Departamento de Física

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A commercial off-the-shelf pMOS transistor as X-ray and heavy ion detector
(2015) Silveira M.A.G.; Melo M.A.A.; Aguiar V.A.P.; Rallo A.; Santos R.B.B.; Medina N.H.; Added N.; Seixas L.E.; Leite F.G.; Cunha F.G.; Cirne K.H.; Giacomini R.; de OLIVEIRA J.A.
© Published under licence by IOP Publishing Ltd.Recently, p-channel metal-oxide-semiconductor (pMOS) transistors were suggested as fit for the task of detecting and quantifying ionizing radiation dose. Linearity, small detection volume, fast readout, portability, low power consumption and low radiation attenuation are some of the pMOS advantages over PIN diode and thermoluminiscent dosimeters. A hand-held measurement system using a low power commercial off-the-shelf pMOSas the sensor would have a clear advantage due to the lower cost incurred by a standard technological process. In this research work, we tested the commercial device 3N163 regarding its behaviouras an X-ray sensor, as well as its possible application as a heavy-ion detector. To study the radiation effects of X-rays, a XRD-7000 (Shimadzu) X-ray diffraction setup was used to produce 10-keV effective energy photons. Heavy ions tests involved 12C, 16O, 19F, 28Si, 35Cl, 63Cu and 107Ag beams scattered at 15° by a 275 μg/cm2 gold target, which provide LETs (Linear Energy Transfer) from 4 to 40 MeV/mg/cm2. The signal readout was done using a 1 GHz oscilloscope with a 10-Gsamples/s conversion rate, high enough to permit the recording of transient pulses in the drain current. In this case, an ion can cause a current signal proportional to the ion beam used. Through this study it was found that a simple commercial pMOS device can be reliably used as a detector of X-rays as well as heavy ion detector.
Analyzing Reliability and Performance Trade-Offs of HLS-Based Designs in SRAM-Based FPGAs under Soft Errors
(2017) Tambara L.A.; Tonfat J.; Santos A.; Kastensmidt F.L.; Medina N.H.; Added N.; Aguiar V.A.P.; Aguirre F.; Silveira M.A.G.
© 1963-2012 IEEE.The increasing system complexity of FPGA-based hardware designs and shortening of time-to-market have motivated the adoption of new designing methodologies focused on addressing the current need for high-performance circuits. High-Level Synthesis (HLS) tools can generate Register Transfer Level (RTL) designs from high-level software programming languages. These tools have evolved significantly in recent years, providing optimized RTL designs, which can serve the needs of safety-critical applications that require both high performance and high reliability levels. However, a reliability evaluation of HLS-based designs under soft errors has not yet been presented. In this work, the trade-offs of different HLS-based designs in terms of reliability, resource utilization, and performance are investigated by analyzing their behavior under soft errors and comparing them to a standard processor-based implementation in an SRAM-based FPGA. Results obtained from fault injection campaigns and radiation experiments show that it is possible to increase the performance of a processor-based system up to 5,000 times by changing its architecture with a small impact in the cross section (increasing up to 8 times), and still increasing the Mean Workload Between Failures (MWBF) of the system.
Analyzing the Influence of the Angles of Incidence and Rotation on MBU Events Induced by Low LET Heavy Ions in a 28-nm SRAM-Based FPGA
(2017) Tonfat J.; Kastensmidt F.L.; Artola L.; Hubert G.; Medina N.H.; Added N.; Aguiar V.A.P.; Aguirre F.; Macchione E.L.A.; Silveira M.A.G.
© 1963-2012 IEEE.This paper shows the impact of low linear energy transfer heavy ions on the reliability of 28-nm Bulk static random access memory (RAM) cells from Artix-7 field-programmable gate array. Irradiation tests on the ground showed significant differences in the multiple bit upset cross section of configuration RAM and block RAM memory cells under various angles of incidence and rotation of the device. Experimental data are analyzed at transistor level by using the single-event effect prediction tool called multiscale single-event phenomenon prediction platform coupled with SPICE simulations.
Experimental setup for Single Event Effects at the São Paulo 8UD Pelletron Accelerator
(2014) Aguiar V.A.P.; Added N.; Medina N.H.; Macchione E.L.A.; Tabacniks M.H.; Aguirre F.R.; Silveira M.A.G.; Santos R.B.B.; Seixas Jr. L.E.
