Analysis of 1 MeV electron irradiation-induced performance degradation in the germanium bottom cell of triple-junction solar cells using temperature-dependent photoluminescence measurements

Abstract

Temperature-dependent photoluminescence spectra of the germanium bottom cell of triple-junction solar cells unirradiated and irradiated with 1?MeV electrons were measured in the 10–300?K temperature range. In unirradiated germanium bottom cell, the spectra show that the PL intensity increases with temperature but slightly decreases at around 250?K because of the intrinsic defect. However, in irradiated germanium bottom cell, the spectra show that there are two negative thermal quenching processes (10–90?K and 200–270?K) and two usual thermal quenching processes (90–200?K and 270–300?K) as a result of the radiation-induced defects E_c ? 0.37?eV and E_c ? 0.12?eV.     

Feasibility of radiation sterilization and dosimetric features of ampicillin: an electron spin resonance study

In the present work, it was aimed to identify radical species produced by gamma irradiation (3–34?kGy) of solid ampicillin, to determine its spectroscopic, dosimetric, stability and kinetic behavior, and to investigate feasibility of the radiation sterilization feature of ampicillin by using electron spin resonance (ESR) spectroscopy. ESR experiments were performed at low and high temperatures (130–400?K) to examine the characteristic properties of the radical intermediates that are produced in ampicillin by gamma radiation treatment. Unirradiated ampicillin presented no ESR signal but irradiated samples exhibited ESR spectra with four resonance peaks spread over a magnetic field range of 8?mT. The spectral parameters of the central resonance line of the spectrum are g?=?2.0044 and ΔH_pp?=?0.08?mT. An exponential growth function of the applied dose was found to describe best the experimental dose–response data and it was found that ampicillin did not exhibit the feature of a good dosimetric material as its ESR intensity was relatively weak even for the samples irradiated at high level of doses. G_mean value of gamma-irradiated ampicillin was found to be 4.6?±?0.9?×?10^?9?mol/J, which is very small compared to irradiated alanine solid sample. However, the discrimination of irradiated ampicillin from unirradiated one was possible even ～3 months after storage at normal conditions. The simulation calculations indicated that gamma irradiation created two different radical species in solid ampicillin. Decay activation energy of the radical species which is mostly responsible from central intense resonance line is calculated to be 55.6?±?3.2?kJ/mol by using the signal intensity decay data derived from annealing studies. It was concluded that ampicillin could be sterilized by gamma radiation and ESR spectroscopy can be used as a potential technique to monitor its radiosterilization process.     

ESR and TL studies of irradiated Anatolian laurel leaf (Laurus nobilis L.)

Laurel leaf (Laurus nobilis L.) samples that originated from Turkey were analyzed by electron spin resonance (ESR) and thermoluminescence (TL) techniques before and after γ-irradiation. Unirradiated (control) laurel leaf samples exhibit a weak ESR singlet centered at g=2.0020. Besides this central signal were two weak satellite signals situated about 3 mT left and right to it in radiation-induced spectra. The dose–response curve of the radiation-induced ESR signal at g=2.0187 (the left satellite signal) was found to be described well by a power function. Variation of the left satellite ESR signal intensity of irradiated samples at room temperature with time in a long term showed that cellulosic free radicals responsible for the ESR spectrum of laurel leaves were not stable but detectable even after 100 days. Annealing studies at four different temperatures were used to determine the kinetic behavior and activation energy of the radiation-induced cellulosic free radicals responsible from the left satellite signal (g=2.0187) in laurel leaves. TL measurements of the polymineral dust isolated from the laurel leaf samples allowed distinguishing between irradiated and unirradiated samples.     

Phase transformation studies in unirradiated and proton beam irradiated Ni–Ti alloy between 25 and 100°C

The stress-induced phase transformation characteristics of unirradiated and proton beam irradiated NiTi alloy were investigated at different tests temperatures. The wire-shaped NiTi specimens were irradiated by 2?MeV proton beam for 30?min at room temperature to a flux of 10¹⁹ protons/m² s. Engineering stress–strain (S-S) curves of both unirradiated and irradiated specimens were obtained using a materials testing machine at 25, 50, 75 and 100°C. The results indicate a single-stage phase transformation from austenite to martensite (B2–B19′) in unirraidated specimens at all the test temperatures. In contrast, in the case of the irradiated specimens, a two-stage austenite–rhombohedral–martensite (B2–R–B19′) phase transformation is observed at 25 and 50°C. The B2–R–B19′ phase transformation, however, is found to change into B2–B19′ transformation at 75 and 100°C. The stress required to initiate the B19′ phase transformation (σ_MS) and the plateau range are found to be lower in irradiated specimens compared with those of the unirradiated specimens. The results obtained are discussed on the basis of the formation of Ni₄Ti₃ precipitates in irradiated specimens and their consequences on the phase transformations.     

