Superconducting instruments

Science Foundation. Several large superconducting instruments were being installed when a government safety inspector appeared and demanded to know what provisions were being made to handle the nuclear waste produced by these instruments. Assume you are the manager of the NMR center, and offer an explanation that could be understood by a nonscientist. 

The problem of reliable structural materials for use at low temperatures has recently become topical. Progress in space research, storage and transportation of liquefied gases, superconducting electrical machinery, and superconducting instrument production requires new structural materials serviceable at long exposures to extreme conditions of operation without deterioration of their physical and mechanical properties. Only some aspects of the development of cryogenic materials science in the USSR are mentioned in this paper, and these have been carried out at the Physico-Technical Institute of Low Temperatures of the Ukrainian Academy of Sciences in Kharkov. 

In Fig. k is shown the 90 MHz C-13 spectrum of free radical polymethyl methacrylate, the same as that in Fig. la. A superconducting instrument was employed, operating at 360 MHz for protons. Spectrum (a) shows all the resonances because of the large (ca. l60 ppm) range of chemical shifts, the spectrum is necessarily rather compressed. Tne u-methyl resonance (ca. 17-22 ppm, referred to tetramethylsilane as zero) is split into triads with pentad fine structure not discernible on this scale. 

NMR instrumentation consists of three chief components a magnet, a spectrometer console, and a probe. While in the past much solid state NMR research was conducted on home-built equipment, the current trend is toward the acquisition of commercial systems. The magnets used for solid state NMR applications generally are superconducting solenoids with a cylindrical bore of 89-mm diameter. The most common field strengths available, 4.7, 7.0, 9.4, and 11.7 Tesla, correspond to proton resonance frequencies near 200, 300, 400, and 500 MHz, respectively. 

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. 

The author is grateful to Mr. H. Horiuchi for the preparation of photoelectrochemical cells. Professor S. Yamada for discussion, and Professor Y. Tanimoto and Associate Professor Y. Fujiwara for using the superconducting magnets. The author also thanks The Center of Advanced Instrumental Analysis, Kyushu University, for H-NMR measurements. This study was financially supported by the Grant-in-Aids for Scientific Research Priority Areas (Area 767, No. 15085203) and (Area 432, No. 17034051), Scientific Research (C) (No. 17550131), and twenty first century COE Program Function Innovation of Molecular Informatics from M EXTof the Japan. 

Cryoshims Rough (superconducting) shim coils that are built into superconducting magnets and adjusted at installation of the instrument. 

A mass calibration for FTICR analyzers with superconducting magnets is very stable and is valid for many days for normal applications. Mass accuracy < 1 ppm can be obtained over a fairly wide mass range. Unique elemental composition can be determined for masses over 800 Da [262]. Recently, 0.1 ppm mass accuracy, which required a mass resolving power >300,000, has been achieved for several thousand peaks by a 14.5 T instrument [263] and commercial instruments with mass accuracy <0.2 ppm are available. As with the orbitrap (see Section 2.2.5) the frequency is... 

Gemini Superconducting Fourier transform NMR systems, VXR series 5, Varian Instruments, Sugar Lane, Texas, USA... 

The basic components of the traditional NMR instrument therefore include a large-capacity superconducting magnet, a sample holder, an RF transmitter, an RF receiver/detector, a sweep generator with... 

Fig. 4.54. Ion transfer optics and differential pumping stages to adapt an ESI source to an FT-ICR instrument. Only the ICR cell is inside the superconducting magnet. By courtesy of Bruker Daltonik, Bremen.

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