Abstract: A method of nuclear quadrupole resonance testing a sample is disclosed in which the excitation applied to the sample is arranged so that phase and amplitude information may be obtained from the response signal, and in which the signal is resolved into two components. Particularly if a parameter such as radio-frequency field strength varies with position, this may give an indication of the distribution of nuclei in the sample, preferably from the phase of the response signal. Positional information can also be obtained by measuring from two or more reference points. This may be employed in imaging. The phase information may be employed to improve the signal to noise ratio obtainable in other methods where only amplitude information was previously available, for example in distinguishing genuine NQR response signals from spurious signals.

Abstract: Methods of and apparatus for Nuclear Quadrupole Resonance (NQR) testing a sample containing quadrupolar nuclei exhibiting a given value of spin-lattice relaxation time, T1, are disclosed. The method comprises applying two excitation blocks to excite nuclear quadrupole resonance, there being a given delay time between the two blocks, detecting resonance response signals, and comparing the response signals from respective blocks. The delay time is less than the T1 value of the nuclei.

Abstract: A method of nuclear quadrupole resonance testing a sample is disclosed in which the excitation applied to the sample is arranged so that phase and amplitude information may be obtained from the response signal, and in which the signal is resolved into two components. Particularly if a parameter such as radio-frequency field strength varies with position, this may give an indication of the distribution of nuclei in the sample, preferably from the phase of the response signal. Positional information can also be obtained by measuring from two or more reference points. This may be employed in imaging. The phase information may be employed to improve the signal to noise ratio obtainable in other methods where only amplitude information was previously available, for example in distinguishing genuine NQR response signals from spurious signals.

Abstract: A method of detecting the presence of a particular substance in a given sample. According to the method, nuclear resonance is excited in a substance and response signals are detected from the substance using a probe. The probe is adjusted in dependence on the character of the sample. A method of detecting the presence of a sample which gives rise to interfering signals, not due to nuclear resonance, comprises exciting nuclear resonance in the sample, and detecting and processing the response signal from the sample in such a way as to at least partially filter out the interfering signals arising from the sample.

Abstract: A method of nuclear quadrupole resonance testing a sample comprising a first type substance containing quadrupolar nuclei and a second type substance which may give rise to spurious signals which interfere with response signals from the quadrupolar nuclei, comprises applying a pulse sequence to the sample to excite nuclear quadrupole resonance, the pulse sequence comprising at least one pair of pulses; detecting response signals; and comparing, for the or each such pair, the respective response signals following the two member pulses of the pair, the pulse sequence being such that the respective spurious signals following the two member pulses can be at least partially cancelled by the comparison without the corresponding true quadrupole resonance signals being completely cancelled; and for the or each such pair, the two member pulses being of like phase.

Abstract: Methods of testing a sample in which long composite pulses comprising a sequence of short closely spaced pulse elements are disclosed. The pulses generate a qualitatively different response characteristic, which can be tailored as desired by suitable adjustment of the pulses. Near sinusoidal dependence on pulse length can be attained, and effective, efficient, inversion pulses can be produced. Typically each pulse element generates a small flip angle of a few degrees, and the sequence conatins tens or even hundreds of elements. Similar excitation and effects may be produced by amplitude modulating a carrier, rather than switching pulses on and off; there is little discernible difference in the excitation seen by the sample.