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At least 127 records · Page 7

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NASA NTRS1992

A parallel-series-fed microstrip array with high efficiency and low cross-polarization

The requirements of a microstrip array with a vertically polarized fan beam are addressed that correspond to its use in C-band interferometric SAR. A combination of parallel- and series-feed techniques are utilized in an array design with a three-stage parallel-fed configuration to enhance bandwidth performance. The linearly polarized traveling-wave microstrip array antenna is fed by microstrip transmission lines in two rows of 36 elements that resonate at 5.30 GHz. The transmission lines are impedance-matched at every junction for all the waves that travel toward the two ends of the array. The two measured principal-plane patterns are shown, and the measured narrow-beam pattern is found to agree with the calculated values. The VSWR bandwidths and narrow and broad beamwidths of the antenna are found to permit efficient performance. The efficiency is attributed to the parallel and series-feed configuration which allows proper impedance matching, and low cross-polarization is a result of the antiphase feed technique employed in the configuration.

Huang, John↗

NASA NTRS1988

Development of a 39.5 GHz Karp traveling wave tube for use in space

A millimeter-wave TWT was developed using a dispersive, high-impedance forward wave interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The 'Tunneladder' interaction structure combines ladder properties modified to accommodate Pierce gun beam optics on a radially magnetized PM focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to each ridge of a double ridged waveguide. Cold-test data are presented, representing the omega-Beta and impedance characteristics of the modified ladder circuit These results were used in small and large-signal computer programs to predict TWT gain and efficiency. A laboratory model tube was designed and fabricated, including all major subassemblies.

Jacquez, A.↗

DOE OSTI2025

EIC Crab Cavity LLRF Studies

The Electron-Ion Collider Crab Cavity Low-Level Radio Frequency system will have to reduce the Crab Cavity impedance to prevent transverse instabilities, while regulating the crabbing voltage and minimizing the Radio Frequency noise levels injected to the beam. These are challenging and partly conflicting requirements. This works summarizes the specifications to achieve these requirements and investigates the possible trade-offs in the architecture.

43 PARTICLE ACCELERATORS↗

DOE OSTI2025

Single-Bunch Instabilities Driven by Space Charge During Low-Energy Cooling at Injection in the EIC Hadron Storage Ring

This paper presents a simulation-based study of single-bunch dynamics at the injection energy of 23.8 GeV for protons in the EIC hadron storage ring, focusing on the impact of space-charge–driven instabilities. The analysis demonstrates that at this energy, the proton bunch experiences significant transverse space-charge forces, which can reduce the stability margin in the presence of the geometric and resistive wall impedance. Various collective effects were considered, with particular attention to the nonlinear nature of the transverse space charge. To stabilize the beam, high chromaticity and octupoles were introduced and their effects analyzed using the ELEGANT code. The results provide a quantitative assessment of the stability thresholds and offer guidance for the machine design and operational strategy at injection.

43 PARTICLE ACCELERATORS↗

NASA NTRS2005

Structural and Acoustic Damping Characteristics of Polyimide Microspheres

A broad range of tests have been performed to evaluate the capability of tiny lightweight polyimide spheres to reduce sound and vibration. The types of testing includes impedance tube measurement of propagation constant, sound power insertion loss for single and double wall systems, particle frame wave characterization and beam vibration reduction. The tests were performed using spheres made of two types of polyimide and with varying diameter. Baseline results were established using common noise reduction treatment materials such as fiberglass and foam. The spheres were difficult to test due to their inherent mobility. Most tests required some adaptation to contain the spheres. One test returned obvious non-linear behavior, a result which has come to be expected for treatments of this type. The polyimide spheres are found to be a competent treatment for both sound and vibration energy with the reservation that more work needs to be done to better characterize the non-linear behavior.

