INSPECTOR-2000: A DSP-BASED, PORTABLE, MULTI-PURPOSE MCA

Various in-situ gamma spectroscopy applications need a versatile, multi-purpose, portable multi-channel analyzer (MCA). Recently, Canberra has introduced the Inspector-2000 for this purpose. It uses digital signal processing (DSP) technology and weighs only about 1.2 kg. It also supports CdTe, NaI and Ge detectors. Due to its use of DSP technology, the Inspector-2000 also provides a longer battery life, a better detector resolution and a better temperature stability than most portable MCAs. This paper includes a short description of the Inspector-2000 MCA and its performance characteristics compared to an analog MCA.

Introduction

Decommissioning and decontamination work, environmental restoration, nuclear safeguards and many other in-situ applications need a versatile, multi-channel analyzer (MCA) that can be taken to the field to make measurements. Such an MCA must be lightweight, rugged, battery operated and temperature stable. In addition, it should be able to handle a large range of count rates without deterioration in the spectrum characteristics. For many years, Canberra has sold the InSpector MCA¹ for this purpose. It has been successfully used for many types of field measurements. We now introduce its successor, the Inspector-2000. Unlike the original Inspector MCA, which uses analog electronics, the Inspector-2000 uses digital signal processing (DSP) technology. It weighs only about 1.2 kg, has a long battery life, and thus allows taking DSP technology to the field. It supports NaI, CdTe and Ge detectors and has a significantly better throughput than an MCA that is based on analog technology. It also provides a better detector resolution, particularly at higher count rates, and its temperature stability is much better.

With traditional spectrometer systems the signal from the detector is first amplified by an analog amplifier and then digitized by an analog-to-digital converter (ADC). In digital signal processing (DSP) systems, the detector signal is digitized directly after the preamplifier, and the digitized data is then filtered and amplified using digital processing algorithms. Previously published studies have shown that both throughput and resolution at high input count rates are better with a DSP system than with a traditional analog system^2,3. Significant benefits from the point of view of sample throughput can also be achieved with low to moderate count rates⁴. All of this data has been obtained with laboratory DSP systems. 

In designing and building the Inspector-2000, we have included a number of brand new concepts⁵ and not only copied the previous Canberra DSP designs, such as the DSA-2000 MCA and the model 2060 and model 9660 NIM modules. On top of everything, the Inspector-2000 is a portable system. Therefore, it is very important to establish the performance characteristics of the Inspector-2000. To allow for an easy comparison, we have performed many of the same types of measurements that were published for the previous DSP designs6. These include throughput and resolution measurements for both small and large detectors. In this paper, we have included a short description of the MCA itself, and describe the results of these measurements.