Bruker BioSpin Solid State NMR, User Manual

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48 (327) BRUKER BIOSPIN User Manual Version 002
General Hardware Setup
Figure 3.38. Parallel Coil to Shift the Tuning Range to Higher Frequency
This additional coil is electrically connected in parallel to the detection coil. Since it
is connected behind the proton trap, the proton channel is not influenced, but as
well the X and Y channel will be affected, because only part of the inductance is
now filled with sample. A parallel coil therefore reduces the RF efficiency quite
substantially. The losses increase as the inductance (size and number of turns) of
the parallel coil decreases. A coil of the same inductance as the detection coil will
cost 50% in S/N and pulse voltage. Usually, these coils introduce about 30% loss.
Adding a Frequency Channel to a Probe (WB probes only) 3.7.3
Probes are produced as single channel, double (channel), triple or quadruple
probes (1, 2, or 3 RF connectors on the probe). It is not possible to modify a probe
produced as a double channel probe into a triple probe, but a triple probe may be
used as triple or double probe. As multiple tuning will reduce the RF performance
of a probe on the other channels (if they are part of the same RF network), it is
better to remove an unused RF channel, if this is possible.
The usual case is triple probes or quadruple probes. A triple probe can be tuned
to
1
H, X and Y (where X is the higher frequency, Y is the lower frequency, both in
the X-nuclei range). A triple probe X/F/H only has 2 RF connectors, because 1H
and 19F are tuned to the same RF connector simultaneously. Likewise, a quadru-
ple probe is an X/Y/F/H probe, with the X channel tuned to X and Y, and the pro-
1. X-Tuning cap
2. Parallel coil 3. Proton reject filter („trap“)
4. Probe ground