Self heat generating synthesis of tri-colour lamp phosphors

The simple method for the preparation of phosphors such as aluminates, Y₂O₃, YVO₄ and LaPO₄ by the combustion synthesis described earlier in the literature is reported. It is shown here that the phosphors prepared by such synthesis do not possess all the required characteristics. Suitable modifications by way of annealing at >1200°C in controlled atmospheres, however, can yield the phosphors with characteristics which may fulfil the demands of lamp industry.     

Synthesis and properties of rare earth doped lamp phosphors

Red, blue and green emitting lamp phosphors such as Eu³⁺ doped Y₂O₃ (red phosphor), Eu²⁺ doped Ba_0·64Al₁₂O_18·64, BaMgAl₁₀O₁₇ and BaMg₂Al₁₆O₂₇ (blue phosphors) and Ce_0·67Tb_0·33MgAl₁₁O₁₉ and Eu²⁺, Mn²⁺ doped BaMgAl₁₀O₁₇ (green phosphors) have been prepared by the combustion of the corresponding metal nitrates (oxidizer) and oxalyl dihydrazide/urea/carbohydrazide (fuel) mixtures at 400°–500°C within 5 min. The formation of these phosphors has been confirmed by their characteristic powder X-ray diffraction patterns and fluorescence spectra. The phosphors showed characteristic emission bands at 611 nm (red emission), 430–450 nm (blue emission) and 515–540 nm (green emission). The fine-particle nature of the combustion derived phosphors has been investigated using powder density, particle size and BET surface area measurements. Paper presented at the poster session of MRSI AGM VI, Kharagpur, 1995     

Electronic ballast for multiple fluorescent lamp systems

An electronic ballast for multiple tubular fluorescent lamp systems is presented. The proposed structure has a high value for the power factor, a dimming capability, and soft switching of the semiconductor devices operated at high frequencies. A zero-current switching pulse width modulated SEPIC converter is used as the rectifying stage and it is controlled using the instantaneous average input current technique. The inverting stage consists of classical resonant half-bridge converter with series-resonant parallel-loaded filters. The dimming control technique is based on varying the switching frequency and monitoring the phase shift of the current drained by the filters and lamps in order to establish a closed loop control. Experimental results are presented that validate the theoretical analysis.     

Adaptive fluorescent lamp start control strategy for dimmable magnetic ballast system

Abstract

Based on the environmental concern a novel central dimming system with magnetic ballast driven lighting system, Dimmable Magnetic Ballast System (DMBS), was presented to replace the electronic ballast driven lighting system. To make the DMBS work at a wide range of input voltages for dimming, an Adaptive Fluorescent Lamp Starter (AFLS) which can provide an adaptive preheating time and constant fire voltage for different operation voltage and environmental temperature is proposed in this paper. Experimental results show that features of an adaptive preheating time, a single‐pulse ignition with constant fire voltage, and zero glow current can be achieved. Compared with conventional electronic starters, the proposed AFLS can stretch the lifetime and operating voltage range of the DMBS.     

Relationship between Ba atom emission and electrode temperature in a low-pressure fluorescent lamp

A relationship between emission characteristics of Ba atom as an emitter material and temperature distributions of an electrode in a fluorescent lamp is described, which is measured by using laser-induced fluorescence and black-body radiation method, respectively. In a virgin lamp, a hot spot observed at the electrode edge connected to the power supply is the main source of Ba atom emission. In a long-term-used lamp, it is shown that Ba atom emission, thermionic electron emission in cathode half-cycle and electron collection in anode half-cycle are most active on the hot spot appearing on the center of the electrode.     

Bromine-iodine excimer electric-discharge lamp with continuous UV radiation spectrum

The optical characteristics of a small-size UV lamp filled with a working mixture of xenon and krypton with bromine and iodine vapor and pumped by longitudinal electric discharge have been studied. The lamp emits a resonance atomic line of iodine I* at 206.2 nm (with a full width at half maximum of 0.10 nm) and a continuum in the range 220–390 nm, which is formed by the emission bands of diatomic molecules [XeI(B-X), XeBr(B,D-X), Br₂(B-X), I₂(B-X), and IBr(B-X)]. The optimum partial pressure of iodine vapor is 100–200 Pa, that of bromine vapor ranges from 130 to 400 Pa, and that of heavy inert gases, from 400 to 800 Pa. The average total UV output radiation power was 10–12 W at an efficiency of 10–12%.     

