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I'm measuring T2 in paramagnetic materials. These values are very short (0.5-5 ms), and I have to use very short interpulse delays. On Bruker machines standard CPMG sequence looks like this:

d1 p1(90°) [d20 p2(180°) d20]

the number of 180° trains [number of times the sequence in square brackets is repeated] is specified in vc list. I use 12 points, from 8 to 96 pulse trains.

Suppose my d20 is 40 us and my p2 is 20 us.

My questions are:

  1. Should the duration of p2 be included in the calculation of TE? If yes, then in my example, the TE would be 0.1 ms, not 0.08 ms (per loop).

  2. Should I be worried about applying high-power pulses so frequently? In this example, the pulse is applied 20% of the time. What if d20 is 0? This would result in a continuous pulse of up to 96*0.02=1.92 msec. Can this fry the probe? My d1 is at least 100 ms.


asked Jan 18 '15 at 00:26

A%20K's gravatar image


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(2) if you have an oscilloscope, you can monitor the reflection which tells you whether arcing occurs. From my experience, if you are using an liquid probe that usually runs with a power 50W, 2ms pulse should be fine. You can also make you d1 longer for better heat dissipation. I have tested CPMG with very high power, 300W, 2us pulse+10us spacing (equivalent to your d20 5us), 1k pulses. It still works fine.


answered Feb 27 '15 at 12:48

Jeffreyyyy's gravatar image


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