Characterizing the influence of neutron fields in causing single-event effects using portable detectors

The malfunction of semiconductor devices caused by cosmic rays is known as Single Event Effects(SEEs). In the atmosphere, secondary neutrons are the dominant particles causing this effect. The neutron flux density in atmosphere is very low. For a good statistical certainty, millions of device hours are required to measure the event rate of a device in the natural environment. Event rates obtained in such testings are accurate. To reduce the cost and time of getting the event rate, a device is normally taken to artificial accelerated neutron beams to measure its sensitivity to neutrons. Comparing the flux density of the beam and the flux density of a location in the atmosphere, the real time event rate can be predicted by the event rate obtained. This testing method was standardized as the neutron accelerated soft error rate (ASER) testing in JEDEC JESD89A standard. However, several life testings indicated that the neutron flux density predictions given by the accelerated testings can have large errors. Up to a factor of 2 discrepancy was reported in the literature. One of the major error sources is the equivalence of the absolute neutron flux density in the atmosphere and in accelerated beam. This thesis proposes an alternative accelerated method of predicting the real-time neutron error rate by using proxy devices. This method can avoid the error introduced by the uncertainty in the neutron flux density. The Imaging Single Event Effect Monitor (ISEEM) is one of the proxy devices. It is the instrument originally developed by Z. Török and his co-workers in the University of Central Lancashire. A CCD was used as the sensitive element to detect neutrons. A large amount of data sets acquired by Török were used in this work. A re-engineered ISEEM has been developed in this work to improve ISEEM performance in life testings. Theoretical models have been developed to analyze the response of ISEEM in a wide range of neutron facilities and natural environment. The agreement of the measured and calculated cross-sections are within the error quoted by facilities. Because of the alpha contamination and primary proton direct ionization effects, performance of ISEEM in life testings appeared to be weak

Radiation health research, 1986 - 1990

A collection of 225 abstracts of radiation research sponsored by NASA during the period 1986 through 1990 is reported. Each abstract was categorized within one of four discipline areas: physics, biology, risk assessment, and microgravity. Topic areas within each discipline were assigned as follows: Physics - atomic physics, nuclear science, space radiation, radiation transport and shielding, and instrumentation; Biology - molecular biology, cellular radiation biology, tissue, organs and organisms, radioprotectants, and plants; Risk assessment - radiation health and epidemiology, space flight radiation health physics, inter- and intraspecies extrapolation, and radiation limits and standards; and Microgravity. When applicable subareas were assigned for selected topic areas. Keywords and author indices are provided

Gadolinium Oxide/Silicon Thin Film Heterojunction Solid-State Neutron Detector

The internal conversion electron emission from the de-excitation of the Gd-158m nucleus was explored as a means for neutron detection. Thin film gadolinium oxide (Gd2O3) and p-type silicon heterojunction diodes were produced using a supercritical water deposition process. Pulse height spectroscopy was conducted on the novel diodes while they were subjected to a moderated plutonium-beryllium (PuBe) source flux of 104 thermal neutrons/cm2 s. Coincident gamma spectroscopy was employed to verify the 1107.6 keV photon emissions from the diode indicative of successful neutron capture by Gd-157 and the subsequent de-excitation of the Gd-158m nucleus. Neutron capture in the diodes could not be confirmed experimentally. The diodes were found to be sensitive to gamma rays between 10 and 20 keV

Development of Novel Sensor Devices for Total Ionization Dose Detection

abstract: Total dose sensing systems (or radiation detection systems) have many applications, ranging from survey monitors used to supervise the generated radioactive waste at nuclear power plants to personal dosimeters which measure the radiation dose accumulated in individuals. This dissertation work will present two different types of novel devices developed at Arizona State University for total dose sensing applications. The first detector technology is a mechanically flexible metal-chalcogenide glass (ChG) based system which is fabricated on low cost substrates and are intended as disposable total dose sensors. Compared to existing commercial technologies, these thin film radiation sensors are simpler in form and function, and cheaper to produce and operate. The sensors measure dose through resistance change and are suitable for applications such as reactor dosimetry, radiation chemistry, and clinical dosimetry. They are ideal for wearable devices due to the lightweight construction, inherent robustness to resist breaking when mechanically stressed, and ability to attach to non-flat objects. Moreover, their performance can be easily controlled by tuning design variables and changing incorporated materials. The second detector technology is a wireless dosimeter intended for remote total dose sensing. They are based on a capacitively loaded folded patch antenna resonating in the range of 3 GHz to 8 GHz for which the load capacitance varies as a function of total dose. The dosimeter does not need power to operate thus enabling its use and implementation in the field without requiring a battery for its read-out. As a result, the dosimeter is suitable for applications such as unattended detection systems destined for covert monitoring of merchandise crossing borders, where nuclear material tracking is a concern. The sensitive element can be any device exhibiting a known variation of capacitance with total ionizing dose. The sensitivity of the dosimeter is related to the capacitance variation of the radiation sensitive device as well as the high frequency system used for reading. Both technologies come with the advantage that they are easy to manufacture with reasonably low cost and sensing can be readily read-out.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Exploration of radiation damage mechanism in mems devices.

