Sixty years on from ZETA … Chris Warrick UK Atomic Energy Authority The Sun … What is powering it? Coal? Lifetime 3,000 years Gravitational Energy? Lifetime 30 million years – Herman Von Helmholtz, Lord Kelvin - mid 1800s The Sun … Suggested the Earth is at least 300 million years old – confirmed by geologists studying rock formations … [Image: Charles Darwin, Origin of Species] The Sun … Albert Einstein (Theory of Special Relativity) and Becquerel / Curie’s work on radioactivity – suggested radioactive decay may be the answer … But the Sun comprises hydrogen … The Sun … Arthur Eddington proposed that fusion of hydrogen to make helium must be powering the Sun “If, indeed, the subatomic energy is being freely used to maintain their great furnaces, it seems to bring a little nearer to fulfilment our dream of controlling this latent power for the well-being of the human race – or for its suicide” Cambridge – 1930s Cockcroft Walton accelerator, Cavendish Laboratory, Cambridge. But huge energy losses and low collisionality Ernest Rutherford : “The energy produced by the breaking down of the atom is a very poor kind of thing . Anyone who expects a source of power from the transformation of these atoms is talking moonshine.” Oxford – 1940s Peter Thonemann – Clarendon Laboratory, Oxford. ‘Pinch’ experiment in glass, then copper tori. First real experiments in sustaining plasma and magnetically controlling them. Imperial College – 1940s George Thomson / Alan Ware – Imperial College London then Aldermaston. Also pinch experiments, but instabilities started to be observed – especially the rapidly growing kink instability. AERE Harwell Atomic Energy Research Establishment (AERE) Harwell – Hangar 7 picked up fusion research. Fusion is now classified. Kurchatov visit 1956 [Images showing Soviet physicist Igor Kurchatov's historic visit and lecture on fusion research] ZETA [Photographs of the Zero Energy Thermonuclear Apparatus experimental area and team] ZETA Zero Energy Thermonuclear Apparatus Pinch experiment – but with added toroidal field to help with instabilities and pulsed DC power supplies. Started in 1957 – and neutrons were soon being measured … ZETA [Images showing international press coverage and headlines such as 'BRITAIN UNVEILS HER SUN - Zeta spells H-power everlasting'] Pathé News – ZETA - H Power For Peace (1958): British scientist working on Zeta machine which produces energy by hydrogen. - Dr. Fry Interviewed On "Zeta" Hydrogen Power From The Sea (1958): Dr. Fry being interviewed - Taming The H Bomb (1958): Scientists at Harwell research into Nuclear fusion for power generation Princeton – 1950s Lyman Spitzer – Princeton Developed the first stellerator – in a figure of eight - so particle drift is (theoretically) cancelled out. Longer pulse lengths should be achievable as there is no externally driven plasma current. Lawrence Livermore – 1950s Post and others – mirror machines. Linear devices where magnetic mirrors are used to ‘block’ the ends of the vessel. “Atoms for Peace” Geneva 1958 was preceded by full declassification and resulted in intense discussions between east and West … … but a realisation that all schemes (stellerators, pinches and mirror machines had serious drawbacks). RNAS Culham / HMS Hornbill [Photographs of the Royal Naval Air Station Culham airfield prior to becoming the Culham Science Centre / fusion laboratory] IAEA Conference 1965 .. was held at the new Culham Laboratory to mark its opening. Spitzer reviewed current results, noting that all schemes has drawbacks – Stellerators suffered from excessive Bohm diffusion and pinches rapid instabilities – especially kinks. One bright spot – Lev Artsimovich from the USSR – who described encoraging results from a so-called “Toroidálʹnaya kámera s magnítnymi katúškami” - or Tokamak. The toroidal field was much (by factor 500) larger than in classical pinch devices. T3 Tokamak T-3 - the first true tokamak at the Kurchatov Institute of Atomic Energy. Boasted high confinement times (10ms) and high plasma temperatures (10 million degrees C) – but all measurements were indirect … Moscow 1969 [Images showing the UK Culham team (The 'Culham Five') visiting Moscow with Thomson scattering laser equipment to measure T-3 tokamak temperatures] Experiments 1970s Levitron TOSCA Experiments 1980s DITE TORSO A European Tokamak An ambitious project – the Joint European Torus – was formulated. Plasma of 100m3 – a hundred times bigger than any other tokamak. Capable of using Tritium as well as Deuterium and including full remote handling. JET site decision [Aerial views of Culham and Garching sites, and political leaders negotiating the site decision in 1977] JET construction [Photographs of building construction at Culham in 1980] JET construction [Photographs of JET mechanical structure and magnetic coil assembly] TFTR - Princeton The USA adopted tokamaks quickly. TFTR was built to achieve breakeven. Large beam heating systems and a standard circular vessel. Relatively simple design using known technologies. Started in 1982 – with Tritium capability. JET –v- TFTR JET – D shaped vessel. Coils are stronger and theory suggests more plasma current can be driven. TFTR – circular vessel. Quicker to construct and known technology. First plasmas – 1982 / 1983 [Photographs of control room celebrations and early computing hardware including the ZX Spectrum] H-mode Accidental discovery of high confinement mode – maintaining high density and temperature across the plasma, with a pedestal at the edge. [Diagram comparing L-mode and H-mode profile with edge transport barrier] D-T experiments JET – September 1997 16MW of fusion power remains a world record. Q ~ 0.7 [Chart showing Fusion power (MW) vs Time (s) comparing JET and TFTR Deuterium-Tritium pulses] All the World’s Tokamaks More than 50 devices Comparison of plasma cross-sections: T3, DIII-D, JET, ITER (4 m scale) ITER Reagan and Gorbachev agreed to the ITER project in 1985. Formal signing and site selected in 2006. Construction now underway … First plasma in Dec 2025. [Photograph of the ITER Tokamak Complex and assembly hall construction at Saint-Paul-lez-Durance, France] Stellerators Much more advanced than Spitzer’s early versions (e.g. Wendelstein 7-X) – but inherently still removing non-uniform fields by generating combined helical field structure with one coil set. “Stellerators a beast to build; tokamaks a beast to operate” [Comparison between Stellarator (e.g. W7-X) and Tokamak (e.g. ASDEX Upgrade) coil and field topologies] Spherical Tokamaks [Images showing compact spherical tokamak plasma, device internal structure, and engineering cutaway]