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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

A 3-D Navier-Stokes CFD study of turbojet/ramjet nozzle plume interactions at Mach 3.0 and comparison with data

Advanced airbreathing propulsion systems used in Mach 4-6 mission scenarios, usually consist of a single integrated turboramjet or as in this study, a turbojet housed in an upper bay with a separate ramjet housed in a lower bay. As the engines transition from turbojet to ramjet, there is an operational envelope where both engines operate simultaneously. One nozzle concept under consideration has a common nozzle, where the plumes from the turbojet and ramjet interact with one another as they expand to ambient conditions. In this paper, the two plumes interact at the end of a common 2-D cowl, when they both reach an approximate Mach 3.0 condition and then jointly expand to Mach 3.6 at the common nozzle exit plane. At this condition, the turbojet engine operated at a higher NPR than the ramjet, where the turbojet overpowers the ramjet plume, deflecting it approximately 12 degrees downward and in turn the turbojet plume is deflected 6 degrees upward. In the process, shocks were formed at the deflections and a shear layer formed at the confluence of the two jets. This particular case was experimentally tested and the data used to compare with the PARC3D code with k-kl two equation turbulence model. The 2-D and 3-D centerline CFD solutions are in good agreement, but as the CFD solutions approach the outer sidewall, a slight variance occurs. The outer wall boundary layers are thin and do not present much of an interaction, however, where the confluence interaction shocks interact with the thin boundary layer on the outer wall, strong vortices run down each shock causing substantial disturbances in the boundary layer. These disturbances amplify somewhat as they propagate downstream axially from the confluence point. The nozzle coefficient (CFG) is reduced 1/2 percent as a result of this sidewall interaction, from 0.9850 to 0.9807. This three-dimensional reduction is in better agreement with the experimental value of 0.9790.

Chang, Ing↗
DOE OSTI2017

Evolution of Co-existing Long and Short Period Stellar Activity Cycles

The magnetic activity of the Sun becomes stronger and weaker over roughly an 11 year cycle, modulating the radiation and charged particle environment experienced by the Earth as “space weather.” Decades of observations from the Mount Wilson Observatory have revealed that other stars also show regular activity cycles in their Ca ii H+K line emission, and identified two different relationships between the length of the cycle and the rotation rate of the star. Recent observations at higher cadence have allowed the discovery of shorter cycles with periods between 1--3 years. Some of these shorter cycles coexist with longer cycle periods, suggesting that two underlying dynamos can operate simultaneously. We combine these new observations with previous data, and show that the longer and shorter cycle periods agree remarkably well with those expected from an earlier analysis based on the mean activity level and the rotation period. The relative turbulent length scales associated with the two branches of cyclic behavior suggest that a near-surface dynamo may be the dominant mechanism that drives cycles in more active stars, whereas a dynamo operating in deeper layers may dominate in less active stars. However, several examples of equally prominent long and short cycles have been found at all levels of activity of stars younger than 2.3 Gyr. Deviations from the expected cycle periods show no dependence on the depth of the convection zone or on the metallicity. For some stars that exhibit longer cycles, we compute the periods of shorter cycles that might be detected with future high-cadence observations.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1997

SBUV/2 Long-Term Measurements of Solar Spectral Variability

The NOAA-11 SBUV/2 spectral solar data have been corrected for long-term instrument changes to produce a 5.5 year data record during solar cycle 22 (December 1988 - October 1994). Residual drifts in the data at long wavelengths are +/- 1% or less. At 200-205 nm, where solar variations drive stratospheric photochemistry, these data indicate long-term solar changes of 5-7% from the maximum of Cycle 22 in April 1991 through the end of the NOAA-11 data record. Comparisons of NOAA-11 data with UARS SUSIM and SOLSTICE for the period October 1991 - October 1994, when all 3 instruments were operating simultaneously, show that the observed long-term variations in 200-205 nm irradiance agree to within 2%. This result is consistent with predictions from the Mg-2 proxy index. The SBUV/2 instruments represent a valuable resource for long-term solar UV activity studies because of their overlapping data records. In addition to the NOAA-11 data presented here, the NOAA-9 SBUV/2 instrument began taking data in March 1985 and is still operating, providing a complete record of Cycle 22 behavior from a single instrument. Three additional SBUV/2 instruments are scheduled to be launched between 1997 and 2003, which should permit full coverage of solar cycle 23.

