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.     

Lithium fluoride colour centres-based imaging detectors for proton beam characterization at high doses

Proton beams of 7 MeV energy, produced by a linear accelerator, were used to irradiate LiF crystals and thin films thermally evaporated on glass substrates in the dose range from 10³ to 4 × 10⁶ Gy, inducing the formation of stable photoluminescent colour centres (mainly F₂ and F₃⁺), emitting in the visible spectral range. Using a conventional fluorescence microscope, the transversal proton beam intensity was mapped by acquiring the photoluminescence image of the irradiated spots. Image analysis allowed measuring the integrated photoluminescence intensity as a function of the irradiation dose: a linear optical response was obtained up to different maximum dose values, after which a quenching was observed, depending on the nature of the samples (crystals or films). The colour centres formation was investigated by optical absorption spectroscopy at room temperature and the Principal Component Analysis was applied to the absorption spectra of irradiated LiF crystals. In samples irradiated at highest doses, it allowed clearly identifying the formation of more complex aggregate defects, which appears strictly related to the observed photoluminescence quenching effect.     

Effect of swift heavy ion irradiation on thermal,optical and structural properties of poly vinylidene chloride

Poly vinylidene chloride (PVDC) irradiated with lithium (50 MeV), carbon (85 MeV), nickel (120 MeV) and silver ions (120 MeV) having fluence range of 1 × 10¹¹ ions/cm² to 3 × 10¹² ions/cm² have been studied using different techniques i.e. XRD (X-ray diffraction), FTIR (Fourier transform infrared), UV–Visible and TGA (thermo-gravimetric analysis). In XRD analysis, the intensity of diffraction peaks of PVDC irradiated with lithium ions was enhanced at lower fluence as compared to pristine. The shift in optical absorption edge in irradiated PVDC was correlated with the decrease in optical band gap energy. The distinguishable characteristic peaks were observed due to UV–Vis analysis, in lithium irradiated samples of PVDC at higher fluences. The % age decrease in optical band gap energy for the respective ions were 30.9%, 34.16%, 81.1%, 87.02% respectively. Formation of double carbon bonds and breaking of C–O and C–Cl bonds with the release of Cl in irradiated PVDC was observed in FTIR spectra. In Thermogravimetric analysis (TGA), the % age weight loss observed for irradiated samples with increase in ion fluence was lesser than the % age weight loss observed in pristine sample.     

Yield curves for photo-proton emission from carbon and beryllium

The yields of photo-protons at laboratory angles of 40° and 70° from carbon irradiated with bremsstrahlung of end-point energies between 125 and 1000 MeV are given. From these data and a more limited set for beryllium, the shapes of the cross-sections for photo-proton emission by monochromatic photons are deduced. From a separate series of measurements on carbon at 70° lab with bremsstrahlung of end-point energies 380 and 420 MeV, the energy spectrum of photo-protons emitted by photons of energies 400±20 MeV has been derived.     

Effect of plasma scale length on multi-MeV proton production by intense laser pulses

The influence of the plasma density scale length on the production of MeV protons from thin foil targets irradiated at I lambda(2) = 5 x 10(19) W cm(-2) has been studied. With an unperturbed foil, protons with energy >20 MeV were formed in an exponential energy spectrum with a temperature of 2.5+/-0.3 MeV. When a plasma with a scale length of 100 microm was preformed on the back of the foil, the maximum proton energy was reduced to <5 MeV and the beam was essentially destroyed. The experimental results are consistent with an electrostatic accelerating mechanism that requires an ultrashort scale length at the back of the target.     

Investigations on the optical, thermal and surface modifications of electron irradiated l-threonine single crystals

l-Threonine single crystals have been irradiated by 6 MeV electrons. Irradiated crystals at various electron fluences were subjected to various techniques such as UV–vis–NIR, atomic force microscopy (AFM) and thermomechanical analyses. Thermal strength of the irradiated crystals has also been studied through differential scanning calorimetry (DSC) measurements. The results have been discussed in detail.     

Electron irradiation damage in silicon containing carbon and diffused 18O

Silicon crystals have been diffused with ¹⁸O, irradiated with 2 MeV electrons at room temperature and then annealed up to 400°C. Infrared absorption measurements of the localized vibrational modes of various defects have been made at each stage.     

Structural phase diagram for ZnS nanocrystalline thin films under swift heavy ion irradiation

The synthesis of nanocrystalline ZnS thin films by pulsed laser deposition and their modification by swift heavy ions are presented. The irradiations with 150 MeV Ni ions at fluences of 1×10¹¹, 1×10¹² and 1×10¹³ ions/cm² have been used for these studies. Irradiation results in structural phase transformation and bandgap modification of these films are investigated by using X-ray diffraction and UV-visible absorption measurements, respectively. Since stoichiometry changes induced by irradiation can contribute to the modification of these properties, elastic recoil detection analysis has been performed on pristine and 150 MeV Ni ions irradiated ZnS thin films using a 120 MeV Ag ion beam. The stoichiometry of the films has been found to be similar for pristine and ion irradiated samples. A structural phase diagram based on thermal and pressure spikes has been constructed to explain the structural phase transformation.     

