Signal-to-noise considerations

Signal-to-noise considerations make most neutron-based explosive detection approaches very difficult to implement. The basis for combining multiple detection approaches (FNA, along with thermal gamma detection and neutron transmission spectroscopy) in a FNAP application that preserves the small volume advantage of a APSTNG remains to be established. There are distinct advantages associated with the API approach, but the concomitant reductions in available neutron flux, issues of tube lifetime, and the intrinsic poor spatial resolution must be taken into consideration for potential applications. 

In the absence of interferents, the correlation coefficient is equal to 1 and therefore ohy = 1. In this case, the minimum detection error is defined solely on the basis of signal-to-noise considerations. When interferents exist, the correlation coefficient is always smaller than 1 and therefore olf is always larger than 1. The minimum detection error approaches infinity when there is complete overlap and the analyte signal is indistinguishable from interfering components. 

The optimum frequency at which to work is going to be dictated by other considerations as well, availability of a suitable source and detector, signal to noise considerations, working temperature and pressure, and the other species to be determined. Bringing cost into the equation does focus the mind on the expense of both sources and detectors and unless there were a particular operational need the spectral region 40-200 GHz would be a likely compromise for most applications (see Section 6.2). 

It is anticipated that future experiments in photodissociation dynamics as well as inelastic and reactive collisions will involve coincidence measurements in which vector quantities of more than one fragment are simultaneously measmed. Such measurement would provide a wealth of detailed information on the nature of the transition state region. Many such experiments were imrealized because of the poor signal-to-noise considerations. With the advent of laser light sources with high repetition rates, however, coincidence measurements are becoming quite feasible. 

In the case of narrow absorption bands, due to signal-to-noise considerations, it is better to report the area of the peak Je(p)dv (V are wavenumbers in cm ), which is proportional to the peak intensity. Two other quantities, which can be reported instead of e, are the transition dipole strength D and the oscillator strength P, to which they are related by the following two equations [53]. 

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