Hongbin Geng

Combined Radiation Effects of Protons and Electrons on NPN Transistors

This paper examines individual radiation effects caused by 110 keV electrons, 70 keV protons and 170 keV protons, and combined radiation effects induced by 110 keV electrons together with 70 keV protons and 110 keV electrons with 170 keV protons on the forward current gain of bipolar junction transistors (3DG112D, NPN). Key parameters were measured in-situ and the change in current gain of the NPN transistors is obtained at a fixed collector current. Experimental results show that the current gain degradation of the NPN transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 keV electrons, while the displacement damage is mainly induced by 170 keV protons in this study. Under the combined exposure of 170 keV protons and 110 keV electrons, the current gain degradation lies between those given by the individual irradiations. The current gain degradation is mainly caused by the 170 keV protons, and the 110 keV electrons mitigate the degradation to some extent. In the case of combined irradiation of 110 keV electrons and 70 keV protons, no synergistic effect occurs, the current gain degradation is basically controlled by the 110 keV electrons.

Simultaneous and Sequential Radiation Effects on NPN Transistors Induced by Protons and Electrons

This paper examines individual radiation effects caused by 110 keV electrons and 170 keV protons, and combined radiation effects induced by 110 keV electrons together with 170 keV protons on the forward current gain of NPN bipolar junction transistors (3DG130, 3DG112). Key parameters were measured in-situ and the change in current gain of the NPN bipolar junction transistors is obtained at a fixed voltage of base-emitter junction (VBE) during simultaneous and sequential exposures. Experimental results show that the current gain degradation of the NPN bipolar junction transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 keV electrons, while the displacement damage is mainly induced by 170 keV protons in this investigation. Based on the simultaneous and sequential exposure results, the ionization damage caused by 110 keV electrons can give an enhancing effect to displacement damage induced by 170 keV protons for NPN bipolar junction transistors.

Synergistic Radiation Effects on PNP Transistors Caused by Protons and Electrons

This paper examines individual radiation effects caused by 110 KeV electrons, 70 KeV electrons and 170 KeV protons, and combined radiation effects induced by 110 KeV electrons together with 170 KeV protons and 70 KeV electrons with 170 KeV protons on the forward current gain of bipolar junction transistors (3CG130, PNP). The combined radiation effects include simultaneous and sequential radiation effects. Key parameters were measured in-situ and the change in current gain of the PNP transistors is obtained at a fixed voltage of emitter-base junction . Experimental results show that the current gain degradation of the PNP transistors is sensitive to both of ionization and displacement damage. The ionization damage is primarily caused by 110 KeV and 70 KeV electrons, while the displacement damage is mainly induced by 170 KeV protons in this investigation. Based on the simultaneous and sequential exposure results, the ionization damage caused by 110 KeV and 70 KeV electrons could give annealing-like and enhancing effects to displacement damage induced by 170 KeV protons for PNP BJTs.

Radiation effects on optical and structural properties of GG17 Glasses induced by 170 keV electrons and protons

The effects of 170 keV electron and proton irradiation are investigated on the optical property and the structure of GG17-type borosilicate glasses for the purpose of assessing the suitability of this material for the rubidium lamp envelope, based on GEANT4 simulating calculation, using electron paramagnetic resonance and Fourier transform infrared spectra and optical-transmittance measurements. The Micro-mechanisms on damage of GG17 Glasses are clarified for electron and proton, respectively. For the electron with the energy of 170 keV, defect creation is due to ionization energy losses and the center is mainly boron oxygen hole center (BOHC) formed by one hole trapped on a bridge oxygen structure with [BO4]−. As a result the number of BOHCs grows as the electron fluence increases. However, for the proton with the energy of 170 keV, the creation of structural defects dominates by means of debonding as a result of an atom having been kicked off the structural chain (displacement effect). This leads to the...

Study on Damage Effects of Methyl Silicone Rubber Induced by Proton Radiation

The damage behaviors of methyl silicone rubber induced by radiation of protons with 150-keV energy were studied. The surface morphology, tensile strength, Shaw hardness, cross-linking density, and glass temperature were evaluated. Positron annihilation lifetime spectroscopy and infrared attenuated total reflection analysis were carried out to reveal the damage mechanism of the rubber. The results show that the tensile strength, Shaw hardness, cross-linking density, and glass temperature of the silicone rubber increase and then decrease with increasing radiation fluence. Analysis indicated that all of the annihilation span τ 3 and the intensity I 3 of the longest lifetime positrons spouses, as well as the free volume V f , decreased with increasing radiation fluence, under lower radiation fluences, and then increased slowly after the fluence 10 1 5 cm - 2 . The proton radiation would mainly induce cross-linking reactions in the silicon rubber when the fluence is lower, whereas degradation becomes dominant as the fluence increases.

