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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Self-scanned anode array with a microchannel plate electron multiplier - The SSANACON

A photoelectron counting detector utilizing a 128-element linear self-scanned anode array to collect the output of a dual microchannel plate electron multiplier is described. The operation of the detector, its spatial resolution and detection efficiency, and radiation behavior are discussed. The low-noise detector was developed for the Mariner Jupiter/Saturn mission UV spectrometer, and offers a large dynamic range and count rate of 0.003 per anode-sec. It can measure simultaneously two spatially separated signals differing by more than six orders of magnitude in count rate.

Broadfoot, A. L.↗
NASA NTRS1977

Extended performance solar electric propulsion thrust system study. Volume 5. Capacitor-diode voltage multiplier: Technology evaluation

A 1-kW capacitor-diode voltage multiplier (CDVM) was designed, fabricated and tested to demonstrate the power of feasibility of high power CDVM's and to verify the analytical techniques that had been used to predict the performance characteristics of a 6-kw CDVM. High efficiency (96.2%), a low ratio of component weight to power (0.55 kg/kW), and low output ripple voltage (less than 1%, peak to peak) were obtained during the operation of a 1-kW CDVM various input line, load current, and load fault conditions.

Martinelli, R. M.↗
NASA NTRS1978

A 30-cm mercury ion thruster performance with a 1 kW capacitor-diode voltage multiplier beam supply

A 1 kW solar array and capacitor-diode voltage multiplier converter (S/A-CDVM) was successfully integrated with a 30 cm diameter mercury ion thruster system to provide ion beam power. Measurements were made to compare steady state and transient response performance of a conventional bridge converter with the S/A-CDVM converter used for the ion beam supply. The ability to recover from screen to accelerator arcs and promptly re-establish stable thruster performance was demonstrated. Solar array transient response to thruster arcing was measured.

Terdan, F. F.↗
NASA NTRS1978

Medium power voltage multipliers with a large number of stages

Voltage multiplier techniques are extended at medium power levels to larger multiplication ratios. A series of dc-dc converters were built, with from 20 to 45 stages and with power levels up to 100 watts. Maximum output voltages were about 10,000 volts.

Harrigill, W. T.↗
NASA NTRS1977

Line strengths, collision strengths and excitation rates for multiply-charged silicon ions

In the present paper, the line strengths, collision strengths, and rate coefficients are calculated for a variety of transitions in multiply charged silicon ions from Si(VI) to Si(XIV). The line strengths are obtained by using Clementi wave functions for the ground-state configuration, and excited-state wave functions generated by a semiempirical method. The collision strengths are calculated in an LS coupling scheme in the distorted-wave approximation, neglecting exchange except for the helium-like transitions. These results are then integrated over a Maxwellian velocity distribution function to yield rate coefficients. The rates are presented graphically and also in terms of a two-parameter fit.

Davis, J.↗
NASA NTRS1978

30-cm mercury ion thruster performance with a 1 kW capacitor-diode voltage multiplier beam supply

A 1 kW Solar Array and Capacitor-Diode Voltage Multiplier Converter (S/A-CDVM) has been successfully integrated with a 30 cm-diameter mercury ion thruster system to provide ion beam power. Measurements were made to compare steady state and transient response performance of a conventional bridge converter with the S/A-CDVM converter used for the ion beam supply. The ability to recover from screen to accelerator arcs and promptly re-establish stable thruster performance was demonstrated. Solar array transient response to thruster arcing was also measured.

Terdan, F. F.↗
NASA NTRS1978

Medium power voltage multipliers with a large number of stages

Voltage multiplier techniques were extended at medium power levels to larger multiplication ratios. A series of DC-DC converters were built, with from 20 to 45 stages and with power levels up to 100 watts. Maximum output voltages were about 10,000 volts.

Harrigill, W. T.↗
NASA NTRS1978

Performance characteristics of high-conductivity channel electron multipliers

The paper describes a new type of continuous channel multiplier (CEM) fabricated from a low-resistance glass to produce a high-conductivity channel section and thereby obtain a high count-rate capability. The flat-cone cathode configuration of the CEM is specifically designed for the detection of astigmatic exit images from grazing-incidence spectrometers at the optimum angle of illumination for high detection efficiencies at XUV wavelengths. Typical operating voltages are in the range of 2500-2900 V with stable counting plateau slopes in the range 3-6% per 100-V increment. The modal gain at 2800 V was typically in the range (50-80) million. The modal gain falls off at count rates in excess of about 20,000 per sec. The detection efficiency remains essentially constant to count rates in excess of 2 million per sec. Higher detection efficiencies (better than 20%) are obtained by coating the CEM with MgF2. In life tests of coated CEMs, no measurable change in detection efficiency was measured to a total accumulated signal of 2 times 10 to the 11th power counts.

Timothy, J. G.↗
NASA NTRS1979

VHF frequency multiplier

Low-power step-recovery-diode frequency multiplier generates 361-MHz signal. Diode conducts when ac waveform is positive at its upper terminal. When voltage is negative, diode continues to conduct stored charge in its junction.

