GPU water cooling investigations for the digital correlator of the MeerKAT+

GPUs represent a valuable solution in the framework of digital signal processing in radio astronomy. Currently, GPUs have been selected as the primary option for building the digital correlator of the MeerKAT+ array, for both the F-Engine and the X/B-Engine. Thermal management is one of the major issues affecting GPUs in comparison to FPGAs and in this paper we outline how water cooling solutions may assist

Sardinia aperture array demonstrator: measurement campaigns of radio frequency interferences

Measurement campaigns of radio frequency interferences (RFIs) represent a fundamental aspect to optimize data collected by radio astronomical observations. In order to monitor the state of unwanted man-made signals, every radio telescope needs to have a radio frequency map in the frequencies range of its receivers. The Sardinia Aperture Array Demonstrator (SAD) is an Italian aperture array demonstrator composed of prototypical Vivaldi antennas designed to work at frequencies below 500 MHz. The antennas are located at the Sardinia Radio Telescope (SRT) site and they are arranged with a versatile approach that is able to provide different array configurations. In this paper, we present the results of measurement campaigns conducted with the SAD antennas at the SRT observing site with the aim to monitor the evolution of RFI scenario from 2016 to date. The signal acquisition chain and the software tool used for RFI detection are, also, presented

A New Biometric Tool for Three-Dimensional Subcutaneous Tumor Scanning in Mice

To propose an innovative methodology for the monitoring of the evolution of induced subcutaneous tumors in mice. Materials and Methods: A new 3D scannerable to measure the tumor mass volume is presented. The scanner is based on the projection of a fringe pattern onto the sample surface (structured light). The lines are diffused by the sample and then collected by a digital camera. The obtained 2D-image is treated by the scanner’s software thatextracts the 3D information and evaluates the samplevolume. Results: The 3D scanner has been successfully used in the measurement of subcutaneous HT-29 colorectal cancer xenografts treated with 5-fluorouracil, bevacizumab and their combination. Comparison with simple caliper measurements revealed important and significant differences between the two measurement techniques. Conclusion: The proposedmethodology is more effective than the usual approach basedon caliper measurements.The efficacy of a new anticancer drug should be alwaysverified by means of the so-called experimental model of the disease, where the characteristics of the disease are recreated in cell cultures, grown in the laboratory (in vitromodels) orin laboratory animals (in vivo models) (1). Considering the latter case, tumors may be induced in mice by subcutaneous injection of human tumor cells. Subcutaneous human tumor xenograft models are widely used because they recapitulate many aspects of the biology of human tumors, including sensitivity to anticancer agents (2). Once cancer cells areinoculated, the researchers carry out treatment with the anticancer drug and follow the daily evolutions in the shape and in volume of the tumor. The tumor mass volume of treated and non-treated mice must be statistically compared in order to assess the reliability of the treatment. The testin gof human tumors in subcutaneous sites have provided relevant and predictive information to the clinic. In fact,every clinically-approved anticancer drug was tested usingthis model, and showed significant antitumor effects beforeentering early-phase clinical trials (2).Although some experimental devices are available for the measurement of tumor volume from 3-dimensional images(computed axial tomography, positron-emission tomography,and magnetic resonance imaging), these systems are primarily designed for biological, chemical, and functionalstudies of animal models (3). As well-stated by Girit and colleagues, these devices usually require many preparative efforts and expensive materials (radioactive sources, contrastagents, and fluorescent chemicals), thus their use is notpractical for animal testing facilities (4).On the basis of these considerations, in partnership withPOEMA (Progettazioni Opto-Elettroniche MetrologiaAvanzata; Cagliari, Italy; www.poemaonline.eu), we developed an innovative small non-contact device (3Dscanner) capable of rapid, highly reproducible measurements of subcutaneous tumor volumes in mice. We outline the prototype characteristics, describing hardware and software features, and give some practical examples of its use

Progettazione, realizzazione e caratterizzazione della catena ricevente per il sistema SADino precursore del Sardinia Aperture Array Demonstrator (SAAD)