In this work we present an experimental setup mounted in one of the beam lines at the São Paulo 8UD Pelletron Accelerator in order to study Single Event Effects in electronic devices. The basic idea is to use elastic scattering collisions to achieve a low-flux with a high-uniformity ion beam to irradiate several devices. 12C, 16O, 28Si, 35Cl and 63Cu beams were used to test the experimental setup. In this system it is possible to use efficiently LET values of 17 MeV/mg/cm2 for an external beam arrangement and up to 32 MeV/mg/cm2 for in-vacuum irradiation. © 2014 Elsevier B.V. All rights reserved.
High natural radiation in Brazilian sands
(2012) Silveira M.A.G.; Medina N.H.; Pereira B.R.; Aguiar V.A.P.
The present work investigated Brazilian beach sands in order to analyze the total external natural radiation dose using a gamma-ray spectrometry technique. The activities from the radionuclides 40K and the elements from the series of 238U and 232Th were measured. The sand samples from Morro Branco beach, Ceará, and Itacaré beach, Bahia, presented different colors and grain size than the beaches from São Paulo. A sample collected in Itacaré beach showed an effective dose of 2.5 (1) mSv/yr. This value is outside the annual typical range (0.3-0.6 mSv) indicated by the United Nations Scientific Committee on the Effects of Atomic Radiation. The high effective dose found in Itacaré beach is mainly due to the presence of a large amount of 232Th and 238U. All the other samples collected in Ceará and São Paulo States are inside the annual typical range. Energy-Dispersive X-Ray Spectroscopy (EDS) microanalysis showed that this high external radiation is related to the presence of zircon and monazite, which commonly carry traces of uranium and thorium. © 2012 American Institute of Physics.
Reliability calculation with respect to functional failures induced by radiation in TMR arm cortex-M0 soft-core embedded into SRAM-based FPGA
(2019) Benites L.A.C.; Benevenuti F.; De Oliveira A.B.; Kastensmidt F.L.; Added N.; Aguiar V.A.P.; Medina N.H.; Guazzelli M.A.
© 2019 IEEE.This paper presents comparative results from fault injection (FI) and heavy ions accelerated irradiation on a Xilinx 7 series static RAM (SRAM)-based field-programmable gate array (FPGA) for a soft-core microprocessor mitigated by triple modular redundancy (TMR) with different levels of granularity. The Arm Cortex-M0 soft-core processor executing two software applications is employed as a case study. The TMR implementation is automatically generated from synthesized netlist and includes coarse and fine grain variants. Apart from the TMR mitigation, the configuration memory scrubbing is used as implemented by the engine natively available on Xilinx 7 series FPGAs. Experiments with FI and heavy ions allow analyzing the effectiveness of the automated TMR mitigation combined with memory scrubbing and also to analyze the consistency of reliability metrics from FI and heavy ions. The dynamic cross section of the design was improved up to 4.5 times according to the implemented TMR granularity and when associated with the configuration memory scrubbing.
Reliability-Performance Analysis of Hardware and Software Co-Designs in SRAM-Based APSoCs
(2018) Tambara L.A.; Kastensmidt F.L.; Rech P.; Lins F.; Medina N.H.; Added N.; Aguiar V.A.P.; Silveira M.A.G.
© 1963-2012 IEEE.All programmable system-on-chip (APSoC) devices provide higher system performance and programmable flexibility at lower costs compared to standalone field-programmable gate array devices and processors. Unfortunately, it has been demonstrated that the high complexity and density of APSoCs increase the system's susceptibility to radiation-induced errors. This paper investigates the effects of soft errors on APSoCs at design level through reliability and performance analyses. We explore 28 different hardware and software co-designs varying the workload distribution between hardware and software. We also propose a reliability analysis flow based on fault injection (FI) to estimate the reliability trend of hardware-only and software-only designs and hardware-software co-designs. Results obtained from both radiation experiments and FI campaigns reveal that performance and reliability can be improved up to 117× by offloading the workload of an APSoC-based system to its programmable logic core. We also show that the proposed flow is a precise method to estimate the reliability trend of system designs on APSoCs before radiation experiments.

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