Charles E. Barnes

Emerging radiation hardness assurance (RHA) issues: a NASA approach for space flight programs

Spacecraft performance requirements drive the utilization of commercial-off-the-shelf (COTS) components and emerging technologies in systems. The response of these technologies to radiation is often complex. This engenders a set of emerging radiation hardness assurance (RHA) issues which include displacement damage in optocouplers, high-precision and hybrid devices, enhanced low dose rate (ELDR) and proton damage enhancement (PDE) in linear circuits, linear transients, and catastrophic single event effects (SEEs) phenomena. NASA has developed an approach to designing reliable space systems which address these emerging RHA issues. This programmatic methodology includes hazard definition, hazard evaluation, requirements definition, evaluation of device usage, and application of radiation engineering techniques with the active involvement of designers. Risk assessment is an integral constituent in the approach as is an established program to assess future technology needs for programs.

Total dose and proton damage in optocouplers

Radiation damage from gamma rays and protons is investigated for two types of optocouplers with different physical configurations. Far more damage occurs from protons because of displacement damage, which reduces the photoresponse of the phototransistor and causes severe degradation in LED light output for one of the two device types. The other device type was far more resistant to radiation, primarily because it used a shorter wavelength LED that was relatively unaffected by protons.

Accounting for time-dependent effects on CMOS total-dose response in space environments

Abstract Time-dependent charge buildup and annealing processes cause the ionizing radiation response of CMOS devices and circuits to depend strongly on the dose rate of the exposure. Oxide-trap charge annealing and interface-trap buildup in nMOS transistor can lead to positive threshold voltage shifts in a space environment, while negative threshold voltage shifts are commonly observed after irradiations at typical laboratory dose rates [50–300 rad(Si)/s]. Thus, devices that pass laboratory testing can fail at the low dose rates encountered in space due to positive nMOS transistor threshold-voltage shifts above preirradiation values, i.e. “rebound”. We summarize how this issue can be addressed in total-dose hardness assurance test methods for space. An example of such a guideline is the revised U.S. military-standard ionizing-radiation-effects test method (MIL-STD 883D, Test Method 1019.4).

Radiation effects in photonic modulator structures

A review is given of the effects of radiation on various photonic modulator materials and devices including polymer-based structures, insulator-based devices, semiconductor-based devices, and spatial light modulators. We conclude by providing recommendations for further work in the area of radiation effects in photonic modulators.

Recent photonics activities under the NASA Electronic Parts and Packaging (NEPP) program

With the rapidly increasing insertion of photonic devices, circuits and subsystems into NASA spacecraft, a variety of issues associated with reliability and radiation tolerance have arisen. In this paper, we discuss these issues from the perspective of the work currently ongoing in the NASA Electronic Parts and Packaging (NEPP) Program. This Program is focused on evaluating the reliability and radiation response of advanced and emerging microelectronics and photonics technologies of interest to NASA spacecraft system designers. Examples to be discussed include radiation studies of various optoelectronic devices and reliability of photonic components. These studies have been motivated in part by problems observed in space that include the failure of optocouplers on TOPEX/Poseidon, and the observation of single event-induced transients in the Hubble Space Telescope.

Measurements and results of gamma-radiation-induced attenuation at 980-nm of single-mode fiber

Radiation testing of 980 nm single mode optical fiber, at 120 krads total dose was performed at three temperatures (minus 30 degrees Celsius, plus 96 degrees Celsius, and room temperature). Testing was also performed on samples from different sections of the optical fiber drawn from a single preform that was designed for a lower cutoff wavelength this fiber is referred to as (Flight), and an off-the-shelf (OTS) 980 nm optical fiber from the same manufacture. The results of this data are discussed in this paper and a projection of the damage to the optical fibers over a five year period was done using the nth order kinetic model developed by J. Friebele et al.

Observation of radiation induced changes in stress and electrical properties in MOS devices

Strain measurements using X-ray diffraction were performed on irradiated commercial and radiation-hardened metal gate CMOS devices in addition to polysilicon gate NMOS devices. I-V curves were taken and V/sub ot/ and V/sub it/ were separated using the subthreshold slope method for all devices. A correlation has been shown to exist between physical strain relaxation and the electrical properties as a function of radiation dose and recovery. Data shown suggest that the physical response (strain relaxation) in the silicon at the oxide interface is a measure of the type of damage induced and the recovery mechanism. Postradiation measurements of triangle V/sub it/ and triangle V/sub ot/ taken immediately after irradiation support the conclusions of V. Zekeriya and T.-P. Ma (1983) and K. Kasama et al. (1986,1987); compressive stress at the silicon/SiO/sub 2/ interface does reduce radiation damage in the device. >

Overview of fiber optics in the natural space environment

The potential applications of fiber-optic (FO) systems in spacecraft which will be exposed to the space radiation environment are discussed in view of tests conducted aboard the Long-Duration Exposure Facility and the Comet Rendezvous and Asteroid Flyby spacecraft. Attention is given to anticipated trends in the use of FO in spacecraft communications systems. The natural space radiation environment is noted to be far more benign than the military space environment, which encompasses displacement-damage effects due to significant neutron influences

Effect of neutron irradiation on the properties of AlGaAs/GaAs laser diodes

The effects of neutron irradiation on several properties of both single and multiple stripe laser diodes have been examined. Prior to fast neutron irradiation, total light output as a function of laser current, threshold current, near-field pattern, far-field pattern, and laser output wavelength spectra were measured at room temperature. These measurements were then repeated at intermittent neutron fluence levels. It was observed that the threshold current increased with neutron fluence for all devices examined. In contrast, neutron irradiation had only an indirect effect on the remainder of the laser diode properties in that the higher currents required for operation after irradiation caused variations in these properties.

Optical fibers in the adverse space environment - The Space Station

On the NASA Space Station, the requirement for high speed data transfer between the exterior experimental bays and the interior research facilities has generated the need for fiberoptics. The adverse vacuum effects in space, temperature extremes, and natural space radiation place extreme conditions on optical fiber interconnects. This report addresses the adverse space environmental effects of temperature and radiation on optical fibers.