Search

The impacts of hydrided and non-hydrided materials near transistors on neutron-induced single event upsets (SEUs) were investigated by simulating monoenergetic neutron irradiations on 65-nm technology bulk static random access memories. The onset energy of the SEUs induced by H ions depends on the shielding capability, i.e., the material and thickness, of components placed in front of transistors when those components do not contain hydrogen atoms. The shielding capability also influences the initial slope observed in the energy-dependence of SEU cross sections. Taking into account the non-hydrided component attached to memory cells used in the simulation, all experimental data measured at each neutron facility were reproduced well using SEU cross sections obtained by simulation. We also find that the effect of components near transistors on neutron-induced soft error rates is not negligible even for irradiation by white neutrons.

As a first step in building a toolkit for the computer analysis of images of sea floor sediment cores, we introduce a technique to automate a time consuming manual phase of said analysis. The retrieved cores contain artifacts, e.g., induced by the extraction itself, the removal of which improves the efficiency of environmental reconstruction. From a computer vision perspective, the task of identifying those artifacts is an image segmentation problem. The method we describe as a solution uses the recently introduced fully convolutional neural networks (FCN), which have been shown to be very efficient in segmenting images.

With the aim of providing critical nuclear data of primary knock-on atoms (PKAs) created from proton-induced spallation reactions, a new detection system was designed and dedicated to the PKA measurement that requires lower measurement threshold energies and superior mass resolution than the conventional experimental setups. Such requirements can be fulfilled by employing the TOF-E and dE-E methods, and this new PKA detection system, which consists of two fast timing detectors and one dE-E gas ionization detector. The design of the detectors and the experimental setup, along with the estimated system performed are briefly described in this paper.

Transports of secondary cosmic-ray neutrons and muons in a building and a stacked server are simulated by Particle and Heavy Ion Transport code System (PHITS) with considering distributions of energy and zenith-angle of secondary cosmic-rays by PHITS based analytical radiation model in the atmosphere (PARMA) model. The calculated neutron fluxes are in surprisingly good agreement with measured data. Soft errors in an n-type metal-oxide-semiconductor field-effect transistor caused by secondary cosmic-ray neutron and muon in the open air and on the first floor of the building are analyzed based on the multiple sensitive volume (MSV) model using PHITS. It is found that the secondary cosmic-ray neutron-induced SER decrease by shielding effect of the building while that caused by secondary cosmic-ray muons is not affected.

Precise predictions of the radiation environment inside space vehicles, and inside the human body, are essential when planning for long term deep space missions. Since these predictions include complex geometries, as well as the contributions from many different types of radiation, including neutrons, 3-D Monte Carlo codes with precise physics models are needed. In this paper, we present improvements and developments of some physics models used in the general purpose 3-D Monte Carlo code PHITS [1]. The total reaction cross section (σ R ) and the decay lifetime of a projectile particle are the first essential quantities in MC calculations, since these determine the mean free path of the transported particles and the probability function according to which a projectile particle will collide within a certain distance in the matter depends on the σ R . This will also scale the calculated partial fragmentation cross sections. In this paper we present comparisons of calculated and measured σ R using the Kurotama Hybrid σ R , model [2] which is incorporated into PHITS. The prediction of the fragmentation reactions of relativistic heavy ions is also essential for ensuring radiation safety of astronauts. The default model for nuclear-nuclear reactions is JQMD in PHITS. However, JQMD cannot accurately enough describe the nucleon and d, t, 3He and 4He induced reactions. Therefore the Intra-Nuclear Cascade of Liege (INCL) [3] has been selected as the default model for these reactions. Moreover, it has been realized that the production of light fragments is underestimated by conventional simulation codes based on a combination of intranuclear cascade and statistical decay models. This is because this combination cannot reproduce the high multiplicity events that are responsible for the production of light fragments. To better reproduce high multiplicity events, we have simulated fragmentation cross sections using a combination of JQMD/INCL, statistical multi-fragmentation model (SMM) [4,5] and the generalized evaporation model (GEM). Examples of these simulations will be presented. A new approach to describe neutron spectra of deuteron-induced reactions in the Monte Carlo simulations has also been developed by combining the INCL and the Distorted Wave Born Approximation (DWBA) calculation [6]. We have incorporated this combined method into PHITS and applied it to estimate (d,xn) spectra on light targets at incident energies ranging from 10 to 40 MeV. In this paper, we will show that the double differential cross sections obtained by INCL and DWBA successfully reproduced broad peaks and discrete peaks, respectively.

