SpinCore Hahn-Echo package for RadioProcessor and iSpin-NMR

The Hahn-Echo experiment program is available in the RadioProcessor Example Programs.

Figure 1 shown below depicts a Hahn-Echo experiment conducted on household cooking oil using a 10.8 MHz permanent magnet.

Fig 1.

Figure 1 shows what the signal looks like when capturing data continuously during a Hahn-Echo experiment. The large spike is the 180 degree pulse being applied.

Figure 2 below shows the pulse sequence used by the RadioProcessor to perform this experiment. Each vertical line is a new instruction, and the names of the delays used are shown with arrows. The Hahn-Echo program included in the RadioProcessor examples will accept command line parameters which can be used to specify the values for each of the pulse program parameters.

CPMG Timing Sequence
Fig 2.

Shown in this figure is what the RF excitation pulse will look like, as well as what the acquired baseband data will look like. The tx_enable and scan_trigger signals are both internal signals used to control the timing of the experiment.

The Hahn-Echo executable takes the following arguments as inputs:

Hahn_Echo

P2_time

ringdown_time

P2_phase

P1_phase

tau

num_scans

fnam

bypass_fir

adc_freq

repetition_delay

blanking_bit

blanking_delay

debug

amplitude

MHz

kHz

degrees

0 or 1

MHz

seconds

0-3

0 or 1

0.0-1.0

SF - Spectrometer frequency, in MHz
SW - Desired baseband spectral width, in kHz
P2_time - Pulse length of 90 degree pulse, in us
ringdown_time - Ring down time after 90 degree pulse, in us
P2_phase - Phase of 90 degree pulse
P1_phase - Phase of 180 degree pulses
tau - tau is the time between the 90 degree pulse and the180 degree pulses
num_scans - Number of times to repeat the scan (and average the data)
fname - Filename to store data to
bypass_fir - A 1 bypasses the signal around the FIR filter, or 0 to use it. See manual for details on this
adc_freq - Clock frequency of the board, in MHz
repetition_delay - Time to allow sample to relax after each scan (in seconds)
blanking_bit - Number of the TTL bit to use for the blanking signal to the power amplifier.
blanking_delay - Time (in milliseconds) to power on the amplifier before experiments (3.0 is a good value for the PA10W)
debug - Set this to 1 to generate SpinAPI debug output, 0 otherwise
amplitude - (Optional) Sets the amplitude of the pulses; the default value is 1.0

The P1_time parameter shown in Figure 2 is not specified on the command line. It is calculated inside the CPMG program as:

P1_time - 2*P2_time

Download

The Hahn Echo Package is available as part of the RadioProcessor Examples.

Hahn_Echo.exe (32-bit)

Hahn_Echo.exe (64-bit)

Hahn_Echo.bat

Source code: Hahn_Echo.c