Positive Ion Mass Spectrometry (PIMS) – The next generation in radiocarbon analysis

Overview

Accelerator mass spectrometry (AMS) is one of the largest analytical tools used in the world with some systems as big as a nine-story building and covering an area of half a football field. Over the past 40 years of development they have become more compact, however they still ultimately rely on the use of a particle accelerator. Positive ion mass spectrometry (PIMS), invented at the Scottish Universities Environmental Research Centre (SUERC), is the first system to perform as well as AMS but without the use of a particle accelerator with just 4 years of development.
This compact system has some distinct advantages over AMS:
• The compact and easy to use system can be used by any department or company rather than specialist laboratories or national facilities.
• The powerful electron cyclotron resonance ion source (ECRIS) enables automation of sample preparation, thereby further simplifying the process and opening the technique up to new areas of science which just were not feasible with AMS

Radiocarbon (14C) is the most commonly measured isotope and has cross-disciplinary applications in Physics, Earth, Environmental, Biomedical, Pharmaceutical and Archaeological sciences. SUERC’s primary interest is in environmental applications such as dating global environmental change, landscape erosion, deglaciation, or tracing sources of pollution, methane sources, CO2 mapping, etc. Radiocarbon’s largest application, however, is pharmaceutical where it is used as a biological tracer, for example 14C-enriched labelling of developmental drugs.

With such wide ranging application this next generation analytical technique will create future opportunities across many different areas of research. Because PIMS development is in its early stage, there is a unique opportunity to become a leader in an emerging field.
The key areas of PIMS development that will push the boundaries of this analytical technique are:
1. Radio-frequency (RF) plasma ion sources: The ECRIS has limited understanding in use for mass spectrometry, development is needed to improve memory between samples, efficiency, creating aluminium beams for 26Al dating.
2. Ion beam transport physics: Through computational modelling and direct measurement better understanding of how to transport the largest ion beam current used in mass spectrometry.
3. Particle beam matter interaction: The ion beam is cleaned of interferences in the patented reaction cell. The physics of how the particles collide with a target material to destroy molecules and exchange charge states will be studied.

The University has already licenced the IP to two companies who have worked with us to develop the first PIMS. One of these companies is a CASE partner and will provide real industrial experience and collaboration.

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Image Captions

Picture 1.jpg – “(left) Multi-Cathode Source of Negative Ions by Caesium Sputtering (MC-SNICS) to produce ion beams from cosmogenic nuclide samples, (middle) 5 million volt accelerator to break up molecular interferences, and (right) positive mass spectrometry (PIMS) ion source.”

Picture 2.jpg – “High intensity particle beam interacting with residual gas as it enters and exits the reaction cell.”

Methodology

Research will be performed on the £2M PIMS prototype installed at SUERC, which is currently the only place in the world where this work can be done.
The PIMS machine uses a cutting-edge Pantechnik Microgan ECRIS. This ion source will be modified by developing new liners to create an inert surface inside the source, without compromising the complex electromagnetic interactions. The plasma source typically operates on gas samples, however, to analyse more species, it will be important to deliver liquids and solids. Existing techniques for bulk samples, such as the thermal evaporation of solid material directly into the ion source, will be developed for discreate samples.

Ion beam modelling, for example using IBSimu or SimIon, will be used to understand the limits of the ion beam transport and how to modify optics for improved operation. Beam profile monitors will be used to analyse the beam and, when necessary, new emittance diagnostics will be developed.

The key component of the PIMS invention is the reaction cell which is used to purify the ion beam. The complex interactions between the ion beam and the cell medium must destroy molecules without degrading beam quality and convert as much of the beam negative as possible. This will be studied by investigating the qualities of the different gasses and modifying the properties of the gasses.

Project Timeline

Year 1

Refining key research questions and establishing hypotheses; accelerator mass spectrometry skills, and PIMS skills; ECRIS skills; ion beam simulation; ECRIS modification designs; reaction cell simulation and hypothesis; PhD progression presentation.

Year 2

ECRIS optimisation; Aluminium investigation; reaction cell optimisation; data analysis; statistical modelling; presentation at national conference.

Year 3

Continues machine optimisation; further data analysis; lead authorship of key manuscript(s); presentation at international conference (e.g. AMS15/16);

Year 3.5

Thesis preparation and write-up, including publications; thesis submission for examination.

Training
& Skills

The skills developed in this project will make the candidate an expert in radiocarbon and cosmogenic nuclide dating, AMS, and PIMS analytical techniques. An in-depth theoretical and practical knowledge of particle beam physics gained in this project will provide the skills to work in any particle accelerator facility in the world. Any one of these skills will create many opportunities for a highly successful research or industrial career. A comprehensive training programme will be provided by the project supervisors who are internationally recognised experts. This training will comprising both specialist scientific training and generic transferable and professional skills. This is a unique PhD opportunity for an analytically minded candidate, offering direct access to unique technologies and providing highly desirable specialist and complementary interdisciplinary skills. Specifically, training will be provided in rare isotope analysis by AMS and PIMS; data reduction; numerical data interpretation and statistical modelling. Training in ion beam optical simulation and modelling required to understand the design and operation or particle beam systems. The student will gain access to University of Glasgow taught courses and NERC run training course depending on skill of the candidate. This is an industrially supported project with NEC (Wisconsin USA). The candidate will have the opportunity to travel to NEC and spend time being trained in various aspect of AMS, PIMS, simulation and practical application in the USA.

References & further reading

Freeman et al. 2015. Radiocarbon positive-ion mass spectrometry. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 361, 229-232.

US Patent No. US 10,128,095 B2

Further Information

Applications: to apply for this PhD please use the url: https://www.gla.ac.uk/study/applyonline/?CAREER=PGR&PLAN_CODES=CF18-7316

 

NEC http://www.pelletron.com
PIMS at NEC http://www.pelletron.com/products/positive-ion-mass-spectrometry-pims-systems/
BBC news https://www.bbc.co.uk/news/uk-scotland-44526368
Richard Shanks: Richard.shanks@glasgow.ac.uk
https://www3.gla.ac.uk/research/az/suerc/staff/shanksrichard/
https://www.researchgate.net/profile/Richard_Shanks
Clayton Magill: C.Magill@hw.ac.uk
https://researchportal.hw.ac.uk/en/persons/clayton-magill
https://www.researchgate.net/profile/Clayton_Magill

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