratings

The effect of irradiation on the strain sensitivity coefficient of strain sensing fiber Bragg gratings （FBGs） has been investigated through experiments. FBGs were fabricated in single mode fibers with 3 tool% Ge-concentration in the core and with a H2-1oading treatment. In experiments, the FBGs were subjected to y-radiation exposures using a Co6~ source at a dose-rate of 25 Gy/min up to a total dose of 10.5 kGy. The GeO defect in fiber absorbs photons to form a GeE＇ defect; the interaction with H2 is a probable reason for the y-radiation sensitivity of gratings written in hydrogen loaded fibres, The effect mechanism of radiation on the strain sensitivity coefficient is similar to that of radiation on the temperature sensitivity coefficient. Radiation affects the effective index neff, which results in the change of the thermo-optic coefficient and the strain-optic coefficient. Irradiation can change the strain sensitivity coefficient of FBGs by 1.48%-2.71%, as well as changing the Bragg wavelength shift （BWS） by 22 pm-25 pm under a total dose of 10.5 kGy. Our research demonstrates that the effect of irradiation on the strain sensitivity coefficient of FBG is small and that strain sensing FBGs can work well in the radiation environment.

Effect of Irradiation on Crystallinity and Mechanical Properties of Ultrahigh-Molecular-Weight Polyethylene

Ultrahigh-molecular-weight polyethylene(UtlMWPE) has been irradiated (0-40 Mrad) with a Co^(60) source at room temperature under vacuum. Their crystallinity has been investigated by DSC and SAXS A significant increase of heat of fusion can be seen at low irradiation doses, which is attributed to crystallization caused by chain scission during the process of irradiation. It is also observed that thickness of lamellae changes with irradiation dose. Young's modulus has been improved significantly after irradiation at low doses.

Hot-Carrier Effects on Total Dose Irradiated 65 nm n-Type Metal-Oxide-Semiconductor Field-Effect Transistors

The influence of total dose irradiation on hot-carrier reliability of 65 nm n-type metal-oxide-semiconductor field- effect transistors （nMOSFETs） is investigated. Experimental results show that hot-carrier degradations on ir- radiated narrow channel nMOSFETs are greater than those without irradiation. The reason is attributed to radiation-induced charge trapping in shallow trench isolation （STI）. The electric field in the pinch-off region of the nMOSFET is enhanced by radiation-induced charge trapping in STI, resulting in a more severe hot-carrier effect.

Improvement of total-dose irradiation hardness of silicon-on-insulator materials by modifying the buried oxide layer with ion implantation

The hardening of the buried oxide （BOX） layer of separation by implanted oxygen （SIMOX） silicon-on-insulator （SOI） wafers against total-dose irradiation was investigated by implanting ions into the BOX layers. The tolerance to total-dose irradiation of the BOX layers was characterized by the comparison of the transfer characteristics of SOI NMOS transistors before and after irradiation to a total dose of 2.7 Mrad（SiO2）. The experimental results show that the implantation of silicon ions into the BOX layer can improve the tolerance of the BOX layers to total-dose irradiation. The investigation of the mechanism of the improvement suggests that the deep electron traps introduced by silicon implantation play an important role in the remarkable improvement in radiation hardness of SIMOX SOI wafers.

Protective Effects of Shikonin on Brain Injury Induced by Carbon Ion Beam Irradiation in Mice

Radiation encephalopathy is the main complication of cranial radiotherapy. It can cause necrosis of brain tissue and cognitive dysfunction. Our previous work had proved that a natural antioxidant shikonin possessed protective effect on cerebral ischemic injury. Here we investigated the effects of shikonin on carbon ion beam induced radiation brain injury in mice. Pretreatment with shikonin significantly increased the SOD and CAT activities and the ratio of GSH/GSSG in mouse brain tissues compared with irradiated group （P〈0.01）, while obviously reduced the MDA and PCO contents and the RO$ levels derived from of the brain mitochondria.

Effect of Treatment Temperature on Iron Nitride Foils Irradiated with Nitrogen Plasma

We investigated the effect of treatment temperature on the magnetic property of iron nitride foils irradiated with nitrogen plasma. The iron nitride foils irradiated with nitrogen plasma were composed of ε-Fe2/3N, γ'-Fe4N and γ nitrogen austenite in α-Fe of the matrix. The saturation magnetization of the iron nitride foils decreased with increasing the surface temperature. The coercive force of the iron nitride foils increased with increasing the surface temperature.

