Positron Reaction Microscopy
Lead Research Organisation:
University College London
Department Name: Physics and Astronomy
Abstract
Studies with positrons and positronium, the short-lived atom made of an electron and its antimatter counterpart the positron, range from fundamental tests of annihilation and investigations of events in the galactic centre (where it is estimated that approximately 93% of all annihilation events occur through the decay of Ps) to practical applications such as characterization of microscopic voids in materials as well as medical diagnostics and therapy. Much has been learnt, in the past few decades, about the interactions of positrons and Ps with atoms and molecules thanks to the ability of performing controlled reactions with these projectiles, of analyzing final-state products with improved sensitivity together with increasingly sophisticated theoretical descriptions. The aim of this proposal is to advance this knowledge and explore particular aspects of fundamental antimatter-matter interactions. Of particular interest here are reactions resulting in fragmentation of atoms and molecules as driven by positrons.In order to study these, a major instrumental development is proposed consisting of a 'positron reaction microscope'. It will require the development of a bright positron-beam, a cold gas jet and a spectrometer. The reaction products from the intersection of the two beams will be imaged and their trajectory termina and times-of-flight will be determined. From these, a complete picture of the reaction will be extracted and unprecented insight in positron driven reactions will be gained.
People |
ORCID iD |
| Gaetana Laricchia (Principal Investigator) |
Publications
Arcidiacono C
(2007)
Double-differential ionization cross-section for H2O
in Radiation Physics and Chemistry
Arcidiacono C
(2009)
Ion production by positron impact on H 2 O
in Journal of Physics B: Atomic, Molecular and Optical Physics
Brawley SJ
(2010)
Resonant scattering of positronium in collision with CO2.
in Physical review letters
Brawley SJ
(2010)
Electron-like scattering of positronium.
in Science (New York, N.Y.)
Cooke D
(2012)
Positronium formation with excitation
in Journal of Physics: Conference Series
Cooke D
(2008)
Direct non-dissociative and dissociative ionization of CO2 by positron impact
in Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms
Cooke D
(2014)
Ionization cross-sections for positron collisions with N2
in The European Physical Journal D
Cooke DA
(2010)
Simultaneous ionization and excitation of molecules by positron impact.
in Physical review letters
Cooke, David A.
(2014)
Ionization cross-sections for positron collisions with N2
D.A. Cooke (Co-Author)
(2010)
Positronium formation cross-sections for Xe, CO(2) and N(2)
| Description | Studies with positrons and positronium, the short-lived atom made of an electron and its antimatter counterpart the positron, range from fundamental tests of annihilation and investigations of events in the galactic centre (where it is estimated that approximately 93% of all annihilation events occur through the decay of Ps) to practical applications such as characterization of microscopic voids in materials as well as medical diagnostics and therapy. Much has been learnt, in the past few decades, about the interactions of positrons and Ps with atoms and molecules thanks to the ability of performing controlled reactions with these projectiles, of analyzing final-state products with improved sensitivity together with increasingly sophisticated theoretical descriptions. The aim of this work has been to advance this knowledge and explore particular aspects of fundamental antimatter-matter interactions. Of particular interest here have been reactions resulting in ionization-fragmentation of atoms and molecules as driven by positrons. In order to study these, a major instrumental development has been undertaken consisting of a 'positron reaction microscope'. It has required the development of a brightness-enhanced positron-beam, a cold gas jet and a spectrometer. The beam is tunable in an energy range (5-500) eV with an angular divergence of 1° and an energy