Philo T. Farnsworth Controlled Fusion

January 27, 2008


The Farnsworth Invention


This is the name of a Broadway play about Philo T. Farnsworth inventing electronic television and having that invention stolen by RCA.

Farnsworth had another invention which was never completed due to his death. This was an instrument which he believed would control nuclear fusion and solve all of mankinds energy requirements forever.

Farnsworth Controlled Fusion


His device to the best of my knowledge to describe it consisted of a spherical anode enclosing an electrically isolated cathode of smaller diameter consisting of a polyhedral array of hollow rings. The cathode supports passed through insulators in the anode to provide the electrical connection. The atmosphere inside the sphere was reduced to very low density with state of the art vacuum pumps. Phil called this device a "Fusor". Some photos of equipment and his youngest son's description of his work can be found at http://www.philotfarnsworth.com

A high voltage (tens of thousands of volts) was established between the anode and cathode. Deuterium or Tritium gas was injected into the sphere. Whatever happened in there resulted in a brilliant glow, bright flashes and free neutrons flying about. The basic principle behind the Farnsworth fusor, inertial electrostatic confinement (IEC), was first noticed by Phil as a glowing cloud of electrons in vacuum tubes while inventing Television. If an electric field is applied to a hot gas cloud (plasma), the positively-charged ions in the plasma will be attracted toward the region with the lowest electrical potential. By arranging conductors into a sperical grid and then applying a voltage, the fusor attracts the ions into the center of the sphere. If the voltage is high enough, the electrical attraction will cause the ions to zoom through the center at high speed; the ions then collide with other ions also moving through the center thus causing nuclear fusion or nuclear breakup (stripping).

My name is LeRoy B. Wentz. Philo T. Farnsworth was married to one of my mother's sisters, Elma "Pem" Gardner. Pem and Phil and their youngest son, Kent, were living in Fort Wayne, Indiana at the time I was studying Physics at the University of Illinois in Urbana, Illinois (1959 to 1962). My wife, Julia, and I were invited to Fort Wayne to stay in their home and visit for a few days in 1960.

Philo Farnsworth was by far my most famous relative and Aunt Pem's family relished in it even though not genetically related to Phil. I was very much aware of his television saga while growing up and this may well have been a deciding factor in my choice of engineering and science as a career.

While visiting him, his efforts were mainly focussed on the development of controlled nulear fusion. At that time his experiments were being conducted in laboratories at ITT, his employer who funded much of his early fusion experiments. He described to me his experiments, the equipment and what had been observed at that time as well as his theories as to how the system worked. He was absolutely convinced that he had observed the fusion of deuterium into tritium and/or helium 3 in his equipment. I was unable to understand much of what Uncle Phil told me about his device and his theories. He spoke in different terms than I was learning in my studies of physics - I attribute this to Uncle Phil being mostly self taught and developing his own terms to describe his thinking.

The best that I can describe what Uncle Phil was doing follows:


A spherical cloud of electrons forms around the center of the sphere. Deuterium and/or Tritium gas is allowed to enter the sphere. Some of the Deuterium or Tritium inside (Hydrogen atoms with an extra neutron (or 2) in the nucleus) becomes ionized (loses its orbiting electron) and gets accelerated toward the center of the sphere where it interacts (fuses?) with other ions or neutral atoms. At any rate ions trapped inside the electron cloud oscillate through center and collide.

Neutrons are somehow produced which escape the equipment and are recorded in quantity by external neutron counters.

A glowing plasma forms and bright flashes occur.

WHAT HAPPENED?


That is the $64 question. When I described what Uncle Phil had told me to my Physics Professors (with his permission) they pointed out that the neutron in Deuterium is not very strongly bound and can be stimulated to come apart without expending great energy. The real proof of fusion would require measuring the neutron energy or detecting Tritium (Hydrogen atoms with 2 neutrons and a proton in the nucleus) or Helium3 (2 protons and one neutron in the nucleus) inside the sphere after the test. The device could only be practical if it produced more energy than it consumed.

I now believe that the two U of Illinois Physics Professors that I discussed this with were putting me off without really thinking about the questions because their answers misled me to think too little about my Uncle's experiments.

The nuclear binding energy of deuterium is the difference in mass (with energy equivalent as per Einstein E=m*c*c) between the Deuterium nucleus (deuteron) and the separate proton and neutron masses of which it is composed. This energy is 2.225 Mev. Thus it takes a particle with energy of at least 2.225Mev to break Deuterium apart (stripping).

