ISO_NWIPs-for-Ballot

ISO/NP

5.3 Outline of apparatus configuration 507 The configuration of the NMR apparatus includes a cryogenically cooled superconducting magnet, an 508 NMR probe, a high-frequency pulse generator, a signal receiver and a data processor. The main 509 spectrometer is a pulse Fourier transform NMR (FT-NMR) which simultaneously excites the entire 510 frequency range of the observed nuclei with a powerful radio frequency pulse (see Figure 3). 511 After pulse irradiation of the sample, the free induction decay (FID) is observed. The signal intensity is a 512 function of time for the FID. A spectrum that is a function of the frequency is obtained by applying a 513 Fourier transformation to the FID data. 514

NMR spectrum

Data processing section (computer)

Fourier transform

Superconducting magnet

Digital converter

NMR Probe

Receiver section

FID （ free induction decay ）

Radio frequency receiver

Radio frequency generator

High frequency generation section

Pulse programmer

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Radio frequency (pulse )

Figure 3 － Example of a pulse Fourier transform NMR spectrometer (FT-NMR apparatus)

The elements of the apparatus are as follows: 518 a) Liquid helium cooled superconducting magnet; 519 b) NMR probe (detector), for irradiating the sample with radio-frequency pulses and detecting the 520 radio frequency decay (FID NMR signals) generated by the sample; 521 c) Radio-frequency (RF) pulse generator and amplifier, applied to the sample in a very specified way 522 that is specified by the pulse sequence and other spectrometer acquisition parameters. These pulses 523 (audio frequencies) are mixed with a fixed, high frequency that corresponds to the NMR resonance 524 frequency. This is largely determined by the size of the static magnetic field, and the nucleus being 525 observed. The apparatus sends the collection of pulses to the transmitter/detector in the magnet 526 probe to excite the NMR sample signals. 527 d) Signal receiver, to measure the weak RF signal emitted by the sample, digitize and amplify it, and 528 mix all frequencies down again. This FID is now available to be co-added with others if signal 529 leveraging is performed to improve the overall signal size. 530

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