; dsr_n15cpmg
; arx-version
; simplified CPMG pulse sequence for T2 measurements
; CAUTION : partial suppression of cross-correlation is performed so not 
;        suitable as a research-grade pulse sequence
; direct detection of 15N with decoupling of 1H during acquisition
; DSR, Spring 2005

; Reference:
; Thompson, L.E., and Rovnyak, D., "Accessible NMR Experiments Studying the Hydrodynamics of 15N-enriched Ubiquitin at Low Fields", Submitted to Biochem and Mol. Biol. Ed., 2005.

;set 180 pulses
;commented out since better to have students set these manually
;p2=p1*2
;p4=p3*2

1 ze
2 d1 do dl0
3 (p3 ph1):d
  d4
  (p4 ph2):d (p2 ph2)
  d4
  (p3 ph3):d (p1 ph4)
  d4
  (p4 ph2):d (p2 ph2)
  d4
4 d20
  p2 ph4
  d20
  lo to 4 times c
  d3
  (p4 ph2):d
  d3
5 d20
  p2 ph4
  d20
  lo to 5 times c
  d3 dl5
  go=2 ph31 cpd
  wr #0 if #0 vc
  20u do
  lo to 1 times l4
exit

ph1  = 0 2 0 2 0 2 0 2
ph2  = 0 0 0 0 0 0 0 0
ph3  = 1 1 1 1 3 3 3 3
ph4  = 0 0 2 2 0 0 2 2
ph31 = 0 2 2 0 2 0 0 2

;tl0: transmitter power level (default)
;dl0: decoupler high power level
;dl5: decoupler power level for CPD/BB decoupling
;p1 :  90 degree transmitter high power pulse (15N)
;p2 : 180 degree transmitter high power pulse (15N)
;p3 :  90 degree decoupler high power pulse (1H)
;p4 : 180 degree decoupler high power pulse (1H)
;p31: 90 degree pulse for decoupling slave timer (cpd sequence)
;d1 : relaxation delay; 1-5 * T1
;d3 : refocusing interval for 1H 180 pulse (suggest 2 ms) 
;d4 : 1/(4J(XH)) ; 2.7 ms is ok
;d20: refocusing interval for cpmg; must be << 1/2J; (suggest 400-600us)
      Note that a single interval is 4*d20 + 2*p2 + 2*d3 + p4  ~  4*d20
      That is for educational purposed, can just assume the that 4*d20 is
      the evolution increment
;l4 : number of times to perform the experiment, incrementing the 
;     variable counter list every time; recommend 4-5 values
;     For example, with d20 set to 600us, a vclist of (2, 10, 20, 40, 75)
;     corresponds to relaxation times of (4.8 ms, 24 ms, 48 ms, 96 ms, 180 ms)

;NS: 8 * n
;DS: 4-8 transients reasonable
;cpd: cpd-decoupling according to sequence defined by cpdprg (in eda)