Physics:Muon tomography

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Short description: Tomography technique based on high-energy muon particles


Muon tomography is a technique that uses cosmic ray muons to generate three-dimensional images of volumes using information contained in the Coulomb scattering of the muons. Since muons are much more deeply penetrating than X-rays, muon tomography can be used to image through much thicker material than x-ray based tomography such as CT scanning. The muon flux at the Earth's surface is such that a single muon passes through an area the size of a human hand per second.[1] Since its development in the 1950s, muon tomography has taken many forms, the most important of which are muon transmission radiography and muon scattering tomography. Muon tomography imagers are under development for the purposes of detecting nuclear material in road transport vehicles and cargo containers for the purposes of non-proliferation.[2][3] Another application is the usage of muon tomography to monitor potential underground sites used for carbon sequestration.[1]

History

Cosmic ray muons have been used for decades to radiograph objects such as pyramids and geological structures. The technique of muon transmission imaging was first used in the 1950s by Eric George to measure the depth of the overburden of a tunnel in Australia.[4] In a famous experiment in the 1960s, Luis Alvarez used muon transmission imaging to search for hidden chambers in the Pyramid of Chephren in Giza, although none were found at the time;[5] a later effort discovered[6] a previously unknown void in the Great Pyramid. In all cases the information about the absorption of the muons was used as a measure of the thickness of the material crossed by the cosmic ray particles.

Muon transmission imaging

More recently, muons have been used to image magma chambers to predict volcanic eruptions.[7] Kanetada Nagamine et al.[8] continue active research into the prediction of volcanic eruptions through cosmic ray attenuation radiography. Minato[9] used cosmic ray counts to radiograph a large temple gate. Emil Frlež et al.[10] reported using tomographic methods to track the passage of cosmic rays muons through cesium iodide crystals for quality control purposes. All of these studies have been based on finding some part of the imaged material that has a lower density than the rest, indicating a cavity. Muon transmission imaging is the most suitable method for acquiring this type of information.

Mu-Ray project

The Mu-Ray project is funded by the Istituto Nazionale di Fisica Nucleare (INFN, Italian National Institute for Nuclear Physics) and the Istituto Nazionale di Geofisica e Vulcanologia (Italian National Institute for Geophysics and Volcanology).[11] The Mu-Ray project is committed to map the inside of Mount Vesuvius, located in Naples, Italy. The last time this volcano erupted was in 1944. The goal of this project is to "see" inside the volcano which is being developed by scientists in Italy, France, the US and Japan.[12] This technology can be applied to volcanoes all around the world, to have a better understanding of when volcanoes will erupt.[13]

Muon scattering tomography

In 2003, the scientists at Los Alamos National Laboratory developed a new imaging technique: muon scattering tomography (MT). With muon scattering tomography, both incoming and outgoing trajectories for each particle are reconstructed. This technique has been shown to be useful to find materials with high atomic number in a background of high-z material such as uranium or material with a low atomic number.[14][15] Since the development of this technique at Los Alamos, a few different companies have started to use it for several purposes, most notably for detecting nuclear cargo entering ports and crossing over borders.

The Los Alamos National Laboratory team has built a portable Mini Muon Tracker (MMT). This muon tracker is constructed from sealed aluminum drift tubes,[16] which are grouped into twenty-four 1.2-meter-square (4 ft) planes. The drift tubes measure particle coordinates in X and Y with a typical accuracy of several hundred micrometers. The MMT can be moved via a pallet jack or a fork lift. If a nuclear material has been detected it is important to be able to measure details of its construction in order to correctly evaluate the threat.[17]

MT uses multiple scattering radiography. In addition to energy loss and stopping cosmic rays undergo Coulomb scattering. The angular distribution is the result of many single scatters. This results in an angular distribution that is Gaussian in shape with tails from large angle single and plural scattering. The scattering provides a novel method for obtaining radiographic information with charged particle beams. More recently, scattering information from cosmic ray muons has been shown to be a useful method of radiography for homeland security applications.[14][18][19][20]

Multiple scattering can be defined as when the thickness increases and the number of interactions become high the angular dispersion can be modelled as Gaussian. Where the dominant part of the multiple scattering polar-angular distribution is

