Search NASA⌕ Search

SEARCH · Search NASA

Results for “rf source”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Nonuniform sampling techniques for antenna applications

A two-dimensional sampling technique, which can employ irregularly spaced samples (amplitude and phase) in order to generate the complete far-field patterns is presented. The technique implements a matrix inversion algorithm, which depends only on the nonuniform sampled data point locations and with no dependence on the actual field values at these points. A powerful simulation algorithm is presented to allow a real-life simulation of many reflector/feed configurations and to determine the usefulness of the nonuniform sampling technique for the copolar and cross-polar patterns. Additionally, an overlapped window concept and a generalized error simulation model are discussed to identify the stability of the technique for recovering the field data among the nonuniform sampled data. Numerical results are tailored for the pattern reconstruction of a 20-m offset reflector antenna operating at L-band. This reflector is planned to be used in a proposed measurement concept of large antenna aboard the Space Shuttle, whereby it would be almost impractical to accurately control the movement of the Shuttle with respect to the RF source in prescribed directions in order to generate uniform sampled points. Also, application of the nonuniform sampling technique to patterns obtained using near-field measured data is demonstrated. Finally, results of an actual far-field measurement are presented for the construction of patterns of a reflector antenna from a set of nonuniformly distributed measured amplitude and phase data.

Rahmat-Samii, Yahya↗
NASA NTRS1987

Spaceborne Imaging Radar-C instrument

The present discussion of the Spaceborne Imaging Radar-C (SIR-C) hardware design, subsystem functional design, and interfaces with the NASA Space Shuttle, gives attention to antenna characteristics and to instrument performance parameter characteristics in the C- and L-bands. The SIR-C antenna is a dual-frequency, dual-polarization distributed array antenna whose distribution of transmit/receive modules improves the system noise figure and eliminates the need for a single, high-power RF source. Phase shifters for individual subarrays allow electronic beam steering in elevation and azimuth.

Huneycutt, Bryan L.↗
NASA NTRS1990

Electrooptic modulation methods for high sensitivity tunable diode laser spectroscopy

A CdTe phase modulator and low power RF sources have been used with Pb-salt tunable diode lasers operating near 8 microns to generate optical sidebands for high sensitivity absorption spectroscopy. Sweep averaged, first-derivative sample spectra of CH4 were acquired by wideband phase sensitive detection of the electrooptically (EO) generated carrier-sideband beat signal. EO generated beat signals were also used to frequency lock the TDL to spectral lines. This eliminates low frequency diode jitter, and avoids the excess laser linewidth broadening that accompanies TDL current modulation frequency locking methods.

Glenar, David A.↗
NASA NTRS1999

Dual polarized, heat spreading rectenna

An aperture coupled patch splits energy from two different polarization components to different locations to spread heat. In addition, there is no physical electrical connection between the slot, patch and circuitry. The circuitry is located under a ground plane which shields against harmonic radiation back to the RF source.

Epp, Larry W.↗
DOE OSTI2012

Ultra-High Gradient Compact S-Band Linac for Laboratory and Industrial Applications

There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The commonly used S-band SLAC-type structure has an operating gradient of only about 20 MV/m; while much higher operating gradients (up to 70 MV/m) have been recently achieved in X-band, as a consequence of the substantial efforts by the Next Linear Collider (NLC) collaboration to push the performance envelope of RF structures towards higher accelerating gradients. Currently however, high power X-band RF sources are not readily available for industrial applications. Therefore, RadiaBeam Technologies is developing a short, standing wave S-band structure which uses frequency scaled NLC design concepts to achieve up to a 50 MV/m operating gradient at 2856 MHz. The design and prototype commissioning plans are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Fast wave heating in the NSTX-Upgrade device

NSTX-Upgrade will operate with toroidal magnetic fields (B T) up to 1 T, nearly twice the value used in the experiments on NSTX, and the available NBI power will be doubled. The doubling of B T while retaining the 30 MHz RF source frequency has moved the heating regime from the high harmonic fast wave (HHFW) regime used in NSTX to the mid harmonic fast wave (MHFW) regime. By making use of the full wave code AORSA, this work shows that direct ion damping (mainly by thermal ions localized at the 5th harmonic resonance) might be significant in NSTX-Upgrade under TRANSP predicted full performance conditions and the electron and ion absorption is sensitive to the ratio of electron and ion temperature. Launching at high toroidal wave number appears to be one way to significantly reduce the ion damping. By using the extended AORSA code, which includes a detailed description of the scrape-off layer in the field solutions, we found a large electric field amplitude outside of the last closed flux surface as previously seen in NSTX from AORSA simulations (D. L. Green, et al, Phys. Rev. Lett. 107, 145001 (2011)). Preliminary results by introducing a collision damping in the scrape-off layer in the AORSA code to represent a damping process are presented, showing for the first time absorbed power in the scrape-off layer.

