The Cathode Ray Tube site
History and Physics Instruments
Canal Rays or positive
Protons (red glow)
1850 - 1931
The Goldstein Canal Ray tube.
This tube demonstrates that besides the cathode rays there is another
stream that travels in the opposite direction as the electron flow.
Discovered in 1886 by Eugen Goldstein (1850- 1931) who named this
"canal rays". In fact these are positively charged protons, producing a
reddish light in the upper part of the tube while in the lower part the usual
green emission of electrons can be seen when they hit the glass wall.
The electrons in the lower part of the tube can be deflected by
a magnetic field but the canal rays almost not. Goldstein could not explain
this phenomenon, it took 12 years before Goldstein's paper was published.
An interesting PDF about the discovery of the proton can be found here.
The Crookes vacuum tube (Crookes nr 7a and 7b)
Demonstrates the behavior of the electron beam in different
The 7a tube has a low vacuum about 10-30 Torr like in a
De la Rive tube, the beam in here exists between the cathode to
the anode via the shortest way, regardless which of the three is
The 7b tube however has a high vacuum of 0,03 Torr, the difference
is clear to see. Radiant matter leaves the concave cathode in the
opposite way (as X-rays) unlike which of the three anodes is used.
See also the Cross vacuum scale.
Wien Canal Ray tube length 42 cm.
This is a rare very early Leybold's Nachfolger model probably end of the 19th Century with platinum wire connections.
Canal rays can be seen in the left of the picture.
The early platinum wire loop
Wien's Canal Ray tube is named after it's inventor
Wilhelm Wien. Wien did several experiments from
1897-1912, his experiments were similar to
JJ.Thomson almost the same time.
This tube has some extra electrodes compared to
the Goldstein Canal Ray tube. To connect the tube
in different way's to a galvanometer the positive or
negative charged particles can be measured by
The sieve with tiny holes.
Early four electrode high vacuum tube no7b.
This is a model made before 1900 but still works fine.
The tube has the specific blue electrode glass seals.
Original form of a Goldstein tube.
This model is a Leybold's Nachfolger product
Probably made second quarter of the 20th century
Rare early Crookes vacuum tube.
made end of 19th century
(Crookes nr 8) Crookes describes this tube
in his 1879 On Radiant Matter lecture.
"The rays of matter being driven from the
hemi -cylinder from a direction normal to
it's surface, come to a focus and then
diverge. Tracing their path in brilliant
green phosphoresce on the surface of the
Electrons in the lower part
Early 1900 Crookes 7b tube
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Front of the tube
Where cathode rays come into open air. A thin aluminum foil needs to be placed in the clamp on the front to keep the vacuum in the tube.
A rare Lenard tube
The tube made by Leybold
is painted black to see the weak purple cathode rays in the front of the tube. It has a NS19 joint to fit on a vacuum pump.
Philipp Lenard (1862-1947) was a
German Physicist and the winner of the
Nobel Prize for Physics in 1905 for his
research on cathode rays and the
discovery of many of their properties.
He became an active proponent of Nazi
ideology. Lenard did extensive research on
Cathode rays and developed this Crookes
type tube in1905 which emit cathode rays a
few centimeters into open air trough a thin
aluminum foil. These rays are harmful to
organic materials just like X-rays.
These tubes can be only used on a
vacuum pump because the front foil will
never be a perfect vacuum seal.