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Results for “Active Pulse Compression”

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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Electromagnetic ion cyclotron waves stimulated by modest magnetospheric compressions

AMPTE/CCE magnetic field and particle data are used to test the suggestion that increased hot proton temperature anisotropy resulting from convection during magnetospheric compression is responsible for the enhancement in Pc 1 emission via generation of electromagnetic ion cyclotron (EMIC) waves in the dayside outer equatorial magnetosphere. The relative increase in magnetic field is used to gauge the strength of the compression, and an image dipole model is used to estimate the motion of the plasma during compression. Proton data are used to analyze the evolution of the proton distribution and the corresponding changes in EMIC wave activity expected during the compression. It is suggested that enhancements in dynamic pressure pump the energetic proton distributions in the outer magnetosphere, driving EMIC waves. Waves are expected to be generated most readily close to the magnetopause, and transient pressure pulses may be associated with bursts of EMIC waves, which would be observed on the ground in association with ionospheric transient signatures.

Anderson, B. J.↗
NASA NTRS2012

NASA's Robotic Lunar Lander Development Project

Since early 2005, NASA's Robotic Lunar Lander Development (RLLD) office at NASA MSFC, in partnership with the Applied Physics Laboratory (APL), has developed mission concepts and preformed risk-reduction activities to address planetary science and exploration objectives uniquely met with landed missions. The RLLD team developed several concepts for lunar human-exploration precursor missions to demonstrate precision landing and in-situ resource utilization, a multi-node lunar geophysical network mission, either as a stand-alone mission, or as part of the International Lunar Network (ILN), a Lunar Polar Volatiles Explorer and a Mercury lander mission for the Planetary Science decadal survey, and an asteroid rendezvous and landing mission for the Exploration Precursor Robotics Mission (xPRM) office. The RLLD team has conducted an extensive number of risk-reduction activities in areas common to all lander concepts, including thruster testing, propulsion thermal control demonstration, composite deck design and fabrication, and landing leg stability and vibration. In parallel, the team has developed two robotic lander testbeds providing closed-loop, autonomous hover and descent activities for integration and testing of flight-like components and algorithms. A compressed-air test article had its first flight in September 2009 and completed over 150 successful flights. This small test article (107 kg dry/146 kg wet) uses a central throttleable thruster to offset gravity, plus 3 descent thrusters (~37lbf ea) and 6 attitude-control thrusters (~12lbf ea) to emulate the flight system with pulsed operation over approximately 10s of flight time. The test article uses carbon composite honeycomb decks, custom avionics (COTS components assembled in-house), and custom flight and ground software. A larger (206 kg dry/322 kg wet), hydrogen peroxide-propelled vehicle began flight tests in spring 2011 and fly over 30 successful flights to a maximum altitude of 30m. The monoprop testbed also uses a central gravity-canceling thruster and 3 descent thrusters, but has 12 attitude-control thrusters and a maximum flight time of over a minute. The testbed uses aluminum ortho-grid decks, an LN200-1 IMU, Roke Manor Radar Altimeter, Illunis optical cameras, Novatel Pro-Pak GPS truth data system, Pressure transducers & thermocouples for housekeeping, "In-Control" ground system software, and the core Flight Executive (cFE) modular software environment. The peroxide lander testbed is able to accept other sensors and algorithms for testing, both from within NASA and from other customers. Through these activities, the RLLD team has significantly reduced technical risks for all small and medium class robotic landers for the Moon and other airless planetary bodies.

Cohen, Barbara A.↗
NASA NTRS2018

Gradient Field Imploding Liner Fusion Propulsion System: NASA Innovative Advanced Concepts Phase I Final Report

The advancement of human deep space exploration requires the continued development of energetic in-space propulsion systems, from current chemical engines to nuclear thermal rockets to future high energy concepts such as nuclear fusion. As NASA embarks on a program to develop near-term nuclear thermal propulsion, this NASA Innovative Advanced Concepts (NIAC) Phase I activity was funded to investigate the feasibility of an innovative approach toward highly energetic pulsed fusion propulsion. Previous concept studies have proposed the conversion of fusion energy for in-space propulsion, ranging from laser-ignited fusion systems such as Gevaltig and VISTA, to the British Interplanetary Society's Daedalus concept and its more recent incarnation under Project Icarus, to steady-state spherical torus fusion systems. Recent NIAC studies have also evaluated several innovative fusion concepts, including the acceleration and compression of field reversed configuration plasmas in time-changing magnetic fields, magnetically driven liners imploding onto plasma targets, and high current z-pinch compression of material liners onto fission-fusion fuel targets. While each of these studies firmly established the potential benefits of fusion systems for interplanetary travel, they also identified significant challenges in successfully engineering such systems for spacecraft propulsion. The concept outlined in this Technical Publication (TP) builds on the lessons learned from these prior activities, approaching the quest for fusion-powered propulsion through an innovative variation of magneto-inertial fusion concepts developed for terrestrial power applications.

