11
Z33048_00_01
Getting Started
1.11 Initial Shimming
First level shimming is done in the usual way by first setting the currents given in the
magnet manual and then seeing if the base shim can be improved in the GS mode.
Once the cryo-shims are set, continue adjusting the lower orders of the BOSS1 shim
system in the GS mode until your FID half height has reached approximately 100 ms.
1.12 Finding the Lock Field and Phase
Once your shim has reached a certain level, your lock should begin to show a signal.
1. Enable the Lock sweep mode in the BSMS panel.
2. Adjust the field and phase such that the “wiggles” are centred around zero and the
first wiggle is positive in both directions.
Due to sidebands, there will be more than one lock field value that gives a lock signal.
You can check which is the correct one by making a measurement, and checking that
the spectrum has the correct ppm scale (e.g 4.7 ppm for water, 7.2 ppm for a C6D6 sol-
vent peak).
Alternatively, you can use the Fourier AU program “flock”, which queries for the lock sol-
vent, creates a temporary 2H data set and starts an acquisition to find the lock signal in
the 2H spectrum. Flock compares the ppm shift of the 2H signal to the default value from
the edlock table. The difference in ppm is then converted to a shift in the lock field. The
new lock field is displayed in a pop-up window. Additionally, flock informs the operator
how many solvent peaks have been found and if this number is in agreement with the
number of resonance lines for the selected lock solvent. When the number of signals is
different from the expected value, flock uses the peak with the highest intensity to calcu-
late the lock shift. The new shift value is set in the Fourier and a normal lock procedure is
started.
Figure 1.4 Results of the AU Program FLOCK
The flock command also works with solvents with more than one peak and can be fine
tuned. Refer to the service manual for details.
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