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The availability of high performance configurable digital processors offers the possibility of real-time implementation of digital least-mean-square analysis methods in nuclear spectroscopy. A particularly simple, efficient and highly precise technique for reducing the mathematical complexity of least-mean-square algorithms used in deriving energy and arrival time of detected events is presented. The method has been theoretically developed and validated through comparison with state-of-the-art digital signal processing techniques. Index Terms--Digital measurements, energy measurement, least mean squares algorithm, time measurement.

The experimental application of a digital technique for high-resolution estimation of occurrence time of detected events is described. In particular, the method that achieves timing precisions well below the sampling time interval is tested for timing of events from scintillation detectors. The validity of the technique is demonstrated both in terms of achieved performances and of implementation simplicity in an electronic architecture based on a FPGA device. Index Terms--Digital processing, field programmable gate array (FPGA), scintillators, timing.

A fully digital trigger technique is presented. It is based on evaluating the occurrence or the absence of an event on a statistical basis. This allows very low-level discrimination for isolated events as well as high time resolving capabilities, i.e., double event discrimination, provided that the events are sufficiently energetic. These two conflicting requirements are met by using a single processing architecture. The theory of the underlying optimum filter and a less resource-hungry processor are carried out and their relative performance compared. Self-calibration and self-optimization of the algorithm with respect to the actual noise conditions have also been implemented. The user can easily adapt to his/her requirements the balance between false triggering reduction, low-level discrimination, and multiple event rejection. Index Terms--Digital spectroscopy, high-resolution spectroscopy, trigger, prediction.

The necessary shapings for optimum processing of signals from radiation detectors can be conveniently obtained by using an analog prefilter followed by an analog-to-digital converter (ADC) and a digital filter. In this paper we analytically calculate the dependence of resolution and efficiency of energy measurements on the characteristics of the analog prefilter architecture. Consequent design rules of the analog stage are derived and different solutions are proposed and discussed. Index Terms--Analog-to-digital conversion, efficiency, digital filter, digital spectroscopy.

We introduce a new filtering method capable of increasing measurement resolution and processed data throughput through a nonstandard baseline restoration technique. An overall optimization of the signal-to-noise ratio and of the processing efficiency is performed and new filters are obtained. The hardware implementation exploits the resources of a FPGA and is not significantly resource-hungrier than standard setups. The experiments confirm theoretical expectations. The obtained resolution is 1.8 keV on the 1.173 MeV peak: This result is an improvement with respect to the one achievable with the standard optimum filter in the same conditions by about a 10% factor; the data rate is improved too.

We present the experimental application and comparison of two methods for the synthesis of digital filters, which represent the state-of-the-art of optimum digital processing of shaped signals with arbitrary constraints in time and frequency domain, and any kind of stationary noise power spectral density. The methods are implemented in experimental measurement setups, and optimum filters are synthesized with regard to assigned constraints (e.g., finite duration, flat top, peaking time, zero area, etc.) and by taking into account the real environmental noise or disturbance present in the system, identified from datasets of simple signal experimental acquisitions. Implementation issues are detailed and basic design rules for digital signal processors based on these techniques are derived. Index Terms--DSP, energy resolution, high-resolution spectroscopy, HPGe detectors, LMS data analysis, optimum digital spectroscopy.

An adaptive serf-calibrating instrument for digital spectroscopy is proposed and demonstrated. Most of the typical processing features (pole-zero cancellation, baseline restoration, and shaping) are digitally implemented and optimized. The main feature of the processor is the capability to serf-calibrate and self-optimize the configurable sections of the whole measurement setup, both digital and analog parts. This is accomplished through automatic dynamic initialization procedures, which make the system particularly user friendly and flexible to varying operative conditions while keeping very high resolution performances. Index Terms--Autocalibration, digital spectroscopy, DSP, FPGA, USB.

A digital technique for high-resolution estimation of occurrence time of detected events is presented. The method achieves timing precisions well below the sampling time interval through a nonrecursive processing strategy. Due to linearity of the procedure, the processing runs online, and the architecture has been implemented in a configurable field programmable gate array (FPGA) device with a very limited resource burden. The method has been validated through processing of simulated and measured data and a full experimental assessment of the technique in an acquisition and processing digital setup for different operative conditions is at present going on. [ABSTRACT FROM AUTHOR]

By exploiting some interesting properties of feedback loops including an analog-to-digital converter (ADC) and a digital-to-analog converter (DAC), it is possible to perform filtering action on both signal and noise in a mixed digital-analog realm, similar to the well-known sigma-delta ADC. In particular, we present a signal conditioning architecture based on this loop, which optimizes the analog-to-digital conversion operation in a high-resolution digital spectrometer. Elimination of pile-up at the ADC input, which minimizes the probability of its saturation as well as minimization of alias effects are achieved with no significant hardware burden and no measurement resolution loss. The filtering action inherent in the loop is used to obtain pole-zero cancellation, to improve the input signal rate, to reduce the effects of quantization noise by pushing it out-of-band, and to enhance the linearity of the converter. The technique has been implemented and validated. [ABSTRACT FROM AUTHOR]