Palumbo, Daniel L.↗

DOE OSTI2021

Manipulating ferroelectric behaviors via electron-beam induced crystalline defects

Ferroelectric nanoplates are attractive for applications in nanoelectronic devices. Defect engineering has been an effective way to control and manipulate ferroelectric properties in nanoscale devices. Defects can act as pinning centers for ferroelectric domain wall motion, altering the switching properties and domain dynamics of ferroelectrics. However, there is a lack of detailed investigation on the interactions between defects and domain walls in ferroelectric nanoplates due to the limitation of previous characterization techniques, which impedes the development of defect engineering in ferroelectric nanodevices. In this study, we applied in situ biasing transmission electron microscopy to explore how dislocation loops, which were judiciously introduced into barium titanate nanoplates via electron beam irradiation, affect the motion of ferroelectric domain walls. The results show that the motion was dramatically suppressed by these localized defects, because of the local strain fields induced by the defects. Additionally, the pinning effect can be further enhanced by multiple domain walls embedded with defect arrays. These results indicate the possibility of manipulating domain switching in ferroelectric nanoplates via the electron beam.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

NASA NTRS1988

A millimeter-wave tunneladder TWT

A millimeter-wave traveling wave tube (TWT) was developed using a dispersive, high-impedance forward wave interaction structure based on a ladder, with non-space-harmonic interaction, for a tube with high gain per inch and high efficiency. The 'TunneLadder' interaction structure combines ladder properties modified to accommodate Pierce gun beam optics in a radially magnetized PM focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to diamond cubes which are in turn active diffusion brazed to each ridge of a doubly ridged waveguide. Cold-test data, representing the (omega)(beta) and and impedance characteristics of the modified ladder circuit, were used in small and large-signal computer programs to predict TWT gain and efficiency. The structural design emphasizes ruggedness and reliability. Actual data from tested tubes verify the predicted performance while providing broader bandwidth than expected.

Wilson, D.↗

NASA NTRS1988

A millimeter-wave tunneLadder TWT

A millimeter wave traveling wave tube was developed using a dispersive, high impedance forward interaction structure based on a ladder, with non-space harmonic interaction, for a tube with high gain per unit length and high efficiency. The TunneLadder interaction structure combines ladder properties modified to accommodate Pierce gun beam optics in a radially magnetized permanent magnet focusing structure. The development involved the fabrication of chemically milled, shaped ladders diffusion brazed to diamond cubes which are in turn active-diffusion brazed to each ridge of a doubly ridged waveguide. Cold test data are presented, representing the omega-beta and impedance characteristics of the modified ladder circuit. These results were used in small and large signal computer programs to predict TWT gain and efficiency. Actual data from tested tubes verify the predicted performance while providing broader bandwidth than expected.

Jacquez, A.↗

DOE OSTI2026

Impedance and wakefield studies of the EIC RCS 591 MHz five-cell cavity

The Electron-Ion Collider (EIC) is a next-generation accelerator complex designed to enable high-luminosity collisions between highly polarized electrons and light ions (e.g., He-3). A central component of its Electron Injection System (EIS) is the Rapid Cycling Synchrotron (RCS), which accelerates a single 28 nC electron bunch from 750 MeV to 5, 10, or 18 GeV using an array of 591 MHz five-cell superconducting RF (SRF) cavities—eight at the current design stage. To ensure stable acceleration of high-charge bunches, we conducted detailed impedance and wakefield studies of the SRF cavity structure using both frequency- and time-domain methods. Wakefield solvers (ECHO3D, ECHO1D, CST), eigenmode analysis, and multi-particle tracking with ELEGANT were employed to evaluate longitudinal and transverse impedance effects and to determine instability thresholds. These studies provide critical input for the cavity design and operating parameters required to preserve beam quality and stability in the RCS.

Accelerator Physics↗

NASA NTRS1985

Mass spectra of neutral particles released during electrical breakdown of thin polymer films

A special type of time-of-flight mass spectrometer triggered from the breakdown event was developed to study the composition of the neutral particle flux released during the electrical breakdown of polymer films problem. Charge is fed onto a metal-backed polymer surface by a movable smooth platinum contact. A slowly increasing potential from a high-impedance source is applied to the contact until breakdown occurs. The breakdown characteristics is made similar to those produced by an electron beam charging system operating at similar potentials. The apparatus showed that intense instantaneous fluxes of neutral particles are released from the sites of breakdown events. For Teflon FEP films of 50 and 75 microns thickness the material released consists almost entirely of fluorocarbon fragments, some of them having masses greater than 350 atomic mass units amu, while the material released from a 50 micron Kapton film consists mainly of light hydrocarbons with masses at or below 44 amu, with additional carbon monoxide and carbon dioxide. The apparatus is modified to allow electron beam charging of the samples.

