Protocol: Xx  Sequence: xx.c  Apptype: solidseq1d

Description: 

X pulses with interleaved acquisition.  Used for multipulse calibration 
of pwX90. Usually performed with a liquid sample or a sample of RTV 
silicon rubber with slow spinning. Xx can also be used to examine 
sampling windows and set the blank/unblank delays r1Xxx and r2Xxx. 

Xx subtracts probe ring-down with a two-scan (0,2) phase cycle of the 
preparation pulse and the receiver.  The module xxX has zero phase for 
all scans.  For very short values of tauXxx, when probe proton 
background is present the oscillating pattern will not be symmetric 
about zero, due to a constant signal from probe ringing and background. 
Use One scan to see the signal without ringing. 

Additional Software: 

reset_xx -  If the current experiment is Xmx this macro copies the 
values of xmxX to xxX. Otherwise the values of aXxx and pwXxx are set 
from aX90 and pwX90.  This macro is run from the protocol. 

Setup: 

Load a calibrated data set and select the protocol Xx. For a new 
nucleus set the desired observe nucleus and select Onepul to array 
pwX90 for a rough calibration before using Xx. 

Set aXprep = aX90 and set pwXprep = pwX90. Set phXprep = 0. Set aXxx = 
aX90 and set pwXxx = pwX90 and nt = 2. 

Set tauXxx = 10 us and set npaXxx = 10.  Set r1Xxx = 1.0, us, r2Xxx = 
0.5us and r3Xxx = 1.0 us.  Set rof3 = r3Xxx on the Receiver page 
(important!!).   It may be necessary to fine adjust r1Xxx and r2Xxx to 
eliminate ring down from the sampling periods.

Set sw = 1/tauXxx to obtain one point per sampling period or set sw = 
5.0e6 to observe the sampling windows. Note that because the DDR allows 
only specific dwell times that it may be necessary to choose sw first 
and set tauXxx = 1/sw. If tauXxmx does not equal the dwell the FID 
output will not appear accurate. A sw = 5.0e6 can be used to observe 
for any value of tauXxx. 

Obtain 2 scans. Adjust aXxx or pwXxx to obtain a FID that is a decaying 
cosinusoid with 4 points per cycle.  When the optimum is obtained set 
pwx90 = pwXxx. Alternatively Fourier transform the pattern and measure 
the splitting delta of the doublet.  The flip angle is 180.0*delta/sw. 

Use Xx to view the sampling window that will be used for multi-pulse 
experiments and remeasure pwX90 under these conditions.   Set tauXxx to 
a value that will create a window similar to that of the multipulse 
experiment (c.f. 6.0-8.0 us for Br24q, etc). Note that the actual 
window between pulses for Xx is (tauXxx - pwXxx).  Set sw = 5.0e6. 
Adjust npaXxx to open or close the sampling window. One unit of npaXxx 
corresponds to 100 ns of acquisition. The FID will now contain multiple 
points in each acquisition period and appear as a series of square 
pulses rather than points.  If the value of npaXxx is too large or 
tauXxx is too small one will see distortion from ring-down in the first 
points of each sampling window. Determine the best acquisition with the 
shortest tauXxx.

Parameter Groups: 

prepX:  Module:  no 
Sequence:  br24q.c      
Description:  Implements a variable length pulse to provide quadrature 
              detection about a tilted precession axis. Typically followed
              by a windowed multiple-pulse acquisition.
Parameters:  Sequence Page
       aXprep - the amplitude of the obs pulses. 
       pwXprep - 90-degree flip on the obs channel. 
       phXprep - small-angle phase offset of the pulse. The phase must 
              be reset to zero after the pulse. 

scaleX:  (processing)  Module:  no 
Sequence:  br24.c    
Description:  Shows the F2 scale factor, scalesw, for evolution of the 
              obs nuclei under a multiple-pulse waveform. 
Parameters:  Sequence Page
       scalesw - the F2 scale factor. Typically scalesw is the inverse 
              of the mutiple-pulse scale factor.         

xxX:  Module: yes
Sequence:  xx.c 
Description:  Implements pulses on obs with acquisition in each window. 
              Used for measurement of the 90-degree pulse width.  
Parameters:  Sequence Page
       aXxx - amplitude of the obs pulses.
       pwXxx - 90-degree flip on obs.
       r1Xxx - pre-pulse delay (similar to rof1).         
       r2Xxx - post_pulse delay (similar to rd or rof2).
       r3Xxx - T/R-to-rcvron delay (must equal rof3 or 2.0 us if rof3 
              is not defined). 
       tauXxx - cycle time for one window and one pulse. 
       npaXxx - number of 100 ns ticks in the detection window. 
       chXxx = 'obs' must be set (not shown).
Implementation:  WMPA xx = getxx("xxX");
Underscore function: _xx(xx,phXxx);  phXxx is the overall phase table. 


