View source for Louis Slotin

{{Short description|Canadian physicist and chemist}}
{{pp-move|small=yes}}
{{Use dmy dates|date=May 2022}}
{{Infobox person
| birth_name         = Louis Alexander Slotin
| name               = Louis Slotin
| image              = Slotin Los Alamos.jpg
| caption            = Slotin's Los Alamos badge photo
| birth_date         = {{birth date|1910|12|1|df=y}}
| birth_place        = [[Winnipeg]], Manitoba, Canada
| death_date         = {{death date and age|1946|5|30|1910|12|1|df=y}}
| death_place        = [[Los Alamos National Laboratory]], New Mexico, U.S.
| death_cause        = [[Acute radiation syndrome]]
| occupation         = [[Physicist]] and [[chemist]]
| resting_place      = [[Shaarey_Zedek_Cemetery_(Winnipeg)|Shaarey Zedek Cemetery]]
| education          = {{ubl|[[University of Manitoba]] ([[Bachelor of Science|BSc]], [[Master of Science|MSc]]) | [[King's College London]] (PhD)}}
| known_for          = Criticality tests on plutonium and nuclear weapons assembling, the [[Dollar (reactivity)|dollar unit of reactivity]]
}}

'''Louis Alexander Slotin''' ({{IPAc-en|'|s|l|ou|t|I|n}} {{respell|SLOHT-in}};<ref>{{Cite AV media |title=The Slotin Accident |url=https://www.youtube.com/watch?v=utZFyzh7Dyk |date=Oct 18, 2017 |language=en |publisher=AtomicHeritage |via=YouTube |access-date=2024-02-19}}</ref> 1 December 1910&nbsp;– 30 May 1946) was a Canadian [[physicist]] and [[chemist]] who took part in the [[Manhattan Project]]. Born and raised in the [[North End, Winnipeg|North End]] of [[Winnipeg]], Manitoba, Slotin earned both his Bachelor of Science and Master of Science degrees from the [[University of Manitoba]], before obtaining his doctorate in physical chemistry at [[King's College London]] in 1936. Afterwards, he joined the [[University of Chicago]] as a research associate to help design a [[cyclotron]].

In 1942, Slotin was invited to participate in the Manhattan Project, and subsequently performed experiments with [[uranium]] and [[plutonium]] [[pit (nuclear weapon)|cores]] to determine their [[critical mass]] values. After [[World War II]], he continued his research at [[Los Alamos National Laboratory]] in [[New Mexico]]. On 21 May 1946, he accidentally triggered a supercritical [[Nuclear chain reaction|nuclear chain reaction]], which released a burst of [[hard radiation]]. He was rushed to the hospital and died nine days later on 30 May. Slotin had become the second fatal victim of a [[criticality accident]] in history, following [[Harry Daghlian]], who had died of a related accident with the same plutonium "[[demon core]]" the previous year.

Slotin was hailed as a hero by the United States government for reacting quickly enough to prevent the deaths of his colleagues. However, some physicists argue that Slotin's behavior preceding the accident was reckless and that his death was preventable. The accident and its aftermath have been dramatized in several fictional and non-fictional accounts.

== Early life ==
Louis Slotin was the first of three children born to Israel and Sonia Slotin, [[Yiddish]]-speaking [[Jews|Jewish]] refugees who had fled the [[Anti-Jewish pogroms in the Russian Empire|pogroms of Russia]] to [[Winnipeg]], Manitoba. He grew up in the [[North End, Winnipeg|North End]] neighborhood of Winnipeg, an area with a large concentration of Eastern European immigrants. From his early days at Machray Elementary School through his teenage years at [[St. John's High School (Winnipeg)|St. John's High School]], Slotin was academically exceptional. His younger brother, Sam, later remarked that his brother "had an extreme intensity that enabled him to study long hours."<ref name="zeilig22">{{cite journal|last=Zeilig |first=Martin |date=August–September 1995 |title=Louis Slotin and 'The Invisible Killer' |journal=The Beaver |volume=75 |issue=4 |pages=20–27 |url=http://www.mphpa.org/classic/FH/LA/Louis_Slotin_1.htm |access-date=28 April 2008 |archive-url=https://web.archive.org/web/20080516101332/http://www.mphpa.org/classic/FH/LA/Louis_Slotin_1.htm |archive-date=16 May 2008 |url-status=dead }}</ref>

At age 16, Slotin entered the [[University of Manitoba]] to pursue a degree in science. During his undergraduate years, he received a University Gold Medal in both physics and chemistry. Slotin received a [[Bachelor of Science|B.Sc.]] degree in geology from the university in 1932 and a [[Master of Science|M.Sc.]] degree in 1933. With the assistance of one of his mentors, he obtained a fellowship to study at [[King's College London]] under the supervision of [[Arthur John Allmand]],<ref name="zeilig22" /> the chair of the chemistry department, who specialized in the field of applied [[electrochemistry]] and [[photochemistry]].<ref>{{cite journal |year=1951 |title=In memoriam: Arthur John Allmand, 1885–1951 |journal=[[Faraday Transactions|Journal of the Chemical Society, Faraday Transactions]] |volume=47 |pages=X001–X003 |url=http://www.rsc.org/delivery/_ArticleLinking/DisplayArticleForFree.cfm?doi=TF951470X001&JournalCode=TF |doi= 10.1039/TF951470X001|access-date= 19 December 2007|url-access=subscription }}</ref>