[math]\displaystyle{ \frac{\mathrm{d}N}{\mathrm{d}\theta}={\frac{1}{2 \pi \theta_0^2}}\,\exp{\left(-\frac{\theta^2}{2 \theta_0^2}\right)}. }[/math]

where θ is the muon scattering angle and θ0 is the standard deviation of scattering angle, is given approximately by

[math]\displaystyle{ \theta_0={\frac{14.1\,\mathrm{MeV}}{pc \beta}}\sqrt{\frac{X}{X_0}}. }[/math]

The muon momentum and velocity are p and β, respectively, c is the speed of light, X is the length of scattering medium, and X0 is the radiation length for the material. This needs to be convolved with the cosmic ray momentum spectrum in order to describe the angular distribution.

The Image can then be reconstructed by use of GEANT4.[21] These runs include input and output vectors, [math]\displaystyle{ \vec{X} }[/math] in and [math]\displaystyle{ \vec{X} }[/math] out for each incident particle. The incident flux projected to the core location was used to normalize transmission radiography (attenuation method). From here the calculations are normalized for the zenith angle of the flux.

Muon Momentum Integrated Tomography System

Despite the various benefits of using cosmic ray muons for imaging large and dense objects, i.e., spent nuclear fuel casks and nuclear reactors, their wide applications are often limited by the naturally low muon flux at sea level, approximately 10,000 m−2min−1. To overcome this limitation, two important quantities—scattering angle, θ and momentum, p—for each muon event must be measured during the measurement. To measure cosmic ray muon momentum in the field, a fieldable muon spectrometer using multi-layer pressurized gas Cherenkov radiators has been developed and the muon spectrometer-tomography shows improved muon scattering tomography resolutions.[22]

Nuclear waste imaging

Tomographic techniques can be effective for non-invasive nuclear waste characterization and for nuclear material accountancy of spent fuel inside dry storage containers. Cosmic muons can improve the accuracy of data on nuclear waste and Dry Storage Containers (DSC). Imaging of DSC exceeds the IAEA detection target for nuclear material accountancy. In Canada, spent nuclear fuel is stored in large pools (fuel bays or wet storage) for a nominal period of 10 years to allow for sufficient radioactive cooling.[23]

Challenges and issues for nuclear waste characterization are covered at great length, summarized below:[24]

  • Historical waste. Non-traceable waste stream poses a challenge for characterization. Different types of waste can be distinguished: tanks with liquids, fabrication facilities to be decontaminated before decommissioning, interim waste storage sites, etc.
  • Some waste form may be difficult and/or impossible to measure and characterize (i.e. encapsulated alpha/beta emitters, heavily shielded waste).
  • Direct measurements, i.e. destructive assay, are not possible in many cases and Non-Destructive Assay (NDA) techniques are required, which often do not provide conclusive characterization.
  • Homogeneity of the waste needs characterization (i.e. sludge in tanks, in-homogeneities in cemented waste, etc.).
  • Condition of the waste and waste package: breach of containment, corrosion, voids, etc.

Accounting for all of these issues can take a great deal of time and effort. Muon Tomography can be useful to assess the characterization of waste, radiation cooling, and condition of the waste container.

Los Alamos Concrete Reactor

In the summer of 2011, a reactor mockup was imaged using Muon Mini Tracker (MMT) at Los Alamos.[25] The MMT consists of two muon trackers made up of sealed drift tubes. In the demonstration, cosmic-ray muons passing through a physical arrangement of concrete and lead; materials similar to a reactor were measured. The mockup consisted of two layers of concrete shielding blocks, and a lead assembly in between; one tracker was installed at 2.5 metres (8 ft 2 in) height, and another tracker was installed on the ground level at the other side. Lead with a conical void similar in shape to the melted core of the Three Mile Island reactor was imaged through the concrete walls. It took three weeks to accumulate 8×10^4 muon events. The analysis was based on point of closest approach, where the track pairs were projected to the mid-plane of the target, and the scattered angle was plotted at the intersection. This test object was successfully imaged, even though it was significantly smaller than expected at Fukushima Daiichi for the proposed Fukushima Muon Tracker (FMT).

