A high luminance high-resolution cathode-ray tube for special purposes

For those applications where light sources of high radiance or displays of high resolution are necessary, miniature cathode-ray tubes have been developed with monocrystalline luminescent screens. These newly developed screens consist of cerium-doped yttrium-aluminum garnet (YAG), epitaxially grown on commercially available YAG substrates; they have an excellent heat conductivity and are optically clear. The construction of the tube and its performance in two modes of operation are described. When the tube is operated with a continuous undeflected beam, the luminance of the spot is limited by thermal quenching of the phosphor material. Under these circumstances, the maximum luminance of 1.9 × 10
⁸
cd/m
²
(0.55 × 10
⁸
FTL or 4 × 10
⁵
W/m
²
sr) is reached at a power of 70 mW in a 3.5-µA 20-kV beam, focussed to a spot of 9 µm diameter. Equipped with appropriate deflection coils and scanned with an interlaced field of 575 active lines and 25-Hz repetition frequency, the tube can handle up to 20 W of beam power in a 12 × 16 mm
²
image area. In this mode, the luminance is limited by the design of the electron gun and the desired resolution. At 20 kV and 100 µA (i.e., at 7500 cd/m
²
) the tube has a half-intensity linewidth of 60 µm, which is equivalent to 500-TV limiting response lines in the same 12 × 16 mm
²
area.