DeLand, Matthew T.↗
DOE OSTI2016

Clemson University Wind Turbine Drivetrain Test Facility

In November of 2009, Clemson University was awarded a competitive grant from the U.S. Department of Energy to design, build and operate a facility for full-scale, highly accelerated mechanical testing of next-generation wind turbine drivetrain technologies. The primary goal of the project was to design, construct, commission, and operate a state-of-the-art sustainable facility that permits full-scale highly accelerated testing of advanced drivetrain systems for large wind turbines. The secondary goal was to meet the objectives of the American Recovery and Reinvestment Act of 2009, especially in job creation, and provide a positive impact on economically distressed areas in the United States, and preservation and economic recovery in an expeditious manner. The project was executed according to a managed cooperative agreement with the Department of Energy and was an extraordinary success. The resultant new facility is located in North Charleston, SC, providing easy transportation access by rail, road or ship and operates on an open access model such that it is available to the U.S. Wind Industry for research, analysis, and evaluation activities. The 72 m by 97 m facility features two mechanical dynamometer test bays for evaluating the torque and blade dynamic forces experienced by the rotors of wind turbine drivetrains. The dynamometers are rated at 7.5 MW and 15 MW of low speed shaft power and are configured as independent test areas capable of simultaneous operation. All six degrees of freedom, three linear and three rotational, for blade and rotor dynamics are replicated through the combination of a drive motor, speed reduction gearbox and a controllable hydraulic load application unit (LAU). This new LAU setup readily supports accelerated lifetime mechanical testing and load analysis for the entire drivetrain system of the nacelle and easily simulates a wide variety of realistic operating scenarios in a controlled laboratory environment. The development of these two dynamometer test rigs is the first significant achievement for the project. These test rigs embody a new manner of test due to the system configuration and completely new design with a free floating loading hub in the LAU. This project provided the catalyst for the advancement to this new test rig configuration that has been adopted by every significant wind turbine test rig constructed since the inception of this project. There are currently two different vendors supplying these new systems. Catalyzing this new design is the second major success of the project. With the increased market penetration of wind energy over the past decade, many regions and countries have developed specific electrical grid specifications and performance codes for large wind farms to ensure operational reliability and stability. These grid codes provide requirements for interconnection with the grid during low or high voltage phenomena, typically encountered during and after system fault events. Given the installed infrastructure of the Wind Turbine Drivetrain Testing Facility (WTDTF), a natural expansion of facility capability was to include the necessary equipment for performing fault ride-through evaluations of wind turbines to the Low Voltage Ride Through (LVRT) codes. Once the decision was made to expand the scope of the original grant into fault ride-through testing, it was clear that there are several markets, not just wind, which could benefit from this type of test and that simple fault ride-through testing could be extended into a broader scope of electrical testing capabilities. It was at this point that Clemson University was awarded a second grant to build a 15 MW Hardware-In-the-Loop (HIL) Grid Simulator in order to establish world class electrical testing capabilities to compliment the mechanical testing at the WTDTF. This third significant achievement resulted in the 15 MW HIL Grid Simulator as the corner stone of the Duke Energy eGRID Center and is collocated with the WTDTF in the SCE&G Energy Innovation Center at the new Facility in North Charleston, SC, USA. Before the eGRID was completed, it was recognized that the ability to test solar farm equipment was but a small step away thru the addition of enhanced equipment to provide for DC testing. In yet another expansion/success, a 2.5 MW rectifier system was designed and implemented by Clemson staff to enhance the Center’s capabilities. The program required over 250,000 man-hours of on-site construction labor reworking the brownfield facility on the former Navy Base, clearly satisfying one of the major goals of the Reinvestment Act. This was done while winning numerous awards for design and construction of the facility, including the Top US Project for 2014 from the Trade Journal Engineering News Record. The project was a major collaborative developmental activity managed by Clemson University staff that involved the DOE and many partners and organizations.

