[en] The IAEA has responded to Member States needs by implementing programmatic activities that provide interested Member States, particularly those in developing countries, with support to increase, and in some cases establish national and regional capabilities for the proper operation, calibration, maintenance and utilization of instruments in nuclear spectrometry applications. Technological advances in instrumentation, as well as the consequent high rate of obsolescence, make it important for nuclear instrumentation laboratories in Member States to keep their knowledge and skills up to date. This publication reviews the current status, developments and trends in electronics and digital methods for nuclear spectrometry, providing useful information for interested Member States to keep pace with new and evolving technologies. All nuclear spectrometry systems contain electronic circuits and devices, commonly referred to as front-end electronics, which accept and process the electrical signals produced by radiation detectors. This front-end electronics are composed of a chain of signal processing subsystems that filter, amplify, shape, and digitise these electrical signals to finally produce digitally encoded information about the type and nature of the radiation that stimulated the radiation detector. The design objective of front-end electronics is to obtain maximum information about the radiation and with the highest possible accuracy. Historically, the front-end electronics has consisted of all analog components. The performance delivered has increased continually over time through the development and implementation of new and improved analog electronics and electronic designs. The development of digital electronics, programmable logic, and digital signal processing techniques has now enabled most of the analog front-end electronics to be replaced by digital electronics, opening up new opportunities and delivering new benefits not previously achievable. Digital electronics and digital signal processing methods are enabling advances in numerous spectrometry applications such as lightweight, portable and hand held radiation instruments, and high-resolution digital medical imaging systems. The objective of this technical meeting was to review the current status, developments and trends in nuclear electronics and signal processing, and their application with various radiation detectors. The meeting discussed the problems faced and the solutions employed, to improve the performances of data acquisition systems and high-tech equipment used for nuclear spectrometry. Presentations made at the meeting elaborated operational experiences with modern signal processing and electronics, and highlighted the latest developments in this field. This publication summarizes the findings and conclusions arising from this technical meeting

[en] Problems involved in supporting high-tech equipment are discussed and solutions employed described. (author)

[en] The phase space of neutron beams - the neutron flux distribution with respect to position, flight direction and energy/wavelength - can be investigated by means of position sensitive detectors in time-of-flight regime, using the pinhole imaging method. These results can serve for experimental verification of numerical simulations, quality assessment of neutron optical components, giving information for quality assurance and corrective actions as well as input data for downstream instrument design and optimization. On-site investigation of highly radiating areas like moderators, cold neutron sources and beam extraction systems, hardly accessible by other means is possible by this procedure. Examples of such experiments performed at the spallation source at Los Alamos Neutron Scattering Center and the reactor at Budapest Neutron Centre are presented. The accuracy and reliability of the obtained detector images can be improved by the development of detector parameters: resolution, limit count rate, detection efficiency and their crossovers. For this purpose, a method is worked out to evaluate the detection depth profile and efficiency of the multiwire proportional detectors with delay-line encoding or parallel readout. A polychromatic, collimated, pulsed beam, tilted with respect to the normal to the detector plane by a known angle is measured. The trace thus recorded is the projection of the beam track through the detector gas chamber. The neutron counts detected in various pixels of this trace is proportional to the number of neutrons absorbed and detected at various gas depths. Measurement of the time of flight allows the determination of the intensity distribution energy dependence. This technique is suitable to adjust the drift voltage to ensure appropriate spectral accuracy of new detectors. The depth detection profile can be determined (number of neutrons detected versus depth and wavelength), as well as the resolution vs. wavelength in one step. (author)

[en] This article illustrates different kinds of problems experienced in operating and maintaining nuclear spectrometry instrumentation in Peru, and describes some solutions used to solve the problems. (author)

[en] After a nuclear instrumentation laboratory is adequately equipped, attention must be given to the ongoing operation and maintenance. This is an important consideration in the production of satisfactory data and quality control. It requires that the maintenance technician or engineer has adequate understanding of each instrument design in order to detect any problem that arises. Nowadays, manufacturers make use of new technology such as microprocessors, microcontrollers, digital signal processors (DSP), field programmable gates arrays (FPGA), programmable logic controller (PLC) to improve their equipment design, thus increasing the efficiency and quality of measurements. These embedded components are designed in a digital configuration which makes them difficult to troubleshoot, once faulty. Therefore, equipment maintenance has evolved from repair to replacement of boards. Boards that are designed based on the new technology can be used to upgrade an existing instrument for a data acquisition, spectrum analyzing, etc. Communication between these components and the computer can be achieved by LabVIEW and with user interfaces designed using a LabVIEW environment. (author)

