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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

The Miniature Radio Frequency Instruments (Mini-RF) Global Observations of Earth's Moon

Radar provides a unique means to analyze the surface and subsurface physical properties of geologic deposits, including their wavelength-scale roughness, the relative depth of the deposits, and some limited compositional information. The NASA Lunar Reconnaissance Orbiter's (LRO) Miniature Radio Frequency (Mini-RF) instrument has enabled these analyses on the Moon at a global scale. Mini-RF has accumulated 67% coverage of the lunar surface in S-band (12.6 cm) radar with a resolution of 30 m/pixel. Here we present new Mini-RF global orthorectified uncontrolled S-band maps of the Moon and use them for analysis of lunar surface physical properties. Reported here are readily apparent global- and regional-scale differences in lunar surface physical properties that suggest three distinct terranes, namely: a (1) Nearside Radar Dark Region; (2) Orientale basin and continuous ejecta; and the (3) Highlands Radar Bright Region. Integrating these observations with new data from LRO's Diviner Radiometer rock abundance maps, as well Clementine and Lunar Prospector derived compositional values show multiple distinct lunar surface terranes and sub-terranes based upon both physical and compositional surface properties. Previous geochemical investigations of the Moon suggested its crust is best divided into three to four basic crustal provinces or terranes (Feldspathic Highlands Terrane (-An and -Outer), Procellarum KREEP Terrane, and South Pole Aitken Terrane) that are distinct from one another. However, integration of these geochemical data sets with new geophysical data sets allows us to refine these terranes. The result shows a more complex view of these same crustal provinces and provides valuable scientific and hazard perspectives for future targeted human and robotic exploration.

Radar observations↗
NASA NTRS2018

Lunar Relay Coverage Analysis for RF and Optical Links

This paper describes our effort in searching different lunar relay architectures and assessing their coverage performance and other pros and cons for RF and optical links. Regarding RF links, we considered three notional lunar relay architectures, all communicating with the three sites of the Deep Space Network (DSN): Goldstone, California; Canberra, Australia; and Madrid, Spain: 1) A constellation of three relay orbiters: two at the Polar frozen elliptical orbits, and one at an equatorial circular orbit. 2) One relay orbiter in a 74-day Lissajous orbit at Earth-Moon Lagrange Point L2. 3) One relay orbiter in a 14-day Lunar distance retrograde orbit. Regarding optical link, we considered a notional multi-hop relay architecture that consists of one relay orbiter in a 74-day Lissajous orbit at Earth-Moon L2 (as in architecture #2 in the RF case), three Near-Earth relay satellites in geosynchronous orbit at longitudes 187° E, 110° E, and 347° E, and three ground stations at White Sands (US), Guam (US), and Tenerife (Spain). We introduce the additional constraints of Sun-“Earth”Probe (SEP) angle for return links, and Sun-Probe-“Earth” (SPE) angle for forward links. SPE and SPE angles determine the amount of sunlight (noise) that goes into the detector of the telescope, thus affecting the capacity of an optical link.

Lee, Charles↗
NASA NTRS2020

CubeSat Array for Detection of RF Emissions from Exoplanets using Inter-Satellite Optical Communicators

We are presenting a CubeSat mission concept wherein a large number of small spacecraft furnished with Ultra-Long Wavelength (ULW) observation antennas is to be implemented to synthesize a large aperture for detecting ULW emissions from selected exoplanets. The CubeSat Array for the Detection of RF Emissions from Exoplanets (CADRE) concept involves the placement of a swarm arrangement of CubeSats into small amplitude Lissajous orbits around the Earth-Moon L2 point. In addition to the ULW receivers, each CADRE CubeSat will be furnished with a novel omnidirectional optical communicator which should allow data sharing at gigabit per second data rates. In this paper we discuss the science goals, potential architecture and key technical challenges of an eventual CADRE implementation. We present the estimated interferometer specifications needed to detect Exoplanet RF emissions, CubeSat orbits and formations as well as CubeSat design considerations. Special focus is placed on the design of the mission-enabling inter-CubeSat optical cross link which allows for fast sharing of the detected RF signals for subsequent correlation.

