Editing Nuclear fusion (section)

=== Weaponization ===
{{Main page|Nuclear weapon design|Thermonuclear weapon}}
Research into [[Thermonuclear weapon|fusion for military purposes]] began in the early 1940s as part of the [[Manhattan Project]]. In 1941, Enrico Fermi and Edward Teller had a conversation about the possibility of a fission bomb creating conditions for thermonuclear fusion. In 1942, [[Emil Konopinski]] brought Ruhlig's work on the deuterium–tritium reaction to the projects attention. [[J. Robert Oppenheimer]] initially commissioned physicists at Chicago and Cornell to use the Harvard University cyclotron to secretly investigate its cross-section, and that of the lithium reaction (see below). Measurements were obtained at Purdue, Chicago, and Los Alamos from 1942 to 1946. Theoretical assumptions about DT fusion gave it a similar cross-section to DD. However, in 1946 [[Egon Bretscher]] discovered a [[Resonance (particle physics)|resonance]] enhancement giving the DT reaction a cross-section ~100 times larger.<ref name="r126">{{cite journal |last1=Chadwick |first1=M. B. |last2=Reed |first2=B. Cameron |date=2024-09-02 |title=Introduction to Special Issue on the Early History of Nuclear Fusion |journal=Fusion Science and Technology |volume=80 |issue=sup1 |page= |doi=10.1080/15361055.2024.2346868 |issn=1536-1055 |doi-access=free|bibcode=2024FuST...80D...3C }}</ref>

From 1945, John von Neumann, Teller, and other Los Alamos scientists used [[ENIAC]], one of the first electronic computers, to simulate thermonuclear weapon detonations.<ref name="c888">{{cite journal |date=2014-09-30 |title=Los Alamos Bets on ENIAC: Nuclear Monte Carlo Simulations, 1947–1948 |url=https://ieeexplore.ieee.org/document/6880250 |access-date=2025-03-05 |journal=IEEE Annals of the History of Computing|doi=10.1109/MAHC.2014.40 |last1=Haigh |first1=Thomas |last2=Priestley |first2=Mark |last3=Rope |first3=Crispin |volume=36 |issue=3 |pages=42–63 |url-access=subscription }}</ref>

The first artificial thermonuclear fusion reaction occurred during the 1951 US [[Greenhouse Item|Greenhouse George]] nuclear test, using a small amount of [[Deuterium–tritium fusion|deuterium–tritium]] gas. This produced the largest yield to date, at 225 kt, 15 times that of [[Little Boy]]. The first "true" [[thermonuclear weapon]] detonation i.e. a two-stage device, was the 1952 [[Ivy Mike]] test of a [[Liquid hydrogen|liquid]] [[Deuterium fusion|deuterium-fusing]] device, yielding over 10 Mt. The key to this jump was the full utilization of the fission blast by the [[Teller–Ulam]] design.

The Soviet Union had begun their focus on a hydrogen bomb program earlier, and in 1953 carried out the [[RDS-6s]] test. This had international impacts as the first air-deliverable bomb using fusion, but yielded 400 kt and was limited by its single-stage design. The first Soviet two-stage test was [[RDS-37]] in 1955 yielding 1.5&nbsp;Mt, using an independently reached version of the Teller–Ulam design.

Modern devices benefit from the usage of solid [[lithium deuteride]] with an enrichment of lithium-6. This is due to the [[Jetter cycle]] involving the exothermic reaction:

: {{nuclide|link=yes|lithium|6}} + {{SubatomicParticle|10neutron}} → {{nuclide|Helium|4}} + {{nuclide|Tritium}}
During thermonuclear detonations, this provides tritium for the highly energetic DT reaction, and benefits from its neutron production, creating a closed neutron cycle.<ref name="m027">{{cite arXiv |last1=Fortunato |first1=Lorenzo |last2=Loaiza |first2=Andres Felipe Lopez |last3=Albertin |first3=Giulio |last4=Fragiacomo |first4=Enrico |date=2024-09-30 |title=Jetter and Post nuclear fusion cycles: new fire to an old idea |class=physics.plasm-ph |eprint=2410.09065 }}</ref>