Editing Trinity (nuclear test) (section)

===The bomb===
{{See also|Nuclear weapon design#Implosion-type weapon}}
[[File:Trinity tower.jpg|thumb|right|upright=1|The {{convert|30|m|adj=on|-2}} "shot tower" constructed for the test]]
The term "[[gadget]]"—a laboratory euphemism for a bomb<ref>{{cite web |url=https://www.atomicheritage.org/profile/robert-f-christy |title=Robert F. Christy |publisher=Atomic Heritage Foundation |access-date=November 8, 2014 |archive-date=October 13, 2014 |archive-url=https://web.archive.org/web/20141013203837/http://www.atomicheritage.org/profile/robert-f-christy |url-status=live }}</ref>—gave the laboratory's weapon physics division, "G Division", its name in August 1944.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=307–308}} At that time it did not refer specifically to the Trinity Test device as that had yet to be developed,{{sfn|Hawkins|Truslow|Smith|1961|p=228}} but once it was, it became the laboratory code name.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=307–308}} The Trinity bomb was officially a Y-1561 device, as was the Fat Man used later in the bombing of Nagasaki. The two were very similar, though the Trinity bomb lacked fuzing and external ballistic casing. The bombs were still under development, and small changes continued to be made to the Fat Man design.{{sfn|Coster-Mullen|2012|pp=47–53}}

To keep the design as simple as possible, a nearly solid spherical core was chosen rather than a hollow one, although calculations showed that a hollow core would be more efficient in its use of plutonium.<ref name="Christy">{{cite web |url=http://www.webofstories.com/play/robert.christy/8 |last=Christy |first=Robert |author-link=Robert Christy |title=Constructing the Nagasaki Atomic Bomb |publisher=Web of Stories |access-date=October 12, 2014 |url-status=dead |archive-url=https://web.archive.org/web/20141010073928/http://www.webofstories.com/play/robert.christy/8 |archive-date=October 10, 2014 }}</ref>{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=293}} The core was compressed to [[prompt critical|prompt super-criticality]] by the implosion generated by the high explosive lens. This design became known as a "Christy Core"{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=270–271, 293–294}} or "[[Pit (nuclear weapon)#Christy pits|Christy pit]]" after physicist [[Robert F. Christy]], who made the solid pit design a reality after it was initially proposed by [[Edward Teller]].<ref name="Christy"/><ref>{{cite web |publisher=Restricted Data: The Nuclear Secrecy Blog |last=Wellerstein |first=Alex |title=Christy's Gadget: Reflections on a death |url=http://blog.nuclearsecrecy.com/2012/10/05/christys-gadget/ |access-date=October 7, 2014 |archive-date=October 11, 2014 |archive-url=https://web.archive.org/web/20141011050606/http://blog.nuclearsecrecy.com/2012/10/05/christys-gadget/ |url-status=live }}</ref><ref>{{cite web |url=https://www.webofstories.com/play/hans.bethe/94 |title=Hans Bethe 94 – Help from the British, and the 'Christy Gadget' |publisher=Web of Stories |access-date=October 12, 2014 |archive-date=April 4, 2020 |archive-url=https://web.archive.org/web/20200404220148/http://www.webofstories.com/play/hans.bethe/94 |url-status=live }}</ref>

