ZETA (fusion reactor)

ZETA was a major experiment in the early history of fusion power research. It was built at the Atomic Energy Research Establishment in the United Kingdom. Its goal was to produce large numbers of fusion reactions, although it was not large enough to produce net energy. ZETA went into operation in August 1957 and by the end of the month it was giving off bursts of about a million neutrons per pulse.

About ZETA (fusion reactor) in brief

Summary ZETA (fusion reactor)ZETA was a major experiment in the early history of fusion power research. Based on the pinch plasma confinement technique, it was built at the Atomic Energy Research Establishment in the United Kingdom. Its goal was to produce large numbers of fusion reactions, although it was not large enough to produce net energy. ZETA went into operation in August 1957 and by the end of the month it was giving off bursts of about a million neutrons per pulse. Measurements suggested the fuel was reaching between 1 and 5 million kelvins, a temperature that would produce nuclear fusion reactions. The claim that ZETA had produced fusion had to be publicly withdrawn, an embarrassing event that cast a chill over the entire fusion establishment. The neutrons were later explained as being the product of instabilities in the fuel. In spite of ZETA’s failure to achieve fusion, the device went on to have a long experimental lifetime and produced numerous important advances in the field. In one line of development, the use of lasers to more accurately measure the temperature was tested on ZETA, and was later used to confirm the results of the Soviet tokamak approach. In another, while examining ZETA test runs it was noticed that the plasma self-stabilised after the power was turned off. This has led to the modern reversed field pinch concept. The basic understanding of nuclear fusion was developed during the 1920s as physicists explored the new science of quantum mechanics. Using this theory, in 1929 Fritz Houtermans and Robert Atkinson demonstrated that expected reaction rates in the core of the sun supported Arthur Eddington’s 1920 suggestion that the sun is powered by fusion.

In 1934, Mark Oliphant, Paul Harteck and Ernest Rutherford were the first to achieved fusion on Earth, using a particle accelerator to shoot deuterium nuclei into a metal foil. This allowed them to measure the nuclear cross section of various fusion reactions and determined that the reaction occurred at a lower energy than other reactions, peaking at about 100,000 electronvolts. This energy corresponds to the average energy of particles in a gas heated to thousands of millions of kelvin. In 1944 Enrico Enrici calculated this energy would occur at about 50,000,000 K. If that energy can be captured back into the plasma, it can make the reaction self-sustaining. In a simple magnetic field system, the electrons and nuclei orbit the magnetic field, and thus expand to the ideal gas-filled core of a solenoid. A plasma is electrically conductive, subject to electric fields and subject to magnetic fields and is subject to an open-filled magnetic field. This is the ideal confinement system for a fusion reactor. For fusion reactor, the problem is keeping the reactor contained against the known physical pressure; any known physical container would melt at these temperatures. If the fuel is contained against a magnetic field and is open to the field, the plasma will expand according to the Ideal gas law.