INOVA400 ---- Gradient shim:
1. The default probe is 4-nuc. there is no gradient coil in the probe. so we have to use homespoil coil to do the gradient shim.
a. Set gradtype='nnh' -rather than gradtype='nnp'
b. use at least 2% H2O in D2O dopped standard sample. run a regualr proton spectrum
c. gmapsys --> select homespoil and proton
d. set the 90 degree pulse 15us and 30us for 180 pulse at tpwr=58 set the gain to 20 run a test if you see a gradient profile, then you could make a gradient shim map.
e. set gzsize=5
After the gradient shim, save the shim file and run 1% CHCl3 in CDCl3 to check the lineshape.
the best line on this probe is 0.23/3.76/5.37 Hz.