Il presente rapporto tecnico riassume la progettazione, realizzazione e caratterizzazione della catena di componenti a microonde e a radio frequenza per l’acquisizione del segnale del sistema SADino, precursore del Sardinia Aperture Array Demonstrator (SAAD). Il progetto SAAD prevede la realizzazione di un aperture array composto da 128 antenne Vivaldi a doppia polarizzazione lineare [1-7], installate al sito del Sardinia Radio Telescope (SRT), ciascuna delle quali verrà collegata alla sua catena dedicata di componenti a microonde per l’acquisizione del segnale, che permette di trasportare il segnale analogico rilevato in radio frequenza dall’antenna fino al back-end digitale. Con l’obiettivo di eseguire velocemente i primi test, inizialmente si è deciso di implementare parzialmente l’array SAAD. L’implementazione parziale del sistema SAAD prende appunto il nome di SADino, che prevede la realizzazione di un mini-array di 16 elementi a doppia polarizzazione, con il quale è possibile effettuare le prime osservazioni e i primi test di beam-forming con il back-end digitale dedicato basato sulle schede Italian Tile Processing Module (iTPM) [8]. Con SADino sono state scelte solo 16 antenne (a doppia polarizzazione) dell’intero array SAAD da 128 elementi, disposte in maniera casuale, poiché il back-end digitale iTPM è dotato di soli 32 ingressi. La catena ricevente (una per ogni canale di polarizzazione di ciascuna antenna Vivaldi) è stata progettata basandosi sui risultati di una campagna di misure, effettuata nell’estate del 2020, utile a valutare la presenza in banda di segnali interferenti generati dall’uomo e indesiderati per le attività di ricerca radioastronomica, noti come radio frequency interference (RFI) [6]. Per l’esecuzione di tale campagna di misure, si è utilizzata una delle antenne Vivaldi del SAAD, equipaggiandola con una catena di acquisizione del segnale che ha fatto da precursore (almeno per quanto riguarda la valutazione degli stadi di amplificazione) alla versione finale di catena ricevente da utilizzare sul sistema SADino, precursore dell’intero SAAD. L’obiettivo di questa campagna di misure RFI è stato quello di selezionare una banda di frequenze il più possibile libera da segnali indesiderati e contenuta ovviamente all’interno della banda di lavoro delle antenne che costituiscono l’array. Le antenne Vivaldi del SAAD sono state progettate per lavorare con buona efficienza in un range di frequenze che va da 50 MHz a 500 MHz [4], mentre i componenti a microonde che costituiscono la catena di acquisizione del segnale sono ottimizzati per lavorare nel range di frequenze selezionato in base ai risultati delle misure RFI e all’interno del quale poi opererà il telescopio. In questo rapporto interno vengono presentati i risultati della campagna di misure RFI preliminare, illustrando la catena ricevente utilizzata per queste misure (vedi Sezione 2). Nella Sezione 3 viene descritta la progettazione, realizzazione e caratterizzazione della catena di componenti a microonde per ciascuna antenna del sistema SADino. Nella Sezione 4 viene descritto il sistema di alimentazione che permette di alimentare i componenti attivi inseriti all’interno della catena ricevente e, infine, nella Sezione 5 si riportano le considerazioni conclusive sul lavoro svolto

Preliminary tests to design an ad hoc signal acquisition chain for the Sardinia Aperture Array Demonstrator

The Sardinia Aperture Array Demonstrator (SAD) is an Italian facility, which is composed of 128 prototypical Vivaldi antennas, specifically designed to operate across the 50-500 MHz frequency range. As well known, one of the major burden at low frequency are the radio frequency interferences, thus after several accurate measurement campaigns we realized that a specific signal conditioning is needed in order to feed the digital beamformer with the proper signal level. In this paper, we report the results of the preliminary tests that we carried out in order to design an ad hoc receiving chain for the SAD array

FPGA-based digital back-ends for the Sardinia Radio Telescope

The Sardinia Radio Telescope (SRT), located in San Basilio, about 35 km north of Cagliari, is the largest (64-m diameter) radio telescope in Italy. It is a general-purpose, fully-steerable radio telescope designed to operate in the 300 MHz - 116 GHz frequency range, which allows it to perform a wide variety of scientific studies. The advanced electronic digital platforms that are installed at SRT play a key role, in particular those based on FPGAs (Field Programmable Gate Array), both because of their processing capability and their reconfigurability. In this paper, we present an overview of the digital back-ends available at SRT, as well as the ones under development; it is important to underline that, for all of them, FPGAs are the beating heart

