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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

UCGretina geant4 simulation of the GRETINA Gamma-Ray Energy Tracking Array

UCGretina, a geant4 simulation of the GRETINA gamma-ray tracking array of highly-segmented high-purity germanium detectors is described. We have developed a model of the array, in particular of the Quad Module and the capsules, that gives good agreement between simulated and measured photopeak efficiencies over a broad range of gamma-ray energies and reproduces the shape of the measured Compton continuum. Both of these features are needed in order to accurately extract gamma-ray yields from spectra collected in in-beam gamma-ray spectroscopy measurements with beams traveling at v / c ≳0.3 at the National Superconducting Cyclotron Laboratory and the Facility for Rare Isotope Beams. In the process of developing the model, we determined that millimeter-scale layers of passive germanium surrounding the active volumes of the simulated crystals must be included in order to reproduce measured photopeak efficiencies. In conclusion, we adopted a simple model of effective passive layers and developed heuristic methods of determining passive-layer thicknesses by comparison of simulations and measurements for a single crystal and for the full array. Prospects for future development of the model are discussed.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Accelerated radiation transport modeling techniques for pencil beam computed tomography using gamma rays

Monte Carlo radiation transport modeling studies were performed for a compact, and high-resolution gamma-ray computed tomography system designed for imaging irradiated nuclear fuel. The system comprises a 60 Co source – chosen for its highly penetrating 1173 keV and 1332 keV gamma rays – a pair of high-aspect-ratio pencil beam collimators, and an inorganic scintillator detector. Here two acceleration methods are proposed to rapidly model a transmission type gamma-ray tomography system. The first, a variance reduction technique, is based on performing Monte Carlo simulations with a monodirectionally-biased source, sampled from a characteristic sub-volume of the full source volume. The second acceleration method is based on the deterministic calculations using the Beer–Lambert law and detector response characteristics. Comparison of simulations using acceleration approaches with analog simulations of the fully isotropic, full-volume equivalent, show that the Monte Carlo variance reduction technique gives quantitatively accurate predictions for large collimator aspect ratios while the deterministic calculations are semi-quantitative but converge close to the correct result as the collimator aspect ratio increases. As such, these techniques can be used to reduce the computational cost in generating simulated radiographs and tomographs by several orders of magnitude. Experimental validation efforts are currently underway and will be demonstrated in future work.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2023

Compatibility of ethylene vinyl acetate (EVA)/ethylene vinyl alcohol (EVOH)/EVA films with gamma, electron-beam, and X-ray irradiation

Many polymer-based medical devices are sterilized by gamma irradiation. To reduce the use of cobalt-60 gamma-ray sources, transition from gamma ray to alternative irradiation technologies was proposed, namely electron beam (e-beam) and X-ray. A major impediment for such a transition is the knowledge gap in material compatibility with the different radiation sources. In this study, multi-layer films consisting of ethylene vinyl acetate (EVA) and ethylene vinyl alcohol (EVOH) components were irradiated to target doses of 30, 45, and 60 kGy by gamma-ray, e-beam, and X-ray sources. Effects of irradiation were evaluated on 12 material properties, and statistical comparisons between gamma irradiation and alternative technologies were conducted using the two one-sided t-test (or “equivalence test”) and classic t-test. Melting temperature and UV absorbance below 300 nm showed dose dependencies, while other investigated properties such as discoloration and mechanical durability did not change with dose up to 60 kGy. Based on these results, there is no material compatibility issue associated with the transition from gamma to e-beam or to X-ray as source of sterilization radiation of the studied multi-layer film.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Effects of gamma, electron beam, and X-ray irradiation on the plastic components of a universal bone cement mixer medical device

