Search

Square Kilometer Array (SKA)-Low is the radio telescope operating in the lowest frequency band of the SKA, from 50 up to 350 MHz. It consists of 512 stations, each composed of 256 dual-polarization log-periodic antennas for a total of 262,144 independent signal paths. The low-frequency aperture array (LFAA) is the portion of the SKA-Low telescope including the antennas and the related electronics. Signal processing is hosted in a temperature controlled and shielded facility: the central processing facility (CPF), for all the core stations, or remote processing facilities (RPF), for stations in the array arms, to limit the maximum fiber length. Such a geographically distributed and interconnected radio telescope, spanning ∼65 km in diameter, requires that frequency and timing reference signals are distributed to the processing facilities with high stability and precision to ensure the required system performances. We present the realization of the clock and pulse per second distribution network inside the LFAA signal processing cabinet where subracks containing signal acquisition boards are housed. We describe the different parts of the chain, and we report on the total jitter introduced by this structure.

The design and development process for the Square Kilometre Array (SKA) radio telescope’s Low Frequency Aperture Array component was progressed during the SKA pre-construction phase by an international consortium, with the goal of meeting requirements for a critical design review. As part of the development process a full-sized prototype SKA Low ‘station’ was deployed – the Aperture Array Verification System 1 (AAVS1). We provide a system overview and describe the commissioning results of AAVS1, which is a low frequency radio telescope with 256 dual-polarisation log-periodic dipole antennas working as a phased array. A detailed system description is provided, including an in-depth overview of relevant sub-systems, ranging from hardware, firmware, software, calibration, and control sub-systems. Early commissioning results cover initial bootstrapping, array calibration, stability testing, beam-forming, and on-sky sensitivity validation. Lessons learned are presented, along with future developments.

A novel version of digital hardware Italian Tile Processing Module (ITPM) 1.6 has been released for the Low-Frequency Aperture Array (LFAA) component of the Square Kilometre Array (SKA). This back-end includes two plugged-in main blocks, as an analog device , the Pre-ADU board, and an Analog to Digital Unit (ADU), a 6U board containing sixteen dual-inputs Analog to Digital Converters and two Field Programmable Gate Array (FPGA) devices, capable of digitizing and processing 32 RF input signals (50-650 MHz). We present the main features of the upgrade of the board compared to previous versions: there are new and high performance components improving processing capability, mechanical changes matching the design of the housing sub-rack and finally a general reduction of the overall power consumption. The ITPM ADU 1.6 version, now in engineering phase together with its sub-rack system, is currently the last prototype before the design of the industrial line for mass production, necessary for the LFAA deployment. Results of system performances will be presented.

The SKA LOW telescope is an interferometer composed of 512 stations. Each station consists of 256 electronically steered antennas. The Low Frequency Aperture Array is the portion of the SKA-LOW telescope including the antennas and the related electronics. The LFAA signal processing chain amplifies, transports and combines the signals from the antennas composing each station into a coherent beam. Beamforming is performed in the frequency domain, with stringent requirements on bandpass flatness, linearity in a RFI contaminated spectral region, and allowed signal degradation. We adopted an architecture including a highly optimized oversampled polyphase filterbank for channelization, and a distributed network beamformer. The system has been validated as part of the Aperture Array Verification System, a single station operating at the SKA site in Western Australia.

The signal processing firmware that has been developed for the Low Frequency Aperture Array component of the Square Kilometre Array is described. The firmware is implemented on a dual FPGA board, that is capable of processing the streams from 16 dual polarization antennas. Data processing includes channelization of the sampled data for each antenna, correction for instrumental response and for geometric delays and formation of one or more beams by combining the aligned streams. The channelizer uses an oversampling polyphase filterbank architecture, allowing a frequency continuous processing of the input signal without discontinuities between spectral channels. Each board processes the streams from 16 antennas, as part of larger beamforming system, linked by standard Ethernet interconnections. There are envisaged to be 8192 of these signal processing platforms in the first phase of the Square Kilometre array so particular attention has been devoted to ensure the design is low cost and low power., 19 pages

The Square Kilometre Array (SKA) [1] telescope consists in its first phase of two arrays, a dish array to be constructed in South Africa and a low frequency aperture array to be constructed in Western Australia. The aperture array, SKAI-Low, will consist of 512 stations, each with 256 wide bandwidth log periodic antennas. The frequency range of SKAI-Low is 50 to 350 MHz. The Low Frequency Aperture Array (LFAA) consortium is tasked to design the station, the infrastructure around them and the station signal processing.

