{"id":1278,"date":"2008-12-03T22:03:09","date_gmt":"2008-12-03T22:03:09","guid":{"rendered":"http:\/\/etherwave.wordpress.com\/?p=1278"},"modified":"2008-12-03T22:03:09","modified_gmt":"2008-12-03T22:03:09","slug":"hump-day-history-lawrences-cyclotron","status":"publish","type":"post","link":"https:\/\/rational-action.com\/etherwave\/2008\/12\/03\/hump-day-history-lawrences-cyclotron\/","title":{"rendered":"Primer: Lawrence’s Cyclotron"},"content":{"rendered":"

In the early 1930s, the acceleration of electrons and protons was a popular project.\u00a0 While the spectacular theoretical developments in quantum mechanics had stolen the show in physics in the 1920s, the problem of understanding the atomic nucleus had also become a\u00a0subject of renewed interest\u00a0following on experiments performed by Ernest Rutherford and his coterie at the Cavendish Laboratory at Cambridge University.\u00a0 They had shown that\u00a0bombarding\u00a0nuclei\u00a0with the natural radiation of radioactive\u00a0materials could transmute the subject nuclei into different elements.\u00a0 However, natural radioactive materials were expensive, and their ability to provide incident particles was uncontrolled and inefficient.\u00a0 It was understood that providing some artificial source of high energy (high velocity) particles would make\u00a0bombardment easier, and the exploration of atomic nuclei more systematic and reliable.<\/p>\n

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Edwin McMillan and Ernest Lawrence. Credit: Lawrence Berkeley National Laboratory, courtesy AIP Emilio Segre Visual Archives, Fermi Film Collection<\/figcaption><\/figure>\n

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The obvious means of creating a source was to send particles streaming across a high electrical\u00a0potential difference (high voltage).\u00a0 Lightning accelerated electrons in an uncontrolled way between the sky and the ground—and had, in fact,\u00a0been\u00a0marshaled as a source of ephemeral high voltages.\u00a0 The electrical industry had been vigorously seeking ways of creating high voltages so as to transmit electricity over long distances more effectively.\u00a0 In the laboratory, since the late 19th century, cathode ray tubes had been sending electrons through a vacuum between\u00a0oppositely charged plates.\u00a0 Cathode rays also created x-rays, which were of interest\u00a0as a\u00a0therapy for cancer; and it was expected the higher energy x-rays created in higher voltages would lead to more effective therapies than those already tried.<\/p>\n

So, the production of reliable, high energy accelerators became a scientific premium during the 1920s.\u00a0\u00a0Andthere were a lot of takers.\u00a0 Some physicists, such as John Cockroft at Cavendish, Charles Lauritsen at Caltech, and Merle Tuve at the Department of Terrestrial Magnetism\u00a0of the Carnegie Institution of Washington accelerated particles using variants on the original concept of creating large potential differences.\u00a0 In the early 1930s, Robert Van de Graaff invented his spectacular generator<\/a>, which\u00a0created enormous potentials by transporting charges to a large sphere.\u00a0 The German electrical engineer Rolf Wider\u00f6e (who was interested in constructing electrical devices rather than investigating the nucleus) successfully constructed a method of accelerating particles in steps<\/em>, and published his method in the Arhiv f\u00fcr Electrotechnik <\/em>in 1928.\u00a0 Unlike single potential differences, particles could be accelerated in steps over and over again by adding more accelerating electrodes, leading to far larger particle energies than was otherwise considered practically possible (or safe).<\/p>\n

The physicist Ernest Lawrence (1901-1958) of\u00a0the University\u00a0of California at Berkeley\u00a0(and a boyhood friend of Tuve’s from South Dakota) was a key player in the accelerator sweepstakes.\u00a0 He happened upon Wider\u00f6e’s article, and, one among others, elected, with his graduate students David Sloan and M. Stanley Livingston, to construct accelerators according to this series design—including a design that arranged the electrodes so as to accelerate the particles in a circle.\u00a0 While certainly not the first to imagine what became known as the “cyclotron”, in 1931 Lawrence and Livingston were <\/em>the first to construct a cyclotron with a good enough design so as to keep the particle on its proper track.<\/p>\n

