Editing Americium (section)

==Applications==
{{Multiple image|direction=vertical|align=right|image1=Residential smoke detector.jpg|image2=InsideSmokeDetector.jpg|width=200|caption2=Outside and inside view of an americium-based smoke detector}}

===Ionization-type smoke detector===
{{Main|Smoke detector#Ionization}}

Americium is used in the most common type of household [[smoke detector]], which uses <sup>241</sup>Am in the form of americium dioxide as its source of [[ionizing radiation]].<ref>{{citation |url=http://www.uic.com.au/nip35.htm |archive-url=http://webarchive.loc.gov/all/20020911070229/http%3A//www%2Euic%2Ecom%2Eau/nip35%2Ehtm |archive-date= 11 September 2002 |title=Smoke Detectors and Americium |work=Nuclear Issues Briefing Paper |volume=35 |date=May 2002 |access-date=2015-08-26}}</ref> This isotope is preferred over <sup>226</sup>[[radium|Ra]] because it emits 5 times more alpha particles and relatively little harmful gamma radiation.

The amount of americium in a typical new smoke detector is 1&nbsp;[[microcurie]] (37&nbsp;[[kBq]]) or 0.29 [[microgram]]. This amount declines slowly as the americium decays into [[neptunium]]-237, a different transuranic element with a much longer half-life (about 2.14 million years). With its half-life of 432.2 years, the americium in a smoke detector includes about 3% [[neptunium]] after 19 years, and about 5% after 32 years. The radiation passes through an [[ionization chamber]], an air-filled space between two [[electrode]]s, and permits a small, constant [[Electric current|current]] between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and affects this current, triggering the alarm. Compared to the alternative optical smoke detector, the ionization smoke detector is cheaper and can detect particles which are too small to produce significant light scattering; however, it is more prone to [[Type I and type II errors|false alarms]].<ref>Residential Smoke Alarm Performance, Thomas Cleary. Building and Fire Research Laboratory, National Institute of Standards and Technology; UL Smoke and Fire Dynamics Seminar. November 2007</ref><ref name="NIST">Bukowski, R. W. ''et al''. (2007) [http://www.fire.nist.gov/bfrlpubs/fire07/art063.html Performance of Home Smoke Alarms Analysis of the Response of Several Available Technologies in Residential Fire Settings] {{Webarchive|url=https://web.archive.org/web/20100822192559/http://www.fire.nist.gov/bfrlpubs/fire07/art063.html |date=22 August 2010 }}, NIST Technical Note 1455-1</ref><ref>{{cite web |url=http://media.cns-snc.ca/pdf_doc/ecc/smoke_am241.pdf |archive-url=
https://web.archive.org/web/20160325003327/https://cns-snc.ca/media/uploads/teachers/smoke_am241.pdf|archive-date=2016-03-25|title = Smoke detectors and americium-241 fact sheet|publisher = Canadian Nuclear Society|access-date =31 August 2009}}</ref><ref>{{cite web|url=http://www.atsdr.cdc.gov/toxprofiles/tp156.pdf|title=Toxicological Profile For Americium|author=Gerberding, Julie Louise |publisher=[[United States Department of Health and Human Services]]/[[Agency for Toxic Substances and Disease Registry]]|access-date=29 August 2009|date=2004| archive-url= https://web.archive.org/web/20090906112953/http://www.atsdr.cdc.gov/toxprofiles/tp156.pdf| archive-date= 6 September 2009 | url-status= live}}</ref>

===Radionuclide===
As <sup>241</sup>Am has a roughly similar half-life to <sup>238</sup>Pu (432.2 years vs. 87 years), it has been proposed as an active element of [[radioisotope thermoelectric generator]]s, for example in spacecraft.<ref name="RTG">[http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf Basic elements of static RTGs] {{Webarchive|url=https://web.archive.org/web/20130215003518/http://fti.neep.wisc.edu/neep602/SPRING00/lecture5.pdf |date=15 February 2013 }}, G.L. Kulcinski, NEEP 602 Course Notes (Spring 2000), Nuclear Power in Space, University of Wisconsin Fusion Technology Institute (see last page)</ref> Although americium produces less heat and electricity – the power yield is 114.7&nbsp;mW/g for <sup>241</sup>Am and 6.31&nbsp;mW/g for <sup>243</sup>Am<ref name="res" /> (cf. 390&nbsp;mW/g for <sup>238</sup>Pu)<ref name="RTG" /> – and its radiation poses more threat to humans owing to neutron emission, the [[European Space Agency]] is considering using americium for its space probes.<ref>[http://www.spaceflightnow.com/news/n1007/09rtg/ Space agencies tackle waning plutonium stockpiles], Spaceflight now, 9 July 2010</ref>

