The effects of fast neutron irradiation on oxygen in Czochralski silicon

The effects of fast neutron irradiation on oxygen atoms in Czochralski silicon (CZ-Si) are investigated systemically by using Fourier transform infrared (FTIR) spectrometer and positron annihilation technique (PAT). Through isochronal annealing, it is found that the trend of variation in interstitial oxygen concentration ([O_i]) in fast neutrons irradiated CZ-Si fluctuates largely with temperature increasing, especially between 500 and 700℃. After the CZ-Si is annealed at 600℃, the V₄ appearing as three-dimensional vacancy clusters causes the formation of the molecule-like oxygen clusters, and more importantly these dimers with small binding energies (0.1--1.0eV) can diffuse into the Si lattices more easily than single oxygen atoms, thereby leading to the strong oxygen agglomerations. When the CZ-Si is annealed at temperature increasing up to 700℃, three-dimensional vacancy clusters disappear and the oxygen agglomerations decompose into single oxygen atoms (O) at interstitial sites. Results from FTIR spectrometer and PAT provide an insight into the nature of the [O_i] at temperatures between 500 and 700℃. It turns out that the large fluctuation of [O_i] after short-time annealing from 500 to 700℃ results from the transformation of fast neutron irradiation defects.     

Effect of fast neutron irradiation on the structural and optical properties of Makrofol DE 1-1 CC polycarbonate

Samples from sheets of the polymeric material Makrofol DE 1-1 CC have been exposed to neutrons of incident energy in the range of 0.8–19.2 MeV. The modifications induced in Makrofol samples due to neutron irradiation have been studied through different characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, intrinsic viscosity, refractive index and color difference studies. Infrared spectroscopy indicated that cross-linking is the dominant mechanism in the energy range of 2.3–19.2 MeV. The cross-linking reported by FTIR spectroscopy destroyed the degree of ordering in the Makrofol samples, as revealed by the XRD technique. Also, this cross-linking led to an increase in the values of intrinsic viscosity from 0.41 to 0.68 at 28 °C, indicating an increase in the average molecular mass, associated with an increase in the refractive index. Additionally, the non-irradiated Makrofol samples showed significant color sensitivity toward neutron irradiation. The sensitivity toward neutron irradiation can be seen by the change in the blue color component of the non-irradiated Makrofol film to yellow after the samples are exposed to neutrons up to 19.2 MeV. This is accompanied by a net increase in the darkness of the samples.     

质子与中子辐照对电荷耦合器件暗信号参数的影响及其效应分析

对科学级电荷耦合器件(charge-coupled device, CCD)进行了质子和中子辐照试验及退火试验, 应用蒙特卡洛方法计算了质子和中子在CCD中的能量沉积, 分析了器件的辐射损伤机理. 仿真计算了N⁺埋层内沉积的位移损伤剂量, 辐照与退火试验过程中主要考察暗信号的变化规律. 研究结果显示, 质子与中子辐照均会引发暗信号退化, 其退化的规律与位移损伤剂量变化一致; 退火后, 质子辐照所致CCD暗信号大幅度恢复, 其体暗信号增加量占总暗信号增加量的比例最多为22%; 中子辐照引发的暗信号增长主要为体暗信号. 质子和中子在N⁺埋层产生相同位移损伤剂量的情况下, 两者导致的体暗信号增长量相同, 质子与中子辐照产生的体缺陷对体暗信号增长的贡献是同质的.     

The effect of thermal reactor neutron irradiation on semi-insulating GaN

Semi-insulating Gallium nitride was irradiated by fast and thermal neutrons with fluences from 10¹⁴ to 10¹⁶ n/cm². Depth-resolved cathodoluminescence spectroscopy was used to determine defects changes before and after irradiation. The results revealed two kinds of defects affected near-band emission recombination from two opposite directions. One was attributed to irradiation-induced N vacancies that contribute to near-band emission recombination. Another was attributed to irradiation-induced deep level defects that contribute to sub-band gap recombination and thus decrease the near-band emission recombination.     

