Shimming Work Shop
Shimming the Beast I Manual and Automatic Methods
Written by: Mike Brown Bruker BioSpin South NMR Training Center 001042006.meb
Shimming the Beast • In this presentation I will speak mainly about “manual shimming methods “ • The techniques discussed apply to BOSS l and BOSS II • Of course, gradient shimming is still the easiest, the quickest and the most precise way to shim a magnet • Gradient Shim methods are covered in detail in 2 very good manuals : – Gradient Shimming Manual XWINNMR 3.x and TopSpin 1.x, by Dr. Amy Freund and Dr. Donna Baldisseri, Bruker BioSpin Corp. – 2H Gradient Shimming in XWINNMR 3.5/3.6 and Topspin 1.x, by Peter Barron Bruker, BioSpin Pty Ltd
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Shimming the Beast • • • • • • • •
Theory Tips and tricks The shim “matrix” Manual shim method Tune procedure Simplex Cryoline and lineshape tests Pre-saturation test
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Theory of Shimming If a “perfect shim” is achieved: Then all of the Protons in the sample will be exposed to the same magnetic field. And all of the Protons will have the same frequency. And you will have “perfect line shape”.
γ Δ B0 Δ L.F = 2π 4
Theory of Shimming (cont.) If the Z1 Shim is “off” by a few units then a linear gradient is applied to the sample. A “spreading out” of the peak occurs This can be extended to Z3 and Z5 and all odd order RT Shims
γ ↑ ΔB0 ↑ ΔL.F = 2π 5
Theory of Shimming (cont.) If the Z2 Shim is “off” by a few units then a quadratic gradient is applied to the sample A “hump on one side” of the peak occurs
This can be extended to Z4 and Z6, all even order RT Shims 6
Tips for Manual shimming • Saturate the lock then back off a few dB • Set LOCK DC to –95 or so • Set lock Gain so the lock is in the top ¾ of the screen • Use AU program loopadj • Examine the line shape frequently • Shim slow and steady • Wait for the last round to settle out before continuing • “wsh” frequently
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Shimming Theory • Example of “On-axis” (Z or spinning) shims. Shims are used to compensate the magnetic field imperfection/ inhomogeneity in the sample area. Bruker standard bore magnets have 20 (BOSS I) or up to 34 (BOSS II) RT shim gradients.
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Shimming Theory • Example of field inhomogeneity due to offset of Z1 and Z2 shim. • Compensation is done by creating a magnetic field profile which has: • opposite sign compared to the inhomogeneity • same absolute intensity as the inhomogeneity • Compensation requires a shim system to create the compensation field And a gradient system to measure the inhomogeneity
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Mike’s Shim “Matrix”
First order
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
Second order Third order Fourth order Fifth order
Most Sensitive
Least Sensitive
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Mike’s Shim “Matrix”
First order
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
Third order
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Mike’s Shim “Matrix” Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
Second order
Fourth order
Non-Spin
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Mike’s Shim “Matrix”
Its never going to be a pure single “bad” shim You have to iterate between the shims in an order AND between orders 13
Mike’s Shim “Matrix”
Sample Dependent Probe Dependent Magnet and Shim stack
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Mike’s Shim “Matrix” Interactions Strong Interaction
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Not as an strong Interaction
Mike’s Shim “Matrix” Weak Interactions
Weak Interaction
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Interactions
Mike’s Shim “Matrix” 1st Order Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Mike’s Shim “Matrix” 2nd order Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Mike’s Shim “Matrix” 3rd Order Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Mike’s Shim “Matrix” 4th Order Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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Mike’s Shim Method • Run auto lock phase or “Loopadj” • Iterate between orders • Iterate between shims in an order • Adjust non-spin shims, non-spin • You can adjust all shims non-spin (spin and non-spin), 21
Mike’s Shim Method
Spinning Shims Adjust Spin or NON-Spin
Z
X
Y
Z2
XZ XY
YZ X2-Y2
Z3
XY2 XYZ
YZ2 Z(X2-Y2)
Z4
XZ3
YZ3
Z5
X3
Y3
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NONSpinning Shims Adjust ONLY NON Spin!
Mike’s Shim Method When you first adjust a shim: •Go up (CW) and then go down (CCW) with the adjustment, until you see the peak in the lock level, or FID integral, rise then fall. •Leave that shim at that peak value. •Then go to the next shim in that particular order •And adjust it to the peak. •Then go to the next shim in that order •And adjust it to the peak. •Then go back through until no more improvement can be gained. •wsh often!