resolution of 1%. The efficiency of tungsten meshes and thin foils for moderation of fast positrons from 22 Na has also been investigated in transmission geometry and a fair agreement has been found with previous experimental results where directly comparable. For foils, the dependence on material thickness is found to be similar to the prediction of the Vehanen-Mäkinen diffusion model; however, the magnitude is 5-10 times lower. A broad consensus is observed between experiment and the results of a three-dimensional model developed in this work. For a given thickness, meshes are found to be generally better than foils by around a factor of 10 with a maximum efficiency ( ~~ 10-3) comparable to that achieved with thin single crystal foils, in accord with previous measurements and the results of the present model. This work has been supplemented by investigations of ionizing collisions involving excitation of the target and/or the positronium atom formed as well as positron-induced fragmentation of molecular targets. In particular, cross sections for ionization excitation of CO2 and N2 by positron impact have been measured for the first time and found to exceed those for electron impact factors of 3-5, the enhancement arising primarily via positronium formation. The cross sections for the formation of positronium in the 2P state in collisions of positrons with He, Ar, and Xe atoms have been determined by measuring coincidences between the remnant ion and the Lyman-alpha photon from positronium. The maximum fractional contributions to the total Ps formation cross sections have been found to increase progressively in going from He to Xe. The total and direct ionization cross-sections for positron impact on N2 have been measured in the energy range from 5 eV to 850 eV. The results have been compared with other experimental and theoretical determinations. The energy distributions of positrons forward scattered from H2O have been measured in coincidence with the remnant ions (H2O+, OH+ and H+) . The maxima of the energy distributions associated with the production of OH+ and H+ are about 5-10 times smaller than that for (HO+)-O-2. |
| Exploitation Route | In the long term, positron/Ps scattering may also impact upon the risk assessment associated with medical diagnostics and therapeutic protocols of positron-emission-tomography, material characterization (primarily through annihilation and positronium formation). The public/industrial sector will also benefit through knowledge transfer as well as the training of talented young scientists in performing world-class science and in developing a variety of skills (e.g. problem-solving, creativity, communication, etc). The immediate beneficiaries of the research will be other scientists studying positron and positronium physics, atomic and molecular physics, astrophysics. The theme of the research is ionization, a process which is particularly interdisciplinary, with relevance in chemistry, environmental studies, plasma physics. |
| Sectors | Chemicals,Environment,Healthcare |
| URL | http://www.ucl.ac.uk/positron-physics/title.html |
| Description | Positrons and positronium are fundamental to our understanding of the physical universe. They have also become exceptionally powerful in the biomedical industry and useful in practical applications ranging from material science to engineering . The main beneficiaries of the outcomes of our research are primarily other scientists, including modellers of astrophysical and radiobiological processes as well as plasma diagnostics . Benefits arise for the public/industrial sector also through the training of talented young scientists in performing world-class science and in developing a variety of skills (e.g. problem-solving, creative, communication, etc), crucial in innovative endevours in academia and industry. Recent members of the group are now working at prestigious research labs (e.g. CERN, RIKEN, ETH) , in the UK Industry (e.g. Health Protection Agency, BAE Systems Detica, Thermo Fisher Scientific) and the financial sector. Antimatter is a powerful vehicle for stimulating interest and promoting understanding in physics and science by the general public and especially by young people. In the framework of the departmental "Science for the Public" initiatives, we endeavour to generate public awareness and engagement through popular publications and by delivering popular lectures / talks at schools or interested societies. |