Left – Lead reactor core with conic void. Right – Observed core where average scattering angles of muons are plotted. The void in the core is clearly imaged through two 2.74 metres (9 ft 0 in) concrete walls. The lead core of 0.7 metres (2 ft 4 in) thickness gives an equivalent radiation length to the uranium fuel in Unit 1, and gives a similar scattering angle. Hot spots at the corners are artifacts caused by edge effect of MMT.[25]

Fukushima application

On March 11, 2011, a 9.0-magnitude earthquake, followed by a tsunami, caused an ongoing nuclear crisis at the Fukushima Daiichi power plant. Though the reactors are stabilized, complete shutdown will require knowledge of the extent and location of the damage to the reactors. A cold shutdown was announced by the Japanese government in December, 2011, and a new phase of nuclear cleanup and decommissioning was started. However, it is hard to plan the dismantling of the reactors without any realistic estimate of the extent of the damage to the cores, and knowledge of the location of the melted fuel.[26][27] Since the radiation levels are still very high at the inside of the reactor core, it is not likely anyone can go inside to assess the damage. The Fukushima Daiichi Tracker (FDT) is proposed to see the extent of the damage from a safe distance. A few months of measurements with muon tomography, will show the distribution of the reactor core. From that, a plan can be made for reactor dismantlement; thus potentially shortening the time of the project many years.

In August 2014, Decision Sciences International Corporation it had been awarded a contract by Toshiba Corporation (Toshiba) to support the reclamation of the Fukushima Daiichi Nuclear complex with the use of Decision Science's muon tracking detectors.[28]

Non-proliferation

The Nuclear Non-proliferation Treaty (NPT) signed in 1968 was a major step in the non-proliferation of nuclear weapons. Under the NPT, non-nuclear weapon states were prohibited from, among other things, possessing, manufacturing or acquiring nuclear weapons or other nuclear explosive devices. All signatories, including nuclear weapon states, were committed to the goal of total nuclear disarmament.

The Comprehensive Nuclear-Test-Ban Treaty (CTBT) bans all nuclear explosions in any environments. Tools such as muon tomography can help to stop the spread of nuclear material before it is armed into a weapon.[29]

The New START[30] treaty signed by the US and Russia aims to reduce the nuclear arsenal by as much as a third. The verification involves a number of logistically and technically difficult problems. New methods of warhead imaging are of crucial importance for the success of mutual inspections.

Muon Tomography can be used for treaty verification due to many important factors. It is a passive method; it is safe for humans and will not apply an artificial radiological dose to the warhead. Cosmic rays are much more penetrating than gamma or x-rays. Warheads can be imaged in a container behind significant shielding and in presence of clutter. Exposure times depend on the object and detector configuration (~few minutes if optimized). While SNM detection can be reliably confirmed, and discrete SNM objects can be counted and localized, the system can be designed to not reveal potentially sensitive details of the object design and composition.[31]

The Multi-Mode Passive Detection System (MMPDS) port scanner, located in the Freeport, Bahamas can detect both shielded nuclear material, as well as explosives and contraband. The scanner is large enough for a cargo container to pass through, making it a scaled-up version of the Mini Muon Tracker. It then produces a 3-D image of what is scanned.[32]

Tools such as the MMPDS can be used to prevent the spread of nuclear weapons. The safe but effective use of cosmic rays can be implemented in ports to help non-proliferation efforts. Or even in cities, under overpasses, or entrances to government buildings.

Pyramid chamber detection

Muon tomography is extensively used for the ScanPyramids mission, which was launched in October 2015, in the hope of discovering hidden chambers in the Egyptian pyramids. The main objective was to use non-destructive methods to find new pathways and chambers within the pyramid. In November 2017, it was reported that three separate teams independently found a large hidden chamber in the Great Pyramid of Giza with the help of muon tomography.

Cosmic Ray Inspection and Passive Tomography (CRIPT)

The Cosmic Ray Inspection and Passive Tomography (CRIPT)[33] detector is a Canadian muon tomography project which tracks muon scattering events while simultaneously estimating the muon momentum. The CRIPT detector is 5.3 metres (17 ft) tall and has a mass of 22 tonnes (22 long tons; 24 short tons). The majority of the detector mass is located in the muon momentum spectrometer which is a feature unique to CRIPT regarding muon tomography.