We explored UV, X-ray and proton radiation damage mechanisms in MEMS resonators. T-shaped MEMS resonators of different dimensions were used to investigate the effect of radiation. Radiation damage is observed in the form of resistance and resonance frequency shift of the device. The resistance change indicates a change in free carrier concentration and mobility, while the resonance frequency change indicates a change in mass and/or elastic constant. For 255nm UV radiation, we observed a persistent photoconductivity that lasts for about 60 hours after radiation is turned off. The resonance frequency also decreases 40-90 ppm during irradiation and slowly recovers at about the same time scale as the resistance during annealing. For X-ray radiation, the resonance frequency decreases with radiation, but the resistance increases. To investigate X-ray dose-rate dependence, we irradiated the resonators at three different dose rates of X-ray: 5.4, 10.9 and 30.3 krad(SiO2)/min. The change in resonance frequency and resistance both showed a dose rate dependence where a lower dose-rate X-ray caused a larger shift in resonance frequency than the higher dose-rate. We attributed the observed shift in resonance frequency to the change in carrier concentration—using Keyes’ theory of electronic contribution to elastic constant—for both X-ray and UV radiation. The resistance change is explained by the net effect of the carrier concentration and mobility change. We proposed that the carrier concentration changes through two differing mechanisms for X-ray and UV radiation. For X-ray, dopant depassivation is primarily responsible for the carrier concentration change since an X-ray is known to dissociate the hydrogen-boron complex and it penetrates through the 15μm thick Si resonator affecting the whole bulk of Si. On the contrary, the 255nm UV gets absorbed near the surface (within 10nm) and charges the native oxide. The mirror charge on adjacent silicon is responsible for the carrier concentration change. The mirror charges drive the silicon surface to accumulation, depletion or strong inversion depending on the type and amount of charge trapped in the oxide. Since the carrier concentration only changes near the surface, it was predicted that higher surface-to-volume ratio devices will show a greater shift in resonance frequency. This was proven by radiating three devices with differing widths (1, 2 and 8μm), and therefore differing surface-to-volume ratios. This experiment verified that the UV light effect is surface dominated. The dimensional dependence is also observed for X-ray radiation damage. We found that a reduction in the surface-to-volume ratio enhances the X-ray radiation damage and we proposed a hydrogen diffusion-based model that fits the observed dimensional dependence of X-ray radiation damage. For proton radiation, the direction of resonance frequency change depended on the energy of radiated proton. Two proton energies were tested: 0.8MeV and 2MeV. The proton with 0.8MeV energy stops inside the resonator, causing greater displacement damage than the proton with 2MeV energy, which readily passes through the resonator. The 2MeV proton causes more ionization damage than the 0.8MeV protons. So, the observed energy dependence of resonance frequency shift comes from the competing effects of displacement damage and ionization damage since resonance frequency decreases due to ionization damage but increases due to displacement damage. The result agrees with our theory since the 0.8MeV proton radiation showed net resonance frequency increase during radiation and more permanent damage after annealing compared to the 2MeV proton radiation

Impact of Space Weather on Climate and Habitability of Terrestrial Type Exoplanets

The current progress in the detection of terrestrial type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favorable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of astrospheric, atmospheric and surface environments of exoplanets in habitable zones around G-K-M dwarfs including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles, and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favorable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro) physical, chemical, and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the habitable zone to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.Comment: 206 pages, 24 figures, 1 table; Review paper. International Journal of Astrobiology (2019

