Lifetime estimation of thermoluminescence traps in granitic quartz

Abstract

Thermoluminescence (TL) traps in granitic quartz are potential geochronometers for ages of up to billions years. TL sensitivity is believed to be a measure of the population of TL traps. Their lifetimes can be roughly estimated either by isothermal annealing or by an empirical approach. The former is applicable to radiation sensitive traps corresponding to > 200°C TL when first order kinetics is assumed. The lifetimes are found to be several orders longer than those of trapped electrons. The lifetimes of thermally sensitive traps (< 200°C TL) are estimated from empirical curves that are constructed from data from granitic quartz of known age. It is found that the lifetime increases with the trap depth.     

Hot electron studies of lattice damage created in silicon by implantation of 2.8 MeV protons

Abstract

In this paper we report the results of a study of the annealing properties of the ionized defect density associated with the damage created in the silicon lattice by implantation of 2.8 MeV protons at room temperature. In particular, the annealing of damage created by implanting to a level of 4.43 × 10¹² protons/cm² is reported. The resulting isochronal annealing curve covered the temperature range from 70°C to 460°C. Two major annealing stages are discussed, one a broad stage between 70°C to 200°C and the other an abrupt annealing stage between 440°C to 460°C. Between the temperature range 200°C to 440°C the number of ionized defects remained relatively constant. Above 460°C no detectable effects of the proton implantation remained.     

Neutron scattering in Ag+ and Na+ β-aluminas

Na⁺ and Ag⁺ β-alumina for various stoichiometries and for various hydration states have been studied by neutron scattering using incident energy of 0.8 meV with a resolution of 20 μeV in the 200–325° C temperature range. From the weak quasielastic signal (QES) observed for the non- stoichiometric (NS) Ag⁺ β-alumina a translational diffusion constant D_t has been estimated at about 10^-5 cm² s^-1 at 200°C. No such QES has been observed for stoichiometric Ag⁺ and Na⁺ compounds. The dehydration of Na⁺ β-alumina has been evidenced by the disappearance of the broad QES above 300°C; correlatively the low frequency inelastic spectrum of Na⁺ of β-alumina is changed.     

Remote Temperature Sensor Based on the Up-Conversion Fluorescence Power Ratio of an Erbium-Doped Silica Fiber Pumped at 975 nm

Abstract

This article presents experimental results demonstrating the performance of an erbium-doped silica fiber as a remote temperature sensor in the interval from 20°C to 200°C. The sensor is based on the change in the fluorescence intensity ratio of two spectral bands as a function of temperature. The green fluorescence signal was generated by up-conversion processes in the erbium-doped fiber pumped at 975 nm. A radiometric analysis was applied to the erbium-doped fiber to evaluate its performance as a temperature sensor, and the results from this analysis were compared against other rare-earth-doped fiber sensors that utilize the intensity ratio technique.     

Growth of he bubbles in al during annealing

Abstract

The temperature dependent growth of He bubbles in Al films implanted at room temperature to various He concentrations is investigated by electron energy-loss spectroscopy (EELS) and transmission electron microscopy (TEM). EELS reveals even the weakest changes in He density within the bubbles by measuring the pressure shift of the He 1¹S₀?2¹P₁ transition. This is applied to investigate the mechanisms driving the growth of bubbles in the temperature range 20°C ? T ? 500°C. For T?200°C indication is found that bubbles relax by emission of interstitial dislocation loops. At higher temperatures bubble migration and coalescence under absorption of thermal vacancies is evident. The final state is characterized by large cavities filled with He at low pressure as evidenced by the detection of the atomic He series.     

Temperature dependence of luminescence time-resolved spectra from quartz

Pulsed optical stimulation of luminescence has been used to study the thermal dependence of luminescence lifetimes in quartz over the temperature range 20–200°C. Time-resolved spectra for lifetime analysis were recorded from samples of quartz over a dynamic range of 64 μs following stimulation of luminescence by pulsed 525 nm green light emitting diodes (LEDs) using an 11 μs pulse and 12% duty cycle. It has been demonstrated that an increase in measurement temperature generally leads to a decrease in lifetimes from about 30 μs at 20°C to about 7 μs at 200°C. The form of the decrease is influenced by the initial optical or thermal pre-treatment of samples.     

