Editing Compton scattering (section)

== Applications ==

=== Compton scattering ===
Compton scattering is of prime importance to [[radiobiology]], as it is the most probable interaction of gamma rays and high energy X-rays with atoms in living beings and is applied in [[radiation therapy]].<ref>Camphausen KA, Lawrence RC. [http://www.cancernetwork.com/cancer-management-11/chapter02/article/10165/1399960 "Principles of Radiation Therapy"] {{Webarchive|url=https://web.archive.org/web/20090515031929/http://www.cancernetwork.com/cancer-management-11/chapter02/article/10165/1399960 |date=2009-05-15 }} in Pazdur R, Wagman LD, Camphausen KA, Hoskins WJ (Eds) [http://www.cancernetwork.com/cancer-management-11/ Cancer Management: A Multidisciplinary Approach] {{Webarchive|url=https://web.archive.org/web/20131004224102/http://www.cancernetwork.com/cancer-management-11/ |date=2013-10-04 }}. 11 ed. 2008.</ref>
<ref>
Ridwan, S. M., El-Tayyeb, F., Hainfeld, J. F., &amp; Smilowitz, H. M. (2020). Distributions of intravenous injected iodine nanoparticles in orthotopic U87 human glioma xenografts over time and tumor therapy. Nanomedicine, 15(24), 2369–2383. https://doi.org/10.2217/nnm-2020-0178</ref>

Compton scattering is an important effect in [[gamma spectroscopy]] which gives rise to the [[Compton edge]], as it is possible for the gamma rays to scatter out of the detectors used. [[Compton suppression]] is used to detect stray scatter gamma rays to counteract this effect.

=== Magnetic Compton scattering ===
Magnetic Compton scattering is an extension of the previously mentioned technique which involves the magnetisation of a crystal sample hit with high energy, circularly polarised photons. By measuring the scattered photons' energy and reversing the magnetisation of the sample, two different Compton profiles are generated (one for spin up momenta and one for spin down momenta). Taking the difference between these two profiles gives the magnetic Compton profile  (MCP), given by <math>J_{\text{mag}}(\mathbf{p}_z)</math> – a one-dimensional projection of the electron spin density.
<math display="block">J_{\text{mag}}(\mathbf{p}_z) = \frac{1}{\mu}\iint_{-\infty}^\infty (n_{\uparrow} (\mathbf{p}) - n_{\downarrow}(\mathbf{p})) d\mathbf{p}_x d\mathbf{p}_y</math>
where <math>\mu</math> is the number of spin-unpaired electrons in the system, <math>n_\uparrow(\mathbf{p})</math> and <math>n_\downarrow(\mathbf{p})</math> are the three-dimensional electron momentum distributions for the majority spin and minority spin electrons respectively.

Since this scattering process is [[Coherence (physics)|incoherent]] (there is no phase relationship between the scattered photons), the MCP is representative of the bulk properties of the sample and is a probe of the ground state. This means that the MCP is ideal for comparison with theoretical techniques such as [[density functional theory]].
The area under the MCP is directly proportional to the spin moment of the system and so, when combined with total moment measurements methods (such as [[SQUID]] magnetometry), can be used to isolate both the spin and orbital contributions to the total moment of a system.
The shape of the MCP also yields insight into the origin of the magnetism in the system.<ref name="Cooper2004">{{cite book|author=Malcolm Cooper|title=X-Ray Compton Scattering|url=https://books.google.com/books?id=m58jXIJDs3QC|access-date=4 March 2013|date=14 October 2004|publisher=[[OUP Oxford]]|isbn=978-0-19-850168-8}}</ref><ref>Barbiellini, B., Bansil, A. (2020). Scattering Techniques, Compton. Materials Science and Materials Engineering, Elsevier. https://doi.org/10.1016/B978-0-323-90800-9.00107-4
</ref>

