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The implication of figures 5-8 is the following: The resolution requirement in a spectroscopy problem is defined by the complexity of the spectrum, especially true in isotopic ratio measurements. This defines what shaping time must be employed for a give detector. The question may then arise as to how fast data may be taken, (how quickly can the measurement be made), or over what range of count ratescan the system operate without excessive peak shift or resolution degradation. (The optimum count rate to take data is the point of maximum throughput). What is shown here is that the digiDART makes it possible to “fine tune” filter settings to the best effect, and that once done, the count rate stability is excellent.The system continues to produce viable data from low rates to beyond the point of maximum throughput, with peak shift of less than 40 eV (0.03%) across the range.

Figure 9

Figures 9 and 10 show peak position

and resolution at low- and high- energy Figure 10 over time. A mixed isotope source was acquired over a period of 5 days: 120 spectra. The count-rate was approximately 1 kHz. The filter setting was 12 S risetime, 0.8 S flat top. The 59 keV and 1332.5 keV peaks were monitored.

At 1332 keV the peak position and resolution drift standard deviations were 0.002% and 2% respectively, while at 59 keV the corresponding results were 0.005% and 0.9%.


A new and innovative digital high performance portable MCA has been developed and tested. In spite of the demands of designing for low power, it has been shown to provide performance at least equivalent to the best laboratory grade, digital spectrometer and the best analog systems. In practical terms there is no longer any trade off in performance for a field system. Indeed this system can be effectively used in fixed installations, where small size/low power, battery backup, local multiple storage, networkability, detector self-diagnostics and data authentication can be assets to the measurement. Its packaging and display provide superior ergonomic features, whereas multi-spectral

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