The Coulomb barrier between two charged particles with like charge approaching each other is the energy required to overcome the electric repulsion between them and reach close enough to each other such that the nuclear attractive force is greater than the electrical repulsion force. The classical coulomb barrier energy for singly charged ions such as Deuterium or tritium (deutrons or tritons) is about 1.4 Mev depending on the distance chosen for the nuclear force to start dominating.

Thus the energy to split a Deuterium nucleus is more than 1.5 times as big as the energy to cause them to collide.

Farnsworth's Fusor experiments produced free neutrons by applying between 50,000 and 100,000 volts between the cathode and anode. A singly charged ion of Deuterium or Tritium would reach a mean of 50Kev to 100Kev energy by accelerating through a field of this voltage. Subsequent experiments showed that the D-T fusion rate (neutron production rate) peaks at about 70Kev.

This leads to the conclusion that Philo Farnsworth produced D-D fusion in his laboratory at will prior to 1960 and D-T fusion subsequently.

I am still troubled by the factor of ten difference between the calculated coulomb barrier energy and the ion energy in the Farnsworth experiments. That is that a head on collision of two Deuterons each with 700 Kev energy is required to overcome the classical coulomb barrier while Farnsworth was colliding two Deuterons each with 70 Kev energy. Quantum tunneling based on quantum theory has been used to explain such phenomena but the factor of ten seems too much for the rate of neutron production observed.

How Far Did the Experiments Progress?


Phil Farnsworth spent the remainder of his life and most of his wealth pursuing his dream of controlled fusion until his health failed and he passed away on March 11, 1971. He had actually spent as many years exploring nuclear fusion as he had inventing Television.

I heard but sketchy reports during the 10 years that he worked on fusion after I last visited him. I only know that he was totally convinced he had created fusion events inside his fusor and that he was continually making progress toward his goal and that a practical, unlimited source of energy was just around the corner. He was unable to find sufficient financing to complete his work. He was unable to convince visiting scientists that he was on the right track.

Philo Taylor Farnsworth proved many times during his life that his vision was correct and resulted in many practical inventions. The vast reward promised by his controlled fusion device makes me wonder if he might have had the answer in his vision and was unable to communicate that answer to others nor reduce it to practice with the financial resources he had available.

Almost 37 years have passed since Phil Farnsworth's death. In that time many people have built fusors and experimented with them. No one has been able to finish his dream. Although it is simple to cause short intensive bursts of fusion events using the Fusor, it is entirely a different matter to sustain the events long enough to free large amounts of energy and then to capture this energy and use it. D-D and D-T fusion free much of the energy in the form of high energy neutrons which are hard to contain and extract their energy. Fusion of other heavier nuclei with the energy contained in charged particles rather than neutrons seems to have a better chance of becoming a practical energy source. The Hydrogen(Proton) to Boron(5 Protons and 5 or 6 Neutrons) fusion appears to be the most promising

http://www.belljar.net/634fusor.pdf discusses aspects of the Farnsworth "Fusor" and how to make one.

A device for propusion in space based on the fusor is described in a paper on this link: http://fti.neep.wisc.edu/iec/murali1.htm

WHAT IS NUCLEAR FUSION?


Nuclear fusion is the process in which the nuclei of two or more atoms are merged (fused) into another larger nucleus. The energy of the sun (and other stars) is derived from fusing 4 hydrogen atoms into a Helium atom plus 2 electrons plus energy. This fusing results in a net production of energy. This reaction requires very high temperatures and pressures such as exist in the sun.

On Earth physicists have been trying for many years to produce fusion reactions in a controlled process which will safely provide our energy needs without damaging our environment. The Hydrogen bomb uses uncontrolled fusion to produce massive destructive explosions. Current experiments involve a device known as a Stellarator (star machine) or a Tokamak to contain a hot gas of Hydrogen, etc. (a plasma) and thereby create a miniature environment similar to that used by the sun in its fusion process. Scientists have produced fusion in such devices but they are far from being practical and safe.

The Brussard Fusor


Dr. Robert W. Bussard is an American physicist working primarily in nuclear fusion energy research. Bussard received his PhD from Princeton. He has been working with fusors for more than 20 years and has developed a number of changes from the Farnsworth fusors.

The biggest problem of the Farnsworth fusors is that the cathode is constantly impacted by electrons and ions causing it to heat up and melt during attempts to sustain fusion reactions. Dr. Bussard's current invention removes the cathode grid and replaces it with a magnetic field. The magnetic field is used to contain electrons to form a spherical negative potentential well. Ions to be fused are trapped in this spherical well and oscillate through the central area until they are reacted. The system thus acts like a spherical colliding beam device.

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