Another proposed space-related application of americium is a fuel for space ships with nuclear propulsion. It relies on the very high rate of nuclear fission of <sup>242m</sup>Am, which can be maintained even in a micrometer-thick foil. Small thickness avoids the problem of self-absorption of emitted radiation. This problem is pertinent to uranium or plutonium rods, in which only surface layers provide alpha-particles.<ref name="rocket">{{cite web|title = Extremely Efficient Nuclear Fuel Could Take Man To Mars in Just Two Weeks|website = [[ScienceDaily]]|date = 3 January 2001|url = https://www.sciencedaily.com/releases/2001/01/010103073253.htm|access-date =22 November 2007| archive-url= https://web.archive.org/web/20071017120211/https://www.sciencedaily.com/releases/2001/01/010103073253.htm| archive-date= 17 October 2007 | url-status= live}}</ref><ref>{{cite conference|title = An americium-fueled gas core nuclear rocket|book-title = AIP Conf. Proc.|date = 10 January 1993|volume = 271|pages = 585–589|conference = Tenth symposium on space nuclear power and propulsion|author = Kammash, T. |doi = 10.1063/1.43073|display-authors=etal|url = https://deepblue.lib.umich.edu/bitstream/2027.42/87734/2/585_1.pdf|hdl = 2027.42/87734|hdl-access = free}}</ref> The fission products of <sup>242m</sup>Am can either directly propel the spaceship or they can heat a thrusting gas. They can also transfer their energy to a fluid and generate electricity through a [[magnetohydrodynamic generator]].<ref name="mprice">{{cite journal|last1=Ronen|first1=Y.|last2=Shwageraus|first2=E.|title=Ultra-thin 242mAm fuel elements in nuclear reactors|journal=Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment|volume=455|page=442|date=2000|doi=10.1016/S0168-9002(00)00506-4|issue=2|bibcode = 2000NIMPA.455..442R }}</ref>

One more proposal which utilizes the high nuclear fission rate of <sup>242m</sup>Am is a nuclear battery. Its design relies not on the energy of the emitted by americium alpha particles, but on their charge, that is the americium acts as the self-sustaining "cathode". A single 3.2&nbsp;kg <sup>242m</sup>Am charge of such battery could provide about 140&nbsp;kW of power over a period of 80 days.<ref>Genuth, Iddo [http://thefutureofthings.com/3015-americium-power-source/ Americium Power Source] {{webarchive|url=https://web.archive.org/web/20100507103250/http://thefutureofthings.com/articles.php?itemId=26%2F64%2F |date=7 May 2010 }}, The Future of Things, 3 October 2006, Retrieved 28 November 2010</ref> Even with all the potential benefits, the current applications of <sup>242m</sup>Am are as yet hindered by the scarcity and high price of this particular [[nuclear isomer]].<ref name="mprice" />

In 2019, researchers at the UK [[National Nuclear Laboratory]] and the [[University of Leicester]] demonstrated the use of heat generated by americium to illuminate a small light bulb. This technology could lead to systems to power missions with durations up to 400 years into [[interstellar space]], where solar panels do not function.<ref>{{cite web |title=UK scientists generate electricity from rare element to power future space missions |url=https://www.nnl.co.uk/2019/05/uk-scientists-generate-electricity-from-rare-element-to-power-future-space-missions/ |website=[[National Nuclear Laboratory]] |date=3 May 2019 |access-date=3 May 2019}}</ref><ref>{{cite magazine |author=<!--Staff writer(s); no by-line.--> |title=Rare element could power distant space missions |url=https://eandt.theiet.org/content/articles/2019/05/rare-element-could-power-far-flung-space-missions |magazine=E&T Engineering and Technology |publisher=[[Institution of Engineering and Technology]] |date=3 May 2019 |access-date=3 May 2019 }}</ref>

