Radiation-induced damage in calcium fluoride ionic crystals exposed to high-intensity ultraviolet and vacuum ultraviolet light

An experimental setup for studying optical materials under the action of plasma-emitted intense (up to 10⁵ W/cm²) ultraviolet and vacuum ultraviolet radiation is described, and methods for estimating the radiation damage are developed. The damage produced in calcium fluoride ionic crystals at ～300 K by low (10³ rad) and moderate (10⁶ rad) absorbed doses is experimentally estimated.     

Development of NaCl:K(6T) phosphor for thermoluminescence dosimetry

The present paper discusses the development of the NaCl:K (10 ^–1 molar fraction of potassium) phosphor as dosimeter material for beta-radiation thermoluminescent dosimetry (TLD). The TLD grade NaCl:K(6T) material was prepared by annealing the NaCl:K powder obtained from aqueous solution by the method of recrystalization and annealed at 600°C for two hours in open air. It is observed that thermal glow curves of NaCl:K(6T) specimen exhibit well defined glow peak around 170°C alongwith a weaker peak at lower temperature. The high-temperature peak is found to grow supralinearily with increase in beta dose in the range 10–2×10³ rad. Since the nature of glow curves under the influence of different doses remains more or less identical, it is believed that the phosphor does not undergo radiation damage and give high intrinsic TL around peak III. Examination of the system for fundamental dosimetry requirement shows that the NaCl:K(6T) material can be used as a suitable TLD material in beta radiation.     

Effect of high-dose irradiation on the optically stimulated luminescence of Al2O3:C

This paper examines the effect of high-dose irradiation on the optically stimulated luminescence (OSL) of Al2O3:C, principally on the shape of the OSL decay curve and on the OSL sensitivity. The effect of the degree of deep trap filling on the OSL was also studied by monitoring the sensitivity changes after doses of beta irradiation and after step-annealing of samples previously irradiated with high doses. The OSL response to dose shows a linear-supralinear-saturation behavior, with a decrease in the response for doses higher than those required for saturation. This behavior correlates with the sensitivity changes observed in the samples annealed only to 773 K, which show sensitization for doses up to 20-50 Gy and desensitization for higher doses. Data from the step-annealing study leads to the suggestion that the sensitization is caused by the filling of deep electron traps, which become thermally unstable at 1100-1200 K, whereas the desensitization is caused by the filling of deep hole traps, which become thermally unstable at 800-875 K, along with a concomitant decrease in the concentration of recombination centers (F+ -centers). Changes in the shape of the OSL decay curves are also observed at high doses, the decay becoming faster as the dose increases. These changes in the OSL decay curves are discussed in terms of multiple overlapping components, each characterized by different photoionization cross-sections. However, using numerical solutions of the rate equations for a simple model consisting of a main trap and a recombination center, it is shown that the kinetics of OSL process may also be partially responsible for the changes in the OSL curves at high doses in Al2O3:C. Finally, the implication of these results for the dosimetry of heavy charged particles is discussed.     

Effect of high gamma dose on the PADC properties

The effect of the properties of PADC nuclear track detectors after exposure to high doses of gamma absorbed doses up to 5×10⁵ Gray (50 Mrad) were studied. The gamma source was a 9.03 PBq (244 KCi), Co-60 source. Results indicate that each of the bulk etch rate (V_b), the tracks etch rate (V_t) and the sensitivity (V) of the detectors increases with the high gamma absorbed dose, but there is a drop in these parameters at the low gamma absorbed dose. Signs of surface roughness were observed by increasing the gamma absorbed doses and changes in color observed for doses larger than 2×10⁵ Gray. The temperature of detectors during irradiation time reached 41°C. The fission fragment tracks (from Cf-252 source) disappeared quickly within the etching time (minutes) for total absorbed doses greater than 3×10⁵ Gray due to their high bulk etch rate.     

Temperature effect during the gamma irradiation of CaSO4: Dy

The effect of the irradiation temperature of CaSO4 doped with Dy was investigated in the interval of 77-298 K. The difference in the response at different temperatures increases with the dose. The response for the system at 77 K was about 20% lower in relation to room-temperature readings. The behavior of CaSO4:Dy at low temperatures shows a linear pattern for doses in the range studied. The response is very reproducible and is a good dosimetric system for samples that are irradiated at low temperature.     

