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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Intensity Modulated Radiation Therapy (IMRT) With Simultaneously Integrated Boost Shortens Treatment Time and Is Noninferior to Conventional Radiation Therapy Followed by Sequential Boost in Adjuvant Breast Cancer Treatment: Results of a Large Randomized Phase III Trial (IMRT-MC2 Trial)

In the modern era, improvements in radiation therapy techniques have paved the way for simultaneous integrated boost irradiation in adjuvant breast radiation therapy after breast conservation surgery. Nevertheless, randomized trials supporting the noninferiority of this treatment to historical standards of care approach are lacking.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

Hypofractionated Radiation Therapy to the Prostate Bed With Intensity-Modulated Radiation Therapy (IMRT): A Phase 2 Trial

Postoperative radiation therapy (RT) is a common therapy used for patients with prostate cancer. Although clinical trials have established the safety and efficacy of hypofractionation as a primary therapy, there are limited data in a postoperative setting. We conducted a prospective trial to evaluate the safety and feasibility of postoperative hypofractionated RT to the prostate bed.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2021

International Recommendations on Reirradiation by Intensity Modulated Radiation Therapy for Locally Recurrent Nasopharyngeal Carcinoma

Reirradiation for locally recurrent nasopharyngeal carcinoma (NPC) is challenging because prior radiation dose delivered in the first course is often close to the tolerance limit of surrounding normal structures. A delicate balance between achieving local salvage and minimizing treatment toxicities is needed. However, high-level evidence is lacking because available reports are mostly retrospective studies on small series of patients. Pragmatic consensus guidelines, based on an extensive literature search and the pooling of opinions by leading specialists, will provide a useful reference to assist decision-making for these difficult decisions.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2022

Intense cyclic heating effects on thermo-fracture and thermal shock of solid tungsten and open-cell tungsten foam

Here we investigate here the effects of transient (cyclic) arc-jet plasma and laser heating on fracture behavior of W-foam and solid tungsten. The two key parameters that control the foam thermomechanical response are its density and mean cell size expressed in Pores Per Inch (PPI). Tungsten foam samples were fabricated with Chemical Vapor Deposition (CVD) with variety of PPI and relative density. These were tested under two types of qualitatively different conditions: (1) high-enthalpy arc-jet, and (2) high-power cyclic laser heating. None of the foam samples showed macroscopic through-thickness cracks. However, distributed micro-cracks were observed on ligaments and their triple junctions. Under the same loading conditions, W-foam and solid tungsten showed similar crack network pattern and characteristic length-scale. However, Crack Opening Displacement (COD) was twice as large in solid W as compared to W-foam. Foam samples that have been previously exposed to a low-pressure helium plasma showed significant changes in their surface forming nano-texture fuzz which was removed by subsequent testing in the arc-jet. Extensive fracture and re-crystallization were observed in the thin solid W disk that was fully-constrained from expansion. Thicker and fully-constrained solid W disks did not display recrystallization, grain growth, and extensive cracking. However, thicker disks that were free to expand showed some recrystallization and extensive through-thickness cracks due to less effective cooling and thus higher temperatures. Laser beam testing showed no visible damage formation at 0.19 GW/m 2 and 0.38 GW/m 2 for both low-density (23%) and high-density (43%) foams at low pulses (100-1000). Micro-cracks were observed after 10,000 pulses at 0.19 GW/m 2 in both foams, and in low-density foam after 100,000 at 0.38 GW/m 2 . The nature of thermomechanical damage in W-foam exposed to extreme power (GW/m 2 ) short-duration laser pulses was found to be qualitatively similar to that of high power (MW/m 2 ) long-duration arc-jet.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Concentric core-shell tracks and spectroscopic properties of SrTiO 3 under intense electronic excitation