Changes in Microstructure and Tensile Properties of Hot Rolled 1420 Al-Li Alloy Subjected to Thermocycling

The thermal cycling tests, which simulate the cyclic temperature events in space, between 77 and 393K with a period of 480s by a constraint thermal cycling apparatus were performed to hot rolled 1420 Al-Li alloy. The tensile properties before and after thermal cycling were evaluated. The microstructure of the alloy was studied by means of TEM. Experimental results show that the strength and ductility of the alloy decrease obviously after 1000 or 3000 thermal cycles. Thermal stress induces changes in microstructure are characterized by emitting dislocations from boundaries to matrix, forming dislocation pile-ups against grain boundaries and an increase of dislocation density. The accumulation of changes in microstructure may lead to stress concentration at grain boundaries, and result in an obvious degradation in tensile properties.

Effects of Space Environment Factors on Optical Materials for Space Application

The effects of proton and electron radiations as well as thermal cycling on properties of optical materials for space application were studied using a complex simulator for space environment. The energy of protons and electrons ranged from 60 to 180 keV that is within the energy range of the Earth radiation belt. The temperature interval of thermal cycling, Δ, was kept between 80 and 400K. The obtained results showed that if the reflectors were not grounded directly, charging-and-discharging could cause severe damage of the reflector surface. Bulging or exfoliating of the surface films would be more severe due to synergistic effect of proton radiation and thermal cycling on the reflectors. For JGS3 quartz glass, the proton and electron radiations result mainly in the ultraviolet absorption at 210–240 nm, while an absorption in visible range also occurs in the case of high radiation fluence.

A Study of Methylsilicone Rubber Damage Behavior Induced by Proton Irradiation

In this paper, the damage behavior of methylsilicone rubber induced by irradiation of protons with 150keV energy was studied. The surface morphologies, tensile strength, Shaw hardness, cross-linking density and glass temperature were examined. Positron annihilation lifetime spectrum analysis (PALS) was performed to reveal the damage mechanisms of the rubber. The results showed that the tensile strength and Shaw hardness of the rubber increased firstly and then decreased with increasing the irradiation fluence. The PALS characteristics τ3 and I3, as well as the free volume Vf, decreased with increasing the irradiation fluence up to 1015cm−2, and then increased slowly. It was noticed that the proton irradiation caused a decrease in the free volume of the methyl silicone rubber when the fluence was less than 1015 cm−2, while the free volume increased at the fluence greater than 1015cm−2. The results on cross-linking density indicated that the cross-linking induced by proton irradiation was dominant under smaller proton fluencies, increasing the tensile strength and Shaw hardness of the rubber, while the degradation of the rubber dominated under greater fluencies, leading to decreasing the tensile strength and Shaw hardness.

A Study of Synergistic Radiation Effects of Protons and Electrons on Teflon FEP/Al Degradation

Aluminized Teflon FEP film (fluorinated ethylene-propylene) is commonly used on exterior spacecraft surfaces for thermal control. Synergistic effects of proton and electron radiations on aluminized Teflon FEP degradation were investigated in terms of ground-based simulation testing. The energy of protons and electrons was chosen in the range of a few tens keV. The results showed that both the radiations of protons and electrons led to forming an absorption band in the near ultraviolet to visual regions, and the electrons also resulted in a decrease of spectral reflectance with fluence in the near-infrared range. The effect of synergistic radiation of protons and electrons did not show additivity on the reflective property of aluminized Teflon FEP film. The effect of simultaneous radiation of protons and electrons was lower, while the additive radiation effect given by the two types of charged particles higher. Under a given fluence of radiation, the overall changes in spectral reflectance were independent from the radiation sequence of protons and electrons. The changes in spectral reflectance with radiation fluence and the XPS spectrum for the simultaneous radiation were similar to those for the sequential electron to proton radiation.

Numerical Simulation of Thermal Stress Induced by Thermocycling in Hot Rolled 1420 Al-Li Alloy

A model of grains under plane stress state has been established. According to the grains model, thermal stress induced by thermal cycling (77K–393K) in the alloy is numerically simulated by finite element method. The numerical analysis results show that the difference in coefficient of thermal expansion and elastic modulus for grains along different crystal directions can produce alternate thermal misfit stresses and strains near boundaries due to thermal cycling. At the temperatures of the upper and lower limit (393K and 77K), thermal stress nearby grain boundary reaches maxima.