[en] The hybrid integration of an injection laser with a simple avalanche transistor modulator is shown to produce optical peak powers of several tens of watts magnitude and pulse rise times appreciably shorter than 1 ns. In certain circumstances the pulse leading edge assumes the form of a spike having a displayed rise time of 120 ps. (U.S.)

No abstract available

No abstract available

[en] Novel improved power metal oxide semiconductor field effect transistor (MOSFET) drive circuits are introduced. An anti-deadlock block is used in the P-channel power MOSFET drive circuit to avoid deadlocks and improve the transient response. An additional charging path is added to the N-channel power MOSFET drive circuit to enhance its drive capability and improve the transient response. The entire circuit is designed in a 0.6 μm BCD process and simulated with Cadence Spectre. Compared with traditional power MOSFET drive circuits, the simulation results show that improved P-channel power MOSFET drive circuit makes the rise time reduced from 60 to 14 ns, the fall time reduced from 240 to 30 ns, and its power dissipation reduced from 2 to 1 mW, while the improved N-channel power MOSFET drive circuit makes the rise time reduced from 360 to 27 ns and its power dissipation reduced from 1.1 to 0.8 mW. (semiconductor integrated circuits)

[en] The block-diagram and operation of a magnetron modulator are presented and considered. The modulator includes a magnetron, a controllable current source, a switch, a storage capacitor, a current transducer and a comparison element connected in a circle. An inductance coil is switched for decrease of pulse decay time between the magnetron cathode and input of current transducer, that ensures fast discharge of parasitic capacities. The developed modulator may be successfully used in pulse SHF-generators

No abstract available

[en] This work describes the digital down-shift (DDS) technique, a new method of extracting short rise-time velocity profiles in the analysis of optically up-converted PDV data. The DDS technique manipulates the PDV data by subtracting a constant velocity (i.e., the DDS velocity νDDS) from the velocity profile. DDS exploits the simple fact that the optically up-converted data ride on top of a base velocity (ν0, the apparent velocity at no motion) with a rapid rise to a high velocity (νf) of a few km/s or more. Consequently, the frequency content of the signal must describe a velocity profile that increases from ν0 to ν0 + νf. The DDS technique produces velocity reversals in the processed data before shock breakout when ν0 < νDDS < ν0 + νf. The DDS analysis process strategically selects specific DDS velocities (velocity at which the user down shifts the data) that produce anomalous reversals (maxima and/or minima), which are predictable and easy to identify in the mid-range of the data. Additional analysis determines when these maxima and minima occur. By successive application of the DDS technique and iterative analysis, velocity profiles are extracted as time as a function of velocity rather than as a function of time as it would be in a conventional velocity profile. Presented results include a description of DDS, velocity profiles extracted from laser-driven shock data with rise times of 200 ps or less, and a comparison with other techniques.

No abstract available

[en] The three-mode theory due to Mindlin and McNiven [J. Appl. Mech. 27, 145--151 (1960)], governing axisymmetric motions in a circular rod, is appraised by comparing responses predicted by it with experimental data obtained by Miklowitz and Nisewanger [J. Appl. Mech. 24, 240--244 (1957)]. The problem studied involves a semi-infinite rod, made of 24S-T aluminum alloy, subjected to pressure applied to the end of the rod. The two sets of responses are compared at various stations along the rod. To make the comparisons meaningful, it was necessary to recognize that the pressure applied experimentally had a finite rise time, however short; to make an estimate from the responses of what that rise time might be; and then apply this time distribution of pressure in evaluating the theoretical responses. Comparison shows that the Mindlin--McNiven theory predicts the responses at stations farther than one diameter from the end of the rod. The matching is accurate not only at the head of the impulse but at points representing large times following the first disturbance

[en] X-ray pulses with a risetime of 10^-11s or shorter (e.g. to pump certain X-ray lasers) could be realized by interposing a series of absorbers between the X-ray source and target, and evaporating the absorber (e.g. with the X-ray beam itself). The expected dependence of risetime on absorber material and dimensions, X-ray energy and original pulse shape is discussed. (Auth.)