Effect of high-energy electron irradiation on forsterite laser crystals

The effect of 21-MeV electron irradiation on the optical absorption characteristics of Czochralski-grown forsterite (Mg₂SiO₄) single crystals (both undoped and chromium-doped) has been investigated. The irradiation is found to induce additional optical absorption (AOA) in the crystals in the range of 225–1200 nm due to the formation of color centers based on intrinsic host point defects and the change in the oxidation state of chromium ions. The AOA spectra have been decomposed into elementary bands. The influence of the chromium concentration in crystals, the oxygen content in the growth atmosphere, and additional doping with lithium on the behavior of these bands has been analyzed. A possible structure of the color centers responsible for the AOA is discussed. It is shown that the electron irradiation somewhat decreases the intensity of the characteristic absorption bands of tri- and tetravalent chromium ions and gives rise to a new absorption band in Mg₂SiO₄:Cr and Mg₂SiO₄:Cr,Li crystals heavily doped with chromium.     

Effect of gamma irradiation on undoped and uranium doped calcium fluoride crystals

Color centers in undoped and U³⁺-doped CaF₂ crystals induced by γ-irradiation with different doses were studied by differential absorption and Raman spectra. Multiple color centers and conversion among them were caused in undoped CaF₂ with the creation of radiation defects. In U³⁺:CaF₂ crystal, trivalent uranium was demonstrated to act as hole trap in the process of γ-irradiation, which was ionized to tetravalent. This process was accompanied by the formation of F₂⁺ centers, but without additional background absorption due to radiation defects.     

伽马辐照对掺镱光纤材料特性影响的研究

掺镱光纤是高功率激光器的核心材料,但在高能射线辐照后其应用性能会显著下降,因此有必要对掺镱光纤材料在辐照环境下的性能变化进行深入研究。采用改进型化学气相沉积法结合稀土螯合物掺杂制备了系列光纤预制棒及光纤,测试了光纤在不同剂量下射线辐照前后的高功率输出性能,以及光纤预制棒辐照前后的吸收光谱及镱离子荧光寿命。结果表明：小剂量辐照后掺镱光纤的高功率输出显著下降,通过预制棒吸收光谱可看出主要是因为伽马辐照后使掺镱光纤材料中Al的相关缺陷浓度增多,在可见光区域吸收损耗增加。Ce离子的掺杂通过缓减辐致铝氧空位中心（Al-OHC）色心缺陷的增加,减少Yb离子荧光寿命的下降,可在一定程度上抑制高功率掺镱光纤的辐致暗化。     

Effect of gamma irradiation on the polymer electrolyte PEO-NH4ClO4

Irradiation affects the structures of materials at different scales, thus changing physical and chemical properties. We study here the effect of gamma irradiation at different doses on the polymer electrolyte PEO-NH₄ClO₄. Optical micrographs show cracks in the irradiated samples and impedance spectroscopy measurements indicate reduced ion-conductivity at room temperature but slight enhancement at higher temperature. At high frequencies, the real part of the admittance shows a power-law variation; the exponent, which is a measure of self-similarity of the structure, is reduced on irradiation. The overall results point to a more disordered structure at higher radiation doses.     

Influence of 60Co gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol crystals

In this article, effect of gamma irradiation on the structural and optical properties of 2-aminopyridinium 4-nitrophenolate 4-nitrophenol (2AP4N) has been reported. The grown crystals of 2AP4N were exposed to ⁶⁰Co gamma rays with a dose of 50 kGy and 100 kGy. The radiation-induced effects were analyzed using X-ray diffraction, FT-IR, UV–visible, photoluminescence techniques. The refractive index was determined using a long arm spectrometer. The structural properties of the pristine and irradiated crystals were studied using powder XRD. The peak intensity decrease after irradiation may be attributed to the formation of point defects. The UV visible study reveals that the energy gap has decreased after irradiation and then has increased for the higher dose. The intensity variation in the PL spectra is due to colour center mechanism. The SHG efficiency of 2AP4N crystals was found to be unaffected by gamma irradiation.     