Irradiation Effects on the Retention of Hydrogen in Al_2O_3

Substantial defects are produced in Al2O3 by 4 MeV Au ion irradiation with a fluence of 4.4×10^15 cm^-2. Ruther- ford baekscattering spectrometry/channeling and cross-sectional transmission electron microscopy methods are used to investigate the irradiation damage. The 190keV H ions with a fuence of 1×10^17 cm^-2 are used for implanting pristine and Au ion irradiated Al2O3 to explore the irradiation damage effects on the hydrogen retention in Al2O3. The time-of-flight secondary ion mass spectrometry method is used to obtaJn the single hydrogen depth profile and ions mass spectra （IMS）, in which we find that implanted hydrogens interacted with defects produced by Au ion irradiation. In IMS, we also obtain the hydrogen retention at a certain depth. Comparing the hydrogen retention in different Al2O3 samples, it is concluded that the irradiation damage improves the tritium permeation resistance property of Al2O3 under given conditions. This result means that Al2O3 may strengthen its property of reduc/ng tritium permeation under the harsh irradiation environment in fusion reactors.

Irradiation effects of graphene and thin layer graphite induced by swift heavy ions

Graphene and thin graphite films deposited on SiO2/Si are irradiated by swift heavy ions(209Bi, 9.5 Me V/u) with the fluences in a range of 1011ions/cm2–1012ions/cm2 at room temperature. Both pristine and irradiated samples are investigated by Raman spectroscopy. For pristine graphite films, the 'blue shift' of 2D bond and the 'red shift' of G bond with the decrease of thickness are found in the Raman spectra. For both irradiated graphene and thin graphite films, the disorder-induced D peak and D' peak are detected at the fluence above a threshold Φth. The thinner the film, the lower the Φthis. In this work, the graphite films thicker than 60 nm reveal defect free via the absence of a D bond signal under the swift heavy ion irradiation till the fluence of 2.6 × 1012ions/cm2. For graphite films thinner than 6 nm, the area ratios between D peak and G peak increase sharply with reducing film thickness. It concludes that it is much easier to induce defects in thinner films than in thicker ones by swift heavy ions. The intensities of the D peak and D' peak increase with increasing ion fluence, which predicts the continuous impacting of swift heavy ions can lead to the increasing of defects in samples. Different defect types are detected in graphite films of different thickness values. The main defect types are discussed via the various intensity ratios between the D peak and D' peak(HD/HD).

Evolution of optical properties and molecular structure of PCBM films under proton irradiation

Low-energy proton irradiation effects on the optical properties and the molecular structure of phenyl-C_(61)-butyric acid methyl ester(PCBM)are studied in this work.The PCBM films are irradiated by 100-keV proton beams with fluences of 5×10^(12)p/cm^(2),5×10^(13)p/cm^(2),and 5×10^(14)p/cm^(2),respectively.The photoluminescence(PL)peaks of the post-irradiated PCBM films show a progressive decrease in the peak intensity as the proton fluences increase,which can be attributed to the deep defect levels induced by proton irradiation.Additionally,a slight blue-shift in the PL spectrum is also observed at a proton fluence of 5×10^(14)p/cm^(2).The underlying mechanism can be traced back to the lift of the lowest unoccupied molecular orbital(LUMO)level,which is caused by the attachment of methoxy radicals on ortho position of the phenyl ring in the post-irradiated PCBM structure.This work is of significance in understanding the radiation hardness and the damage mechanism of the PCBM film in radiation environments,which is essential before it is put into practical application in space.

Irradiation Effect on Second Harmonic Generation of Dyes Doped KDP Crystals

Most irradiation studies in the hydrogen bonded ferroelectrics have been concentrated on the transient defects induced by ionising radiation, such as ultraviolet （UV） light, where the defects are closely related to the optical properties. But heavy ion beam irradiation effects have rarely been studied. The structural, optical, and non-linear optical properties of the doped crystals were analyzed with the characterization studies, such as powder XRD, UV-Visible and second harmonic generation （SHG） measurements, respectively. The results for doped KDP crystal were compared with the results of the pure KDP crystals. The experiment results showed that Li^3＋ irradiation leads to the development of a well-defined surface H peak in dye doped KDP crystals. The stability of KDP single crystal was improved by doping organic dyes. The nano-islands of dye in KDP were likely to be dissolved and enhance the non-linear optical properties of these materials.

Influence of temperature and alloying elements on the threshold displacement energies in concentrated Ni-Fe-Cr alloys

Concentrated solid-solution alloys(CSAs)have demonstrated promising irradiation resistance depending on their compositions.Under irradiation,various defects can be produced.One of the most important parameters characterizing the defect production and the resulting defect number is the threshold displacement energies(Ed).In this work,we report the results of Ed values in a series of Ni-Fe-Cr concentrated solid solution alloys through molecular dynamics(MD)simulations.Based on several different empirical potentials,we show that the differences in the Ed values and its angular dependence are mainly due to the stiffness of the potential in the intermediate regime.The influences of different alloying elements and temperatures on Ed values in different CSAs are further evaluated by calculating the defect production probabilities.Our results suggest a limited influence of alloying elements and temperature on Ed values in concentrated alloys.Finally,we discuss the relationship between the primary damage and Ed values in different alloys.Overall,this work presents a thorough study on the Ed values in concentrated alloys,including the influence of empirical potentials,their angular dependence,temperature dependence,and effects on primary defect production.

