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At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Interstellar Mapping and Acceleration Probe (IMAP): A New NASA Mission

The Interstellar Mapping and Acceleration Probe (IMAP) is a revolutionary mission that simultaneously investigates two of the most important overarching issues in Heliophysics today: the acceleration of energetic particles and interaction of the solar wind with the local interstellar medium. While seemingly disparate, these are intimately coupled because particles accelerated in the inner heliosphere play critical roles in the outer heliospheric interaction. Selected by NASA in 2018, IMAP is planned to launch in 2024. The IMAP spacecraft is a simple sun-pointed spinner in orbit about the Sun-Earth L1 point. IMAP's ten instruments provide a complete and synergistic set of observations to simultaneously dissect the particle injection and acceleration processes at 1 AU while remotely probing the global heliospheric interaction and its response to particle populations generated by these processes. In situ at 1 AU, IMAP provides detailed observations of solar wind electrons and ions; suprathermal, pickup, and energetic ions; and the interplanetary magnetic field. For the outer heliosphere interaction, IMAP provides advanced global observations of the remote plasma and energetic ions over a broad energy range via energetic neutral atom imaging, and precise observations of interstellar neutral atoms penetrating the heliosphere. Complementary observations of interstellar dust and the ultraviolet glow of interstellar neutrals further deepen the physical understanding from IMAP. IMAP also continuously broadcasts vital real-time space weather observations. Finally, IMAP engages the broader Heliophysics community through a variety of innovative opportunities. This papersummarizes the IMAP mission at the start of Phase A development.

McComas, D. J.↗
NASA NTRS2018

Space-and Ground-Based Non-Accelerated Long Lifetime Data for Ruggedized Commercial Non-Planar Ring Oscillator (NPRO) Lasers

Lifetime data is presented for ruggedized commercial NPRO lasers used in the Tropospheric Emission Spectrometer (TES) Instrument on NASA’s Aura Earth-orbiting spacecraft, including 20 years of data from two life test units on the ground, 12 years of on-orbit data from TES Laser A, and 2 years of on-orbit data from TES Laser B. The TES lasers are diode-pumped Non-Planar Ring Oscillator (NPRO) lasers using Nd:YAG crystals. Since accelerated life testing was not possible on the complete laser, early prototype lasers that had gone through thermal cycling and vibration testing were placed on non-accelerated life tests with the hope of gathering at least a couple of years of data before launch. Long-term lifetime data for hybrid laser systems in space applications is not abundant, and out of necessity, accelerated reliability testing is usually done over a relatively short time with a large number of devices. The data presented in this paper is unique as it tracks the optical power output over time of a total of four lasers on the order of decades rather than months or years. Two of the lasers have each been on life test for over 20 years on the ground and are still operating, and the other two lasers have been on-orbit for 14 years. TES Laser A was still operating when the TES Instrument was decommissioned in January 2018. Therefore, the data presented covers over 450,000 non-accelerated device-hours, with 23% of those hours being in space.

Kane, T.J.↗
NASA NTRS2021

Constraining particle acceleration in Sgr A? with simultaneous GRAVITY, Spitzer, NuSTAR, and Chandra observations

We report the time-resolved spectral analysis of a bright near-infrared and moderate X-ray flare of Sgr A⋆. We obtained light curves in the M, K, and H bands in the mid- and near-infrared and in the 2 − 8 keV and 2 − 70 keV bands in the X-ray. The observed spectral slope in the near-infrared band is νLν ∝ ν0.5 ± 0.2; the spectral slope observed in the X-ray band is νLν ∝ ν−0.7 ± 0.5. Using a fast numerical implementation of a synchrotron sphere with a constant radius, magnetic field, and electron density (i.e., a one-zone model), we tested various synchrotron and synchrotron self-Compton scenarios. The observed near-infrared brightness and X-ray faintness, together with the observed spectral slopes, pose challenges for all models explored. We rule out a scenario in which the near-infrared emission is synchrotron emission and the X-ray emission is synchrotron self-Compton. Two realizations of the one-zone model can explain the observed flare and its temporal correlation: one-zone model in which the near-infrared and X-ray luminosity are produced by synchrotron self-Compton and a model in which the luminosity stems from a cooled synchrotron spectrum. Both models can describe the mean spectral energy distribution (SED) and temporal evolution similarly well. In order to describe the mean SED, both models require specific values of the maximum Lorentz factor γmax, which differ by roughly two orders of magnitude. The synchrotron self-Compton model suggests that electrons are accelerated to γmax ∼ 500, while cooled synchrotron model requires acceleration up to γmax ∼ 5 × 104. The synchrotron self-Compton scenario requires electron densities of 1010 cm−3 that are much larger than typical ambient densities in the accretion flow. Furthermore, it requires a variation of the particle density that is inconsistent with the average mass-flow rate inferred from polarization measurements and can therefore only be realized in an extraordinary accretion event. In contrast, assuming a source size of 1 RS, the cooled synchrotron scenario can be realized with densities and magnetic fields comparable with the ambient accretion flow. For both models, the temporal evolution is regulated through the maximum acceleration factor γmax, implying that sustained particle acceleration is required to explain at least a part of the temporal evolution of the flare.