Lapointe, M. R.↗
DOE OSTI2018

Ultrasonic Bat Deterrent Technology

The project objective was to advance the development and testing of a near commercial bat-deterrent system with a goal to increase the current GE deterrent system effectiveness to over 50% with broad species applicability. Additionally, the research supported by this program has provided insights into bat behavior and ultrasonic deterrent design that had not previously been explored. Prior research and development had demonstrated the effectiveness of a commercial-grade, air-powered, ultrasonic bat deterrent to be between 30-50% depending upon the species of bat. However, the previous research provided limited insight into the behavioral responses of bats in the presence of ultrasonic deterrent sound fields that could be utilized to improve effectiveness. A unique bat flight room was utilized to observe the behavioral characteristics of bats in the presence of ultrasonic sound fields. Behavioral testing in the bat flight facility demonstrated that ultrasonic sounds similar to those produced by the GE deterrent influenced the activities and behaviors, primarily those associated with foraging, of the species exposed. The study also indicated that continuous and pulsing ultrasonic signals had a similar effect on the bats, and confirmed that as ultrasonic sounds attenuate, their influence on the bats’ activities and behavior decreases. Ground testing at Wolf Ridge Wind, LLC and Shawnee National Forest assessed both continuous and pulsing deterrent signals emitted from the GE deterrent system and further enhanced the behavioral understanding of bats in the presence of the deterrent. With these data and observations, the existing 4-nozzle continuous, or steady, emission ultrasonic system was redesigned to a 6-nozzle system that could emit a pulsing signal covering a larger air space around a turbine. Twelve GE 1.6-100 turbines were outfitted with the deterrent system and a formal three-month field study was performed using daily carcass searches beneath the 12 turbines. Additionally, a unique 3D bat flight path visualization system was utilized to monitor for and identify any changes in bat activity caused by the operation of the deterrent system. Both the carcass search and flight path visualization data indicated that the pulsed deterrent system was effective, but not more effective, than the steady system tested in prior years. However, an unanticipated byproduct of the pulsing system was the emission of intermittent water vapor from the deterrent devices due to the air compression process that powered the devices. This water vapor may have altered the ultrasonic signal and obscured the results in an unknown way. While a qualitative analysis of the effect of the water vapor on the deterrent signal had indicated there was not dramatic change in the expected ultrasonic signal, it was not possible to conclusively determine if the pulse signal would have been more effective in the absence of the water vapor. A mid-season installation of a desiccant system was performed and the dataset divided into two groups to account for the change. Prior to the system change, the deterrent was not effective (-23%, P = 0.8617, α = 0.05) at reducing eastern red bat fatalities and effective (38%, P = 0.0169, α = 0.05) for the non-eastern red bat species, combined. After the installation of the desiccant system, the pulsed deterrent system showed similar results, although not statistically significant, with a point estimates of 23% (P = 0.2924, α = 0.05) observed for eastern red bats and 54% (P = 0.0926, α = 0.05) for the other combined bat species.

17 WIND ENERGY↗
NASA NTRS1996

ORION Low Cost Laser Analysis

We show that laser-target interaction physics demands the shortest laser pulse of which hardware is capable (but not less than 100 ps) in the ORION ground-based laser concept. We compare two leading ways to achieve such pulses - SRS/SBS cascade compression and grating compression - with the standard MOPA approach, and conclude that the first of these is most robust. However, the state of the art in laser devices will require a year or two to implement these ideas. We present a pulse format and beam footprint protocol which will solve the conflict between relativistic lookahead and beam tilt and should permit all-laser active acquisition and tracking in ORION.