| First Year Of Impact | 2008 |
| Sector | Aerospace, Defence and Marine,Education,Environment,Healthcare,Manufacturing, including Industrial Biotechology |
| Impact Types | Cultural,Societal,Economic |
| Description | Standard Research |
| Amount | £560,729 (GBP) |
| Funding ID | EP/P009395/1 |
| Organisation | Engineering and Physical Sciences Research Council (EPSRC) |
| Sector | Public |
| Country | United Kingdom |
| Start | 11/2016 |
| End | 10/2019 |
| Description | ATOMKI |
| Organisation | University of Tsukuba |
| Department | Division of Physics |
| Country | Japan |
| Sector | Academic/University |
| PI Contribution | Positron physics expertize |
| Collaborator Contribution | Ion collision physics expertize |
| Impact | Record 1 of 15 By:M. Shipman, S.J. Brawley, L. Sarkadi and G. Laricchia Phys. Rev. A 93 (2017) 032704 By: A. Loreti, R. Kadokura, S. E. Fayer, A. Kover and G. Laricchia Phys. Rev. Lett. 117 (2016) 253401 By: S. E. Fayer, A. Loreti, S.L. Andersen, A. Kover and G. Laricchia J. Phys. B 49 (2016) 075202 Magnetic field-free measurements of the total cross section for positrons scattering from helium and krypton By: Williams, AI (Williams, A. I.); Murtagh, DJ (Murtagh, D. J.); Fayer, SE (Fayer, S. E.); Andersen, SL (Andersen, S. L.); Chevallier, J (Chevallier, J.); Kover, A (Koever, A.); Van Reeth, P (Van Reeth, P.); Humberston, JW (Humberston, J. W.); Laricchia, G (Laricchia, G.) Title: Moderation and diffusion of positrons in tungsten meshes and foils Source: JOURNAL OF APPLIED PHYSICS Volume: 118 Issue: 10 Article Number: 105302 DOI: 10.1063/1.4930033 Published: SEP 14 2015 ISSN: 0021-8979 eISSN: 1089-7550 Accession Number: WOS:000361636900043 Record 2 of 14 By: Fayer, SE (Fayer, S. E.); Loreti, A (Loreti, A.); Kover, A (Koever, A.); Andersen, SL (Andersen, S. L.); Laricchia, G (Laricchia, G.) Edited by: Diaz, C (Diaz, C); Rabadan I (Rabadan, I); Garcia, G (Garcia, G); Mendez, L (Mendez, L); Martin, F (Martin, F) Title: An electrostatic positron beam for atomic and molecular collision experiments Source: XXIX INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC, AND ATOMIC COLLISIONS (ICPEAC2015), PTS 1-12 Book Series Title: Journal of Physics Conference Series Volume: 635 Article Number: 052070 DOI: 10.1088/1742-6596/635/5/052070 Published: 2015 Conference Title: 29th International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC) Conference Date: JUL 22-28, 2015 Conference Location: Toledo, SPAIN Sponsor(s): Univ Autonoma Madrid; Consejo Super Investigaciones Cient ISSN: 1742-6588 ISBN: ***************** Accession Number: WOS:000366407000317 Record 3 of 14 By: Kover, A (Koever, A.); Williams, AI (Williams, A. I.); Murtagh, DJ (Murtagh, D. J.); Fayer, SE (Fayer, S. E.); Laricchia, G (Laricchia, G.) Title: An electrostatic brightness-enhanced timed positron beam for atomic collision experiments Source: MEASUREMENT SCIENCE & TECHNOLOGY Volume: 25 Issue: 7 Article Number: 075013 DOI: 10.1088/0957-0233/25/7/075013 Published: JUL 2014 ISSN: 0957-0233 eISSN: 1361-6501 Accession Number: WOS:000338634700014 Record 4 of 14 By: Laricchia, G (Laricchia, G.); Cooke, DA (Cooke, D. A.); Kover, A (Koever, A.); Brawley, SJ (Brawley, S. J.) Edited by: Whelan, CT (Whelan, CT) Title: Experimental aspects of ionization studies by positron and positronium impact Source: FRAGMENTATION PROCESSES: TOPICS IN ATOMIC AND MOLECULAR PHYSICS Pages: 116-136 Published: 2013 ISBN: 978-1-107-00744-4 Accession Number: WOS:000315651700006 Record 5 of 14 By: Kover, A (Koever, A.); Murtagh, DJ (Murtagh, D. J.); Williams, AI (Williams, A. I.); Laricchia, G (Laricchia, G.) Edited by: Campeanu, RI (Campeanu, RI); Darewych, JW (Darewych, JW); Stauffer, AD (Stauffer, AD) Title: Differential Ionization Studies by Positron Impact Source: XV INTERNATIONAL WORKSHOP ON LOW ENERGY POSITRON AND POSITRONIUM PHYSICS Book