R. Abuter↗
DOE OSTI2015

Field Work Proposal: PUBLIC OUTREACH EVENT FOR ACCELERATOR STEWARDSHIP TEST FACILITY PILOT PROGRAM

Jefferson Lab’s outreach efforts towards the goals of Accelerator Stewardship Test Facility Pilot Program consist of the lab’s efforts in three venues. The first venue, at the end of March is to meet with the members of Virginia Tech Corporate Research Center (VTCRC) (http://www.vtcrc.com/tenant-directory/) in Blacksburg, Virginia. Of the nearly 160 members, we expect that many engineering companies (including mechanical, electrical, bio, software) will be present. To this group, we will describe the capabilities of Jefferson Lab’s accelerator infrastructure. The description will include not only the facilities but also the intellectual expertise. No funding is requested for this effort. The second venue is to reach the industrial exhibitors at the 6th International Particle Accelerator Conference (IPAC’15). Jefferson Lab will host a booth at the conference to reach out to the >75 industrial exhibitors (https://www.jlab.org/conferences/ipac2015/SponsorsExhibitors.php) who represent a wide range of technologies. A number of these industries could benefit if they can access Jefferson Lab’s accelerator infrastructure. In addition to the booth, where written material will be available, we plan to arrange a session A/V presentation to the industry exhibitors. The booth will be hosted by Jefferson Lab’s Public Relations staff, assisted on a rotating basis by the lab’s scientists and engineers. The budget with IPAC’15 designations represents the request for funds for this effort. The third venue is the gathering of Southeastern Universities Research Association (SURA) university presidents. Here we plan to reach the research departments of the universities who can benefit by availing themselves to the infrastructure (material sciences, engineering, medical schools, material sciences, to name a few). Funding is requested to allow for attendance at the SURA Board Meeting. We are coordinating with DOE regarding these costs to raise the projected conference management cost ceiling in the Conference Management Tool.

99 GENERAL AND MISCELLANEOUS↗
DOE OSTI2015

Double layer -- a particle accelerator in the magnetosphere

Slides present the material under the following topics: Introduction (What is a double layer (DL)? Why is it important? Key unsolved problems); Theory -- time-independent solutions of 1D Vlasov--Poisson system; Particle-in-cell simulations (Current-driven DLs); and Electron acceleration by DL (Betatron acceleration). Key problems include the generation mechanism, stability, and electron acceleration. In summary, recent observations by Van Allen Probes show large number of DLs in the outer radiation belt, associated with enhanced flux of relativistic electrons. Simulations show that ion acoustic double layers can be generated by field-aligned currents. Thermal electrons can gain energy via betatron acceleration in a dipole magnetic field.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Kinetic Simulations of Particle Acceleration at Shocks

Collisionless shocks are mediated by collective electromagnetic interactions and are sources of non-thermal particles and emission. The full particle-in-cell approach and a hybrid approach are sketched, simulations of collisionless shocks are shown using a multicolor presentation. Results for SN 1006, a case involving ion acceleration and B field amplification where the shock is parallel, are shown. Electron acceleration takes place in planetary bow shocks and galaxy clusters. It is concluded that acceleration at shocks can be efficient: >15%; CRs amplify B field via streaming instability; ion DSA is efficient at parallel, strong shocks; ions are injected via reflection and shock drift acceleration; and electron DSA is efficient at oblique shocks.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The Machine Protection System for the Fermilab Accelerator Science and Technology Facility

