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[en] A new model was developed for the characterization and quantification of the 'inaccessible' discharge parameters in closed tube high power electrodeless fluorescent lamps. The results obtained applying the model are verifiable by means of a simple comparison of the primary equivalent resistance and reactance as a result of the measured V1, I1, ψ1 with the equivalent primary resistance and reactance inferred from the proposed model. The results are in good agreement at all operating lamp power levels. What is unexpected is the capacitive behaviour of the inductive coupled plasma at lower powers. The investigation method is suitable for the optimization of high power electrodeless lamps with a long discharge path operated at low frequencies, in order to improve the efficiency and the system stability, especially if the lamp has to be dimmed
[en] A review of the different technologies used to dose mercury in fluorescent lamps is presented. Conventional liquid mercury dosing is gradually being replaced with more reliable and environmentally friendly solutions that enable a significant reduction of the amount of mercury introduced in the lamp, so as to cope with more stringent regulations issued to minimize the environmental impact of exhausted lamps. This paper will review the most advanced novel methods to assure an accurate and fine dosing of mercury in fluorescent lamps, especially focusing on solutions based on the use of solid alloys
[en] Two optically brightened commercial papers were subjected to 72 hours continuous exposure to graphic arts daylight simulating fluorescent lamps at 1.4 and 4.4 klux. At the higher illuminance level, a CIELAB colour difference of 1.0 was reached in approximately 3 and 50 hours for the two papers. The colour differences produced by the 1.4 klux exposure were greater than that predicted by assuming a linear relationship between intensity and colour change, by a factor of 1.8.
[en] In this study, in situ exposure assessment of both electric and magnetic fields of different intermediate frequency (IF) sources is investigated. The authors investigated smart boards and touch-screens, energy-saving bulbs, fluorescent lamps, a portable hearing unit and an electro-surgical unit (ESU). For most of these sources, the electric field is the dominating quantity. International Commission on Non-Ionizing Radiation Protection reference levels are exceeded for touch-screens (44 kHz: up to 155.7 V m-1 at 5 cm), energy-saving bulbs (38-52 kHz: up to 117.3 V m-1), fluorescent lamps (52 kHz: up to 471 V m-1 at 5 cm) and ESUs (up to 920 kHz: 792 V m-1 at 0.5 cm). Magnetic field strengths up to 1.8 and 10.5 A m-1 were measured close to the ESU and portable hearing unit (69 V m-1), respectively. Large differences of measured field values exist among the various operating modes of the IF equipment. Compliance distances for general public range from 15.3 cm (touch-screen) to 25 cm (fluorescent lamps). (authors)
[en] The external electrode fluorescent lamp (EEFL) is operated in a high frequency mode because the lamp lighting is basically a dielectric barrier discharge. The self-discharge synchronization is defined by synchronizing the self-discharge time of the dielectric wall charge with the voltage rising and falling time. It is shown that for the self-discharge synchronization a high brightness is obtained in the multi-lamps backlight connected in parallel with the EEFLs operated with square waves from a switching inverter. The frequency for self-discharge synchronizing is also shown to increase as the driving voltage increases
[en] We fabricated three types of high luminous efficacy white light emitting diodes (LEDs). The first was a white LED with a high luminous efficacy (ηL) of 249 lm W-1 and a high luminous flux (φv) of 14.4 lm at a forward-bias current of 20 mA. This ηL was approximately triple that of a tri-phosphor fluorescent lamp (90 lm W-1). The blue LED used as the excitation source in this white LED had a high output power (φe) of 47.1 mW and a high external quantum efficiency (ηex) of 84.3%. The second was a high-power white LED, fabricated from the above high-power blue LED, and had a high φe of 756 mW at 350 mA. φv and ηL of the high-power white LED were 203 lm and 183 lm W-1 at 350 mA, respectively. The third was a high-power white LED fabricated from four high-power blue LED dies. φv and ηL of the high-power white LED were 1913 lm and 135 lm W-1 at 1 A, respectively. The white LED had a higher flux than a 20 W-class fluorescent lamp and 1.5 times the luminous efficacy of a tri-phosphor fluorescent lamp (90 lm W-1).
