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An amplitude modulated laser radar has been developed by the Italian Agency for New Technologies, Energy and the Environment (ENEA) for periodic in-vessel inspection in large fusion machines. The viewing system is based on a transceiving optical radar using a radio frequency (RF) modulated single-mode 840-nm wavelength laser beam. The sounding beam is transmitted through a coherent optical fiber to a probe, on the tip of which a focusing optics and suitable scanning system, using a silica prism, steers the laser beam in order to obtain a complete 3-D mapping of the in-vessel surface. This paper describes the digital signal processing system used to modulate the laser beam, as well as to measure both the amplitude of the backscattered laser beam and the phase difference between it and the modulation signal. This information, together with the information on the scanning system position, are acquired and then used by the visualization system to produce both 2-D and 3-D images. The system is based on VME boards and directly acquires and processes in real-time three 79.5-MHz RF signals by using a digital receiver and four digital signal processors. The system principles, the mathematical algorithm, and the system architecture are described here after. © 2002, The Institute of Electrical and Electronics Engineers, Inc.

The inspection of the internal wall of the large fusion reactors represents a difficult problem to solve due to the hostile environment, which is characterized by the presence of radiation, temperature, high vacuum and high magnetic field. However, the internal inspection system is essential to verify the status of the components of the first wall and therefore to plan the remote management operations correctly. At the Frascati laboratories, a specific technology was developed that can solve the problem by arriving at a first prototype of a laser measuring system, which passed the conceptual design review phase of ITER. The scanning head of the prototype was based on a rotating prism. More recently a complete overhaul of the system has been made that was based on further experiences of similar systems that have been developed for different fields, such as fine arts and underwater inspection systems. This revision, while maintaining the general concepts of the previous prototype, has completely revised the scanning head. The prism has been replaced with a mirrors based system, thus conceptually avoiding the multiple reflections within the prism itself that limited the accuracy of the old prototype. Furthermore, the new scanning head has been provided with an embedded calibration system with the relative calibration procedures. The new project presently represents an internal development of the Frascati laboratories and has been protected by a patent currently being extended internationally.

Accurate and timely assessment of displacements and/or structural damages in nuclear reactor vessels’ components is a key action in routine inspections for planning maintenance and repairs but also in emergency situations for mitigating consequences of nuclear incidents. Nevertheless, all these components are maintained underwater and reside in high-radiation fields thus imposing harsh operative conditions to inspection devices which must cope with effects such as Cerenkov radiation background, Total Ionizing Radiation (TID), and occlusions in the detectors’ field of view. To date, ultrasonic techniques and video cameras are in use for inspection of components’ integrity and with measurements of volumetric and surface crack opening displacements, respectively. The present work reports the realization of a radiation tolerant laser scanner and the results of tests in a nuclear research reactor vessel for acquisition of 3D models of critical components. The device, qualified for underwater operation and for withstanding up to 1 MGy of TID, is based on a 515 nm laser diode and a fast-scanning electro-optic unit. To evaluate performances in a significant but controlled environment, the device has been deployed in the vessel of a research reactor operated by ENEA in the Casaccia Research Centre in Rome (Italy). A 3D model of the fuel rods assembly through a cooling water column of 7 m has been acquired. The system includes proprietary postprocessing software that automatically recognizes components of interest and provides dimensional analysis. Possible application fields of the system stretch to dimensional analysis also in spent nuclear fuel storage pools.

This paper describes the high-priority testing activities supporting the ITER radial neutron camera (RNC) design, performed by a consortium of European institutes within a framework contract placed by fusion for energy, the ITER European Domestic Agency. The main role of the RNC is to measure the uncollided 14- and 2.5-MeV neutrons from deuterium-tritium and deuterium-deuterium fusion reactions through an array of flux monitors/spectrometers located in collimated lines of sight viewing the plasma through the ITER equatorial port plug #1. The line-integrated neutron fluxes will be used to evaluate, through reconstruction techniques, the radial profile of the neutrons emitted per unit time and volume (neutron emissivity) and, therefore, the neutron yield and the alpha particles' birth profile. The activity of high-priority testing is dedicated to the preparation and the design of experimental test environment, the conduction of appropriate tests and reporting of test results for the high-priority prototypes, clarifying or verifying the expected key function and system behavior, and enhancing learning on specific issues (potential showstoppers). © 1973-2012 IEEE.