光电耦合器的反应堆中子辐射效应

 选择3种典型光电耦合器开展了反应堆中子辐照实验,中子注量为3×10¹¹~5×10¹²cm^-2时,位移效应导致电流传输比下降,饱和压降提高。发光器件相同,探测器为Si PIN光电二极管的光电耦合器比探测器为Si NPN光敏晶体管的光电耦合器的初始电流传输比要小,但其抗位移损伤能力更强。探测器均为Si NPN光敏晶体管,发光器件为异质结LED要比硅两性掺杂LED的光电耦合器的电流传输比抗位移损伤能力提高2个量级;以光敏晶体管为探测器的光电耦合器,在较大的正向电流和输出负载电阻条件下工作可提高抗辐射水平。此外,光电耦合器的位移损伤存在加电退火效应。     

Effect of simultaneous helium implantation on the microstructure evolution of Inconel X-750 superalloy during dual-beam irradiation

This study focuses on investigation into the effect of helium implantation on microstructure evolution in Inconel X-750 superalloy during dual-beam (Ni⁺/He⁺) irradiation. The 1 MeV Ni⁺ ions with the damage rate of 10^?3 dpa/s as well as 15 keV He⁺ ions using rate of 200 appm/dpa were simultaneously employed to irradiate specimens at 400 °C to different doses. Microstructure characterization has been conducted using high-resolution analytical transmission electron microscopy (TEM). The TEM results show that simultaneous helium injection has significant influence on irradiation-induced microstructural changes. The disordering of γ′ (Ni₃ (Al, Ti)) precipitates shows noticeable delay in dose level compared to mono heavy ion irradiation, which is attributed to the effect of helium on promoting the dynamic reordering process. In contrast to previous studies on single-beam ion irradiation, in which no cavities were reported even at high doses, very small (2–5 nm) cavities were detected after irradiation to 5 dpa, which proved that helium plays crucial role in cavity formation. TEM characterization also indicates that the helium implantation affects the development of dislocation loops during irradiation. Large 1/3 〈1?1?1〉 Frank loops in the size of 10–20 nm developed during irradiation at 400 °C, whereas similar big loops detected at higher irradiation temperature (500 °C) during sole ion irradiation. This implies that the effect of helium on trapping the vacancies can help to develop the interstitial Frank loops at lower irradiation temperatures.     

光电耦合器的反应堆中子辐射效应

选择3种典型光电耦合器开展了反应堆中子辐照实验,中子注量为3×1011~5×1012cm-2时,位移效应导致电流传输比下降,饱和压降提高。发光器件相同,探测器为Si PIN光电二极管的光电耦合器比探测器为Si NPN光敏晶体管的光电耦合器的初始电流传输比要小,但其抗位移损伤能力更强。探测器均为Si NPN光敏晶体管,发光器件为异质结LED要比硅两性掺杂LED的光电耦合器的电流传输比抗位移损伤能力提高2个量级;以光敏晶体管为探测器的光电耦合器,在较大的正向电流和输出负载电阻条件下工作可提高抗辐射水平。此外,光电耦合器的位移损伤存在加电退火效应。     

Influence of electron irradiation on properties of semi-insulating GaAs detectors

The effects of electron beam irradiation on electrical and spectrometric properties of semi-insulating (SI) GaAs detectors were studied. The electric properties were monitored by reverse and forward current–voltage characteristics. In general, a breakdown voltage decrease with the dose was observed. However, some samples showed a local increase in the breakdown voltage at doses between 5 and 10?kGy. The detector spectrometric properties (the charge collection efficiency (CCE), the energy resolution and the detection efficiency) were evaluated from measured spectra of the ²⁴¹Am radionuclide gamma source before and after electron irradiation. The CCE and energy resolution showed minor changes after irradiation. The detection efficiency noticed an initial increase (up to a dose of 5?kGy) followed by a permanent decrease. At 30?kGy, the overall degradation of detector functionality was observed with all samples.     

Effect of neutron irradiation on optical spectra of α-Al2O3 and α-SiO2 single crystals

Using two crystal dielectrics (α-Al₂O₃ and α-SiO₂) as examples, the author studied the effect of large neutron-radiation doses on their optical spectra. The variation in IR spectra in the region of α-SiO₂ stretching and deformation vibrations is investigated; its relation to changes in the structure of the irradiated crystal is discussed. Institute of Nuclear Physics, Academy of Sciences of the Republic of Uzbekistan, Ulugbek Settlement, Tashkent, 702132. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 135–138, January–February, 1999.     

Synergistic effects of neutron and gamma ray irradiation of commercial CHMOS microcontroller

This paper presents the experimental results of a combined irradiation environment of neutron and gamma rays on 80C196KC20, which is a 16-bit high performance member of the MCS96 microcontroller family. The electrical and functional tests were made in three irradiation environments: neutron, gamma rays, combined irradiation of neutron and gamma rays. The experimental results show that the neutron irradiation can affect the total ionizing dose behaviour. Compared with the single radiation environment, the microcontroller exhibits considerably more severe degradation in neutron and gamma ray synergistic irradiation. This phenomenon may cause a significant hardness assurance problem.     