Bertelli, Nicola↗
DOE OSTI2017

Ion funnel device

An ion funnel device is disclosed. A first pair of electrodes is positioned in a first direction. A second pair of electrodes is positioned in a second direction. The device includes an RF voltage source and a DC voltage source. A RF voltage with a superimposed DC voltage gradient is applied to the first pair of electrodes, and a DC voltage gradient is applied to the second pair of electrodes.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2019

Low noise, high bandwidth, high sensitivity laser seismometer

A laser seismometer may measure the change in a phase modulated optical signal. Unlike traditional interferometers, the laser phase is first modulated by a radio frequency (RF) source, which is then demodulated following detection to provide the signal of interest. The net result is a direct measurement of displacement with the effects of amplitude noise eliminated via limiting and the effects of 1/f phase noise (frequency drift, etc.) eliminated by self-interfering the signal. Because the signal-to-noise ratio (SNR) of the optical signal is strong, the technique provides a strong measure of the displacement and avoids the extremely low voltages and associated problems of traditional sensors.

58 GEOSCIENCES↗
DOE OSTI2017

Status of the ITER Ion Cyclotron H&CD

The ITER Ion Cyclotron Heating and Current Drive system (IC H&CD) is designed to deliver 20MW to a broad range of plasma scenarios between 40 and 55MHz, during very long pulses. It consists of two broadband equatorial port plug antennas, their pre-matching and matching systems, transmission lines, Radio Frequency (RF) Sources and High Voltage Power Supplies. The overall project schedule has been revised and agreed by ITER Council; it re-integrates the second antenna and its power supplies in construction baseline and sets the dates for progressive installation with DT phase planned in 2035. Recent progress on ICRF subsystems is reported, covering design evolution, qualification of test articles and specific R&D results in domestic agencies, suppliers, associated laboratories and IO.

Agarwal, Rohit↗
DOE OSTI2022

High Efficiency Travelling Wave X-Band Linac With Tunable Output Energy

We are designing a compact and efficient electron linac with 500 W of average beam power and beam energy tunable from 5 to 10 MeV. The accelerator is of travelling wave type, and has little RF power reflected back to the RF source, eliminating the need for a large, lossy isolator. The structure is powered by a compact commercial 1.7 MW 9.3 GHz magnetron. To vary the beam energy we will change the current from the triode gun. We present an analysis of the structure, which includes varying the length from 60 cm to 80 cm, and the structure type, such as constant impedance versus constant gradient.

Romero, Agustin↗
DOE OSTI2017

A NEW THERMIONIC RF ELECTRON GUN FOR SYNCHROTRON LIGHT SOURCES

A thermionic RF gun is a compact and efficient source of electrons used in many practical applications. RadiaBeam Systems and the Advanced Photon Source at Argonne National Laboratory collaborate in developing of a reliable and robust thermionic RF gun for synchrotron light sources which would offer substantial improvements over existing thermionic RF guns and allow stable operation with up to 1A of beam peak current at a 100 Hz pulse repetition rate and a 1.5 μs RF pulse length. In this paper, we discuss the electromagnetic and engineering design of the cavity and report the progress towards high power tests of the cathode assembly of the new gun.

RF↗
DOE OSTI2015

Initial results of a full kinetic simulation of RF H{sup −} source including Coulomb collision process

In order to evaluate Electron Energy Distribution Function (EEDF) more correctly for radio frequency inductively coupled plasma (RF-ICP) in hydrogen negative ion sources, the Electromagnetic Particle-In-Cell (EM-PIC) simulation code has been improved by taking into account electron-electron Coulomb collision. Binary collision model is employed to model Coulomb collision process and we have successfully modeled it. The preliminary calculation including Coulomb collision has been done and it is shown that Coulomb collision doesn’t have significant effects under the condition: electron density n{sub e} ∼ 10{sup 18} m{sup −3} and high gas pressure p{sub H{sub 2}} = 3 Pa, while it is necessary to include Coulomb collision under high electron density and low gas pressure conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Self-induced steady-state magnetic field in the negative ion sources with localized rf power deposition

