Rokutaro Koga

Heavy ion induced snapback in CMOS devices

Single-event-snapback (SES) susceptibilities of selected CMOS devices to heavy ions were measured using N, Ne, Ar, Cu, and Kr ion beams. Like latchup, snapback was observed macroscopically by detecting the abnormally high bias current condition. However, the snapback susceptibility characteristics differed from those of latchup, and consequently it was possible to measure the snapback responses unambiguously. The responses are expressed in terms of the cross section for varying bias and stopping power of ions. Test data indicate that CMOS devices with rather long channel lengths (on the order of 3 mu m) are free from SES when operated at about 5 V. However, current theories predict that this regenerative breakdown mode of upset may become very important at 5 V or below for devices with extremely short n-channel lengths. >

The Impact of Radiation-Induced Failure Mechanisms in Electronic Components on System Reliability

A methodology is described to incorporate destructive radiation effects into the reliability estimation for a space system. Examples are presented to illustrate how on-orbit system reliability can be estimated from test data from radiation-sensitive parts.

EOSCOR: A light weight, microprocessor controlled solar neutron detector

Abstract A light weight high energy neutron detector with vertical detection efficiency of 0.005 at 40 MeV and 1.4 m2 sensitive area has been developed for long duration super-pressure balloon flight observations of solar neutrons and gamma rays. It consists of two sets of four plastic scintillator hodoscopes separated by a 1 m time-of-flight path to observe n−p, C(n, p), and C(n, d) interactions. The neutrons interactions are separated from gamma ray events through TOF measurements. For a large flare, the signal from solar neutrons is expected to be an order of magnitude greater than that of the atmospheric background. The microprocessor controls the data acquisition, accumulation of histograms, and the encoding of data for the telemetry systems. A test flight of the detector was made with a zero-pressure balloon. The expected many-week duration of a super-pressure balloon flight would significantly increase the probability of observing 20–150 MeV neutrons from a medium or large flare.

50–500 MeV observations of LMC supernova 1987A

Abstract Since the discovery of the supernova outburst in the LMC in 1987, we have made two attempts (on day 55 and day 407) to measure the high energy gamma-ray flux in the range 50–500 MeV, by using a balloon borne spark chamber telescope. On day 55, no positive signal was seen from the source. A 3σ upper limit of 2.9 × 10 −5 ph cm −2 s −1 was obtained after the analysis of the spark chamber data. Preliminary analysis of the quick look data obtained in the second flight shows that the gamma-ray flux even on day 407 was less than 9 × 10 −4 ph cm −2 s −1 (3 σ ).

EOSCOR III, a High Energy Solar Neutron Detector

A light weight high energy neutron detector has been developed for the observation of 20-150 MeV solar flare neutrons on a long duration Sky Anchor balloon flight. It consists of two 1 m2 plastic scintillators separated by a 1 m time-of-flight path to detect the protons from n-p scattering and 12C(n, pX) interactions in the upper scintillator. Adiabatic isochronous light pipes view the scintillators. Time-of-flight and pulse height analysis are used to measure the proton velocity, to discriminate against albedo events, and to separate the slower moving protons from Compton electrons. The Monte Carlo efficiency calculations are compared with accelerator calibration results using mono-energetic neutrons. Some results from short duration high altitude balloon observations are presented.

50–500 MeV γ‐ray emission in the early phase of SN1987A

SN1987A was observed on 19th April 1987 with a combined high energy γ‐ray and hard x‐ray payload, flown on a stratospheric balloon from Alice Springs, Australia. The γ‐ray detector, sensitive in the energy range 50–500 MeV, was an optical spark chamber with 400cm2 area, a field of view of 60° FWHM and a time resolution of 10 μs. The counting rate profile at ∼2.2 mb float altitude has lead to a 3σ upper limit to the steady γ‐ray flux of 7×10−4 ph cm−2 s−1 in the 50–500 MeV range. This upper limit is compared to our predictions for the time profile of γ‐ray emission from SN1987A resulting from pulsar acceleration of particles to cosmic ray energies.