From nuclear transmutation to nuclear fission, 1932-1939

317 Pages·2002·2.116 MB·English

by  Per F Dahl

From Nuclear Transmutation to
Nuclear Fission, 1932–1939
Also by Per F Dahl
Ludvig Colding and The Conservation ofEnergy Principle:
Experimental andPhilosophical Contributions (1972)
Superconductivity: its Historical Rootsand Developmentfrom Mercury
to the CeramicOxides(1992)
American Instituteof Physics
Flash of the Cathode Rays: A History of JJThomson’s Electron (1997)
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From Nuclear Transmutation to
Nuclear Fission, 1932–1939
Per F Dahl
Institute of Physics Publishing
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Contents
Preface vii
Acknowledgments x
List ofIllustrations xii
1 PROLOGUE 1
1.1 1932:Wings over Europe,and other upheavals 1
2 THE ENGLISH STAGE IS SET 5
2.1 Manchester,1919 5
2.2 From Manchester to Cambridge: off to apoor start 9
2.3 Provocations inVienna 14
2.4 Amillionvolts or more? 17
3 AMERICAN BEGINNINGS 25
3.1 South Dakotapals 25
3.2 Geophysics, or smash the atom? 27
3.3 Research aboveallelse 31
4 HOW MANY VOLTS? 36
4.1 New physics, with consequences for smashing
atoms 36
4.2 The Three Musketeers of DTM 43
4.3 Berkeley, and anevening inthe library 49
4.4 Widero¨eandVan de Graaff: accelerator virtuosos 52
5 PROTONS, ELECTRONS, AND GAMMA-RAYS 58
5.1 Protons in Cambridge, and (cid:1)-rays? 58
5.2 Protons in Berkeley 61
5.3 Electrons in Washington, DC 69
v
From Nuclear Transmutation toNuclear Fission, 1932–1939
6 PROTONS EAST AND WEST 75
6.1 One million volt protons 75
6.2 Protons atDTM 79
7 GIANTS OF ELECTRICITY 86
7.1 X-rays in Pasadena 86
7.2 Megavolts on Round Hill 90
8 DIFFICULT YEARS 96
8.1 Depression and other scientificailments 96
9 1932 100
9.1 Moreparticles, expected and unexpected 100
9.2 Cockcroft andWaltonstrike 108
10 RUNNERS UP 119
10.1 Disintegrations at Berkeley, if with difficulty 119
10.2 Disintegrations in Washington as well 125
11 DEUTERIUM 138
11.1 Deutons ontarget 138
11.2 A controversy erupts 144
11.3 The controversy is resolved 150
11.4 Mopping up theheavy water 156
12 THE AMERICANS FORGE AHEAD 160
12.1 Slowdown at theCavendish; Rutherford’s death 160
12.2 Another dispute gives wayto American success 168
12.3 The Rad Lab in action 178
13 FISSION: RETURN OF LIGHTFOOT 186
13.1 Slowneutrons in Rome;nuclear fission in Berlin 186
13.2. News of fission reaches America 194
13.3. Fissionin Berkeley, andCockcroft again in action 204
14 EPILOGUE 215
14.1. Lateryears 215
14.2. Mostly Cockcroft 223
Abbreviations 229
Notes 232
Selectbibliography 266
Name index 275
Subject index 293
vi
Preface
The present volume deals with a particular phase of the early history of
experimental nuclear physics: what in effect became a race, circa 1930,
betweenfourlaboratoryteamstobethefirsttoachievethetransmutation
ofatomicnucleiwith artificiallyaccelerated nuclear projectiles(protons)
in high-voltage discharge tubes or vacuum chambers. (Experiments 15
years earlier under Ernest Rutherford had relied on alpha-particles
fromradiumsourcesinthedisintegrationofnitrogennuclei.)Thelabora-
tories and their team leaders were John D Cockcroft at the Cavendish
Laboratory in Cambridge, England; Merle A Tuve at the Department of
TerrestrialMagnetism (DTM)of theCarnegieInstitution ofWashington;
Ernest OLawrenceatthe Radiation Laboratory andDepartmentofPhy-
sicsoftheUniversityofCaliforniainBerkeley;andCharlesCLauritsenat
the Kellogg Radiation Laboratory, California Institute of Technology in
Pasadena, CA.
As is generally known, the ‘race’ was won by the English team in
1932—the ‘annus mirabilis’ of nuclear physics with a number of impor-
tant breakthroughs in nuclear and particle physics that year. Less well
known are the details of the competing accelerators, the personalities of
theteammembers,theirvariegatedexperiments,andcertainexternalfac-
torsthat played a role in theBritish victory.
Istart,aftersomepreliminaries,withtheearlydaysoftheCavendish
under Rutherford and James Chadwick, with certain provocations from
the Radium Institute in Vienna, and the arrival of John Cockcroft and
hispartnerErnestWaltoninCambridge.Next,wemeetErnestLawrence
andMerleTuve,boyhoodfriendsinSouthDakota.WealsomeetGeorge
Gamow and Gregory Breit, theorists who would profoundly affect the
upcomingcompetition.Earlygeophysicsandhigh-speedelectronexperi-
mentsattheDTMled,oddlyenough,toasuccessfulprotonacceleratorin
Tuve’s laboratory, taking advantage of Robert Van de Graaff and his
clevergenerator.AsayoungprofessoratBerkeley,meanwhile,Lawrence
vii
From Nuclear Transmutation toNuclear Fission, 1932–1939
came across an accelerator scheme by the young Norwegian physicist
RolfWidero¨e,andmagicallytransformeditintohiscyclotron.AtCaltech,
Charlie Lauritsen had his own ideas for the design of a high-voltage
installation for various purposes. With prototype accelerators running
afterafashioninCambridge,inWashington,andinBerkeleyandinPasa-
dena,theracewasoninthemidstofpooreconomictimes.Welearnofthe