Ammonia gas sensor based on SnO2 nanostructure with the enhanced sensing capability at low temperatures

ABSTRACT

We investigated the gas-sensing performance of tin oxide nanowires for ammonia gas at low temperature (～ 50°C). Tin oxide nanostructures were deposited at 1000°C and 1100°C on gold-coated silicon substrates using the physical vapor deposition method. Gas-sensing measurements were made for ammonia gas at various strengths (i.e. 50, 100 and 200?ppm) and the sensing performance was compared at low temperature for both the samples e.g. nanostructures deposited at 1000°C and 1100°C. Due to the highly oriented structure, the sample deposited at 1000°C shows high sensing capability at low temperature as compared to the regular tetragonal phase observed at 1100°C. The morphological and structural properties of nanowires were systematically examined using the scanning electron microscopy and X-ray diffraction.     

锑化铟中载流子的复合过程

用定态光电导及光磁电的方法测量了p型n型InSb在85—290°K之间的电子及空穴的寿命。在室温附近,所有样品的截流子寿命都趋于同一值,在290°K时为3×10^-8秒。从寿命的绝对值及温度依赖关系,以及掺杂对寿命的影响,可以肯定在室温附近起主要作用的复合过程是带间碰撞复合过程。在200°K以下,p型样品中的电子寿命与空穴寿命有很大差别,表明有陷阱作用。用位于价带之上0.05eV的复合中心及位于导带之下0.11eV的电子陷阱能完满地解释200°K以下的寿命与温度的依赖关系。     

Optical behaviour of melting for a thin metal film

Reflectance measurements have been performed for gallium films at normal incidence (from 0.3 to 0.9 μm) in terms of temperature (from -20°C to + 40°C). The basic results are: (i) a drastic change in reflectance when melting occurs (about 20% at 0.6 μm), and (ii) a shift in the temperature of the solid-liquid transition with the thickness of the film which only takes place on and after the second melting (about 7°C for a film 250A?thick).     

Fundamental absorption edge of evaporated amorphous WO3 films

The fundamental absorption edge of evaporated WO₃ films is investigated. The optical gap of the virgin film is estimated to be 3.41 eV at room temperature and it decreases with increase of annealing temperature up to 200°C. Annealing at 300°C leads to change in the spectral shape, which is caused by crystallization. For the films annealed at 200°C, temperature coefficient of the optical gap is estimated to be ?2×10^?4 eV/K and the slope of Urbach's tail is found to be independent of measuring temperature up to 200°C. With electrolytic coloration, shift of the optical gap toward higher energy is observed. Magnitude of this shift is estimated to be 0.05 eV at the color center concentration of 7.5×10²¹ cm^?3 when H⁺ electrolyte is used. If Li⁺ electrolyte is used, the magnitude of this shift is about three times larger than in the case of H⁺ electrolyte. This fact is interpreted by a small change in the host matrix structure owing to the injection of proton or Li⁺ during coloration.     

Die Verfestigungserholung von plastisch verformten Steinsalzeinkristallen

Cylindrical rock salt single crystals have been plastically deformed by compression in the [001]-direction at room temperature to shear stresser τ _E of 200 N/cm² and 350 N/cm², respectively. Isochronal annealing experiments reveal, that workhardening recovers at >300° C. The characteristic annealing temperature was found between 400° C and 450° C. At 600° C the residual workhardening still amounts to 15–20%. The isochronal reduction of screw dislocation density between 400 and 600° C shows qualitatively the same behaviour as recovery of workhardening. From the isothermal annealing curves of the samples deformed to 200 N/cm² the activation energy for recovery of workhardening was found to be about 1 eV. Assuming that the kinetics of recovery can be explained by processes distributed in activation energy, an approximate spectrum of activation energies (with a maximum arising at ～1 eV) has been evaluated. The results show that recovery of workhardening after low deformation (stage I of the stress strain curve) is mainly due to the dislocations.     

Positron annihilation in electron-irradiated n-type gap crystals

Abstract

The defects in n-GaP crystals irradiated by 2.3 MeV electrons up to 1 × 10¹⁹ cm^?2 at RT were studied by means of positron annihilation (angular correlation) and electrical property measurements. It was found that positrons are trapped in some radiation-induced vacancy-type defects (acceptors) but that the effect saturates at high electron fluences (D1 × 10¹⁸ cm^?2). The trapping rate in irradiated samples increases with temperature in the range 77–300 K. Post-irradiation isochronal annealing reveals the positron traps clustering at about 200–280°C. All positron sensitive radiation-induced defects disappear upon annealing up to 500°C.     

