The use of pseudonoise sequences to code a pulsed neutron logging source

Pseudonoise coded sources producing a seemingly erratic sequence of closely spaced, low-energy impulses have been used extensively to probe deterministic systems. Data processing of the system output results in a record which would have been produced by a source having much larger energy impulses at a much greater time spacing. This paper is a study of the merit of this approach in pulsed neutron logging where the system must be regarded as stochastic. It is concluded that for processes with an exponential decay, a pseudonoise coded source gives some improvement over conventionally coded sources for times shorter than the time constant of the process. For longer times it is decidedly inferior.