Due to market and regulatory pressures, many healthcare manufacturers are considering alternatives to cobalt-60 gamma radiation, including accelerator-based electron beam (E-beam) and X-ray radiation for product sterilization. In this work, the effects of irradiation on a representative medical product, comprised of eight distinct polymer materials, were directly compared for three radiation technologies – cobalt-60 gamma, E-beam, and X-ray – at four dose levels (15, 25, 50, and 70 kGy). The objective was to determine how radiation effects (deleterious or beneficial) are influenced by source and dose level, with the specific goal of determining whether E-beam radiation and/or X-ray radiation could be viable alternatives to gamma radiation for device sterilization. Here, the specific product considered is a single-use medical device for orthopedic surgery, the Stryker Instruments MixeVac III bone cement mixer, which is currently sterilized using gamma radiation from cobalt-60 sources. Following ASTM International standards and input from the manufacturer, we characterized the effects of the three radiation sources on product functionality as well as on the mechanical and optical properties of the constituent polymers. Results indicate that although measurable differences in properties between the standard gamma irradiated materials and the alternative E-beam and X-ray irradiated materials were observed, those differences were small. Statistically significant differences were noted in the case of yellowness index for polyvinyl chloride, high-density polyethylene, and polycarbonate, and in the case of tensile elongation at break for high impact polystyrene and polyvinyl chloride. In general, the results of this study support the viability of E-beam and X-ray radiation as alternative options to cobalt-60 gamma radiation for sterilization of Stryker single-use universal bone cement mixer medical devices.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Gamma, electron beam and X-ray irradiation effects on polymers in an advanced bone cement mixer device

The medical device industry has been investigating ways to increase the use of alternatives to cobalt-60 gamma radiation and ethylene-oxide gas sterilization, such as electron beam (E-beam) and X-ray radiation, due to regulatory and market pressures. One impediment to switching to E-beam or X-ray technology for sterilization is the lack of data on the effects of these radiation sources on medical device polymers. To provide such data this work considers irradiation and testing of a common single-use medical bone cement mixing system, the Stryker Advanced Cement Mixer (ACM®), that is composed of seven polymer materials. The ACM® devices considered here were processed to sterilization-relevant doses (15, 25, 50, and 70 kGy) using three radiation technologies: gamma, E-beam, and X-ray. The system and its polymer components were tested for product functionality, as well as mechanical and visual properties to determine how exposure effects may be influenced by radiation technology and dose level. We found that although there were instances of statistically significant differences in effects between the gamma-irradiated products and those irradiated with E-beam and X-ray, those effects were negligible in terms of retained functionality of the product and retained mechanical properties of the polymer components. Overall, results of this study demonstrate that, for of the effects studied, E-beam and X-ray are viable alternatives to cobalt-60 gamma radiation for sterilization of the polymer-based device investigated.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2021

In-beam γ-ray spectroscopy of 37–42 P

The level schemes of the neutron-rich 37-42 P isotopes are investigated via in-beam gamma-ray spectroscopy following the fragmentation of a 45 Cl projectile beam at intermediate beam energies. Information on gamma-gamma coincidence relationships complemented by comparisons to shell-model calculations in the sd-pf model space were used to construct excitation level schemes for these neutron-rich nuclei. For the odd-mass 37,39 P isotopes, a level scheme is presented that appears essentially complete at low energies and exhausts the states predicted by the SDPF-MU shell-model Hamiltonian. In conclusion, simple Nilsson configurations are proposed for the low-lying excited states of 38,39,40,41 P from an analysis of the E2 transition matrix elements and moments calculated within the shell model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2022

Generation of collimated vortex gamma-rays from intense Poincaré beam–plasma interaction

We report on numerical calculations in which a multi-petawatt γ-ray beam is generated using a novel configuration based on fully structured light irradiating an overdense plasma waveguide. We analyze how the relativistic laser pulse efficiently confines and accelerates plasma electrons to GeV-scale energies and drives a quasi-static field that induces magneto-bremsstrahlung radiation. Multiphoton Compton scattering of electrons in the intense part of the laser also occurs although the radiated energy-density is comparatively lower. The emitted γ-rays carry orbital angular momentum, are highly collimated, and account for upwards of 15% of the incident field energy in one particular case. A comparison of the laser-to-particle angular momentum and energy transfer efficiencies is made between the cases of irradiation by a circularly polarized Laguerre–Gauss mode and one type of full Poincaré beam, and it is found that the latter yields an order-of-magnitude enhancement. In conclusion, the essential characteristics of the interaction are validated with three-dimensional particle-in-cell simulations that include quantum electrodynamical effects.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Dynamic Testing of a Commercial FRAM Device Under Gamma Ray Dose and Neutron Beam

Here, this work presents dose rate and neutron testing on a ferroelectric random-access memory (FRAM) device in dynamic operation during radiation pulses. Radiation failure modes are shown to be unique. Dose rate failure is shown to be based primarily on integrated dose in the radiation pulse and terminates the FRAM operation and can alter up to 8 bytes of data in storage. Neutron failures are attributed to a shifting of data like a clocking error.