17 WIND ENERGY↗
NASA NTRS2016

The Atacama Cosmology Telescope: The Polarization-Sensitive ACTPol Instrument

The Atacama Cosmology Telescope (ACT) makes high angular resolution measurements of anisotropies in the Cosmic Microwave Background (CMB) at millimeter wavelengths. We describe ACTPol, an upgraded receiver for ACT, which uses feedhorn-coupled, polarization-sensitive detector arrays, a 3deg field of view, 100 mK cryogenics with continuous cooling, and meta material antireflection coatings. ACTPol comprises three arrays with separate cryogenic optics: two arrays at a central frequency of 148 GHz and one array operating simultaneously at both 97 GHz and 148 GHz. The combined instrument sensitivity, angular resolution, and sky coverage are optimized for measuring angular power spectra, clusters via the thermal Sunyaev-Zel'dovich (SZ) and kinetic SZ signals, and CMB lensing due to large-scale structure. The receiver was commissioned with its first 148 GHz array in 2013, observed with both 148 GHz arrays in 2014, and has recently completed its first full season of operations with the full suite of three arrays. This paper provides an overview of the design and initial performance of the receiver and related systems.

Telescope↗
NASA NTRS2004

Optoelectronic Sensor System for Guidance in Docking

The Video Guidance Sensor (VGS) system is an optoelectronic sensor that provides automated guidance between two vehicles. In the original intended application, the two vehicles would be spacecraft docking together, but the basic principles of design and operation of the sensor are applicable to aircraft, robots, vehicles, or other objects that may be required to be aligned for docking, assembly, resupply, or precise separation. The system includes a sensor head containing a monochrome charge-coupled- device video camera and pulsed laser diodes mounted on the tracking vehicle, and passive reflective targets on the tracked vehicle. The lasers illuminate the targets, and the resulting video images of the targets are digitized. Then, from the positions of the digitized target images and known geometric relationships among the targets, the relative position and orientation of the vehicles are computed. As described thus far, the VGS system is based on the same principles as those of the system described in "Improved Video Sensor System for Guidance in Docking" (MFS-31150), NASA Tech Briefs, Vol. 21, No. 4 (April 1997), page 9a. However, the two systems differ in the details of design and operation. The VGS system is designed to operate with the target completely visible within a relative-azimuth range of +/-10.5deg and a relative-elevation range of +/-8deg. The VGS acquires and tracks the target within that field of view at any distance from 1.0 to 110 m and at any relative roll, pitch, and/or yaw angle within +/-10deg. The VGS produces sets of distance and relative-orientation data at a repetition rate of 5 Hz. The software of this system also accommodates the simultaneous operation of two sensors for redundancy

Howard, Richard T.↗
NASA NTRS1992

Research opportunities with the Centrifuge Facility

The Centrifuge Facility on Space Station Freedom will consist of a 2.5-meter diameter Centrifuge accommodating two concentric rings of habitats and providing variable g-forces between 0.01 g and 2.0 g; modular habitats providing housing and lifesupport for rats, mice, and plants; a habitat holding system providing power, water, airflow and other utilities to several modular habitats; and a life sciences glovebox, an isolated work volume accommodating simultaneous operations by at least two scientists and providing lighting, airflow, video and data access, and other experiment support functions. The centrifuge facility will enable long-duration animal and plant microgravity research not previously possible in the NASA flight research program. It will offer unprecedented opportunities for use of on-board 1-g control populations and statistically significant numbers of specimens. On orbit 1-g controls will allow separation of the effects of microgravity from other environmental factors. Its selectable-g and simultaneous multiple-g capabilities will enable studies of gravitational thresholds, the use of artificial gravity as a countermeasure to the effects of microgravity, and ready simulation of Lunar and Martian gravities.