A novel digital hardware platform has been designed for the Low Frequency Aperture Array (LFAA) component of the Square Kilometre Array (SKA). This board, called Analog Digital Unit (ADU), is a 6U board containing sixteen dual-inputs Analog to Digital Converters (ADC) and two Field Programmable Gate Array (FPGA) devices, capable of digitizing and processing 32 RF input signals. We present the main features of the board and the signal processing firmware that has been developed for LFAA. Although the ADU has been conceived mainly for the low frequency band (50–350 MHz), its use has been proved effective also for higher frequencies (375-650 MHz). In this paper we describe also the application of ADU as the digital acquisition and processing system for PHAROS2, a cryogenically cooled 4–8 GHz Phased Array Feed (PAF) demonstrator. The final part is focused on the future developments of the board.

A signal processing hardware platform has been developed for the Low Frequency Aperture Array component of the Square Kilometre Array (SKA). The processing board, called an Analog Digital Unit (ADU), is able to acquire and digitize broadband (up to 500[Formula: see text]MHz bandwidth) radio-frequency streams from 16 dual polarized antennas, channel the data streams and then combine them flexibly as part of a larger beamforming system. It is envisaged that there will be more than 8000 of these signal processing platforms in the first phase of the SKA, so particular attention has been devoted to ensure the design is low-cost and low-power. This paper describes the main features of the data acquisition unit of such a platform and presents preliminary results characterizing its performance.

Nowadays the reliability issues of SRAM-based Field Programmable Gate Arrays (FPGAs) operating in harsh environments are well understood. One major effect is Single Event Upsets (SEUs), which are able to invert the stored logical value in flip-flops and memory cells. This issue is more serious when the affected memory cells are part of the configuration memory used for programming the circuit functionality. The consequences may be alterations of the circuit functionality causing errors which may only be corrected by reprogramming the device. For a better understanding of the robustness of programmed circuits, this paper compares two decoders for Error Correction Codes (ECCs). A Hamming Decoder and a One-Step Majority Logic Decoder (OS-MLD) for the Difference-Set Cyclic Codes (DSCC) are analyzed yielding surprisingly unexpected results for their SEU susceptibility, which are interesting for application designers.

Reliability is a major concern for electronic circuits, especially for those that operate in harsh environments. One source of problems are Single Event Upsets (SEU), which change the value of flip flops and memory cells. SEUs are a major issue for SRAM-based Field Programmable Gate Arrays (FPGAs), as they may alter the circuit functionality, creating errors that will only be removed if the device is reprogrammed. The cost of traditional techniques to deal with SEUs, like triplication, can be excessive in some applications. One example are Space systems, in which power consumption and weight are limited. In those cases, the use of ad hoc protection techniques that can reduce the cost is interesting. In this paper, new protection techniques for adaptive equalizers implemented in SRAM-based FPGAs are presented. The proposed techniques use the knowledge of the equalizer to provide effective protection at a lower cost. The results show a reduction of up to 70% in the use of resources in comparison to the commercial XTMR solution.

The paper discusses the experimental validation of fault injection analyses performed with the FLIPPER tool. Failure probabilities obtained by fault injection were compared against failure probabilities obtained at accelerated proton testing of a benchmark design provided by the European Space Agency.

A 100 Msamples/s 14-bit sampling analog-to-digital converter has been used to perform digital pulse-shape acquisition of signals collected from CHIMERA telescopes. Two different kinds of tests have been carried out to check the performances. The signals from a typical CHIMERA detection cell have been collected using both a standard CHIMERA electronic chain up to the amplifier, and a very simple analog front end, basically reduced to the preamplifier. The obtained on-beam and on-line results are presented.

The new detector CHIMERA, in its final 4π configuration, has been installed at Laboratori Nazionali del Sud (LNS) in Catania in January 2003. Beams of different energies ranging from protons to Au ions were delivered by the Tandem and the Super Conducting Cyclotron for nuclear reaction studies, in agreement with the approval of the Scientific Advisory Committee of LNS. Recent experimental results confirm very low energy thresholds of the trigger (below 0.5 MeV/nucleon), ensured within a wide dynamical range. Good characteristics of identification of light charged particles and heavy fragments have been obtained by using three detection techniques: Δ E-E , Δ E -time of flight, and the Pulse-Shape discrimination method. We present results of recent analysis concerning the production of intermediate mass fragments (IMF) in semi-peripheral collisions. Our results combined with theoretical Boltzmann-Nordheim-Vlasov simulations clearly demonstrate the presence of very fast processes of IMF production in the overlapping region of the target and projectile nuclei during re-separation, i.e. in the time scale comparable with the collision time. Evidence for slower, sequential-like production of IMF's is also shown.