=== King's College London ===
While at King's College London, Slotin distinguished himself as an [[amateur boxing|amateur boxer]] by winning the college's amateur bantamweight boxing championship. Later, he gave the impression that he had fought for the [[Second Spanish Republic|Spanish Republic]] and trained to fly a fighter with the [[Royal Air Force]].<ref name="Obit">{{cite journal |last=Anderson |first=H. L. |author2=A. Novick |author3=P. Morrison  |date=23 August 1946 |title=Louis A. Slotin: 1912–1946 |url=https://archive.org/details/sim_science_1946-08-23_104_2695/page/182 |journal=[[Science (journal)|Science]] |volume=104 |issue=2695 |pages=182–183 |doi=10.1126/science.104.2695.182 |pmid=17770702|bibcode = 1946Sci...104..182A }}</ref> Author [[Robert Jungk]] recounted in his book ''[[Brighter than a Thousand Suns: A Personal History of the Atomic Scientists]]'', an early history of the [[Manhattan Project]], that Slotin "had volunteered for service in the [[Spanish Civil War]], more for the sake of the thrill of it than on political grounds. He had often been in extreme danger as an anti-aircraft gunner."<ref>{{cite book | last= Jungk | first= Robert | author-link= Robert Jungk | title= [[Brighter than a Thousand Suns: A Personal History of the Atomic Scientists|Brighter than a Thousand Suns]] | publisher= Harcourt Brace | year= 1958 | location= New York | isbn=0156141507 | oclc= 181321 | pages= [https://archive.org/details/brighterthanthou00jung_0/page/194 194–196] }}</ref> During an interview years later, Sam stated that his brother had gone "on a walking tour in Spain" and he "did not take part in the war" as previously thought.<ref name="zeilig22" />

Slotin earned a [[Doctor of Philosophy|Ph.D.]] in [[physical chemistry]] from King's College London in 1936.<ref name="Obit" /> He won a prize for his thesis entitled "An Investigation into the Intermediate Formation of Unstable Molecules During some Chemical Reactions." Afterwards, he spent six months working as a special investigator for [[Dublin]]'s [[Great Southern Railways]], testing the [[nickel-zinc battery|Drumm nickel-zinc rechargeable batteries]] used on the [[Harcourt Street railway line|Dublin–Bray line]].<ref name="zeilig22" />

== Career ==
=== University of Chicago ===
In 1937, after he unsuccessfully applied for a job with Canada's [[National Research Council of Canada|National Research Council]],<ref>{{cite web | title = Louis Slotin And 'The Invisible Killer' | publisher = The Manhattan Project Heritage Preservation Association, Inc. | author = Martin Zeilig | date = August–September 1995 | url = http://www.mphpa.org/classic/FH/LA/Louis_Slotin_2.htm | access-date = 13 May 2012 | archive-url = https://web.archive.org/web/20130116154040/http://www.mphpa.org/classic/FH/LA/Louis_Slotin_2.htm | archive-date = 16 January 2013 | url-status = dead }}</ref> the [[University of Chicago]] accepted Slotin as a research associate. There, he gained his first experience with nuclear chemistry, helping to build the first [[cyclotron]] in the midwestern United States.<ref name="science.ca">{{cite web| title = science.ca Profile: Louis Slotin| publisher = GCS Research Society  | date = 7 November 2007| url = http://www.science.ca/scientists/scientistprofile.php?pID=290&pg=0| access-date = 21 November 2007}}</ref> The job paid poorly and Slotin's father had to support him for two years. From 1939 to 1940, Slotin collaborated with [[Earl Evans (scientist)|Earl Evans]], the head of the university's biochemistry department, to produce radiocarbon ([[carbon-14]] and [[carbon-11]]) from the cyclotron.<ref name="zeilig22" /> While working together, the two men also used carbon{{nbhyph}}11 to demonstrate that [[plant cell]]s had the capacity to use [[carbon dioxide]] for [[carbohydrate metabolism|carbohydrate synthesis]], through [[carbon fixation]].<ref><!-- The referenced bio article says "animal cells" like photosynthetic plants. This is clearly in error. Plants cells are meant--> {{cite web|title = Earl Evans, 1910–1999|publisher = [[University of Chicago Medical Center]] | date = 5 October 1999|url = https://www.uchospitals.edu/news/1999/19991005-evansobit.html|access-date = 20 December 2007 }}</ref>

Slotin might have been present at the start-up of [[Enrico Fermi]]'s "[[Chicago Pile-1]]", the first [[nuclear reactor]], on 2 December 1942; the accounts of the event do not agree on this point.<ref group=notes>A 1962 University of Chicago document says that Slotin "was present on 2 December 1942, when the group of 'Met Lab' [Metallurgical Laboratory] scientists working under the late Enrico Fermi achieved man's first self-sustaining nuclear chain reaction in a pile of [[graphite]] and uranium under the West Stands of [[Stagg Field]]." Slotin's colleague, Henry W. Newson, recollected that he and Slotin were not present during the scientists' experimentation.</ref> During this time, he also contributed to several papers in the field of [[radiobiology]]. His expertise on the subject garnered the attention of the United States government, and as a result he was invited to join the Manhattan Project, an effort to develop an [[atomic bomb]].<ref name="science.ca"/> Slotin worked on the production of [[plutonium]] under future [[List of Nobel laureates|Nobel laureate]] [[Eugene Wigner]] at the university and later at the [[Oak Ridge National Laboratory]] in [[Oak Ridge, Tennessee|Oak Ridge]], [[Tennessee]]. He moved to the [[Los Alamos National Laboratory]] in [[New Mexico]] in December 1944 to work in the bomb physics group of [[Robert Bacher]].<ref name="zeilig22"/>

