Editing Tokamak (section)

==== Culham Five ====
In the aftermath of ZETA, the UK teams began the development of new plasma diagnostic tools to provide more accurate measurements. Among these was the use of a [[laser]] to directly measure the temperature of the bulk electrons using [[Thomson scattering]]. This technique was well known and respected in the fusion community;{{sfn|Bromberg|1982|p=172}} Artsimovich had publicly called it "brilliant". Artsimovich invited [[Bas Pease]], the head of Culham, to use their devices on the Soviet reactors. At the height of the [[Cold War]], in what is still considered a major political manoeuvre on Artsimovich's part, British physicists were allowed to visit the Kurchatov Institute, the heart of the Soviet nuclear bomb effort.<ref>{{cite web |url=https://www.walesonline.co.uk/news/wales-news/valleys-boy-who-broached-iron-1794244 |title= The Valleys boy who broached the Iron Curtain to convince the USA that Russian Cold War nuclear fusion claims were true |date=3 November 2011 |website=WalesOnline}}</ref>

The British team, nicknamed "The Culham Five",<ref>{{cite magazine |first=Robert |last=Arnoux |url=http://www.iter.org/newsline/102/1401 |title=Off to Russia with a thermometer |magazine=ITER Newsline |issue=102 |date=9 October 2009}}</ref> arrived late in 1968. After a lengthy installation and calibration process, the team measured the temperatures over a period of many experimental runs. Initial results were available by August 1969; the Soviets were correct, their results were accurate. The team phoned the results home to Culham, who then passed them along in a confidential phone call to Washington.{{sfn|Bromberg|1982|p=167}} The final results were published in ''Nature'' in November 1969.<ref name=culham>{{cite journal |first1=N. J. |last1=Peacock |first2=D. C. |last2=Robinson |first3=M. J. |last3=Forrest |first4=P. D. |last4=Wilcock |first5=V. V. |last5=Sannikov |s2cid=4290094 |title=Measurement of the Electron Temperature by Thomson Scattering in Tokamak T3 |journal=[[Nature (journal)|Nature]] |volume=224 |issue=5218 |pages=488–490 |year=1969 |doi=10.1038/224488a0 |bibcode=1969Natur.224..488P }}</ref> The results of this announcement have been described as a "veritable stampede" of tokamak construction around the world.<ref>{{cite magazine |magazine=New Scientist |title=Fusion research - the temperature rises |first=Michael |last=Kenward |url=https://books.google.com/books?id=tbhTdnZsqMUC&pg=PA626 |date=24 May 1979 }}{{Dead link|date=May 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>

One serious problem remained. Because the electrical current in the plasma was much lower and produced much less compression than a pinch machine, this meant the temperature of the plasma was limited to the resistive heating rate of the current. First proposed in 1950, [[Spitzer resistivity]] stated that the [[electrical resistance]] of a plasma was reduced as the temperature increased,<ref name="Spitzer 1950">{{cite journal
 |last1=Cohen |first1=Robert S.
 |last2=Spitzer |first2=Lyman Jr.
 |last3=McR. Routly |first3=Paul
 |title=The Electrical Conductivity of an Ionized Gas
 |date=October 1950
 |journal=Physical Review
 |volume=80
 |issue=2
 |pages=230–238
 |url=http://ayuba.fr/pdf/spitzer1950.pdf
 |doi=10.1103/PhysRev.80.230
|bibcode=1950PhRv...80..230C}}</ref> meaning the heating rate of the plasma would slow as the devices improved and temperatures were pressed higher. Calculations demonstrated that the resulting maximum temperatures while staying within ''q'' > 1 would be limited to the low millions of degrees. Artsimovich had been quick to point this out in Novosibirsk, stating that future progress would require new heating methods to be developed.{{sfn|Bromberg|1982|p=161}}