Commercial-off-the-shelf devices are often advocated as the only solution to the increasing performance requirements in space applications. This paper presents the solutions developed in the frame of the European Space Agency's HiRel program, concluded in December 2014, where a number of techniques proposed in the past 10 years have been used to design a highly reliable system, which has been selected for forthcoming space missions. This paper presents the system architecture, describes performed evaluations, and discusses the results.

CHIMERA is a second generation 4/spl pi/ detector for high resolution light particle and fragment measurements in the field of intermediate energy nuclear reactions. An enhanced data acquisition, control and trigger system has been developed to manage the almost 5000 electronic channels of the detector. The data acquisition system is based on a Fast Data Link (FDL) connection between 9U VME crates. The FDL is a highly programmable VME device. It performs data readout and transfer to a destination VME CPU, the FIC8243, running the real time OS9 operating system. Data read and transfer is performed by a fast protocol (Sparse Data Scan) whose performances have been improved introducing the Chained Block Transfer mode (CBLT) technique. Data collected by the CPU are broadcast to analysis work-stations for on-line data analysis and storage. All commands from and to the VME CPU are sent by socket-based network protocols. Complete remote control of the electronic front-end is obtained by a system of client-server applications. A first level event selection and control during readout is made by a trigger system based on a new VME 9U board (MUSE), fully integrated with the FDL readout system.

A commercial two-DSP-based board is the basic unit of the on-line computational and control system under development for the multidetector array CHIMERA. The system design includes a small scale parallel and distributed architecture of PCs and DSP boards. The PCs are used both as host computer and interface between user and network. Each PC can host up to three DSP boards. The system is able to accomplish the on-beam control of CHIMERA, by means of the on-line computation of special algorithms, instead of using the usual techniques of special pulses to be sent off-beam. The physical data, collected and organized in UDP packets by the data acquisition system, are read through a 10 Mbit/s Ethernet network. The PC software, running under Windows NT 4.0, is based on threads and assures the communication and program managing as well as the result presentation. The DSP-software is written in C++ and takes care of the communication with the PC and of the computation of algorithms. The preliminary on beam results for the first three wheels (about 100 telescopes), obtained by employing two biprocessor boards located in the PCI bus of a Pentium MMX PC, are also presented.

The paper describes power switching converters suitable for possible power supply distribution networks for the upgraded detectors at the High Luminosity LHC collider. The proposed topologies have been selected by considering their tolerance to the highly hostile environment where the converters will operate as well as their limited electromagnetic noise emission. The analysis focuses on the description of the power supplies for noble liquid calorimeters, such as the Atlas LAr calorimeters, though several outcomes of this research can be applied to other detectors of the future LHC experiments. Experimental results carried on demonstrators are provided.

The paper describes the SIDERALE experiment that was hosted as a piggy back payload on SoRa LDB (Sounding Radar Long Distance Balloon) mission by the Italian Space Agency (ASI). SIDERALE was aimed at testing a detector for high energy astrophysics applications based on a 4x4 pixel CZT solid state sensor. An onboard data handling computer, a mass memory and a power supply units were integrated in SIDERALE. Furthermore an innovative telemetry system BIT (Bi-directional Iridium Telemetry) was used in order for SIDERALE to be autonomous and independent from the hosting payload. In the paper a preliminary analysis of flight and scientific data is discussed.

Recent progress in the CdZnTe (CZT) based detectors prototypes suggests the possibility of an efficient use as 3D detectors. In this paper we discuss how the z coordinate of the interacting photon can be obtained in thick pixellated CZT crystals with a spatial resolution equal to the linear dimension of the implemented pixel (mm). Two different approaches will be described. The first considers a fine segmentation of multi anode and cathode electrodes arranged in orthogonal strips and biased with an electric field transversal to the photons arrival line (PTF = Planar Transversal Field): this solution tends to simplify the readout electronics although at the expense of some complexity in detectors assembling. The second one is based on a more classical configuration, single cathode and multi electrodes anode (exploiting the small pixel effect) biased with a field parallel to the impinging photons direction (PPF = Parallel Transversal Field). This approach needs a more complex electronics to analyze the signal shape of each interaction in order to evaluate, among other parameters, the interaction depth. Conversely in this configuration the focal plane can be assembled with relative simplicity. Both the configurations can be disposed in a stack to improve the working energy range through an effective use of the Compton effect.