Influence of Nitrogen Supply and Temperature on Stable Carbon Isotope Ratios in Plants of Different Photosynthetic Pathways (C3, C4, CAM)

Abstract

One representative species of each of the three photosynthetic pathways (C₃, C₄, CAM) were cultivated in growth chambers with high and low nitrogen nutrition level respectively once at 20°C day/13°C night temperature, once at 30°C day/13°C night. Leaf conductances and δ¹³C values of the leaves of each plant were determined. At 20°C day temperature the C₃ species showed higher leaf conductance with low nitrogen nutrition level than with high nitrogen level, which is also reflected in a more negative δ¹³C value, whereas both C₄ and CAM plants did not respond in this manner to nitrogen supply. An increase of day temperature to 30°C diminished the significant response of the C₃ plant, while the response of C₄ and CAM representatives to nitrogen nutrition did not change markedly.     

The properties of some derivative autocorrelation functions computed with the atom-atom potential

High-resolution quasi-elastic neutron-scattering measurements have been made on two nematogens: DMBCA with a nematic range 108 to 119°C, and 5CB and a tail-deuteriated sample (D5CB), having a nematic range 22·6 to 35·1°C.

Results on 5CB in the crystal phase at ～18°C showed no significant quasielastic broadening, which means that any random motions of the alkyl chain are slower than about 5 × 10⁹ rad s^-1. Measurements were made at a single temperature in the nematic phases on specimens aligned in a magnetic field of 0·25T; for DMBCA with scattering vector Q⊥n (n is the nematic director) and for 5CB and D5CB with Q⊥n and Q∥n and also on the isotropic liquid phase of D5CB at 45°C. Analysis of the coherent scattering from nematic D5CB at Q = 1·2 Å^-1 and 25°C gave an order parameter <P ₂>=0·55, close to the simple mean field value for this temperature. The coherent scattering from DMBCA is too weak to allow this experiment to be performed.

The most remarkable qualitative feature of the results is the close similarity of the scattering law S(Q, ω) for D5CB (and 5CB) with Q⊥n and Q∥n. Analysis of the results in all cases was made using values for the translational diffusion constants measured previously. Corrections for multiple scattering are shown to be important and a single simple model has been devised which fits the line shapes of all the results for D5CB in nematic (Q⊥n and Q∥n) and isotropic liquid phases and DMBCA. The model involves uniaxial rotational diffusion about the long molecular axis m coupled to a displacement along the rotation axis giving a net rotation in a plane whose normal makes an angle ∝ relative to the direction m. Values for the rotational diffusion constant D _rd ns^-1 are as follows: D5CB, 25°C, 6 (∝ ～ 50°); 45°C, 10. DMBCA, 112°C, 16, (all ±10–15 per cent).

The results for D5CB and 5CB are so similar that no additional detailed model fitting was attempted for the fully hydrogenous sample and it is concluded that while the motion of the alkyl tails is freer, the time scale of the motions is not more than about a factor of 2 faster than that of the molecular cores.     

Investigation of temperature dependence of neutron yield and electron screening potential for the d(d, n)3He reaction proceeding in deuterides ZrD2 and TiD2

The temperature dependence of the enhancement factor for the dd reaction proceeding in TiD₂ and ZrD₂ is investigated. The experiments were carried out at the Hall pulsed ion accelerator (INP, Polytechnic University, Tomsk, Russia) in the deuteron energy interval 7.0?C12.0 keV and at temperatures ranging from 20 to 200°C. The values obtained for the electron screening potentials indicate that the dd reaction enhancement factor does not depend on the target temperature in the range 20?C200°C. This result contradicts the conclusions drawn by the LUNA Collaboration from their work.     

Positron annihilation studies on molybdenum irradiated with neutrons at temperatures from 350° C to 1000° C

We performed measurements of positron lifetimes and the lineshape parameter on molybdenum samples irradiated with neutrons at temperatures from 350° to 1000° C. The results show that the correlation between swelling and positron characteristics depends strongly on irradiation temperature. From 350° to 500° C, ΔS, and notI ₂, correlates with sweelling; from 500° to 800° C, both ΔS andI ₂ correlate with swelling; and at higher temperatures, none of them correlates with swelling.     