Funk, Glenn A.↗
DOE OSTI2020

Dual wavelength operation of the GaSb-based Y-branch distributed Bragg reflector lasers near 2.1 μ m

The GaSb-based diode lasers operating simultaneously at two wavelengths near 2.1 μm have been designed and fabricated. The Y-branch devices used the 6th order distributed Bragg reflectors (DBR) to provide spectrally selective feedback. The laser active region contained two asymmetric quantum wells with allowed optical transitions between two lowest electron (e1 and e2) and top hole (hh1) subbands. The laser emission lines loosely matched the e1-hh1 and e2-hh1 optical transitions with separation corresponding to ~3.1 THz. Finally, the 10 μm wide deeply etched straight ridge DBR lasers demonstrated stable single mode operation with more than 50 mW of output power.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2013

Beyond hard x-ray photoelectron spectroscopy: Simultaneous combination with x-ray diffraction

Hard x-ray photoelectron spectroscopy (HAXPES) is a powerful and novel emerging technique for the nondestructive determination of electronic properties and chemical composition of bulk, buried interfaces and surfaces. It benefits from the exceptionally large escape depth of high kinetic energy photoelectrons, increasing the information depth up to several tens of nanometers. Complementing HAXPES with an atomic structure sensitive technique (such as x-ray diffraction) opens a new research field with major applications for materials science. At SpLine, the Spanish CRG beamline at the European Synchrotron Radiation Facility, we have developed a novel experimental set-up that combines HAXPES and x-ray diffraction (x-ray reflectivity, surface x-ray diffraction, grazing incidence x-ray diffraction, and reciprocal space maps). Both techniques can be operated simultaneously on the same sample and using the same excitation source. The set-up includes a robust 2S + 3D diffractometer hosting a ultrahigh vacuum chamber equipped with a unique photoelectron spectrometer (few eV < electron kinetic energy < 15 keV), x-ray tube (Mg/Ti), 15 keV electron gun, and auxiliary standard surface facilities (molecular beam epitaxy evaporator, ion gun, low energy electron diffraction, sample heating/cooling system, leak valves, load-lock sample transfer, etc.). This end-station offers the unique possibility of performing simultaneous HAXPES + x-ray diffraction studies. In the present work, we describe the experimental set-up together with two experimental examples that emphasize its outstanding capabilities: (i) nondestructive characterization of the Si/Ge and HfO{sub 2}/SiO{sub 2} interfaces on Ge-based CMOS devices, and (ii) strain study on La{sub 0.7}Ca{sub 0.3}MnO{sub 3} ultrathin films grown on SrTiO{sub 3}(001) substrate.

36 MATERIALS SCIENCE↗
NASA NTRS1972

The 20 and 30 GHz communications system for the ATS-F millimeter wave experiment.

The first space communications system operating at millimeter wavelengths is planned for the sixth Applications Technology Satellite (ATS-F), scheduled for launch in May of 1973. The ATS-F experiment is designed to provide engineering data on wideband space-to-earth transmissions at 20 and 30 GHz as a function of meteorological conditions and modulation techniques. The system design for both the spacecraft and ground station portions of the experiment is presented, and the unique design characteristics of these relatively new and unexplored frequency bands are emphasized. The experiment is designed to provide wideband 1440-MHz propagation links and 40-Megabit communications links with simultaneous operation at 20, 30, and 4 GHz for link comparisons.

Ippolito, L. J.↗
NASA NTRS2004

New Acoustic Arena Qualified at NASA Glenn's Aero-Acoustic Propulsion Laboratory

A new acoustic arena has been qualified in the Aero-Acoustic Propulsion Laboratory (AAPL) at the NASA Glenn Research Center. This arena is outfitted specifically for conducting fan noise research with the Advanced Noise Control Fan (ANCF) test rig. It features moveable walls with large acoustic wedges (2 by 2 by 1 ft) that create an acoustic environment usable at frequencies as low as 250 Hz. The arena currently uses two dedicated microphone arrays to acquire fan inlet and exhaust far-field acoustic data. It was used successfully in fiscal year 2003 to complete three ANCF tests. It also allowed Glenn to improve the operational efficiency of the four test rigs at AAPL and provided greater flexibility to schedule testing. There were a number of technical challenges to overcome in bringing the new arena to fruition. The foremost challenge was conflicting acoustic requirements of four different rigs. It was simply impossible to construct a static arena anywhere in the facility without intolerably compromising the acoustic test environment of at least one of the test rigs. This problem was overcome by making the wall sections of the new arena movable. Thus, the arena can be reconfigured to meet the operational requirements of any particular rig under test. Other design challenges that were encountered and overcome included structural loads of the large wedges, personnel access requirements, equipment maintenance requirements, and typical time and budget constraints. The new acoustic arena improves operations at the AAPL facility in several significant ways. First, it improves productivity by allowing multiple rigs to operate simultaneously. Second, it improves research data quality by providing a unique test area within the facility that is optimal for conducting fan noise research. Lastly, it reduces labor and equipment costs by eliminating the periodic need to transport the ANCF into and out of the primary AAPL acoustic arena. The investment to design, fabricate, and install the new compact arena in fiscal year 2002 has paid dividends in fiscal year 2003 and will for many years to come. It has provided a dedicated, high-quality acoustic arena to support low-speed fan testing for ANCF while minimizing scheduling impacts and improving operational productivity in the AAPL facility.

