Cool-down
CryoProbe Installation BRUKER 53 (93)
When the cool-down has started, "Load additional Xwin-nmr software" on
page 54 and "Put HPPR CRP assembly into operation" on page 54. Do not
leave the CryoProbe System unattended during the first cool-down.
While the cool-down is in progress for about 2 h, there is plenty of time to do the
"HPPR CRP configuration" on page 45
in the User Manual.
WARNING: Do not disconnect any tube or cable from a running CryoProbe Sys-
tem unless
UNPLUG lights up on the CryoCooling Unit front panel. Pressurized cry-
ogenic helium gas is circulated between CryoProbe, CryoCooling Unit, and He
Compressor. It could cause cold burns on unprotected eyes and skin when tubes
are disconnected during operation.
c.5 C
OOL DOWN will keep flashing as long as the ambient temperature prep-
arations (evacuation, flushing cycles and charging with He) are in
progress. Several pneumatic pops will be audible. At this point, it is
recommended to check the secondary pressure at the He Regulator: it
should always come back to 22-25 bar. The primary pressure must
remain ∫ 40 bar at all times.
c.6 ~15 min later, CryoCooler and He Compressor will be started auto-
matically to perform the cool-down. C
OOL DOWN changes to steady
white during the actual cool-down. The characteristic periodic hiss of
the CryoCooler will be audible then.
c.7 If C
OLD on the CryoCooling Unit flashes, it will take about half an hour
more until the final temperature is reached and stabilized.
NOTE: A cool-down must not take more than 4 h; if it does, the Cryo-
Controller will interrupt automatically and warm up the system (see
"Cool-down doesn’t reach cold state" on page 66
).
c.8 Verify that the ‘sample’ temperature reading from inside the cavity is
at its preset value and stable. Now a sample can be inserted. At this
point, the "Low temperature limit in sample cavity" on page 46
in
the User Manual should be determined.
NOTE: For recommended sample depth and filling height, see the ‘L
IM-
ITATIONS - WARNINGS’ sheet for the CryoProbe and "Samples and
spinners" on page 55 in the User Manual.
IMPORTANT: Always keep an eye on the sample temperature with
edte when working with the CryoProbe. If the temperature drops,
eject the sample and keep monitoring the ‘sample’ temperature inside
the CryoProbe cavity.
c.9 Set all RF power levels pl and sp to 120 dB (recommended).
c.10 Enter xau crpwobb in XWIN-NMR and tune the CryoProbe on all
channels including
2
H, see "Tuning and matching" on page 48 in
the User Manual. When done, enter xau crpon.
c.11 Shimming can be started while C
OLD is still flashing, see "Shimming
and Lock-in" on page 49 in the User Manual.
c.12 When C
OLD is continuously on, the final conditions are stable.
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