== Work at Los Alamos ==
At Los Alamos, Slotin's duties consisted of dangerous [[Critical mass|criticality]] testing, first with [[uranium]] in [[Otto Robert Frisch]]'s experiments, and later with plutonium [[pit (nuclear weapon)|cores]]. Criticality testing involved bringing masses of [[fissile]] materials to near-critical levels to establish their [[critical mass]] values.<ref name="Martin">{{cite journal |last=Martin |first=Brigitt |date=December 1999 |title=The Secret Life of Louis Slotin 1910–1946 |journal= Alumni Journal of the University of Manitoba |volume=59 |issue=3 | url=http://www.cns-snc.ca/history/pioneers/slotin/slotin.html |access-date= 22 November 2007 |archive-url = https://web.archive.org/web/20071007121854/http://www.cns-snc.ca/history/pioneers/slotin/slotin.html |archive-date = 7 October 2007|url-status=dead}}</ref> Scientists referred to this flirting with the possibility of a [[nuclear chain reaction]] as "[[Demon core|tickling the dragon's tail]]", based on a remark by physicist [[Richard Feynman]] comparing the experiments to "tickling the tail of a sleeping dragon".<ref name="NYT"/><ref>{{cite journal |date=November–December 2002 |title=Science as Theater: The Slip of the Screwdriver |journal=[[American Scientist]] |volume=90 |issue=6 |pages=550–555 |bibcode = 2002AmSci..90..550S |doi = 10.1511/2002.6.550 |last1= Shepherd-Barr |first1= Kirsten |last2= Lustig |first2= Harry |s2cid=208868168 }}</ref> On 16 July 1945, Slotin assembled the core for [[Trinity test|Trinity]], the first detonated atomic device, and became known as the "chief armorer of the United States" for his expertise in assembling nuclear weapons.<ref>{{cite book | last=Durschmied | first=Erik | title=Unsung Heroes: The Twentieth Century's Forgotten History-Makers | publisher=[[Hodder & Stoughton]] | location=London | year=2003 | isbn=0340825197 | page=[https://archive.org/details/unsungheroestwen0000durs/page/245 245] | url=https://archive.org/details/unsungheroestwen0000durs/page/245 }}</ref><ref name="Sullivan 2016 p. 16-17">{{cite book | last=Sullivan | first=Neil J. | title=The Prometheus Bomb: The Manhattan Project and Government in the Dark |location=Lincoln | publisher=[[University of Nebraska Press]] | year=2016 | isbn=978-1612348902 | url=https://books.google.com/books?id=Md4nDwAAQBAJ | access-date=30 November 2021 | pages=16–17 }}</ref> Slotin received two small circular lead and silver commemorative pins for his work on the project.<ref name="zeilig22" />

[[File:Louis Slotin and the Gadget Bomb.jpg|thumb|Louis Slotin ({{em|left}}) with [[the Gadget]] bomb during the Trinity test]]
In the winter of 1945–1946, Slotin shocked some of his colleagues with a bold action by repairing an instrument {{Convert|6|ft}} under water inside the [[Clinton Pile]] while it was operating, rather than wait an extra day for the reactor to be shut down. He did not wear his [[dosimetry]] badge, but his dose was estimated to be at least 100 [[roentgen (unit)|roentgen]].<ref name="ziegler">{{cite book|last1=Morgan|first1=Karl Ziegler|last2=Peterson|first2=Ken M.|title=The Angry Genie: One Man's Walk Through the Nuclear Age|url=https://archive.org/details/angrygenieoneman0000morg|url-access=registration|access-date=30 May 2012|year=1999|publisher=University of Oklahoma Press|isbn=978-0806131221|pages=[https://archive.org/details/angrygenieoneman0000morg/page/34 34]–35}}</ref> A dose of 1 [[Gray (unit)|Gy]] (≈100 roentgen) can cause nausea and vomiting in 10% of cases, but is generally survivable.<ref>{{cite journal|last=Mettler Jr. |first=Fred A. |author2=Voelz, George L. |title=Major Radiation Exposure – What to Expect and How to Respond |journal=New England Journal of Medicine |date=16 May 2002 |volume=346 |issue=20 |pmid=12015396 |url=http://web.engr.oregonstate.edu/~higley/Radiation%20Biology/Exams%20and%20quizzes/major%20radiation%20exposure%20what%20to%20expect%20and%20how%20to%20respond%20mettler.pdf |access-date=15 November 2012 |doi=10.1056/NEJMra000365 |pages=1554–1561 |url-status=dead |archive-url=https://web.archive.org/web/20130226030448/http://web.engr.oregonstate.edu/~higley/Radiation%20Biology/Exams%20and%20quizzes/major%20radiation%20exposure%20what%20to%20expect%20and%20how%20to%20respond%20mettler.pdf |archive-date=26 February 2013 }}</ref>

