Measurement of very short T2

i like this post (click again to cancel)

i dont like this post (click again to cancel)

remove favorite mark from this question (click again to restore mark)

Hello,

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:

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).
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.

Thanks!

cpmg t2

asked Jan 18 '15 at 00:26

A K
1

One Answer:

oldest newest most voted

i like this answer (click again to cancel)

i dont like this answer (click again to cancel)

(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.

link

answered Feb 27 '15 at 12:48

Jeffreyyyy
1

Here (once you log in) you will be able to sign up for the periodic email updates about this question.

Your answer

Please start posting your answer anonymously - your answer will be saved within the current session and published after you log in or create a new account. Please try to give a good answer, for discussions, please use comments and please do remember to vote (login to vote)

toggle preview

Tags:

cpmg ×7
t2 ×6

Asked: Jan 18 '15 at 00:26

Seen: 3,335 times

Last updated: Feb 27 '15 at 12:48

Related questions