Dear colleagues,
Recently I have been struggling to deal with the lineshape stability problem. Two Bruker NEO systems 500MHz and 600MHz were installed in our lab two months ago. The specs (line shape, sensitivity, magnetic field drift) of both spectrometers are achieved. However, the stability of line shape of two magnets behaves dramatically different. The lineshape of 500 can hold several hours to even over night, while the lineshape of 600 splits in half an hour and degrades to a crowd of peaks overnight. Please see the attachment file for the problem.
1, The degradation of line shape is not caused by the convection of the sample. Lowering the temperature or spinning the sample makes no improvement.
2, The problem is not caused by the shimming control board. After the boards are exchanged on the two consoles, the 500 is still very stable and the 600 bad again.
3, There are no weird values of the shim coils. No trends of the shim value change observed.
4, The instability may not be due to the magnet. The lineshape specs are achieved on both system. The drift rate is 4Hz for 500 MHz while the value is even smaller (about 2Hz ) for the 600.
Now I need the help for this issue. First, have you ever had the same problem? what is the possible cause? Second, would you like to sign the acceptance document for the 600 system?
Thank you for your generous input! A follow up summary will be posted if necessary.
Guangyu
Received on Wed Mar 06 2019 - 03:59:48 MST