The Machine Protection System (MPS) for the Fermilab Accelerator Science and Technology Facility (FAST) has been implemented and tested. The system receives signals from several subsystems and devices which conveys the relevant status needed to the safely operate the accelerator. Logic decisions are made based on these inputs and some predefined user settings which in turn controls the gate signal to the laser of the photo injector. The inputs of the system have a wide variety of signal types, encoding methods and urgencies for which the system is designed to accommodate. The MPS receives fast shutdown (FSD) signals generated by the beam loss system and inhibits the beam or reduces the beam intensity within a macropulse when the beam losses at several places along the accelerator beam line are higher than acceptable values. TTL or relay contact signals from the vacuum system, toroids, magnet systems etc., are chosen with polarities that ensure safe operation of the accelerator from unintended events such as cable disconnection in the harsh industrial environment of the experimental hall. A RS422 serial communication scheme is used to interface the operation permit generator module and a large number of movable devices each reporting multi-bit status. The system also supports operations at user defined lower beam levels for system conunissioning. The machine protection system is implemented with two commercially available off-the-shelf VMEbus based modules with on board FPGA devices. The system is monitored and controlled via the VMEbus by a single board CPU

Wu, Jinyuan↗
DOE OSTI2016

BENCHMARK ACCELERATED AGING OF HARVESTED HYPALON/EPR AND CSPE/XLPE POWER AND I&C CABLE IN NUCLEAR POWER PLANTS

As part of the Light Water Reactor and Sustainability (LWRS) program in the U.S. Department of Energy (DOE) Office of Nuclear Energy, material aging and degradation research is currently geared to support the long-term operation of existing nuclear power plants (NPPs) as they move beyond their initial 40 year licenses. The goal of this research is to provide information so that NPPs can develop aging management programs (AMPs) to address replacement and monitoring needs as they look to operate for 20 years, and in some cases 40 years, beyond their initial operating lifetimes. For cable insulation and jacket materials that support instrument, control, and safety systems, accelerated aging data are needed to determine priorities in cable aging management programs. Before accelerated thermal and radiation aging of harvested, representative cable insulation and jacket materials, the benchmark performance of a new test capability at Oak Ridge National Laboratory (ORNL) was evaluated for temperatures between 70 and 135 C, dose rates between 100 and 500 Gy/h, and accumulated doses up to 20 kGy, Samples that were characterized and are representative of current materials in use were harvested from the Callaway NPP near Fulton, Missouri, and the San Onofre NPP north of San Diego, California. From the Callaway NPP, a multiconductor control rod cable manufactured by Boston Insulated Wire (BIW), with a Hypalon/ chorolosulfonated polyethylene (CSPE) jacket and ethylene-propylene rubber (EPR) insulation, was harvested from the auxiliary space during a planned outage in 2013. This cable was placed into service when the plant was started in 1984. From the San Onofre NPP, a Rockbestos Firewall III (FRIII) cable with a Hypalon/ CSPE jacket with cross-linked polyethylene (XLPE) insulation was harvested from an on-site, climate-controlled storage area. This conductor, which was never placed into service, was procured around 2007 in anticipation of future operation that did not occur. Benchmark aging for both jacket and insulation material was carried out in air at a temperature of 125 C or in uniform 140 Gy/h gamma irradiation over a period of 60 days. Their mechanical properties over the course of their exposures were compared with reference data from comparable cable jacket/insulation compositions and aging conditions. For both accelerated thermal and radiation aging, it was observed that the mechanical properties for the Callaway BIW control rod cable were consistent with those previously measured. However, for the San Onofre Rockbestos FRIII, there was an observable functional difference for accelerated thermal aging at 125 C. Details on possible sources for this difference and plans for resolving each source are given in this paper.

Duckworth, Robert C↗
DOE OSTI2017

50 MeV Run of the IOTA / FAST Electron Accelerator

The low-energy section of the photoinjector-based electron linear accelerator at the Fermilab Accelerator Science & Technology (FAST) facility was recently commissioned to an energy of 50 MeV. This linear accelerator relies primarily upon pulsed SRF acceleration and an optional bunch compressor to produce a stable beam within a large operational regime in terms of bunch charge, total average charge, bunch length, and beam energy. Various instrumentation was used to characterize fundamental properties of the electron beam including the intensity, stability, emittance, and bunch length. While much of this instrumentation was commissioned in a 20 MeV running period prior, some (including a new Martin- Puplett interferometer) was in development or pending installation at that time. All instrumentation has since been recommissioned over the wide operational range of beam energies up to 50 MeV, intensities up to 4 nC/pulse, and bunch structures from ~1 ps to more than 50 ps in length.

Source record↗
DOE OSTI2018

Muon Acceleration: Neutrino Factory and Beyond

We summarize the current state of a concept for muon acceleration aimed at a future Neutrino Factory and extendable to Higgs Factory. The main thrust of these studies was to reduce the overall cost while maintaining performance by exploring the interplay between the complexity of the cooling systems and the acceptance of the accelerator complex. To ensure adequate survival for the short-lived muons, acceleration must occur at high average gradient. The need for large transverse and longitudinal acceptances drives the design of the acceleration system to an initially low RF frequency, e.g., 325 MHz, which is then increased to 650 MHz as the transverse size shrinks with increasing energy. High-gradient normal conducting RF cavities at these frequencies require extremely high peak-power RF sources. Hence superconducting RF (SRF) cavities are chosen. We consider an SRF-efficient design based on a multi-pass (4.5) ?dogbone? RLA, extendable to multi-pass FFAG-like arcs.

