The light output of some phosphors excited with electrons of high current density

Einstein, P.A.

doi:10.1088/0508-3443/8/5/302

Cited by 16 publications

(11 citation statements)

References 8 publications

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“…The linearity of the increase in the intensity of the luminescence is, however, generally limited to low current densities with phosphors used in most color-TV display systems (1)(2)(3)(4)(5). At high current densities, the increase is less than linear.…”

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confidence: 99%

“…The intensity of the luminescence emitted by a phosphor screen excited by cathode rays increases as the number of electrons per unit area incident upon the phosphor is increased. The linearity of the increase in the intensity of the luminescence is, however, generally limited to low current densities with phosphors used in most color-TV display systems (1)(2)(3)(4)(5). At high current densities, the increase is less than linear.…”

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confidence: 99%

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Phosphor Screens for High-Current-Density Cathode-Ray Tubes

Meyer¹,

Palillo²

1969

J. Electrochem. Soc.

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Phosphors are evaluated for use in high-current-density cathode-ray tubes. Oxide-based phosphors exhibit a linear increase in brightness with current density, whereas conventional II-VI sulfide phosphors show a less-than-linear increase. At high current densities, the sulfides also exhibit spectral shifts and a decrease in decay times. Selected rare-earth-activated oxide phosphors incorporated in a postdeflection focusing tube demonstrated a substantially linear increase in brightness, improved contrast ratio, and good color balance.The intensity of the luminescence emitted by a phosphor screen excited by cathode rays increases as the number of electrons per unit area incident upon the phosphor is increased. The linearity of the increase in the intensity of the luminescence is, however, generally limited to low current densities with phosphors used in most color-TV display systems (1-5). At high current densities, the increase is less than linear. This nonlinear behavior is called the "saturation" effect. The most common type of color-TV tube in use today is the shadow-mask version in which a perforated electrode is interposed between the electron guns and the phosphor screen in a unipotential drift space. This electrode severely limits the number of electrons reaching the screen since 85% of the electrons emitted by the guns are not transmitted by the mask (6). Other types of color picture tubes are available which considerably increase the current density at the phosphor screen by providing for finer focusing of the electron beam. One such class of tubes, the post-deflection focusing (PDF) type, produces a focusing action at the screen by replacing the unipotential drift space by a retarding field region created by a grill in close proximity to the screen. The "Chromatron" or "Lawrence" tube (7) are examples of this tube type in which either one or three electron guns are used and in which the current densities on the phosphor screens are several orders of magnitude higher than the current densities in the shadow-mask tube. Recently, another type of tube has been announced (8) which utilizes current densities between those encountered in the shadow-mask and the PDF tubes. In this tube, electron guns with improved focus are used, and a grill system having a higher optical transmittance than that of the shadow mask is placed between the phosphor screen and the electron guns. Conceivably, the development of guns having improved focus could also be utilized in shadow-mask tubes to obtain higher current densities.The brightness advantage which would be expected from the PDF grill has, however, not been realized in practice. The PDF grill has an electron transmission about six times that of the aperture mask and, in addition, provides a focusing action which delivers a higher current density at the screen. However, the phosphor characteristics preclude full utilization of the higher current density because of the nonlinear response of the phosphors at higher current densities and the decrease in contrast ratio 1 caus...

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Phosphor Screens for High-Current-Density Cathode-Ray Tubes

Meyer¹,

Palillo²

1969

J. Electrochem. Soc.

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“…When excited by an e-beam at a current density characteristic of CRT use (~10 jiA/cm 2 ), this phosphor can convert over 2C% of the incident ebeam energy into light. 52 However, as the excita tion current density exceeds 20 mA/'cm 2 , the out put light -itensity begins to roll off, 53 as shown in Fig. 20.…”

