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Unread 06-12-2012, 11:25 PM
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Default Gradient strength recalculation

Gradient strength recalculation

Iam bit stuck with % z gradient calculation used in Bruker pulse programs. In some instruments (Varian) they use as short as 200us for some gradient pulses, but in Bruker, they fix the length of all the gradient pulses as constant (say 500 us) and vary the gradient strength accordingly.

Hence, is there any easy way to convert a gradient pulse of say 17 G/cm applied for 0.5 ms to 'x' G/cm for 1ms.(where 'x' is the new gradient strength for 1ms).

Once this conversion is completed,the next step would be to calculate the gradient % which i think is the ratio of ('x' (G/cm)*100)/Maxgradamplitude, where Maxgradamplitude is the maximum G/cm specified for a spectrometer (e.g. 70 G/cm for an 800 MHz).

(I read from Dr.James Keeler notes that the sum of the phase of the coherence before and after the application of a pair of z gradient pulses should be zero, for an appropriate coherence to be selected. The book also suggests an handy formulae (s1*Bg1t_1)/(s_2Bg2*t2) = -p1/p2; where s1,s2 are shape factors of gradient pulses used for coherence selection. Bg1,Bg2 are the gradient field strength of first and second gradient pulse, t1,t2 are the time period for each applied pulse and p1 and p2 are the coherence before and after the gradient pulses, respectively. But this formulae requires the complete coherence transfer pathway to be elucidated.On the other hand, the published sequence would have considered all these details while providing the strength and delays of gradient pulses. So is it possible to take advantage of the already existing information and make the conversion for desired delays in a simplied way.)



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