Bentum, Mark↗
NASA NTRSDate not supplied

Design and Analysis of Convolutional Neural Network for RF Signal Modulation Classification for In-Orbit Deployment

To effectively transmit data to and from satellites requires a complex and robust RF communication system. Commonly, several different types of signal modulations may be required to maximize satellite efficiency depending on a variety of unexpected channel impairments. We propose a neural network algorithm capable of learning these RF signal modulations using a supervised learning technique designed for low power, high-efficiency in-orbit deployment. The work presented demonstrates a convolutional neural network (CNN) capable of learning and recognizing a set of modulation schemes commonly used to transmit RF information. We are capable of recognizing the modulation scheme from the I and Q data channels directly, with no preprocessing or data conversion required other than breaking the incoming signal into a set of uniform normalized samples. We perform a network design and size analysis, showing that reasonably high accuracy can be obtained using networks with a relatively low number of trainable parameters. Given that a user of a system such as this may wish to receive a signal using a modulation scheme that the network has not previously learned, we demonstrate that transfer learning can learn new modulation schemes by retraining only the fully connected layers in the CNN. Thus, this type of network would excel in outer space deployment using high-efficiency transfer learning hardware. Modulation recognition can be performed through rapid feedforward computation, and the CNN training process is significantly simplified when learning new modulations is required.

CNN↗
DOE OSTI2013

Mechanical Analysis of the 400 MHz RF-Dipole Crabbing Cavity Prototype for LHC High Luminosity Upgrade

The proposed LHC high luminosity upgrade requires two crabbing systems in increasing the peak luminosity, operating both vertically and horizontally at two interaction points of IP1 and IP5. The required system has tight dimensional constraints and needs to achieve higher operational gradients. A proof-of-principle 400 MHz crabbing cavity design has been successfully tested and has proven to be an ideal candidate for the crabbing system. The cylindrical proof-of-principle rf-dipole design has been adapted in to a square shaped design to further meet the dimensional requirements. The new rf-dipole design has been optimized in meeting the requirements in rf-properties, higher order mode damping, and multipole components. A crabbing system in a cryomodule is expected to be tested on the SPS beam line prior to the test at LHC. The new prototype is required to achieve the mechanical and thermal specifications of the SPS test followed by the test at LHC. This paper discusses the detailed mechanical and thermal analysis in minimizing Lorentz force detuning and sensitivity to liquid He pressure fluctuations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2014

RF-driven ion source with a back-streaming electron dump

A novel ion source is described having an improved lifetime. The ion source, in one embodiment, is a proton source, including an external RF antenna mounted to an RF window. To prevent backstreaming electrons formed in the beam column from striking the RF window, a back streaming electron dump is provided, which in one embodiment is formed of a cylindrical tube, open at one end to the ion source chamber and capped at its other end by a metal plug. The plug, maintained at the same electrical potential as the source, captures these backstreaming electrons, and thus prevents localized heating of the window, which due to said heating, might otherwise cause window damage.

47 OTHER INSTRUMENTATION↗
DOE OSTI2014

RF Input Power Couplers for High Current SRF Applications

High current SRF technology is being explored in present day accelerator science. The bERLinPro project is presently being built at HZB to address the challenges involved in high current SRF machines with the goal of generating and accelerating a 100 mA electron beam to 50 MeV in continuous wave (cw) mode at 1.3 GHz. One of the main challenges in this project is that of handling the high input RF power required for the photo-injector as well as booster cavities where there is no energy recovery process. A high power co-axial input power coupler is being developed to be used for the photo-injector and booster cavities at the nominal beam current. The coupler is based on the KEK–cERL design and has been modified to minimise the penetration of the coupler tip in the beam pipe without compromising on beam-power coupling (Qext ~105). Herein we report on the RF design of the high power (115 kW per coupler, dual couplers per cavity) bERLinPro (BP) coupler along with initial results on thermal calculations. We summarise the RF conditioning of the TTF-III couplers (modified for cw operation) performed in the past at BESSY/HZB. A similar conditioning is envisaged in the near future for the low current SRF photo-injector and the bERLinPro main linac cryomodule.

