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Bradley, D.

Publications and source records attributed to Bradley, D..

15 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Diagnosing inertial confinement fusion ignition

Abstract Fusion ignition by inertial confinement requires compression and heating of the fusion fuel to temperatures in excess of 5 keV and densities exceeding hundreds of g/cc. In August 2021, this scientific milestone was surpassed at the National Ignition Facility (NIF), when the Lawson criterion for ignition was exceeded generating 1.37MJ of fusion energy (Abu-Shawareb et al 2022 Phys. Rev. Lett. 129 075001), and then in December 2022 target gain >1 was realized with the production of 3.1MJ of fusion energy from a target driven by 2.0MJ of laser energy (Abu-Shawareb et al 2024 Phys. Rev. Lett. 132 065102). At the NIF, inertial confinement fusion research primarily uses a laser indirect drive in which the fusion capsule is surrounded by a high-Z enclosure (‘hohlraum’) used to convert the directed laser energy into a symmetric x-ray drive on the capsule. Precise measurements of the plasma conditions, x-rays, γ -rays and neutrons produced are key to understanding the pathway to higher performance. This paper discusses the diagnostics and measurement techniques developed to understand these experiments, focusing on three main topics: (1) key diagnostic developments for achieving igniting plasmas, (2) novel signatures related to thermonuclear burn and (3) advances to diagnostic capabilities in the igniting regime with a perspective toward developments for intertial fusion energy.

Moore, A. S. (ORCID:0000000221258882)↗
DOE OSTI2022

Hot Spot Evolution Measured by High-Resolution X-Ray Spectroscopy at the National Ignition Facility

Evolution of the hot spot plasma conditions was measured using high-resolution x-ray spectroscopy at the National Ignition Facility. The capsules were filled with DD gas with trace levels of Kr and had either a high-density-carbon (HDC) ablator or a tungsten (W)-doped HDC ablator. Time-resolved measurement of the Kr He β spectra, absolutely calibrated by a simultaneous time-integrated measurement, allows inference of the electron density and temperature through observing Stark broadening and the relative intensities of dielectronic satellites. By matching the calculated hot spot emission using a collisional-radiative code to experimental observations, the hot spot size and areal density are determined. Here these advanced spectroscopy techniques further reveal the effect of W dopant in the ablator on the hot spot parameters for their improved implosion performance.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Optimized continuum x-ray emission from laser-generated plasma

We study continuum x-ray emission from hot plasma at the National Ignition Facility (NIF). We find that the x-ray yield in the multi-keV photon energy range is larger in Ti than in Ag or Au. This apparent paradox is due to Ti K-shell vacancies generated by the extraordinary energy density achieved by the NIF lasers. This is supported by direct observations of large continuum enhancement above the Ti K-series limit due to both free–bound (recombination) emission and strong Ly α (H-like) emission. Detailed calculations agree well with our measurements and support our conclusions. <!--/abstract content--><!--fulltext content--> X-ray emission from matter pervades the universe and plays an important role in the high-energy density (HED) regime (~10 5 J/cm 3 ). For example, the emission and absorption of x-rays controls the thermal state and evolution of stellar interiors.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2019

The Origins Space Telescope

The Origins Space Telescope will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did galaxies evolve from the earliest galactic systems to those found in the universe today? How do habitable planets form? How common are life-bearing worlds? To answer these alluring questions, Origins will operate at mid- and far-infrared wavelengths and offer powerful spectroscopic instruments and sensitivity three orders of magnitude better than that of Herschel, the largest telescope flown in space to date. After a 3 ½ year study, the Origins Science and Technology Definition Team will recommend to the Decadal Survey a concept for Origins with a 5.9-m diameter telescope cryo cooled to 4.5 K and equipped with three scientific instruments. A mid-infrared instrument (MISC-T) will measure the spectra of transiting exoplanets in the 2.8 – 20 μm wavelength range and offer unprecedented sensitivity, enabling definitive biosignature detections. The Far-IR Imager Polarimeter (FIP) will be able to survey thousands of square degrees with broadband imaging at 50 and 250 μm. The Origins Survey Spectrometer (OSS) will cover wavelengths from 25 – 588 μm, make wide-area and deep spectroscopic surveys with spectral resolving power R ~ 300, and pointed observations at R ~ 40,000 and 300,000 with selectable instrument modes. Origins was designed to minimize complexity. The telescope has a Spitzer-like architecture and requires very few deployments after launch. The cryo-thermal system design leverages JWST technology and experience. A combination of current-state-of-the-art cryocoolers and next-generation detector technology will enable Origins’ natural background limited sensitivity.