Spectral,X-ray diffraction,surface morphological and thermal studies of gamma-irradiated potassium bis(oxalato)zincate(II)dihydrate

ABSTRACT

Potassium bis(oxalato)zincate(II)dihydrate was prepared and characterized. The sample was irradiated with ⁶⁰Co gamma rays up to 900?kGy. Infrared, Raman and photoluminescence spectra, X-ray diffraction pattern, surface morphology by AFM and SEM and non-isothermal decomposition of the complex were studied before and after irradiation. Spectral studies suggested significant radiation damage. X-ray diffraction studies showed reduction in unit cell volume and average crystallite size. Both unirradiated and irradiated samples of the complex belong to the hexagonal crystal system. Surface morphology of the complex changed upon irradiation. Thermal decomposition was enhanced.     

Investigation of radiosterilization feasibility of sulfamethoxazole by ESR spectroscopy

In the present study, the spectroscopic features of the radiolytic intermediates that were produced in gamma-irradiated (5, 10, 25 and 50?kGy) sulfamethoxazole (SMX) have been investigated by electron spin resonance (ESR) spectroscopy and the radiation sterilization feasibility of SMX by ionizing radiation was examined. Gamma-irradiated SMX exhibited a complex ESR spectrum consisting of 13 resonance lines where spectral parameters for the central resonance line were found to be g?=?2.0062 and ΔH_pp?=?0.6?mT. The radiation yield of SMX was calculated to be relatively low (G?=?0.1) by ESR spectroscopy and no meaningful difference was observed in the comparison of unirradiated and 50?kGy gamma irradiated SMX by the Fourier transform infrared (FT-IR) technique, confirming that SMX is a radioresistive material. Although SMX could not be accepted to be a good dosimetric material, the identification of irradiated SMX from the unirradiated sample was possible even for the low absorbed radiation doses and for a relatively long time (three months) after the irradiation process. Decay activation energy of the radical species, which is mostly responsible for the central intense resonance line, is calculated to be 45.15?kJ/mol by using the signal intensity decay data derived from annealing studies. Four radical species with different spectroscopic properties were accepted to be responsible for the ESR spectra of gamma-irradiated SMX, by simulation calculations. It is concluded that SMX and SMX-containing drugs can be sterilized by gamma radiation and ESR spectroscopy is an appropriate technique for the characterization of these induced radical intermediates during the gamma irradiation process of SMX. Toxicology tests should also be done for its safe usage.     

Composition,temperature and radiation induced changes in gamma irradiated AAAMPS copolymer

Effect of composition, temperature and radiation dose in gamma irradiated acrylamide-2-acrylamido-2-methyl propane sulphonic acid (AA) copolymer has been investigated by electron spin resonance (ESR) and fourier transform infrared (FTIR) techniques. ESR spectra of gamma irradiated AA copolymer have been recorded under different conditions. The observed ESR spectra are analysed by computer simulation techniques, to separate the constituent component spectra. Magnetic parameters employed to simulate the component spectra enabled the identification of corresponding free radicals. The AA copolymer with low acrylamide content composed of macroradicals of the type ?CH₂?CH?CH₂? and methyl radicals (CH₃) whereas the copolymer with high acryl amide content possess methyl radicals and radicals of the type ?CH₂?C(CONH₂)?CH₂?/CH₃?C?CH₃. Reasons for the variation in the formation of free radicals have been explained. The observed changes in ESR spectra of irradiated AA copolymer at higher temperatures are thought to be due to the recombination of free radicals. Formation of free radicals found to be enhanced with the increase in dose of irradiation. FTIR spectra of pure and irradiated copolymers have also confirmed the previous results.     