In the context of R&D studies financed by the Italian Space Agency (ASI), a feasibility study to evaluate the Italian Industry interest in medium-large scale production of enhanced CZT detectors has been performed by an Italian Consortium. The R&D investment aims at providing in-house source of high quality solid state spectrometers for Space Astrophysics applications. As a possible spin-off industrial applications to Gamma-ray devices for non-destructive inspections in medical, commercial and security fields have been considered by ASI. The short term programme mainly consists of developing proprietary procedures for 2-3" CZT crystals growth, including bonding and contact philosophy, and a newly designed low-power electronics readout chain. The prototype design and breadboarding is based on a fast signal AD conversion with the target in order to perform a new run for an already existing low-power (

The development of formation flying technology in space has opened a new window for astronomy at hard X-γ-ray wavelenghts, allowing observations with unprecedented angular resolution (location accuracy of the order of few arcsec). This has stimulated the development of new concepts for imaging instruments: on one side, the focusing telescopes like γ-ray lens, using small,well shielded detector volumes, on the other side very large area γ-ray imagers, both allowing a big step in sensitivity. We report on a study for the concept of a large area (1 square meter), narrow field coded mask telescope with arcsec imaging capability, based on CZT detector technology and active collimation system, made of Si microstrip detector modules and operating in the energy band 15-500 keV. Feasibility and performance characteristics are discussed as well as possible geometric configurations and background suppression schemes, in the light of data obtained from INTEGRAL/IBIS and other CdTe/CZT instruments currently in space.

The capability of digital pulse shape technique to acquire data from CHIMERA detection cells (Si-CsI(Tl) telescopes) has been evidenced in our previous works. We have now applied this technique to the charge discrimination of the products stopped in the silicon detectors. Large area totally depleted CHIMERA planar silicon detectors (5 cmtimes5 cm area, 300 mum thick) in both rear and front side injection have been used. In preliminary tests full charge identification for the reaction products up to Z=11 have been obtained for products both crossing (DeltaE-E technique) and stopping in the silicon detector, using a 21 MeV/u 20Ne beam at the LNS Superconducting Cyclotron in Catania. The quality of the obtained results clearly indicates that the digital signal processing approach is able to give excellent results in this application, too

Mass and atomic-number identification (ID) of reaction products is a fundamental requirement of any nuclear reaction study. An effective particle-ID method is demonstrated, based on pulse shape analysis/discrimination (PSD) applied to large-area, single-element silicon detectors. This technique uses commercial electronic modules and achieves atomic number resolution rivaling that typically obtained with multi-element (/spl Delta/E-E) detector telescopes. The method is applied to the CHIMERA detector system without compromising its time-of-flight (TOF) resolution. In-beam tests of the PSD method have been performed with large-area, 300-/spl mu/m thick CHIMERA silicon detectors, measuring particles from the /sup 19/F+/sup 12/C reaction at Tandem energies. Performance of a simple PSD set up is discussed, for front and rear particle injection.

A fault injection tool for SRAM-based FPGAs based on the fault emulation technique is presented. Faults are injected by modifying the configuration bitstream while this is loaded into the device, without using standard synthesis tools or available commercial software, such as Jbits or similar. This makes our tool independent of the system used for design development and allows a quick fault injection. Also, any device configuration cell can be accessed and this permits to study the effects of possible contentions or shorts, which cannot be analyzed using commercial tools. An example of the use of the tool is described.

Heavy ion studies with stable and exotic beams require the identification of nuclear frag- ments in a broad range of mass and atomic numbers. Recent progresses of the Pulse Shape Discrimination (PSD) method applied to the current signals of silicon detectors have en- couraged new studies in this field. The aim of our experimental study was to progress in this technique by applying PSD to charge signals produced in planar silicon detectors of large capacitance (1nF). A new electronic design based on a double constant-fraction discrimination of timing signals, was applied to some of the CHIMERA Si detectors, by using Tandem and Cyclotron beams delivered by the LNS in Catania. We obtained charge identification with energy threshold of about 4 AMeV from Z=1 up to fluorine and with good timing performances (direct injection mode). Our recent results strongly encourage for further application to 4π detection systems in the field of exotic beams.

124Sn+64Ni and 112Sn+58Ni reactions at 35 AMeV incident energy were studied with the forward part of CHIMERA multi-detector. The most central collisions were selected by means of a multidimensional analysis. The characteristics of the source formed in the central collisions, as size, temperature and volume, were inspected. The measured isotopes of light fragments (3, 4 pages, Contribution to 8th International Conference on Nucleus-Nucleus Collisions, Moscow 2003