大電力用半導体デバイスの宇宙線故障率計算手法

Power semiconductor devices are susceptible to catastrophic failures when exposed to energetic particles present in cosmic radiation. The most serious failure mechanism is single event burnout (SEB). SEB in terrestrial operating condition is a widely recognized problem due to the usage of high Power semiconductor devices in many terrestrial applications. However, the recent increase in the aircraft power requirement and subsequent demand for high power semiconductor devices in avionics indicates the importance of expanding SEB study to higher altitudes. Moreover, the SEB failure rate in avionic system is many times higher than terrestrial electronics due to the increase in cosmic ray flux at high altitudes. The calculation of SEB failure rate of power devices plays critical role in power device selection to make the system robust against cosmic radiation. The failure rate calculation using modeling approaches is very easy and offers many advantages compare to real life tests and accelerated tests. However, empirical formula proposed by Zeller from the accelerating testing result can only be applicable to evaluate the failure rate at sea level. In this research, a universal failure calculation method is proposed to evaluate the failure rate of any high power semiconductor device. Unique feature of decoupling between failure cross section and cosmic ray flux spectrum in the proposed method makes it possible to calculate the failure rate in any radiation condition like terrestrial conditions, aviation altitudes, space environment etc. The failure rate results shown for PiN diodes of 100 μm (1) and 300 μm (3) due to the interaction of cosmic ray neutrons up an altitude of 60 km. First chapter provides the basic introduction about purpose of this work, the research objectives and importance of proposed failure rate calculation method. Second chapter describes the origin of radiation along with the radiation environment. The interaction of radiation with the matter and in particular the discovery of Single Event Effects in electronic integrated circuits is discussed. Moreover, we discussed the reason for considering the cosmic ray neutrons in the present work. Third chapter presents the literature review about energetic particle interaction with the high power semiconductor devices. The phenomena leading to device destruction also discussed in various power devices in detail. Fourth chapter describes the Single Event Burnout simulation of PiN diode. The physical process leading to the failure is shown for 300 μm and 100 μm PiN diode using the simulation results. The transient current waveforms are shown to differentiate the burnout and non-burnout situations. Fifth chapter introduces the proposed universal failure rate calculation method. Various components of the failure calculation method are discussed in detail. The threshold charge for device destruction obtained from simulation results is shown for 300 μm and 100 μm PiN diode. Sixth chapter presents results obtain from the proposed method. The calculated failure rate at sea level is validated with the Zeller results. Further, altitude dependent failure rate up to 60 km is obtained using the neutron spectrum from EXPACS database. In addition, the cutoff energy dependence on failure rate also briefly discussed.九州工業大学博士学位論文 学位記番号: 生工博甲第428号 学位授与年月日: 令和4年3月25日1 Introduction|2 Radiation and its effects on Electronics|3 SEB in High power semiconductor devices|4 Simulation of Single Event Burnout phenomena of PiN Diode|5 Proposed Universal SEB Failure rate calculation method|6 Failure rate results|7 Conclusion九州工業大学令和3年

Characterizing the influence of neutron fields in causing single-event effects using portable detectors

The malfunction of semiconductor devices caused by cosmic rays is known as Single Event Effects(SEEs). In the atmosphere, secondary neutrons are the dominant particles causing this effect. The neutron flux density in atmosphere is very low. For a good statistical certainty, millions of device hours are required to measure the event rate of a device in the natural environment. Event rates obtained in such testings are accurate. To reduce the cost and time of getting the event rate, a device is normally taken to artificial accelerated neutron beams to measure its sensitivity to neutrons. Comparing the flux density of the beam and the flux density of a location in the atmosphere, the real time event rate can be predicted by the event rate obtained. This testing method was standardized as the neutron accelerated soft error rate (ASER) testing in JEDEC JESD89A standard. However, several life testings indicated that the neutron flux density predictions given by the accelerated testings can have large errors. Up to a factor of 2 discrepancy was reported in the literature. One of the major error sources is the equivalence of the absolute neutron flux density in the atmosphere and in accelerated beam. This thesis proposes an alternative accelerated method of predicting the real-time neutron error rate by using proxy devices. This method can avoid the error introduced by the uncertainty in the neutron flux density. The Imaging Single Event Effect Monitor (ISEEM) is one of the proxy devices. It is the instrument originally developed by Z. Török and his co-workers in the University of Central Lancashire. A CCD was used as the sensitive element to detect neutrons. A large amount of data sets acquired by Török were used in this work. A re-engineered ISEEM has been developed in this work to improve ISEEM performance in life testings. Theoretical models have been developed to analyze the response of ISEEM in a wide range of neutron facilities and natural environment. The agreement of the measured and calculated cross-sections are within the error quoted by facilities. Because of the alpha contamination and primary proton direct ionization effects, performance of ISEEM in life testings appeared to be weak.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Space Settlements: A Design Study

Nineteen professors of engineering, physical science, social science, and architecture, three volunteers, six students, a technical director, and two co-directors worked for ten weeks to construct a convincing picture of how people might permanently sustain life in space on a large scale, and to design a system for the colonization of space. Because the idea of colonizing space has awakened strong public interest, the document presented is written to be understood by the educated public and specialists in other fields. It also includes considerable background material. A table of units and conversion factors is included to aid the reader in interpreting the units of the metric system used in the report

NASA thesaurus. Volume 1: Hierarchical Listing

There are over 17,000 postable terms and nearly 4,000 nonpostable terms approved for use in the NASA scientific and technical information system in the Hierarchical Listing of the NASA Thesaurus. The generic structure is presented for many terms. The broader term and narrower term relationships are shown in an indented fashion that illustrates the generic structure better than the more widely used BT and NT listings. Related terms are generously applied, thus enhancing the usefulness of the Hierarchical Listing. Greater access to the Hierarchical Listing may be achieved with the collateral use of Volume 2 - Access Vocabulary and Volume 3 - Definitions