Leisawitz, D.↗
NASA NTRS2018

The Origins Space Telescope: Mission Concept Overview

The Origins Space Telescope (OST) will trace the history of our origins from the time dust and heavy elements permanently altered the cosmic landscape to present-day life. How did the universe evolve in response to its changing ingredients? How common are life-bearing planets? To accomplish its scientific objectives, OST will operate at mid- and far-infrared wavelengths and offer superlative sensitivity and new spectroscopic capabilities. The OST study team will present a scientifically compelling, executable mission concept to the 2020 Decadal Survey in Astrophysics. To understand the concept solution space, our team studied two alternative mission concepts. We report on the study approach and describe both of these concepts, give the rationale for major design decisions, and briefly describe the mission-enabling technology.

Leisawitz, D.↗
NASA NTRS1972

Summary of results of parametric studies of space shuttle booster, orbiter, and launch vehicle concepts

The results of analytical and experimental parametric studies of space shuttle booster, orbiter and launch vehicle aerodynamics are described. During this study over 1700 hours of experimental wind tunnel tests were conducted on several versions of the shuttle booster, orbiter and launch vehicle. Fifteen separate tests were conducted in three different test facilities. Due to the number of test programs conducted and the time required for test preparation, analysis of the test data has been limited to that required to drive the experimental program. A brief description of each of the experimental tests conducted including the test purpose and approach is included. Several test models were designed and fabricated in support of the experimental program. These models are described.

Bradley, D.↗
NASA NTRS1972

Space shuttle: Aerodynamic characteristics of cone-cylinder-flare-fin configurations at Mach numbers of 1.96, 2.74, and 4.96 and angles of attack from 50 to 90 degrees

A 0.00227-scale parametric model of an LMSC/MSFC water recoverable booster was tested in the MSFC 14 x 14-inch trisonic wind tunnel. The purpose of the test was to obtain high angle of attack force and static stability data which could be used by MSFC in preliminary design and aerodynamic trade studies. These data were obtained using six-component internal strain gauge balances. One hundred forty-four different geometrical combinations were possible as all model parts were interchangeable (three nose cones, three cylinder lengths, four flare sections and three sets of fins, plus a no-fin case in combination with the other components). However, due to tunnel occupancy limitations, only the most representative combinations were tested. All configurations investigated were tested at Mach 1.96, 2.74 and 4.96 with data obtained at angles of attack from 50 degrees to 90 degrees and at angles of sideslip from -10 degrees to +10 degrees (at an angle of attack of 60 degrees).

Bradley, D.↗
NASA NTRS1972

Effects of cruise engine location and power on interference

Data are presented, in plotted form, of tests for determining the interference effects of space shuttle booster cruise engine location for power-on and power-off conditions. The tests were conducted in a 7 x 10 foot transonic wind tunnel; the model was a 0.015-scale space shuttle booster specially equipped for propulsion effects testing. Data were obtained over a Mach number range of 0.4 to 1.13 at angles of attack from -4 deg to 20 deg at zero degrees sideslip and at angles of sideslip from -6 deg to +6 deg at constant angles of attack of 0 deg, 6 deg, 15 deg, and in some cases 10 deg. Additional parameters investigated were: elevon deflection, canard deflection, aileron deflection, rudder deflection, canard position, and mass flow rate.

Bradley, D.↗
NASA NTRS1972

Space shuttle: Experimental investigations for base drag reduction on a 0.015 scale model MSFS proposed space shuttle booster at Mach numbers from 0.40 to 1.10

A 0.015-scale model of a modified version of the MDAC space shuttle booster was tested to obtain force, static stability, and control effectiveness data. The objective of this test was the reduction of cruise (M = 0.4) base drag by the use of base flaps, base vents, elevon deflection and base flow from a plenum mounted forward of the base heat shield. Transonic data were also obtained to determine the aerodynamic characteristics of the new base shape. Six component aerodynamic force and moment data were recorded over an angle of attack range from 4 deg to 20 deg at 0 deg sideslip and over a sideslip range from -6 deg to 6 deg at 0 deg, 6 deg and 15 deg angle of attack. Mach number varied from 0.4 to 1.10 at a constant R of 2 million per unit length.

Bradley, D.↗
NASA NTRS1971

Space shuttle: Stability and control effectiveness of the MDAC parametric delta canard booster at Mach 0.38. Volume 1: Canard parametric variations

A 0.015 scale model of a modified version of the MDAC space shuttle booster was tested in the Naval Ship Research and Development Center 7 x 10 foot transonic wind tunnel, to obtain force, static stability, and control effectiveness data. Data were obtained for a cruise Mach Number of 0.38, altitude of 10,000 ft, and Reynolds Number per foot of approximately 2 x one million. The model was tested through an angle of attack range of -4 deg to 15 deg at zero degree angle of sideslip, and at an angle of sideslip range of -6 deg to 6 deg at fixed angles of attack of 0 deg, 6 deg, and 15 deg. Other test variables were elevon deflections, canard deflections, aileron deflections, rudder deflections, wing dihedral angle, canard incidence angle, wing incidence angle, canard position, wing position, wing and canard control flap size and dorsal fin size.

Bradley, D.↗