[en] Published in summary form only

[en] This paper studies the impact that the outcome of new digital architectures has brought to dead time of spectrometers. Special emphasis is given to the performance comparison between conventional spectrometers and the most important architectures usually adopted in the digital solutions. Dead-time analysis is accomplished through a dedicated numerical simulation application developed with the purpose of optimizing the digital architecture performance taking into account parameters such as the incident rate of events, the existence of pulse pile-up or the complexity of the processing algorithm used during the digital pulse processing. Results of simulations using a real time multiprocessor platform (Digital Pulse Processing-M8) are presented and design options are justified accordingly

[en] This paper presents innovative algorithms for optimum filtering, rise-time discrimination and proper correction of solid-state detector pulses based on digital pulse processing (DPP) techniques and on a Linear Sliding Method. These techniques allow a significant improvement on the spectral resolution by taking into account both the electronic noise and the pulse rise time fluctuations mainly due to the incomplete charge collection in the CZT crystal. In order to develop these algorithms pre-amplified pulses coming from a planar XR100-T detector (Amptek) were digitized by a 12-bit PCI acquisition card (125 MHz) hosted by a PC platform. The presented results show that, due to the possibility of fine adjustments on the discrimination and correction parameters during the processing stage, this flexible DPP implementation leads to significantly better results than the analog hardware discrimination solution. Comparative analysis of Am-241 spectra show a significant reduction of the low-energy 'tail' on the 59.5 keV photo-peak

[en] The response of a cadmium zinc telluride (CZT) detector to X-rays with energies around the Zn, Cd and Te K-absorption edges was investigated. The energy non-linearity in the detector response at the K-edges is less than 0.1%, within the experimental errors. No abrupt variation in both the w-value and the detector energy resolution was observed at the K-edges, a behaviour consistent with the absence of intrinsic non-linearity effects in CZT. Within the accuracy of our measurements, we conclude that there are no non-linearity effects in CZT semiconductors at the Zn, Cd and Te K-edges

[en] The ITER project demanding operating conditions, as well as other enabling experiments in relevant fusion projects, present new challenges to the diagnostics, control and instrumentation. The most critical requirements relate to the high acquisition rates (up to some gigasample per second), high physical event rate (up to several megaevents per second), need to handle enormous quantities of data in long experimental pulses (up to 30 minutes) and highly complex control and diagnostic algorithms. Radiation hardness of all equipment involved must also be taken into account for high magnetic fields as well as neutron irradiation in the fusion devices port cells.

sp0002^>The implementation of state-of-the-art designs were tested both with in-house built prototypes and complete systems installed in the major international fusion experiments. The main technologies used include Advanced Telecommunications Computing Architecture (ATCA), high speed electronic devices for signal digitization, complex real-time algorithms for physics analysis, control and data compression implemented in high-performance computing using field-programmable gate arrays and multicore processor architectures.

sp0003^>The control and data acquisition group at Instituto de Plasmas e Fusão Nuclear (Instituto Superior Técnico - Lisboa) has conducted several projects and studies for the development of reliable high-performance processing tools and instrumentation for the diagnostics and control of fusion devices capable of complying with the most demanding requirements.