Wnuk, Stephen P.↗
NASA NTRS2018

UV Capabilities of the CETUS Multi-Object Spectrometer (MOS) and NUV/FUV Camera

The Cosmic Evolution Through UV Spectroscopy (CETUS) concept enables parallel observations by the UV multiobject spectrometer (MOS) and near-UV/far-UV camera which operate simultaneously but independently with their separate field of views. The near-UV MOS can target up to 100 objects at a time without confusion with nearby sources or background zodiacal light. This multiplexing will allow over 100,000 galaxies to be observed over a typical mission lifetime. The MOS includes a next-generation micro-shutter array (NGMSA), an efficient aspheric Offner-like spectrometer design with a convex grating, and nanotube light traps for suppressing unwanted wavelengths. The NUV/FUV Camera has the capability to image in a range of sub-bands from 115-400 nm at the same time the MOS is operating at 180-350 nm. The UV camera has a similar Offner-like relay, selectable filters, and two separate detectors to optimize observing in either the far-UV (115-175 nm) or the near-UV (180-400 nm) utilizing a CsI Micro-Channel Plate detector (MCP) and a CCD respectively.

The Cosmic Evolution Through UV Spectroscopy (CETU↗
DOE OSTI2023

Image Characterization of Reactions Generated by an Aeroengine Micromixing Injector for Lean Direct Injection of Hydrogen and Hydrogen/Natural Gas Blend

An aeroengine micromixing injector, originally designed for lean direct injection of jet fuel, was adapted to work with hydrogen, natural gas, and any blend in between. The ultimate goal of the design was to achieve low NOx emissions when operated on pure hydrogen; to better characterize its performance, flame imaging diagnostics was implemented. Three types of cameras mounted parallel to the injector base and pointing towards the quartz combustor cylinder with the same angle were operated simultaneously: Nikon D90, Dynacolor FB-N9-U, and Phantom v7.1, to capture the visible spectrum, OH* chemiluminescence, and dynamic behavior of the flames, respectively. The current work also includes the overlapping of visible spectrum and OH* chemiluminescence, as an effort to qualitatively define the heat release over the flame area, i.e., UV over visible domain. Additionally, a z-type schlieren configuration was employed to reinforce the presence of some small-scale details occurring near the injector outlet ports. Using the airbox pressure drop, preheat temperature, fuel composition and flame temperature as the factors of study, a Box Behnken model was designed yielding into a 16-points matrix for the operability region, at atmospheric pressure. The main responses were extracted from the OH* images, because of its correlation with the flame heat release, these being the flame area and its average brightness, the heat release area and its center of gravity and leading edge. To assess the importance of the main factors and their interactions, an analysis of variance (ANOVA) was performed for each response, considering as significant each contributor with a p-value below 0.05. For these five responses it was found that all four main factors need to be included into the model (most of them because its own significance, others to ensure the model hierarchy), as well as some common interactions as the preheat and flame temperatures or pressure drop and fuel composition, and quadratic terms from fuel composition or flame temperature. Three of the five models presented R2 and coefficient of variance (C.V.) indicators around 0.97 and 5%, respectively; the leading edge ANOVA yielded into R2=0.78 and C.V.=18.88%; and the heat release area showed R2=0.91 and C.V.=24.13%. Lastly, the confinement ratio effect of the combustor over the flame structure was quantified, for three different conditions: the original 80 mm inner diameter and 200 mm length cylinder was compared against a shorter 150 mm tube (same inner diameter) and a narrower 47 mm inner diameter one (same 200 mm length). The length had a smaller effect than the inner diameter, even though both factors were not strong enough to make a significant deviation on most of the flame parameters: the difference was within the repeatability margin of error for the brightness, flame area, and center of gravity and leading edge of the heat release area.