Influence of electron irradiation on optical properties of scheelite crystals

Optical transmission spectra of nominally pure BaWO₄ and SrMoO₄ and doped BaWO₄:La³⁺ and SrMoO₄:Yb³⁺ crystals are measured after irradiation with a 6-MeV 5-μs pulse electron beam at room temperature. It is shown that the irradiation effect strongly depends on the crystals composition, the type, and the concentrations of doping ions. Possible mechanisms responsible for the spectra transformations and the correspondent formulas of chemical reactions addressing these mechanisms are proposed.     

Formation of nanodefects in LiF crystals under gamma irradiation

The absorption spectra, photoluminescence spectra, and microhardness of LiF crystals exposed to gamma radiation from a shutdown reactor and a ⁶⁰Co source at a dose rate of 7.65 Gy/s are investigated. The structure of these crystals is determined using x-ray diffraction analysis. It is revealed that the Li sublattice contains not only point and complex radiation-induced defects but also 28-nm LiOH particles induced by gamma radiation. It is shown that the formation of defects occurs more efficiently upon exposure to radiation from a shutdown reactor than from a ⁶⁰Co source.     

Positron annihilation in alkali-halide crystals after electron irradiation

The effect of electron beam irradiation on the positron annihilation in KCl, KBr, NaCl single crystals was investigated. The narrowing of the angular correlation curves increases up to the saturation value with the absorbed radiation dose. The shape of the received narrow components differs from the narrow component measured in the additively colored samples. This phenomenon shows the considerable influence of the hole centres upon the positron annihilation in ionic crystals. Paper presented at 3rd Internat. Conf. Positron Annihilation, Otaniemi, Finland (August 1973).     

Observations of elastic and quasi-elastic nuclear gamma resonance absorption in hemoglobin crystals

Mössbauer spectra of carbonmonoxy-liganded human hemoglobin crystals, selectively enriched with ⁵⁷Fe in the α-chains, were measured at 260 K and at 101 K a quadrupole doublet of lorentzians with the usual, narrow line width was observed, while at 260 K a superposition was observed of one doublet with a narrow and a second one with a broadened line width. The narrow doublet is attributed to elastic absorption processes and the broadened doublet to quasi-elastic ones. The spectrum at 260 K indicates that fluctuational processes between conformational substates of the quarternary “R” structure do exist.     

The effect of electron irradiation on some alkali halide single crystals

The investigated alkali halides (Nacl, KCl, RbCl and CsCl) decompose under electron irradiation into alkali metal colloids and chlorine gas. This decomposition is a special case of radiation damage effects, which strongly influence the crystalline structure and the physical properties of the crystals under investigation. The decomposition process consists of the breaking up of the single crystalline material into polycrystalline aggregates; at the same time cavities, or larger aggregates of vacancies are produced, which, together with the boundaries of the polycrystalline aggregates, serve as the nuclei of growing dark platelets, which appear to be precipitated alkali metal crystals.We wish to thank Prof. Dr. S. Lengyel, director of our laboratory, for his helpful assistance in securing the necessary means, and his interest. We further thank Mrs. L. Fülöp, who carried out the electron-microscopic preparatory work and helped most effectively in taking and evaluating the electron micrograms and diffractograms. Finally we wish to thank R. Voszka, head assistant of the University, and J. Kis, research physicist, for valuable discussions.     

Effect of electron irradiation on InSb microcrystals

The results of experimental studies of electrophysical properties of heavily doped n-InSb whiskers exposed to electron irradiation (13 MeV, 300 K) are reported. The limiting electrophysical parameters and the problem of the Fermi-level pinning in irradiated InSb are discussed. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 42–45, February, 2006.     

电子辐照条件下初始电位对介质材料表面电位衰减特性的影响

为了研究航天器介质材料表面不同电位初始值对表面电位衰减特性的影响。利用航天器带电地面模拟实验设备对聚酰亚胺和聚四氟乙烯介质材料充电到不同电位值,然后关闭电子枪,用电位计测量介质材料表面电位的衰减曲线,并从理论上对cross-over现象进行分析。介质材料初始电位值越大,则表面电位衰减速度越快,且在一定的时间段内电位衰减效率随初始电位值的增大而变大;在相同的真空度条件下,对于初始电位值之和相等的两组衰减曲线,初始电位值之间差值较小的一组衰减曲线更容易出现cross-over现象;出现cross-over现象的时间和电子的迁移率相关,对于相同的两个初始电位,迁移率越大的材料则出现cross-over现象的时间越短,电位衰减会更快。航天器介质材料表面充电电位越大则衰减速度越快,在一定时间的衰减效率越高。     

