System and method for characterizing a sample by low-frequency spectra

1 - 22 . (canceled)

23 . Apparatus for interrogating a sample that exhibits low-frequency molecular motion, comprising:

a container adapted for receiving the sample, the container having both magnetic and electromagnetic shielding;

an adjustable-power source of Gaussian noise for directing Gaussian noise to the sample, with the sample in the container;

a detector for detecting an electromagnetic time-domain signal composed of sample source radiation superimposed with the directed Gaussian noise; and

an electronic computer adapted to receive the time-domain signal from the detector, and to process the signal to generate a spectral plot that displays, at a selected power setting of the Gaussian noise source, low-frequency spectral components characteristic of the sample in a selected frequency range between DC and 50 kHz.

24 . The apparatus of claim 23 , wherein the electronic computer includes a signal analyzer that functions to (i) calculate a series of Fourier spectra of the time-domain signal over each of a plurality of defined time periods, in a selected frequency range between 100 Hz and 50 kHz, and (ii) average the Fourier spectra.

25 . The apparatus of claim 24 , wherein the calculating includes calculating at least five Fourier spectra, each taken over a 1-5 second time-domain interval.

26 . The apparatus of claim 23 , wherein the source of Gaussian noise includes an adjustable-power Gaussian noise generator and a Helmholz coil which is contained within the magnetic electromagnetic shielding, and which receives a selected noise output signal from the noise generator in a range 100 mV to 1 V.

27 . The apparatus of claim 26 , wherein the generator is designed to inject Gaussian noise into the sample at a frequency between DC and 2 kHz.

28 . The apparatus of claim 23 , wherein the detector is a second-derivative gradiometer which outputs a current signal, and a SQUID operatively connected to the gradiometer to convert the current signal to an amplified voltage signal.

29 . A method for interrogating a sample that exhibits low-frequency molecular motion, comprising:

placing the sample in a container having both magnetic and electromagnetic shielding,

injecting noise into the sample at a selected noise amplitude;

recording an electromagnetic time-domain signal composed of sample source radiation superimposed on the injected noise,

generating a spectral plot that contains, at a selected power setting of the noise source, low-frequency, sample-dependent spectral components characteristic of the sample in a selected frequency range between 100 and 50 kHz, and

repeating the injecting, recording and generating at different selected noise amplitudes until a plot showing a maximum or near maximum number of spectral components characteristic of the sample is generated.

30 . The method of claim 29 , wherein the generating includes (i) calculating a series of Fourier spectra of the time-domain signal over each of a plurality of defined time periods, in a selected frequency range between 100 Hz and 50 kHz, and (ii) averaging the Fourier spectra.

31 . A method for interrogating a sample that exhibits low-frequency molecular motion, comprising:

receiving the sample;

magnetically and electromagnetically shielding the sample;

directing adjustable-power Gaussian noise to the sample;

detecting an electromagnetic time-domain signal composed of sample source radiation superimposed with the directed Gaussian noise; and

receiving the time-domain signal, and processing the signal to generate a spectral plot that displays, at a selected power setting of the Gaussian noise source, low-frequency spectral components characteristic of the sample in a selected frequency range between DC and 50 kHz.

32 . The method of claim 31 , wherein the processing includes (i) calculating a series of Fourier spectra of the time-domain signal over each of a plurality of defined time periods, in a selected frequency range between 100 Hz and 50 kHz, and (ii) averaging the Fourier spectra.

33 . The method of claim 32 , wherein the calculating includes calculating at least five Fourier spectra, each taken over a 1-5 second time-domain interval.

34 . The method of claim 31 , wherein the directing Gaussian noise includes providing a Helmholz coil contained within magnetic electromagnetic shielding, which receives a selected noise output signal in a range 100 mV to 1 V.

35 . The method of claim 34 , wherein the directing Gaussian noise includes injecting Gaussian noise into the sample at a frequency between DC and 2 kHz.

36 . The method of claim 31 , wherein the detecting is performed using a second-derivative gradiometer which outputs a current signal, and a SQUID operatively connected to the gradiometer to convert the current signal to an amplified voltage signal.

37 . An apparatus for interrogating a sample that exhibits low-frequency molecular motion, comprising:

means for placing the sample in a container having both magnetic and electromagnetic shielding;

means for injecting noise into the sample at a selected noise amplitude;

means for recording an electromagnetic time-domain signal composed of sample source radiation superimposed on the injected noise;

means for generating a spectral plot that contains, at a selected power setting of the noise source, low-frequency, sample-dependent spectral components characteristic of the sample in a selected frequency range between 100 and 50 kHz; and,

means for repeating the injecting, recording and generating at different selected noise amplitudes until a plot showing a maximum or near maximum number of spectral components characteristic of the sample is generated.

38 . The apparatus of claim 37 , wherein the means for generating includes means for calculating a series of Fourier spectra of the time-domain signal over each of a plurality of defined time periods, in a selected frequency range between 100 Hz and 50 kHz, and means for averaging the Fourier spectra.