Linear Trapping Research Articles

Lower hybrid heating of ionospheric ions due to ion ring distributions in the cusp

The stability of H+ and He++ ring distributions which have been observed downflowing into the cusp on the DE and S3‐3 satellites is examined in the context of the feedback of those instabilities on plasma of ionospheric origin (H+ and O+). Lower hybrid waves are excited by the ring distributions in three distinct phases of wave‐particle interaction: linear growth, trapping, and quasi‐linear diffusion. The latter phase accounts for most particle heating. Including background O+ and/or a He++ ring introduces new modes not present in a pure H+ plasma which play an important role in heating heavier ions. O+ is heated significantly more by a He++ ring than a H+ ring of comparable energy density. It is suggested that lower hybrid waves generated by downflowing ion ring distributions play a role in energizing ion conies in the cusp.

Diffusion in a two-region slab with an eroding boundary

The transient mass diffusion problem with linear irreversible trapping and external sources for a two-region slab which has one of its outer boundaries eroding at a prescribed rate and subjected to boundary condition of the third kind at both boundaries is analyzed and a zeroth order solution is presented for the concentration distribution in the medium as a function of time and position. To illustrate the application, numerical results are presented for the concentration distribution in the medium.

Whistler wave trapping in a density crest

The linear trapping of whistler waves in a field-aligned density crest is investigated experimentally and theoretically below ω=ωc/2 (half gyrofrequency). An experiment has been performed on antenna-excited whistler waves in a large magnetized plasma with a density crest. The phase and amplitude profiles of the whistler wave are measured along and across the crest. The results are compared with predictions based on ray theory. Laboratory observations have verified the characteristic behavior of crest trapping.

Inhomogeneous positron trapping in fatigued aluminum single crystals

Surface fatigue phenomena have been studied in 99.9999% aluminum single-crystal cantilever beams subjected to reverse bending, by using positron annihilation and X-ray diffraction techniques. The coincidence of about the same penetration depth of the surface fatigue damage and of the positrons resulted in a very high sensitivity of the positron technique which, combined with X-ray diffraction, yielded information after single fatigue cycles for a fatigue life of about 107 cycles. A linear positron trapping model based on an inhomogeneous distribution of two different types of traps has been developed by using and extending the principles of the simple linear trapping model for one type of traps. The lifetimes and the relative integrated intensities at annihilation of positrons in pairs of aluminum single-crystal specimens were measured as functions of the number of fatigue cycles during the fatigue hardening stages I and II, the two crystals being subjected to the same strain amplitude of 0.17%. Correlation between the positron results and the corresponding spots of von Laue back-reflections was obtained. In early stages of fatigue, two characteristic position lifetimes, the first being (215±15) ps and the second varying during fatigue from 230 ps to (260±15) ps, have been found and have been interpreted to originate from trapping of positrons at dislocation jog elements and voids/vacancy dipoles, respectively.

Carrier Injection into SiO2 from Si Surface Driven to Avalanche Breakdown by a Linear Ramp Pulse, and Trapping, Distribution and Thermal Annealing of Injected Holes in SiO2

A simple method to produce an avalanche breakdown with a constant avalanche current in the silicon substrate of a MOS diode and to inject hot carriers into the gate oxide is presented. The shift of flatband voltage and that of the breakdown voltage of an n-type MOS diode are observed by hole injection into the gate oxide grown in dry oxygen using the above method. It is observed that about 1/10 of the injected holes could be captured by traps in the gate oxide. It is indicated by both the bias-temperature treatment and the avalanche injection process that hole traps would be generated by avalanche injected holes in the gate oxide. The trapped holes are located near the Si–SiO2 interface decaying from that interface.