John L. (Iain) Campbell
University Professor Emeritus
Telephone: 519-824-4120 x52325
Office: MacN 326
Lab: MacN 012 Lab Extension: 58397
Degrees & awards
- BSc in Physics, University of Glasgow, 1963
- PhD in Physics, University of Glasgow, 1967
- DSc, University of Glasgow, 1982
- DTech (honorary degree) University of Lund, Sweden, 1997
- Queen’s Golden Jubilee Medal, 2003
- University of Guelph Medal of Merit 2010
- JARI Medal (Elsevier Publishing) 2014
Atomic inner-shell processes; X-ray spectroscopy; fundamental parameters for X-ray emission analysis; applications of ion beams from accelerators; development of proton-induced X-ray emission (PIXE) and PIXE software for elemental analysis and imaging; development of fundamental parameters approach for in situ X-ray emission analysis of Martian rocks and soils for elements and water.
I have spent one-year leaves at the Max Plank Institüt fur Kernphysik in Germany and at the UK Atomic Energy Authority’s Harwell Laboratory. Shorter research assignments abroad were at the University of the Witwatersrand in S. Africa and the French Bureau de Récherches Géologiques et Minières. I have presented two-day training schools on the use of our PIXE software package at the Louvre Museum in Paris, the University of Florence, the Max Planck Institüt in Heidelberg, and the University of Madrid. I am a regular speaker at international conferences on applications of accelerators in pure and applied physics and in X-ray Spectrometry: the proceedings of two such conferences were dedicated to me in recognition of my contributions. I am a member of the X-ray Fundamental Parameters Initiative launched recently by the French and German National Standards labs and the European X-ray Spectrometry Association. Presently I am a co-investigator on NASA’s Mars Science Laboratory mission.
Major Research Achievements
Two examples are noted:
- The computer software package GUPIX developed by my group on the basis of our experience in PIXE and its underlying physics has been supplied to over 150 ion beam analysis laboratories in 33 countries. This fundamental parameters approach to PIXE analysis has become the most widely adopted PIXE software. A recent Google search showed 12700 hits. Our three successive GUPIX publications have attracted 846 citations in ISI.
- In 2008, we reported the first quantitative in situ determination of water by an instrument on the Martian surface. A new approach to the photon scatter peaks in the spectra from the alpha-particle X-ray spectrometer on the Spirit rover measured water contents of up to 15% in the bright high-sulphur Paso Robles soils in the Columbia hills.
Present Research Activities
Fundamental research focuses on creation and de-excitation of core vacancies in atoms, using particle and photon beams, radionuclides and X-ray spectroscopy. Interests include natural widths of core levels, X-ray transition rates, satellites, multiple ionization, chemical bonding effects, fluorescence and Coster-Kronig probabilities. New work on a PIXE approach to testing X-ray attenuation coefficient databases was launched recently, stimulated by the workshops of the X-ray Fundamental Parameters Initiative. Our X-ray spectroscopy work is supported by continuing studies of the properties and response of Si(Li) and SDD X-ray spectrometers.
Applied research is partly based on the Guelph Micro-PIXE Facility, which provides elemental analysis and imaging on a wide variety of sample types. We continue to refine, test and develop our GUPIX software, which is a powerful tool used worldwide to fit PIXE spectra and derive element concentrations. A new tool GUMAP is near completion. Work has started in use of the facility for support of the Martian APXS project described below in (3). Equivalence between APXS analyses of geo-standards and accelerator-based PIXE analyses offers us the potential for a deeper examination of the accuracy of the PIXE component of APXS across a wide range of terrestrial rock types that emulate Martian ones.
In situ analysis of Martian rocks and soils with the ‘alpha particle X-ray spectrometer’ is done in collaboration with Prof. Ralf Gellert who is the lead scientist for both the MER APXS (Spirit and Opportunity rovers) and the MSL APXS (Curiosity rover). APXS employs two X-ray excitation&emission methods - PIXE and XRF – to excite the elements in these samples.
Based on GUPIX (see (2) above) we have created a new fundamental parameters-based code GUAPX to process the rock and soil spectra recorded on Mars by the APXS. Our 2012 paper on calibration of the MSL APXS using terrestrial geochemical reference materials revealed anomalies in the results for the light elements examined by the PIXE branch. Subsequent XRD work has provided a quantitative explanation of these ‘mineral phase effects’; this work continues. A new project described in (2) above uses accelerator-based PIXE analysis of reference materials to extend our understanding of what APXS really measures in different rock types classified by the TAS diagram.
- Mineral-bound water on Mars: We have developed a new method (mentioned above) which employs the photon scatter peaks in the APXS spectra to deduce the presence of elements whose atomic number is too low for them to be detected via their X-rays. This enabled us to make the quantitative in situ determinations of bound water content in the Paso Robles soils at Gusev crater. Considerable effort is now being devoted to refining this technique, and it is being used on the MSL mission.
See Campbell website: http://pixe.physics.uoguelph.ca/