=== Harry Daghlian's death ===
On 21 August 1945, laboratory assistant [[Harry Daghlian]], one of Slotin's close colleagues, was performing a criticality experiment when he accidentally dropped a heavy [[tungsten carbide]] brick onto a {{convert|6.2|kg|adj=on}} [[plutonium–gallium alloy]] bomb core, later nicknamed [[demon core]], which would later also kill Slotin.<ref>{{cite book | last=Newtan | first=Samuel Upton | title= Nuclear War I and Other Major Nuclear Disasters of the 20th Century | publisher= [[AuthorHouse]] | location=[[Bloomington, Indiana]] | year = 2007|isbn=978-1425985103 | page=67 }}</ref> The 24-year-old Daghlian was irradiated with a large dose of [[neutron radiation]]. Later estimates suggested that this dose might not have been fatal on its own, but he then received additional delayed [[gamma radiation]] and [[beta burns]] while disassembling his experiment.<ref name=hoffman /> He quickly collapsed with [[acute radiation poisoning]] and died 25 days later in the Los Alamos base hospital.<ref name="Sullivan 2016 p. 16">{{harvnb | Sullivan | 2016 | p=16 }}</ref>

=== Planned return to teaching ===
After [[World War II]], Slotin expressed growing disdain for his personal involvement in the project. He remarked, "I have become involved in the [[United States Navy|Navy]] tests, much to my disgust."<ref name="zeilig22" /> Unfortunately for Slotin, his participation at Los Alamos was still required because, as he said, "I am one of the few people left here who are experienced bomb putter-togetherers." He looked forward to resuming teaching and research into [[biophysics]] and radiobiology at the University of Chicago. He began training a replacement, [[Alvin C. Graves]], to take over his role at Los Alamos.<ref name="zeilig22" />

=== Criticality accident ===
[[File:Tickling the Dragons Tail.jpg|thumb|A re-creation of the Slotin incident. The inside hemisphere with the thumb-hole next to the demonstrator's hand is beryllium (replacing the uranium tamper of the same size in a [[Fat Man]] bomb). There is an external larger metal sphere of aluminium under it (replacing the pusher sphere in this bomb's design). The plutonium "[[demon core]]" was inside the spheres at the time of the accident and is not visible, but its dimensions are comparable with the two small half-spheres shown resting nearby.]]
On 21 May 1946, with seven colleagues watching, Slotin performed an experiment that involved the creation of one of the first steps of a [[Nuclear fission|fission reaction]] by placing two half-spheres of [[beryllium]] (a [[neutron reflector]]) around a {{convert|3.5|in|mm|adj=mid|-diameter}} plutonium core. The experiment used the same {{convert|6.2|kg|lb|1|adj=on}} plutonium core that had irradiated Daghlian, later called the "[[demon core]]" for its role in the two accidents. Slotin grasped the upper 228.6&nbsp;mm (9-inch) beryllium hemisphere<ref name=hoffman /> with his left hand through a thumb hole at the top while he maintained the separation of the half-spheres using the blade of a screwdriver. The standard protocol was to use [[shim (spacer)|shim]]s between the halves, as allowing them to close completely could result in the instantaneous formation of a critical mass and a lethal power excursion.<ref name="zeilig22" /><ref name="Sullivan 2016 p. 16-17"/><ref name=accidents>{{cite web |url=http://library.lanl.gov/cgi-bin/getfile?00314607.pdf |title=A Review of Criticality Accidents |date=September 26, 1967 |publisher=[[Los Alamos Scientific Laboratory]] |access-date=August 12, 2015 |url-status=live |archive-url=https://web.archive.org/web/20170118111722/http://library.lanl.gov/cgi-bin/getfile?00314607.pdf |archive-date=January 18, 2017 }}</ref>

By Slotin's own unapproved protocol, the shims were not used. The top half of the reflector was resting directly on the bottom half at one point, while 180 degrees from this point a gap was maintained by the blade of a flat-tipped [[screwdriver]] in Slotin's hand. The size of the gap between the reflectors was changed by twisting the screwdriver. Slotin, who was given to bravado,<ref>{{Cite web|url=https://iflscience.com/the-demon-core-accident-how-one-man-stopped-a-nuclear-detonation-with-his-bare-hands-59736|title=The Demon Core: How One Man Intervened With His Bare Hands During A Nuclear Accident|website=IFLScience|date=17 May 2021 }}</ref> became the local expert, performing the test on almost a dozen occasions, often in his trademark blue jeans and cowboy boots in front of a roomful of observers. [[Enrico Fermi]] reportedly told Slotin and others they would be "dead within a year" if they continued performing the test in that manner.<ref>{{cite book | title = The Plutonium Files | last = Welsome | first = Eileen | page = [https://archive.org/details/plutoniumfiles00wels_0/page/184 184] | year = 1999 | isbn = 978-0-385-31402-2 | location = New York | publisher = Dial Press | url = https://archive.org/details/plutoniumfiles00wels_0/page/184 | access-date = November 18, 2012 }}</ref> Scientists referred to this flirtation with a [[nuclear chain reaction]] as "tickling the dragon's tail", based on a remark by physicist [[Richard Feynman]].<ref name="NYT">{{cite news |last=Weber |first=Bruce |title=Theater Review; A Scientist's Tragic Hubris Attains Critical Mass Onstage |url=https://www.nytimes.com/2001/04/10/theater/theater-review-a-scientist-s-tragic-hubris-attains-critical-mass-onstage.html |work=[[The New York Times]] |date=10 April 2001 |access-date=12 November 2007 |archive-date=3 November 2012 |archive-url=https://web.archive.org/web/20121103135846/http://www.nytimes.com/2001/04/10/theater/theater-review-a-scientist-s-tragic-hubris-attains-critical-mass-onstage.html |url-status=live }}</ref><ref>{{cite journal |date=November–December 2002 |title=Science as Theater: The Slip of the Screwdriver |journal=[[American Scientist]] |publisher=[[Sigma Xi]] |volume=90 |issue=6 |pages=550–555 |bibcode = 2002AmSci..90..550S |doi = 10.1511/2002.6.550 |last1= Shepherd-Barr |first1= Kirsten |last2= Lustig |first2= Harry |s2cid=208868168 |url=http://www.americanscientist.org/issues/feature/2002/6/science-as-theater/99999 |archive-url=https://web.archive.org/web/20170520181417/http://www.americanscientist.org/issues/feature/2002/6/science-as-theater/99999 |archive-date=May 20, 2017 |url-status=dead|url-access=subscription }}</ref>

