Other

Michael Momayezi

William K Warburton

Jackson T Harris

John W Wahl

Peter M Grudberg

A method and apparatus for processing step-like output signals (primary signals) generated by non-ideal, for example, nominally single-pole ('N-1P ') devices. An exemplary method includes creating a set of secondary signals by directing the primary signal along a plurality of signal paths to a signal summation point, summing the secondary signals reaching the signal summation point after propagating along the signal paths to provide a summed signal, performing a filtering or delaying operation in at least one of said signal paths so that the secondary signals reaching said summing point have a defined time correlation with respect to one another, applying a set of weighting coefficients to the secondary signals propagating along said signal paths, and performing a capturing operation after any filtering or delaying operations so as to provide a weighted signal sum value as a measure of the integrated area Qof the input signal.

Method and apparatus for improving resolution in spectrometers processing output steps from non-ideal signal sources

A method and counter for reducing the background counting rate in gas-filled alpha particle counters wherein the counter is constructed in such a manner as to exaggerate the differences in the features in preamplifier pulses generated by collecting the charges in ionization tracks produced by alpha particles emanating from different regions within the counter and then using pulse feature analysis to recognize these differences and so discriminate between different regions of emanation. Thus alpha particles emitted from the sample can then be counted while those emitted from the counter components can be rejected, resulting in very low background counting rates even from large samples. In one embodiment, a multi-wire ionization chamber, different electric fields are created in different regions of the counter and the resultant difference in electron velocities during charge collection allow alpha particles from the sample and counter backwall to be distinguished. In a second embodiment, a parallel-plate ionization chamber, the counter dimensions are adjusted so that charge collection times are much longer for ionization tracks caused by sample source alpha particles than for those caused by anode source alpha particles. In both embodiments a guard electrode can be placed about the anode's perimeter and secondary pulse feature analysis performed on signal pulses output from a preamplifier attached to this guard electrode to further identify and reject alpha particles emanating from the counter's sidewalls in order to further lower the counter's background.

Ultra-low background gas-filled alpha counter

For pulse processing spectrometers that use a fast channel to detect input pulses, a slow channel to measure the pulses' energies, pileup inspection circuitry pulses, and binning to produce an output spectrum of captured energy values, the correction technique extends the Harms method to produce an estimate <C> of the average ratio of the number of input pulses detected in the fast channel per non-piled-up pulse whose captured energy value is to be binned into the output spectrum and, for each such non-piled-up pulse, adding the value <C> to the corrected output spectrum in the bin dictated by the captured energy value. The uncorrected spectrum is formed in the traditional manner by simply adding 1 to the equivalent bin. Three techniques are disclosed for producing the estimate <C>, a running average, a bucket averaging, and a circular buffer method.

Method and apparatus for producing spectra corrected for deadtime losses in spectroscopy systems operating under variable input rate conditions

A method and apparatus for processing step-like output signals generated by non-ideal, nominally single-pole (&ldquo;N-1P&rdquo;) devices responding to possibly time-varying, pulse-like input signals of finite duration, wherein the goal is to recover the integrated areas of the input signals. Particular applications include processing step-like signals generated by detector systems in response to absorbed radiation or particles and, more particularly, to digitally processing such step-like signals in high resolution, high rate gamma ray (&ggr;-ray) spectrometers with resistive feedback preamplifiers connected to large volume germanium detectors. Superconducting bolometers can be similarly treated. The method comprises attaching a set of one or more filters to the device's (e.g., preamplifier's) output, capturing a correlated multiple output sample from the filter set in response to a detected event, and forming a weighted sum of the sample values to accurately recover the total area (e.g., charge) of the detected event.

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Oakland, CA, United States of America

Michael Momayezi