Harris, Nathan↗
DOE OSTI2022

Monte Carlo simulations demonstrating physics of equivalency of gamma, electron-beam, and X-ray for radiation sterilization

We report the sterilization of medical devices using the gamma rays from the decay of cobalt-60 has accumulated decades of experience of the performance of the materials and devices that are irradiated. The use of radiation using electron beams and x-rays has much less experience and this leads to questions of equivalency between these three technologies. Computer simulations were conducted to model the relevant physical processes of the interactions of each of the three forms of radiation in order to compare the spectra of electron energies at energies below 500 keV. It is predominantly the electrons below this threshold that produce the sterilization dose. No difference in energy spectra was seen between the three types of initial radiation. It is concluded that there is no energy dependent difference between gamma, e-beam, and x-ray for radiation sterilization.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Structure of 30 Mg explored via in-beam γ-ray spectroscopy

In the island of inversion, ground states of neutron-rich sd-shell nuclei exhibit strong admixtures of intruder configurations from the fp shell. The nucleus 30 Mg, located at the boundary of the island of inversion, serves as a cornerstone to track the structural evolution as one approaches this region. Spin-parity assignments for excited states in 30 Mg, especially negative-parity levels, have yet to be established. In the present work, the nuclear structure of 30Mg was investigated by in-beam gamma-ray spectroscopy mainly focusing on firm spin-parity determinations. High-intensity rare-isotope beams of 31 Mg, 32 Mg, 34 Si, and 35 P bombarded a Be target to induce nucleon removal reactions populating states in 30 Mg. Gamma rays were detected by the state-of-the-art gamma-ray tracking array GRETINA. For the direct one-neutron removal reaction, final-state exclusive cross sections and parallel momentum distributions were deduced. Multi-nucleon removal reactions from different projectiles were exploited to gain complementary information. With the aid of the parallel momentum distributions, an updated level scheme with revised spin-parity assignments was constructed. Spectroscopic factors associated with each state were also deduced. Results were confronted with large-scale shell-model calculations using two different effective interactions, showing excellent agreement with the present level scheme. Furthermore, a marked difference in the spectroscopic factors indicates that the full delineation of the transition into the island of inversion remains a challenge for theoretical models.

20 ≤ A ≤ 38↗
DOE OSTI2024

PUFFIn – A user friendly fast interface for calculating and visualizing the dose distribution in materials

This article describes a new graphical user interface that uses the PENELOPE Monte Carlo code to calculate dose distributions in materials. It is named PUFFIn, for the Penelope User-Friendly Fast Interface and was developed as an educational and scoping analysis tool for non-experts in radiation modeling. PUFFIn enables the user to visualize and compare the dose distributions in objects (e.g., sterilized healthcare products) irradiated with cobalt-60 gamma-rays, electron beam (E-beam) or X-rays. From such comparisons, the user can determine the most efficient product and/or packaging designs for any given radiation field – whether for conceptual or existing products and packaging. PUFFIn is distributed in a complete, self-contained package of software, including the PENELOPE radiation transport code, a standard graphics package, and a set of simple exercises. The package is available to any user at no cost and requires a minimal amount of training compared to other similar software. PUFFIn's capabilities are described, as well as validation measurements performed at Texas A&M University E-beam facility and the Aerial E-beam Facility in France.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2022

