Novel NMR methodologies using DC SQUIDs applied to fundamental condensed matter physics and biodiagnostics

Lead Research Organisation: Royal Holloway, University of London
Department Name: Physics

Abstract

The ability to probe the incredibly weak magnetism that results directly from nuclear spin is one of the wonders of physics, discovered in the middle of the last century. It relies on the fact that a nucleus will precess like a top in an applied magnetic field, at a rate that is species specific. In a MRI hospital magnet (typical field 1.5 T) the protons in the patient's body precess at around 60 MHz. This project relies on the use of Superconducting Quantum Interference Devices (SQUIDs), which operate as exquisitely sensitive flux to voltage transformers, to either measure still weaker signals from systems with low spin density or to perform spectroscopy and imaging in the Earth's magnetic field or lower. This work combines the technical challenge of building instruments, which open up a new domain for NMR, with new science. This new science ranges from fundamental low temperature physics to new applications for biological and medical diagnostics. Superfluidity is a state of matter that is characterised by the entire fluid being described by a macroscopic wavefunction. The lighter isotope of helium, helium-3, becomes superfluid when helium quasi-particles form pairs, at 0.94 mK for helium under its own vapour pressure. In 3He the pair diameter is around 70 nm at zero pressure. The aim of this project is to confine the superfluid in a cavity where the height is tuneable through the use of piezo-electric nanopositioning devices and comparable to the size of the pair. New phases and new physics are predicted to occur as the system is tuned into and through the two-dimensional limit. Predicted is an analogue of the quantum hall effect for transport of nuclear spin. But totally new, unexpected and exotic phenomena are likely to emerge as we enter uncharted territory. Nuclear magnetic resonance (NMR) experiments are sensitive to the phase of the superfluid and so provide the ideal probe with which to study the superfluid properties as a function of cavity height and temperature. The small size of these cavities, 10 -100 nm high, results in tiny signals so the high sensitivity of the SQUID, exploiting recent advances, is necessary for its detection. High resolution NMR spectroscopy and clinical magnetic resonance imaging, MRI, has revolutionised the study of chemical and biomolecular structure and the non-invasive diagnostic ability of the healthcare sector. One limiting factor to the use of these techniques is that the drive to improve performance has been focused on operation in ever higher magnetic fields. These high fields are obtained with sophisticated (expensive and large) superconducting magnets. This precludes the ability of these devices to be mobile, and results in a limited number of specialist facilities. This work aims to develop instruments for NMR and MRI that do not rely on a large superconducting magnet. The high, frequency independent, sensitivity of SQUIDs coupled with mechanisms to overcome the low intrinsic thermal polarisations in low fields means that operation in microtesla fields produced by simple magnets is possible. The long term aim is to couple SQUID based microtesla NMR/MRI instruments with cryogen free operation. More compact, cheaper, and mobile instruments, coupled to new imaging and spectroscopy techniques in the low field regime are expected to significantly extend the impact of the NMR method for analysis and a wide range of biodiagnostics. High spectral resolution, low field NMR spectroscopy offers the possibility of relating spin-lattice relaxation times, T1, to physical properties such as porosity. This could be exploited in the characterisation of bone porosity, used in the diagnosis of osteoporosis. The couplings between nuclei of different species result in a field independent frequency shift of the NMR signal that is sensitive to molecular conformations (the distance and angle between bonds) and has the potential to provide a sensitive detector of biomolecular interactions in vivo

Publications

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Dimov S (2010) Anodically bonded submicron microfluidic chambers. in The Review of scientific instruments

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Dimov S (2009) Decoupling of Confined Normal 3He in Journal of Low Temperature Physics

 
Description Developed a methodology for confining a superfluid in a box where one of the dimensions was the size of the Cooper pair that makes up the superfluid. This confinement provides a new tool for modifying the phase diagram of the superfluid and opens up the possibility of engineering devices that rely on the superfluid properties of 3He.
Exploitation Route Now we have control on the superfluid order parameter, we (or others) can fabricate a new class of device which may exploit the topological nature of the surface states of superfluid helium-3.
Sectors Healthcare,Manufacturing, including Industrial Biotechology,Security and Diplomacy

URL https://www.royalholloway.ac.uk/physics/research/condensedmatter/quantumfluidsandsolids/quantumfluidsandsolids.aspx
 
Description The primary purpose of this project is fundamental research on superfluidity, using superfluid 3He. A significant and wide impact in the shorter term derives from the recognised importance of research on matter under extreme conditions, in particular low temperatures. Developing capability in this sector, and enhancing measurement technique, metrology and instrumentation, is a key feature of this research, and we have contributed in several ways. This impact has been achieved through close collaboration with the industrial sector (primarily Oxford Instruments Nanoscience) and National Measurement Institutes, and was the subject of an Impact Case Study to REF2014. This study was highlighted in the Institute of Physics 2015 publication "Inspirational physics for a modern economy, http://www.iop.org/publications/iop/2015/page_65902.html Joint research with Oxford Instruments on cryogen-free microkelvin technology was subsequently highlighted at a special session at the APS March meeting in 2015. Progress on noise thermometry was featured at a Royal Society meeting at Chicheley Hall in May 2015, "Towards implementing the new kelvin", a project involving collaboration across National Measurement Institutes in the EU.
First Year Of Impact 2009
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic,Policy & public services

 
Description EPSRC
Amount £1,140,435 (GBP)
Funding ID EP/J022004/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 10/2012 
End 09/2016
 
Description Institute of Physics Low Temperature Techniques Course 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Postgraduate students
Results and Impact The purpose of the meeting is to disseminate best practice and raise awareness of new innovations in low temperature techniques and thermometry to each new national cohort of PhD students and postdoctoral researchers embarking on a research career at low temperatures. In addition we raise the awareness of how those skills can be employed in an industrial environment. Each year the event is attended by around 50 delegates (mainly 1st year PhD students, occasionally international), the students report a raised awareness and begin to create the support network with each other and the speakers at the event that will help them during there career. The event is organised and chaired by: Dr. Andrew Casey (with support from the IOP) Dr. Andrew Casey and Dr. Jan Nyeki both give presentations at the event. The event is supported by an annual grant from the IOP Low Temperature group of £1000, which is used to reduce the cost of attendance. The event is publicised by the IOP through it's website and newsletters. An e-version of the material presented is distributed to all of the delegates.
grant from the IOP Low Temperature group of £1000, which is used to reduce the cost of attendance. The event is publicised by the IOP through it's website and newsletters. An e-version of the material presented is distributed to all of the delegates.
Year(s) Of Engagement Activity 2009,2010,2011,2012,2013,2014,2015
URL https://www.iopconferences.org/