Timeline of nuclear fusion

This timeline of nuclear fusion is an incomplete chronological summary of significant events in the study and use of nuclear fusion.

1920s

*1920
**Based on F.W. Aston's measurements of the masses of low-mass elements and Einstein's discovery that E=mc², Arthur Eddington proposes that large amounts of energy released by fusing small nuclei together provides the energy source that powers the stars.
**Henry Norris Russell notes that the relationship in the Hertzsprung–Russell diagram suggests a hot core rather than burning throughout the star. Eddington uses this to calculate that the core would have to be about 40 million Kelvin. This was a matter of some debate at the time, because the value is much higher than what observations suggest, which is about one-third to one-half that value.
*1928
**George Gamow introduces the mathematical basis for quantum tunnelling.
*1929
**Atkinson and Houtermans provide the first calculations of the rate of nuclear fusion in stars. Based on Gamow's tunnelling, they show fusion can occur at lower energies than previously believed. When used with Eddington's calculations of the required fusion rates in stars, their calculations demonstrate this would occur at the lower temperatures that Eddington had calculated.

1930s

*1932
**Ernest Rutherford's Cavendish Laboratory at Cambridge University begins nuclear experiments with a particle accelerator built by John Cockcroft and Ernest Walton.
**In April, Walton produces the first man-made fission by using protons from the accelerator to split lithium into alpha particles.
**Using an updated version of the equipment firing deuterium rather than hydrogen, Mark Oliphant discovered helium-3 and tritium, and that heavy hydrogen nuclei could be made to react with each other. This is the first direct demonstration of fusion in the lab.
*1938
**Kantrowitz and Jacobs of the NACA Langley Research Center built a toroidal magnetic bottle and heat the plasma with a 150 W radio source. Hoping to heat the plasma to millions of degrees, the system fails and they are forced to abandon their Diffusion Inhibitor. This is the first attempt to make a working fusion reactor.
*1939
** Peter Thonemann develops a detailed plan for a pinch device, but is told to do other work for his thesis.
**Hans Bethe provides detailed calculations of the proton–proton chain reaction that powers stars. This work results in a Nobel Prize for Physics.

1940s

*1948
** James L. Tuck and Alan Alfred Ware build a prototype pinch device out of old radar parts at Imperial University.

1950s

*1950
**The tokamak, a type of magnetic confinement fusion device, was proposed by Soviet scientists Andrei Sakharov and Igor Tamm.
*1951
**Edward Teller and Stanislaw Ulam at Los Alamos National Laboratory (LANL) develop the Teller-Ulam design for the thermonuclear weapon, allowing for the development of multi-megaton weapons.
**Fusion work in the UK is classified after the Klaus Fuchs affair.
**A press release from Argentina claims that their Huemul Project had produced controlled nuclear fusion. This prompted a wave of responses in other countries, especially the U.S.
***Lyman Spitzer dismisses the Argentinian claims, but while thinking about it comes up with the stellarator concept. Funding is arranged under Project Matterhorn and develops into the Princeton Plasma Physics Laboratory.
***Tuck introduces the British pinch work to LANL. He develops the Perhapsatron under the codename Project Sherwood. The project name is a play on his name via Friar Tuck.
*** Richard F. Post presents his magnetic mirror concept and also receives initial funding, eventually moving to Lawrence Livermore National Laboratory (LLNL).
***In the UK, repeated requests for more funding that had previously been turned down are suddenly approved. Within a short time, three separate efforts are started, one at Harwell and two at Atomic Weapons Establishment (Aldermaston). Early planning for a much larger machine at Harwell begins.
***Using the Huemul release as leverage, Soviet researchers find their funding proposals rapidly approved. Work on linear pinch machines begins that year.