Effect of irradiation on ethyl 2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxylate: an ESR study

Ethyl 2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐3‐carboxylate [C₁₁H₁₅NO₂S] was synthesized by the Gewald method. Its single crystals were grown from an alcohol/ethyl acetate solution at 15 °C and characterized using IR and ¹H‐NMR. These single crystals were irradiated for 72 h at 298 K by a ⁶⁰Co gamma source with a dose speed of 0.864 kGy/h. After irradiation, electron spin resonance (ESR) measurements were carried out to study radiation‐induced radicals in the temperature range from 120 to 450 K. Additionally, for the single crystal, ESR angular dependencies were measured in the xy, xz and yz planes of the substance. This irradiated single crystal was analyzed based on the ESR spectra. Analysis of the spectra revealed that the radical was formed by a C–H bond fission at the carbon end of the substance. It was also observed that the color of the sample changed after irradiation. The hyperfine and g parameters were determined from the experimental spectra. It was inferred from these results that the hyperfine parameters and g value exhibited anisotropic behavior. The average values of these parameters were calculated as follows: g = 2.0088, A_H1=H2 = 20.70 G, A_H3=H4 = 10.80 G, A_Ha = 4.59 G, A_Hb = 3.24 G and, A_N = 6.10 G. Copyright © 2011 John Wiley & Sons, Ltd.     

Electron paramagnetic resonance,infrared, and electrical conductivity studies of γ-ray irradiated Li2SO4-K2SO4 mixed system

Abstract

Electron paramagnetic resonance spectra of 7-irradiated Li:₂SO₄-K₂SO₄ mixed system are measured at X-band and 300 K. Two types of centers, A and B, identified as LiOH⁺ ₂ and SO^? ₃ are studied. The EPR spectrum of LiOH⁺ ₂ has a well-resolved hyperfine structure. The effective g-value and the hyperfine structure constant of it are calculated. On the other hand, the SO^? ₃ center is characterized by an intense isotropic signal at a g-value ≈ 2. 0035. Mechanisms of center formation are proposed. Infrared transmittance spectra were recorded for unirradiated and γ-ray irradiated samples. A decrease in the transmittance spectra was observed after irradiation. The ionic conductivity, σ, has been measured for the Li₂SO₄-K₂SO₄ system before and after irradiation in the temperature range 30–400°C. The activation energy was found to be 1. 1 eV. A considerable decrease in the conductivity value accompanied by an increase in the activation energy was observed after γ-irradiation.     

Effect of gamma-irradiation on thermal decomposition kinetics,X-ray diffraction pattern and spectral properties of tris(1,2-diaminoethane)nickel(II)sulphate

Tris(1,2-diaminoethane)nickel(II)sulphate was prepared, and characterised by various chemical and spectral techniques. The sample was irradiated with ⁶⁰Co gamma rays for varying doses. Sulphite ion and ammonia were detected and estimated in the irradiated samples. Non-isothermal decomposition kinetics, X-ray diffraction pattern, Fourier transform infrared spectroscopy, electronic, fast atom bombardment mass spectra, and surface morphology of the complex were studied before and after irradiation. Kinetic parameters were evaluated by integral, differential, and approximation methods. Irradiation enhanced thermal decomposition, lowering thermal and kinetic parameters. The mechanism of decomposition is controlled by R₃ function. From X-ray diffraction studies, change in lattice parameters and subsequent changes in unit cell volume and average crystallite size were observed. Both unirradiated and irradiated samples of the complex belong to trigonal crystal system. Decrease in the intensity of the peaks was observed in the infrared spectra of irradiated samples. Electronic spectral studies revealed that the M–L interaction is unaffected by irradiation. Mass spectral studies showed that the fragmentation patterns of the unirradiated and irradiated samples are similar. The additional fragment with m/z 256 found in the irradiated sample is attributed to S₈⁺. Surface morphology of the complex changed upon irradiation.     

Electron Spin Resonance of Free Radicals Produced by Ultraviolet Photolysis in Some Vegetables and Their Juices

Abstract

Paramagnetic species produced by ultraviolet photolysis in various vegetables of domestic origin have been investigated by electron spin resonance technique. The ESR spectra of the small cut pieces of the vegetable fleshes and their frozen juices have been investigated before and under UV photolysis. The samples of potato and carrod exhibit too complex ESR spectra, but parsley, dill, white radish and green pepper do not exhibit any ESR signal before UV photolysis at 113 K. However both the small cut pieces of fleshes of potato, carrot, parsley, dill, white radish and green pepper and their juices exhibit ESR spectra during UV photolysis that we attributed to the H?O and CO^? ₂ radicals. The ESR parameters of these radicals have been obtained and the origins of these radicals have been shown to be the glucose molecules in the carbohydrate chains of these substances.     

