THE FUSOR REACTOR: Philo Farnsworth

The multipactor tubes use opposed concave electrodes. In effect, they are concave electrostatic mirrors. These mirrors focus the ionized gases into tight little points, just as mirrors concentrate light. The concave mirrors permitted the re-discovery of electron optics; a phenomenon originally witnessed by Sir William Crookes in 1890 and “overlooked”.

Dr. Farnsworth designed a great number of different multipactor tubes. His patent collection is enormous. Dr. Farnsworth noted very anomalous phenomena in several of his multipactor tubes. These included sharp energy surges on the output stages, which seemingly appeared “from nowhere”. The possibility is strong that he discovered an entirely new kind of energy source, having nothing to do with hot fusion. It has been suggested that these surges were of cosmic origin.

While testing his high power UHF multipactor tubes in 1935, Farnsworth discovered a strange phenomenon, which caught his curiosity. Suspended in the tube center, he sighted a tiny brilliant blue starlike point. The little starlike point of light became more brilliant with increasing application of voltage. The little starlike points never touched the walls of the container, remaining fixed in the space where first sighted. Farnsworth recognized this feature as a control characteristic, which might somehow be employed in the future.

Farnsworth multipactor tubes can be small enough to be hand-held. The larger models are the size and volume of a thermos bottle. Used as UHF oscillators, they produce enormous outputs of power.

The optically focused little stars are instantly formed within the multipactor tube, exhibiting all the control-response characteristics later sought desperately by hot fusion reactor designers.

Farnsworth realized that hot ionized gases could be bound into these small starlike points, their rare stability managing any applied power load. The little stars could absorb and hold tremendous amounts of applied energy, an aspect that deeply impressed Dr. Farnsworth. His original notion was to utilize the principle in high power UHF transmitter tubes. For metallurgical purposes Farnsworth thought the process would have industrial applications. The star points could be directed into any material surface. Melting tiny holes in metals would be no problem for the intense freely floating little ionic star. Soon his mind turned toward nuclear energy. The starlike “plasmoids” could be loaded with any amount of electrical power and be maintained away from the container walls. They were stable, could absorb fresh gas and electrical power with theoretically no limit to the attainable temperatures. The notion of using the principle to construct a nuclear furnace deeply intrigued him.


Thermonuclear energy was used in the hydrogen bomb technology. The scientific community was astir with talk of hydrogen energy. Farnsworth also studied the problem of controlled thermonuclear energy. The gaseous temperatures had to be immensely high, and safely contained. By as early as 1953 he had conceived of a means for using the star like phenomenon to produce controlled nuclear hot fusion reactions. He published his theoretical research on usable hot fusion energy.

In 1959 H.S. Geneen (Raytheon) invited Dr. Farnsworth to address the ITT board of directors on controlled nuclear hot fusion. It was against the verbalized misgivings of the AEC that this lecture was presented. Farnsworth was then formally approached by ITT after announcing his plans to investigate hot fusion reactions. Farnsworth designed a new and dramatically original tube, which he named “The Fusor”. In this new tube, the starlike plasmoids of deuterium were isolated, shaped, confined, treated, balanced, and moved absolutely without the need for magnetic confinement. He conducted the first tests in his own home laboratory space, the deuterium tanks and electrical cables running throughout the living room to the cellar. Shortly thereafter, preliminary tests on the first Farnsworth “Fusor” was performed in a small ITT basement laboratory. His first design for a hot fusion reactor system was realized late in 1958. ITT monitored all the research and brought its own supervisors into Farnsworth’s team.

The “Fusor” is a device, which produces controllable hot fusion reactions and does not utilize magnetic confinement. The design is a radical departure from all the designs of its time, a simple optical electronic system. The Fusor is no larger than a softball. In its center is the electron-radiating cathode. This cathode is surrounded by a spherical anode. A group of deuterium guns are symmetrically mounted about the anode ball. Their beam axes face each other and intersect at the tube center, firing ionized fuel into the reactive focus. It is perhaps the most advanced electron power tube ever designed.

Deuterium gas particles are propelled and focused into the center of the tube, establishing the star-like plasma at the focus. Magnets are never needed to contain the gas. Nuclei, which are trapped in the starpoint, can never escape the focus. They are maintained in place by their own inertia and the incoming barrage. Deuterium nuclei are literally hammered into the required density in the central region by the process of “inertial containment”, a term, which Farnsworth first coined. Potentially escaping nuclei are stopped by layers of surrounding charge until they are forced back into their center point. Ionic shells are held in the vise-like grip of applied power. Confinement power can be poured into this center almost indefinitely because the trapped nuclei cannot escape the field energy. Nuclei, which “fall” into the centermost virtual electrode, have fusion energies, and are contained at a density sufficient to produce controlled fusion reactions. With sufficiently high power applications, the hot fusion reaction can be sustained and controlled at will in the Fusor. Dr. Farnsworth worked out an elegant means for extracting the energies of fusion, energies that remain electronic in their nature. Developed fusion energy produces an electronic pressure blast against the applied energy field. This experimentally appeared as a dramatic back-surge in power. This electrical blast may be directly harnessed and used in external loads.

Even as stars govern their own output by expanding and reducing plasma density, the little stars were found to be remarkably resilient and resistive to instabilities. In fact, the only instabilities seen in the Fusor were those, which came from the outside. Tube external power instabilities required new safety systems to be developed. Maintaining the constancy of application required “pure” electrical inputs.