Imaging diagnostics, flame characterization, OH* c↗
DOE OSTI2013

Broadband carbon monoxide laser system operating in the wavelength range of 2.5 - 8.3 {mu}m

A two-cascade frequency conversion of CO-laser radiation is demonstrated in a single sample of a nonlinear ZnGeP{sub 2} crystal. The crystal is pumped by a repetitively pulsed cryogenic lowpressure CO laser operating on {approx}150 vibration - rotational transitions in the wavelength range 5.0 - 7.5 {mu}m, which corresponds to the frequency range of a half octave. In the first conversion cascade, generation of second harmonic and sum frequencies of various pairs of CO-laser radiation give {approx}350 emission lines in the wavelength range 2.5 - 3.7 {mu}m. In the second cascade, by mixing the radiation converted in the first cascade with the residual radiation of the CO laser we have obtained {approx}90 lines in the range 4.3 - 5.0 {mu}m and more than 80 lines in the range 7.5 - 8.3 {mu}m. Thus, using a single sample of the nonlinear ZnGeP{sub 2} crystal pumped by the radiation of a single CO laser we have produced a source of broadband (more than one and a half octaves) laser radiation, simultaneously operating at {approx}670 lines in the wavelength range 2.5 - 8.3 {mu}m. (lasers)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2019

In-Flight Line-Of-Sight Pointing Performance for the GOES-16 and GOES-17 Spacecraft

The Geostationary Operational Environmental Satellite-R program (GOES-R) has launched two of the next generation geostationary weather satellites, both of which are now fully operational. GOES-16 launched in November 2016, and GOES-17 launched in March 2017. In this paper, we present the pointing and pointing stability results of the two spacecraft, with specific focus on aspects of the design related to mitigating jitter. The flight instrument suite includes 6 seismic accelerometers sampled at approximately 2 kilohertz, allowing in-flight verification of pointing stability and comparison back to simulation predictions. This paper compares the observed flight results with the simulation predictions for acceleration and shock response spectrum (SRS) for various operational scenarios and instrument observation modes. Passive isolation of both the reaction wheels and the payload deck have proved to be effective in reducing jitter responses. Active Vibration Damping (AVD) of flexible-body modes attenuates the low frequency motion of the vehicle appendages, improving the low-frequency pointing performance. Knowledge of the instrument scan mirror motion is fed forward to the reaction wheel control, reducing disturbances on the spacecraft bus. Attitude knowledge and rate data are provided to the primary Earth-observing instrument with an accuracy defined by the Integrated Rate Error (IRE) requirements. The data are used to adjust instrument scanning. As we show in this paper, the in-flight performance of the GN&C (Guidance, Navigation and Control) design provides the necessary capabilities to achieve the demanding GOES-R mission objectives while its robustness enabled the simultaneous operation of the Advanced Baseline Imager (ABI) prime and redundant cryocoolers (CCs) to resolve an in-flight cooling anomaly on GOES-17.

Line-of-Sight↗
NASA NTRS1994

Observations of water vapor by ground-based microwave radiometers and Raman lidar

In November to December 1991, a substantial number of remote sensors and in situ instruments were operated together in Coffeyville, Kansas, during the climate experiment First ISCCP Regional Experiment Phase 2 (FIRE 2). Includede in the suite of instruments were (1) the NOAA Environmental Technology Laboratory (ETL) three-channel microwave radiometer, (2) the NASA GSFC Raman lidar, (3) ETL radio acoustic sounding system (RASS), and (4) frequent, research-quality radiosondes. The Raman lidar operated only at night and the focus of this portion of the experiment concentrated on clear conditions. The lidar data, together with frequent radiosondes and measurements of temperature profiles (every 15 min) by RASS allowed profiles of temperature and absolute humidity to be estimated every minute. We compared 20 min measurements of brightness temperature (T(sub b) with calculations of T(sub b) that were based on the Liebe and Layton (1987) and Liebe et al. (1993) microwave propagation models, as well as the Waters (1976) model. The comparisons showed the best agreement at 20.6 GHz with the Waters model, with the Liebe et al. (1993) model being best at 31.65 GHz. The results at 90 GHz gave about equal success with the Liebe and Layton (1987) and Liebe et al. (1993) models. Comparisons of precipitable water vapor derived independently from the two instruments also showed excellent agreement, even for averages as short as 2 min. The rms difference between Raman and radiometric determinations of precipitable water vapor was 0.03 cm which is roughly 2%. The experiments clearly demonstrate the potential of simultaneous operation of radiometers and Raman lidars for fundamental physical studies of water vapor.

