< The receiver block diagram | Index | Quick guide to NMR matlab online analysis >
Scheme for a description
log in on the linux PC
open a terminal window
cd nmr/LabFisicaStatiCondensati/mygroup directory
launch the program
gtknmr&
Hardware settings
You will need to make sure that your tunable probe is also mached to 50 Ohm in the frequency renge of interest. This is done normally directly with a synthesizer not connected to the NMR spectrometer, by means of a magic T: when a 50 Ohm source is connected to the input and the main output is a load, the third connector outputs the reflected wave, which is zero when the load is also 50 Ohm.
Switch on the synthesizer, the power amplifier and the HyReSpect NMR spectrometer.
Tune the probe at the working frequency {$\nu_L$}. This is done with a replica of the magic T, with the third output connected to an oscilloscope and the input source from the spectrometer. HyReSpect requires the synthesizer to be set at a frequency {$\nu=\nu_0+\nu_L$}, with {$\nu_0=1050$} MHz for its heterodyne building scheme. The irradiation frequency {$\nu_L$} is obtained internally and it is directed on a dedicated output for this purpose, whenever the pulse sequence is idle.
Always remember to re-tune the probe each time you change the working frequency!
Description of the grafical user interface (gui)
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Select the File tab
file selection
comments
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Select the Control tab
check that the synthesizer (e.g. Rohde Schwarz) appears in the control pop-up
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Attach:pulse-timing.png Δ
The sketch displays an echo sequence: time along the axis, the step functions represent the two pulses, names (R,AD+, ...) indicate time intervals
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Select the Sequence tab
For an echo pulse, write the P1, P2 pulse durations, e.g. 0.2u (for 0.2 µs, 0 to end the pulse list), and delay between the two, D1, e.g. 12u
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The display will contain the data
The lower panel in the gtknmr GUI select other acquisition parameters:
- RlxD relaxation delay is the interval between sequence repetitions, must be of order 5 times T1
- Rinh Receiver inhibit (keeps the receiver switched off during rf pulses)
- AcqD Acquisition delay, must be at least 1/fltr, the sum of Rinh and AcqD is represented as R+AD in the sequence sketch above
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- TxAtt Transmitter attenuation, controls the power in the pulses in dB, the larger the number the weaker the pulse
- RxAtt Receiver attenuation, the NMR signal is strongly amplified to start with, and this parameter controls a subsequent attenuation, to set the maximum admissible total amplification avoiding saturation of the ADC
- BlkSiz block size, number of digitized points
- fltr filter width in inverse us. This filter is optimized to avoid aliasing
- AdcRate sample rate of the ADC
- MxScan maximum scans, number of seque3nce+acquisition repetitions, the signal is summed (averaged) for noise reduction
- NScan number of scans actually recorded
Start ALT-G start acquisition
Abort stop acquisition before reaching MS
Kill ALT-K clear memory (do not save)
Save ALT-S save the measurement in the current zone
< The receiver block diagram | Index | Quick guide to NMR matlab online analysis >