At 3:20&nbsp;p.m., the screwdriver slipped and the upper beryllium hemisphere fell, causing a "[[prompt critical]]" reaction and a burst of [[hard radiation]].<ref name="Martin" /> Scientists observed the blue glow of [[Ionized air glow|air ionization]] and felt a heat wave. Slotin experienced a sour taste in his mouth and an intense burning sensation in his left hand. He jerked his left hand upward, lifting the upper beryllium hemisphere, and dropped it to the floor, ending the reaction. Slotin had already been exposed to a lethal dose of neutron radiation, however.<ref name="zeilig22" />

At the time of the accident, dosimetry badges were in a locked box about {{convert|100|ft|m}} from where the reaction occurred. Realizing that no one in the room had their film badges on, "immediately after the accident Dr. Slotin asked Dr. [[Raemer E. Schreiber]] to have the badges taken from the lead box and placed on the critical assembly".<ref name=hoffman /> This peculiar response was of no value for determining the actual doses received by the men in the room and put Schreiber at "great personal risk" of additional exposure. A report later concluded that a heavy dose of radiation may produce [[vertigo]] and can leave a person "in no condition for rational behavior."<ref name=hoffman /> As soon as Slotin left the building he vomited, a common reaction from exposure to extremely intense [[ionizing radiation]]. Slotin's colleagues rushed him to the hospital, but the radiation damage was irreversible.<ref name="zeilig22" />

The six other men present at the time of the reaction included [[Alvin C. Graves|Alvin Cushman Graves]], Samuel Allan Kline, Marion Edward Cieslicki, [[Dwight Smith Young]], Theodore P. Perlman, and [[Private (rank)|Pvt.]] Patrick J. Cleary.<ref name="hempelman">{{cite conference|last1=Hempelman|first1=Louis Henry|last2=Lushbaugh|first2=Clarence C.|last3=Voelz|first3=George L.|date=19 October 1979|title=What Has Happened to the Survivors of the Early Los Alamos Nuclear Accidents?|url=https://www.orau.org/ptp/pdf/accidentsurvivorslanl.pdf|conference=Conference for Radiation Accident Preparedness|location=Oak Ridge|publisher=Los Alamos Scientific Laboratory|id=LA-UR-79-2802|access-date=5 January 2013}} There have been five studies done of the amount of radiation each person involved received in the accident; these are the latest, dated 1978, from a table in this reference.</ref><ref name="schreiber">{{cite news|title=Nuclear Niaveté|author=Larry Calloway|journal=Albuquerque Journal|url=http://www.abqjournal.com/trinity/trinity2.pdf}}</ref><ref>{{cite news| url=https://www.nytimes.com/1998/12/31/us/re-schreiber-88-nuclear-bomb-physicist.html | work=The New York Times | first=Eric | last=Pace | title=R.E. Schreiber, 88, Nuclear Bomb Physicist | date=31 December 1998}}</ref><ref name=pfiles>{{cite book|last=Welsome|first=Eileen|title=The plutonium files|year=1999|publisher=Delacorte Press|location=New York|isbn=0385314027|url=https://archive.org/details/plutoniumfiles00wels_0/page/184|page=[https://archive.org/details/plutoniumfiles00wels_0/page/184 184]}}</ref><ref name=":0">{{Cite news|url=https://www.newspapers.com/clip/4814605/four_injured_men_out_of_hospital_louis/|title=Four injured men out of hospital, Louis Slotin (radiation exposure) (1948) – on Newspapers.com|newspaper=Albuquerque Journal|date=26 May 1946|page=4|access-date=3 April 2016}}</ref> By 25 May 1946, four of these seven men had been discharged from the hospital. The [[United States Army]] physician responsible for the Los Alamos base hospital, [[Captain (United States)|Captain]] Paul Hageman, said that Slotin's, Graves', Kline's and Young's "immediate condition is satisfactory."<ref name=":0" />

==== Slotin's death ====
Despite intensive medical care and offers from numerous volunteers to donate blood for [[blood transfusion|transfusions]], Slotin's condition was incurable.<ref name="zeilig22" /> He called his parents and they were flown at Army expense from Winnipeg to be with him. They arrived on the fourth day after the incident, and by the fifth day his condition started to deteriorate rapidly.<ref name="New Yorker"/>

