A linear electric motor has been built to study hydrodynamic instabilities at the interface between fluids subjected to acceleration. The facility is powered by 16 independent capacitor banks to provide arbitrary acceleration profiles up to 1000 times earth’s gravity. Electrical measurements include the current, magnetic field, acceleration, and projectile trajectory. The instability is observed with flash shadowgraphy. The shot turnaround time is <15 min and over 100 shots can be taken before replacing the armature and rails.
We present an approach to receive-mode broadband beam forming and jammer nulling for large adaptive antenna arrays as well as its efficient and compact optical implementation. This broadband efficient adaptive method for true-time-delay array processing (BEAMTAP) algorithm decreases the number of tapped delay lines required for processing an N-element phased-array antenna from N to only 2, producing an enormous savings in delay-line hardware (especially for large broadband arrays) while still providing the full NM degrees of freedom of a conventional N-element time-delay-and-sum beam former that requires N tapped delay lines with M taps each. This allows the system to adapt fully and optimally to an arbitrarily complex spatiotemporal signal environment that can contain broadband signals of interest, as well as interference sources and narrow-band and broadband jammers--all of which can arrive from arbitrary angles onto an arbitrarily shaped array--thus enabling a variety of applications in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of radio frequency (rf) photonic systems, as it uses a coherent optically modulated fiber-optic feed network, gratings in a photorefractive crystal as adaptive weights, a traveling-wave detector for generating time delay, and an acousto-optic device to control weight adaptation. Because the number of available adaptive coefficients in a photorefractive crystal is as large as 10(9), these photonic systems can adaptively control arbitrarily large one- or two-dimensional antenna arrays that are well beyond the capabilities of conventional rf and real-time digital signal processing techniques or alternative photonic techniques.
In this paper we present a new approach to efficient true-time-delay (TTD) beamforming for large adaptive phased arrays as well as its elegant and compact optical implementation. This Broadband and Efficient Adaptive Method for Time-delay Array Processing (BEAMTAP) algorithm decreases the number of tapped delay lines required to process an N-element phased array antenna from N to only 2, producing an enormous savings in delay-line hardware, especially for large arrays, while still providing the full N M degrees of freedom of a conventional N element time delay beamformer with AI taps each. This allows the system to fully and optimally adapt to an arbitrarily complex spatio-temporal signal environment that can contain broadband signals, noise, and narrowband and broadband jammers, all of which can arrive from arbitrary ranges and angles onto an arbitrarily shaped array. thus enabling a variety of application in radar, sonar, and communication. This algorithm is an excellent match with the capabilities of RF photonic systems using gratings in photorefractive crystals as adaptive weights, because the hardware implementation of tapped delay lines is the factor which limits the scalability of these systems to large arrays. Because the number of available adaptive coefficients in a photorefractive crystal is practically unlimited, these photonic systems can adaptively control very large l-D or 2-D phased arrays, that are well beyond the capabilities of conventional RF or real-time digital signal processing techniques.
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