Phipps, Claude R.↗
DOE OSTI2019

Nonlinear Dynamics and Phase Space Manipulations of High-Brightness Beams

The project consisted of two main tasks. Each task had several specific aims. The three main objectives of Task 1 were: 1. Investigation of the flat beam technique to produce high transverse emittance ratio longitudinally-compressed bunches, 2. Exploration of a new chicane-like transverse-to-longitudinal phase space exchanger for precise pulse shaping and emittance exchange, 3. Applications of flat-beam with shaped current profile(s) to dielectric wakefield acceleration in an asymmetric waveguide. The outcome of our research was to performed details simulations of flat-beam generation and compression. Some preliminary experiment on flat-beam generation and compression were conducted at the FAST-IOTA injector in parallel to commissioning activities. Likewise, the longitudinal phase-space transformation was not fully explored; we participated in experiments conducted at the Argonne Wakefield Accelerator and especially introduced a simple transverse-shaping technique.

43 PARTICLE ACCELERATORS↗
DOE OSTI2018

Russian Physics Journal (Former Soviet Physics Journal) and its Contribution to the Development of High-Current Pulse Electronics and Electrophysics

This article assesses the impact that the journal has had on the research and development in high-current pulse electronics and electrophysics, gas electronics, physics of gas lasers, relativistic microwave electronics, plasma electronics, etc. All these fields of research involve achievements in three areas of science and technology, namely, the creation of high-power nanosecond pulse generators; fundamental studies of nanosecond high-current discharges in gases, which have led to the discovery of the phenomenon of multielectron initiation of discharges, and studies of pulsed vacuum discharges, which have resulted in the discovery of explosive electron emission. The author began his research activities in these areas in 1958 at Tomsk Polytechnic Institute and continued them at the Institute of High Current Electronics of the Siberian Branch of the USSR Academy of Sciences, which was opened in 1977. A number of articles published in the journal were devoted to priority issues such as the studies of nanosecond discharges in gases, in vacuum, and in water; the description of the properties of explosive electron emission; the invention of metal-dielectric cathodes with ferroelectrics, and the proposal of gas compression in devices based on electrically exploded cylindrical conductors.

42 ENGINEERING↗
DOE OSTI2020

Demonstration of a 2 ps, 5 TW peak power, long-wave infrared laser based on chirped-pulse amplification with mixed-isotope CO 2 amplifiers 2 amplifiers

We report generation of 5 TW peak power in a 2 ps pulse at 9.2 µm via chirped-pulse amplification (CPA) in mixed-isotope high-pressure CO 2 laser amplifiers. This represents the highest peak power in a single picosecond pulse format and the shortest pulse at terawatt peak power ever achieved in the long-wave infrared (LWIR) spectral range. Maximum demonstrated energy of the compressed pulse is 14 J and minimum period between shots is 20 s. The successful implementation of the chirped pulse amplification technique in a short-pulse gas laser opens a route to development of LWIR laser facilities with tens of terawatts of peak power, thus approaching the number of photons per optical cycle of current near-infrared laser systems based on solid-state active media.

43 PARTICLE ACCELERATORS↗
NASA NTRS1996

On the Theory of High-Power Ultrashort Pulse Propagation in Raman-Active Media

The propagation of an intense femtosecond pulse in a Raman-active medium is analyzed. An analytic solution which describes in explicit form the evolution of the light pulse is derived. The field of an intense light wave undergoes a substantial transformation as the wave propagates through the medium. The nature of this transformation can change over time scales comparable to the period of the optical oscillations. As a result, the pulse of sufficiently high energy divides into stretched and compressed domains where the field decreases and increases respectively.

Belenov, E. M.↗
DOE OSTI2018

A new developed in-between shots lithium evaporation coating system for improving plasma performance in EAST

A new in-between shots evaporative lithium coating system has been successfully developed and implemented on the Experimental Advanced Superconducting Tokamak (EAST) for the 2017 campaign. This paper describes a novel technique for the introduction of lithium into the EAST vessel allowing evaporative coatings to be applied between discharges without requiring a significant amount of time to insert and retract the lithium source. This newly designed system utilizes a rotating axis driven by a vacuum dynamic sealing feedthough under remote control to open and close a shutter. A compression bellows, which drives the delivery tube, guarantees accurate position of the oven thus avoiding possible direct contact with the plasma. This allows the new evaporation system to be operated in two distinct modes. One mode is operated in-between shots to refresh pre-coated lithium film, the other is a real-time lithium vapor injection during plasma operations to provide active wall conditioning during long pulse plasma discharges. In this paper, operation of this new lithium deposition system in the in-between shots replenishment mode is described. Initial experiments show that this system worked well during the interval of discharges in EAST, and the in-between shots lithium coating effectively reduced the wall recycling and impurity concentrations. Furthermore, the application of fresh lithium coating lead to sustain the plasma stored energy and confinement, as well as a reduction of impurity radiation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2024