[en] A high-speed, time-stamping and histogramming data acquisition system for position encoded data has been developed for the new OPAL neutron scattering facility being built by the Australian Nuclear Science and Technology Organization's Bragg Institute. The system described here provides the ability to capture, timestamp, and histogram position encoded neutron data. It provides this capability using the combination of a custom PCI card and a general purpose computer. Using this combination of minimal hardware with a general purpose computer it provides a flexible yet fast architecture that can handle data rates in excess of 2 million events per second. The PCI card integrates the data capture, frame generation, veto logic, and timestamping features and then forwards the information to the computer via the PCI bus for histogramming. The histogramming is then performed on a general purpose computer where DRAM memory can easily be expanded to 16 Gigabytes and beyond. Since it is performed in software it can be easily customized to carry out many different types measurements including kinetic, time of flight, and stroboscopic. Multiple cards can be implemented in a single PC to provide a synchronized scalable system. (author)

[en] Users of nuclear spectroscopy systems desire always-optimal performance to be achieved over a wide range of experimental conditions. The types of detector and their associated pulse signal processing circuitry should be able to tolerate electrical mains power fluctuations that can occur in power distribution grids. The equipment should be able to reduce to a reasonable level, or eliminate, the noise introduced by electrical disturbances that could adversely influence the data analysis. The trend in AC power sources in the United Republic of Tanzania is towards more highly loaded public utilities systems that lead to poor quality of commercial power with time. Electrical disturbance of high content or even the low content disturbances have been identified as among factors that may lead to equipment failure or intermittent errors in data and control. The performance of three commercial spectroscopy systems: Ortec NaI(Tl), CANBERRA HPGe detector, (digital spectrum analyzer) and SILENA HPGe detector, (analog spectrum analyzer) have been evaluated for the purpose of assessing their suitability and tolerance to typical working environments in the United Republic of Tanzania. The analog spectroscopy system had some disadvantages as compared to the digital systems, but it appeared to be preferred for repair services. (author)

[en] Signal processing in the digital domain is known to have better performance than analog processing for pulse shape discrimination of neutron and gamma ray pulses. Digital signal processing (DSP) can synthesize any filter response without the associated signal degradation which happens in the complex analog signal path. Neutron absorption cross-section measurement experiments derive the information of neutron energy from time of flight along a length of channel. Single channel multi-hit time marker approach gives required time resolution and dynamic range for the neutron energies of interest. The predominant gamma background affects the pulse count rates possible in such an experiment. The development of an FPGA based digital signal processing system has been undertaken for this application with counter based multi-hit time marker approach. The inherent parallel architecture of a FPGA implementation will result in better performance compared to DSP processor based implementation. A trigger input to the system indicates the start of the neutron beam which restarts a fast counter. The time of arrival (TOA) for each neutron/gamma ray generates a pulse from a detector. Each pulse is processed in two parallel paths, one for counting and one for pulse shape discrimination. The counting channel latches the output of the fast counter and transfers it to a TOA FIFO. This approach results in higher count rates compared to multi-channel scaling or time-to-analog conversion followed by MCA approach. The pulse shape discriminator is based on the fact that the detector pulses have different decaying tails for neutron and gamma rays. A longer tail is expected for a neutron pulse than for a gamma pulse. Each acquired pulse is passed through a chain of signal processing which compares the total energy with the pulse amplitude to differentiate neutron and gamma pulses. The filtered neutron events are transferred from the TOA FIFO to a Neutron TOA FIFO which is then used for further analysis. The counting channel is much faster than the shape-processing channel thus limiting the event rate. Implementing a number of signal processing channels in parallel improves the event rate. (author)

[en] Gamma spectrometry is widely used as a tool to measure qualitative and quantitative gamma ray emitters in a sample. Container size, sample to detector distance, and sample volumes are well known factors that affecting the quality of gamma spectrometry measurement. However, other factors such as the age of the counting system and surrounding conditions have not much been reported. Therefore, the objective of this study is to find how the age factor and surrounding conditions affecting the quality of the measurements. From this study, it is found that when the age of a system increases, the system tends to have a higher lower limit of detection and poorer linearity. Point source checks found drifting of several parameters such as efficiency, FWHM, and peak position against changing trend of surrounding conditions such as room temperature and humidity. (author)

[en] In this work, the Xilinx XtremeDSP Development kit for Virtex-4 SX FPGA was used as a hardware prototyping platform for development of a multi-channel digital spectrometer. The kit is based on Xilinx Inc.'s most advanced Virtex family of FPGAs, and is equipped with two 14-bit 105 MSPS ADCs and two 14-bit 160 MSPS DACs. The two boards are chained together so that signals from four detectors can be processed simultaneously. In order to utilize the ADCs input range as best as possible, a four channel analog pre-filter has been designed and developed. This pre-filter includes digitally controlled differentiation, pole-zero cancellation, linear amplification and an anti-aliasing filter. The system was tested on several X ray detectors with resistor feedback and transistor reset preamplifiers, and exhibited performances similar to Canberra's InSpector 2000 Digital Signal Processing Portable Spectroscopy Workstation. (author)