Section: E-piam-pumped Epitaxial Phosphorsmentioning

confidence: 98%

Potential of high-average-power solid state lasers

Emmett¹,

Krupke²,

Sooy³

1984

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We discuss the possibility of extending solid state laser technology to high average power and of improving the efficiency of such lasers sufficiently to make them reasonable candidates for a number of demanding applications. A variety of new design concepts, materials, and techniques have emerged over the past decade that, collectively, suggest that the traditional technical limitations on power (a few hundred watts or less) and efficiency (less than V%) can be removed. The core idea is configuring the laser medium in relatively thin, large-area plates, rather than using the traditional low-aspect-ratio rods or blocks. This presents a large surface area for cooling, and assures that deposited heat is relatively close to a cooled surface. It also minimizes the laser volume distorted by edge effects. The feasibility of such configurations is supported by recent developments in materials, fabrication processes, and optica! pumps. Two tvpes of lasers can, in principle, utilize this sheet-like gain configuration in such a way that phase and gain profiles are oniformh sampled and ID first order, vield high-quaiitv (undistorted) beams. The zigzag laser does this wi'h a single plate, and should be capable of power levels up to several kilowatts The disk laser is designed around a large number of plates, and should be capable m scaling to arbitrarily high powr levels.

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“…2~AT I = --~ hi r, [5] a t Therefore, the proportionality constant between light spot intensity and current density for Y2SiOs:Tb, a, is given by…”

Section: [4]mentioning

confidence: 99%

“…Measurement of the saturation of various phosphors has been reported by a number of authors (1)(2)(3)(4)(5)(6), with the work of Meyer and Palilla (6) being most directly concerned with television tube application. In these previous works, some assumption was made about the current density profile across the electron beam and a calculated average current density was used in the saturation plots.…”

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A Technique for Measuring the Saturation of Phosphors at High Current Densities

Gibbons

DeLosh

Tien

et al. 1973

J. Electrochem. Soc.

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A technique is described which allows for the measurement of the saturation of luminous intensity of phosphors up to high current densities. The actual light intensity profile of the spot is measured and is related to the current density profile across the spot, the latter being obtained from measurements on a nonsaturating phosphor. This technique thus uses a point-bypoint measurement of relative efficiency vs. beam current density, and therefore no assumptions concerning the beam current profile have to be made, and no averaging of beam current over spot diameter is required. Typical data are presented from several classes of materials. For the samples reported, La202S:Tb showed the least degree of saturation, (Zn, Cd)S:Ag the greatest degree, and Zn2SiO4:Mn was intermediate to these two.Most phosphors, when excited by an electron beam, show a less than linear increase in brightness with increasing beam current density. This phenomenon is known as saturation and is indicated schematically in Fig. 1 where both intensity and efficiency are displayed as a function of beam current density. This effect can be particularly troublesome in multicolored cathode ray tubes using high current densities, e.g., post deflection focusing (PDF) type color television tubes. * Electrochemical Society Active Member. ]Key words: luminescence, phosphors, saturation. CURRENT DENSITYFig. 1. Effect of current density on: a) brightness or b) efficiency of a nonlinear phosphor.Two disadvantages will accrue if the phosphors chosen for this type of tube exhibit saturation in the current density range used by the tube: (i) the anticipated brightness increase will not be achieved, and (ii) the color balance and white field produced by color mixings will vary with beam current density. For these reasons, the intensity vs. beam current density data is an important factor in choosing the appropriate phosphors for these types of applications.Measurement of the saturation of various phosphors has been reported by a number of authors (1-6), with the work of Meyer and Palilla (6) being most directly concerned with television tube application. In these previous works, some assumption was made about the current density profile across the electron beam and a calculated average current density was used in the saturation plots. The technique reported in this article determines the actual current density profile of the spot, and so provides a point by point measurement of intensity vs. beam current density. ApparatusPhosphors used in this experiment were either obtained commercially (so designated in the appropriate figures) or prepared in the laboratory. Samples were settled onto 2.5 • 7.5 cm microscope slides using a potassium silicate-barium acetate settling method. After lacquering, the slides were aluminized in a vacuum evaporator. Aluminum deposition was regulated by a quartz crystal thickness monitor such that all samples measured had an aluminum backing of 1000 _ 50A. Saturation measurements were made in a demountable electron beam gun system sho...

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The light output of some phosphors excited with electrons of high current density

Cited by 16 publications

References 8 publications

Phosphor Screens for High-Current-Density Cathode-Ray Tubes

Phosphor Screens for High-Current-Density Cathode-Ray Tubes

Potential of high-average-power solid state lasers

A Technique for Measuring the Saturation of Phosphors at High Current Densities

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