Machlett Dynamax “25” X-Ray Tube

by Charles Adeyinka

Machlett Dynamax “25” X-Ray Tube

Object: Machlett Dynamax “25” X-Ray Tube

The Machlett Dynamax “25” X-Ray Tube was developed around 1939, representing both the end of the great depression and the start of WWII. Perhaps this positive improvement in x-ray technology was just one representation of how the Great Depression was coming to an end.  This object represented great advancement in x-ray development, as the rotating anode within this tube made higher energy x-rays possible, leading to higher penetration of materials. The dual focus aspect of this tube enabled images of both fine detail and wider (less detailed) scope to be produced. This early model of the rotating anode tube was developed by Raymond R. Machlett, a recognized pioneer of X-ray technology.Dynamax Tube - cork end

Though this particular x-ray tube was utilized academically  in the physical sciences, it was noted that this product had also been used for radiomedical purposes. In general, x-rays allow doctors to see problems within in the human body without being intrusive. Thus it’s easy to see how the dual focus and rotating anode of this x-ray tube would be beneficial for both research and clinical purposes.

Collection: University of Toronto’s Scientific Instruments Collection

Maker: Raymond R Machlett of Machlett Laboratories (originally E. Machlett & Son)

Dimensions: Height = , Width = , Depth =

Materials: Copper, tungsten, ceramic, cork, and glass


Dynamax Tube labelThe x-ray was discovered in 1895 by Wilhelm Conrad Rontgen. Rontgen performed an experiment in which an electric voltage was passed through a special gas in a tube, and witnessed that it this action produced a fluorescent light. He then wrapped black paper around the entire tube and saw that the fluorescence could be seen through the black paper. He had discovered an unknown, invisible light (x-ray). [8]

The X-ray tube is the integral component of the x-ray machine. Within the tube there are electrons that begin within the heated filament (cathode) and are forced toward the anode made of tungsten.[7] These electrons are essential in photon production. The electrons begin at high speed in a high orbital and eventually come into contact with metal at the anode within the x-ray tube. This contact causes the electrons to immediately fall into a lower energy level. This electron movement causes there to be a large amount of energy released some of which is the photon.  [6] The photons that are produced represent the light energy of the x-ray.

This specific X-ray tube for its time of introduction produced images of higher quality and worked much quicker than its previous counterpart. It allowed for use at higher energies and imaging for longer periods of time in sections of the body. Regarding improvements of the X-ray tube, overall the machine improved imaging of various organs such as the lungs, heart, intestines, and gall bladder. It gave higher quality images while using less voltage and it shortened the time for Bucky diaphragm imaging to just 1/60 second.[4] As well in recent models there has been an increase of power by 60 kW, 328 000 heat units (thermal storage capacities), an in increase of the rotational speed by 7000 rpm, and the maximum voltage had gone up by 60 kVp.[5]

This version of the x-ray tube created an entire study towards x-rays and was the basis for many improvements of the technologies such as the ct scan and pet scan. These improvements helped many medical facilities such as the Hospital for Sick Children and Sunnybrook Hospital.

 Dynamax Tube - detail of interior

Form and Fabrication:

The Machlett Dynamax “25” X-Ray Tube possesses a copper anode, pure nickel cathode tungsten target disk, and ceramic and cork materials for insulation. As well it is a made of a glass covering that encases a cathode and anode.

The object is in good condition with slight darkening of the glass casing from radiation. There is a label on the glass that indicates product maker and product name/function (see object label image for further details).

Production:Dynamax Tube - detail of end

This is difficult to answer. We know who produced it and the materials, but exact specifications regarding production are not specified.


The Machlett Dynamax “25” X-Ray Tube was used by the University of Toronto Physics department for both experimental and educational purposes. This object was transferred to the University of Toronto’s Scientific Instruments Collection in 2011.

Sources and further readings:




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