The Cathode Ray Tube site

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The Finebeam tube (fadenstrahlrohre) is used with Helmholtz coils to study electron beam deflection and determine the electron charge to mass ratio (e/m).
The German NEVA factory, manufacturer of the Finebeam tube, closed in 1969.
Philips DG7-32 exploded view box was designed for educational purposes.
The Braun tube, developed after Thomson, used electrostatic deflection plates and became a precursor to CRTs in oscilloscopes.
Early Braun tubes had a phosphor mica screen; later versions used phosphor-coated glass fronts like modern CRTs.
P.J. Kipp & Zonen, founded in 1830, sold Braun tubes and evolved into a company that still exists in the Netherlands.
The Wehnelt CRT (ca. 1930) introduced a direct heated filament cathode and Wehnelt cylinder for electron beam focusing.
Arthur Wehnelt discovered in 1904 that alkaline earth coatings on cathodes improve electron emission efficiency.
Post-war Braun tubes (e.g., BR2) were produced by NARVA VEB in East Germany (DDR).

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