Kendall, B. R. F.↗

NASA NTRSDate not supplied

A Dual Linear/Circular Polarized Wideband Flat Panel Phased Array Antenna for K/Ka-band 6U CubeSat Communications Applications

Circular polarized (CP) electromagnetic waves are preferred for space-to-space and space-to-ground satellite communications (SATCOM). CubeSats with 6U sizes (1U represents a 10 cm x 10 cm x 10 cm), that will rotate together with the Moon as it orbits Earth require high gain CP antenna systems to maintain reliable communication links. Here, we have designed an 8x8 dual linear and dual circularly polarized phased array antenna (PAA) aperture that offers 22-28 GHz bandwidth, with maximum gain of 23 dBic, and beam scanning capability of ±50o with acceptable axial ratio over all scan angles. A stacked patch topology is selected to achieve wide impedance bandwidth. Each driven patch has two via feed point locations that are connected to grounded coplanar waveguide (CPW) feed structures. By utilizing phase shifters from the Anokiwave RFICs (AWMF-0165) employed for the beamforming network (BFN), we have generated both dual linear polarization and dual circular polarization in each patch. Each driven and parasitic patch is innovatively shaped to achieve excellent isolation between two feed points which, in turn, leads to low cross polarization, high efficiency and good axial ratio over the entire bandwidth. Each chip has eight outputs which feed one 2x2 sub-array consisting of four dual linear or dual circularly polarized driven patches, simultaneously. Each 2x2 sub-array of the 8x8 array are sequentially rotated which improves axial ratio performance when the antenna operates in the dual circularly polarized mode. By utilizing a mirror effect, cross-polarized fields are also improved when operated in a dual linear polarized mode. The 8x8 array aperture is simulated taking into account the effect of the multilayer printed circuit board (PCB) stack-up of the BFN and co-simulated with the power splitter outputs and chip outputs and results are compared with only passive array performance. The performance of the antenna is still excellent when non-ideal chip performances are included in the simulation analysis. The fabricated array will be tested for radiation patterns in the Antenna and Microwave Laboratory (AML) of the San Diego State University and the NASA Glenn Research Center (GRC) spherical near field chambers. The design of the 8x8 antenna array with BFN layout is shown in Fig. 1.

5G↗

DOE OSTI2022

Conversion of Classical Light Emission from a Nanoparticle‐Strained WSe 2 Monolayer into Quantum Light Emission via Electron Beam Irradiation

Abstract Solid‐state single photon emitters (SPEs) within atomically thin transition metal dichalcogenides (TMDs) have recently attracted interest as scalable quantum light sources for quantum photonic technologies. Among TMDs, WSe 2 monolayers (MLs) are promising for the deterministic fabrication and engineering of SPEs using local strain fields. The ability to reliably produce isolatable SPEs in WSe 2 is currently impeded by the presence of numerous spectrally overlapping states that occur at strained locations. Here nanoparticle (NP) arrays with precisely defined positions and sizes are employed to deterministically create strain fields in WSe 2 MLs, thus enabling the systematic investigation and control of SPE formation. Using this platform, electron beam irradiation at NP‐strained locations transforms spectrally overlapped sub‐bandgap emission states into isolatable, anti‐bunched quantum emitters. The dependence of the emission spectra of WSe 2 MLs as a function of strain magnitude and exposure time to electron beam irradiation is quantified and provides insight into the mechanism for SPE production. Excitons selectively funnel through strongly coupled sub‐bandgap states introduced by electron beam irradiation, which suppresses spectrally overlapping emission pathways and leads to measurable anti‐bunched behavior. The findings provide a strategy to generate isolatable SPEs in 2D materials with a well‐defined energy range.