Analysis of the relationship between neutron dose and Cerenkov photons under neutron irradiation through Monte Carlo method

To theoretically explore the feasibility of neutron dose characterized by Cerenkov photons, the relationship between Cerenkov photons and neutron dose in a water phantom was quantified using the Monte Carlo toolkit Geant4. Results showed that the ratio of the neutron dose deposited by secondary electrons above Cerenkov threshold energy to the total neutron dose is approximately a constant for monoenergetic neutrons from 0.01 eV to 100 eV. With the initial neutron beam energy from 0.01 eV to 100 eV, the number of Cerenkov photons has a good correlation with the total neutron dose along the central axis of the water phantom. The changes of neutron energy spectrum and mechanism analysis also explored at different depths. And the ratio of total neutron dose to the intensity of Cerenkov photons is independent of neutron energy for neutrons from 0.01 eV to 100 eV. These findings indicate that Cerenkov radiation also has potential in the application of neutron dose measurement in some specific fields.     

添加Ti对Al-Bi难混溶合金组织和性能的影响

难混溶合金在凝固过程中极易发生液-液相分离,造成第二相的宏观偏析,失去了合金的应用价值.本文将第三组元Ti添加到Al-Bi难混溶合金中,研究了Ti的添加对合金的凝固组织和性能的影响,探索了原位生成的金属间化合物的存在形式,分析了第二相Bi颗粒的分布.研究结果表明,凝固过程中原位生成的长针状Al_3Ti化合物,均匀分布在Al基体中,穿插在Bi相颗粒之间,阻碍了Bi相颗粒的沉降及凝并,防止了Bi相颗粒的碰撞及长大,制备了Bi相弥散分布在Al基体中的难混溶合金;同时弥散分布在基体中的硬质相Al_3Ti还增强了基体的强度,提高了合金的硬度,使合金表现出优异的耐磨性能.     

Photoluminescence enhancement from the defects state formed by neutron/gamma mixed irradiation in an epoxy resin for LED applications

ABSTRACT

In the framework of the ICERR (International CEntres based on Research Reactors) project, the effect of neutron/gamma irradiation on material has been studied. In this work, we investigate the mixed neutron/gamma irradiation effects on the optical properties of epoxy resin polymers. Photoluminescence (PL) measurements are used in epoxy resin films irradiated in the dose range from 0 to 900?Gy. For more information about the carriers dynamics, we studied their activation energy and phononic processes through the analysis of the PL spectrum evolution as a function of temperature. Mostly, materials irradiation studies by ionizing sources show a generation of defects and subsequently lead to the damage and degradation on the different properties. In this study we have shown an advantage of neutron/gamma irradiation, it is the improvement of the luminescence properties. The 500?Gy dose has the highest quantum yield at low temperature. But the 600?Gy dose shows the highest yield at room temperature. For the 500?Gy dose, the neutron/gamma treatment mainly favored the activation of carriers from lower to higher levels. On the other side with the 600?Gy dose, there was a combination between the activation of carriers from lower to higher levels and the ionization of trapped electrons in the defects centers.     

Effect of fast neutron irradiation on magnetic properties of fullerene superconductor Rb3C60

Effects of fast neutron irradiation and post-annealing on magnetic properties of Rb₃C₆₀ were studied through the dc magnetization measurement. Rb₃C₆₀ powder samples were prepared in an evacuated quartz glass tube, and the temperature and the magnetic field dependences of dc magnetization were measured before and after irradiation and after post-annealing. The neutron fluences were 1.0, 1.8 and 3.3 × 10¹⁶ n/cm², and the post-annealing was made at a temperature of 473 K for 3 h. Magnetic hysteresis of the samples irradiated at the fluence of 1.8 and 3.3 × 10¹⁶ n/cm² disappeared, and the hysteresis curves hardly changed at the fluence of 1.0 × 10¹⁶ n/cm². As for the post-annealing effect, the hysteresis curves of the sample irradiated at the fluence of 1.8 × 10¹⁶ n/cm² were completely recovered after annealing, while those of the other samples, which had a magnetic background before irradiation, were not recovered. In this study, it was found that the loss of superconductivity in Rb₃C₆₀ powder is observed when the neutron irradiation fluence exceeds 1.0 × 10¹⁶ n/cm², and the lost superconductivity is completely recovered by the post-annealing at 473 K for 3 h.     