Magnetoplastic effect in irradiated NaCl and LiF crystals

The effect of low x-ray irradiation doses (≈10² rad) on the magnetoplastic effect — the detachment of dislocations from paramagnetic centers under the action of an external magnetic field B — in alkali-halide crystals has been investigated. The measurements were performed on LiF crystals and three types of NaCl crystals, differing in impurity content. The dependence of the mean free path l of the dislocations on the rotational frequency ν of a sample in a magnetic field was especially sensitive to low irradiation doses. In unirradiated crystals this dependence is a single-step dependence and is characterized by a critical frequency ν _c ∝B ² above which the magnetoplastic effect is not observed. The frequency ν _c depends only on the type of paramagnetic centers, and not on their density. Even the lowest irradiation dose employed (<100 rad) leads to a sharp restructuring of the dependence l(ν), converting it into a two-step dependence (for edge dislocations) with an additional critical frequency ν _c2, that is insensitive to the irradiation dose, and that corresponds to the appearance of magnetically sensitive stoppers of a new type under irradiation. The initial critical frequency ν _c1, as a rule, also varies with the dose, reflecting the change in state of the impurity complexes (Ca in NaCl and Mg in LiF). Specifically, it is shown for NaCl(Ca) crystals that as the irradiation dose increases, the frequency ν _c1 increases, gradually approaching the value ν _c2, so that by the time the dose is ≈300 rad, the dependence l(ν) once again becomes a single-step dependence, dropping sharply only for ν⩾ν _c2. It is shown that the addition of a small number of Ni atoms to a NaCl crystal makes the Ca complexes radiation resistant, and the critical frequency ν _c1 corresponding to them initially equals ν _c2 for crystals with no Ni. The recombination kinetics of radiation defects in the case in which the samples are irradiated under a tungsten lamp was investigated. A possible physical model of the observed dependences is discussed. Zh. éksp. Teor. Fiz. 111, 615–626 (February 1997)     

Spectrally resolved thermoluminescence of highly irradiated LiF:Mg,Cu,P detectors

Well known, widely applied high sensitive thermoluminescence (TL) detector LiF:Mg,Cu,P (MCP-N) was investigated. This paper analyses changes of the TL emission spectrum of MCP-N after irradiation with ultra high doses (up to 500 kGy). Spectral dependence of TL on dose is very complex especially in the region of very high doses (>1 kGy). As a general trend we found that the number of peaks increases with dose in the long-wavelength region indicating new types of recombination centres (RCs). Wavelength peak positions for increasing doses are quite stable. Only some of them show slight red-shift.     

NMOS器件不同剂量率γ射线辐射响应的理论预估

介绍了利用线性响应理论预估CC4007-NMOS器件在剂量率01，23，44和91rad(Si)/s下的辐射损伤情况，理论预估值和试验结果符合得比较好.利用线性响应理论预估了CC4007-NMOS器件从低剂量率到高剂量率环境下的辐射损伤及25℃长时间退火情况，结果表明，在相同偏压下，高剂量率辐照加室温退火所引起的阈值电压漂移量在误差容许的范围内等于低剂量率辐照的漂移量，两者总的时间相同.利用线性响应理论预估CC4007-NMOS器件在不同剂量率辐照下的失效剂量.     

GaN基多量子阱蓝光LED的γ辐照效应

本文用4×104Ci(1Ci=3.7×1010Bq)的60Co源(剂量率2×105rad(Si)/h)对GaN基InGaN/GaN多量子阱蓝光LED进行5种剂量的γ射线的辐照实验.通过辐照前后蓝光LED的波长、色纯度、最大半峰宽(FWHM)和电流-电压(I-V)、电流-光通量(I-F)等电光学特性分析,得到γ射线对GaN基LED器件的辐照效应.结果发现,辐照后LED器件的发光一致性和均匀性变差,在20mA工作电流下,最大剂量下器件发光强度衰减近90%,光通量衰减约40%,并得到器件的抗辐照能力的参数τ0Kγ为4.039×10-7rad.s-1,发现较低的正向偏压下(小于2.6V)器件的饱和电流随辐照总剂量增大而增大.     

质子注入MBE碲镉汞n-on-p结性能研究

基于中波响应波段的分子束外延碲镉汞薄膜材料成功制备出不同质子注入剂量的大光敏元(5 00μm×500μm)的n-on-p结构的p-n结，并对相应的p-n结的电流-电压（I-V）特性进行 了研究.质子注入剂量为2×10¹⁵cm^-2时R₀A达312.5Ω ·cm²，低温热处理后达490Ω·cm². 关键词： I-V特性 碲镉汞薄膜 质子注入 p-n结     

Relative thermoluminescence effects of alpha‐ and beta‐ radiation

Abstract

A study has been made of the relative thermoluminescence response to α- and β-radiation of six phosphors (two types of natural fluorite, CaF₂: Mn, CaF₂: Tb, CaSO₄: Mn and quartz) using samples which are thin compared to the range of the α-particles. The α- and β-radiations induce the same glow peaks, but at low doses (<100 rads) the TL response per rad of α-radiation (3.7 MeV) is less than that per rad of β-radiation in all the glow peaks studied. The α-efficiency ranges from 53 per cent for CaF₂: Mn to 2 per cent for quartz (110°C peak) at 3.7 MeV and decreases with decreasing α-particle energy. At higher doses (10⁶?10⁷ rads) the TL responses to α- and β-radiation become equal within 15 per cent; most of the glow peaks are in or near saturation at these doses. The higher the β-dose at which a peak saturates, the higher is the α-efficiency (at low doses) of that peak. The results support the interpretation that the α-efficiency is low because the phosphor is near or in saturation in the localized region near the α-path. This interpretation is given quantitative support by a theoretical calculation of the localized energy-density.     