Electron Microscopy Studies of Magnetron Sputtered YBa＿2Cu＿3O＿（7－δ） Thin Films

Magnetron sputtered YBa_2Cu_3O_(7-δ) superconducting thin films before and after ion implantation wereinvestigated by using high resolution electron microscopy and scanning electron microscopy. Very goodepitaxial but defect-containing, effectively single crystalline films are demonstrated. The defect density concerning (001 ) plane decreases with increasing grown thickness of the film.

OKMC simulation of vacancy-enhanced Cu solute segregation affected by temperature/irradiation in the Fe–Cu system

The effects of annealing and irradiation on the evolution of Cu clusters in a-Fe are investigated using object kinetic Monte Carlo simulations.In our model,vacancies act as carriers for chemical species via thermally activated diffusion jumps,thus playing an important role in solute diffusion.At the end of the Cu cluster evolution,the simulations of the average radius and number density of the clusters are consistent with the experimental data,which indicates that the proposed simulation model is applicable and effective.For the simulation of the annealing process,it is found that the evolution of the cluster size roughly follows the 1/2 time power law with the increase in radius during the growth phase and the 1/3 time power law during the coarsening phase.In addition,the main difference between neutron and ion irradiation is the growth and evolution process of the copper-vacancy clusters.The aggregation of vacancy clusters under ion irradiation suppresses the migration and coarsening of the clusters,which ultimately leads to a smaller average radius of the copper clusters.Our proposed simulation model can supplement experimental analyses and provide a detailed evolution mechanism of vacancy-enhanced precipitation,thereby providing a foundation for other elemental precipitation research.

Lattice damage in InGaN induced by swift heavy ion irradiation

The microstructural responses of In_(0.32)Ga_(0.68)N and In_(0.9)Ga_(0.1)N films to 2.25 GeV Xe ion irradiation have been investigated using x-ray diffraction,Raman scattering,ion channeling and transmission electron microscopy.It was found that the In-rich In_(0.9)Ga_(0.1)N is more susceptible to irradiation than the Ga-rich In_(0.32)Ga_(0.68)N.Xe ion irradiation with a fluence of 7×10^(11)ions·cm^(-2)leads to little damage in In_(0.32)Ga_(0.68)N but an obvious lattice expansion in In_(0.9)Ga_(0.1)N.The level of lattice disorder in In_(0.9)Ga_(0.1)N increases after irradiation,due to the huge electronic energy deposition of the incident Xe ions.However,no Xe ion tracks were observed to be formed,which is attributed to the very high velocity of 2.25 Ge V Xe ions.Point defects and/or small defect clusters are probably the dominant defect type in Xe-irradiated In_(0.9)Ga_(0.1)N.

Transmission Electron Microscopy Investigation of the Ar^+ Ion Irradiation Effect in Semiconductor GaAs

Room temperature irradiation effect of GaAs compound semiconductor by 100 keV Ar+ ions has been systematically studied by means of transmission electron microscopy. The dose dependenceoof the Ar+ ion irradiation and room temperature annealing effects have been investigated. The experimental results show that the structure of GaAs transforms from perfect crystalline through weakly and severely damaged crystalline to amorphous states with the increase of the irradiation dose and the damaged states are changed during room temperature annealing.

Loss prediction of three-level amplified spontaneous emission sources in radiation environment

A model of three-level amplified spontaneous emission(ASE)sources,considering radiation effect,is proposed to predict radiation induced loss of output power in radiation environment.Radiation absorption parameters of ASE sources model are obtained by the fitting of color centers generation and recovery process of gain loss data at lower dose rate.Gain loss data at higher dose is applied for self-validating.This model takes both the influence of erbium ions absorption and photon bleaching effect into consideration,which makes the prediction of different dose and dose rate more accurate and flexible.The fitness value between ASE model and gain loss data is 99.98%,which also satisfies the extrapolation at the low dose rate.The method and model may serve as a valuable tool to predict ASE performance in harsh environment.

ORIGIN FOR IRRADIATION EFFECT OF 0.56 GeV C^(6+) ON CaVSn:YIG

This paper presents numerous physical characteristics of Ca, V, Sn doped yttrium iron garnet (CaVSn:YIG) irradiated with 0.56GeV carbon ions delivered by the Heavy Ion Research Facility of Lanzhou (HIRFL). The reason for change of the magnetic properties of the samples induced by energetic carbon ions bombardment is discussed. By comparison of this results with the irradiation effects of YIG induced by energetic argon, krypton and xenon obtained on the GANIL, Caen,France, it is concluded that the irradiation effect of 0.56 GeV C6+ on CaVSn.YIG arises from the electronic energy losses.