Over the next four days, Slotin suffered an "agonizing sequence of radiation-induced traumas", including severe [[diarrhea]], reduced urine output, swollen hands, [[erythema]], "massive [[blister]]s on his hands and forearms", [[intestinal paralysis]] and [[gangrene]]. He had internal [[radiation burns]] throughout his body, which one medical expert described as a "three-dimensional sunburn." By the seventh day, he was experiencing periods of "mental confusion." His lips turned blue and he was put in an [[oxygen tent]]. He ultimately experienced "a total disintegration of bodily functions" and slipped into a [[coma]].<ref name="New Yorker"/><ref>{{cite book | editor= Chris Austill | title=Decision-Making in the Nuclear Age | publisher= Halcyon Press| location=[[Weston, Massachusetts]] | year = 1983 |oclc=9778139 | page= 353}}</ref> Slotin died at 11 a.m. on 30 May, in the presence of his parents.<ref>{{Cite news|url=https://www.newspapers.com/clip/4814517/atomic_injuries_fatal_to_scientist/|title=Atomic injuries fatal to scientist Louis Slotin (radiation) (1948) – on Newspapers.com|newspaper=Albuquerque Journal|date=31 May 1946|page=1|access-date=3 April 2016}}</ref> He was buried in the [[Shaarey Zedek Cemetery (Winnipeg)|Shaarey Zedek Cemetery]] in Winnipeg on 2 June 1946.<ref name="zeilig22" />

==== Other injuries and death ====
Graves, Kline and Young remained hospitalized after Slotin's death.<ref>{{Cite news|url=https://www.newspapers.com/clip/4814567/atomic_injuries_fatal_to_scientist/|title=Atomic injuries fatal to scientist, Louis Slotin (radiation) (1948) 2 – on Newspapers.com|newspaper=Albuquerque Journal|date=31 May 1946|page=2|access-date=3 April 2016}}</ref> Graves, who was standing the closest to Slotin, also developed [[acute radiation sickness]] and was hospitalized for several weeks. He survived, although he lived with chronic neurological and vision problems. Young also suffered from acute radiation syndrome, but recovered. By 28 January 1948 Graves, Kline and Perlman sought compensation for damages suffered during the incident. Graves settled his claim for $3,500 (or about ${{Inflation|US|3500|1946|r=-2|disp=out|fmt=c}} today,{{Inflation-fn|US}} adjusted for inflation).<ref>{{Cite news|url=https://www.newspapers.com/clip/4814954/kline_graves_perlman_seek/|title=Kline, Graves & Perlman seek compensation for radiation exposure (1948) – on Newspapers.com|newspaper=Albuquerque Journal|date=29 January 1948|page=5|access-date=3 April 2016}}</ref>

Three of the observers eventually died of conditions that are known to be promoted by radiation: Graves of a [[heart attack]] twenty years later at age 55,<ref>{{cite news|work=[[The New York Times]]|url=https://www.nytimes.com/1989/11/19/magazine/america-s-radiation-victims-the-hidden-files.html?scp=1&sq=America%27s+Radiation+Victims%3A+The+Hidden+Files&st=cse&pagewanted=print|date=19 November 1989|title=America's Radiation Victims: The Hidden Files|author=Clifford T. Honicker}}</ref> Cieslicki of [[acute myeloid leukemia]] nineteen years later at age 42, and Young of [[aplastic anemia]] and bacterial infection of the heart lining, twenty-nine years later, at age 83. Some of the deaths may have been a consequence of the incident. Louis Hempelman, M.D., a consultant to the Los Alamos Scientific Laboratory, believed that it is not possible to establish a causal relation between the incident and the specifics of the death from such a small sample.<ref name=hempelman /> He stated this opinion in a publicly available report that included personal medical information which he had previously declined to release to Cieslicki during the final stages of his illness.

==== Disposal of core ====
The core involved was intended to be used in the [[Operation Crossroads#Test Able|Able detonation]], during the [[Operation Crossroads|Crossroads]] series of nuclear weapons testing. Slotin's experiment was said to be the last conducted before the core's detonation and was intended to be the final demonstration of its ability to go critical.<ref name="Millerp69">{{cite book|last=Miller|first=Richard L.|title=Under the Cloud: The Decades of Nuclear Testing|publisher=Two Sixty Press|location=[[The Woodlands, Texas]]|year=1991|isbn=0029216206|oclc=13333365|pages=[https://archive.org/details/underclouddec00mill/page/69 69, 77]|url=https://archive.org/details/underclouddec00mill/page/69}}</ref> After the accident, it needed time to cool. It was therefore rescheduled for the third test of the series, provisionally named ''Charlie'', but this was cancelled due to the unexpected level of radioactivity after the underwater ''Baker'' test and the inability to decontaminate the target warships. The core was eventually melted down and its material reused in a later core.<ref name="New Yorker">{{cite news | newspaper=[[The New Yorker]] | last=Wellerstein| first=Alex| title=The Demon Core and the Strange Death of Louis Slotin| url=https://www.newyorker.com/tech/elements/demon-core-the-strange-death-of-louis-slotin?intcid=mod-latest| date=21 May 2016 |access-date=22 May 2014}}</ref>

=== Radiation dosage ===
[[File:Slotin criticality map.png|thumb|right|300px|A sketch used by doctors to determine the amount of radiation to which each person in the room had been exposed during the excursion]]
[[File:Slotin criticality drawing.jpg|thumb|right|300px|A drawing based on the above sketch.]]
The radiation doses received in these two accidents are not known with any accuracy. A large part of the dose was due to neutron radiation, which could not be measured by dosimetry equipment of the day. The available film badges were not worn by personnel during the accident, and badges that were supposed to be planted under tables in case of disasters like these were not found. Disaster badges hung on the walls provided some useful data about gamma radiation.<ref name=hoffman>{{cite report|last=Hoffman|first=Joseph G.|title=Radiation Doses in the Pajarito Accident of May 21, 1946|date=26 May 1948|url=https://www.orau.org/ptp/Library/accidents/pajarito.pdf|access-date=30 May 2012|publisher=Los Alamos Scientific Laboratory|id=LA-687|display-authors=etal}}</ref>