X-ray fluorescent analysis using scattered radiation

The main stages in the development of the theory and technique of X-ray fluorescent analysis (XRFA) based on the method of standard scattered radiation (standard background) are considered. The applicability of different variations of the method for determining low and high concentrations is estimated. The potentialities of a new algorithm for constructing the XRFA calibration characteristic on the basis of a modified universal equation and its application for solving problems in systems of analytical control of benefication and production are demonstrated.     

Ultraviolet radiation emitted by compact fluorescent lamps

To meet the objective of energy efficiency, increasing emphasis on use of energy saver compact fluorescent lamps (CFLs), makes it necessary to analyze the effect of radiation especially ultraviolet (UV) radiation on human health. Various types of CFLs in terms of various shapes, sizes and electrical powers are studied for UV content present in their radiation. Various parameters such as UV irradiance, ratio of UV irradiance to electrical power (η) and ratio of UV power to luminous flux (k), for eighteen types of CFLs are studied to dictate their performance. As expected, both the UV output power and the luminous flux are reduced in the case of double envelope CFLs in comparison to single envelope CFLs, however, the k value is reduced more effectively. For all types of CFLs under study, k₁ for UVA remains less than 104 μW/lm, which is a safe limit for UVA. However, the study demonstrates that the use of CFLs might be detrimental to human health if these are used at shorter distance, e.g., in table lamps.     

Optical radiation emissions from compact fluorescent lamps

There is a drive to energy efficiency to mitigate climate change. To meet this challenge, the UK Government has proposed phasing out incandescent lamps by the end of 2011 and replacing them with energy efficient fluorescent lighting, including compact fluorescent lamps (CFLs) with integrated ballasts. This paper presents a summary of an assessment conducted by the Health Protection Agency in March 2008 to evaluate the optical radiation emissions of CFLs currently available in the UK consumer market. The study concluded that the UV emissions from a significant percentage of the tested CFLs with single envelopes may result in foreseeable overexposure of the skin when these lamps are used in desk or task lighting applications. The optical output of all tested CFLs, in addition to high-frequency modulation, had a 100-Hz envelope with modulation in excess of 15%. This degree of modulation may be linked to a number of adverse effects.     

Synthesis of C-N co-doped nano-CeO2 and dye degradation under compact fluorescent lamp irradiation

Carbon and nitrogen (C-N) co-doped nano-CeO2 was synthesized by the solvothermal method using hexamethylenetetramine (HMT) as a precipitator at 140 degrees C for 24 h. We found that the degradation of acid orange 7 (AO7) was 94.4% and 98.8% with C-N co-doped nano-CeO2 upon irradiation with a 100-watt high-pressure mercury lamp (HML) and a 10-watt compact fluorescent lamp (CFL), respectively. By comparison, TiO2 degraded 68.4% and 43.0% of the AO7 irradiated by HML and CFL, respectively. We found that the degradation efficiencies of AO7 upon irradiation with the 10-watt CFL in the presence of the samples synthesized using different precipitators decreased as follows: CeO2(HMT)> CeO2-TiO2(HMT) > TiO2(HMT) > CeO2(NaHCO3) > CeO2(Na2CO3).     

Compact and flexible optical sensor designed for on-line monitoring

A new on line optical sensor based on light scattering dedicated to real-time monitoring during processing of polymers blends and polymers nanocomposites has been developed. The sensor is designed to monitor the quality of a polymer melt or of a dispersion of nanofillers in a polymeric matrix during the process of extrusion. This sensor presents three openings: two for light sensor setups (one for transmission measurements and the other for 90°-scattered light measurements) and one for the incident laser beam. The experimental validation of this optical sensor has been realized on two materials: poly(methyl methacrylate) (PMMA) and on the nanocomposites obtained by the melt mixing of this polymer matrix with modified montmorillonite (MMT) clays. Experimental results proved the good results in terms of signal repeatability and sensitivity to organoclay particle concentration and structures of nanocomposites respectively.     

Dosimetry of densely ionising radiation with three LiF phosphors for space applications

A new method of thermoluminescence dosimetry of densely ionising radiation based on the ratio of different efficiency-LET functions of three thermoluminescent detectors (TLDs) has been developed. The applied TLD types are: MTS-7 ((7)LiF:Mg,Ti), MCP-7 ((7)LiF:Mg,Cu,P) and MTT-7 (a newly developed (7)LiF:Mg,Ti with modified activator composition and increased response to high-LET radiation). The tests of this method, performed with high-energy ion beams at the HIMAC accelerator within the ICCHIBAN project, proved that good agreement with the true dose values may be achieved even in very complicated mixed fields. The proposed method will be applied for analysis of several thousand TLDs used for the determination of organ doses in an anthropomorphic phantom orbiting outside the International Space Station within the MATROSHKA experiment.     