*1952
**Ivy Mike shot of Operation Ivy, the first detonation of a thermonuclear weapon, yields 10.4 megatons of TNT out of a fusion fuel of liquid deuterium.
**Cousins and Ware build a larger toroidal pinch device in England and demonstrated that the plasma in pinch devices is inherently unstable.
*1953
**The Soviet RDS-6S test, code named " Joe 4", demonstrated a fission/fusion/fission ("Layercake") design for a nuclear weapon.
** Linear pinch devices in the US and USSR report detections of neutrons, an indication of fusion reactions. Both are later explained as coming from instabilities in the fuel, and are non-fusion in nature.
*1954
**Early planning for the large ZETA device at Harwell begins. The name is a take-off on small experimental fission reactors which often had "zero energy" in their name, ZEEP being an example.
**Edward Teller gives a now-famous speech on plasma stability in magnetic bottles at the Princeton Gun Club. His work suggests that most magnetic bottles are inherently unstable, outlining what is today known as the interchange instability.
*1955
**At the first Atoms for Peace meeting in Geneva, Homi J. Bhabha predicts that fusion will be in commercial use within two decades. This prompts a number of countries to begin fusion research; Japan, France and Sweden all start programs this year or the next.
*1956
**Experimental research of tokamak systems started at Kurchatov Institute, Moscow by a group of Soviet scientists led by Lev Artsimovich.
**Construction of ZETA begins at Harwell.
**Igor Kurchatov gives a talk at Harwell on pinch devices, revealing for the first time that the USSR is also working on fusion. He details the problems they are seeing, mirroring those in the US and UK.
**In August, a number of articles on plasma physics appear in various Soviet journals.
**In the wake of the Kurchatov's speech, the US and UK begin to consider releasing their own data. Eventually, they settle on a release prior to the 2nd Atoms for Peace conference in Geneva in 1958.
*1957
**In the US, at LANL, Scylla I begins operation using the θ-pinch design.
**ZETA is completed in the summer, it will be the largest fusion machine for a decade.
**In August, initial results on ZETA appear to suggest the machine has successfully reached basic fusion temperatures. UK researchers start pressing for public release, while the US demurs.
**Scientists at the AEI Research laboratory in Harwell reported that the Sceptre III plasma column remained stable for 300 to 400 microseconds, a dramatic improvement on previous efforts. Working backward, the team calculated that the plasma had an electrical resistivity around 100 times that of copper, and was able to carry 200 kA of current for 500 microseconds in total.
*1958
**In January, the US and UK release large amounts of data, with the ZETA team claiming fusion. Other researchers, notably Artsimovich and Spitzer, are sceptical.
**In May, a series of new tests demonstrate the measurements on ZETA were erroneous, and the claims of fusion have to be retracted.
**American, British and Soviet scientists began to share previously classified controlled fusion research as part of the Atoms for Peace conference in Geneva in September. It is the largest international scientific meeting to date. It becomes clear that basic pinch concepts are not successful and that no device has yet created fusion at any level.
**Scylla demonstrates the first controlled thermonuclear fusion in any laboratory, although confirmation came too late to be announced at Geneva. This θ-pinch approach will ultimately be abandoned as calculations show it cannot scale up to produce a reactor.

1960s

*1960
**After considering the concept for some time, John Nuckolls publishes the concept of inertial confinement fusion. The laser, introduced the same year, appears to be a suitable "driver".
*1961
**The Soviet Union test the Tsar Bomba (50 megatons), the most powerful thermonuclear weapon ever.
*1964
** Plasma temperatures of approximately 40 million degrees Celsius and a few billion deuteron-deuteron fusion reactions per discharge were achieved at LANL with the Scylla IV device.
*1965
**At an international meeting at the UK's new fusion research centre in Culham, the Soviets release early results showing greatly improved performance in toroidal pinch machines. The announcement is met by scepticism, especially by the UK team who's ZETA was largely identical. Spitzer, chairing the meeting, essentially dismisses it out of hand.
**At the same meeting, odd results from the ZETA machine are published. It will be years before the significance of these results are realized.
**By the end of the meeting, it is clear that most fusion efforts have stalled. All of the major designs, including the stellarator, pinch machines and magnetic mirrors are all losing plasma at rates that are simply too high to be useful in a reactor setting. Less-known designs like the levitron and astron are faring no better.
**The 12-beam "4 pi laser" using ruby as the lasing medium is developed at Lawrence Livermore National Laboratory (LLNL) includes a gas-filled target chamber of about 20 centimeters in diameter.
*1967
**Demonstration of Farnsworth-Hirsch Fusor appeared to generate neutrons in a nuclear reaction.
**Hans Bethe wins the 1967 Nobel Prize in physics for his publication on how fusion powers the stars in work of 1939.
*1968
** Robert L. Hirsch is hired by Amasa Bishop of the Atomic Energy Commission as staff physicist. Hirsch would eventually end up running the fusion program during the 1970s.
**Further results from the T-3 tokamak, similar to the toroidal pinch machine mentioned in 1965, claims temperatures to be over an order of magnitude higher than any other device. The Western scientists remain highly sceptical.
**The Soviets invite a UK team from ZETA to perform independent measurements on T-3.
*1969
**The UK team, nicknamed "The Culham Five", confirm the Soviet results early in the year. They publish their results in October's edition of ''Nature''. This leads to a "veritable stampede" of tokamak construction around the world.
**After learning of the Culham Five's results in August, a furious debate breaks out in the US establishment over whether or not to build a tokamak. After initially pooh-poohing the concept, the Princeton group eventually decides to convert their stellarator to a tokamak.

