Probe single coil

Some MAS probes are single-coil, allowing proton-only acquisition, and some are dual-coil, allowing the acquisition of 2-D proton-carbon data. Note that MAS probes can be used for ordinary solution work and though very labour-intensive to use, can give excellent sensitivity where the available compound is limited and signal to noise is at a premium. 

NMR. The CP/MAS spectra were obtained on a single coil, double-tuned probe similar in design to that reported earlier (15) but modified (16) for the electromagnet of the Varian XL-100-15 system. A homebuilt receiver system allows single coil operation. The probe uses a D2O external lock and a special rotor and stator assembly design to provide MAS. The carbon-13 (25.16 MHz) and the proton (100.06 MHz) radio frequency fields are 17 G and 12 G, respectively for 90 watts of power. The H spin locking pulse of 90° may be varied in terms of length and amplitude while the amplitude of the - C irradiation can be controlled to within 0.1 db to match the Hartmann-Hahn (17) condition. The isolation between the two channels is in excess of... 

The probe uses a single-coil for 20 mm spinning samples at room temperature. There are no tuning elements in the probe -- rather the tuning is by a variable inductor at the end of a A./4 cable as described in the discussion of quarter wave cables in V.C.8. The transformer at the end of the second quarter wave cable matches the impedance between the tank circuit and the broadband preamplifier. The output... 

With variable inductors or capacitors of sufficient range, it is possible to make a multinuclear probe which can be converted from one frequency to another merely by changing coils wound on inserts. For single coil probes such inserts can be changed conveniently by modifying commercial rf connectors, for example, BNC, and attaching them to the ends of the inserts. 

We now give an example of a homebuilt probe used in the spectrometer described in section V.C.2. It is a single coil probe with an impedance matching network built in. It is built in an enclosure made from a sawed off section of an aluminum extrusion supplied by Pomona. Its exterior dimensions are 68x105 mm and thickness 40 mm (including two cover plates each of 3 mm thickness). Each cover plate is screwed on to the main body with 8 screws. A sketch of it follows. 

K. E. Kisman and R. L. Armstrong, "Coupling scheme and probe damper or pulsed nuclear magnetic resonance single coil probe," Rev. Sci. Instrum. 45, 1159-1163 (1974). 

The most common single coil duplexers are designed with cables of appropriate lengths such that the receiver is at the wrong electrical distance from the transmitter to see the transmitter signal while the probe is at the right distances from both the transmitter and the receiver (Lowe and Tarr, 1968). 

R. A. McKay and D. E. Woessner, "A simple single-coil probe for pulsed nuclear magnetic resonance," J. Sci. Instrum. 43, pp. 838-840 (1966). 

For a single coil probe, the receiving function and the transmitting function should be optimized simultaneously if the rf circuits were designed correctly. However, for a surprising number of spectrometers, the adjustment which yields the... 

This feature of the field is sometimes used in order to control the quality of an induction probe consisting of coils and wires. In the case when the magnetic field is created by one single coil, the points where the component Hz vanishes are easily calculated. 

It is obvious that for given frequency, conductivity, and magnetic permeability this behavior takes place for shorter probes with higher accuracy. Correspondingly, in order to reduce the influence of conductivity, it is appropriate to apply relatively short induction probes, in particular, single-coil arrays. However, in this case we can expect an increase of the influence of borehole radius, caverns, and eccentricity. As is well known, the relation between magnetic permeability and susceptibility in Gauss system is ... 

A single cell layer of an excised piece of onion epidermis was selected as a test object for this micro-coil, (Figure 2.1.14), and an imaging experiment was carried out, similar to the one by Mansfield et al., who used a laboratory-made micro-coil probe and gradient system [31]. Other micro-coil types, e.g., volume coils or coils that are immersed into the objects, can be adapted to specific applications and mounted on commercial imaging probes. 

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