Of the several [[allotropes of plutonium]], the metallurgists preferred the malleable δ ([[Delta (letter)|delta]]) [[Phase (matter)|phase]]. This was stabilized at room temperature by alloying it with 5% [[gallium]].<ref name="neim">{{cite web |year=2005 |title=The drama of plutonium |url=http://www.neimagazine.com/story.asp?storyCode=2029280 |url-status=dead |archive-url=https://web.archive.org/web/20100915115554/http://www.neimagazine.com/story.asp?storyCode=2029280 |archive-date=2010-09-15 |access-date=2010-01-25 |publisher=Nuclear Engineering International}}</ref> Two equal hemispheres of plutonium-gallium alloy were plated with silver,{{sfn|Coster-Mullen|2012|pp=47–53}}{{sfn|Hawkins|Truslow|Smith|1961|pp=256–257}} and designated by serial numbers HS-1 and HS-2.<ref>{{cite web |publisher=Restricted Data: The Nuclear Secrecy Blog |last=Wellerstein |first=Alex |title=The third core's revenge |url=http://blog.nuclearsecrecy.com/2013/08/16/the-third-cores-revenge/ |access-date=April 4, 2014 |archive-date=April 7, 2014 |archive-url=https://web.archive.org/web/20140407081649/http://blog.nuclearsecrecy.com/2013/08/16/the-third-cores-revenge/ |url-status=live }}</ref> The {{convert|6.19|kg|adj=on}} radioactive core generated 15 W of heat, which warmed it up to about {{convert|100|to|110|F|C}},{{sfn|Coster-Mullen|2012|pp=47–53}} and the silver plating developed blisters that had to be filed down and covered with gold foil; later cores were plated with [[nickel]] instead.<ref>{{cite web |title=Cyril S. Smith's Interview |url=https://www.manhattanprojectvoices.org/oral-histories/cyril-s-smiths-interview |last1=Smith |first1=Cyril S. |last2=Sanger |first2=S.L. |publisher=The Voices of the Manhattan Project and National Museum of Nuclear Science and History |year=1986 |access-date=March 29, 2020 |archive-date=March 29, 2020 |archive-url=https://web.archive.org/web/20200329120705/https://www.manhattanprojectvoices.org/oral-histories/cyril-s-smiths-interview |url-status=live }}</ref>
[[File:Fat Man design model.png|thumb|left|Basic nuclear components of the bomb. The uranium slug containing the plutonium sphere was inserted late in the assembly process.]]
A trial assembly of the bomb, without active components or explosive lenses, was carried out by the bomb assembly team headed by [[Norris Bradbury]] at Los Alamos on July 3. It was driven to Trinity and back. A set of explosive lenses arrived on July 7, followed by a second set on July 10. Each was examined by Bradbury and Kistiakowsky, and the best ones were selected for use.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=365}} The remainder were handed over to [[Edward Creutz]], who conducted a test detonation at Pajarito Canyon near Los Alamos without nuclear material.{{sfn|Rhodes|1986|p=657}} Magnetic measurements from this test suggested that the implosion might be insufficiently simultaneous and the bomb would fail. Bethe worked through the night to assess the results and reported that they were consistent with a perfect explosion.{{sfn|Rhodes|1986|pp=661–663}}

Assembly of the nuclear capsule began on July 13 at the McDonald Ranch House, where the master bedroom had been turned into a [[clean room]]. The polonium-beryllium [[Urchin (detonator)|"Urchin" initiator]] was assembled, and [[Louis Slotin]] placed it inside the two hemispheres of the plutonium core. [[Cyril Stanley Smith|Cyril Smith]] then placed the core in the natural uranium [[tamper (nuclear weapon)|tamper]] plug, or "slug". Air gaps were filled with {{convert|0.5|mil|adj=on}} gold foil, and the two halves of the plug were held together with uranium washers and screws which fit smoothly into the domed ends of the plug.{{sfn|Coster-Mullen|2012|pp=56–57}}
[[File:Trinity device readied.jpg|thumb|right|The bomb being unloaded at the base of the tower for the final assembly]]

To better understand the likely effect of a bomb dropped from a plane and detonated in air, and generate less nuclear fallout, the bomb was to be detonated atop a {{convert|100|ft|adj=on}} steel tower.{{sfn|Rhodes|1986|p=654}} The bomb was driven to the base of the tower, where a temporary [[eye bolt]] was screwed into the {{convert|105|lb|adj=on}} capsule and a [[Hoist (device)|chain hoist]] was used to lower the capsule into the bomb. As the capsule entered the hole in the uranium tamper, it stuck. [[Robert Bacher]] realized that the heat from the plutonium core had caused the capsule to expand, while the explosives assembly with the tamper had cooled during the night in the desert. By leaving the capsule in contact with the tamper, the temperatures equalized and, in a few minutes, the capsule had slipped completely into the tamper.{{sfn|Coster-Mullen|2012|pp=49–50}} The eye bolt was then removed from the capsule and replaced with a threaded uranium plug, a boron disk was placed on top of the capsule (to complete the thin spherical shell of plastic boron around the tamper), an aluminum plug was screwed into the hole in the pusher (aluminum shell surrounding the tamper), and the two remaining high explosive lenses were installed. Finally, the upper [[Duralumin|Dural]] polar cap was bolted into place.{{sfn|Coster-Mullen|2012|p=58}} The assembly of active material and high explosives was finished at 17:45 hours on 13 July.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=370}}

The gadget was hoisted to the top of the tower. The tower stood on four legs extending {{convert|20|ft}} into the ground, with concrete footings. Atop it was an oak platform and a [[corrugated iron]] shack open to the west. The gadget was hauled up with an electric winch.{{sfn|Rhodes|1986|p=654}} A truckload of mattresses was placed underneath in case the cable broke and the gadget fell.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=368–370}}{{efn|The mattresses would not have protected the gadget, but they helped the men to feel better.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|p=483}}}} A crew then attached each of the 32 Model 1773 [[Exploding-bridgewire detonator|EBW]] detonators. Full assembly of the bomb was completed by 17:00 on July 14.{{sfn|Coster-Mullen|2012|p=314}} The seven-man arming party, consisting of Bainbridge, Kistiakowsky, [[Joseph McKibben]] and four soldiers including Lieutenant Bush, drove out to the tower to perform the final arming shortly after 22:00 on July 15.{{sfn|Hoddeson|Henriksen|Meade|Westfall|1993|pp=368–370}}