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Shim Method A. Low orders Adjust Z1, Z2, Z3 Spin or Non Spin Adjust X, Y, XZ, YZ, XZ2, YZ2, XY and X2-Y2 Non-Spin Repeat A until there is no more improvement B. Mid Orders Adjust Z1, Z2, Z3, Z4 Spin or Non Spin Adjust XZ3, YZ3, XYZ and (X2-Y2)Z Non-Spin Repeat A and B until there is no further improvement C. High Orders Adjust Z1 – Z5 Spin Adjust X3, Y3, ZX3 and ZY3 Non-Spin Repeat A, B, C until no further improvement D. Spin Shims Adjust Z1-Z2-Z3-Z4-Z5 Spin or Non-Spin Repeat A, B, C, D until there is no further improvement 24
Tune • The BSMS has a shimming algorithm • It will work on most samples • It will work well on most solvents • It is fast and easy to implement in ICONNMR • It is useful for when gradients are not available 25
Tune Methods (SHIMMIT) spin # SHIMMIT spin DELAY 3 MAXLOCK 0.4 TIMEOUT 1800 LOCKDWELL 3 # Shim_name Maximum_Step_Size Number_of_Iterations Z 30 3 Z2 30 3 Z 5 5 Z2 5 5 Z3 5 5 #AUTOSHIM ON Z=2 Z2=4 This indicates a comment, this statement is not parsed by the BSMS. 26
Tune Methods (SHIMMIT non-spin) Shim_name Z Z2 X Y Z Z2 Z3
Maximum_Step_Size Number_of_Iterations 30 3 30 3 30 5 30 5 5 5 5 5 5 5
For each RT Shim you want TUNE to optimize you must have a line similar to these. The shim method is, to increase one shim value by step-size until the measured lock value decreases by a certain amount. Then the step-size is reduced according to the measured values. The optimization procedure is repeated until no more improvement is obtained. This is repeated not more then number_of_iteration times. For CDCl3 and DMSO-d6 use a step size of 25 to 30 and make Number_of_iterations about 3 to 5 27
Tips for Tune Methods (SHIMMIT) You must start with a good shim file for that probe ! Start with a good shim file (from line shape or presat) Then run your CDCl3 or D2O sample with “tune SHIMMIT” on the TopSpin command line. You should do a manual auto lock phase, after SHIMMIT finishes (or a loopadj). SHIMMIT is only useful after a good line shape has been found for that probe in that system. SHIMMIT can also be used as the tune file in ICONNMR if gradients Are not available.
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Simplex • Simplex is an automation program delivered with systems. • It will shim every sample and nearly every solvent quite nicely. • It can take quite a bit of time to shim a system (as much as 6 hours)
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Simplex # SIMPLEX_SPIN # SHIM
INITIAL Step Size
FINAL STEP SIZE
SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET SET
20 30 100 300 600 30 30 200 200 800 800 500 500 2000 2000 5000 5000 2000 2000 10000
4 4 10 30 60 5 5 20 20 80 80 50 50 200 200 500 500 200 200 1000
Z Z2 Z3 Z4 Z5 X Y XZ YZ XZ2 YZ2 XY X2Y2 XYZ X2Y2Z X3 Y3 XZ3 YZ3 Z6
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Simplex must have this Set of lines at the Beginning of the control file Initial: the initial value of the adjustment. Final: The final value of adjustment (used to judge if any further change is needed)
Simplex: The Iteration Control File WSH simplex_start LOCKDWELL 10 USE_LOCKLEVEL
(writes a starting shim file) (sets the time between lock level readings)
ROTATION ON WAIT (turns rotation on and waits for stabilization) SIMPLEX Z Z2 Z3 Z4 Z5 WSH simplex_final
(writes a final shim file)
This particular control file will work on any solvent including Acetone-d6. With a decent starting shim file !
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Cryoline Cryoline is used to test the magnet and BSMS for proper operation. • Use cryoline when you suspect a quenched cryoshim • When you suspect a bad RT shim • If you have a “non-responsive RT shim” Set all RT shims to ZERO! Create a shim file on disk called “zeroshim”
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Cryoline Use the HWT sample or a doped 1% H2O/99% D2O Sample. Non Spin. PULPROG = zg30 TD = 16K SI = 16K NS = 1 D1 = 500 millisecond P1 = 10usec (or 90 degree PW) PL1 = 0 dB (or 90 degree Power level) SW = 10 PPM (or more if needed) SOLVENT = D2O NUC1 = 1H O1P = on resonance (about 4.7 PPM) 33
Cryoline Measure the width of the peak in PPM at 50%, 12.5%, 5% and 1% of the peak height. This can most easily be accomplished by setting CY to 100 cm and measuring the width of the peak at 50.0cm, 12.5 cm, 50 cm and 1.0 cm. Plot the spectra with a CY of 12.5 and 500 centimeters. Plot the full spectrum. • Run cryoline locked and • Run cryoline unlocked (sweep off)
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Cryoline The usual accepted values for this test are listed in the following table:
These numbers are to be used as a guide. The CRYOLINE test is only an indication of the degree of difficulty of shimming the system to specifications. The broader the cryoline the more difficult the system will be to shim to specification.