Comparative Effects of Radiation Sterilization Modality on Medical PVC Tubing

As the production volume of single-use, polymer-based medical devices increases each year, so does the need for throughput capacity to sterilize the devices. Around 80% of radiation-sterilized devices are processed using gamma-ray radiation from industrial cobalt-60 sources. Supply chain, security, and disposal concerns are prompting manufacturers and contract sterilizers to explore alternatives to irradiation using cobalt-60 gamma-rays, such as electron beam (E-beam) and X-ray radiation. Advantages of these ‘machine’ sources over radioisotope-based sources are that they do not decay, a characteristic that requires cobalt-60 to be replaced over time, they can be turned off when not in use, and they do not represent the same level of concern regarding misuse. One of the barriers to direct transition from gamma-ray sterilization to E-beam or X-ray sterilization is concern over the relatively unknown effects of sterilization dose of these alternative modalities on the performance of medical device polymers. Commercially available medical devices sterilized with gamma-ray irradiation exhibit acceptable device function, acceptable mechanical performance, and acceptable discoloration. To be viable, alternate sterilization methods must not only achieve acceptable sterilization, but the process must also result in a product with functional, mechanical, and visual effects acceptable to customers and the regulator. Flexible polyvinyl chloride (PVC) is a plastic material that is commonly found in single-use medical devices and is known for its sensitivity to radiation processing. For instance, transparent PVC is known to yellow upon irradiation. To encouraging sterilization alternatives to cobalt-60 gamma-ray, we directly compared the effects of gamma-ray, E-beam, and X-ray radiation exposure at similar sterilization-relevant doses on key properties of medical grade PVC tubing.

cobalt-60↗
DOE OSTI2022

Supplementing Gamma Sterilization with X-Ray and E-Beam Technologies: An International Industry and Academia Collaboration

Ionizing-technology–based industries are growing rapidly around the world. The expansion is driven mostly by the technology’s myriad applications, including polymer crosslinking, medical device sterilization, food pasteurization, and phytosanitary treatment. Ionization also is used in the manufacture of some healthcare products such as medical devices and biopharmaceuticals. Industrial sterilization methods render single-use products and manufacturing components safe and ready for their intended use. ISO11137-1 describes the validation and routine control of a sterilization process for medical devices and mentions the three types of radiation considered under this scope: gamma, X-ray, and electron beam (e-beam)

gamma sterilization, electron beam sterilization, ↗
DOE OSTI2021

Organic glass scintillator bars with dual-ended readout

Organic glass scintillator (OGS) bars (6 × 6 × 50 mm 3 ) were melt-cast and characterized with dual-ended readout by silicon photomultiplier arrays. The results were compared to trans-stilbene bars of the same size. Energy resolution was measured via a 137 Cs Compton-coincidence experiment. Time resolution was determined via a 22 Na coincidence-timing experiment. Depth-of-interaction resolution was measured by moving a gamma ray fan beam along the major axis of the bars. Pulse shape discrimination capability and neutron light output were determined via a time-of-flight measurement of a 252 Cf source. The OGS bars exhibited better energy resolution at 478 keV (10.3 ± 0.5% vs. 11.2 ± 0.5%), better time resolution from 200–341 keVee (270 ps vs. 340 ps FWHM), slightly poorer depth-of-interaction resolution, poorer PSD performance, and higher neutron light output than the stilbene bars. Here, the low cost, ease of manufacturing, brightness, and excellent time resolution make OGS a strong candidate for use in compact radiation imaging systems.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Intense gamma-ray source based on focused electron beams from a laser wakefield accelerator

Laser wakefield accelerators generate ultrashort electron bunches with the capability to produce γ-rays. Here, we produce focused laser wakefield acceleration electron beams using three quadrupole magnets. Electron beams are then focused into a 3 mm lead converter to generate intense, focused bremsstrahlung γ beams. Experimental results demonstrate the generation and propagation of focused γ beams to a best focus spot size of 2.3 ± 0.1 × 2.7 ± 0.2 mm 2 using a copper stack calorimeter. Monte Carlo simulations conducted using GEANT4 are in good agreement with experimental results and enable detailed examination of γ-ray generation. Simulations indicate that the focused γ beams contained 2.6 × 10 9 photons in the range of 100 keV to 33 MeV with an average energy of 6.4 MeV. A γ-ray intensity of 7 × 10 10 W/cm 2 was estimated from simulations. In conclusion, the generation of focused bremsstrahlung γ-ray sources can have important applications in medical imaging applications and laboratory astrophysics experiments.

43 PARTICLE ACCELERATORS↗