Abstract: A spectrometer having improved energy resolution by correcting for error introduced by charge carrier trapping. By monitoring the shape of the pulses produced by the detector, a digital filter is adjusted to improve the energy resolution. The adjustment is performed manually by an operator or automatically by an automatic optimizer circuit that modifies the digital filter until the spectral peaks have a width and shape matching the desired characteristics, which are a minimum width and a substantially symmetrical shape. By correcting for the energy loss associated with long rise time events, the charge-trapping correcting spectrometer produces spectral peaks with improved energy resolution.

Abstract: A method and apparatus for improving the sensitivity of a position sensitive gamma ray detector and gamma camera. To obtain good position resolution, small effective detector elements are required. However, such small detector elements cause nearly all the gamma rays interacting by Compton scattering to be lost, i.e., they will not contribute to forming the image. The method and apparatus of the present invention takes advantage of the fact that when an incoming gamma ray of known energy is completely absorbed in two separate detector elements the sum of the energy depositions identifies this gamma ray as a valid event. Furthermore, for incoming gamma rays having energies less than 511/2 keV the position where the smallest energy is deposited is the first interaction site and therefore this position can also contribute to forming the image. Alternatively, both interaction sites can be used to form the image, thus improving sensitivity but increasing background noise compared with the preferred embodiment.

Abstract: A method and apparatus for improving the sensitivity of a position sensitive gamma ray detector and gamma camera. To obtain good position resolution, small effective detector elements are required. However, such small detector elements cause nearly all the gamma rays interacting by Compton scattering to be lost, i.e., they will not contribute to forming the image. The method and apparatus of the present invention takes advantage of the fact that when an incoming gamma ray of known energy is completely absorbed in two separate detector elements the sum of the energy depositions identifies this gamma ray as a valid event. Furthermore, for incoming gamma rays having energies less than 511/2 keV the position where the smallest energy is deposited is the first interaction site and therefore this position can also contribute to forming the image. Alternatively, both interaction sites can be used to form the image, thus improving sensitivity but increasing background noise compared with the preferred embodiment.

Abstract: An automatic pole-zero (APZ) adjustment circuit for an ionizing radiation spectroscopy system. An output of a preamplifier is sampled to identify the decay time constant of the preamplifier output. A correction based upon the identified decay time constant is generated by a correction signal generator and applied through either an analog pole-zero adjustment network or a programmable digital shaping filter to accomplish pole-zero correction.

Abstract: A differential correction apparatus for use with a spectroscopy device. The spectroscopy device simultaneously produces two histograms corresponding to the spectrum acquired. The first histogram contains the counts recorded by a differential correction method (DCM), giving the best estimate of the counts per channel in the absence of dead time. The second histogram is the error spectrum, giving the variance of the counts in each channel of the first spectrum. The two spectra have the same size, true acquisition time, and energy calibration with the only difference being the number of counts in each channel. By obtaining both histograms, it is possible to both obtain an accurate spectrum when the energy peaks have varying decay times and retain the necessary information about the spectrum to allow the statistical error to be calculated.

Abstract: An automatic pole-zero (APZ) adjustment circuit for an ionizing radiation spectroscopy system. An amplitude histogram of an acquired spectrum is obtained. The shape of a selected peak from the amplitude histogram is analyzed for peak shape distortion indicating the existence of undershoot or overshoot. An analog correction signal generated by a pole-zero adjustment network is added to cancel existing undershoot or overshoot, thereby minimizing distortion of the peak shape. In an alternate embodiment, the correction signal is a digital transformation algorithm applied to a programmable digital shaping filter, thereby digitally minimizing distortion of the peak shape.

Abstract: A method for improving the speed of convergence to sub-least-significant-bit accuracy and precision in a digital signal averager when the measurements are averaged over many samples where the noise inherent in the signal is not large compared to 1 LSB. A slider offset circuit implements the method which adds offsets to an analog input signal acquired from an analog sensor. The slider offset circuit compensates for limitations in the resolution of an analog-to-digital converter by adding a sub-least-significant-bit offset to the input signal. Similarly, the slider offset circuit compensates for the differential non-linearity using a Gatti offset which are whole number multiples of the average voltage bin width. Speed of convergence to sub-LSB accuracy is further improved by employing non-consecutive increments in the two sliders.