1. The NMR spectrometer Magnet Probe Coils Transmitters
Amplifiers and pre-amplifiers
Receiver
ADC

2. The NMR spectrometer

3. The Magnet History First magnets were built using
ferromagnetic material=
permanent magnet
Then Electromagnets:
i.e. field was generated by wiring of conducting material
Now: cyomagnets: i.e. electromagnets made of superconducting wire.
A “cutted” magnet

4. Cryomagnets Superconducting wire
has a resistance approximately equal to zero
when it is cooled to a temperature close to
absolute zero ( o C or 0 K) by
emersing it in liquid helium. Once current is
caused to flow in the coil it will continue to
flow for as long as the coil is kept at liquid
helium temperatures.
The length of superconducting wire in the
magnet is typically several miles.

5. Magnet

6. The Probe
The sample probe is the name given to that part of the spectrometer which accepts the sample, sends RF energy into the sample, and detects the signal emanating from the sample.
It contains the RF coil, sample spinner, temperature controlling circuitry, and gradient coils.
Picture an axial cross section of a cylindrical tube containing sample. In a very homogeneous Bo magnetic field this sample will yield a narrow spectrum

7. B0 homogeneity
In a more inhomogeneous field the sample will yield a broader spectrum due to the presence of lines from the parts of the sample experiencing different Bo magnetic fields.

8. The coils You may find one or more RF coils in a probe.
RF coils create the B1 field which rotates
the net magnetization in a pulse sequence.
They also detect the transverse magnetization
as it precesses in the XY plane. Most RF
coils on NMR spectrometers are of the
saddle coil design and act as the
transmitter of the B1 field and receiver of RF
energy from the sample.
The resonant frequency,n , of an RF coil is determined by the inductance (L) and capacitance (C) of the inductor capacitor circuit.
n=1/2p(LC)1/2
RF coils used in NMR spectrometers need to be tuned for the specific sample being studied.