1970s

*1970
**Princeton's conversion of the Model C stellarator to the Symmetrical Tokamak is completed, and tests match the Soviet results. With an apparent solution to the magnetic bottle problem in-hand, plans begin for a larger machine to test the scaling and various methods to heat the plasma.
**Kapchinskii and Teplyakov introduce a particle accelerator for heavy ions that appear suitable as an ICF driver in place of lasers.
*1972
**The first neodymium- doped glass (Nd:glass) laser for ICF research, the "Long Path laser" is completed at LLNL and is capable of delivering ~50 joules to a fusion target.
*1973
**Design work on JET, the Joint European Torus, begins.
*1974
** J.B. Taylor re-visited ZETA results of 1958 and explained that the quiet-period was in fact very interesting. This led to the development of reversed field pinch, now generalised as "self-organising plasmas", an ongoing line of research.
**KMS Fusion, a private-sector company, builds an ICF reactor using laser drivers. Despite limited resources and numerous business problems, KMS successfully compresses fuel in December 1973, and on 1 May 1974 successfully demonstrates the world's first laser-induced fusion. Neutron-sensitive nuclear emulsion detectors, developed by Nobel Prize winner Robert Hofstadter, were used to provide evidence of this discovery.
** Beams using mature high-energy accelerator technology are hailed as the elusive "brand-X" driver capable of producing fusion implosions for commercial power. The Livingston Curve, which illustrates the improvement in power of particle accelerators over time, is modified to show the energy needed for fusion to occur. Experiments commence on the single beam LLNL Cyclops laser, testing new optical designs for future ICF lasers.
*1975
**The Princeton Large Torus (PLT), the follow-on to the Symmetrical Tokamak, begins operation. It soon surpasses the best Soviet machines and sets several temperature records that are above what is needed for a commercial reactor. PLT continues to set records until it is decommissioned.
*1976
**Workshop, called by the US-ERDA (now DoE) at the Claremont Hotel in Berkeley, CA for an ad-hoc two-week summer study. Fifty senior scientists from the major US ICF programs and accelerator laboratories participated, with program heads and Nobel laureates also attending. In the closing address, Dr. C. Martin Stickley, then Director of US-ERDA's Office of Inertial Fusion, announced the conclusion was "no showstoppers" on the road to fusion energy.
**The two beam Argus laser is completed at LLNL and experiments involving more advanced laser-target interactions commence.
**Based on the continued success of the PLT, the DOE selects a larger Princeton design for further development. Initially designed simply to test a commercial-sized tokamak, the DOE team instead gives them the explicit goal of running on a deuterium-tritium fuel as opposed to test fuels like hydrogen or deuterium. The project is given the name Tokamak Fusion Test Reactor (TFTR).
*1977
**The 20 beam Shiva laser at LLNL is completed, capable of delivering 10.2 kilojoules of infrared energy on target. At a price of $25 million and a size approaching that of a football field, the Shiva laser is the first of the "megalasers" at LLNL and brings the field of ICF research fully within the realm of " big science".
**The JET project is given the go-ahead by the EC, choosing the UK's center at Culham as its site.

*1978
**As PLT continues to set new records, Princeton is given additional funding to adapt TFTR with the explicit goal of reaching breakeven.
*1979
**LANL successfully demonstrates the radio frequency quadrupole accelerator (RFQ).
** ANL and Hughes Research Laboratories demonstrate required ion source brightness with xenon beam at 1.5MeV.
**The Foster Panel report to US-DoE's Energy Research and advisory board on ICF concludes that heavy ion fusion (HIF) is the "conservative approach" to ICF. Listing HIF's advantages in his report, John Foster remarked: "...now that is kind of exciting." After DoE Office of Inertial Fusion completed review of programs, Director Gregory Canavan decides to accelerate the HIF effort.

1980s

*1982
**HIBALL study by German and US institutions, Garching uses the high repetition rate of the RF accelerator driver to serve four reactor chambers and first-wall protection using liquid lithium inside the chamber cavity.
**Tore Supra construction starts at Cadarache, France. Its superconducting magnets will permit it to generate a strong permanent toroidal magnetic field.
**high-confinement mode