In several applications, such as collision avoidance, it is necessary to have a system able to rapidly detect the simultaneous presence of different obstacles. In general, these applications do not require high resolution performance, but it is necessary to assure high system reliability also within critical scenarios, as in the case of partially transparent atmosphere or environment in presence of multiple objects (implying multiple echoes having different delay times.) This paper describes the algorithm, the architecture and the implementation of a digital Light Detection and Ranging (LIDAR) system based on a chirped optical carrier. This technique provides some advantages compared to the pulsed approach, primarily the reduction of the peak power of the laser. In the proposed architecture all the algorithms for signal processing are implemented using digital hardware. In this way, some specific advantages are obtained: improved detection performance (larger dynamics, range and resolution), capability of detecting multiple obstacles having different echoes amplitude, reduction of the noise effects, reduction of the costs, size and weight of the resulting equipment. The improvement provided by this fully digital solution is potentially useful in different applications such as: collision avoidance systems, 3D mapping of environments and, in general, remote sensing systems which need wide distance and dynamics. © 2016 China Ordnance Society

In several nuclear applications, scintillators, coupled with a photomultiplier and pulse amplifier, are used in order to detect high energy particles, i.e. neutrons and gamma rays. The different particles incident on the scintillator produce electrical pulses having different shape; moreover, the amplitude of these signals is related to the particles energy. The electrical pulses of the scintillator chain are acquired by digital systems that, generally, perform a triggered acquisition consisting of a stream of pulse windows. The aim of this study is the development of a simplified clustering algorithm able to produce reference patterns in compliance with the pattern recognition algorithm based on the matched filter technique, starting from a stream of pulses generated by particles having different energy and type. This paper contains a general description of the clustering algorithm and of the main customizations performed for the scintillator signals. In order to test in real case the efficiency, the algorithm has been applied on the data acquired during a radiation test performed at Frascati Neutron Generator for Stilbene scintillator. The results show that this algorithm works properly, deriving the centroids of the clusters representing the neutron and gamma shapes, together with their occurrences in the analysed data stream.

To achieve the aim of the ITER Radial Neutron Camera Diagnostic, the data acquisition prototype must be compliant with a sustained 2 MHz peak event for each channel with 128 samples of 16 bits per event. The data is acquired and processed using an IPFN FPGA Mezzanine Card (FMC-AD2-1600) with 2 digitizer channels of 12-bit resolution and a sampling rate up to 1.6 GSamples/s mounted in a PCIe evaluation board from Xilinx (KC705) installed in the host PC. The acquired data in the event-based data-path is streamed to the host through the PCIe x8 Direct Memory Access (DMA) with a maximum data throughput per channel is 0.5 GB/s of raw data (event base), 1 GB/s per digitizer and up to 1.6 GB/s in continuous mode. The prototype architecture comprises an host PC with two KC705 modules and four channels, producing up to 2 GB/s in event mode and up to 3.2 GB/s in continuous mode. To reduce the produced data throughput from host to ITER databases, the real-time data compression was evaluated using the LZ4 lossless compression algorithm, which provides compression speed up to 400 MB/s per core. This paper presents the architecture, implementation and test of the parallel real-time data compression system running in multiple isolated cores. The average space saving and the performance results for long term acquisitions up to 30 minutes, using different data block size and different number of CPUs, is also presented., 21st Real Time Conference, June 9th - 15th, Colonial Williamsburg, Virginia, United States

The ITER Radial Neutron Camera (RNC) Data Acquisition (DAQ) prototype is based on the PCIe protocol as the interface to be used between the I/O unit and the host computer, allowing the scalability of the final RNC DAQ system. The prototype architecture comprises two digitizer modules with two channels in each, installed in the host computer and the maximum produced data throughput is up to 1.6 GB/s per board, allowing a sustainable 2 MHz peak event to cope with the long plasma discharges, up to half an hour. The Linux Device Driver provides the interface between the hardware and the host applications running on a high-performance computer, which receives the acquired data through the Direct Memory Access (DMA) channels. The preliminary tests show that the Linux kernel miss some hardware interrupts when the time between interrupts is in the microsecond scale, which implies data loss if a traditional read technique based on interrupt handling is implemented. The direct usage of the polling mechanisms to retrieve the data is not suitable as the variable event rate over the same discharge does not allow to define an optimal fixed-time to retrieve data and identify missing data packets. This contribution presents the architecture, implementation and test of a different device driver approach using the polling mechanism which improves the performance and reliability. This allows the device driver to automatically check and transfer missing data blocks, recovering the data losses transparently for the host applications. The performance results for tests with different event data rates and duration up to an hour are also presented.

The In-Vessel Viewing System is a 3D laser scanning system which will be used to inspect the blanket first wall in ITER. To make the IVVS probe design compatible with the harsh environmental conditions present in ITER, a test campaign was performed in 2012-2013 to verify the adequacy of the main components of the IVVS probe. The IVVS components inspected were an optical encoder, passive components and two customized ultrasonic piezoceramic motors that were instrumented with various sensors. A general architecture of the Data Acquisition and Control System (DACS) was defined and then specialized for each test. To be suitable for this test campaign, the DACS had to host various I/O modules and to properly interface the driver of the customized piezo motors, in order to permit the full control of the test and the acquisition of experimental data. This paper presents the instrumentation solutions designed and implemented for different facilities constraints and the related DACS developed in four specialized versions for the described test campaign. © 2015 Elsevier B.V. All rights reserved.