Series Title: Journal of Physics Conference Series Volume: 199 Article Number: 012020 DOI: 10.1088/1742-6596/199/1/012020 Published: 2010 Conference Title: 15th International Workshop on Low Energy Positron and Positronium Physics Conference Date: JUL 29-AUG 01, 2009 Conference Location: York Univ, Toronto, CANADA Conference Host: York Univ ISSN: 1742-6588 ISBN: ***************** Accession Number: WOS:000280343800020 Record 6 of 14 By: Williams, AI (Williams, A. I.); Kover, A (Koever, A.); Murtagh, DJ (Murtagh, D. J.); Laricchia, G (Laricchia, G.) Edited by: Campeanu, RI (Campeanu, RI); Darewych, JW (Darewych, JW); Stauffer, AD (Stauffer, AD) Title: Progress Towards a Positron Reaction Microscope Source: XV INTERNATIONAL WORKSHOP ON LOW ENERGY POSITRON AND POSITRONIUM PHYSICS Book Series Title: Journal of Physics Conference Series Volume: 199 Article Number: 012025 DOI: 10.1088/1742-6596/199/1/012025 Published: 2010 Conference Title: 15th International Workshop on Low Energy Positron and Positronium Physics Conference Date: JUL 29-AUG 01, 2009 Conference Location: York Univ, Toronto, CANADA Conference Host: York Univ ISSN: 1742-6588 ISBN: ***************** Accession Number: WOS:000280343800025 Record 7 of 14 By: Arcidiacono, C (Arcidiacono, C.); Beale, J (Beale, J.); Pesic, ZD (Pesic, Z. D.); Kover, A (Kover, A.); Laricchia, G (Laricchia, G.) Title: Ion production by positron impact on H2O Source: JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS Volume: 42 Issue: 6 Article Number: 065205 DOI: 10.1088/0953-4075/42/6/065205 Published: MAR 28 2009 ISSN: 0953-4075 Accession Number: WOS:000264386400014 Record 8 of 14 By: Laricchia, G (Laricchia, G.); Brawley, S (Brawley, S.); Cooke, DA (Cooke, D. A.); Kover, A (Koever, A.); Murtagh, DJ (Murtagh, D. J.); Williams, AI (Williams, A. I.) Edited by: Orel, AE (Orel, AE); Starace, AF (Starace, AF); Nikolic, D (Nikolic, D); Berrah, N (Berrah, N); Gorczyca, TW (Gorczyca, TW); Kamber, EY (Kamber, EY); Tanis, JA (Tanis, JA) Title: Ionization in positron- and positronium- collisions with atoms and molecules Source: XXVI INTERNATIONAL CONFERENCE ON PHOTONIC, ELECTRONIC AND ATOMIC COLLISIONS Book Series Title: Journal of Physics Conference Series Volume: 194 Article Number: 012036 DOI: 10.1088/1742-6596/194/1/012036 Published: 2009 Conference Title: 26th International Conference on Photonic, Electronic and Atomic Collisions Conference Date: JUL 22-28, 2009 Conference Location: Western Michigan Univ, Kalamazoo, MI Sponsor(s): CRYOGENIC Ltd; IOP; Kalamazoo Cty Convent & Visitors Bur; Natl Electrostat Corp; PhysMath Cent; RoentDek Handels GmbH; Taylor & Francis Grp; WIENER Corp; WMU, Dept Phys; WMU, Coll Arts & Sci; WMU, Off Vice President Res; WMU, Grad Coll; WMU, Diether H Haenicke Inst Global Educ Conference Host: Western Michigan Univ ISSN: 1742-6588 ISBN: ***************** Accession Number: WOS:000282024600036 Record 9 of 14 By: Cooke, DA (Cooke, D. A.); Murtagh, DJ (Murtagh, D. J.); Kover, A (Kover, A.); Laricchia, G (Laricchia, G.) Title: Direct non-dissociative and dissociative ionization of CO2 by positron impact Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Volume: 266 Issue: 3 Pages: 466-470 DOI: 10.1016/j.nimb.2007.12.026 Published: FEB 2008 Conference Title: 14th International Workshop on Low-Energy Positron and Positronium Physics Conference Date: AUG 01-04, 2007 Conference Location: Univ Reading, Reading, ENGLAND Conference Host: Univ Reading ISSN: 0168-583X Accession Number: WOS:000255671600024 Record 10 of 14 By: Brawley, SJ (Brawley, S. J.); Beale, J (Beale, J.); Armitage, S (Armitage, S.); Leslie, DE (Leslie, D. E.); Kover, A (Kover, A.); Laricchia, G (Laricchia, G.) Title: Fragmentation of positronium in collision with xenon Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Volume: 266 Issue: 3 Pages: 497-501 DOI: 10.1016/j.nimb.2007.12.031 Published: FEB 2008 Conference Title: 14th International Workshop on Low-Energy Positron and Positronium Physics Conference Date: AUG 01-04, 2007 Conference Location: Univ Reading, Reading, ENGLAND Conference Host: Univ Reading ISSN: 0168-583X Accession Number: WOS:000255671600029 Record 11 of 14 By: Laricchia, G (Laricchia, G.); Armitage, S (Armitage, S.); Kover, A (Koever, A.); Murtagh, DJ (Murtagh, D. J.) Edited by: Arimondo, E (Arimondo, E); Berman, PR (Berman, PR); Lin, CC (Lin, CC) Title: Ionizing Collisions by Positrons and Positronium Impact on the Inert Atoms Source: ADVANCES IN ATOMIC, MOLECULAR, AND OPTICAL PHYSICS, VOL 56 Book Series Title: Advances In Atomic Molecular and Optical Physics Volume: 56 Pages: 1-47 DOI: 10.1016/S1049-250X(08)00010-4 Published: 2008 ISSN: 1049-250X ISBN: 978-0-12-374290-2 Accession Number: WOS:000260857800001 Record 12 of 14 By: Arcidiacono, C (Arcidiacono, C.); Kover, A (Koever, A.); Pesic, ZD (Pesic, Z. D.); Beale, J (Beale, J.); Laricchia, G (Laricchia, G.) Title: Double-differential ionization cross-section for H(2)O Source: RADIATION PHYSICS AND CHEMISTRY Volume: 76 Issue: 3 Pages: 431-435 DOI: 10.1016/j.radphyschem.2005.12.056 Published: MAR 2007 Conference Title: 3rd Conference on Elementary Processes in Atomic Systems Conference Date: AUG 31-SEP 02, 2005 Conference Location: Univ Miskole, Miskole, HUNGARY Sponsor(s): Univ Miskole, Dept Phys; European Phys Soc Conference Host: Univ Miskole ISSN: 0969-806X Accession Number: WOS:000243742300013 Record 13 of 14 By: Arcidiacono, C (Arcidiacono, C); Kover, A (Kover, A); Laricchia, G (Laricchia, G) Title: Energy-sharing asymmetries in ionization by positron impact Source: PHYSICAL REVIEW LETTERS Volume: 95 Issue: 22 Article Number: 223202 DOI: 10.1103/PhysRevLett.95.223202 Published: NOV 25 2005 ISSN: 0031-9007 Accession Number: WOS:000233458500020 PubMed ID: 16384216 Record 14 of 14 By: Kover, A (Kover, A); Arcidiacono, C (Arcidiacono, C); Laricchia, G (Laricchia, G) Title: Differential ionization experiments on positron-atom scattering Source: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS Volume: 221 Pages: 56-59 DOI: 10.1016/j.nimb.2004.03.031 Published: JUL 2004 Conference Title: 12th International Workshop on Positron and Positronium Physics (POSITRON03) Conference Date: JUL 19-21, 2003 Conference Location: Aarhus Univ, Inst Phys & Astron, Sandbjerg, DENMARK Sponsor(s): Aarhus Univ, Fac Sci; Danish Nat Sci Res Council; Carlsberg Fdn; Knud Hojgaards Fond; Oticon Fonden; Toyota Fonden; Danfysik a/s Conference Host: Aarhus Univ, Inst Phys & Astron ISSN: 0168-583X Accession Number: WOS:000221998000011 |
| Description | Aarhus University |
| Organisation | Aarhus University |
| Department | Department of Physics and Astronomy |
| Country | Denmark |
| Sector | Academic/University |
| PI Contribution | Testing the efficiency and characteristics of thin-film single-crystals to positron moderation and remoderation and training of student |
| Collaborator Contribution | Provision of thin-film single-crystals for positron moderation and remoderation and secondment of student |
| Impact | Magnetic field-free measurements of the total cross section for positrons scattering from helium and krypton S. E. Fayer, A. Loreti, S.L. Andersen, A. Kover and G. Laricchia J. Phys. B 49 (2016) 075202 http://iopscience.iop.org/0953-4075;jsessionid=45F26BC909B9E8C22C53723A042F5855.c1.iopscience.cld.iop.org Moderation and diffusion of positrons in tungsten meshes and foils A. I. Williams, D. J. Murtagh, S. E. Fayer, S.L. Andersen, J. Chevallier, A. Kover, P. Van Reeth , J.W. Humberston and G. Laricchia J. Appl. Phys. 118 (2015) 105302 An electrostatic positron beam for atomic and molecular collision experiments S E Fayer, A Loreti, A Kover, S L Andersen and G Laricchia Journal of Physics: Conference Series 635 (2015) 052070 http://iopscience.iop.org/article/10.1088/1742-6596/635/5/052070/meta http://scitation.aip.org/content/aip/journal/jap/118/10/10.1063/1.4930033 |
| Description | Szeged |
| Form Of Engagement Activity | Participation in an activity, workshop or similar |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Professional Practitioners |
| Results and Impact | Annual Congress of the Hungarian Physical Society. Receipt of the award of an Honorary Fellowship of the Roland Eotvos Physical Society of Hungary. |
| Year(s) Of Engagement Activity | 2016 |
| URL | http://titan.physx.u-szeged.hu/fizikus_vandorgyules_2016/node/6 |