A "tentative" estimate of the doses involved was made in 1948, based on dozens of assumptions, some of which are now known to be incorrect. In the absence of personal dosimetry badges, the study authors relied on measurements of [[sodium]] activation in the victims' blood and urine samples as their primary source of data. This activation would have been caused by neutron radiation, but they converted all doses to [[equivalent dose]]s of gamma or X-ray radiation. They concluded that Daghlian and Slotin had probably received doses equivalent to {{convert|290|rem|Sv}} and {{convert|880|rem|Sv}}, respectively, of gamma rays. Minimum and maximum estimates varied from about 50% to 200% of these values. The authors also calculated doses equivalent to a mix of soft 80&nbsp;keV X-rays and gamma rays, which they believed gave a more realistic picture of the exposure than the gamma equivalent. In this model, the equivalent X-ray doses were much higher, but would be concentrated in the tissues facing the source, whereas the gamma component penetrated the whole body. Slotin's equivalent dose was estimated to be 1930&nbsp;R (roentgen) of X-ray with 114&nbsp;R of gamma, while Daghlian's equivalent dose was estimated to be 480&nbsp;R of X-ray with 110&nbsp;R of gamma.<ref name=hoffman />  Five hundred [[roentgen equivalent man]] (rem) is usually a fatal exposure for humans.<ref name="New Yorker"/>

In modern times, dosimetry is done very differently. Equivalent doses would not be reported in roentgen; they would be calculated with different weighting factors, and they are not considered as relevant to acute radiation syndrome as [[absorbed dose]]s. Recent documents have made various interpretations of Slotin's dose, ranging from {{convert|287|rad|Gy}}<ref name=ziegler /> to {{convert|21|Sv|rem}}.<ref name="la-13638">{{cite web| title = LA-13638 A Review of Criticality Accidents| publisher =Los Alamos National Laboratory |date=May 2000 | url = https://www.orau.org/ptp/Library/accidents/la-13638.pdf| pages=74–76| access-date = 5 December 2007 }}</ref> Based on citations and supporting reasoning, the most reliable estimate may be a 1978 Los Alamos memo which suggested 10&nbsp;[[gray (unit)|Gy]](n) + 1.14 Gy(γ) for Slotin and 2 Gy(n) + 1.1 Gy(γ) for Daghlian.<ref>{{cite report|last=Lawrence|first=James N. P.|title=Internal Memorandum on Los Alamos Criticality Accidents, 1945–1946, Personnel Exposures|date=6 October 1978|publisher=Los Alamos Scientific Laboratory|id=H-l-78}}</ref> These doses are consistent with the symptoms they experienced.<ref name=hempelman />

== Legacy ==
After the accident, Los Alamos ended all hands-on critical assembly work. Subsequent criticality testing of fissile cores was done with remotely controlled machines, such as the "[[Godiva device|Godiva]]" series, with the operator located a safe distance away to prevent harm in case of accidents.<ref>{{cite book | last= Jungk | first= Robert | author-link= Robert Jungk | title= [[Brighter than a Thousand Suns: A Personal History of the Atomic Scientists|Brighter than a Thousand Suns]] | publisher= Harcourt Brace | year= 1958 | location= New York | isbn= 0156141507 | oclc= 181321 | page= [https://archive.org/details/brighterthanthou00jung_0/page/302 302] }}</ref>

On 14 June 1946, the associate editor of the ''Los Alamos Times'', Thomas P. Ashlock, penned a poem entitled "Slotin – A Tribute":

{{blockquote|
<poem>
May God receive you, great-souled scientist!
While you were with us, even strangers knew
The breadth and lofty stature of your mind
Twas only in the crucible of death
We saw at last your noble heart revealed.<ref name="zeilig22" />
</poem>
}}

The official story released at the time was that Slotin, by quickly removing the upper hemisphere, was a hero for ending the reaction and protecting seven other observers in the room: "Dr. Slotin's quick reaction at the immediate risk of his own life prevented a more serious development of the experiment which would certainly have resulted in the death of the seven men working with him, as well as serious injury to others in the general vicinity."<ref name="zeilig22" /> This interpretation of events was endorsed at the time by Graves, who stood closest to Slotin when the accident occurred.<ref name=pfiles /> Graves, like Slotin, had previously displayed a low concern for nuclear safety and later alleged that [[fallout]] risks were "concocted in the minds of weak malingerers."<ref name=pfiles /> Schreiber, another witness to the accident, spoke out publicly decades later, arguing that Slotin was using improper and unsafe procedures, endangering the others in the lab along with himself. Robert B. Brode had reported hearsay to that effect back in 1946.<ref name="zeilig22" />