Additive colour mixing by surface relief gratings utilizing the power spectrum of a fluorescent lamp

Additive colour mixing produced by diffractive grating structures is studied. The gratings produce almost monochromatic primary colours to a selected viewing angle, providing thus a very large colour gamut. The colours inside the gamut are obtained by additive colour mixing in the reflected diffraction order. The amount of a single primary in the additive colour mixing within one colour pixel is determined by the area fraction of the corresponding grating. We demonstrated the concept by fabricating samples which appear white at 30° viewing angle when illuminated by 4000?K fluorescent lamp.     

Autonomous radiation monitoring of small vessels

Small private vessels are one avenue by which nuclear materials may be smuggled across international borders. While one can contemplate using the land-based approach of radiation portal monitors on the navigable waterways that lead to many ports, these systems are ill-suited to the problem. In contrast to roadways, where lanes segregate vehicles, and motion is well controlled by inspection booths; channels, inlets, and rivers present chaotic traffic patterns populated by vessels of all sizes. A unique solution to this problem is based on a portal-less portal monitor designed to handle free-flowing traffic on roadways with up to five-traffic lanes. The instrument uses a combination of visible-light and gamma-ray imaging to acquire and link radiation images to individual vehicles. This paper presents the results of a recent test of the system in a maritime setting.     

Classical microdosimetry in radiation protection dosimetry and monitoring

Classical microdosimetry concerns the measurement and analysis of the spectrum of radiation energy deposition events in simulated microscopic tissue-equivalent sites. Over the past three decades, classical microdosimetry has been extensively applied for the direct measurement of dosimetric quantities, such as the ambient dose equivalent, and for the spectroscopic properties of tissue-equivalent proportional counters that have led to methods of mixed-field analysis and particle identification. This paper reviews some of the special applications of classical microdosimetry such as the determination of kerma coefficients, differential dosimetry and aviation dosimetry. Also reviewed are some of the technological innovations related to the application of microdosimetry in operational health physics and in particular the development of multi-element proportional counters and detectors based on gas microstrip technology.     

Normalization of precision and conformance confirmation in radiation monitoring

The concept of precision standard for the domain of radiation measurements is formulated. In accordance with international recommendations for the quantitative expression of the precision of measurements, the concept of the uncertainty of results is used and its application to problems of radiation monitoring of objects is demonstrated. The basic principles underlying the application of criteria that define the conformance of results to safety standards are formulated. An example of a conformance criterion for a typical situation of radiation monitoring is given.     

Quality assurance of environmental gamma radiation monitoring in Slovenia

Environmental gamma radiation monitoring established in Slovenia consists of a network of multifunctional gamma monitors (MFMs) based on pairs of Geiger-Müller counters and a network of measuring sites with high-sensitive thermoluminiscence dosemeters. The measuring points are evenly spread across Slovenia, located at the meteorological stations and more densely on additional locations around the Krsko NPP. The MFM network has a 2-fold function with one sensor used for the purpose of early warning system in near surroundings of the NPP and the other, more sensitive, for natural radiation monitoring. The paper summarises activities to establish quality assurance of the environmental gamma radiation measurements in Slovenia, with a critical view of the results in comparison with the international standards and recommendations. While the results of linearity and energy dependence tests were satisfying, on-field intercomparison showed that the inherent signal of one of the monitors (MFM) has to be taken into account in the range of environmental background radiation.     

Structure of the temperature profile within a high-pressure gasdischarge lamp operating near maximum radiation efficiency

A singular perturbation technique is used to describe the temperature profile in a wall-stabilized high-pressure gas-discharge arc in the limit of extremely high radiation efficiency. The analysis shows that the profile is characterized by three different regimes, one of which is a transition layer.     

Education and training issues in individual monitoring of ionising radiation

The present article deals with the education and training (E&T) issues of individual monitoring (IM) of ionising radiation, based on the requirements provided by the Basic Safety Standards Euratom Directive and the European Commission Technical Recommendations for IM of external radiation. The structure and the objectives of E&T programmes addressed to the staff of dosimetry services, in order to allow the recognition and ensure the continuity of expertise are discussed. The necessity for the establishment of a national strategy for building competence in IM through information, education, training and retraining programmes, addressed to the individually monitored personnel is underlined. The train the trainers' concept is recognised as being an important tool for optimising resources and transferring the skills necessary for building competence. The conditions under which an efficient train the trainers' approach can be established are discussed. Examples of curricula concerning the key persons involved in the provision of E&T in occupational radiation protection are also given.