Gas Discharge Tubes

This section includes Geissler tubes and their immediate descendants, including spectrum tubes, flash tubes and laser tubes. Some tubes of this type, such as laser tubes and hollow cathode light sources, have legitimate industrial or scientific uses, but the majority of gas discharge tubes are marketed as purely decorative devices. Gas discharge tubes also saw use as demonstration or teaching tools for high school and college physics classes, allowing for the direct viewing of various electrical and physical effects in a classroom setting.

 


Crookes Cathode Ray Tube (Unknown Mfr.)
 

"Crookes Tube" is the generic descriptor given to a wide range of hard vacuum demonstration devices, each with a different educational function. This particular tube, also known as a "beam deflection tube" was designed to illustrate how a cathode ray beam could be deflected by a magnet. A thin beam of cathode rays is projected through the slit at one end of the tube and strikes a slanted metal plate, which has been covered with a phosphor to produce a visible line discharge. When a magnet is brought near the tube, the effect of the magnetic field can be seen in the deflection of the cathode ray beam.

Though traditionally cathode ray tubes of this type were pumped down to a vacuum state, the example shown here is a newer gas filled version, most likely made during the 1950s. To make it easier to strike the tube with lower voltage supplies, this example has been filled with hydrogen, which is what produces the blue discharge at either end of the tube.

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Crookes Cathode Ray Tube (Unknown Mfr.)
Uniphase Laser Tube (Unknown P/N)
 

An example of a late era Uniphase helium-neon laser tube. This type of tube was almost exclusively used as a laser projector for early barcode scanners. Power level is unknown, but red helium-neon tubes of this size typically output between 1mw and 2mw.

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Uniphase Laser Tube (Unknown P/N)
Electro Technic Products De La Rive Apparatus
 

A De La Rive apparatus is a specialized gas discharge device designed to demonstrate that the glow discharge in a low pressure environment can be influenced by electromagnetic fields. The De La Rive apparatus consists of two parts, a low vacuum electron tube with a tubular depression passing through it's radius, and an electromagnet that mates to the tube such that the electromagnet's core passes through the center of the tube. When the tube is activated and a voltage is passed across the electromagnet, the discharge beam will rotate around the ring-shaped anode in the same direction as the magnetic field, demonstrating that the glow discharge is made up of charged particles that can be influenced by an external electromagnetic force.

This example, manufactured by Electro Technic Products, was probably produced sometime in the mid 20th century as an educational demonstration for high school and college physics classes. Interestingly, the control coil for this example is made out of the re-purposed shell of an Electro Technic BD10 violet ray generator, a device commonly used as a 'sexual aid' amongst a certain subset of the human population.

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Electro Technic Products De La Rive Apparatus
Crookes Mineral Tube with Calcite
 

This rather obscure Crookes tube is designed to demonstrate the phosphorescent properties of various minerals, in this case calcite, when exposed to an electron beam. The center of the tube contains a cubical sample of calcite caged within the embrace of a bent glass rod. A large plate electrode at the top of the tube generates a cone of electrons that excite the calcite and cause it to glow red. The glow of the calcite is persistent; the sample will continue to emit light for several minutes after power has been removed from the tube. Originally this tube would have been mounted to a turned wooden stand by means of the long glass extension exiting below the calcite sample; a century of human friction stripped this example from it's stand long ago. Based on the tube's cap construction and the way in which the calcite sample is mounted, it is likely this particular tube was made late in the 19th century.

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Crookes Mineral Tube with Calcite
Geissler Tube with Spirals
 

The Geissler tube is an electrical demonstration device that was invented in 1857 by Heinrich Geissler. Starting in the 1880s, Geissler tubes were mass-produced as functionally useless decorative devices, designed to provide entertainment to wealthy Victorians, and such tubes could arguably considered to be the world's first electronic entertainment product. Technically, a Geissler tube is simply an evacuated glass tube with two electrodes, which has been filled with a noble gas or other substance to produce a demonstrational glow discharge. In practice however, Geissler tubes are usually highly decorated, formed into complex shapes and encrusted with whorls of uranium glass and liquid filled cavities.

This example is a fairly representative of the typical form of a Geissler tube; it is constructed of two glass spirals connected to glass bubbles at each end which contain the electrodes. The center 'grape' bubble of the tube is made out of uranium glass, and fluoresces green when the tube is under high tension.

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Geissler Tube with Spirals
Welch Scientific Geissler 'Aurora' Tube
 

This is a post WW2 Geissler tube that was manufactured specifically for the educational market. Though most Geissler tubes are typically highly decorated, this particular example is somewhat unusual due to its completely unshaped and undecorated envelope, which was designed to allow students to observe the flow of the gas discharge under different external magnetic and electrical fields. This can be seen in the photo to the right, the 'dark space' at each electrode is clearly visible, as are the standing waves produced by the high frequency power supply used for the photo. Though this tube was sold by Welch Scientific, we are almost certain it was actually manufactured by Electro-Technic Products sometime between 1960 and 1980 based on it's shape and electrode construction.

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Welch Scientific Geissler 'Aurora' Tube
Pressler 'Globe' Spectrum Tubes
 

Devices included in this entry:

Argon spectrum tube (glass capillary vessel)
Krypton spectrum tube (glass capillary vessel, pictured in thumbnail)


Another example of a set of spectrum tubes with unusually shaped envelopes. These tubes have right angle electrodes like the "H" shaped tube below, but add the extra attachment of a globe shaped discharge chamber at one end of the capillary vessel. This construction style allows the tube to serve double duty as both a capillary emitter and a point spectral source.

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Pressler 'Globe' Spectrum Tubes
Melles Griot HeNe Laser Tube (Unknown P/N)
 

This is an example of an older low power 'hard seal' helium neon laser tube. Unlike early 'soft seal' helium-neon lasers, this tube has its mirrors permanently fused to the glass envelope, which prevents the helium from escaping over time. A hard seal tube can be expected to hold its gas for several decades, as opposed to the one- to three-year lifespan of the average soft seal tube. The exact power output of this unit is unknown, but is probably at or below 1mW.

Melles Griot HeNe Laser Tube (Unknown P/N)
Deuteurium Arc Lamp (Unknown Mfr.)
 

This unusual device is a deteurium arc lamp, a type of laboratory UV light source. This lamp is approximately the size of a standard octal tube, but has only three leads which are covered in thick insulation. There are two rectangular chambers in the center of the lamp, with small slits in the front. There appears to be a large heater coil in the outer chamber, which is open on both ends. The lamp has an argon-like ionization glow.

Special thanks to Giorgio Basile for identifying this device.

Deuteurium Arc Lamp (Unknown Mfr.)

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