Patent ID: 6952652

Claim:
Apparatus for use in detecting a selected material in a sample, comprising (a) a sample holder for holding the sample, the holder being shielded from ambient electrical and magnetic energy, (b) a noise generator for introducing noise into the sample, without ionizing the sample, (c) a data storage device for storing, for each of one or more preselected materials including the selected material, a data set containing low-frequency spectral components that are (i) in a selected frequency range between DC to 50 kHz, and (ii) characteristic of that material, (d) a detector assembly including a detector coil adjacent the sample holder for producing a time-domain signal having signal components related to low-frequency electromagnetic radiation produced by the selected material in the sample, (e) signal conditioning components for converting the signal from the detector coil to an amplified conditioned signal from which frequency components above a selected frequency have been removed, (f) an electronic computer operably connected to the conditioning components to receive the conditioned signal therefrom, and for processing this signal by: (i) retrieving from the data storage device a data set of low-frequency spectral components characteristic of the selected sample material, (ii) filtering the conditioned signal, with such in digitized form, to selectively pass low-frequency spectral components corresponding to those of the retrieved data set; (iii) cross-correlating the filtered signal from (ii) with the data set of low-frequency spectral components from (i) to produce a frequency-domain spectrum in a frequency range within DC to 50 kHz, and (iv) determining whether the frequency-domain spectrum contains one or more low-frequency signal components that are characteristic of the selected material, and diagnostic of the presence or absence of such material in the sample, and (g) an interface device operably connected to the computer for displaying the output of the processing.