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Vacuum tube and plasma displays
Published in John P. Dakin, Robert G. W. Brown, Handbook of Optoelectronics, 2017
Makoto Maeda, Tsutae Shinoda, Heiju Uchiike
An electron beam put out from the gun travels straight toward the center of the CRT. To let it reach all over the screen, we usually use two methods—electrostatic deflection and electromagnetic deflection. The former method requires two flat-plate electrodes facing each other. The beam travels between the two. When electrical potential between them varies, the beam changes the direction. In spite of its lower deflection efficiency, the method is quite effective in deflecting high frequency. Meanwhile, the latter method of electromagnetic deflection characterized by its higher deflection efficiency is used for television and many other CRTs, and the deflection yoke performs electromagnetic deflection, using two pair of coils. As a pair of coils facing each other generates one magnetic field, the two pairs create two magnetic fields, directing the beam both horizontally and vertically. See the structure in Figure 5.3 for magnetic deflection yoke.
The Changing Face of Public Broadcasting in India
Published in IETE Journal of Education, 2023
The cathode ray tube (CRT) was the sole display device for the TV, and the use of magnetic deflection facilitated wide deflection angles. This resulted in a display tube of short neck, and thus a TV receiver having more acceptable depth. The magnetic deflection coils were wound on a ferrite core to provide a concentrated magnetic field, which forced the electron beam to move in the x, y direction on the CRT face under the control of scanning circuits. The CRT display dictated a scanning frequency of about 16 KHz on account of constraints of bandwidth, and choice of magnetic material for the deflection yoke, all taken together. Philips Holland did pioneering work on these issues related to Systems B and G. The scanning circuits were kept in sync with transmitted signals to ensure a stable picture on the CRT face. The phosphor on the inside of the CRT emitted white light under electron bombardment. The color display tube has three guns for three primary colors and each beam was made to fall on a phosphor dot of a particular color. The color tube was developed by RCA of the USA and improved substantially by SONY of Japan.
Investigations on physical properties of Mg ferrite nanoparticles for microwave applications
Published in Journal of Microwave Power and Electromagnetic Energy, 2019
Siva Kumar Pendyala, K. Thyagarajan, A. Gurusampath Kumar, L. Obulapathi
Nano-structured Mg-ferrites at various calcination temperatures have been successfully prepared by the sol-gel auto-combustion method. Mg-ferrite samples exhibit the cubic spinel structure with no impurity phase and average crystallite size was calculated from XRD is in the order of 20 nm and is increased with the calcination temperature upto 600 °C which was also supported by SEM studies. The SEM analysis confirmed the nature of material and surface having clear grains with well-defined grain segregation. The average grain size is increased with the calcination temperature. The FTIR spectra showed the clear O–H and C–O–H groups in the stretched and vibrational modes respectively. The maximum dielectric constant of 46 at 1 kHz frequency at 600 °C calcination temperature was observed. The dielectric constant, dielectric loss exhibits decreasing nature with increase of frequency, which is useful for applications in the range of high frequency especially in deflection yoke rings, microwave devices.