Positron annihilation spectroscopy and specific heat study of Neon ion irradiated MgB2

Specific heat studies under magnetic field and positron annihilation spectroscopy were carried out on 160 MeV Ne ion irradiated polycrystalline MgB₂ samples. There is an unusual decrease in positron lifetime in the irradiated sample which may be due to neon ion implantation. This was also indicated by change in cell volume. Coincidence Doppler Broadening Spectra of Mg, B, irradiated and unirradiated MgB₂ show that positrons primarily annihilate in boron sublattice in the unirradiated sample whereas there is some similarity of the spectrum of the irradiated sample with that of Mg. There is Mg deficiency in the unirradiated sample whereas predominantly boron vacancies exist in Ne ion irradiated MgB₂ sample. Specific heat measurements show that there is a small increase in electronic part of the specific heat and electron-phonon coupling constant.     

Neutron diffraction study of anisotropy of crystal lattice compression in irradiated of fast neutron high-T c superconductors YBa2Cu3O6·95 and La1·83Sr0·17CuO4 under pressure

Abstract

The structural changes in the high temperature superconductors (HTSC) samples of the compounds YBa₂Cu₃O_6·95 and La_1·83Sr_0·17CuO₄ under pressure being unirradiated and irradiated by fast neutrons have been studied by the neutron diffraction method. The different anisotropy of crystal lattice compression was found for these compounds in the initial and irradiated states.     

Effect of laser irradiation on the structure and valence states of copper in Cu-phosphate glass by XPS studies

The effect of laser irradiation using three different wavelengths (IR, visible and UV) generated from Nd:YAG laser on the local glass structure as well as on the valence state of the copper ions in copper phosphate glass containing CuO with the nominal composition 0.30(CuO)-(0.70)(P₂O₅), has been investigated by X-ray photoelectron spectroscopy (XPS). The presence of asymmetry and satellite peaks in the Cu 2p spectrum for the unirradiated sample is an indication of the presence of two different valence states, Cu²⁺ and Cu⁺. Hence, the Cu 2p_3/2 spectrum was fitted to two Gaussian-Lorentzian peaks and the corresponding ratio, Cu²⁺/Cu_total, determined from these relative areas clearly shows that copper ions exist predominately (>86%) in the Cu²⁺ state for the unirradiated glass sample under investigation. For the irradiated samples the symmetry and the absence of satellite peaks in the Cu 2p spectra indicate the existence of the copper ions mostly in Cu⁺ state. The O 1s spectra show slight asymmetry for the irradiated as well as unirradiated glass samples which result from two contributions, one from the presence of oxygen atoms in the P-O-P environment (bridging oxygen BO) and the other from oxygen in an P-O-Cu and PO environment (non-bridging oxygen NBO). The ratio of NBO to total oxygen was found to increase with laser power.     

Investigation of gamma radiation induced changes in local structure of borosilicate glass by TDPAC and EXAFS

Gamma radiation induced changes in local structure around the probe atom (Hafnium) were investigated in sodium barium borosilicate (NBS) glass, used for immobilization of high level liquid waste generated from the reprocessing plant at Trombay, Mumbai. The (NBS) glass was doped with ¹⁸¹Hf as a probe for time differential perturbed angular correlation (TDPAC) spectroscopy studies, while for studies using extended X-ray absorption fine structure (EXAFS) spectroscopy, the same was doped with 0.5 and 2 % (mole %) hafnium oxide. The irradiated as well as un-irradiated glass samples were studied by TDPAC and EXAFS techniques to obtain information about the changes (if any) around the probe atom due to gamma irradiation. TDPAC spectra of unirradiated and irradiated glasses were similar and reminescent of amorphous materials, indicating negligible effect of gamma radiation on the microstructure around Hafnium probe atom, though the quaqdrupole interaction frequency (ω _Q) and asymmetry parameter (η) did show a marginal decrease in the irradiated glass compared to that in the unirradiated glass. EXAFS measurements showed a slight decrease in the Hf-O bond distance upon gamma irradiation of Hf doped NBS glass indicating densification of the glass matrix, while the cordination number around hafnium remains unchanged.     

ESR of gamma irradiated single crystals of cholesteryl acetate and cholesteryl chloroformate

Cholesteryl acetate and cholesteryl chloroformate compounds have been irradiated with ⁶⁰Co-γ rays at room temperatures. The irradiated samples have been examined for paramagnetic resonance, and the observed spectra in several cases have been identified with specific radicals. The results in each case have been considered in relation to the present knowledge of the radiation chemistry of the compound. The single crystals have been investigated between 120 and 300?K. The spectra are found to be temperature independent and radiation damage centers are attributed to ?HCH₂ radical for cholesteryl acetate and ?H₃ and ?HCH₂ CH₂ CH₂ radicals for cholesteryl chloroformate.     

