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A Status line provides parameter display; with the user able to choose any two from: cursor energy, location, live time, live time remaining, real time remaining, battery life remaining, Count rate, Count rate in ROI, or counts. A real time Peak Information function reports centroid, FWHM, Net and Gross area for the ROI where the cursor is positioned.

A two-point energy calibration of channel and FWHM can be done at any time from the keypad. The user can define from 1 to 9 regions for the Nuclide activity display. The activity with uncertainty is calculated and reported in real time. Multiple acquisition presets are provided: live time, real time, integral peak count, peak area, MDA and uncertainty.

SMART-1 HPGe Detector Support

Figure 3 The portable MCA

spectral display

The MCA supports HPGe detectors with the SMART-1 technology, as well as “traditional” HPGe detector systems. The SMART-1 HPGe detector supports many advanced features, as described in another paper5.

Associated Software

The unit is supported by the ORTEC standard MAESTROTM MCA Emulator. The easy setup has been extended to support all the instrument functions via the USB hardware interface. All of the setup can be done by MAESTRO or by the standalone digiDART. The philosophy is that it is easier to setup the instrument for use “back at base” using a large-screen PC, but all the settings may be changed in the field, where there is no PC available.

The settings can be protected by password, so the settings can not be inadvertently changed. Two levels of passwords are used to allow different levels of access control. If either level of password is set, the password must be entered when the MCA is powered on.

The instrument is compatible with all of the ORTEC analysis packages, including versions of MGA++ and PC/FRAM Isotopic ratio packages, and products for the ISOTOPIC analysis of soils and containers as well as general purpose gamma-analysis packages. To assist the developers of custom or in-house systems, programmer toolkits are available6.

Performance data

In a recent LANL evaluation7, the latest ORTEC digital laboratory spectrometer, the DSPEC Plus was evaluated and considered to be “highly recommended.” It may therefore be considered as a suitable digital benchmark for comparison purposes. The ORTEC 672 Spectorscopy Amplifier has long been considered as a performance benchmark for use in analog systems. In figure 4, the digiDART performance was compared to the DSPEC Plus and an analog system incorporating the 672 and a Canberra 8076 450 MHz Wilkinson ADC under conditions which are similar to those pertaining to many safeguards measurements. The data were taken with an ORTEC 500 mm2

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