Performance of a Single-Family Heat Pump at Different Working Conditions Using Small Quantity of Propane as Refrigerant

The performance of a domestic heat pump that uses a low quantity of propane as refrigerant has been experimentally investigated. The heat pump consists of two minichannel aluminium heat exchangers, a scroll compressor, and an electronic expansion valve. It was charged with the minimum amount of refrigerant propane required for the stable operation of the heat pump without permitting refrigerant vapor into the expansion valve at incoming heat source fluid temperature to the evaporator of +10°C. The inlet temperature of the heat source fluid passing through the evaporator was varied from +10°C to ?10°C while holding the condensing temperature constant at 35°C, 40°C, 50°C, and 60°C, respectively. The minimum refrigerant charges required at above-tested condensing temperatures were found to decrease when the condensing temperature increased and were recorded as 230 g, 224 g, 215 g, and 205 g, respectively. The results confirm that a heat pump with 5 kW capacity can be designed with less than 200 g charge of refrigerant propane in the system. Due to the high solubility of propane in compressor lubrication oil, the amount of refrigerant which may escape rapidly in case of accident or leakage is less than 150 g.     

Ferroelastic detwinning of the high-temperature superconductor YBa2Cu3O7-δ

Crystals of YBa₂Cu₃O_7-δ (YBC) were prepared using a flux technique. The as-grown crystals were typically on the order of 200 μm × 200 μm × 50 μm, where the 50 μm dimension is in the c-direction. Ferroelastic behavior was observed by applying a uniaxial stress along the [100]_tet-direction using a specially-designed fixture which was mounted to a programmable hot/cold stage of a polarizing reflected-light microscope. Domain wall motion was observed for temperatures greater than 200°C, and complete poling was accomplished at stresses on the order of 50–100 MPa at temperatures of 350–400°C. An ionic diffusion-activated mechanism is suggested.     

Dimpling—A new manifestation of ion-produced lattice damage

Abstract

Bombardment of thin (1–10 μ) single crystal targets with energetic ion beams has been found to result in macroscopic distortion of the thin film in the bombarded region. This effect, which has been euphemistically termed a ‘dimple’, is readily observed with the naked eye even at relatively low particle fluence. A useful first-order model has been developed which interprets the dimpling as an expansion of the bombarded region. For very thin samples, this expansion can be accommodated by bowing of the crystal out of the original crystal plane. For this simple model, the fractional expansion is proportional to (δ/d)² where δ is the maximum displacement from the original crystal plane and d is the diameter of the bombarded area. This measurement allows expansioh to be determined with a sensitivity comparable to or better than the most sensitive existing methods.

For silicon about 3 μ thick bombarded by 1.8 MeV He ions, the expansion increases essentially linearly with fluence at the lowest fluence (below about 10¹⁵ to 10¹⁴ cm^?2). In this region about 0.001 atomic volumes are added per incident ion. As the fluence is increased, the apparent expansion begins to increase more rapidly than linearly but approaches a saturation value at the highest fluence (about 10¹⁸ cm^?2). The effect of particle flux, incident energy, and bombardment temperature is discussed as well as some preliminary results on C ion produced dimples in Si and the behavior of Ge samples.

Thirty-minute isochronal annealing of silicon samples irradiated with He ions at room temperature shows reverse annealing for temperatures up to about 200–300°C. The dimple begins to anneal at 300°C and disappears after annealing to 600–700°C.

After irradiation, the dimpled region absorbs light more strongly in the visible and near IR region. This disappears with annealing before the dimple itself completely disappears and is felt to be largely due to scattering from defect clusters.     

Nanocrystallization of an amorphous Fe<Subscript>80</Subscript>B<Subscript>20</Subscript> alloy during severe plastic deformation

The structural evolution of an amorphous Fe₈₀B₂₀ alloy subjected to severe plastic deformation at room temperature or at 200°C was studied. Deformation leads to the formation of α-Fe nanocrystals in an amorphous phase. After room-temperature deformation, nanocrystals are localized in shear bands. After deformation at 200°C, the nanocrystal distribution over the alloy is more uniform. Possible causes of the crystallization of the amorphous phase during severe plastic deformation are discussed.