Natural Space Radiation Research Articles

Monte Carlo simulations of proton irradiation effects on PTFE, KEVLAR, EFTE, DYNEEMA, and NOMEX polymeric materials used in astronaut space suits

Astronauts suffer from natural space radiation as high-energetic protons, heavy ions, and secondary particles produced in collisions. Galactic cosmic rays and solar particle events are the basic parts of space radiation spectra. Wears and accessories designs for use by astronauts aim to minimize these deleterious effects of this environment. Polymeric materials are preferred in astronaut suits because they are lightweight, inexpensive, and durable. Teflon, KEVLAR, ethylene tetrafluoroethylene, DYNEEMA, and NOMEX polymeric astronaut wear materials were exposed to high energetic proton irradiations by the use of Monte Carlo simulation tools SRIM-2013 and FLUKA 2011.1. Proton energies are applied as 1, 2, and 3 GeV known as in order of space radiation magnitude. Besides, displacement per atom calculations were done and results were discussed in the plane of structural changes in the given polymeric materials. After interacting with protons with 1, 2, and 3 GeV energies, the material with the lowest Displacement per atom value among the five studied materials is DYNEEMA with values of 1.01E − 25, 9.96E − 26, and 1.00E − 25, respectively. Again, among the materials studied for these three proton energies, DYNEEMA has the highest electronic stopping power values are, respectively, 2.11E − 03, 2.10E − 03, and 2.31E − 03. DYNEEMA has the highest nuclear stopping power values as 2.23E − 07, 1.53E − 07, and 4.27E − 07, respectively.

Radiation Hardness Assurance Testing of Microelectronic Devices and Integrated Circuits: Radiation Environments, Physical Mechanisms, and Foundations for Hardness Assurance

This document describes the radiation environments, physical mechanisms, and test philosophies that underpin radiation hardness assurance test methodologies. The natural space radiation environment is presented, including the contributions of both trapped and transient particles. The effects of shielding on radiation environments are briefly discussed. Laboratory radiation sources used to simulate radiation environments are covered, including how to choose appropriate sources to mimic environments of interest. The fundamental interactions of radiation with materials via direct and indirect ionization are summarized. Some general test considerations are covered, followed by in-depth discussions of physical mechanisms and issues for total dose and single-event effects testing. The purpose of this document is to describe why the test protocols we use are constructed the way they are. In other words, to answer the question: “Why do we test it that way”?

Using radiation risk for assessment of space radiation hazard

Radiation hazard caused by exposure during a spaceflight is characterized by radiobiological consequences at all levels of organism. These consequences have a stochastic nature. Even deterministic effects are basically random quantity having all attributes of such mathematical values. The radiation risk is defined in this case as an additional probability of health damage or as a death probability in extreme case. For the manned spaceflight additional peculiarity of a human’s exposure is added. A natural space radiation environment has a stochastic character because solar particle events and crew of a spacecraft can be exposed to dose from background level up to lethal one. The report presents a procedure of radiation risk assessment for quantitative expression of radiation hazard level during a flight and using this value for developing protection recommendations. It is emphasized that the risk value is connected specifically with the time interval of possible hazard’s existent. The form of risk representation must be chosen depending on a time scale of radiobiological processes induced by the exposure (expressing in fact the radiation hazard model). Surviving function specified for the crewmember mortality rate changed by the professional exposure must be used for risk calculation. Solar particle events determine a stochastic character of radiation environment in space that must be taken into account for a risk assessment. The reliability of radiation risk assessment can be used for this goal.