Exploring Standing and Reflected Slow-mode Waves in Flaring Coronal Loops: A Parametric Study Using 2.5D MHD Modeling

Abstract Recent observations of reflected propagating and standing slow-mode waves in hot flaring coronal loops have spurred our investigation into their underlying excitation and damping mechanisms. To understand these processes, we conduct 2.5D magnetohydrodynamic (MHD) simulations using an arcade active region model that includes a hot and dense loop. Our simulations allow for in-depth parametric investigations complementing and expanding our previous 3D MHD modeling results. We excite these waves using a large-amplitude, flow pulse applied at one footpoint of the loop in two distinct models as motivated by observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). The first model (Model 1) incorporates classical compressive viscosity coefficient, while the second model (Model 2) adopts a 10-times enhanced viscosity coefficient. We obtain the following major results: (1) Our 2.5D MHD simulations reinforce previous conclusions derived from 1D and 3D MHD models that significantly enhanced viscosity is crucial for the rapid excitation of standing slow waves with damping times consistent with observations by Wang et al. (2015). (2)We uncover that nonlinearity in Model 1 delays the conversion of a reflected propagating wave into a standing wave. In contrast, Model 2 exhibits a much weak influence of nonlinearity on the excitation time of standing waves, thanks to the suppression of these effects by enhanced viscosity. (3) Our results reveal that the transverse temperature structure holds more influence on wave behavior than the density structure. In Model 1, increased loop temperature contrast significantly enhances wave trapping within the structure, mitigating the impact of temperature-dependent viscous damping. Conversely, in Model 2, the impact of temperature structure on wave behavior weakens in comparison to the effect of viscosity. (4) Model 1 displays evident nonlinear coupling to the fast and kink magnetoacoustic waves and pronounced wave leakage into the corona. Model 2 exhibits significantly weaker effects in this regard. Analyzing three observed wave events by SDO/AIA aligns with Model 2 predictions, providing further support for the substantial viscosity increase. Our 2.5D study unravels the complex interplay of wave-flow phenomena and nonlinear processes in coronal loops, extending our previous 1D modeling results to incorporate more realistic loop geometry. This provides insights into scenarios where 3D effects may be neglected, thereby enhancing our understanding of the intricate dynamics of the solar corona.

Tongjiang Wang↗
DOE OSTI2016

Eye-safe picosecond Raman laser

The results of development of a picosecond Nd :YAG laser with SBS and SRS pulse compression are presented. The laser emits single-frequency radiation (one longitudinal cavity mode of a passively Q-switched master oscillator) with a pulse energy of 5 mJ at a pulse duration of about 30 ps and a pulse repetition rate of 100 Hz. The output laser wavelength is 1530 nm. The laser beam quality is close to the diffraction limit (M{sup 2}⩽1.2). Thermally induced phase distortions introduced into the laser beam by the active elements of laser amplifiers are studied and a method of their compensation is proposed. Using this method, we have developed, fabricated, and successfully tested aspherical optical elements compensating for thermal aberrations of active elements, which has allowed us to decrease the beam divergence and increase the output energy. (lasers. active media)

42 ENGINEERING↗
NASA NTRS1976

Waves in active and passive periodic structures - A review

The theory and recent applications of waves in periodic structures are reviewed. Both the Floquet and coupled waves approach are analyzed in some detail. The theoretical part of the paper includes wave propagation in unbounded and bounded active or passive periodic media, wave scattering from periodic boundaries, source radiation (dipole, Cerenkov, transition, and Smith-Purcell) in periodic media, and pulse transmission through a periodic slab. The applications part covers the recent development in a variety of fields: distributed feedback oscillators, filters, mode converters, couplers, second-harmonic generators, deflectors, modulators, and transducers in the fields of integrated optics and integrated surface acoustics. Work on insect compound eyes, mechanical structures, ocean waves, pulse compressions, temperature waves, and cholesteric liquid crystals, and particles interaction with crystals is briefly reviewed, especially in the case of zeolite crystals and superlattices. Recent advances in fabrication techniques for very fine gratings are also covered.