===Neutron source===
The oxide of <sup>241</sup>Am pressed with [[beryllium]] is an efficient [[neutron source]]. Here americium acts as the alpha source, and beryllium produces neutrons owing to its large cross-section for the (α,n) nuclear reaction:

: <chem>^{241}_{95}Am -> ^{237}_{93}Np + ^{4}_{2}He + \gamma</chem>

: <chem>^{9}_{4}Be + ^{4}_{2}He -> ^{12}_{6}C + ^{1}_{0}n + \gamma</chem>

The most widespread use of <sup>241</sup>AmBe neutron sources is a [[neutron probe]] – a device used to measure the quantity of water present in soil, as well as moisture/density for quality control in highway construction. <sup>241</sup>Am neutron sources are also used in well logging applications, as well as in [[neutron radiography]], tomography and other radiochemical investigations.<ref name="Binder" />

===Production of other elements===
Americium is a starting material for the production of other transuranic elements and [[transactinide]]s – for example, 82.7% of <sup>242</sup>Am decays to <sup>242</sup>Cm and 17.3% to <sup>242</sup>Pu. In the nuclear reactor, <sup>242</sup>Am is also up-converted by neutron capture to <sup>243</sup>Am and <sup>244</sup>Am, which transforms by β-decay to <sup>244</sup>Cm:

: <chem>^{243}_{95}Am ->[\ce{(n,\gamma)}] ^{244}_{95}Am ->[\beta^-][10.1 \ \ce{h}] ^{244}_{96}Cm</chem>

Irradiation of <sup>241</sup>Am by <sup>12</sup>C or <sup>22</sup>Ne ions yields the isotopes <sup>247</sup>Es ([[einsteinium]]) or <sup>260</sup>Db ([[dubnium]]), respectively.<ref name="Binder">{{cite book| author = Binder, Harry H. | title = Lexikon der chemischen Elemente: das Periodensystem in Fakten, Zahlen und Daten : mit 96 Abbildungen und vielen tabellarischen Zusammenstellungen| date = 1999| publisher = Hirzel| isbn = 978-3-7776-0736-8 }}</ref> Furthermore, the element [[berkelium]] (<sup>243</sup>Bk isotope) had been first intentionally produced and identified by bombarding <sup>241</sup>Am with alpha particles, in 1949, by the same Berkeley group, using the same 60-inch cyclotron. Similarly, [[nobelium]] was produced at the [[Joint Institute for Nuclear Research]], [[Dubna]], Russia, in 1965 in several reactions, one of which included irradiation of <sup>243</sup>Am with <sup>15</sup>N ions. Besides, one of the synthesis reactions for [[lawrencium]], discovered by scientists at Berkeley and Dubna, included bombardment of <sup>243</sup>Am with <sup>18</sup>O.<ref name="g1252" />

===Spectrometer===
Americium-241 has been used as a portable source of both gamma rays and alpha particles for a number of medical and industrial uses. The 59.5409&nbsp;keV gamma ray emissions from <sup>241</sup>Am in such sources can be used for indirect analysis of materials in [[radiography]] and [[X-ray fluorescence]] spectroscopy, as well as for quality control in fixed [[nuclear density gauge]]s and [[nuclear densometer]]s. For example, the element has been employed to gauge [[glass]] thickness to help create flat glass.<ref name="g1262" /> Americium-241 is also suitable for calibration of gamma-ray spectrometers in the low-energy range, since its spectrum consists of nearly a single peak and negligible Compton continuum (at least three orders of magnitude lower intensity).<ref>[http://www.nndc.bnl.gov/nudat2/indx_dec.jsp Nuclear Data Viewer 2.4] {{Webarchive|url=https://web.archive.org/web/20170601010723/http://www.nndc.bnl.gov/nudat2/indx_dec.jsp |date=1 June 2017 }}, NNDC</ref> Americium-241 gamma rays were also used to provide passive diagnosis of thyroid function. This medical application is however obsolete.