success at Cambridge in more ways than one, and how the competition
metthe challenge.
By way of rounding out the volume, we follow subsequent develop-
ments in nuclear science, culminating in the discovery of fission and its
aftermath, and learn how the accelerator laboratories responded to the
discovery, each in their own way. While focusing on a particular theme
in early nuclear physics, the book thus also provides an overview of the
history of modern physics, from Rutherford’s experiment at the end of
WorldWarItoprospectsfornuclearenergyontheeveofWorldWarII.
A ‘sub-plot’ running through much of the narrative, and not so well
known, is connected with the divergent ambitions of the two friendly
rivals, Merle Tuve and Ernest Lawrence. Once ensconced in Berkeley,
Lawrence emphasized ever-more-powerful accelerators, at the expense
of the underlying physics made possible with the new atomic artillery.
Tuve, on the other hand, had his eye on the basic physics from the
start. At the same time he found himself in the awkward position of
chasing down a serious blunder in physics interpretation by his friend
in Berkeley,whilehoninghis own high-precision accelerator technology
in Washington to the point of allowing him to perform the world’s first
fundamental experiments bearing directly on the internal constitution
of the atomic nucleus. In a sense Tuve, less well known than Cockcroft
or Lawrence to most, isthe unsung hero of our story.
My primary sources include the wealth of archival material in
Cambridge,England,inBerkeley,andinWashington,DC.InCambridge,
IhadaccesstothepapersandnotebooksofCockcroft(andErnestWalton)
at Churchill College, as well as the Rutherford archives at Cambridge
University Library. Not to be overlooked is the museum collection of
originalapparatus,aswellasthephotographicarchives,attheCavendish
LaboratorynowadayslocatedintherollingfieldsofwestCambridge.At
Berkeley I availed myself of the E O Lawrence papers, in the Bancroft
Library, University of California, including the Berkeley notebooks of
M Stanley Livingston. In Washington, DC, I had access to the Merle
Tuve papers, all held in the Madison Building, Library of Congress, as
well as archives in the DTM Library of the Carnegie Institution of
Washington. As always important were the extensive holdings of the
NielsBohrLibrary,AmericanInstituteofPhysics,aidedbytheirexcellent
GuidetotheArchivalCollections.TheNielsBohrLibraryholdingsincludea
copy of the Archives for the History of Quantum Physics, which I also
viii
Preface
accessed at the Office for History of Science and Technology of the
University ofCalifornia in Berkeley.
Amongthesecondarysourcespertinenttothesubjectathand,Ihave
profited particularly from Guy Hartcup and T E Allibone’s Cockcroft and
the Atom, Herbert Child’s An American Genius: The Life and Times of
Ernest Orlando Lawrence, and John L Heilbron and Robert W Seidel’s
Lawrence and His Laboratory: A History of the Lawrence Berkeley Laboratory.
As for Tuve’s program, I had the benefit of three unpublished manu-
scripts. The first, ‘Respectfully Submitted, Merle A. Tuve,’ Reports from a
Golden Age of Physics, edited, with notes and comments by Louis Brown,
containsMerleTuve’smonthlyreportstoJohnAFleming,DTMdirector,
from June 1928 to September 1940. The second manuscript, written by
Louis Brown, is a draft for DTM’s Centennial History, prepared by
Brown as part of a larger history of the Carnegie Institution, which will
celebrate its centennial in 2002. The third manuscript was the PhD dis-
sertation by Thomas D Cornell, entitled Merle A Tuve and His Program of
Nuclear Studies at the Department of Terrestrial Magnetism: The Early Career
ofa ModernAmerican Physicist.
Iamindebtedtothefollowingindividualsandinstitutionsforarchival
assistance: Louise King (Churchill Archives Centre, Churchill College,
Cambridge), Godfrey Waller (Cambridge University Library), Keith
Papworth (Cavendish Laboratory, Cambridge), Fred Bauman (Manu-
script Reading Room, Library of Congress), Joseph Andersen and his
staff (Niels Bohr Library, American Institute of Physics, College Park,
MD), Shaun Hardy (DTM Library, Carnegie Institution of Washington),
Rita Labrie (Research Library, Lawrence Berkeley National Laboratory),
andthe staff of theBancroft Library (Universityof California,Berkeley).
Along the way, I have been helped directly and indirectly by many
individuals, including Laurie Brown, Louis Brown, Cathy Carson, John
Heilbron,Roger Stuewer, Diana Wear,and Spencer Weart.
I thank my publisher, Jim Revill, and his editorial staff at Institute of
Physics Publishing, including Simon Laurenson, my editor, for their
splendid supportandcooperationinallstagesofmanuscriptprocessing
andproduction of thevolume.
Finally,thebookdepended,asalways,onEleanor,mypersonaleditor,
companion, and wife. Much of the work on the name index was done
by her; she has a keen sense in copy-editing, and her word processing
expertise was essential. All in all, she is truly a partner in my literary
andhistorical endeavors.
PerF Dahl January 2002
ix