Editing Neutron diffraction (section)

== History ==
=== Discovery of the neutron ===
{{main|Neutron#Discovery}}

In 1921, American chemist and physicist [[William Draper Harkins|William D. Harkins]] introduced the term "[[neutron]]" while studying [[atomic structure]] and [[Nuclear reaction|nuclear reactions]]. He proposed the existence of a neutral particle within the [[atomic nucleus]], though there was no experimental evidence for it at the time.<ref>{{Cite journal |last=Harkins |first=William D. |date=1917 |title=The evolution of the elements and the stability of complex atoms. A new periodic system which shows a relation between the abundance of the elements and structure of the nuclei of atoms. |url=https://pubs.acs.org/doi/abs/10.1021/ja02250a002 |journal=Journal of the American Chemical Society |language=en |volume=39 |issue=5 |pages=856–879 |doi=10.1021/ja02250a002 |issn=0002-7863|url-access=subscription }}</ref> In 1932, British physicist [[James Chadwick]] provided experimental proof of the neutron's existence. His discovery confirmed the presence of this neutral [[subatomic particle]], earning him the [[Nobel Prize in Physics]] in 1935. Chadwick's research was influenced by earlier work from [[Irène Joliot-Curie|Irène]] and [[Frédéric Joliot-Curie]], who had detected unexplained neutral [[radiation]] but had not recognized it as a distinct particle.<ref>{{Cite journal |date=1932 |title=The existence of a neutron |url=https://royalsocietypublishing.org/doi/10.1098/rspa.1932.0112 |journal=Proceedings of the Royal Society of London. Series A, Containing Papers of a Mathematical and Physical Character |language=en |volume=136 |issue=830 |pages=692–708 |doi=10.1098/rspa.1932.0112 |bibcode=1932RSPSA.136..692C |issn=0950-1207 |last1=Chadwick |first1=J. |doi-access=free }}</ref> Neutrons are subatomic particles that exist in the nucleus of the atom, it has higher mass than protons but no electrical charge.

In the 1930s [[Enrico Fermi]] and colleagues gave theoretical contributions establishing the foundation of [[neutron scattering]]. Fermi developed a framework to understand how neutrons interact with atomic nuclei.<ref>{{Cite journal |last1=Amaldi |first1=E. |last2=Fermi |first2=E. |date=1936-11-15 |title=On the Absorption and the Diffusion of Slow Neutrons |url=https://link.aps.org/doi/10.1103/PhysRev.50.899 |journal=Physical Review |language=en |volume=50 |issue=10 |pages=899–928 |doi=10.1103/PhysRev.50.899 |bibcode=1936PhRv...50..899A |issn=0031-899X|url-access=subscription }}</ref>

===Early diffraction work===
Diffraction was first observed in 1936<ref>{{Cite journal |last1=Mason |first1=T. E. |last2=Gawne |first2=T. J. |last3=Nagler |first3=S. E. |last4=Nestor |first4=M. B. |last5=Carpenter |first5=J. M. |date=2013-01-01 |title=The early development of neutron diffraction: science in the wings of the Manhattan Project |url=https://journals.iucr.org/a/issues/2013/01/00/wl5168/index.html |journal=Acta Crystallographica Section A: Foundations of Crystallography |language=en |volume=69 |issue=1 |pages=37–44 |doi=10.1107/S0108767312036021 |issn=0108-7673 |pmc=3526866 |pmid=23250059}}</ref> by two groups, von Halban and Preiswerk <ref>{{Cite journal |last=H |first=Von Halban |date=1936 |title=Preuve Experimentale de la Diffraction des Neutrons |url=https://cir.nii.ac.jp/crid/1571135650793736832 |journal=Acad. Sci. Paris |volume=203 |pages=73–75}}</ref> and by Mitchell and Powers.<ref>{{Cite journal |last1=Mitchell |first1=Dana P. |last2=Powers |first2=Philip N. |date=1936-09-01 |title=Bragg Reflection of Slow Neutrons |url=https://journals.aps.org/pr/abstract/10.1103/PhysRev.50.486.2 |journal=Physical Review |volume=50 |issue=5 |pages=486–487 |doi=10.1103/PhysRev.50.486.2|bibcode=1936PhRv...50..486M |url-access=subscription }}</ref> In 1944, [[Ernest O. Wollan]], with a background in X-ray scattering from his PhD work<ref name="PhysicsTodayObit">
{{cite journal |last1=Snell |first1=A. H. |last2=Wilkinson |first2=M. K. |last3=Koehler |first3=W. C. |year=1984 |title=Ernest Omar Wollan |journal=[[Physics Today]] |volume=37 |issue=11 |page=120 |bibcode=1984PhT....37k.120S |doi=10.1063/1.2915947 |doi-access=free}}</ref> under [[Arthur Compton]], recognized the potential for applying thermal neutrons from the newly operational [[X-10 Graphite Reactor|X-10 nuclear reactor]] to [[crystallography]]. Joined by [[Clifford G. Shull]] they developed<ref>
{{cite book |last=Shull |first=C. G. |title=Nobel Lectures, Physics 1991–1995 |date=1997 |publisher=[[World Scientific Publishing]] |editor-last=Ekspong |editor-first=G. |pages=145–154 |chapter=Early Development of Neutron Scattering |chapter-url=https://www.nobelprize.org/nobel_prizes/physics/laureates/1994/shull-lecture.pdf |archive-url=https://web.archive.org/web/20170519024556/https://www.nobelprize.org/nobel_prizes/physics/laureates/1994/shull-lecture.pdf |archive-date=2017-05-19}}</ref> neutron diffraction throughout the 1940s. 