Guest Editorial: Nanophotonics for Space Applications

The application of cutting-edge photonics technology for improving the performance of space-based assets has resulted in a myriad of success stories. As early as 1981, the first photonics-based active fiber optic data links aboard the NASA Long Duration Exposure Facility (Air Force Experiment, AFWL Experiment 701, Fiber Optic Space Effects), during a 69-month orbital period in the Van Allen radiation belts convincingly demonstrated that optical fibers, III-IV laser diodes and detectors, and other photonics technology to follow would have a major role in reducing the dependency on expensive, complexly-wired system technologies, while reducing weight and volume. The proof-of-concept experiment verified the contention that reduced-size photonic systems could reduce satellite weight and volumes while dramatically increasing the bandwidth, reliability, and survivability of commercial and military satellite communication and data acquisition systems. Most importantly, the experiment provided the first conclusive evidence that properly designed photonic systems could provide excellent resistance to the natural space radiation and temperature environment. More recently, QD and nanostructure-based photovoltaic and nonlinear components and sensor arrays operating from visible wavelengths to far-IR are under investigation for near-term application in space systems. Cutting-edge photonic-nanophotonic components, materials, and systems under investigation include radiation-resistant, QD-based chip-sized nonlinear inertial guidance systems, focal plane arrays, thin film solar cells, polymer detectors, polymer modulators, active-smart optical windows, and specialized coatings, to name but a few applications, several of which are presented in this special section. The recent evolution of exotic photonic technology involving integration of nanotechnology with polymers and new molecular-hybrid nanomaterials have shown a high potential for potentially improving specific extra-terrestrial applications, as discussed in this special section. The diverse potential applications are well represented in this section and include papers on protective optical limiting coatings for spacebased sensors (Sarkar et al.), radiation-resistant properties of photovoltaic solar cells (Hubbard et al.), mitigation of Lunar regolith using nanoparticle smart coatings (Pirich et al.), and evolving radiationresistant EO polymer modulator materials (Zhang and Taylor). Recently announced plans by NASA to return to the Moon in 2020 as well as other potential interplanetary space missions will require lightweight polymer-based shielding materials for crew cabins and the protection of astronauts and components from galactic cosmic rays (GCR) during lunar surface exploration and interplanetary missions. Nanotechnology is expected to play a role in the development of some of these materials. Traditional radiation high-Z shielding materials such as lead and other heavy elements are not suitable for GCR protection since the interaction of GCR with these materials results in the production of secondary radiation which is harmful to humans and can degrade photonic and electronic components. Radiation transport calculations have shown that hydrogen-rich low-Z materials are more effective per unit mass of shield than heavier shielding elements for xor gamma-ray absorption because of their lower cross sections, and because heavier elements can serve as the sources of dose-producing secondary particles such as short-range heavy nuclear fragments and penetrating neutrons. Thus, a challenge to develop new nano-based materials and radiation-resistant photonic components for space applications appears to be well under way. Hopefully the initial sampling of papers presented in this special section on Nanophotonics for Space Applications will be well received and provide new ideas from the readership for addressing the special needs of the photonics space community. Journal of Nanophotonics, Vol. 3, 031899 (19 November 2009)

Total-dose radiation hardness assurance

Total-dose radiation hardness assurance is reviewed for MOS and bipolar devices and integrated circuits (ICs), with an emphasis on issues addressed by recent revisions to military and commercial standard test methods. Hardness assurance typically depends upon sample tests of a subgroup of devices or circuits to determine whether the full group meets its performance and functionality requirements to a desired confidence level. The dose rates of many standard test methods match neither the very high dose rates of some military environments nor the very low dose rates of most space environments. So, one must ensure that hardness assurance test plans address device response in the radiation environment of interest. An increasing emphasis has been placed over the last few decades on standardized test procedures to qualify devices for use in the natural space radiation environment. Challenging issues for defining test methods for space environments are nMOS transistor threshold-voltage rebound and enhanced low-dose-rate sensitivity for linear bipolar devices and ICs. Effects of preirradiation elevated temperature stress on MOS radiation response are also a significant concern. Trends are identified for future radiation hardness tests on advanced microelectronics technologies.

Radiation effects in nematodes: Results from IML-1 experiments

The nematode Caenorhabditis elegans was exposed to natural space radiation using the ESA Biorack facility aboard Spacelab on International Microgravity Laboratory 1, STS-42. For the major experimental objective dormant animals were suspended in buffer or on agar or immobilized next to CR-39 plastic nuclear track detectors to correlate fluence of HZE particles with genetic events. This configuration was used to isolate mutations in a set of 350 essential genes as well as in the unc-22 structural gene. From flight samples 13 mutants in the unc-22 gene were isolated along with 53 lethal mutations from autosomal regions balanced by a translocation eT1 (III;V). Preliminary analysis suggests that mutants from worms correlated with specific cosmic ray tracks may have a higher proportion of rearrangements than those isolated from tube cultures on a randomly sampled basis. Flight sample mutation rate was approximately 8-fold higher than ground controls which exhibited laboratory spontaneous frequencies.

Reliable fiber optics for the adverse nuclear environment

Optical fiber system applications have progressed beyond massive production for long-haul telecommunications systems to special systems for military use. The environmental requirements for military systems are extreme. Aircraft systems must endure extreme shock during takeoff and landing on aircraft carriers and thermal shock during a rapid climb from the desert floor to 50,000 ft. Ship systems must weather continuous salt water spray, and space systems must survive the natural space radiation environment. All these systems as well as fixed and mobile ground-based installations may be required to endure the potential threat from nuclear weapons. Research efforts have improved the reliability and survivability of fiber optic systems under these adverse conditions. Radiation test results over extreme temperature ranges have verified that optical fibers have been developed to meet the most adverse of conditions. The establishment of proper test procedures and appropriate evaluation techniques will provide reliable fiber optic components for the adverse nuclear environment.