Bogacz, Alex↗
DOE OSTI2019

LONGITUDINAL-PHASE-SPACE MANIPULATION FOR EFFICIENT BEAM-DRIVEN STRUCTURE WAKEFIELD ACCELERATION∗

Collinear beam-driven structure wakefield acceleration (SWFA) is an advanced acceleration technique that could support the compact generation of high-energy beams for future multi-user x-ray free-electron-laser facilities [1]. Producing an ideal shaped drive beam through phase space manipulation is crucial for an efficient SWFA. Controlling the final longitudinal-phase space of the drive beam necessitate staged beam manipulations during acceleration. This paper describes the preliminary design of an accelerator beamline capable of producing drive beam with tailored current distribution and longitudinal-phase-space correlation. The proposed design is based on simple analytical models combined in a 1-D longitudinal beam-dynamics simulation tracking program supporting forward and backward (time reversal) tracking.

wakefield↗
DOE OSTI2019

Performance Improvement of the Linear System Solver for CMFD Acceleration in PROTEUS-MOC

The PROTEUS code developed under the DOE NEAMS program is a high-fidelity capable whole core transports solver based on unstructured finite element meshes [1]. PROTEUS includes three distinct transport solvers: SN, MOC and NODAL. Among them, the PROTEUS-MOC is the 3D method of characteristics (MOC) solver for extruded geometries. In order to accelerate the convergence of 3D MOC calculation, the CMFD acceleration method was implemented in PROTEUS-MOC [2]. For solving the CMFD linear system, the unpreconditioned GMRES algorithm was used in the previous work [3, 4] for implementing the CMFD scheme because of low computation cost of coarse mesh calculations. In the performance tests, we found that the overhead of the CMFD acceleration became non-negligible as the condition number of the CMFD linear system and the size of problem increase. This indicated that the CMFD overhead should be reduced in the preconditioning technique in order to improve the computational performance. In this work, the performance of CMFD acceleration was notably improved by developing and implementing the new formulation of CMFD linear system and preconditioning technique.

Jung, Yeon Sang↗
DOE OSTI2020

Growth and Properties of Vapor Diffused Nb3Sn Coating for Superconducting Radiofrequency Accelerator Cavity Applications

The desire to reduce construction and operating costs of future SRF accelerators motivates the search for higher-performing alternative materials. Nb3Sn (Tc ~ 18.3 K and Hsh ~ 425 mT) is the front runner. The tin vapor diffusion process is currently the technique of choice to produce promising Nb3Sn-coated cavities. Understanding Nb3Sn nucleation and growth in this process is essential to progress. Samples representing different stages of Nb3Sn formation have been produced and studied to elucidate the effects of nucleation, growth, process conditions, and impurities. Nb3Sn films with thickness from a few hundred nm up to ~15 µm were grown and characterized. The microscopic examination of samples suggests the mechanisms of thin film nucleation and growth. Broadly, nucleation deposits tin as a thin surface phase and, under some conditions, a few hundred nanometer sized particles as well. Conditions that impair nucleation promote the formation of defects, such as ?patches?, in subsequent coating growth. Analysis of coated samples is consistent with the model of Nb3Sn grown in which tin diffuses via grain boundaries to Nb3Sn-Nb interface, where the growth Nb3Sn into the niobium bulk takes place. Similar scaling laws are found for grain growth and layer thickness. Non-parabolic layer growth is consistent with significant grain growth, which reduces the number of Sn-transport channels. Examination of patchy region in Nb3Sn coating revealed it to be large single crystalline grains, pointing to impeded Nb3Sn layer growth due to low grain boundary density, resulting in a significantly thin coating in those areas. Examination of RF loss regions from a coated cavity, identified with a thermometry mapping system showed patchy regions and carbonus defects were associated with strong local field-dependent surface resistance. RF measurements of coated cavities were combined with material characterization of witness samples and coated-cavity cutouts to improve the coating process. Understanding obtained and applied to cavity coatings, resulted in single-cell Nb3Sn cavities with a quality factor of ~2 ×1010 up to 15 MV/m accelerating gradient at 4 K, without "Wuppertal" Q-slope. We have also produced Nb3Sn-coated CEBAF 5-cell cavities with accelerating gradients useful for accelerator cryomodules. This dissertation will discuss the genesis of the Nb3Sn coating in a typical tin vapor diffusion process, effects of different process parameters, and its consequences to the coating of single-cell and multi-cell SRF cavities.