Slotin's accident is echoed in the 1947 film ''[[The Beginning or the End]]'', in which a scientist assembling the bomb destined for Hiroshima dies after coming into contact with radioactive material.{{refn|{{cite book |last=Jungk |first=Robert |authorlink=Robert Jungk |title=Brighter than a Thousand Suns |url=https://archive.org/details/brighterthanthou00jung_0 |publisher=Harcourt Brace |year=1958 |isbn=978-0156141505 |pages=194–196}} }}
It was recounted in [[Dexter Masters]]' 1955 novel ''The Accident'', a fictional account of the last few days of the life of a nuclear scientist suffering from [[radiation poisoning]].<ref>{{cite news |last= Schonberg |first= Harold C |title= Dexter Masters, 80, British Editor; Warned of Perils of Atomic Age |url=https://query.nytimes.com/gst/fullpage.html?res=950DE1D91E38F935A35752C0A96F948260 |work=[[The New York Times]]|date=6 January 1989 |access-date=26 November 2007 }}</ref><ref>{{cite book | first1= Lawrence |last1=Badash |first2=Joseph O. |last2=Hirschfelder |first3=Herbert P. |last3=Broida| title=Reminiscences of Los Alamos, 1943–1945 | publisher= [[D. Reidel Publishing Company]]| location=Dordrecht, Netherlands | year = 1980 |isbn=9027710988 | pages= 98–99}}</ref> Depictions of the criticality incident include the 1989 film ''[[Fat Man and Little Boy (film)|Fat Man and Little Boy]]'', in which [[John Cusack]] plays a fictional character named Michael Merriman based on Slotin, and the ''Louis Slotin Sonata'', a 2001 off-Broadway play directed by David P. Moore.<ref name="TST">{{cite news |last= Berson |first= Misha |title=Louis Slotin Sonata: Tumultuous and bubbling drama |url=http://seattletimes.nwsource.com/html/theaterarts/2003268048_slotin21.html |work=The Seattle Times |date=21 September 2006 |access-date=16 November 2007 }}</ref><ref>Weber, Bruce. [http://theater.nytimes.com/mem/theater/treview.html?id=1077011430626 A Scientist's Tragic Hubris Attains Critical Mass Onstage (theatre review)], ''[[The New York Times]]'', 10 April 2001.</ref>

In 1948, Slotin's colleagues at Los Alamos and the University of Chicago initiated the ''Louis A. Slotin Memorial Fund'' for lectures on physics given by distinguished scientists such as [[Robert Oppenheimer]], [[Luis Walter Alvarez]], [[Hans Bethe]]. The memorial fund lasted until 1962.<ref name="zeilig22" /> In 2002, an [[asteroid]] discovered in 1995 was named [[12423 Slotin]] in his honour.<ref>{{cite web |url=http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=12423+Slotin |title=12423 Slotin (1995 UQ16) |publisher=[[Jet Propulsion Laboratory]] |access-date=8 May 2012 }}</ref>

In 2025, Louis' experiment and accident are featured in "The Demon Core" a short film by [[J. Zachary Thurman]].<ref>https://scienceandfilm.org/projects/871/the-demon-core</ref>

=== Dollar unit of reactivity ===
According to [[Alvin M. Weinberg|Weinberg]] and Wigner,<ref>[[Alvin M. Weinberg]] and Eugene P. Wigner. ''The Physical Theory of Neutron Chain Reactors''. Chicago: University of Chicago Press, 1958. Page 595.</ref> Slotin was the first to propose the name [[dollar (reactivity)|dollar]] for the interval of reactivity between delayed and [[prompt critical]]ity; 0 is the point of self-sustaining chain reaction, a dollar is the point at which slowly released, delayed neutrons are no longer required to support chain reaction, and enters the domain called "prompt critical". Stable nuclear reactors operate between 0 and a dollar; excursions and nuclear explosives operate above a dollar. The hundredth part of a dollar is called a [[cent (reactivity)|cent]].<ref>Hugh C. Paxton: ''A History of Critical Experiments at Pajarito Site''. Los Alamos Document [https://www.atomictraveler.com/LANLPajarito.pdf LA-9685-H], 1983.</ref>  When speaking of purely prompt critical events, some users refer to cents "over critical" as a relative unit.<ref>{{Cite web |last=Thomas P. Mclaughlin, Vladimir V. Frolov |date=May 2000 |title=la-13638.pdf |url=https://orau.org/health-physics-museum/files/library/accidents/la-13638.pdf |url-status=live |archive-url=https://web.archive.org/web/20240324232918/https://orau.org/health-physics-museum/files/library/accidents/la-13638.pdf |archive-date=24 March 2024 |access-date=4 July 2004 |website=ORAU - Museum of Radiation and Radioactivity}}</ref>

== Notes ==
{{reflist|group=notes}}

== References ==
{{reflist|30em}}

== External links ==
{{Commons category}}
{{Spoken Wikipedia|slotin.ogg|date=21 January 2008}}
* [https://web.archive.org/web/20080516101332/http://www.mphpa.org/classic/FH/LA/Louis_Slotin_1.htm Louis P. Slotin] – The Manhattan Project Heritage Preservation Association
* [http://www.science.ca/scientists/scientistprofile.php?pID=290 Louis Slotin, profile] – GCS Research Society
* [https://cns-snc.ca/media/history/pioneers/slotin/slotin.html The Secret Life of Louis Slotin] {{Webarchive|url=https://web.archive.org/web/20211127171622/https://cns-snc.ca/media/history/pioneers/slotin/slotin.html |date=27 November 2021 }} – Canadian Nuclear Society
* {{find a Grave|22319390}}
* [https://www.lib.uchicago.edu/e/scrc/findingaids/view.php?eadid=ICU.SPCL.SLOTIN Guide to the Louis Slotin Memorial Fund Records 1946–1962] at the [https://www.lib.uchicago.edu/scrc/ University of Chicago Special Collections Research Center]

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