Spectro-polarimetric observations of the CIZA J2242.8+5301 northern radio relic: no evidence of high-frequency steepening

Observations of radio relics at very high frequency (>10 GHz) can help to understand how particles age and are (re-)accelerated in galaxy cluster outskirts and how magnetic fields are amplified in these environments. In this work, we present new single-dish 18.6 GHz Sardinia Radio Telescope and 14.25 GHz Effelsberg observations of the well known northern radio relic of CIZA J2242.8+5301. We detected the relic which shows a length of $\sim$1.8 Mpc and a flux density equal to $\rm S_{14.25\,GHz}=(9.5\pm3.9)\,mJy$ and $\rm S_{18.6\,GHz}=(7.67\pm0.90)\,mJy$ at 14.25 GHz and 18.6 GHz respectively. The resulting best-fit model of the relic spectrum from 145 MHz to 18.6 GHz is a power-law spectrum with spectral index $\alpha=1.12\pm0.03$: no evidence of steepening has been found in the new data presented in this work. For the first time, polarisation properties have been derived at 18.6 GHz, revealing an averaged polarisation fraction of $\sim40\%$ and a magnetic field aligned with the 'filaments' or 'sheets' of the relic.Comment: 10 pages, 8 figure

Preliminary Characterization of the Digitally Formed Beams of PHAROS2 Phased Array Feed

We describe the beamforming strategy and the preliminary laboratory characterization results of the beam pattern synthesized by the PHAROS2 Phased Array Feed (PAF), a 4-8 GHz PAF with digital beamformer for radio astronomy application. The PAF is based on an array of 10×11 dual-polarization Vivaldi antennas cryogenically cooled at 20 K along with low noise amplification modules (LNAs) cascaded with a multi-channel Warm Section (WS) receiver. We present the beamforming and test procedures used to, respectively digitally synthesize and characterize the PHAROS2 antenna array beam pattern at 6 GHz. The tests of the array were carried out at room temperature by directly connecting 24 antenna elements to the WS and iTPM digital beamformer in a laboratory measurement setup

Observations of supernova remnants with the Sardinia Radio Telescope

In the frame of the Astronomical Validation activities for the 64m Sardinia Radio Telescope, we performed 5-22 GHz imaging observations of the complex-morphology supernova remnants (SNRs) W44 and IC443. We adopted innovative observing and mapping techniques providing unprecedented accuracy for single-dish imaging of SNRs at these frequencies, revealing morphological details typically available only at lower frequencies through interferometry observations. High-frequency studies of SNRs in the radio range are useful to better characterize the spatially-resolved spectra and the physical parameters of different regions of the SNRs interacting with the ISM. Furthermore, synchrotron-emitting electrons in the high-frequency radio band are also responsible for the observed high-energy phenomenology as -e.g.- Inverse Compton and bremsstrahlung emission components observed in gamma-rays, to be disentangled from hadron emission contribution (providing constraints on the origin of cosmic rays)

A real-time FFT-KLT implementation for SETI research at the Sardinia Radio Telescope

The Search for ExtraTerrestrial Intelligence (SETI) is a project whose goal is to find possible life signatures emitted (intentionally or unintentionally) by possible civilizations from other habitable planets. Historically, the narrow-band FFT approach has been used, since a quasi-monochromatic signal is the most probable signal one would use to send a message to another world, that is in the case of intentionally- transmitted signals. Nevertheless, we could receive an unintentionally-transmitted signal as well. In that case, it would most certainly not be a quasi-monochromatic signal, but would probably be similar (with a wider bandwidth, of the order of MHz) to the signals that we use for conventional communications on Earth. The Kahrunen-Loève Transform (KLT) is a powerful algorithm for such a kind of research. However, a real-time implementation of the KLT has thus far not worked due to a lack of technological resources. We describe a hardware-software infrastructure at the Sardinia Radio Telescope (SRT) that, in real-time, makes it possible to perform the KLT in parallel to the FFT