Bruker NMR 400 89 Ascend DNP, User Manual, Page: 45 / 106

45 ZTKS0243 / Z31993 / 03
Troubleshooting
Continued from page before
Continued on next page
Indicator Possible reason Solution By
RT vessel becomes
cold and wet. Vacuum is broken or
less than 10
-3
mbar.
• Do not remove pumping
unit until liquid helium
fill-in is finished.
• Continue as in problem
Vacuum in RT vessel
does not reach
10
-6
mbar
Bruker Service
Cold leak after
transportation.
1. Stop cool down.
2. Warm up cryostat.
Bruker Service
Cold spot in the
RT-bore. Alignment not
correct.
1. Stop cool down.
2. Warm up cryostat.
3. Align the vessels.
Bruker Service
The helium flow
system becomes
very cold and icy
during flushing with
helium gas. Liquid nitrogen
remains in the
helium vessel,
boiling off strongly
during flushing.
1. Stop flushing.
2. Carefully remove all
liquid nitrogen using the
precooling tube.
3. Check with the dipstick to
be sure that the helium
vessel is completely
empty (no liquid nitrogen
or frozen nitrogen).
Bruker Service
After some intervals
of flushing it is not
possible to reach a
vacuum in the range
of 1 mbar. The globes in the
quench valves are
not fitting correctly in
the O-rings and thus
the quench valves
are leaky.
1. Stop pumping.
2. Remove frozen air and
frozen moisture with
warm helium gas.
3. Slightly grease the
O-rings and check the
position of the globes.
4. Check with the dipstick to
be sure that the helium
vessel is completely
empty (no liquid nitrogen
or frozen nitrogen).
Bruker Service
Liquid nitrogen
remains in the
helium vessel, boil-
ing off strongly dur-
ing flushing.
1. Stop pumping.
2. Carefully remove all
liquid nitrogen using the
precooling tube.
3. Check with the dipstick to
be sure that the helium
vessel is completely
empty (no liquid nitrogen
or frozen nitrogen).
Bruker Service