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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

AMAROK: A Radio Frequency Development Platform for High-Power, Full-Scale Positive Ion Sources for DIII-D Neutral Beam Injectors

Next-generation neutral beam injection (NBI) systems demand RF ion sources capable of efficiently coupling >120 kW at 2–4-MHz frequencies, yet existing designs face voltage standoff and impedance-matching challenges. To address this, the advanced multicoil antenna for RF operations at kilowatts (AMAROK) was developed as a high-power RF inductively coupled plasma (ICP) source delivering up to 200 kW in the 2–4-MHz range via four phase-controlled generators for flexible power sharing. Two antenna designs—a single-strap multiturn (MT) and a multistrap single-turn (ST) design—were evaluated to optimize resonance, impedance matching, and power coupling across plasma loads. Here, a semi-analytical self-resonant frequency (SRF) model, validated experimentally, predicts resonance trends for arbitrary turn counts and tubing diameters, enabling rapid antenna optimization. Strap-to-strap mutual inductance in the ST configuration showed strong spatial dependence, guiding generator operation and total load inductance. These insights informed a custom π -topology matching network, achieving stable impedance matching over a wide range of plasma-driven loads. Collectively, these results position AMAROK as a versatile testbed for advancing high-power RF source technology in fusion NBI applications.

DIII-D↗
NASA NTRS1972

Evidence for a common origin of the electrons responsible for the impulsive X-ray and type III radio bursts.

Observations of impulsive solar flare X-rays greater than or about equal to 10 keV made with the OGO-5 satellite are compared with ground-based measurements of type III solar radio bursts in 10- to 580-MHz range. It is shown that the times of maxima of these two emissions, when detectable, agree within about 18 sec. This maximum time difference is comparable to that between the maxima of the impulsive X-ray and impulsive microwave bursts. In view of the various observational uncertainties, it is argued that the observations are consistent with the impulsive X-ray, impulsive microwave, and type III radio bursts being essentially simultaneous. The observations are also consistent with 10- to 100-keV electron streams being reponsible for the type III emission. The observations indicate that the non-thermal electron groups responsible for the impulsive X-ray, impulsive microwave, and type III radio bursts are accelerated simultaneously in essentially the same region of the solar atmosphere.

Kane, S. R.↗
NASA NTRS1974

A new high-speed solar radio spectrograph for meter and decameter wavelengths

The design and characteristics of a high resolution, digital solar spectrograph are discussed. The spectrometer operates in the 10 to 80 MHz range. The primary considerations in the design of the spectrograph were: (1) optimun sensitivity, (2) wide dynamic range, (3) flexibility in time and frequency resolution, and (4) modern data handling techniques with a simple computer interface.

Mosier, S. R.↗
NASA NTRS1977

CO2 laser communication systems for near-earth space applications

Projections of the growth of earth-sensing systems for the latter half of the 1980's show a data-transmission requirement of 300 Mbit/s and above. The most efficient technique to return the data from a sensing satellite to a ground station is through a geosynchronous data relay satellite. A laser system is most attractive for the space-to-space link. A five-year program was conducted which has shown the basic technical feasibility of accomplishing this link with a CO2 laser system operating at a wavelength near 10 microns. The system uses a mercury-cadmium-telluride infrared mixer cooled to approximately 100 K by a radiative cooler. The laser local oscillator and coupling-modulated laser transmitter use conductively cooled beryllium oxide construction. The optical antenna for transmission and reception has a gain of nominally 92 dB with a 3-dB beamwidth of 80 microrad. Tracking jitter is less than ten microrad, and signal acquisition occurs in less than 1 min. The receiver subsystem has a sensitivity of 10 to the -19th power W/Hz, accommodates a 300-Mbit/s data rate, and can track Doppler frequency variations over a + or - 700-MHz range.

Mcelroy, J. H.↗
NASA NTRS1979

Simultaneous multifrequency observations of Jovian S bursts

The millisecond component of the Jovian decameter emission was studied at high resolution in order to examine the short-term behavior of the S-burst drift rates and to define the drift rate spectrum at high frequencies. By using dynamic spectra of 300 microsec and 3.3 kHz resolution and covering discrete frequency bands in the 26-33 MHz range, large systematic changes in the magnitude of the S-burst drift rates are observed on a time scale of seconds to minutes. The drift rate variability, its dependence on frequency, and absence of the predicted drift rate turnover in the spectrum are interpreted in terms of an ionospheric electron source. Low-resolution intensity-time tracings, abrupt changes in mean drift rates from group to group, and systematic variations in the group-to-group mean drift rates due to predictable temporal changes in the magnetic field gradient on the Io flux tube are discussed. These temporal changes are due to motion of the Io-associated magnetic flux tube in the Jovian magnetosphere.