Cusack, J. A.↗
NASA NTRS1981

Four-quadrant CCD analog multiplier

Sequential processing technique improves accuracy when CCD-array signals are multiplied by weighting function to remove offsets. System uses two schemes to cancel undesired output contributions arising from prerequisite biases. First is spontaneous cancellation by multiple "nominally identical" devices; second is sequential cancellation where same devices are used repeatedly to form multiple products. Single device then successively subtracts products, eliminating effects of MOS-array threshold nonuniformities.

Brooks, C. W.↗
NASA NTRS1979

Crystallization kinetics in a multiply saturated basalt magma - An experimental study of Luna 24 ferrobasalt

The paper deals with the effects of kinetics on mineral/melt partitioning and on fractional crystallization for a Luna-24 ferrobasalt. The composition is nearly multiply saturated under lunar surface conditions, making it possible to study the response of several mineral phases to kinetic factors during cooling. The differential suppression of the temperature of appearance of olivine, clinopyroxene, and plagioclase causes changes in the liquid line of descent. The course of liquid line of descent is mapped as a function of the cooling rate, and the partitioning of elements between pyroxene/liquid and olivine/liquid is examined.

Grove, T. L.↗
NASA NTRS1981

Incoherent optical matrix-matrix multiplier

Real time processing capabilities in the context of reconnaissance sensors, two dimensional beamforming, etc. are addressed. Matrix-matrix multiplier concepts using incoherent light are studied.

Dias, A. R.↗
NASA NTRS1981

Power system design optimization using Lagrange multiplier techniques

An optimization technique using the Lagrange Multiplier Method is proposed to facilitate design of switching power converter systems. The essence of the optimization is to identify the optimal battery voltage level and switching frequency along with the detailed converter design so that the total system weight including the battery and the packaged converter is minimized, and concurrently all specified power circuit performances are satisfied.

Yu, Y.↗
NASA NTRS1982

Quantum efficiency of opaque CsI photocathodes with channel electron multiplier arrays in the extreme and far ultraviolet

The arrays are overcoated with a CsI photocathode in the VUV. The measurements are part of the development program for the Extreme Ultraviolet Explorer. Monochromatic light from a hollow cathode discharge source passing through a McPherson grazing incidence monochromator is used to illuminate the CsI photocathode. The beam diameter is kept small (approximately 2 mm) to confine it within the individual thickness strips. A bias grid is used to produce a 50-V/mm electric field to guarantee collection of all photoelectrons emitted by the CEMA (channel electron multiplier array) webbing. The CEMAs are operated with a gain of 2-3 x 10 to the 6th and are moderately saturated. A channeltron secondary transfer standard is used to determine the absolute QE in the EUV, whereas an NBS calibrated windowed photodiode is used to measure the FUV absolute QE. It is noted that the CsI gives a factor of 3 increase in the QE in the EUV and a factor of 50-5000 in the FUV.

Martin, C.↗
NASA NTRS1987

Implementation of a digital optical matrix-vector multiplier using a holographic look-up table and residue arithmetic

The design and implementation of a digital (numerical) optical matrix-vector multiplier are presented. The objective is to demonstrate the operation of an optical processor designed to minimize computation time in performing a practical computing application. This is done by using the large array of processing elements in a Hughes liquid crystal light valve, and relying on the residue arithmetic representation, a holographic optical memory, and position coded optical look-up tables. In the design, all operations are performed in effectively one light valve response time regardless of matrix size. The features of the design allowing fast computation include the residue arithmetic representation, the mapping approach to computation, and the holographic memory. In addition, other features of the work include a practical light valve configuration for efficient polarization control, a model for recording multiple exposures in silver halides with equal reconstruction efficiency, and using light from an optical fiber for a reference beam source in constructing the hologram. The design can be extended to implement larger matrix arrays without increasing computation time.

Habiby, Sarry F.↗
NASA NTRS1988

Arc lamp power supply using a voltage multiplier

A power supply is provided for an arc discharge lamp which includes a relatively low voltage high current power supply section and a high voltage starter circuit. The low voltage section includes a transformer, rectifier, variable resistor and a bank of capacitors, while the starter circuit comprises several diodes and capacitors connected as a Cockcroft-Walton multiplier. The starting circuit is effectively bypassed when the lamp arc is established and serves to automatically provide a high starting voltage to re-strike the lamp arc if the arc is extinguished by a power interruption.

Leighty, Bradley D.↗
NASA NTRS1987

Implementation of a fast digital optical matrix-vector multiplier using a holographic look-up table and residue arithmetic

The design and implementation of a digital (numerical) optical matrix-vector multiplier are presented. A Hughes liquid crystal light valve, the residue arithmetic representation, and a holographic optical memory are used to construct position coded optical look-up tables. All operations are performed in effectively one light valve response time with a potential for a high information density.

Habiby, Sarry F.↗