A semi-empirical model is derived from operational data collected aboard the International Space Station (ISS) with the U.S. tissue equivalent proportional counter (TEPC). The model provides daily and cumulative mission predictions of the operational dose equivalent that space-crew may receive from galactic cosmic radiation (GCR) and trapped radiation (TR) sources as a function of the ISS orbit. The parametric model for GCR exposure correlates the TEPC dose equivalent rate to the cutoff rigidity at ISS altitudes while the TR parametric model relates this quantity to the mean atmospheric density at the crossing of the South Atlantic Anomaly (SAA). The influences of solar activity, flux asymmetry inside the SAA, detector orientation, and position aboard the ISS on the dose equivalent have been examined. The model has been successfully benchmarked against measured data for GCR and TR exposures to within ±10% and ±20%, respectively, over periods of time ranging from a single day to a full mission. In addition, preliminary estimates of the protection quantity of effective dose equivalent have been simulated using the PHITS Monte Carlo transport code. These simulations indicate that the TEPC dose equivalent is a conservative estimate of the effective dose equivalent.

Concerns about the biological effects of space radiation are increasing rapidly due to the perspective of long-duration manned missions, both in relation to the International Space Station (ISS) and to manned interplanetary missions to Mars in the future. As a preparation for these long duration space missions it is important to ensure an excellent capability to evaluate the impact of space radiation on human health in order to secure the safety of the astronauts/cosmonauts and minimize their risks. It is therefore necessary to measure the radiation load on the personnel both inside and outside the space vehicles and to certify that organ and tissue equivalent doses can be simulated as accurate as possible. In this paper we will present simulations using the three-dimensional Monte Carlo Particle and Heavy Ion Transport code System (PHITS) of long term dose measurements performed with the ESA supported experiment MATROSHKA (MTR), which is an anthropomorphic phantom containing over 6000 radiation detectors, mimicking a human head and torso. The MTR experiment, led by the German Aerospace Center (DLR), was launched in January 2004 and has measured the absorbed dose from space radiation both inside and outside the ISS. In this paper comparisons of measured and calculated dose and organ doses in the MTR located outside the ISS will be presented and uncertainties of the simulations will be discussed. This project was funded by the European Commission in the frame of the FP7 HAMLET project (Project # 218817).12

To be able to calculate the nucleon-nucleon and nucleon-nucleus total reaction cross sections with precision is very important for studies of basic nuclear properties, e.g. nuclear structure. This is also of importance for particle and heavy ion transport calculations since in all particle and heavy ion transport codes, the probability function that a projectile particle will collide within a certain distance x in the matter depends on the total reaction cross sections. This will also scale the calculated partial fragmentation cross sections. It is therefore crucial that accurate total reaction cross section models are used in the transport calculations. In this paper, different models for calculating nucleon-nucleus and nucleus-nucleus total reaction cross sections are compared.1,2

In order to investigate the relationship between kinetic energy of charged particles and light output of liquid organic scintillator, response functions for proton, deuteron, triton, /sup 3/He nucleus and alpha particle have been measured at heavy-ion medical accelerator in Chiba (HIMAC) of National Institute of Radiological Sciences (NIRS). The charged particles were generated by 400 MeV/u C ion bombardment with a thick graphite target. Kinetic energies were determined by time-of-flight (TOF) technique. Energy loss during their flight was calculated by PHITS code and taken into account at energy-correction. Light output for proton was also measured using mono-energy proton beam of 100 and 160 MeV supplied by accelerator. Kinetic energy of proton beam was changed by inserting Al plates onto beam axis as an energy absorber. The experimental results gave a new database of light output.