Enhancement of proton acceleration by hot-electron recirculation in thin foils irradiated by ultraintense laser pulses

MeV-proton production from solid targets irradiated by 100-fs laser pulses at intensities above 1x10(20) W cm(-2) has been studied as a function of initial target thickness. For foils 100 microm thick the proton beam was characterized by an energy spectrum of temperature 1.4 MeV with a cutoff at 6.5 MeV. When the target thickness was reduced to 3 microm the temperature was 3.2+/-0.3 MeV with a cutoff at 24 MeV. These observations are consistent with modeling showing an enhanced density of MeV electrons at the rear surface for the thinnest targets, which predicts an increased acceleration and higher proton energies.     

Spectroscopic studies of copper and carbon ion irradiated polypropylene

The samples of polypropylene (PP) have been irradiated with 120 MeV ⁶⁴Cu⁹⁺ and 70 MeV ¹²C⁵⁺ ion beams, with the fluence ranging from 1 × 10¹³ to 1 × 10¹¹ ions/-cm⁻². UV-VIS and FTIR techniques have been used to study the chemical and optical properties of these irradiated polymers. UV spectra revealed that the optical-gap energy decreases by 54 % with copper ion irradiation at the fluence of 1 × 10¹³ ions/cm², whereas at the same fluence, carbon beam decreases the optical-gap energy by 20%. FTIR analysis of ion irradiated samples revealed the presence of -OH, C = O and C = C bonds. Alkyne formation has been observed only in the case of copper ion irradiation.      

双束质子辐照砷化镓光电导探测器的I-V特性

 对用能量为7.5MeV和20MeV,注量为10¹¹～10¹³cm^-2的质子辐照后的砷化镓材料制作的光电导探测器的光电流和暗电流进行了测试，并由此推得电导率的变化。结果表明，经过能量为7.5MeV的质子改性后的砷化镓探测器相对于未改性的附加光电导率Δσ减少，而且随着辐照注量的增加而越小，而对于先用能量为20MeV质子辐照后再用能量为7.5MeV的质子辐照的砷化镓材料制作的探测器，其附加光电导率Δσ的减少则更为明显。对上述现象进行了分析，并根据其相应关系预测了该种探测器的响应时间、灵敏度、拖尾现象及受X射线激发的输出脉冲的后延的变化情况。     

Recombination of close frenkel defects in gold

The occurrence of close-vacancy-interstitial-pairs in electron-irradiated gold and the annealing temperature of this type of defect have been investigated by means of “sub-threshold” irradiations. Different samples have been irradiated with 3 MeV electrons at five different temperatures between 7.5°K and 36°K. These samples containing Frenkel defects have then been irradiated at 12°K with 1.2 MeV electrons. This energy is less than the threshold for defect production. During the sub-threshold irradiation, defect annihilation rates have been measured which depend strongly on the temperature at which the defects had been produced. For 7.5°K and 12°K they are of the same order of magnitude as were found in Al, Cu, Pt, and Ta, and were ascribed to recombination of closevacancy-interstitial-pairs. For defects produced at 22°K the annihilation rate is smaller by one order of magnitude and even smaller for defects produced at still higher temperatures. It is concluded from this that close-pairs become thermally unstable in gold between 12 and 22°K.     

Mössbauer study of amorphous alloys irradiated with energetic heavy ions

The Mössbauer spectroscopy was applied to study radiation damage in metal-metalloid amorphous alloys irradiated with⁴⁰Ar/E=225 MeV/ or¹³²Xe/E=120 MeV/ ions at room temperature. The observed dose dependent changes in the intensity of the Mössbauer lines and of the hyperfine field distributions can be associated with structural changes in short-range order of the irradiated amorphous alloys.     

Mössbauer study of ferromagnetic metallic glasses irradiated by swift heavy ions at temperatures 100 and 300 K

The effect of swift heavy ion irradiation on ferromagnetic metallic glasses Fe₄₀Ni₃₈Mo₄B₁₈ and Fe₇₈Si₉B₁₃ has been studied. The ion beams used are 100 MeV ¹²⁷I and 180 MeV ¹⁹⁷Au. The specimens were irradiated at fluences ranging from 3 × 10¹² to 1.5 × 10¹⁴ ions/cm². The irradiations have been carried out at temperatures 100 and 300 K. The magnetic moments are sensitive towards the irradiation conditions such as irradiation temperature and stopping power of incident ion beam. The irradiation-induced effects have been monitored, by using Mössbauer spectroscopy. The modifications in magnetic anisotropy and hyperfine magnetic field distributions, as an effect of different irradiation temperature as well as different stopping power have been discussed. After irradiation, all the samples remain amorphous and magnetic anisotropy considerably changes from its original in-plane direction. The results show enhancement in magnetic anisotropy in the specimen irradiated at 100 K, as compared to that of irradiated at 300 K. It is expected that at low temperature, the stresses produced in the material would remain un-annealed, compared to the samples irradiated at room temperature and therefore, the modification in magnetic anisotropy would be enhanced. A distribution of hyperfine magnetic field, of the samples irradiated at low temperature, show a small but distinct peak at ～?11 Tesla, indicating Fe-B pairing.     