The main role of the ITER Radial Neutron Camera (RNC) diagnostic is to measure in real-time the plasma neutron emissivity profile at high peak count rates for a time duration up to 500 s. Due to the unprecedented high performance conditions and after the identification of critical problems, a set of activities have been selected, focused on the development of high priority prototypes, capable to deliver answers to those problems before the final RNC design. This paper presents one of the selected activities: the design, development and testing of a dedicated FPGA code for the RNC Data Acquisition prototype. The FPGA code aims to acquire, process and store in real-time the neutron and gamma pulses from the detectors located in collimated lines of sight viewing a poloidal plasma section from the ITER Equatorial Port Plug 1. The hardware platform used was an evaluation board from Xilinx (KC705) carrying an IPFN FPGA Mezzanine Card (FMC-AD2-1600) with 2 digitizer channels of 12-bit resolution sampling up to 1.6 GSamples/s. The code performs the proper input signal conditioning using a down-sampled configuration to 400 MSamples/s, apply dedicated algorithms for pulse detection, filtering and pileup detection, and includes two distinct data paths operating simultaneously: i) the event-based data-path for pulse storage; and ii) the real-time processing, with dedicated algorithms for pulse shape discrimination and pulse height spectra. For continuous data throughput both data-paths are streamed to the host through two distinct PCIe x8 Direct Memory Access (DMA) channels., Comment: 6 pages, 10 figures, 21st IEEE Real Time Conference (RT-2018), Colonial Williamsburg, 9-15 June 2018

In ENEA Frascati research centre an experimental fusion machine called Frascati Tokamak Upgrade (FTU) is in operation since 1990. The plasma discharge phase of FTU is driven by the dedicated system FSC-U (Fast Sequence Control upgraded), which has been developed in order to send all the necessary commands to the power plants, feeding the toroidal and poloidal coils during the plasma discharge, meanwhile controlling the correct outcome and recording all the events with time resolution of the order of 20 microseconds. In case of incorrect execution of the sequence the system is able to safely shutdown the plants and the plasma pulse. The present FSC-U system is based on an up to date, off the shelf, hardware platform, and it is equipped with an integrated configurator and a custom command and control sequence programming language, allowing the user to program the sequences by linking the execution times of the commands and of the state verifications each other or to global time parameters. The FSC-U system has been tailored to the I/O FTU needs and time scale, but was conceived with the aim of more powerful up-grades. Now is well in progress a design phase in order to extend the system, increasing of many times the system IO capability and, above all, reaching time resolution of one microsecond. The FSC-U system is a command sequencer that include also some functions and concepts of the interlock and protection system, in the new design this functionality was further enhanced in order to comply with the more demanding applications of the large fusion reactors. © 2017 IEEE.

Measurements of total radiated power are very important in tokamak plasmas, especially in the divertor region where they are required for heat flux active control. Bolometric detectors based on metal foils are used as sensors. The signal readout is provided by an electronic system which drives processes and acquires the signals from the resistive bridge-based bolometer. A project for a new electronic system is being carried on at ENEA Frascati Laboratories, aimed to develop an architecture and a system sufficiently flexible in order to be applied to large fusion devices, such as DTT and ITER. The project, conceived for high reliability and lasting time levels, is based on FPGA boards and a completely digital lock-in. A prototype has been recently tested both in the laboratory and on FTU plasma. A key point of the project is the capability of on-line calibration. The paper describes the architecture of the project for the bolometric diagnostic and the analysis of the first results on FTU plasma.

In ENEA Frascati research centre an experimental fusion machine called Frascati Tokamak Upgrade (FTU) is in operation since 1990. During the experimental activity, the automatic control and synchronization of many plants are required. The FTU control system [1] includes many sub-systems having different roles [2, 3]. In particular, a Fast Sequence Control (FSC) hardware is necessary to drive the tokamak power plants and to detect the errors in the fast control sequence during the plasma discharge. The FSC system was designed and realized in 1980s and is still in operation. Due to the obsolescence of some hardware components, a new project for the FSC Upgrade (FSCU) has been started. The project includes a new architecture based on up-to-date commercial hardware and dedicated firmware and software. In the present paper the architecture and the functions of the Fast Sequence Control - Upgrade system is described, along with the main differences between the two systems. © 2015 IEEE.

