Portable X-band system for solution state dynamic nuclear polarization

Armstrong, Brandon D.; Lingwood, Mark D.; McCarney, Evan R.; Brown, E. R.; Blümler, Peter; Han, Songi

doi:10.1016/j.jmr.2008.01.004

Cited by 69 publications

(57 citation statements)

References 25 publications

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“…[12] improved the quality by roughly an order of magnitude in the yz-plane but it essentially stayed the same in 3D (15). The stacking of the individual rings in the x-direction according to Table 4 and the use of polygonal magnets at least for the innermost ring dramatically improved the homogeneity in 3D to about 200 ppm over 5 mm DSV, which could further be enhanced to about 20 ppm by passive shimming with m-metal strips (14).…”

Section: Realizationmentioning

confidence: 90%

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Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Soltner¹,

Blümler²

2010

Concepts Magnetic Resonance

114

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NMR Mandhalas (Magnetic Arrangement for Novel Discrete Halbach LAyout) are arrays of identically shaped magnets in a Halbach-type arrangement. They provide a simple and cost-effective way to generate high magnetic fields for mobile applications, for example, in magnetic resonance. Based on the introductory publication by Raich and Blü mler (Concepts Magn Reson 2004;23B:16-25), we extend the notion of Mandhalas from cube-shaped magnets to polygonal and cylindrical ones and present construction guidelines for the stacking of such rings to generate homogeneous magnetic fields over larger volumes. For this purpose, we present formulas and numerical values based on a dipole approach to calculate the flux density of single rings and composed 3D systems and compare to corresponding results obtained by 3D boundary element method calculations. As an application of the approach presented here, we constructed prototypes.

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Section: Realizationmentioning

confidence: 90%

“…Other advantageous features of Halbach magnets for magnetic resonance are that they can be easily nested and rotated to generate homogeneous sources of variable magnetic fields (12,14,15) and even be hinged to be opened without force (16,17). (18), (e) wedge design (11).…”

Section: Introductionmentioning

confidence: 99%

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Soltner¹,

Blümler²

2010

Concepts Magnetic Resonance

114

View full text Add to dashboard Cite

show abstract

“…Two of such cylinders are nested and can be rotated relative to each other, in order to adjust the transverse magnetic field between 0.1 and 0.468 T. The homogeneity is better than 100 ppm over a spherical volume with 10-mm diameter. More details on similar magnets can be found elsewhere [21,22].…”

Section: Magnetsmentioning

confidence: 99%

A Mobile DNP Polarizer for Continuous Flow Applications

et al. 2012

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Despite its wide applicability in natural sciences, nuclear magnetic resonance (NMR) still suffers from its inherently low sensitivity. This could be overcome by hyperpolarization of molecules via dynamic nuclear polarization (DNP). Here, we introduce a substantial improvement of a mobile Overhauser DNP polarizer, based on an inexpensive Halbach magnet operating at 0.35 T. It shows an almost vanishing magnetic flux at its outer side and does not disturb other instruments. It can be placed directly next to a superconducting magnet, thus reducing the transport time of the hyperpolarized liquid. However, two problems for DNP applications remain. Firstly, radicals are needed which are often toxic. This problem becomes crucial with regard to medical applications. Secondly, the sample must be transported from the polarization magnet to the place of detection like a magnetic resonance imaging (MRI) scanner, and polarization losses due to T 1 relaxation may occur. We have implemented a flow system into the mobile DNP polarizer, which overcomes both obstacles. The radicals are immobilized in a gel matrix and the hyperpolarized radical-free fluid is subsequently directly pumped into the MRI scanner. It is shown that even at flow conditions, the NMR signal is enhanced due to Overhauser DNP in the Halbach magnet as well as in the MRI scanner (4.7 T) at a distance of 1.4 m. Acquired images demonstrate the use of enhanced and, due to dipolar coupling, inverted NMR signals, which provide an excellent MRI contrast even for small enhancements.

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“…The permanent magnet system consists of two coaxially nested discrete Halbach dipoles [9,10] which can be rotated relative to each other to mechanically adjust the strength of the magnetic field inside [11][12][13]. Figure 1 shows the design schematically; the permanent magnet is made of two concentric ''towers'' of which the inner is fixed and the outer can be mechanically rotated around it.…”

Section: Magnetsmentioning

confidence: 99%

“…The magnetic material is glued into sockets milled out of supporting aluminum rings. The layout of the magnet is identical to the one described elsewhere [12] in more detail. The entire magnet system with support weights about 57 kg and has an outer size of 350 9 330 9 320 mm.…”

Section: Magnetsmentioning

confidence: 99%

Overhauser DNP and EPR in a Mobile Setup: Influence of Magnetic Field Inhomogeneity

et al. 2012

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Power-dependent Overhauser dynamic nuclear polarization (DNP) enhancements and continuous-wave electron paramagnetic resonance (EPR) spectra of nitroxide radicals were measured in the magnetic field of a mobile Halbach-array permanent magnet and compared with results from a commercially available electromagnet. DNP saturation factors for varying microwave power were obtained from both measurement series and used to investigate how the increased magnetic field inhomogeneity present in the Halbach magnet affects the saturation efficiency. An EPR detection system was designed to allow continuous-wave EPR measurements at microwave power up to 20 W. Our results show that despite the lower magnetic field homogeneity, a Halbach-array magnet can be used for EPR and DNP-enhanced nuclear magnetic resonance of high quality providing almost the same performance as a more homogeneous electromagnet.

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Portable X-band system for solution state dynamic nuclear polarization

Cited by 69 publications

References 25 publications

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

Dipolar Halbach magnet stacks made from identically shaped permanent magnets for magnetic resonance

A Mobile DNP Polarizer for Continuous Flow Applications

Overhauser DNP and EPR in a Mobile Setup: Influence of Magnetic Field Inhomogeneity

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