Khan, V. F.↗
DOE OSTI2015

Commissioning and Early Operation Experience of the NSLS-II Storage Ring RF System

The National Synchrotron Light Source II (NSLS-II) is a 3 GeV electron X-ray user facility commissioned in 2014. The storage ring RF system, essential for replenishing energy loss per turn of the electrons, consists of digital low level RF controllers, 310 kW CW klystron transmitters, CESR-B type superconducting cavities, as well as a supporting cryogenic system. Here we will report on RF commissioning and early operation experience of the system for beam current up to 200mA.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Multiphysics Analysis of Frequency Detuning in Superconducting RF Cavities for Proton Particle Accelerators

Multiphysics analyses for superconducting cavities are essential in the course of cavity design to meet stringent requirements on cavity frequency detuning. Superconducting RF cavities are the core accelerating elements in modern particle accelerators whether it is proton or electron machine, as they offer extremely high quality factors thus reducing the RF losses per cavity. However, the superior quality factor comes with the challenge of controlling the resonance frequency of the cavity within few tens of hertz bandwidth. In this paper, we investigate how the multiphysics analysis plays a major role in proactively minimizing sources of frequency detuning, specifically; microphonics and Lorentz Force Detuning (LFD) in the stage of RF design of the cavity and mechanical design of the niobium shell and the helium vessel.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Transient Beam Loading Effects in Gas-filled RF Cavities for a Muon Collider

A gas-filled RF cavity can be an effective solution for the development of a compact muon ionization cooling channel. One possible problem expected in this type of cavity is the dissipation of significant RF power through the beam-induced plasmas accumulated inside the cavity (plasma loading). In addition, for the higher muon beam intensity, the effects of the beam itself on the cavity accelerating mode are non-negligible (beam loading). These beam- cavity interactions induce a transient phase which may be very harmful to the beam quality [1]. In this study, we estimate the transient voltage in a gas-filled RF cavity with both the plasma and conventional beam loading and discuss their compensation methods.

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

OBSERVATION OF REPETITION-RATE DEPENDANT EMISSION FROM AN UN-GATED THERMIONIC CATHODE RF GUN

Recent work at Fermilab in collaboration with the Advanced Photon Source and members of other national labs, designed an experiment to study the relationship between the RF repetition rate and the average current per RF pulse. While existing models anticipate a direct relationship between these two parameters we observed an inverse relationship. We believe this is a result of damage to the barium coating on the cathode surface caused by a change in back-bombardment power that is unaccounted for in the existing theories. These observations shed new light on the challenges and fundamental limitations associated with scaling an ungated thermionic cathode RF gun to high average current machines.

Edelen, J. P.↗
DOE OSTI2016

BICMOS power detector for pulsed Rf power amplifiers

A BiCMOS power detector for pulsed radio-frequency power amplifiers is proposed. Given the pulse waveform and a fraction of the power amplifier's input or output signal, the detector utilizes a low-frequency feedback loop to perform a successive approximation of the amplitude of the input signal. Upon completion of the successive approximation, the detector returns 9-bits representing the amplitude of the RF input signal. Using the pulse waveform from the power amplifier, the detector can dynamically adjust the rate of the binary search operation in order to return the updated amplitude information of the RF input signal at least every 1ms. The detector can handle pulse waveform frequencies from 50kHz to 10MHz with duty cycles in the range of 5- 50% and peak power levels of -10 to 10dBm. The signal amplitude measurement can be converted to a peak power measurement accurate to within ±0.6dB of the input RF power.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2015

Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade

The proposed Advanced Photon Source (APS) multibend achromat (MBA) lattice includes a passive bunchlengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.

Berenc, Tim↗
DOE OSTI2018

SLED-II: A New Method of RF Pulse Compression

In the SLED 1 method of RF pulse compression, two high Q resonators store energy from an RF source for a relatively long time interval (typically 3 to 5 J.1sec). Triggered by a reversal in RF phase, this stored energy is then released during a much shorter interval equal to the filling time of the accelerating structure. A peak power gain on the order of three and a compression efficiency on the order of 60% are typically attained. The shape of the output pulse is, however, a sharply decaying expo- nential. In SLED-II the two cavities are replaced by two lengths of resonant line, forming a Resonant Line SLED (RELS) and resulting in a flat output pulse. Therefore, RELS stages can be cascaded to give a greater peak power gain. Using two stages, a peak power gain greater than ten can be achieved with a reasonable compression efficiency. Unlike the BEC,2 the RELS compression fac- tor per stage is not limited to two, albeit at the expense of intrinsic efficiency. Like the BEC, it uses long lines rather than short cavities.