Elachi, C.↗
DOE OSTI2022

Strain localization criteria for viscoplastic geomaterials

This report presents a viscoplastic localization criterion to detect quasi-instantaneous (i.e., load-induced) and delayed (creep-induced) strain localization in rate-dependent solids. The study is based on the theory of controllability and a viscoplastic description of the mechanical response. Analytical precursors of unstable states are defined through systems of ordinary differential equations (OEDs). The use of the proposed criteria is illustrated at the material point level through a set of strain localization analyses simulating active strain localization of a porous rock. In addition, full-field finite element simulations of compression tests conducted under various pressures are reported to demonstrate the role of local unstable viscoplasticity in the spontaneous propagation of deformation bands under stationary boundary conditions. The study shows that the viscoplastic localization criterion maintains a negative sign as long as the behavior is unstable, that is, the rate of deformation is accelerating. The sign switch coincides with the transition to decelerating deformation. The analyses revealed that pulses of overstress always emerge in correspondence with the growth of unstable behavior, and the peak matches the transition to stable behavior. The local responses recovered from full-field analyses were consistent with those observed in analyses at material point level and the predictions of the presented theory.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Picosecond 1.3-μm bismuth fibre laser mode-locked by a nonlinear loop mirror

The influence of the concentration of bismuth active centres (BACs) in phosphosilicate fibres on their optical parameters, including gain coefficient and non-saturable losses, has been studied. A range of BAC concentrations optimal for designing ultrashort-pulse (USP) lasers was chosen based on the obtained results. The optimised fibre was used to fabricate an all-fibre 1.3-μm USP laser mode-locked by a nonlinear loop mirror, which emits 11.3-ps pulses with an energy of 1.65 nJ and a repetition rate of 3.6 MHz. A bismuth fibre amplifier made it possible to increase the pulse energy to 8.3 nJ. After compression in a diffraction grating compressor, the pulse duration decreased to 530 fs. (paper)

42 ENGINEERING↗
DOE OSTI2021

Long duration x-ray source development for x-ray diffraction at the National Ignition Facility

We present the results of experiments to produce a 10 ns-long, quasi-monochromatic x-ray source. This effort is needed to support time-resolved x-ray diffraction (XRDt) measurements of phase transitions during laser-driven dynamic compression experiments at the National Ignition Facility. To record XRDt of phase transitions as they occur, we use high-speed (∼1 ns) gated hybrid CMOS detectors, which record multiple frames of data over a timescale of a few to tens of ns. Consequently, to make effective use of these imagers, XRDt needs the x-ray source to be narrow in energy and uniform in time as long as the sensors are active. The x-ray source is produced by a laser irradiated Ge foil. Our results indicate that the x-ray source lasts during the whole duration of the main laser pulse. Both time-resolved and time-integrated spectral data indicate that the line emission is dominated by the He-α complex over higher energy emission lines. Time-integrated spectra agree well with a one-dimensional Cartesian simulation using HYDRA that predicts a conversion efficiency of 0.56% when the incident intensity is 2 × 1015 W/cm2 on a Ge backlighter.

Werellapatha, K. (ORCID:0000000293154054)↗
DOE OSTI2018

Temporal feedback control of high-intensity laser pulses to optimize ultrafast heating of atomic clusters

We describe how active feedback routines can be applied at a limited repetition rate (5 Hz) to optimize high-power (>10 TW) laser interactions with clustered gases. Optimization of x-ray production from an argon cluster jet, using a genetic algorithm, approximately doubled the measured energy through temporal modification of the 150 mJ driving laser pulse. This method achieved an increased radiation yield through exploration of a multi-dimensional parameter space, without requiring detailed a priori knowledge of the complex cluster dynamics. The optimized laser pulses exhibited a slow rising edge to the intensity profile, which enhanced the laser energy coupling into the cluster medium, compared to the optimally compressed FWHM pulse (40 fs). This report suggests that this technique can be more widely utilized for control of intense pulsed secondary radiation from petawatt-class laser systems.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1975

On-board data management study for EOPAP

The requirements, implementation techniques, and mission analysis associated with on-board data management for EOPAP were studied. SEASAT-A was used as a baseline, and the storage requirements, data rates, and information extraction requirements were investigated for each of the following proposed SEASAT sensors: a short pulse 13.9 GHz radar, a long pulse 13.9 GHz radar, a synthetic aperture radar, a multispectral passive microwave radiometer facility, and an infrared/visible very high resolution radiometer (VHRR). Rate distortion theory was applied to determine theoretical minimum data rates and compared with the rates required by practical techniques. It was concluded that practical techniques can be used which approach the theoretically optimum based upon an empirically determined source random process model. The results of the preceding investigations were used to recommend an on-board data management system for (1) data compression through information extraction, optimal noiseless coding, source coding with distortion, data buffering, and data selection under command or as a function of data activity, (2) for command handling, (3) for spacecraft operation and control, and (4) for experiment operation and monitoring.

Davisson, L. D.↗