Han, Yong↗
DOE OSTI2018

Experimental high gradient testing of a 17.1 GHz photonic band-gap accelerator structure

We report the design, fabrication and high gradient testing of a 17.1 GHz Photonic Band Gap accelerator structure. Photonic band-gap (PBG) structures are promising candidates for electron accelerators capable of high-gradient operation because they have the inherent damping of high order modes required to avoid beam breakup instabilities. The 17.1 GHz PBG structure tested was a single cell structure composed of a triangular array of round copper rods of radius 1.45 mm spaced by 8.05 mm. The test assembly consisted of the test PBG cell located between conventional (pillbox) input and output cells, with input power of up to 4 MW from a klystron supplied via a TM01 mode launcher. Breakdown at high gradient was observed by diagnostics including reflected power, downstream and upstream current monitors and visible light emission. The testing procedure was first benchmarked with a conventional disc-loaded waveguide structure, which reached a gradient of 87 MV/m at a breakdown probability of 1.19 × 10^-1 per pulse per meter. The PBG structure was tested with 100 ns pulses at power levels of less than 90 MV/m in order to limit the surface temperature rise to 120 K. The PBG structure reached up to 89 MV/m at a breakdown probability of 1.09×10^-1 per pulse per meter. These test results show that a PBG structure can simultaneously operate at high gradients and low breakdown probability, while also providing wakefield damping.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Data Analyst - A Device for Continuous Repeating Real-Time Assay of HPGe, CZT, or Scintillation Gamma Spectra - 18574

There are many situations where a continuous repeating series of quantitative gamma spectral assays is desirable. These include measurements of fluid going through a pipe, of items on a conveyor passing under a detector, a detector aimed at the ground on a moving platform, or a detector in free air as a plume of radioactivity drifts by. While Canberra and many others have built and deployed many of these devices, they have all been custom built for that particular application, and rather expensive. The Data Analyst [DA] is a general purpose device that is designed to fulfill many of these applications without modification, but can be fairly-easily modified if needed. The DA is a small [12 x 18 x 5 cm], low-power [3 W] box that accepts the input from external MCAs, controls the acquisition cycle, analyzes the results, and transmits them to the outside world when needed. The detector-MCAs supported are HPGe with Lynx MCA, NaI or CeBr or LaBr with Osprey MCA, and CZT or CsI with internal MCAs. The DA internal software used for analysis is the full standard Genie analysis software, which is very widely used and well accepted in the industry. This allows exported spectral files to be reviewed and confirmed by Experts, and reanalyzed if needed. The DA hardware is totally autonomous. As soon as power is applied, it starts the pre-programmed sequences of acquisition and analysis. Multiple analysis sequences [called Workflows] can be in operation simultaneously, e.g. with different count times and different nuclide libraries. Only the detector with MCA, and the DA are required in the field. A PC can be connected to the DA locally or remotely via WiFi, USB, or Ethernet. The PC is needed to setup the DA, and to readout the results. The DA also supports [with application-specific programming] external Inputs/Outputs either for recording with the analysis results or for use in the computation of the result, e.g. temperature, flow rate, pressure, ... ]. The DA also has an internal GPS receiver with external antenna. Applications of the DA that are discussed include stack gas effluent activity where a portion of the effluent stream was extracted to flow through a shield with a HPGe detector and Lynx MCA, and measurement of reactor coolant activity where a shielded CZT detector and MCA were aimed at various sections of reactor primary coolant during a maintenance outage. Potential other applications are also described. (author)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