Flagg, R. S.↗
NASA NTRS1980

The WISP/HF system for Spacelab

The high frequency part of the waves in space plasmas system, WISP/HF, is a flexible shuttle Spacelab instrument for transmitting, receiving, and processing signals in the 0.3 to 30 MHz range. It permits a wide range of plasma wave experiments in the ionosphere including studies of the transmitting antenna, fundamentals of electromagnetic (EM) and electrostatic (ES) waves in magnetoplasmas, instabilities and nonlinearities, and remote sounding of ionospheric structure. Collaborative investigations involving other WISP equipment (e.g., antenna and propagation studies with the WISP/VLF system) or other Spacelab facilities (e.g., beam plasma interactions using charged particle guns) are envisaged. A few specific examples illustrate the relevance of WISP/HF to current scientific interest. The overall goal is to help build a comprehensive understanding of plasmaspheric wave physics through group studies.

James, H. G.↗
NASA NTRS1980

Ultrasonic imaging using trapped energy mode Fresnel lens transducers

Trapped-energy focusing transducers operating in the 2-5 MHz range have been fabricated by plating concentric rings of electrodes on a piezoelectric plate. The concentric ring structure acts as a Fresnel lens and can be used to obtain excellent lateral focusing of ultrasonic waves. The trapping is sufficiently strong to permit optimization of electrode spacings to suppress spurious virtual foci and ring sidelobes.

Das, P.↗
NASA NTRS1981

Lightning amplitude spectra in the interval from 100 kHz to 20 MHz

The electric radiation fields produced by lightning return strokes, stepped leaders, and intracloud discharge processes have been Fourier-analyzed to determine amplitude spectra for these processes from about 100 kHz to 20 MHz. The fields were recorded under conditions where the lightning locations were known and where the field propagation from the lightning sources to the recording site was entirely over salt water. The spectra for return strokes show an f exp -1 frequency dependence from 100 kHz to 2 MHz, an f exp -2 dependence between 2 and 10 MHz, and an f exp -5 decrease above 10 MHz. In the 1 to 20 MHz range, the spectra of the initial fast transition in return strokes, the initial fast-rising portion of leader steps and the fast transitions in positive intracloud pulses are surprisingly similar.

Weidman, C. D.↗
NASA NTRS1982

Control structures for high speed processors

A special processor was designed to function as a Reed Solomon decoder with throughput data rate in the Mhz range. This data rate is significantly greater than is possible with conventional digital architectures. To achieve this rate, the processor design includes sequential, pipelined, distributed, and parallel processing. The processor was designed using a high level language register transfer language. The RTL can be used to describe how the different processes are implemented by the hardware. One problem of special interest was the development of dependent processes which are analogous to software subroutines. For greater flexibility, the RTL control structure was implemented in ROM. The special purpose hardware required approximately 1000 SSI and MSI components. The data rate throughput is 2.5 megabits/second. This data rate is achieved through the use of pipelined and distributed processing. This data rate can be compared with 800 kilobits/second in a recently proposed very large scale integration design of a Reed Solomon encoder.

Maki, G. K.↗
NASA NTRS1981

Radio observations of Abell clusters and a comparison with certain Einstein observations

Areas around 70 clusters have been observed at the Arecibo Observatory primarily for coordination with about 60 Einstein X-ray sources. Arecibo source coordinates and flux density are tabulated, and some identifications are made with cataloged radio sources. Statistical estimates are made of the percentage of cluster sources among all sources in certain areas and to limits on the flux density of 430 MHz. Arecibo and other radio data are compared with the available Einstein data of seven clusters. Not every Einstein source has a radio counterpart, and the counterparts may variously be bilobed, tailed, or single. A parameter which is proportional to source continuum power at 430 MHz ranges over fewer orders of magnitude than the associated source X-ray luminosity, with no certain correlation between these parameters. NRAO Green Bank interferometer observations of A401 and A2142 are reported.