After initial construction and commissioning[34] at Carleton University in Ottawa, Canada , the CRIPT detector was moved to Atomic Energy Of Canada Limited's Chalk River Laboratories.[35]

The CRIPT detector is presently examining the limitations on detection time for border security applications, limitations on muon tomography image resolution, nuclear waste stockpile verification, and space weather observation through muon detection.

See also

References

  1. 1.0 1.1 "Muon Tomography - Deep Carbon, MuScan, Muon-Tides". Boulby Underground Science Facility. http://www.stfc.ac.uk/Boulby/Projects/MuonTomography/39350.aspx. 
  2. Fishbine, Brian. "Muon Radiography". Detecting Nuclear Contraband. Los Alamos National Laboratory. http://www.lanl.gov/quarterly/q_spring03/muon_text.shtml. 
  3. J. Bae; S. Chatzidakis (2021). "The Effect of Cosmic Ray Muon Momentum Measurement for Monitoring Shielded Special Nuclear Materials". INMM & ESARDA Joint Virtual Annual Meeting. 
  4. George, E.P. (July 1, 1955). "Cosmic rays measure overburden of tunnel". Commonwealth Engineer: 455. 
  5. Alvarez, Luis W.; Anderson, Jared A.; Bedwei, F. El; Burkhard, James; Fakhry, Ahmed; Girgis, Adib; Goneid, Amr; Hassan, Fikhry et al. (1970-02-06). "Search for Hidden Chambers in the Pyramids: The structure of the Second Pyramid of Giza is determined by cosmic-ray absorption" (in en). Science 167 (3919): 832-839. doi:10.1126/science.167.3919.832. ISSN 0036-8075. OCLC 1644869. PMID 17742609. Bibcode1970Sci...167..832A. 
  6. Marchant, Jo (2017-11-02). "Cosmic-ray particles reveal secret chamber in Egypt's Great Pyramid" (in en). Nature 551 (7678). doi:10.1038/nature.2017.22939. ISSN 0028-0836. OCLC 01586310. 
  7. Kedar, Sharon; Tanaka, Hiroyuki K. M.; Naudet, C.J.; Jones, C.E.; Plaut, J.P.; Webb, F.H. (2013-06-14). "Muon radiography for exploration of Mars geology" (in en). Geoscientific Instrumentation, Methods and Data Systems 2 (1): 157-164. doi:10.5194/gi-2-157-2013. ISSN 2193-0856. OCLC 929687607. Bibcode2013GI......2..157K. 
  8. Nagamine, Kanetada; Iwasaki, Masahiko; Shimomura, Kohichiro; Ishida, Katsuhiro (1995-03-15). "Method of probing inner-structure of geophysical substance with the horizontal cosmic-ray muons and possible application to volcanic eruption prediction" (in en). Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (Elsevier) 356 (2-3): 585-595. doi:10.1016/0168-9002(94)01169-9. ISSN 0168-9002. OCLC 781521572. Bibcode1995NIMPA.356..585N. 
  9. Minato, S. (1988). "Feasibility of cosmic-ray radiography: a case study of a temple gate as a test piece". Materials Evaluation 46 (11): 1468–1470. 
  10. Frlež, Emil; Supek, Ivan; Assamagan, Kétévi Adiklè; Brönnimann, Ch.; Flügel, Th.; Krause, Bernward; Lawrence, David W.; Mzavia, David A. et al. (2000-01-21). "Cosmic muon tomography of pure cesium iodide calorimeter crystals" (in en). Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (Elsevier) 440 (1): 57-85. doi:10.1016/S0168-9002(99)00886-4. ISSN 0168-9002. OCLC 781521572. Bibcode2000NIMPA.440...57F. 
  11. Beauducel, F.; Buontempo, S.; D’Auria, L.; De, G.; Festa, G.; Gasparini, P.; Gibert1, D.; Iacobucci, G. et al. (2008-07-18). "Muon radiography of volcanoes and the challenge at Mt. Vesuvius" (in en) (PDF). https://www.researchgate.net/publication/235429847. 
  12. Martinelli, Bruno (1997-05-01). "Volcanic tremor and short-term prediction of eruptions". Journal of Volcanology and Geothermal Research (Elsevier) 77 (1-4): 305-311. doi:10.1016/S0377-0273(96)00101-1. ISSN 0377-0273. Bibcode1997JVGR...77..305M. 
