The Cathode Ray Tube site
History and Physics Instruments
Rotating anode X-ray tubes
A Siemens and a Nago mid 20th century.
Burn marks on the tungsten target.
Burning tube, only heater!
Siemens Kenotron HV X-ray rectifying tube.
125 KV 1400mA used for X-ray power supply.
Click on the tube to see the burning filament.
Siemens Reiniger-werke V150/1502p
A huge 55cm X-ray Kenotron for Greinacher/Villard circuit.
Used in the first half of the 20th century.
Kenotrons were rectifier tubes (valves) for the
very high tensions needed for the X-ray tubes.
In German known as ventilröhre.
Philips Kenotron type 28136
William David Coolidge 1873-1975
Triple cascade X-ray tube in the lab of Dr. Coolidge 1928
In this lab model every bulb is fed with 300KV, the tube was 2,4 meter long with bulb diameters of 30cm!
Lodge X-ray High Tension Valve ca 1912
This rare rectifier tube invented by the physicist Sir Oliver Lodge prevented reverse currents which occurred using Ruhmkorff coils. The unversed voltage had a negative effect on the pressure in the Ion tubes. These rectifier valves prevented these unversed voltages. The valves were used in series with the X-ray tube.
The Cathode inside the tube is an aluminum spiral which creates a larger surface for handling high currents. The distinctive red colored glass is the result of a specific exhaustion method which keeps the vacuum stable under all conditions.
Pictures courtesy of Alastair Wright.
From Ion X-ray tubes to Hot Filament tubes
In the early times Crookes or Hittorf tubes consist of a few simple electrodes projecting into a
glass bulb. With one of these tubes Wilhelm Röntgen made his discovery for which he was
awarded for the first Nobel Prize. The classic cold cathode ion X-ray tube was born. A tube with two
electrodes. The tube developed qiuck into a three electrode tube with an anticathode and platinum
target (due to the high melting point of this metal).
Soon after the discovery of Conrad Röntgen the production of these tubes started, not only in the
German factories of Gundelach, Müller, Pressler and Siemens. But also Andrews in England.
In the US by Victor and General Electric. But these ion tubes had many disadvantages like unstable
vacuum and cooling. Some described them as unpredictable as a woman.
The great breakthrough came in 1913 when William Coolidge and Lilienfeld made there first hot filament
cathode X-ray tube, he replaced the cold cathode with a heated spiral filament cathode and tungsten
anode. The third anticathode disappeared, the angle of the anode in his tube was set at 45º. X-rays
could now be better controlled and were more reliable. The only practical problem was cooling the
Anode, (which got extremely hot) this was a huge problem due to its small size. New designs were
developed, a heavy copper base to the anode, sometimes with water or air cooling, this conducted the
heat away and therefore increased the capacity of the tube to withstand a high current.
Philips developed in 1924 the Metalix tube. The glass tube was fitted in a metal housing and also
incorporated the principle of line focus. This tube had sufficient shielding for physician and patient and
was safe to use with the high voltage.
The anode face was changed to an angle of 19º in respect to the cathode.
X-ray demonstration tube for Gaede pump use.
Leybolds Nachfolger 1910-1930
This tube has blue glass terminals.
Picture from the Leybolds Nachfolger catalogue 1911.
Leybold sold many types of tubes for the use on a
Gaede vacuum pump.
This picture comes from the Leybolds Nachfolger catalogue from 1929.
In this catalogue the tube is only printed in combination with the Gaede pump and not available anymore as a separate item. The reference number points at a new type. This dates this tube before 1929.
Another X-ray demonstration tube
for use on a Gaede pump.
ca 1910-1930 Height 30cm
Two early demonstration Pressler X-ray tubes.
The larger tube made by Pressler has a length of about 25 centimeter and was used in schools mid 20th century. It has a regulator, a small glass compartment on the tube with a piece of charcoal which could be heated to correct the internal gas vacuum. The small tube measures about 15 centimeter with 5 cm bulb and was probably part of a Physics experiment kit around 1900.
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Didactical and Toy X-ray Tubes
Rectifier Valves - Kenotrons
Hot filament Coolidge X-Ray Tubes
The first rotating disk X-ray tube (Rotalix) was developed by Philips in 1929. With this concept the
loadablity problem due to a high energetic focus spot was solved. The heat generated to produce better
quality pictures was spread over a larger area. The disk was made out of sintered tungsten.
Rotating disk X-Ray Tubes
A small X-ray tube ca1896-1900
most likely made by Gundelach.It has a serial number 5658,bulb diameter 7cm
With a bulb diameter of only 4,5cm dates from early 1900. It was probably part of an experiment box sold by Bing or Meiser&Mertig
Advert from the Bing 1912 toy catalogue.
Around 1900 many educational different Physics boxes were sold for amusement or Christmas gift. Many kids were experimenting with the newly discovered techniques like electricity and even X-rays without warning!
Home entertainment X-ray tubes.
These rather small X-ray tubes were
used in school and for home
entertainment sold as part of Physics
experiment boxes together with small
Ruhmkorff coils or Wimshurst
static machines. The drawings from the
original catalogues show how
the tubes were used.
Page from the 1909 German
von Dr. C. Richard Schultze.
Huge water cooled C.H.F. Müller Rapid X-ray tube (1926).
This tube is a result of many years of development, the first Müller Rapid tubes date back to 1911 and were patented. The copper block connection of the anti-cathode to the glass is special in this tube. The anode is hollow for optimum cooling of the electrode with water.
The target is made of Tungsten (Wolfram)
The Bauer air valve regulator.
This regulator was used to regulate the vacuum to the optimum pressure. Inside is a folded thin glass tube containing a bit of mercury. Attached to the rubber hose was a pneumatic piston to move the amount of mercury allowing a bit of air slipping into the tube softening the hardness of the X-ray tube.
Small Gundelach Ion tube for school demonstrations ca1920
The iconic Gundelach Moment tube
lenght 40cm This model is made around 1910-1912.
On the sphere there is a J etched, this was used by Gundelach for marking tubes made for rectified alternating voltages, probably for use with the "Ideal Apparat" made by Reiniger Gebbert & Schall.
The Gundelach vacuum regulator for regulating the " hardness" of the tube.
Smallest kids working X- ray setup ever seen!
Working tube on the smallest
German coil I know.
Due to it's age the tube is gassy
and no harmfull x-rays are produced.
A small 15cm fluoroscope screen made by the German company Heyden ca1910, an Ampere meter made by the French maker C.G de Radiologie and an English indicator tube ca 1910.
The indicator tube was placed in series with the X-Ray tube to see if there was a reverse current present.
The working indicator tube shows the typical reversed current of a Ruhmkorff coil, Ionisation around both wires, there is a bit more forward current than reversed. Due to this phenomena most early X-ray tubes degraded and eventually were not useful anymore.
Placing a valve tube in series with the X-ray tube prevented this negative effect. With a true DC current only one wire will ionize.
A viewing device with a fluorescent screen in the front.
X-ray tube ca 1910 maker unknown but likely from the French Giaffe & Pilon company.
A complete toy X-ray setup from early 1900
In front a German DIY X-ray booklet for kids.