Farkas, Z.↗
DOE OSTI2018

Insight into bulk niobium superconducting RF cavities performances by tunneling spectroscopy

Point contact tunneling (PCT) spectroscopy measurements are reported over wide areas of cm-sized cut outs from niobium superconducting RF cavities. A comparison is made between a high-quality, conventionally processed (CP) cavity with a high field Q drop for acceleration field E $>$ 20 MV/m and a nitrogen doped (N-doped) cavity that exhibits an increasing Q up to fields approaching 15 MV/m. The CP cavity displays hot spot regions at high RF fields where Q-drop occurs as well as unaffected regions (cold spots). PCT data on cold spots reveals a near ideal BCS density of states (DOS) with gap parameters, $\Delta$ as high as 1.62 meV, that are among the highest values ever reported for Nb. Hot spot regions exhibit a wide distribution of gap values down to $\Delta \sim$ 1.0 meV and DOS broadening characterized by a relatively large value of pair-breaking rate, $\Gamma$, indicating surface regions of significantly reduced superconductivity. In addition, hot spots commonly exhibit Kondo tunneling peaks indicative of surface magnetic moments attributed to a defective oxide. N-doped cavities reveal a more homoegeneous gap distribution centered at $\Delta \sim$ 1.5 meV and relatively small values of $\Gamma/\Delta$. The absence of regions of significantly reduced superconductivity indicates that the N interstitials are playing an important role in preventing the formation of hydride phases and other macroscopic defects which might otherwise severely affect the local, surface superconductivity that lead to hot spot formation. The N-doped cavities also display a significantly improved surface oxide, i.e., increased thickness and tunnel barrier height, compared to CP cavities. These results help explain the improved performance of N-doped cavities and give insights into the origin of the initial increasing Q with RF amplitude.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Data Acquisition System for RF Cavity Hadron Monitor

As Fermilab pursues intensity frontier physics, the conventional detectors are not up to the challenge of higher radiation exposure. The detectors in the NuMI beamline rely on knowing the beam composition in order to infer properties of the resultant neutrino beam. Anovel gas-filled RF cavity beam detector is proposed that will be simple and radiation robust in high-radiation environments. Charged particles passing through the cavity produce ionized plasma, which changes the permittivity of the gas and modulate the stored RF field in the cavity. The recent preliminary beam result demonstrates the proof of principle of the beam detector. In an effort to acquire a large amount of data for various cavity parameters, an automatic data acquisition(DAQ)system is designed in LabVIEW. The DAQ system utilizes a Real-Time Power meter from Boonton to acquire RF power data from the cavity.

43 PARTICLE ACCELERATORS↗
DOE OSTI2019

Evaluation of low heat conductivity rf cables

New potential applications of superconducting radio-frequency can be envisioned with conduction cooling of the cavities using cryocoolers. In this case, the total heat load to the cryocoolers have to be carefully managed to assure sufficient margin to operate the cavity at an acceptable accelerating gradient. The static and dynamic heat load from rf cables connected to the cavity can be a significant contribution to the total heat load. In this contribution we report the results from measurements of the temperature profile at 1.3 GHz for two low heat conductivity rf cables, as a function of the rf power and with one end of the cable in thermal contact with a liquid helium bath at 4.3 K. A parametric model of the two cables was developed with ANSYS to match the temperature profiles and calculate the heat load at the cold end of the cable.

Cheng, G.↗
DOE OSTI2017

A Compact Superconducting RF Accelerator for Electron Beam and X-ray Irradiation

As commercial and industrial applications of electron beam and x-ray irradiation have developed, new applications have emerged that require very high beam power to create the required radiation field. These new applications require dependable, efficient, high-energy, high-power electron accelerators. Recent developments in Superconducting Radio-Frequency (SRF) technology can now enable accelerators with lower costs and improved performance. Cryogenic heat loads are dramatically reduced through use of new materials and improved component designs. New cooling methods allow the replacement of complex systems requiring cryogenic fluids with simple robust systems with no fluids. New RF sources can greatly reduce the cost of RF power. Each of these developments has been individually proven and an effort is underway at the Illinois Accelerator Research Center at Fermilab to integrate them into the first prototype of an entirely new class of industrial SRF-based accelerators. These accelerators will enable robust, turn-key operation with very high electrical efficiency. The accelerator prototype under design will be capable of 10 MeV beam, CW operation, and 250 kW of electron beam power. These modular systems are small enough to be palletized and transported to the point of use. Their high electrical efficiency mean that portable power generation systems can be enable their use in mobile applications. The goal is a compact, cost-effective, high-power accelerator suitable for many of the applications covered by this conference. Fermilab is actively working to build the prototype. The end-product will be a commercially available, robust, turn-key system for applications requiring reliable electron beam or X-ray irradiation. Keywords: accelerator, applications, conduction-cooling, cryogen-free, industrial, super-conducting RF.

43 PARTICLE ACCELERATORS↗