The study is in the scope of a recent activity on modeling of SPIDER (Source for Production of Ions of Deuterium Extracted from RF plasma) which is under development regarding the neutral beam injection heating system of ITER. The regime of non-ambipolarity in the source, established before, is completed here by introducing in the model the steady state magnetic field, self-induced in the discharge due to the dc current flowing in it. Strong changes in the discharge structure are reported.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

Spatial distribution of the plasma parameters in the RF negative ion source prototype for fusion

A numerical model, based on the fluid plasma theory, has been used for description of the spatial distribution of the plasma parameters (electron density and temperature, plasma potential as well as densities of the three types of positive hydrogen ions) in the IPP prototype RF negative hydrogen ion source. The model covers the driver and the expansion plasma region of the source with their actual size and accounts for the presence of the magnetic filter field with its actual value and location as well as for the bias potential applied to the plasma grid. The obtained results show that without a magnetic filter the two 2D geometries considered, respectively, with an axial symmetry and a planar one, represent accurately the complex 3D structure of the source. The 2D model with a planar symmetry (where the E×B and diamagnetic drifts could be involved in the description) has been used for analysis of the influence, via the charged-particle and electron-energy fluxes, of the magnetic filter and of the bias potential on the spatial structure of the plasma parameters in the source. Benchmarking of results from the code to experimental data shows that the model reproduces the general trend in the axial behavior of the plasma parameters in the source.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2015

INITIAL COMMISSIONING EXPERIENCE WITH THE SPALLATION NEUTRON SOURCE VERTICAL TEST AREA RF SYSTEM

The Spallation Neutron Source (SNS) has developed a vertical test area (VTA) for the testing and qualification of superconducting radio frequency cavities. The associated RF System successfully supported the initial commissioning of the VTA system and has been utilized for cavity testing at both 4 and 2 K. As operational experience was gained, improvements to the RF system were implemented to better utilize the dynamic range of the system, and software updates and additions were made to meet operational needs. The system continues to evolve as we gain better understanding of the testing needs.

Crofford, Mark↗
DOE OSTI2015

Progress and future developments of high current ion source for neutral beam injector in the ASIPP

A high current hot cathode bucket ion source, which based on the US long pulse ion source is developed in Institute of Plasma Physics, Chinese Academy of Sciences. The ion source consists of a bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerator with slit apertures. So far, four ion sources are developed and conditioned on the ion source test bed. 4 MW hydrogen beam with beam energy of 80 keV is extracted. In Aug. 2013, EAST NBI 1 with two ion source installed on the EAST, and achieved H-mode plasma with NBI injection for the first time. In order to achieve stable long pulse operation of high current ion source and negative ion source research, the RF ion source with 200 mm diameter and 120 mm depth driver is designed and developed. The first RF plasma generated with 2 kW power of 1 MHz frequency. More of the RF plasma tests and negative source relative research need to do in the future.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

Dependence of beam emittance on plasma electrode temperature and rf-power, and filter-field tuning with center-gapped rod-filter magnets in J-PARC rf-driven H{sup −} ion source

The prototype rf-driven H{sup −} ion-source with a nickel plated oxygen-free-copper (OFC) plasma chamber, which satisfies the Japan Proton Accelerator Research Complex (J-PARC) 2nd stage requirements of a H{sup −} ion beam current of 60 mA within normalized emittances of 1.5 π mm mrad both horizontally and vertically, a flat top beam duty factor of 1.25% (500 μs × 25 Hz) and a life-time of more than 50 days, was reported at the 3rd international symposium on negative ions, beams, and sources (NIBS2012). The experimental results of the J-PARC ion source with a plasma chamber made of stainless-steel, instead of nickel plated OFC used in the prototype source, are presented in this paper. By comparing these two sources, the following two important results were acquired. One was that the about 20% lower emittance was produced by the rather low plasma electrode (PE) temperature (T{sub PE}) of about 120 °C compared with the typically used T{sub PE} of about 200 °C to maximize the beam current for the plasma with the abundant cesium (Cs). The other was that by using the rod-filter magnets with a gap at each center and tuning the gap-lengths, the filter-field was optimized and the rf-power necessary to produce the J-PARC required H{sup −} ion beam current was reduced typically 18%. The lower rf-power also decreases the emittances.

43 PARTICLE ACCELERATORS↗