Shiyu He

RADIATION EFFECTS OF PROTONS AND ELECTRONS ON BACKFIELD SILICON SOLAR CELLS

Radiation effects of protons and electrons on the backfield silicon solar cells were investigated. The samples without cover glass were irradiated by the protons and electrons with 30-180 keV and a given flux of 1.2 × 10 12 cm −2 · s −1 for various fluences at 77 K. Experimental results show that the short circuit current decreases gradually with increasing the proton fluence, while the open circuit voltage degrades severely under lower fluences. No obvious changes appear in the electric properties before and after the irradiation by electrons, and there exists a recovery effect in the in situ measurement for the irradiated samples. The effect of the combined radiation of protons and electrons does not show simple additivity. The damage extent of proton radiation is larger than that of combined radiation under lower electron fluences, while the combined radiation results in more severe damage under higher fluences. The DLTS analysis verified that the primary defects induced by protons were the H1 or (V+B) type at the energy level of +0.45 eV, which would result in formation of a resistance layer in the base region and degradation of the backfield Si solar cells.

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.

Degradation of Teflon Film Under Radiation of Protons and Electrons

Aluminized Teflon® film (fluorinated ethylene propylene) is commonly used on exterior spacecraft surfaces for thermal control. Synergistic effects of proton and electron radiation on the Teflon film 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 of kiloelectron volts. The results showed that an absorption band from the near-ultraviolet to the visual region was formed under either proton or electron radiation. But there was no additive effect on reflective property of aluminized Teflon under synergistic radiation of protons and electrons. The effect of simultaneous radiation of protons and electrons was lower than the additive effect of these two charged particles. Under the equal fluence of radiation, the total changes in spectral reflectance were independent from the radiation sequence of protons and electrons. The structural defects induced by protons and electrons were somewhat different. The electrons preferred to activate large molecules and bombard fluorine atoms out of the main chains, forming various free radicals and carbon atoms. Under the radiation of protons, the implantation of protons played an important role in the formation of functional groups. The relation between optical properties and microdefects is discussed.

EFFECT OF VUV RADIATION ON PROPERTIES AND CHEMICAL STRUCTURE OF POLYETHYLENE TEREPHTHALATE FILM

The effect of VUV radiation on polyethylene terephthalate (PET) film was investigated. A gas-jet type of VUV source with the wavelengths of 5-200 nm was used. The experimental results show that under the VUV irradiation, both the tensile fracture strength and elongation decrease slightly. The spectral absorbance of the PET film increases noticeably with increasing VUV dose. The absorption band mainly forms in the near-ultraviolet region. The XPS, FTIR, and ESR analyses indicate that in the skin layer of PET film irradiated with VUV, the C-O bonds could be broken and decarbonylation occurs, leading to the formation of free radicals of benzene rings as well as a trend of carbonification. The scission of the macromolecule chains, the increase in radical concentration, and the carbonification would cause the degradation in optical properties for the PET film under VUV exposure.

Changes in properties and structure of polyethylene terephthalate film under vacuum ultraviolet

The effect of vacuum ultraviolet (VUV) radiation on polyethylene terephthalate (PET) film was investigated on a gas-jet VUV source with a wavelength of 5‐200 nm. The experimental results show that under VUV irradiation both tensile fracture strength and elongation decrease slightly. The spectral absorbance of the PET film increases noticeably with increasing dose. An absorption band mainly forms in the ultraviolet-to-visible region. X-ray photoelectron spectroscopy, Fourier transform infrared, and electron spin resonance analyses indicate that in the skin layer of PET film under VUV radiation, the C‐O bonds are broken and decarbonylation occurs, leading to the formation of free radicals as well as a trend to carbonification. The scission of the macromolecule chains, the increase in radical concentration, and the carbonification are considered to be major contributors to the change of optical properties for PET film under VUV exposure.

Kinetics of Radiation Damage of Quartz Glass by Low-Energy Protons

In a ground-based simulation of the space environment of high vacuum, heat sink, and low-energy protons (140 keV), the change in optical transmittance of JGS3 optical quartz glass was studied, and a kinetic model for the evolution of color centers in the process of radiation damage was explored. Experimental results show that radiation damage effects obviously occur in the surface layer of quartz glass under high-flux and low-energy proton radiation. The optical density change increases rapidly and then a saturation trend appears with increasing absorption dose. Based on experimental results, a kinetic model for the evolution of color centers in quartz glass irradiated with protons is proposed, and the change in optical density is given. The fitted curve is similar to experimental ones. It is believed that the proposed kinetic model can be used in the quantitative description of the change in optical properties of quartz glass increasing absorption dose under low-energy proton radiation.

DAMAGE KINETICS OF QUARTZ GLASS BY PROTON RADIATION

The change in optical transmittance of JGS3 optical quartz glass was studied using ground simulation for the space environment conditions of high vacuum, heat sink, and 140 keV low energy protons and the kinetic model for the evolution of color centers in the process of radiation damage was explored. The experimental results show that radiation damage occurs in the surface layer of quartz glass under large flux and low-energy proton radiation. The optical den- sity change increases rapidly and then a saturation trend appears with increasing absorption dose. A kinetic model for the evolution of color centers in quartz glass irradiated with protons is proposed based on experimental data, from which the change in optical density can be given. The model fitted curve is similar to ex- perimental ones. It is believed that the proposed kinetic model can be used in the quantitative description for the change in optical property of quartz glass with increasing absorption dose under proton radiation with low energy.