Neutron diffraction experiments were carried out in 1945 by [[Ernest O. Wollan]] using the Graphite Reactor at [[Oak Ridge National Laboratory|Oak Ridge]]. He was joined shortly thereafter (June 1946)<ref>{{cite journal |last=Shull |first=Clifford G. |date=1995-10-01 |title=Early development of neutron scattering |journal=Reviews of Modern Physics |publisher=American Physical Society (APS) |volume=67 |issue=4 |pages=753–757 |bibcode=1995RvMP...67..753S |doi=10.1103/revmodphys.67.753 |issn=0034-6861}}</ref> by [[Clifford Glenwood Shull|Clifford Shull]], and together they established the basic principles of the technique, and applied it successfully to many different materials, addressing problems like the structure of ice and the microscopic arrangements of magnetic moments in materials. For this achievement, Shull was awarded one half of the 1994 [[Nobel Prize in Physics]]. (Wollan died in 1984). (The other half of the 1994 Nobel Prize for Physics went to [[Bertram Brockhouse|Bert Brockhouse]] for development of the inelastic scattering technique at the [[Chalk River Laboratories|Chalk River facility]] of [[Atomic Energy of Canada|AECL]]. This also involved the invention of the triple axis spectrometer).

=== 1950-60s === 
The development of neutron sources such as [[Nuclear reactor|reactors]] and [[Spallation source|spallation sources]] emerged. This allowed high-intensity [[Neutron beam activation analysis|neutron beams]], enabling advanced scattering experiments. Notably, the [[High Flux Isotope Reactor|high flux isotope reactor]] (HFIR) at Oak Ridge and Institut Laue Langevin (ILL) in Grenoble, France, emerged as key institutions for neutron scattering studies.<ref>{{Cite journal |last=Helliwell |first=John |date=2012 |title=My life in diffraction: an autobiographical review by George E. Bacon |url=http://www.tandfonline.com/doi/abs/10.1080/0889311X.2012.666976 |journal=Crystallography Reviews |language=en |volume=18 |issue=2 |pages=97–180 |doi=10.1080/0889311X.2012.666976 |bibcode=2012CryRv..18...97H |issn=0889-311X|url-access=subscription }}</ref>

===1970-80s === 
This period saw major advancements in neutron scattering techniques by developing techniques to explore different aspects of material science, structure and behaviour.<ref name="Lovesey-2003">{{Cite book |last=Lovesey |first=Stephen W. |title=Theory of neutron scattering from condensed matter. 2: Polarization effects and magnetic scattering |date=2003 |publisher=Clarendon Pr |isbn=978-0-19-852029-0 |edition=Repr |series=International series of monographs on physics |location=Oxford}}</ref>

[[Small-angle neutron scattering|Small angle neutron scattering (SANS)]]:'' Used to investigate large-scale structural features in materials. The works of Glatter and Kratky also helped in the advancements of this method, though it was primarily developed for [[X-ray|X-rays]].<ref name="Lovesey-2003" /> ''

[[Inelastic neutron scattering|Inelastic neutron scattering (INS)]]'': Provides insights into the dynamic process at the microscopic level. Majorly used to examine atomic and molecular motions.<ref name="Lovesey-2003" />''
[[File:Wollan_and_Shull_1949.jpg|thumb|In 1949, Ernest Wollan and Clifford Shull conducted experiments using a double-crystal [[neutron spectrometer]] positioned on the southern side of the ORNL graphite reactor to collect data. ]]

===1990-present === 
Recent advancements focus on improved sources, using sophisticated detectors and enhanced computational techniques. Spallation sources have been developed at SNS (Spallation Neutron Source) in the U.S. and [[ISIS Neutron and Muon Source|ISIS Neutron]] and Muon Source in the U.K., which can generate pulsed neutron beams for [[Time of flight|time-of-flight]] experiments. [[Neutron imaging]] and [[reflectometry]]<nowiki/>were also developed, which are powerful tools to analyse surfaces, interfaces and thin film structures, thus providing valuable insights into the material properties.