[en] Purpose: The objective of this study is to evaluate radiation sensitivity of optical stimulated luminance dosimeters (OSLDs) by accumulated dose and high dose. Methods: This study was carried out in Co-60 unit (Theratron 780, AECL, and Canada) and used InLight MicroStar reader (Landauer, Inc., Glenwood, IL) for reading. We annealed for 30 min using optical annealing system which contained fluorescent lamps (Osram lumilux, 24 W, 280 ∼780 nm). To evaluate change of OSLDs sensitivity by repeated irradiation, the dosimeters were repeatedly irradiated with 1 Gy. And whenever a repeated irradiation, we evaluated OSLDs sensitivity. To evaluate OSLDs sensitivity after accumulated dose with 5 Gy, We irradiated dose accumulatively (from 1 Gy to 5 Gy) without annealing. And OSLDs was also irradiated with 15, 20, 30 Gy to certify change of OSLDs sensitivity after high dose irradiation. After annealing them, they were irradiated with 1Gy, repeatedly. Results: The OSLDs sensitivity increased up to 3% during irradiating seven times and decreased continuously above 8 times. That dropped by about 0.35 Gy per an irradiation. Finally, after 30 times irradiation, OSLDs sensitivity decreased by about 7%. For accumulated dose from 1 Gy to 5 Gy, OSLDs sensitivity about 1 Gy increased until 4.4% after second times accumulated dose compared with before that. OSLDs sensitivity about 1 Gy decreased by 1.6% in five times irradiation. When OSLDs were irradiated ten times with 1Gy after irradiating high dose (10, 15, 20 Gy), OSLDs sensitivity decreased until 6%, 9%, 12% compared with it before high dose irradiation, respectively. Conclusion: This study certified OSLDs sensitivity by accumulated dose and high dose. When irradiated with 1Gy, repeatedly, OSLDs sensitivity decreased linearly and the reduction rate of OSLDs sensitivity after high dose irradiation had dependence on irradiated dose
[en] Radially resolved line-of-sight intensities of the 254 nm resonance line of Hg were measured for cold spot temperatures between 16 deg. C and 50 deg. C. The observed normalized intensities agree with line-of-sight intensities predicted by our improved 1D Boltzmann/non-local radiation transport model for fluorescent lamps. An additional comparison with model predictions employing the conventional Holstein theory showed that the latter is inadequate for describing the radiation transport of resonance lines in fluorescent lamps
[en] A highly efficient mercury-free flat fluorescent lamp (MFFL) with dielectric barrier Xe gas discharge was developed for a LCD-TV backlight source. The unit cell of the lamp has a simple structure with two main electrodes running parallel to each other and an auxiliary electrode. The adoption of the auxiliary electrode resulted in a wide, stable operating voltage margin, high luminance and efficiency. The 4 inch diagonal size lamp showed a luminous efficacy of 44 lm W-1 at a luminance of 3400 cd m-2 with Ne-Xe(18%) gas mixture. We demonstrated that the 4 inch unit cell can be used to construct a 5 x 8 multi-structured lamp of 32 inch diagonal size for application in a large-sized LCD backlight source by a simple repeat of the unit cell. Despite the increase in size, the 32 inch lamp showed the same discharge voltage and margin of the 4 inch unit cell. Using the proposed MFFL with the auxiliary electrode as the data electrode and the subfield method, we developed a driving scheme for 2-bit areal selective dimming control of an M x N multi-cell lamp which can be operated using only one inverter.
[en] Cathode fall is a key parameter in assessing the performance of a fluorescent lamp since it is a fundamental part of a lamp's operation and, at the same time, may be responsible indirectly for many undesirable effects, such as shortened life and severe end-darkening. This work addresses the familiar band diagnostic (BD), a technique often used to measure cathode fall. The diagnostic is an easily implemented, non-invasive procedure in which a metal foil is placed around the outer glass wall of a lamp in the electrode region, and the potential difference between the foil and electrode is measured. Unfortunately, there are severe limitations in interpreting the measurement. The goal of this work has been to properly conceptualize this diagnostic to improve understanding, to identify factors limiting interpretation and to identify features from experimental measurements. The result is a lumped parameter model, and a key component is a representation of the wall sheath at the plasma/wall boundary. Conceptually, the BD is identical to the internal floating probe, and therefore the model is applicable to that diagnostic as well. In addition to descriptions of the model and model calculations, comparisons are made between band and probe and between band and experimental measurements