N. H. Medina

STRUCTURE OF NEUTRON–RICH NUCLEI FROM DEEP–INELASTIC REACTIONS

Neutron rich nuclei have been populated using the 82Se+192Os deep-inelastic reaction. New experimental results on 188W, 188,190Os target-like nuclei, as well as 74,76,78Ge beam-like nuclei are presented.

Evolution from spherical to various deformed shapes in the odd-odd 59136Pr77 nucleus

Abstract The level scheme of the doubly odd 136Pr nucleus has been investigated via the 136Ce(p,n), 122Sn(19F,5n) and 110Pd(30Si,p3n) reactions at beam energies of 14, 84 and 125 MeV, respectively. A complex decay scheme has been established for the 90 ns isomeric level with Ex = 594.7 keV and Jπ = 6+. The two previously reported bands, one based on the πh 11 2 ⊗ νh 11 2 configuration and one with suggested negative parity consisting of only dipole transitions, have been extended at higher spins and connected firmly to the 6+ isomer. Six new bands have been also identified: two consist of strong dipole and crossover quadrupole transitions, whereas the other four, very weakly populated, consist of only quadrupole transitions. The observed level structures are compared to theoretical calculations performed within the interacting boson model for odd-odd nuclei (IBFFM) and the cranked shell model. The experimental B (M1) B (E2) ratios of the yrast band are well reproduced by the IBFFM calculations, while those of the other semi-decoupled structures are in good agreement with the values obtained from the semiclassical model of Donau.

Proton excitations across the Z = 64 gap in the doubly magic superdeformed nucleus 144Gd

Five superdeformed (SD) bands have been identified in 144Gd with the GASP array using the reaction 100Mo + 48Ti. The J(2) moments of inertia of the four excited SD bands are flat as a function of rotational frequency, indicating the blocking of the N = 6 proton crossing observed in the yrast SD band. According to cranked shell model calculations, the excited bands have two-quasiproton configurations with one proton in the N = 6 orbital and the other in each signature partner of the [404]92+ or [411]32+ orbitals, lying above the Z = 64 gap. The interpretation of the excited SD bands in terms of proton excitations points to the high stability of the N = 80 shell closure at SD shapes. The population of the yrast SD band as a function of the beam energy has been also investigated. Our data shows that the intensity of the yrast SD band is not configuration dependent, being comparable to that of yrast SD bands in the neighboring nuclei. By comparing experimental and theoretical alignments, spins and configurations are assigned to all observed SD bands in the A = 140–150 region.

Stopping power of Nd ions in Pb determined from γ-ray lineshape analysis in Coulomb excitation

Abstract The stopping power of Nd ions in Pb, in the range from 7 to 35 MeV, has been determined using the γ-ray lineshape analysis of the 696.6 keV transition de-exciting the first 2+ level in 144Nd, populated by Coulomb excitation using a 90 MeV 28Si beam. The data are compared with the most commonly used parameterizations.

Analyzing Reliability and Performance Trade-Offs of HLS-Based Designs in SRAM-Based FPGAs Under Soft Errors

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.

Analysis of SRAM-Based FPGA SEU Sensitivity to Combined EMI and TID-Imprinted Effects

This work proposes a novel methodology to evaluate SRAM-based FPGAs susceptibility with respect to Single-Event Upset (SEU) as a function of noise on VDD power pins, TotalIonizing Dose (TID) and TID-imprinted effect on BlockRAM cells. The proposed procedure is demonstrated for SEU measurements on a Xilinx Spartan 3E FPGA operating in an 8 MV Pelletron accelerator for the SEU test with heavy-ions, whereas TID was deposited by means of a Shimadzu XRD-7000 X-ray diffractometer. In order to observe the TID-induced imprint effect inside the BlockRAM cells, a second SEU test with neutrons was performed with Americium/Beryllium (241AmBe). The noise was injected into the power supply bus according to the IEC 61.000-4-29 standard and consisted of voltage dips with 16.67% and 25% of the FPGAs VDD at frequencies of 10 Hz and 5 kHz, respectively. At the end of the experiment, the combined SEU failure rate, given in error/bit.day, is calculated for the FPGAs BlockRAM cells. The combined failure rate is defined as the average SEU failure rate computed before and after exposition of the FPGA to the TID.

Heavy Ions Induced Single Event Upsets Testing of the 28 nm Xilinx Zynq-7000 All Programmable SoC

The recent advance of silicon technology has allowed the integration of complex systems in a single chip. Nowadays, Field Programmable Gate Array (FPGA) devices are composed not only of the programmable fabric but also by hard-core processors, dedicated processing block interfaces to various peripherals, on-chip bus structures and analog blocks. Among the latest released devices of this type, this work focuses in the 28 nm Xilinx Zynq-7000 All Programmable SoC (APSoC). While not immune to the radiation environment in space, the Zynq-7000 seems to be very attractive for the aerospace sector due to its high computational power capability and low-power consumption. In this work, results from heavy ions testing for Zynq-7000 are presented. The experiments were performed in a Brazilian facility located at the University of São Paulo, Brazil.

Shape change along the highly-deformed band in 137Nd☆

Abstract Lifetimes of states of the highly-deformed (HD) band in 137Nd have been measured using the Doppler shift attenuation method. A line-shape analysis has been carried out for individual states, resulting in transition quadrupole moments which decrease with increasing spin. This represents the first confirmation of previous total routhian surface (TRS) calculations that predicted a drift towards positive γ values of the HD minimum (at essentially constant β deformation). The lifetime data show a rather modest deformation of the HD band structure, indicating a softening of the nuclear potential at HD shape.

Study of proton radiation effects among diamond and rectangular gate MOSFET layouts

This paper describes an experimental comparative study of proton ionizing radiation effects between the metal-oxide-semiconductor (MOS) Field Effect Transistors (MOSFETs) implemented with hexagonal gate shapes (diamond) and their respective counterparts designed with the classical rectangular ones, regarding the same gate areas, channel widths and geometrical ratios (W/L). The devices were manufactured by using the 350 nm bulk complementary MOS (CMOS) integrated circuits technology. The diamond MOSFET with α angles higher or equal to 90° tends to present a smaller vulnerability to the high doses ionizing radiation than those observed in the typical rectangular MOSFET counterparts.

Reliability on ARM Processors Against Soft Errors Through SIHFT Techniques

ARM processors are leaders in embedded systems, delivering high-performance computing, power efficiency, and reduced cost. For this reason, there is a relevant interest for its use in the aerospace industry. However, the use of sub-micron technologies has increased the sensitivity to radiation-induced transient faults. Thus, the mitigation of soft errors has become a major concern. Software-Implemented Hardware Fault Tolerance (SIHFT) techniques are a low-cost way to protect processors against soft errors. On the other hand, they cause high overheads in the execution time and memory, which consequently increase the energy consumption. In this work, we implement a set of software techniques based on different redundancy and checking rules. Furthermore, a low-overhead technique to protect the program execution flow is included. Tests are performed using the ARM Cortex-A9 processor. Simulated fault injection campaigns and radiation test with heavy ions have been performed. Results evaluate the trade-offs among fault detection, execution time, and memory footprint. They show significant improvements of the overheads when compared to previously reported techniques.