Johnson, H. M.↗
NASA NTRS1982

Optogalvanic stabilization and offset tuning of a carbon dioxide waveguide laser

A feedback loop employing the change in discharge impedance with output power is used to stabilize the frequency of a CO2 waveguide laser. The relatively high operating pressure of the laser combined with a zero offset feature in the feedback loop allows continuous tuning of the stabilized frequency over a 300-400 MHz range.

Kavaya, M. J.↗
NASA NTRS1980

Analysis of aging data on SAW oscillators

Test oscillators including delay lines and resonators in the 300-400 MHz range have been investigated with reference to the long-term stability (aging) characteristics. All devices were fabricated on rotated Y-cut quartz plates (40 deg), and either gold or platinum metallization was used; all packages were high-quality hermetic enclosures, and the mounting was strictly mechanical, with no organics or silicone rubbers used. It is shown that drift of less than 2 ppm in the first year can be obtained on a significant fraction of the devices when reasonably clean packages are used. The data also suggest that the transducer metallization (at least for aluminum) is very likely the source of the relaxation mechanism that causes the frequency drift.

Parker, T. E.↗
NASA NTRS1983

Satellite systems requirements for land mobile communications

The system design objective is to provide a satellite link through a gateway station, connecting mobile users in areas not served by a terrestrial cellular system to the switched telephone network (STN). The proposed frequency allocation comprises a pair of 10-MHz bands in the 806-890 MHz range specified by the 1979 World Administrative Radio Conference (WARC) for land-mobile satellite service (LMSS). The satellite design is constrained by projected STS capability with an upper stage of the wide-body Centaur or Integral Propulsion System (IPS) type. For the latter (a TRW design), the payload is limited to approximately 10,400 lb. The design is to be based on 1990's technology, with initial operating capability scheduled for 1995. The satellite should be designed for a 7-year life. Mobile-unit compatibility with cellular system specifications is desirable, if consistent with other system requirements.

Horstein, M.↗
NASA NTRS1982

The Clark Lake Teepee-Tee telescope

A new, fully steerable, decametric array for radio astronomy has been built at the Clark Lake Radio Observatory near Borrego Springs, California. This array is a 'T' of 720 conical spiral (teepee-shape) antennas, 3.0 km by 1.8 km. It is capable of operating between 15 and 125 MHz but has best sensitivity in the 25 to 75 MHz range. Both its operating frequency and beam position are adjustable in about 1 msec. A 1024-channel digital correlator has been built and attached to the array. This permits the simultaneous measurement of the complex visibility functions on 512 interferometer baselines between various portions of the array. After Fourier transformation these visibility data yield a 32 x 32 resolution element picture of the area of sky under observation, with frequency-dependent angular resolution ranging from 20 to 2.7 arcsec and a sensitivity of 1 Jy per beam. This system is described, and some initial observations are presented.

Erickson, W. C.↗
NASA NTRS1984

Partial Reflection Spaced Antenna Wind Measurements

The nature of partially reflecting (PR) irregularities is briefly reviewed and the techniques used in the PR spaced antenna method are discussed. The radars addressed use frequencies in the 2 to 6 MHz range operate in a pulse mode at vertical incidence. Radar system parameters including receiver dynamic range, coherent and incoherent detection, and post detection filtering are examined. Finally, data system parameters and real time analysis techniques are discussed.

Fraser, G. J.↗
NASA NTRS1986

Fade-Free Mobile Communication

Scheme for mobile communication reduces multipath fading and interference between adjacent channels. Proposed communication system lends itself to almost completely digital implementation, eliminating costly and bulky crystal filters. Scheme suitable for satellite-aided or terrestrial mobile communication, including cellular mobile telephony, at frequencies in 150-to-900-MHz range.

Stevenson, C. R.↗
NASA NTRS1990

Single-frequency diode-pumped lasers for free-space optical communication

Recent advances in laser technology for intersatellite optical communication systems are reviewed and illustrated with graphs and diagrams. Topics addressed include (1) single-frequency diode-pumped Nd:YAG lasers of monolithic ring configuration (yielding 368-384 mW output power with 1-W pumping), (2) injection chaining of up to 10 monolithic resonators to achieve redundancy and/or higher output power, (3) 2-kHz-linewidth 5-mW versions of (1) which are tunable over a 30-MHz range for use as local oscillators in coherent communication, (4) resonant external modulation and doubling or resonant phase modulation of diode-pumped lasers, and (5) wavelength multiplexing.

Kane, Thomas J.↗