A deeper understanding of the intrinsic link between the irradiation-induced microstructures and the corresponding spectroscopic properties is becoming increasingly attractive for the research fields of materials science, physics, and information technology. In this work, the structural damage response, spectroscopic features, and associated physical mechanisms of SrTiO 3 single crystals under swift heavy ion irradiation were comparatively analyzed using a combination of experimental and theoretical approaches. Corresponding to 0.11–5.00 MeV/u ion irradiation with electronic energy loss ranging from 4.0 to 29.3 keV/nm, the inelastic thermal spike calculations combined with molecular dynamics simulations are compared with the experimental observations, revealing the track fine structures (individual spherical defects with a disordered region, and discontinuous and continuous tracks consisting of an amorphous core and a disordered outer shell) and demonstrating the dominant effects of the deposition energy and lattice temperature on track damage formation and evolution; thus, two essential thresholds for defect formation of ~0.60 eV/atom and amorphous region formation of ~1.81 eV/atom were identified to better describe the concentric core-shell track structure. The enhanced nanohillock formation in the surface region is attributed to the combined action of kinetic and potential energy depositions, and the fluence dependence in regulating the hillock dimensions is also presented. The measured refractive index profiles along different crystal axes further indicate the anisotropy of irradiation-induced lattice expansion. With increasing ion fluence and damage level, the intrinsic bandgap gradually decreased, and the concentration of additional radiative recombination centers (1.81 eV, 2.31 eV, and 2.42 eV) accordingly increased in the SrTiO 3 crystal, providing the possibility of regulating related defects to achieve tunable/selective photon emission for more critical technological applications.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Towards a new generation of solid total-energy detectors for neutron-capture time-of-flight experiments with intense neutron beams

Challenging neutron-capture cross-section measurements of small cross sections and samples with a very limited number of atoms require high-flux time-of-flight facilities. In turn, such facilities need innovative detection setups that are fast, have low sensitivity to neutrons, can quickly recover from the so-called γ-flash, and offer the highest possible detection sensitivity. In this paper, we present several steps towards such advanced systems. Specifically, we describe the performance of a high-sensitivity experimental setup at CERN n_TOF EAR2. It consists of nine sTED detector modules in a compact cylindrical configuration, two conventional used large-volume C 6 D 6 detectors, and one LaCl 3 (Ce) detector. The performance of these detection systems is compared using 93 Nb(n, γ) data. We also developed a detailed G EANT small4 Monte Carlo model of the experimental EAR2 setup, which allows for a better understanding of the detector features, including their efficiency determination. This Monte Carlo model has been used for further optimization, thus leading to a new conceptual design of a γ detector array, STAR, based on a deuterated-stilbene crystal array. Finally, the suitability of deuterated-stilbene crystals for the future STAR array is investigated experimentally utilizing a small stilbene-d12 prototype. The results suggest a similar or superior performance of STAR with respect to other setups based on liquid-scintillators, and allow for additional features such as neutron-gamma discrimination and a higher level of customization capability.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Intense formation of secondary ultrafine particles from Amazonian vegetation fires and their invigoration of deep clouds and precipitation

New particle formation (NPF) in fire smoke is thought to be unlikely due to large condensation and coagulation sinks that scavenge molecular clusters. We analyze aircraft measurements over the Amazon and find that fires significantly enhance NPF and ultrafine particle (UFP < 50 nm diameter) numbers compared to background conditions, contrary to previous understanding. We identify that the nucleation of dimethylamine with sulfuric acid, which is aided by the formation of extremely low volatility organics in biomass-burning smoke, can overcome the large condensation and coagulation sinks and explain aircraft observations. We show that freshly formed clusters rapidly grow to UFP sizes through biomass-burning secondary organic aerosol formation, leading to a 10-fold increase in UFP number concentrations. Here, we find a contrasting effect of UFPs on deep convective clouds compared to the larger particles from primary emissions for the case investigated here. UFPs intensify the deep convective clouds and precipitation due to increased condensational heating, while larger particles delay and reduce precipitation.

54 ENVIRONMENTAL SCIENCES↗