反应堆压力容器钢A508-3辐照硬化的剂量率效应研究

针对不同剂量率对国产反应堆压力容器钢(Reactor Pressure Vessel,RPV)A508-3辐照硬化的影响,利用3.5 MeV的Fe离子在3种不同剂量率(0.1,0.5和1.0 dpa/h)下将样品辐照至4个不同剂量点(0.1,0.3,1.0和3.0 dpa),采用纳米压痕技术表征样品在不同辐照条件下的硬...     

Storage mechanism and OSL-readout possibility of Li2B4O7:Mn (TLD-800)

Thermoluminescence, dose dependences, and EPR of Mn-doped lithium tetraborate are studied. Mn is shown not to change a charge state during energy storage and release. Mn²⁺ amount decreases only at very high doses. The amount of Mn²⁺ depends on the sintering temperature and increases with temperature increase due to reduction of Mn from a higher oxidation state. X-irradiation creates optical absorption bands in Li₂B₄O₇:Mn. Optical stimulation in the UV band is effective for OSL-readout and destroys dosimetric TL peaks. The model of energy storage and release is discussed.     

Radiation-induced transmission loss in optical materials at infrared wavelengths

Information concerning the effect of irradiation on the optical properties of materials in the infrared, sub-mm-and mm-wavelength regions is of increasing importance in fusion plasma diagnostics. The radiation induced transmission loss of a number of materials has therefore been investigated at wavelengths in the ranges 200 nm to 40 μm and 0.23 to 2.0 mm. The samples were irradiated with doses of up to 10¹⁰ rad in a nuclear reactor. While germanium shows considerable transmission loss at doses as low as 10⁶ rad, and the transmission of TPX decreases at 10⁹ rad, other materials, e.g. fused quartz and possibly ZnSe, exhibit sufficient radiation hardness for use in fusion plasma diagnostics.     

Microstructural changes induced in borosilicate glasses by 1 MeV electrons

Radiation damage to borosilicate glass has been studied using a high voltage electron microscope to simultaneously generate and image structural changes At low doses and dose rates (φ ? 5 × 10²⁴ electrons m^-2, F ? 5 × 10²² el m^-2 s^-1), ionic depletion generates a new crystalline phase rich in S₁O₂ For incubation doses exceeding 5 × 10²⁴ electrons m^-2, gas bubbles are observed High damage rates are necessary for bubble nucleation though not for their subsequent growth The critical nucleation flux increases rapidly with irradiation temperature, whereas the gas precipitation efficiency remains constant above 300 K.     

Thermal redistribution of indium in amorphous silicon layers

A new impurity redistribution mechanism is reported for low temperature annealing (525°C) of (100) Si samples implanted with high indium doses. The redistribution is a strong function of implant dose and is believed to be stress related.     

Correlation between base damage and phosphate release from irradiated aqueous solution of thymidine monophosphate in O2 and N2

Steady state radiolyais of dilute aqueous (neutral) solution of thymidine monophosphate (TMP) with reference to base damage and inorganic phosphate release (Pi) are reported in O₂ or N₂ saturated conditions. Dose response are shown graphically and an inverse correlation between the two observed. We believe that in nitrogen conditions, reducing radicals are also responsible for base damage at low doses and become available for phosphate release when base damage saturates at high doses     

Metal adsorption of gamma-irradiated carboxymethyl cellulose/polyethylene oxide blend films

Blend films of different ratios of carboxymethyl cellulose (CMC)/polyethylene oxide (PEO) were prepared by the solution casting method. To investigate the effect of irradiation on all properties of prepared blend, it was exposed to different gamma irradiation doses (10, 20, and 30?kGy). Physical properties such as gel fraction (GF) (%) and swelling (SW) (%) were investigated. It was found that the GF (%) increases with increasing irradiation dose up to 20?kGy, while SW (%) decreases with an increase in the irradiation doses for all blend compositions. Moreover, the structural and mechanical properties of the prepared films were studied. The results of the mechanical properties obtained showed that there is an improvement in these properties with an increase in both CMC and irradiation dose up to 20?kGy. The efficiency of metal ions uptake was measured using a UV spectrophotometer. The prepared films showed good tendency to absorb and release metal ions from aqueous media. Thus, the CMC/PEO film can be used in agricultural domain.     

The real-time gamma radiation dosimetry with TeO2 thin films

A detailed study of the effect of gamma radiation on the current–voltage characteristics of the TeO₂ thin films of different thicknesses, prepared by thermal evaporation in a vacuum, has been carried out for a much wider range of the gamma radiation doses than made here-to-fore. Subsequently, for the thin films of different thicknesses at different applied voltages, the variations of the current density with dose have been obtained. The current density increases near linearly with the gamma radiation dose up to a critical radiation dose, a dose value higher for the thicker films and decreases thereafter. The sensitivities of these TeO₂ thin films at different applied voltages have been found to be in the range 1.2–37.0 nA/cm²/μGy. Correspondingly, the detection limits have also been estimated and have been found to be in the range 0.22–2.16 mGy. Clearly, the TeO₂ thin films have high potential for their use as real-time gamma radiation dosimeters in monitoring the gamma radiation doses under a variety of practical situations involving low level to high level of the doses.