  13. Paolo Strolin (August 2013). "The secret life of volcanoes: using muon radiography". Science in School (27). 
  14. 14.0 14.1 Borozdin, Konstantin N.; Hogan, Gary E.; Morris, Christopher; Priedhorsky, William C.; Saunders, Alexander; Schultz, Larry J.; Teasdale, Margaret E. (2003-03-20). "Radiographic imaging with cosmic-ray muons" (in en). Nature 422 (277): 277. doi:10.1038/422277a. ISSN 0028-0836. OCLC 01586310. PMID 12646911. Bibcode2003Natur.422..277B. 
  15. Hohlmann, Marcus; Ford, Patrick; Gnanvo, Kondo; Helsby, Jennifer; Pena, David; Hoch, Richard; Mitra, Debasis (2009-06-01). "GEANT4 Simulation of a Cosmic Ray Muon Tomography System With Micro-Pattern Gas Detectors for the Detection of High-Z Materials" (in en). IEEE Transactions on Nuclear Science 56 (3): 1356–1363. doi:10.1109/TNS.2009.2016197. ISSN 0018-9499. OCLC 01586310. PMID 12646911. Bibcode2009ITNS...56.1356H. 
  16. Wang, Zhehui; Morris, Christopher L.; Makela, Mark F.; Bacon, Jeffrey D.; Baer, E.E.; Brockwell, M.I.; Brooks, B.J.; Clark, D.J. et al. (2009-07-01). "Inexpensive and practical sealed drift-tube neutron detector" (in en). Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (Elsevier) 605 (3): 430-432. doi:10.1016/j.nima.2009.03.251. ISSN 0168-9002. OCLC 781521572. Bibcode2009NIMPA.605..430W. https://zenodo.org/record/1259263. 
  17. Riggi, S.; Antonuccio, V.; Bandieramonte, M.; Becciani, U.; Belluomo, F.; Belluso, M.; Billotta, S.; Bonanno, G. et al. (2012-07-03). "A large area cosmic ray detector for the inspection of hidden high-Z materials inside containers" (in en). Journal of Physics (IOP Publishing) 409 (1): 012046. doi:10.1016/j.nima.2009.03.251. ISSN 1742-6588. OCLC 723581599. Bibcode2013JPhCS.409a2046R. 
  18. Morris, Christopher L.; Alexander, C. C.; Bacon, Jeffrey D.; Borozdin, Konstantin N.; Clark, D. J.; Chartrand, R.; Espinoza, C. J.; Fraser, A. M. et al. (2008-10-28). "Tomographic Imaging with Cosmic Ray Muons" (in en). Science & Global Security: The Technical Basis for Arms Control, Disarmament, and Nonproliferation Initiatives (Taylor & Francis) 16 (1-2): 37-53. doi:10.1080/08929880802335758. ISSN 0892-9882. OCLC 960783661. Bibcode2008S&GS...16...37M. 
  19. Priedhorsky, William C.; Borozdin, Konstantin N.; Hogan, Gary E.; Morris, Christopher; Saunders, Alexander; Schultz, Larry J.; Teasdale, Margaret E. (2003-07-02). "Detection of high-Z objects using multiple scattering of cosmic ray muons" (in en). Review of Scientific Instruments (American Institute of Physics) 74 (10): 4294-4297. doi:10.1063/1.1606536. ISSN 0034-6748. OCLC 243417110. Bibcode2003RScI...74.4294P. 
  20. L. J. Schultz; G. S. Blanpied; K. N. Borozdin; A. M. Fraser; N. W. Hengartner; A. V. Klimenko; C. L. Morris; C. Oram et al. (2007). "Statistical Reconstruction for Cosmic Ray Muon Tomography". IEEE Transactions on Image Processing 16 (8): 1985–1993. doi:10.1109/TIP.2007.901239. PMID 17688203. Bibcode2007ITIP...16.1985S. 
  21. S. Agostinelli (2003). "Geant4 a Simulation toolkit". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 506 (3): 250–303. doi:10.1016/S0168-9002(03)01368-8. Bibcode2003NIMPA.506..250A. http://infoscience.epfl.ch/record/49909. 
  22. J. Bae; S. Chatzidakis (2022). "Fieldable muon spectrometer using multi-layer pressurized gas Cherenkov radiators and its applications". Scientific Reports 12 (2559): 2559. doi:10.1038/s41598-022-06510-2. PMID 35169208. Bibcode2022NatSR..12.2559B. 