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Bad Cryoline - TEST - System: AV-400 SB OrderNo.: BH083702 Console: H03128/0601 ECL 01 Customer: Bruker BioSpin South Engineer: Mike Brown P/N Console: H03128/0601 Shim system: BOSS I Magnet: BZH-227/400/70F Dewar: D-207/54-371 Shim File: zeroshim Probe: 5 mm PABBI Z820201/0022 Sample depth:20 Gas: air Flow Rate: 535 L/H TE: 300K RO: 20 rps Sample: HWT Sample results:re 7 50%0.19 PPM 12.5% 1.50 PPM 10% 1.82 PPM 5% 2.05 PPM 1% 2.5 PPM
Labeled Methanol In the HWT sample
4
3
2
1
0
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-1
-2
-3
-4
pp m
Good Cryoline - TEST - System: AV-400 SB OrderNo.: BH083702 Console: H03128/0601 ECL 01 Customer: Bruker BioSpin South Engineer: Mike Brown P/N Console: H03128/0601 Shim system: BOSS I Magnet: BZH-227/400/70F Dewar: D-207/54-371 Shim File: zeroshim Probe: 5 mm PABBI Z820201/0022 Sample depth:20 Gas: air Flow Rate: 535 L/H TE: 300K RO: 0 rps Sample: HWT Sample results: 50%0.34 PPM 12.5% 0.52 PPM 10% 0.54 PPM 5% 0.63 PPM 1% 0.84 PPM
Labeled Methanol In the HWT sample
4
3
2
1
0
-1
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-2
-3
-4
pp m
Proton Lineshape • Probably the most critical and important specification to meet with any system or probe. • Almost always you will do line shape first on any probe. (Exceptions: inverse gradient probes, you would start with sucrose-solvent suppression test) • There is a Proton lineshape specification for all Proton observe probes, DUAL, BBI, TXI, TBI QNP etc. • Most BBO (x nucleus observe probes) will not have a Proton lineshape specification • Exception: 5mm BBO for SB systems
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Proton Lineshape • Samples 200 to 360 MHz systems 3 % CHCl3 in Acetone-d6 400 to 600 MHz systems 1 % CHCl3 in Acetone-d6 700 MHz and above 0.3 % CHCl3 in Acetone-d6 Be very careful of radiation damping ! You can de-tune the probe slightly to minimize the effects of radiation damping.
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Proton Lineshape Parameters: Use ATP parameters for Proton line shape NS = 1 for speed while shimming, NS = 4 for the test DS = 0 SW = 2.5 PPM TD = 32K (SI = 16K) AQ = 16 sec O1P = 8 PPM D1 = 2 seconds P1, PL1 = 90 degree pulse Spin at 20 rps for spinning line shape.
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Comparison Spin and Non-Spin Q modulation
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Comparison Spin and Non-Spin • The lock level should drop only slightly between spin and non-spin • Adjust the shims so that the non-spin lock level is about the same as the level of the spin lock level • Then iterate between spinning and non-spin shims until there is no more improvement
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Tips and Tricks •Use any previous shim files for the system, if available •Use automatic methods where possible (gradshim or simplex) •Set up a simplex or map 3D RT shims over night •Use stable temperature and gas flow always ! •Never rotate faster than 20 rps. •Slow and steady is best. •Adjust a shim then wait for the lock level to settle before proceeding to the next shim.`
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Pre-saturation test •If gradients are available, use gradient shim to obtain good pre-saturation spectra •If gradients are not available then start with the proton non spin lineshape shim file, manually shim. Parameters: SW = 12 PPM D1 = 5 seconds O1p = on resonance (adjust) Pl9 = adjust for best suppression RG = at least 64 (bigger is better) SW = 12 PPM D1 = 5 seconds O1p = on resonance (adjust) Pl9 = adjust for best suppression P1 and Pl1 = 90 degree pulse width 44
Pre-saturation test good
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Pre-saturation test with Z6 miss-set Small hump usually Caused by Z6
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References • SHIMMING AN NMR MAGNET Gerald A. Pearson, Chemistry Department, University of Iowa, Iowa City, IA 52252 USA • Bruker SpinReport 154/155 and 152/153 articles by W. E. Hull • Shimming Ain’t Magic: The Shimming of High Resolution NMR Magnets, As Told by a Couple of Nuts, Virginia W. Miner and Woodrow W. Conover • AM User’s Manual, Bruker Instruments Inc. • CXP User’s Manual, Bruker Instruments GMBH • Dr. Clemens Atkins, personal communication • Henry Luhrs, personal communication • Dr. Charles Fry, Journal of Chemical Education 81:922-932 2004 and (http://www.chem.wisc.edu/~cic/nmr/Guides/Other/z1z2_shimming.pdf)
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Any Questions ?
Thank you for your attention ! Any Questions ?
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