Effect of proton irradiation on the physical properties of PC/PBT blends

Samples from polycarbonate/poly (butylene terephthalate) (PC/PBT) blends film have been irradiated using different fluences (1?×?10¹⁵– 5?×?10¹⁷ H⁺/cm²) of 1?MeV protons at the University of Surrey Ion Beam Center, UK. The structural modi?cations in the proton irradiated samples have been studied as a function of fluence using different characterization techniques such as X-ray diffraction and UV spectroscopy. The results indicate that the proton irradiation reduces the optical energy gap that could be attributed to the increase in structural disorder of the irradiated samples due to crosslinking. Furthermore, the color intensity ΔE, which is the color difference between the non-irradiated sample and those irradiated with different proton fluences, increased with increasing the proton fluence up to 5?×?10¹⁷ H^+/cm², convoyed by an increase in the red and yellow color components. In addition, the resultant effect of proton irradiation on the thermal properties of the PC/PBT samples has been investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). It is found that the PC/PBT decomposes in one weight loss stage. Also, the variation of transition temperatures with proton fluence has been determined using DSC. The PC/PBT thermograms were characterized by the appearance of two endothermic peaks due to the glass transition and melting temperatures. The melting temperature of the polymer, T_m, was investigated to probe the crystalline domains of the polymer, since the proton irradiation destroys the crystalline structure so reducing the melting temperature.     

Antiferromagnetic resonance and high magnetic field properties of NaNiO2

Magnetisation measurements up to 23 T and submillimeter wave ESR in the frequency region 48-380 GHz have been performed on NaNiO₂ powders at low temperature. Also typical spectra above the Néel temperature are shown. At 4 K the magnetisation shows a spin-flop transition at 1.8 T and saturation at 10 T. /Ni confirms the low spin state of the Ni³⁺ ions. The susceptibility exhibits a maximum at K with and K. NaNiO₂ is an A-type antiferromagnet: we derive K and K for the interactions between Ni ions within and between adjacent layers, respectively. The AFMR spectra yield an energy gap of 52.5 GHz, in agreement with the spin-flop value derived from the magnetisation. The anisotropy of the g factor observed at 100 K with can be attributed to the Jahn-Teller effect for Ni³⁺ ions in the low spin state, which stabilises the occupation. We finally comment on the isomorphic controversial Li_1-xNi_1+xO₂ compound. Received 9 March 2000 and Received in final form 13 July 2000.     

Mechanical response of proton beam irradiated nitinol

The present investigation deals with the study of mechanical behavior of proton beam irradiated nitinol at room temperature. The specimens in austenitic phase were irradiated over periods of 15, 30, 45 and 60 min at room temperature using 2 MeV proton beam obtained from Pelletron accelerator. The stress-strain curves of both unirradiated and irradiated specimens were obtained using a universal testing machine at room temperature. The results of the experiment show that an intermediate rhombohedral (R) phase has been introduced between austenite and martensite phase, which resulted in the suppression of direct transformation from austenite to martensite (A-M). Stresses required to start R-phase (σ_RS) and martensitic phase (σ_MS) were observed to decrease with increase in exposure time. The hardness tests of samples before and after irradiation were also carried out using Vickers hardness tester. The comparison reveals that the hardness is higher in irradiated specimens than that of the unirradiated one. The increase in hardness is quite sharp in specimens irradiated for 15 min, which then increases linearly as the exposure time is increased up to 60 min. The generation of R-phase, variations in the transformation stresses σ_RS and σ_MS and increase in hardness of irradiated nitinol may be attributed to lattice disorder and associated changes in crystal structure induced by proton beam irradiation.     

ESR of Yb3+ ions in a single crystal of the fluctuating-valence compound YbB12

The temperature and angular dependences of electron spin resonance (ESR) spectra of Yb³⁺ ions in a single crystal of fluctuating-valence compound YbB₁₂ were studied. The existence of Yb?Yb ion pairs was observed in a cubic-symmetry crystal. The ions forming the pairs are coupled by the isotropic exchange but interact also with the other pairs by the dipole and exchange coupling. The occurrence of a slight anisotropy in a cubic semiconductor may be the result of a spontaneous break of symmetry specific for the ground state of the Kondo dielectric. A strong temperature dependence of the amplitude of the ESR signals is found at 1.6–4.2 K and interpreted as a result of the capture of electrons by Yb³⁺ ions from electron traps with a binding energy of 18 K. ESR spectra of Yb³⁺ single ions in the Γ₆ state were observed also. The decrease of temperature from 4.2 to 1.6 K indicates a tendency to the ferromagnetic ordering of Yb?Yb pairs.