Radiation testing of semiconductor devices for space electronics

Radiation effects testing, part selection, and hardness assurance for application to electronic components in the natural space environment are discussed. The emphasis is on semiconductor devices, primarily silicon microcircuits, which are used in the greatest quantity and which, in most cases, are the most sensitive. After a summary of the natural space radiation environment and the effects of radiation on semiconductor devices, laboratory simulation of space radiation and extrapolation to space are covered. Radiation testing is performed to understand failure mechanisms, to characterize the radiation response of specific devices, and to provide data for lot acceptance. Part selection and hardness assurance are discussed by contrasting the traditional approach with the unique aspects of space systems. Some recommendations are made for treating the more complex aspects of space system microcircuit hardness assurance.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Radiation Effects in High Tc Superconductors for Space Applications

YBa2Cu3O7 is one of the new class of superconductors having a critical temperature (Tc) above 90 K. Devices using these materials would require minimal refrigeration to operate in space. It is important, therefore, to determine the effect of natural space radiation on these materials. Preliminary experiments have been performed to study displacement damage and ionization effects in 100?m thick films of YBa2Cu3O7. Samples of these films were irradiated at room temperature with 1) 56 MeV electrons up to a total fluence of 1.6×1015 cm-2, 2) 6 MeV protons up to a total fluence of 5.0×1013 cm-2, and 3) 63 MeV protons up to a total fluence of 1.09×1014 cm-2. It is concluded from the electron irradiations that the major effect of ionization is to increase the normal resistivity of the material. Although Tc(onset) was not much affected by either the electron or the proton irradiations, Tc(completion) varied substantially with proton fluence and at the higher fluences there was evidence of a non-superconducting region even at 4 K. It appears from the shape of the resistivity-temperature curve that high energy proton irradiation induces a partially superconducting multi-phase mosaic. Comparing worst case space environments to the radiations described above, it is concluded that this high Tc material could be made to remain superconducting for extended space missions with only moderate shielding.

Spacecraft Hardness Assurance Programs

This paper describes hardness assurance experience gained from several programs including the production of DSCS (Defense Satellite Communications System) III spacecraft. The data and conclusions are applicable to both natural space and nuclear radiation environments. The hardness assurance programs included semiconductor lot sample tests and latchup screening of integrated circuits. The lot sample testing included both displacement and ionization damage induced by reactor and Cobalt-60 sources, respectively, and prompt dose burnout using flash x-ray (FXR) exposure. Test results and resolution of failed lots are discussed. Significant observations and issues for future technology studies are presented.

Radiation Effects in Microelectronics for Space Instruments

The natural space radiation environment must be considered when microelectronic components are selected for use in space instruments. The designer must be concerned with damage effects due to the total accumulated doses as well as soft upsets and latchup caused by single nuclear events. Methods of estimating the importance of these problems will be discussed and treatments for them will be described.

Hardness Assurance Experience on the DSCS III Spacecraft Program

This paper describes hardness assurance experience gained during the production of three DSCS (Defense Satellite Communications System) III spacecraft. The program approach is applicable to both natural space and nuclear explosive radiation environments. This hardness assurance program included semiconductor lot sample tests and latchup screening of certain integrated circuits. The lot sample testing included both displacement damage and ionization damage induced by reactor and Cobalt-60 sources, respectively, and prompt dose testing using high level flash x-ray (FXR) exposure. Test results and resolution of failed lots are discussed. Significant observations and issues for future technology studies are presented in the areas of both displacement and ionization damage, prompt dose stress (burnout) and latchup.

Radiation Fields in Spacecraft

The radiation environment to be found inside spacecraft, either in free space or earth-orbiting, is reviewed. The three main components of natural space radiation - galactic, solar, and trapped - are presented with a brief description of the important physical characteristics of each. The greatest known hazard to space travellers will come from rare large solar-particle events.

Space radiation dose rates in the earth's atmosphere.

This paper presents a calculation of nuclear radiation dose rates within the earth's atmosphere due to natural space radiation. Two conditions are considered—active sun and quiet sun. The active sun environment includes depressed galactic (cosmic) radiation fluxes and solar flare radiation based upon a model similiar to the Bailey model event. The quiet sun environment includes only the nondepressed galactic radiation. The spectra for both environments were truncated at the geomagnetic cutoff energy for the undisturbed field. Atmospheric attenuation was taken into account by using simple range-energy relations. Asymptotic nuclear reaction cross sections were used to calculate cascade and evaporation secondary fluxes. Gibson's flux-to-rad-dose conversion function and Rossi's RBE-LET relationship were used to yield rad and rem dose rates. In this way, dose rates as a function of altitude (10,000-100,000 ft) and geomagnetic latitude (0-90°) for both active and quiet sun conditions were obtained. The significance of the dose rates obtained for passengers and crew members of the Supersonic Transport (SST) is discussed.

Components and Application Techniques for Electronic Circuitry Operating in Nuclear Environments

A discussion is presented of the effects of steady-state, pulsed, and natural space radiation on electronic equipment. The effects of steady-state irradiations of various active and passive circuit element materials with up to 1020 nvt of fast neutrons and 1012 r of gamma rays are outlined. The effects of gamma pulses of about 100 to 107 r/sec on the responses and properties of circuit elements are discussed. The effects of dose rate on conductivity of various insulators is shown at several temperatures. The nature of space radiations is considered.