Desktop fast-field cycling nuclear magnetic resonance relaxometer (original) (raw)
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2016 International Symposium on Power Electronics, Electrical Drives, Automation and Motion (SPEEDAM), 2016
The main power supply of a Fast Field-Cycling Nuclear Magnetic Resonance (FFC-NMR) is the key element comparing the performance of different solutions. The power supply is a current source that supplies a magnet being the current controlled in order to perform adjustable and repetitive current cycles. This power supply can be based on different topologies, operating principles and controlled using distinct techniques. If for the final users of this experimental technique the current cycles of the equipment is the core feature, for the developers also the power losses distribution needs to be analyzed in order to develop efficient solutions. In this paper, the power losses and the dynamic behavior of two solutions for the FFC-NMR power supply are compared and discussed.
Fast field-cycling nuclear magnetic resonance spectrometer
Review of Scientific Instruments, 1996
We describe here the design and construction of a modern, state-of-the-art nuclear magnetic resonance ͑NMR͒ field-cycling instrument. Fourier transform NMR spectra of both liquid and solid samples can be measured, and spin-lattice relaxation times (T 1Z ) investigated over a broad range of magnetic field strengths ranging from 0 to 2 T. The instrument is based upon an existing personal computer-based NMR spectrometer ͓C. Job, R. M. Pearson, and M. F. Brown, Rev. Sci. Instrum. 65, 3354 ͑1994͔͒ which has been expanded into a fully computer-controlled field-cycling instrument. The magnetic field cycling is accomplished electronically by utilizing fast switching thyristors and a storage capacitor based on the Redfield energy storage concept. Unique aspects of the design include the field-cycling magnet, which can reach fields as high as 2 T; the personal computer-based NMR spectrometer and associated waveform electronics; and the use of a commercially available pulse width modulation switching current amplifier, having low internal power dissipation and a fast current settling time. Using this new technology T 1Z relaxation times as short as 1 ms can be readily measured.
Renewable Energy and Power Quality Journal, 2020
The temperature distribution of a Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) electromagnet plays an important role in the operation of this type of apparatus. The designed electromagnet presents a reduced volume and is iron and copper based, fulfilling the technical requirements for the magnetic field. With this solution, it is possible to increase the overall performance in comparison with former similar FFC relaxometers. Electromagnet's simulation results evaluating the temperature distribution, heating effects and cooling requirements are presented.
Journal of magnetic resonance (San Diego, Calif. : 1997), 2015
A device for performing fast magnetic field-cycling NMR experiments is described. A key feature of this setup is that it combines fast switching of the external magnetic field and high-resolution NMR detection. The field-cycling method is based on precise mechanical positioning of the NMR probe with the mounted sample in the inhomogeneous fringe field of the spectrometer magnet. The device enables field variation over several decades (from 100μT up to 7T) within less than 0.3s; progress in NMR probe design provides NMR linewidths of about 10(-3)ppm. The experimental method is very versatile and enables site-specific studies of spin relaxation (NMRD, LLSs) and spin hyperpolarization (DNP, CIDNP, and SABRE) at variable magnetic field and at variable temperature. Experimental examples of such studies are demonstrated; advantages of the experimental method are described and existing challenges in the field are outlined.
New Magnet Design for Fast-Field-Cycling Nuclear Magnetic Resonance
IEEE Latin America Transactions, 2013
A new magnet design for fast-field-cycling nuclear magnetic resonance is described. A topic of interest is the compensation of the magnetic field homogeneity during the generation of the pulsed magnetic field. In contrast with previous solutions, the magnet system here discussed can be electronically controlled. In Kelvin-type magnets used today, the homogeneity of the field is setup through a current density distribution along the air-cored cylinders that compose the magnet coil. A common feature of this type of magnets is that the magnetic field value and its homogeneity are affected by thermo-mechanical stress during the strong current pulses applied to the coil. In the new design here presented, the problem can be circumvented through a multicoil arrangement driven by individual current sources, allowing an automatic correction of the magnetic field drift and the homogeneity.
