Tuning and matching
CryoProbe User Manual BRUKER 47 (107)
Tuning and matching 4.12
0
IMPORTANT: A CryoProbe must not be tuned or matched when warm because
the properties of the RF circuits are quite different when cold. No resonance may
be visible at ambient temperature.
Before attempting to tune and match a CryoProbe, the green C
OLD light should be
on or at least flashing. It indicates that the temperature is sufficiently low for a
meaningful and persistent adjustment.
Tuning and matching settings are reproducible after a warm-up/cool-down cycle.
They are not more susceptible to a change of solvent than in conventional probes.
Wobbling
The wobbling feature is handled by the ‘warm’ preamplifiers inside the HPPR
CRP instead of the built-in CryoPreamps. Therefore, the RF pathway to these
preamplifiers must be configured with special X
WIN-NMR commands.
t.9 Wait until the sample has equilibrated again (~1h) and write down its
actual temperature as .
NOTE: If the sample temperature would fall below -20°C even with the
VT heater being active, an automatic security warm-up of the Cryo-
Probe will be started. If this happens, switch O
FF the BCU05 and
increase the VT heater power limit carefully. When ,
press
COOL-DOWN to re-establish cold operation of the CryoProbe.
NOTE: The VT hose must not be covered with ice at the point where it
enters the CryoProbe body. If the CryoProbe body is cooled by the VT
gas and becomes wet with condensed water, the hose must be extend-
ed. Since the VT gas flow must never be interrupted while the Cryo-
Probe is cold, a warm-up to ambient temperature is needed before the
hose can be exchanged.
Table 4.9. How to wobble the CryoProbe
step action
w.1 Configure nuclear frequencies and routing in edasp as usual.
For wobbling
2
H, one channel must be set to 2H and routed via a suit-
able X-amplifier to the 2H preamp module.
w.2 To wobble
- all channels incl.
2
H (recommended),
enter locnuc off, crpwobb and wobb,
- all channels except
2
H while the lock is operating,
enter crp2hon, and wobb.
w.3 Tune and match with the Tuning Adapter, see next paragraph.
w.4 When tuning and matching is done, enter stop, locnuc 2H, ii
and crpon.
T
min, BCU05
T
sample
-20°C>
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