Spectrometer superconducting magnets

In high-frequency spectrometers, superconducting magnets are used. Up to 100 GHz, the microwaves... 

Figure Bl.l 1.2. Simplified representation of an NMR spectrometer with pulsed RF and superconducting magnet. The main magnetic field Bq is vertical and centred on the sample.

Fig. 3. A block diagram schematic representation of a Fourier transform nmr spectrometer, ie, a superconducting magnetic resonance system.

Flexible superconducting tapes provide promise of uses for superconductors in motors, generators, and even electric transmission lines. Meanwhile, superconducting magnets cooled to the temperature of liquid helium already are in use. High-field nuclear magnetic resonance (NMR) spectrometers have become standard instruments in chemical research laboratories, and the same type of machine (called an MRI spectrometer) is used for medical diagnosis in hospitals worldwide. 

NMR spectrometers have improved significantly, particularly in the present decade, with the development of very stable superconducting magnets and of minicomputers that allow measurements over long time periods under homogeneous field conditions. Repetitive scanning and signal accumulation allow H-NMR spectra to be obtained with very small sample quantities. 

Figure 1.6 A 500-MHz NMR spectrometer (Bruker AMX 500). The console is the computer-controlled recording and measuring system the superconducting magnet and NMR probe assemblies are on the right.

In the conventional NMR system used in chemical analyses, downsizing of the spectrometer alone may not be appealing, unless other parts of the system, such as a superconducting magnet, a power amplifier, etc., are also miniaturized. On the other hand, the small-sized spectrometer would find interest in various unconventional scenes. In this section, we show examples of such. 

Figure 16 shows an NMR system based on the bulk high-temperature superconducting magnet and the OPENCORE NMR spectrometer, in which 1H NMR in water was performed in 4.7 T. 

Figure 16 An NMR system using a bulk high-temperature superconducting magnet and the OPENCORE NMR spectrometer. The temperature of the bulk SCM was 40 K, while the sample space with a diameter of 24 mm was at room temperature. On the computer screen displayed is a hi FID of water taken on this system. The resonance frequency was 200.045 MHz.

For cls-polyisoprene and cis polybutadiene, the interpretation is based on Ti, NOE and T2 values ( W) although utilization of T2 is complicated because of the possible presence of systematic errors particularly in spectrometers employing superconducting magnets. The interpretation for PE and to a lesser extent PIB is not unique. Several choices of segment length are possible and the parameters listed in Table V are for a minimum length which... 

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