  23. Jonkmans, Guy; Anghel, Vinicius Nicolae Petre; Jewett, Cybele; Thompson, Martin (2013-03-01). "Nuclear waste imaging and spent fuel verification by muon tomography" (in en). Annals of Nuclear Energy (Elsevier) 53: 267-273. doi:10.1016/j.anucene.2012.09.011. ISSN 0306-4549. OCLC 50375208. 
  24. International Atomic Energy Agency (2007). Strategy and methodology for radioactive waste characterization. Vienna: International Atomic Energy Agency. ISBN 9789201002075. 
  25. 25.0 25.1 Miyadera, Haruo; Borozdin, Konstantin N.; Greene, Steve J.; Lukić, Zarija; Masuda, Koji; Milner, Edward C.; Morris, Christopher L.; Perry, John O. (2013-05-24). "Imaging Fukushima Daiichi reactors with muons" (in en). AIP Advances (American Institute of Physics) 3 (5): 052133. doi:10.1063/1.4808210. ISSN 2158-3226. OCLC 780660465. Bibcode2013AIPA....3e2133M. "In the summer of 2011, a reactor mockup was imaged using Muon Mini Tracker (MMT) at Los Alamos (altitude of 2,231 m).". 
  26. Stone, R. (2011). "Fukushima Cleanup Will Be Drawn Out and Costly". Science 331 (6024): 1507. doi:10.1126/science.331.6024.1507. PMID 21436414. Bibcode2011Sci...331.1507S. 
  27. Burns, Peter C.; Ewing, Rodney C.; Navrotsky, Alexandra (2012). "Nuclear Fuel in a Reactor Accident". Science 335 (6073): 1184–1188. doi:10.1126/science.1211285. PMID 22403382. Bibcode2012Sci...335.1184B. 
  28. Blackwell, Shelia S. (4 August 2014). "Decision Sciences Awarded Toshiba Contract for Fukushima Daiichi Nuclear Complex Project" (Press release). Middleburg, Virginia: Decision Sciences. Archived from the original on 28 April 2021. Retrieved 22 December 2021. MIDDLEBURG, Va., Aug. 8, 2014 – Decision Sciences International Corporation (DSIC), an advanced technology provider of security and detection systems, today announced it has been awarded a contract by Toshiba Corporation (Toshiba) to support the reclamation of the Fukushima Daiichi Nuclear complex with the use of DSIC’s revolutionary muon tracking detectors.
  29. "Comprehensive Nuclear-Test-Ban Treaty CTBTO". CTBTO Preparatory Commission. http://www.ctbto.org/fileadmin/content/treaty/treaty_text.pdf. 
  30. "The New START Treaty and Protocol". whitehouse.gov. 2010-04-08. https://obamawhitehouse.archives.gov/blog/2010/04/08/new-start-treaty-and-protocol. 
  31. Borozdin, K.N.; Morris, C.; Klimenko, A.V.; Spaulding, R.; Bacon, J. (2010). Passive Imaging of SNM with Cosmic-Ray Generated Neutrons and Gamma-Rays. 3864–3867. doi:10.1109/NSSMIC.2010.5874537. ISBN 978-1-4244-9106-3. 
  32. "Decision Sciences Corp". http://www.decisionsciencescorp.com/solutions/mmpds/. 
  33. Anghel, Vinicius Nicolae Petre; Armitage, John C.; Baig, F.; Boniface, K.; Boudjemline, K.; Bueno, J.; Charles, E.; Drouin, P-L. et al. (2015-10-01). "A plastic scintillator-based muon tomography system with an integrated muon spectrometer" (in en). Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (Elsevier) 798 (3): 12-23. doi:10.1016/j.nima.2015.06.054. ISSN 0168-9002. OCLC 781521572. Bibcode2015NIMPA.798...12A. 
  34. "Cosmic Ray Inspection and Passive Tomography" (in en-ca). 2021. https://physics.carleton.ca/cript/. 
  35. "A closer look at CRIPT: Commissioning of Canada's first full-scale muon tomography imaging system" (in en-ca). 2013-04-22. http://www.aecl.ca/en/home/news-and-publications/stories/2013/130422.aspx.