Anomalies of heat capacity and spontaneous polarization of nonstoichiometric KTiOPO4 crystals in the low-temperature region

The data of experiments that characterize the dependences of the unit cell volume, heat capacity, and spontaneous polarization of a nonstoichiometric KTiOPO₄ sample are presented for the low-temperature region. It is shown that the influence of the electric field leads to variation in the sample nonstoichiometry, which is characterized by the appearance of anomalous behavior of spontaneous polarization in the region below 30 K. This experimental fact is associated with the appearance of the donor-acceptor pairs possessing the dipole moment. As the temperature increases, they gradually dissociate with the subsequent appearance of the cationic component of conduction.     

Effect of electron irradiation of ZnGeP2 single crystals on terahertz losses in a wide temperature range

Physics of the Solid State - The reflection and transmission spectra of ZnGeP2 single crystals irradiated with 4-MeV electrons have been measured in the frequency range of 5-5000 cm−1 at...     

Influence of gamma and gamma-neutron irradiation on the optical properties of LiNbO3 single crystals

The influence of radiation effects (gamma and mixed gamma-neutron irradiation) on the refractive indices and optical inhomogeneity of lithium niobate single crystals of congruent composition is investigated. The temperature dependences of the optical characteristics of the irradiated crystals exhibit a number of anomalies in the temperature range 20–400°C.     

4H-SiC探测器的γ辐照影响研究

为研究4H-SiC探测器的抗γ辐照性能,使用40万Ci级的⁶⁰Co源对4H-SiC探测器进行了数次辐照,累积辐照剂量最大为1 MGy(Si),并在辐照后对4H-SiC的性能进行了测试。随着累积辐照剂量增加,4H-SiC探测器的正向电流增大,而反向电流恰好相反;根据4H-SiC探测器的正向I-V曲线可提取理想因子和肖特基势垒,理想因子从1.87增加到2.18,肖特基势垒从1.93 V减小至1.69 V;4H-SiC探测器对²⁴¹Am源产生的α粒子进行探测时,探测器的电荷收集率从95.65%退化到93.55%,测得能谱的能量分辨率由1.81%退化到2.32%。4H-SiC探测器在受到1 MGy(Si)的γ辐照后,与未受到辐照时相比,在探测能量为5.486 MeV的α粒子时能量分辨率和电荷收集率仅退化了28.18%和2.2%,仍具备优良的探测性能。     

Effect of gamma irradiation on photoconversion characteristics of metal/gallium arsenide barrier structures with textured interface

The effect of ⁶⁰Co gamma irradiation at doses of 10³-2×10⁵ Gy on the photoconversion and dark I-V characteristics of Au/GaAs surface-barrier solar cells (SCs) is studied. The morphology of the interface microrelief is varied to reach the highest photoconversion efficiency. Of the two types of microrelief morphology (dendritic and quasi-grating) obtained by the chemical anisotropic etching of n-(100)GaAs, the latter is more promising, particularly for SCs designed for space application, since the associated SCs offer higher efficiency and radiation resistance.     

Effect of gamma irradiation on hydrothermally synthesized barium titanate nanoparticles

The effect of gamma irradiation on hydrothermally synthesized BaTiO₃ nanoparticles has been investigated. Gamma irradiation was carried out at room temperature from 0, 50, 100, 150, 200?kGy to a maximum dose up to 250?kGy, source being ⁶⁰Co gamma radiations. The structure, size and chemical changes of the BaTiO₃ were studied using X-ray diffraction, Fourier-transform infrared spectrophotometry (FTIR) techniques and scanning electron microscopy (SEM). The optical band gap has been computed by UV–Visible spectroscopy data. From the results obtained, it is evident that the gamma irradiation increases the crystallinity, whereas the particle size of BaTiO₃ nanoparticles is altered. UV–Visible spectroscopy shows a noticeable change in the energy band gap due to gamma irradiation. Significant changes in anharmonicity constant computed using FTIR data due to irradiation has been observed. SEM shows the size and deviation from uniformity of particles.