=== Inverse Compton scattering ===
Inverse Compton scattering is important in [[astrophysics]]. In [[X-ray astronomy]], the [[accretion disk]] surrounding a [[black hole]] is presumed to produce a thermal spectrum. The lower energy photons produced from this spectrum are scattered to higher energies by relativistic electrons in the surrounding [[stellar corona|corona]]. This is surmised to cause the power law component in the X-ray spectra (0.2–10&nbsp;keV) of accreting black holes.<ref>{{cite web |last1=Dr. Tortosa |first1=Alessia |title=Comptonization mechanisms in hot coronae in AGN. The NuSTAR view |url=http://www.matfis.uniroma3.it/Allegati/Dottorato/TESI/tortosa/tesi_PhD_Tortosa_Alessia.pdf |publisher=DIPARTIMENTO DI MATEMATICA E FISICA}}</ref>

The effect is also observed when photons from the [[Cosmic microwave background radiation|cosmic microwave background]] (CMB) move through the hot gas surrounding a [[galaxy cluster]].  The CMB photons are scattered to higher energies by the electrons in this gas, resulting in the [[Sunyaev–Zel'dovich effect]]. Observations of the Sunyaev–Zel'dovich effect provide a nearly redshift-independent means of detecting galaxy clusters.

Some synchrotron radiation facilities scatter laser light off the stored electron beam.
This Compton backscattering produces high energy photons in the MeV to GeV range<ref>{{cite web|url=http://www.lnf.infn.it/~levisand/graal/graal.html |title=GRAAL home page |publisher=Lnf.infn.it |access-date=2011-11-08}}</ref><ref>{{cite web|url=https://tunl.duke.edu/research/our-facilities | title=Duke University TUNL HIGS Facility | access-date=2021-01-31}}</ref> subsequently used for nuclear physics experiments.

=== Non-linear inverse Compton scattering ===
[[Non-linear inverse Compton scattering]] (NICS) is the scattering of multiple low-energy photons, given by an intense electromagnetic field, in a high-energy photon (X-ray or gamma ray) during the interaction with a charged particle, such as an electron.<ref name=":0">{{Cite journal|last1=Di Piazza|first1=A.|last2=Müller|first2=C.|last3=Hatsagortsyan|first3=K. Z.|last4=Keitel|first4=C. H.|date=2012-08-16|title=Extremely high-intensity laser interactions with fundamental quantum systems|url=https://link.aps.org/doi/10.1103/RevModPhys.84.1177|journal=Reviews of Modern Physics|language=en|volume=84|issue=3|pages=1177–1228|doi=10.1103/RevModPhys.84.1177|issn=0034-6861|arxiv=1111.3886|bibcode=2012RvMP...84.1177D|s2cid=118536606}}</ref> It is also called non-linear Compton scattering and multiphoton Compton scattering. It is the non-linear version of inverse Compton scattering in which the conditions for multiphoton absorption by the charged particle are reached due to a very intense electromagnetic field, for example the one produced by a [[laser]].<ref>{{Cite journal|last=Meyerhofer|first=D.D.|date=1997|title=High-intensity-laser-electron scattering|url=https://ieeexplore.ieee.org/document/641308|journal=IEEE Journal of Quantum Electronics|volume=33|issue=11|pages=1935–1941|doi=10.1109/3.641308|bibcode=1997IJQE...33.1935M|url-access=subscription}}</ref>

Non-linear inverse Compton scattering is an interesting phenomenon for all applications requiring high-energy photons since NICS is capable of producing photons with energy comparable to the charged particle rest energy and higher.<ref>{{Cite journal|last=Ritus|first=V. I.|date=1985|title=Quantum effects of the interaction of elementary particles with an intense electromagnetic field|url=http://link.springer.com/10.1007/BF01120220|journal=Journal of Soviet Laser Research|language=en|volume=6|issue=5|pages=497–617|doi=10.1007/BF01120220|s2cid=121183948|issn=0270-2010|url-access=subscription}}</ref> As a consequence NICS photons can be used to trigger other phenomena such as pair production, Compton scattering, [[nuclear reaction]]s, and can be used to probe non-linear quantum effects and non-linear [[Quantum electrodynamics|QED]].<ref name=":0" />