IRRADIATION EFFECT OF 0．56 GeV C^（6＋） on Y_（1．6）Ca_（1．4）V_（0．45）Sn_（0．5）Fe_（4．05）O_（12）

Y1.6Ca1.4V 0.45Sn0.5Fe4.05O12 is irradiated by 0.56 GeV carbon ion. The irradiation effect is investigated by Mossbauer spectroscopy. The irradiation results in an isotropic distribution of the hyperfine magnetic field. The hyperfine magnetic fields decrease after the irradiation due to the change of supertransferred field. After the irradiation, the chain Fe(a)-oxygen-Fe(d) become longer and it leads to decrease of the supertransferred field.

Effect of ultraviolet blood irradiation and oxygenation on nerve function and function of the red blood cell membrane pump in patients with acute cerebral infarction

BACKGROUND： Ultraviolet blood irradiation and oxygenation （UBIO） has obtained better clinical effect in treating acute cerebral infarction, but the mechanism underlying this effect remains unclear. OBJECTIVE： To observe the effect of UBIO on the nerve function and activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase activities on the red blood cell （RBC） membrane of patients with acute cerebral infarction. DESIGN： A randomized and controlled study.SETTING： Department of Neurology, Xiangfan Central Hospital.PARTICIPANTS： From January 2000 to December 2001, excluding those above 70 years old, 58 cases of 700 patients with acute cerebral infarction admitted in the Department of Neurology, Xiangfan Central Hospital, were recruited and divided into two groups according to the random number table： UBIO treated group （n=28）, including 17 males and 11 females, aged 40-68 years; and control group （n=30）, including 20 males and 10 females, aged 44-69 years. All the patients agreed to participate in the therapeutic program and detected items. The general informations were comparable without obvious differences between the two groups （P 〉 0.05）.METHODS： ① The patients in both groups received routine treatments, besides, those in the UBIO treated group were given UBIO treatment by using the XL-200 type therapeutic apparatus produced in Shijiazhuang, whose ultraviolet wave was set at 253.7 nm with the energy density of 0.568 J/m^2 per second, UBIO treatment started from the second day after admission, once every other day, with a single course consisting of 5-7 treatments. ② In the UBIO treated group, the venous blood was sampled before and after the first, third and the completion of the treatment course respectively, the venous blood was taken at each corresponding time point in the control group. After centrifugation of the blood at 10 000 rounds per minute, the RBC membrane was separated and then the activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase were detected by means of phosphorus determination.③ The nerve function was scored before and after treatment in both groups with European stroke scale, which included 13 items, the total score was 0-100 points, the higher the score, the better the nerve function. MAIN OUTCOME MEASURES ：①Score of European stroke scale before and after treatment in both groups.② Comparison of the activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase on RBC membrane between the two groups before treatment and after the first, third and the completion of the treatment. RESULTS： All the 58 patients with cerebral infarction were involved in the analysis of results.① The score of European stroke scale had no obvious difference between the two groups [（49.31±11.48）, （50.58±12.63）, P 〉 0.05], and it was obviously higher in the UBIO treated group than in the control group after treatment [84.66±13.75）, （77.05±11.17）, P 〈 0.05].②The activity of K^＋-Na^＋-ATPase on RBC membrane in the UBIO treated group was significantly increased after the first and third treatment as compared with before treatment [（31.56±19.25）, （27.64±15.83）, （17.67±13.83）, P 〈 0.01], it was still higher after the completion of the treatment than before treatment without obvious difference [（20.86±14.53）, P 〉 0.05]. After the first and third treatment, it was obviously higher in the UBIO treated group than in the control group [19.31±11.88）, （17.44±10.42）, P 〈 0.01]. ③ In the UBIO treated group, Ca2^＋-Mg2^＋-ATPase activity on RBC membrane significantly increased after the first treatment and remained higher than the pre-treatment level throughout the treatment [（27.49±14.72）, （17.41±4.82）, P 〈 0.01]. The activity of Ca2^＋-Mg2^＋-ATPase on RBC membrane was markedly higher in the UBIO treated group than in the control group after after the first, third and the completion of treatment respectively [（24.83±12.88）, （17.70±5.69）; （28.08±13.44）, （16.32±5.29）; （17.42±6.04）, P〈 0.05-0.01]. CONCLUSION： The effect of UBIO treatment against acute cerebral infarction may be mediated by the increased K^＋-Na^＋ ATPase and Ca2^＋-Mg2^＋-ATPase activities on RBC membrane, which enhances the RBC transformation ability so as to lower RBC aggregation and correct high blood viscosity.