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Later thermionic vacuum tubes, mostly miniature style, some with top cap connections for higher voltages. A vacuum tube, electron tube, [1] [2] [3] valve (British usage), or tube (North America) [4] is a device that controls electric current flow in a high vacuum between electrodes to which an electric potential difference has been applied.
Crookes X-ray tube from around 1910 Another Crookes x-ray tube. The device attached to the neck of the tube (right) is an "osmotic softener". When the voltage applied to a Crookes tube is high enough, around 5,000 volts or greater, [16] it can accelerate the electrons to a high enough velocity to create X-rays when they hit the anode or the glass wall of the tube.
The TWT is an elongated vacuum tube with an electron gun (a heated cathode that emits electrons) at one end. A voltage applied across the cathode and anode accelerates the electrons towards the far end of the tube, and an external magnetic field around the tube focuses the electrons into a beam. At the other end of the tube the electrons strike ...
The simplest klystron tube is the two-cavity klystron. In this tube there are two microwave cavity resonators, the "catcher" and the "buncher". When used as an amplifier, the weak microwave signal to be amplified is applied to the buncher cavity through a coaxial cable or waveguide, and the amplified signal is extracted from the catcher cavity.
After the system has been evacuated and sealed under rough vacuum, the material is heated (usually by radio frequency induction heating). After evaporating, it deposits as a coating on the interior surfaces of the system. Flashed getters (typically made with barium) are commonly used in vacuum tubes. Most getters can be seen as a silvery ...
Such a tube is more correctly called a 'photoemissive cell' to distinguish it from photovoltaic or photoconductive cells. Phototubes were previously more widely used but are now replaced in many applications by solid state photodetectors. The photomultiplier tube is one of the most sensitive light detectors, and is still widely used in physics ...
In the gyrotron, a hot filament in an electron gun (1) at one end of the tube emits an annular-shaped (hollow tubular) beam of electrons (6), which is accelerated by a high-voltage DC anode (10) and then travels through a large tubular resonant cavity structure (2) in a strong axial magnetic field, usually created by a superconducting magnet ...
By 1963, a new structural system of framed tubes had appeared in skyscraper design and construction. Fazlur Rahman Khan, a structural engineer from Bangladesh (then called East Pakistan) who worked at Skidmore, Owings & Merrill, defined the framed tube structure as "a three dimensional space structure composed of three, four, or possibly more frames, braced frames, or shear walls, joined at or ...