Most accelerator\u00a0development in the late-1920s and early-1930s had been done with the idea of creating particles with a sufficiently <\/em>high energy to facilitate nuclear research, around one million electron-volts (MeV, the energy\u00a0gained by an electron across\u00a0a potential difference of one million volts).\u00a0 However, the cyclotron had a strong potential for scaling well beyond that level, and Lawrence soon dedicated his work to the construction of cyclotrons boasting increasingly high energies as well as to nuclear research.<\/p>\n

To provide a place for accelerator construction, Lawrence established an independent laboratory at Berkeley, which became known as the Radiation Laboratory.\u00a0 However, scaling the cyclotron up was not trivial.\u00a0 Although the cyclotron design solved scale problems inherent to the linear accelerator, it, too, required larger and more sophisticated equipment, and, of course, more money.\u00a0 To solve the second problem and thereby the first, Lawrence appealed to the non-profit Research Corporation<\/a> (which took academic patents and channeled the proceeds into research grants, and which also funded Van de Graaff’s generators) and Chemical Foundation.\u00a0 He also salvaged used magnets and radio equipment.\u00a0 Initial success led to more money from other sources, competition from other\u00a0experiments including in industry,\u00a0and thus to\u00a0demands from his sponsors that he protect his intellectual property.\u00a0 This process led onward, to larger cyclotrons, which required staffs for their design,\u00a0construction and use.\u00a0 Ultimately, this scaled up, big money, big staff, big equipment research became a new kind of fundamental physical research.<\/p>\n

Lawrence would win the 1939 Nobel\u00a0Prize in physics, and his\u00a0cyclotron and the foundation of the Radiation Laboratory are often marked as a turning point between the physics of the small university laboratory and expensive\u00a0“big” physics.\u00a0 It is no coincidence that accelerators, such as the new Large Hadron Collider at CERN <\/a>(7 TeV, or 7 million MeV), are the poster apparatus for this scaled up brand of physics.\u00a0 For much of the 20th century, accelerators\u00a0were a core experimental technology for particle physics well beyond the problem of the behavior of atomic nuclei.\u00a0 Lawrence’s laboratory itself (now called\u00a0the Lawrence Berkeley National Laboratory<\/a>) is a part of the Department of Energy’s system of national labs.\u00a0 Beyond its symbolic historical value, though, it is also worth keeping track of the specific scientific and technological contexts surrounding Lawrence’s original work.\u00a0 Research on the nucleus, for example, persisted using accelerators still on the scale of some of Lawrence’s earlier models.<\/p>\n

The go-to book on this subject is John Heilbron and Bob Seidel’s Lawrence and His Laboratory <\/em>(1989), which based on work done with Bruce Wheaton for the lab’s 50th anniversary celebration in 1981.\u00a0 A website based upon this original work<\/a>, plus visual archives<\/a>, are available at the lab’s web site.\u00a0 Also see the American Institute of Physics’ web exhibit<\/a>.\u00a0 Note that’s two Heilbron books featured\u00a0in two consecutive weeks, on quite different technical topics; that kind of chronological adventurousness is rare in today’s history of science profession.<\/p>\n","protected":false},"excerpt":{"rendered":"

In the early 1930s, the acceleration of electrons and protons was a popular project.\u00a0 While the spectacular theoretical developments in quantum mechanics had stolen the show in physics in the 1920s, the problem of understanding the atomic nucleus had also become a\u00a0subject of renewed interest\u00a0following on experiments performed by Ernest Rutherford and his coterie at<\/p>\n

Continue Reading… Primer: Lawrence’s Cyclotron<\/span>Continue Reading…<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"nf_dc_page":"","_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[14],"tags":[179,231,413,414,801,815,993,1067,1293,1309],"class_list":["post-1278","post","type-post","status-publish","format-standard","hentry","category-ewp-primer","tag-bob-seidel","tag-charles-lauritsen","tag-ernest-lawrence","tag-ernest-rutherford","tag-john-cockroft","tag-john-heilbron","tag-m-stanley-livingston","tag-merle-tuve","tag-robert-van-de-graaff","tag-rolf-wideroe"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/posts\/1278","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/comments?post=1278"}],"version-history":[{"count":0,"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/posts\/1278\/revisions"}],"wp:attachment":[{"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/media?parent=1278"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/categories?post=1278"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/rational-action.com\/etherwave\/wp-json\/wp\/v2\/tags?post=1278"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}