2D material↗

NASA NTRSDate not supplied

Cognitive Tapered Slot Circular Array Antenna for Lunar Surface Communications

In this paper, we present the design of a cognitive tapered slot circular array (TSCA) antenna with multiple electronically switched sector beams for lunar surface communication. The circular array is capable of sensing the frequency, power, and direction of arrival of the RF signals. The design of the TSCA builds on our prior work on the development of a single TSA element with a balanced microstrip/coax feed. The measured return loss of the single TSA element shows wide bandwidth with good impedance match across the 5 to 35 GHz frequency range. Additionally, the single TSA has good radiation patterns. The single TSA serves as the building block for a four-element TSCA with multiple electronically switched sector beams for sensing and communications.

Cognitive communications↗

NASA NTRSDate not supplied

Cognitive Tapered Slot Circular Array Antenna for Lunar Surface Communications

Antenna↗

NASA NTRS1992

Method and apparatus for minimizing multiple degree of freedom vibration transmission between two regions of a structure

Arrays of actuators are affixed to structural elements to impede the transmission of vibrational energy. A single pair is used to provide control of bending and extensional waves and two pairs are used to control torsional motion. The arrays are applied to a wide variety of structural elements such as a beam structure that is part of a larger framework that may or may not support a rigid or non-rigid skin. Electrical excitation is applied to the actuators that generate forces on the structure. These electrical inputs may be adjusted in their amplitude and phase by a controller in communication with appropriate vibrational wave sensors to impede the flow of vibrational power in all of the above mentioned wave forms beyond the actuator location. Additional sensor elements can be used to monitor the performance and adjust the electrical inputs to maximize the attenuation of vibrational energy.

Silcox, Richard J.↗

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 NTRS1993

Analysis of microstrip dipoles and slots transversely coupled to a microstrip line using the FDTD method

Printed dipole elements and their complement, linear slots, are elementary radiators that have found use in low-profile antenna arrays. Low-profile antenna arrays, in addition to their small size and low weight characteristics, offer the potential advantage of low-cost, high-volume production with easy integration with active integrated circuit components. The design of such arrays requires that the radiation and impedance characteristics of the radiating elements be known. The FDTD (Finite-Difference Time-Domain) method is a general, straight-forward implementation of Maxwell's equations and offers a relatively simple way of analyzing both printed dipole and slot elements. Investigated in this work is the application of the FDTD method to the analysis of printed dipole and slot elements transversely coupled to an infinite transmission line in a multilayered configuration. Such dipole and slot elements may be used in dipole and slot series-fed-type linear arrays, where element offsets and interelement line lengths are used to obtain the desired amplitude distribution and beam direction, respectively. The design of such arrays is achieved using transmission line theory with equivalent circuit models for the radiating elements. In an equivalent circuit model, the dipole represents a shunt impedance to the transmission line, where the impedance is a function of dipole offset, length, and width. Similarly, the slot represents a series impedance to the transmission line. The FDTD method is applied to single dipole and slot elements transversely coupled to an infinite microstrip line using a fixed rectangular grid with Mur's second order absorbing boundary conditions. Frequency-dependent circuit and scattering parameters are obtained by saving desired time-domain quantities and using the Fourier transform. A Gaussian pulse excitation is applied to the microstrip transmission line, where the resulting reflected signal due to the presence of the radiating element is used to determine the equivalent element impedance.

Tulintseff, A. N.↗

NASA NTRS1991

Integrated 222-GHz corner-reflector antennas

A high-gain monolithic millimeter-wave antenna has been designed, fabricated, and tested at 222 GHz. The structure consists of a traveling-wave antenna integrated on a 1.2-micron dielectric membrane and suspended in a longitudinal cavity etched in a silicon wafer. A new traveling-wave antenna design yields a wideband input impedance and a low cross-polarization component in the E- and quasi-H-plane patterns. A directivity of 17.7 dB and a main-beam efficiency of 88.5 percent are calculated from the 222-GHz pattern measurements. The integrated corner-reflector antenna is well suited for millimeter- and submillimeter-wave imaging applications in large f-number systems.

Gearhart, Steven S.↗