FFC NMR relaxometers on education: Topologies, control techniques and electromagnetic devices
Design of Circuits and Integrated Systems, 2014
The Fast Field Cycling (FFC) Nuclear Magnetic Resonance (NMR) equipment has been mainly developed by engineers with a strong background in power electronics, control and physics. This technique has been widely used by physicists, chemists, biologists, pharmacists and food analysts. During the last decades, the development of this type of apparatus has been taking advantage of the power semiconductors, topologies of the power electronic converters, control techniques, computational tools and materials, among other aspects. In this paper, teaching aspects of using this type of equipment and technique in courses of physics and electrical engineering is described.
Electromagnetic and thermal aspects of a Fast Field Cycling NMR equipment
2015 9th International Conference on Compatibility and Power Electronics (CPE), 2015
The Fast Field Cycling Nuclear Magnetic Resonance (FFC-NMR) technique has been spreading its application to new areas such as oil and food industry. Consequently, new features and improvements concerning the equipment available has been investigated and exploited. Under this context, this paper describes the main aspects concerning the electromagnetic and thermal behavior of the main power supply and the magnet, respectively. The proposed power supply and the magnet were developed under the specifications of the FFC-NMR equipment and in order to match the requirements of the most recent areas of application. The dynamic behavior of the power supply is analyzed based on simulation results, being the thermal study of the magnet performed using finite element method software.
Digital Control of an FFC NMR Relaxometer Power Supply
2020
The fast field cycling (FFC) experimental technique allows to overcome a technical difficulty associated with the nuclear magnetic resonance (NMR) signal-to-noise ratio (SNR) at low frequency spin-lattice relaxation measurements when using conventional NMR spectrometers. Constituting a step forward than the classical analog approaches, in this paper, a digital control system for an FFC-NMR relaxometer power supply was developed. The hardware and software were designed to allow for the modulation of the Zeeman field as required by this technique. Experimental results show that under digital control the system performs fast transitions between the high and low magnetic flux density levels, i.e., the switching times obtained are in the millisecond range, and, assures a good stability of the field during the steady states. Comparative proton relaxometry measurements in two compounds (liquid crystal 5CB and ionic liquid [BMIM]BF4) were made to assess the digital control system performance.
New applications and perspectives of fast field cycling NMR relaxometry
Magnetic resonance in chemistry : MRC, 2015
The field cycling NMR relaxometry method (also known as fast field cycling (FFC) when instruments employing fast electrical switching of the magnetic field are used) allows determination of the spin-lattice relaxation time (T1 ) continuously over five decades of Larmor frequency. The method can be exploited to observe the T1 frequency dependence of protons, as well as any other NMR-sensitive nuclei, such as (2) H, (13) C, (31) P, and (19) F in a wide range of substances and materials. The information obtained is directly correlated with the physical/chemical properties of the compound and can be represented as a 'nuclear magnetic resonance dispersion' curve. We present some recent academic and industrial applications showing the relevance of exploiting FFC NMR relaxometry in complex materials to study the molecular dynamics or, simply, for fingerprinting or quality control purposes. The basic nuclear magnetic resonance dispersion features are outlined in representative examp...
Development of Halbach magnet for portable NMR device
Journal of Physics: Conference Series, 2009
Nuclear magnetic resonance (NMR) has enormous potential for various applications in industry as the on-line or at-line test/control device of process environments. Advantage of NMR is its non-destructive nature, because it does not require the measurement probe to have a contact with the tested media. Despite of the recent progress in this direction, application of NMR in industry is still very limited. This is related to the technical and analytical complications of NMR as a method, and high cost of NMR analyzers available at the market. However in many applications, NMR is a very useful technique to test various products and to monitor quantitatively industrial processes. Fortunately usually there is no need in a high-field superconducting magnets to obtain the high-resolution spectra with the detailed information on chemical shifts and coupling-constant. NMR analyzers are designed to obtain the relaxation parameters by measuring the NMR spectra in the time domain rather than in frequency domain. Therefore it is possible to use small magnetic field (and low frequency of 2-60 MHz) in NMR systems, based on permanent magnet technology, which are specially designed for specific at-line and on-line process applications. In this work we present the permanent magnet system developed to use in the portative NMR devices. We discuss the experimental parameters of the designed Halbach magnet system and compare them with results of theoretical modelling.