An amplitude modulated laser radar has been developed by the Italian Agency for New Technologies, Energy and the Environment for periodic in-vessel inspection in large fusion machines (International Thermonuclear Experimental Reactor). The system is able to obtain a complete three-dimensional mapping of the in-vessel surface. A first digital signal processing system was developed to modulate the laser beam and to detect both the amplitude of the backscattered light and the phase difference between it and the modulation signal. This system is based on commercial digital receiver and parallel digital signal processing boards on a VME bus. It reaches a speed of 100 K measures/s, showing good accuracy and stability. Starting from this, a further development has been done to increase the speed up to 2.328 M measures/s. Reaching the submicrosecond speed was necessary to implement the mathematical algorithm in a highly parallel hardware architecture using a field programmable gate array (FPGA). Based on the good results of the previously developed system, it was decided to maintain the same acquisition front-end though using the last release of analog-to-digital converters, to increase the operating frequency from 80 up to 200 MHz. The software algorithm previously used was completely redesigned and optimized to be used in the FPGA hardware architecture.

The In Vessel Viewing System (IVVS) is an optical radar with sub milimetrical resolution that will be used for imaging and metrology pourposes in ITER. The electronics of the system is based on a Digital Radar Electronics developed in ENEA Frascati laboratories during the past years. Until the present study, the system was based on amplitude modulation technique having double-modulation frequency. The power of the laser is sinusoidally modulated and the distance of the points scanned by the laser beam is obtained measuring the phase difference between outgoing and echo signals. Recently a triple-modulation radar electronics version and an algorithm able to solve the range disambiguation were developed. The aim of the upgrade was the increase of the robustness in the range disambiguation. The paper briefly describes the updates carried out on the Digital Radar Electronics and extensively the test results obtained by comparing the performance of the triple modulation versus the double modulation techniques. © 2015 Elsevier B.V. All rights reserved.

In ITER it is foreseen the use of the In Vessel Viewing System (IVVS), whose scanning head is a 3D laser imaging system able to obtain high-resolution intensity and range images in hostile environments. The IVVS will be permanently installed into a port extension, therefore it has to be compliant with ITER primary vacuum requirements. In the frame of a Fusion for Energy Grant, an investigation of the expected IVVS metrology performances was required to evaluate the device capability to detect erosions on ITER first wall and divertor and to estimate the amount of eroded material. In ENEA Frascati laboratories, an IVVS probe prototype was developed along with a method and a computational procedure applied to a reference erosion plate target simulating ITER vessel components and their possible erosions. Experimental tests were carried out by this system performing several scans of the reference target with different incidence angles, estimating the eroded volume and comparing this volume with its true value. A dedicated study has been also done by changing the power of the laser source; a discussion about the quality of the 3D laser images is reported. The main results obtained during laboratory tests and data processing are presented and discussed. © 2014 EURATOM-ENEA Association.

The paper describes the key concepts of the In Vessel Viewing System probe in phase of design refinement in ENEA Frascati laboratories and presents an integrated survey both on the design activities and the numerous test activities that have been performed to characterize the system and to verify the compliance of its key elements with the ITER environmental conditions. © 2013 IEEE.

The non-intrusive density measurement of the thin plasma produced by a mini-helicon space thruster (HPH.com project) is a challenge, due to the broad density range (between 1016 m-3 and 1019m -3) and the small size of the plasma source (2 cm of diameter). A microwave interferometer has been developed for this purpose. Due to the small size of plasma, the probing beam wavelength must be small (λ=4 mm), thus a very high sensitivity interferometer is required in order to observe the lower density values. A low noise digital phase detector with a phase noise of 0.02° has been used, corresponding to a density of 0.5 × 10 16 m-3. © 2013 American Institute of Physics.

The FTU (Frascati Tokamak Upgrade) requires a bolometer diagnostic in order to measure the total plasma radiation. The current diagnostic architecture is based on a full analog multichannel AC bolometer system, which uses a carrier frequency amplifier with a synchronous demodulation. Taking into account the technological upgrades in the field of electronics, it was decided to realize an upgrade for the bolometric electronic system by using a hybrid analog/digital implementation. The new system developed at the ENEA Frascati laboratories has many improvements, and mainly a massive system volume reduction, a good measurement linearity and a simplified use. The new hardware system consists of two subsystems: the Bolometer Digital Control and the Bolometer Analog System. The Bolometer Digital Control can control 16 bolometer bridges through the Bolometer Analog System. The Bolometer Digital Control, based on the FPGA architecture, is connected via Ethernet with a PC; therefore, it can receive commands settings from the PC and send the stream of bolometric measurements in real time to the PC. In order to solve the cross-talk between the bridges and the cables, each of the four bridges in the bolometer head receives a different synthesized excitation frequency. Since the system is fully controlled by a PC GUI (Graphic User Interface), it is very user friendly. Moreover, some useful features have been developed, such as: auto off-set correction, bridge amplitude regulation, software gain setting, real time visualization, frequency excitation selection and noise spectrum analyzer embedded function. In this paper, the hardware and software system architectures are described and some tests of the developed system are presented, with a related statistical analysis. © 2013 Euratom-ENEA Association sulla Fusione.