Active elimination of radio frequency interference for improved signal-to-noise ratio for in-situ NMR / NQR applications

Nuclear magnetic resonance (NMR - the technology behind magnetic resonance imaging or MRI as used in medical scanning) offers enormous opportunity for materials detection and characterisation in the "real-world": that is open-access, electromagnetically unshielded applications outside of the laboratory where it is necessary to assess the quality, state or presence of materials. These applications include: the minimisation of delays to allow concrete to cure during construction or the assessment of building degradation in the built environment; managed forestry in order to decide which trees to fell or to minimise energy consumption from timber drying during processing; or illicit material detection at secure locations such as airports; and down bore-hole logging for oil and gas well exploration. However, save oil and gas exploration, where the earth's crust provides a natural electromagnetic shield, external radio frequency interference (RFI) pick-up restricts materials detection limits using affordable and practical light-weight, low-field strength magnets and hence inhibits the technology being taken up widely by industry. The problem is unwanted pick-up of radio signals such as aeronautical communications and amateur radio. The pick-up dominates and masks the weak NMR signals coming from materials to be inspected in open-access detectors.

It is the purpose of this proposal to address RFI pick-up head on. We propose a new method to eliminate pick-up called active RFI suppression. We will build a technology demonstrator for active RFI suppression in an open-access NMR system. Our target is a greater than 10 times improvement in the signal-to-noise ratio, sufficient to enable take-up in construction, forestry and homeland security.

The project takes advantage of recent rapid developments in real time signal processing and radio frequency engineering emanating from the mobile communications industry that enable modern devices to process radio signals in real time at the carrier frequency. With these advances we are able to measure the RFI pick-up independently of the NMR signal. Hence we can eliminate the pick up from the NMR signal. The team assembled for the project uniquely comprise experts in NMR techniques and applications and applied radio frequency electronic engineering. The project builds on an RFI characterisation and software feasibility study carried out jointly with Dstl during 2014 and our own experience of using NMR in construction and forestry both in the laboratory and outside in the "real-world" on construction sites and in forests. Dstl remain involved and contribute through support for an engineering doctorate research student, the provision of technical hardware on which to build the demonstrator and detailed knowledge of security applications.

Overcoming RFI detection limits will greatly increase the sensitivity of NMR used for the detection of explosives and narcotics e.g. at airports enabling a combination of improved false positive and false negative detection rates, lower scanning time and smaller detection limits. In principle active RFI suppression is a generic procedure that improves the signal-to-noise ratio without the specificity of hyperpolariation and / or field cycling methods more suited to specific explosives or narcotics. We will collaborate beyond the project lifetime with Dstl and instrumentation manufacturers to bring this opportunity to fruition.

For cements, our research group has Impact Acceleration Account (EPSRC) funding to work with NPL, a consortium of instrumentation manufacturers and cement manufacturers and engineering end users to develop an international standard protocol and reference materials for NMR characterisation of cement based materials as well as low-cost, in-situ, portable instrumentation upon which it can be implemented. Overcoming RFI will offer opportunity to greatly increase take-up of the technology in the construction sector. Two key applications are envisaged: minimisation of delays during construction due to concrete curing (strength build up) and assessment of degradation (water permeation) repair requirements in the built environment. Current in-situ tests for both are poor; neither is adequately addressed. A plan exists to secure on going business development funding with SME instrumentation manufacturers, engineering consultancies and cement producers to bring this about.

In forestry, the use of NMR / MRI for active management and minimisation of energy consumption during processing (drying) of high-value hardwood forest products is not pie-in-the-sky. The industry already uses X-ray CT post-processing of the wood for timber product optimisation purposes. It is used post-processing as drying removes water and increases X-ray contrast. NMR is sensitive to water and can be used pre-processing to achieve the similar results without incurring the cost of first drying low grade wood. A key goal is to be able to predict warping of wood during the drying process. Removing wood prone to warping pre-drying would result in significant financial saving (heating costs). A second goal is to put periodic selection of hardwood trees for felling (thinning of the forest) on a scientific footing. We already collaborate with Forest Research and through them have plans to access networks of timber industry companies to progress the take-up of NMR to higher technology readiness levels.

These three sectors, amongst others, can be expected to take up open access NMR much more widely, and hence make significant financial and safety gains, with the improvements in NMR sensitivity expected from this programme.

We have plans for engagement throughout the project with University of Surrey Business Development and Technology Transfer teams to identify any exploitable outputs. We have plans to hold an end-of-project open workshop for potential end-users. We have plans to create on-line video dissemination materials.