Effect of laser irradiation on the electrical properties of dysprosium doped LiCo-Ferrite

The effect of laser irradiation on the electrical properties of Li_0.5+z Co _z Dy _x Fe_2.5?2z?x O₄ ferrite (0.0 ≤ x ≤ 0.2, z = 0.1) has been studied in the temperature range 300 K ≤ T ≤ 750 K at frequencies of 10 kHz?5 MHz, using a LIMO-IR laser diode, at a wavelength of 808 nm. It was found that laser irradiation increases the polarization, the resistivity and the paramagnetic region. As the result of electronic rearrangement and lattice defects, small polorons and clusters were created. The doping of LiCo-Ferrite by Dy³⁺ increases both the AC and DC resistance of the investigated material. The variation of the AC and DC resistance with the Dy-content (x) obeys the following correlations R _ac/100 = 50x ²+4x+0.005 and R _dc/1000 = 31x ²+0.099x+0.09, respectively. A peculiar behaviour was obtained for the sample with Dy-content x = 0.075, as the resistance notably decreases. The applicable result is that laser irradiation increases the resistance of LiCo-ferrite by about 17% while its doping by dysprosium at x = 0.15 increases the resistance by about 23%. Its value is nearly stable for the temperature range from 340 to 480 K.     

Effect of heat treatment of the D16 alloy on its mechanical properties at low stresses

The elastic hysteresis and residual deflection of the aluminum D16 alloy samples corresponding to the model of a circular plate clamped along its perimeter have been studied at low (the beginning of the Hooke region) mechanical stresses. It has been shown that these characteristics depend substantially (change several times) on the sample state provided by different heat treatment conditions. The non-destructive method used in this work has a high accuracy and can be used to estimate the strength, yield stress, and fatigue life of metals.     

Effects of deposition parameters on the structure and mechanical properties of high-entropy alloy nitride films

High-entropy alloy (AlCrNbSiTiV)N nitride films are prepared using direct current (dc) reactive magnetron sputtering, with an equiatomic AlCrNbSiTiV alloy target. Experiments using the grey-Taguchi method are conducted to determine the effect of deposition parameters (dc power, substrate temperature, N₂/(N₂+Ar) flow rate and substrate bias) on the microstructure, mechanical and tribological properties. Orthogonal array (L₉ 3⁴), signal-to-noise ratio and analysis of variance are used to analyze the effect of the deposition parameters. The coated films are examined using scanning electron microscopy, an atomic force microscope, transmission electron microscopy (TEM), a tribometer and a nanoindenter. The TEM patterns confirm that the (AlCrNbSiTiV)N nitride films have a simple face-center-cubic structure. The experimental results show that a (AlCrNbSiTiV)N film coating significantly improves the mechanical properties. In the confirmation runs, using grey relational analysis, the improvement in friction coefficient is 32.5%, in corrosion current is 28.6%, in hardness H is 29.4%, in elastic modulus E is −18.3%, in H/E is 57.1 and in H³/E² is 225.0%. The samples with (AlCrNbSiTiV)N film coating are classified as HF1 and exhibit good adhesive strength.     

双极集成电路低剂量率辐射损伤增强效应的高温辐照加速实验

选择了四种典型双极集成电路,在两种不同剂量率下,开展了不同温度的高温辐照加速实验,测量了典型双极集成电路的辐射敏感参数在不同高温辐照下的变化规律。实验结果表明：高温辐照能够给出空间低剂量率辐射损伤增强效应的保守估计,且存在最佳辐照温度,最佳辐照温度随总剂量的增加向低温区漂移,随剂量率的增大向高温区漂移,在相同剂量率和总剂量下,输入级为NPN晶体管的双极集成电路比输入级为PNP晶体管的最佳辐照温度低。     

强激光照射对6H-SiC晶体电子特性的影响

使用基于密度泛函微扰理论的第一性原理赝势法, 模拟研究了纤锌矿6H-SiC晶体在强激光照射下电子特性的变化. 研究结果表明, 电子温度T_e在升高到3.89 eV及以上后, 6H-SiC由间接带隙的晶体变为直接带隙的晶体; 带隙值随电子温度T_e升高先是增大后又快速减小, 当电子温度T_e大于4.25 eV以后, 带隙已经消失而呈现出金属特性.