Permeability of oxygen through polycarbonate in water

The permeability of oxygen in water through polycarbonate is observed for thin Makrofol KG and Polyethylenterephthalat (PETP) foils of different thicknesses.

For each thickness the oxygen permeability through the polymer foils has been measured for unirradiated and with a high fluence irradiated foils. It was found that the permeability of oxygen through irradiated Makrofol KG foils is up to a factor of two higher than unirradiated foils.

The foils were irradiated with ⁷⁹Au ions at the energy of 11.65 MeV/u at GSI Darmstadt, Germany.     

Optical behaviour of swift heavy ions irradiated poly(vinyl alcohol) films

Polyvinyl alcohol films were irradiated to 90 MeV O ⁶⁺ and 150 MeV Si ¹⁴⁺ ions at fluence ranging from 10¹⁰ to 10¹² ions/cm². The observed changes in optical energy gap of this polymer have been investigated and results are tried to be explained in terms of energy transferred by the incident ions. It has been noticed that the value of optical energy gap decreases with increasing energy loss during the ion–polymer interaction process.     

Optical and Structural Modifications in Heavy Ion Irradiated Polystyrene

Samples of polystyrene (PS) have been irradiated with ⁶⁴Cu (50 and 120 MeV) and ¹²C (70 MeV) ion beams (fluence=10¹¹ to 10¹³ ions cm^?2) in order to study the induced modifications using UV‐VIS and FTIR spectroscopy. UV spectra of irradiated samples reveal that the optical band gap decreases from 4.36 to 1.46 eV in PS. The decrease in optical band gap is more pronounced with the Cu‐ion beam due to high electronic energy loss as compared to the C ion beam. The effect of low energy (50 MeV) Cu ions on the optical properties of PS is larger than that due to high energy (120 MeV) Cu ions. The correlation between the optical band gap and the number of six member carbon rings inside the largest carbon clusters embedded in the network of polystyrene is discussed. FTIR spectra reveal the formation of hydroxyl, alkene, and alkyne groups in the Cu‐ion irradiated PS. Changes in the intensity of the absorption bands on irradiation with C‐ion relative to pristine samples have also been observed and are discussed.     

快重离子辐照效应的穆斯堡尔谱学研究

概述了利用穆斯堡尔效应开展的固体材料快重离子辐照效应研究的部分结果 ,并对建立在兰州重离子加速器 (HIRFL)上的在束穆斯堡尔谱学研究装置及其应用作了简要的介绍.Mssbauer spectroscopy study of irradiation effects induced by swift heavy ions in solid materials were briefly presented.Amorphization phenomenon of yttrium iron garnet irradiated by 1 GeV Ar ions has been investigated. For the first time, the nearly complete amorphous state was observed. Stainless steel 316L samples were irradiated with 54 MeV C ions and phase transformation of the samples was observed. HT 9 ferrite steel was irradiated with 510 MeV C ions. Its phase...     

Production of neutron-rich isotopes in fission of uranium induced by neutrons of 20 MeV average energy

In the context of a parameter study conducted by several laboratories for future European radioactive beam facilities based on fast-neutron induced fission, in particular for the SPIRAL-II project at GANIL, we have measured the yields of neutron-rich isotopes in the mass range of 88 to 144. These nuclei were obtained as fission products of natural uranium bombarded by neutrons of 20 MeV average energy emitted by a thick carbon target irradiated by 50 MeV deuterons. Yields have been measured using on-line mass separation with the ion-guide method. Compared with proton-induced fission at 25 MeV the magnitude of cross-sections, except for the symmetric region, is similar. Z-distributions of isobars have the same width, 0.7 charge units, but their maxima are shifted by about 0.8 charge units, favouring production of the neutron-richer isobars. Our data allow calculations of absolute cross-sections for fission of natural uranium induced by neutrons of about 20 MeV. Received: 10 July 2000 / Accepted: 27 October 2000     

On the observation of a very low atomic displacement threshold energy in cooper

An annealing study has been made on pure and doped copper specimens irradiated with electrons of 0.3 MeV and 0.375 MeV. No recovery has been observed within the measuring sensitivity in the stage-I region. The damage produced in this experiment and that in a HVEM study by Yoshida and Urban is attributed to a subthreshold mechanism.