Pudasaini, Uttar↗
DOE OSTI2022

US Advanced and Novel Accelerator Beam Test Facilities

Demonstrating the viability of Advanced Accelerator Concepts (AAC) relies on experimental validation. Over the last three decades, the US has maintained a portfolio of advanced and novel accelerator test facilities to support research critical to AAC. The facilities have enabled pioneering developments in a wide variety of beam and accelerator physics, including plasma-wakefeld and structure-wakefeld acceleration. This paper provides an overview of the current portfolio of US facilities possessing charged particle drive beams with high energies, on the order of tens of joules per pulse, or drive lasers with high peak powers, on the order of a petawatt, and are actively conducting AAC research.

Clarke, Christine↗
DOE OSTI2022

Development of Accelerated Steady-state Test Capsule Experiments to Replicate EBR-II Fuel Behavior Using BISON Fuel Performance Analysis

Here in this work, BISON fuel performance calculations were performed to predict the fuel behavior of accelerated burnup U-Pu-Zr fuel, with temperature operation conditions of the fuel and the cladding mirroring conditions within EBR-II fuel pins. The temperature operating conditions within the FAST accelerated burnup rods were aimed at replicating EBR-II X447/X447A fuel surface and inner cladding surface temperatures. Due to the FAST capsule design, these temperatures can be replicated with fission rate densities being significantly increased. fuel performance modeling has not been assessed for novel experiments such as accelerated burnup utilizing the FAST capsule within ATR. This is an important step in understanding accelerated irradiation methods as many performance models are empirical models conforming to the results of PIE but do not always include physical models that would represent the changes in irradiation tests.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Advances in Beam Dynamics at Nuclear Physics Accelerator Facilities

Beam dynamics of particle accelerators is a rich subfield that enables accelerators to be used in pursuit of fundamental topics in particle physics in increasingly complex ways. The field is constantly evolving as new and advanced accelerators push the limits of energy, luminosity, and accelerated species. This talk will cover some recent beam dynamics developments for future operation of DOE nuclear physics user facilities, including upgrade options for Jefferson Lab's 12 GeV CEBAF. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under contract DE-AC05-06OR23177.

Sy, Amy↗
DOE OSTI2023

High Power Targetry R&D and support for future generation accelerator

A high-power target system is a key beam element to complete future High Energy Physics (HEP) experiments. The target endures high power pulsed beam, leading to high cycle thermal stresses/pressures and thermal shocks. The increased beam power will also create significant challenges such as corrosion and radiation damage that can cause harmful effects on the material and degrade their mechanical and thermal properties during irradiation. This can eventually lead to the failure of the material and drastically reduce the lifetime of targets and beam intercepting devices. Designing a reliable target is already a challenge for MW class facilities today and has led several major accelerator facilities to operate at lower power due to target concerns. With present plans to increase beam power for next generation accelerator facilities in the next decade and the multi-year time-scale to acquire the knowledge on material behavior under such extreme environment, timely R&D of robust high-power targets is critical to fully secure the physics benefits of ambitious accelerator power upgrades. The next generation of high-power targets for future accelerators will use more complex geometries, novel materials, and new concepts allowing better high heat flux cooling methods. Advanced numerical simulations need to be developed to satisfy the physical design requirements of reliable beam-intercepting devices. In parallel, radiation hardened beam instrumentation irradiation methods for high-power targets must be further developed. Additional irradiation facilities are needed since only a few facilities worldwide offer beams for target testing, and the beam provided may not be appropriate for the specific facility or project. Thus, a comprehensive research and development program must be implemented to address the challenges that multi-MW targets face.

Pellemoine, F.↗
DOE OSTI2014

Applying Nonlinear Diffusion Acceleration to Fixed-Source Problems with Anisotropic Scattering - Paper 15

Work over the last several years has demonstrated the impressive performance gains that can be attained by using Moment-Based Acceleration (MBA), or High-Order/Low-Order (HOLO), methods in a variety of transport applications. In the field of neutronics, Nonlinear Diffusion Acceleration (NDA) has been used to accelerate the solution to the fixed-source problem and the k-eigenvalue problem. These methods efficiently move a major portion of the computational work out of the full phase-space (high-order (HO)) domain into a reduced phase-space (low-order (LO)) setting. In previous implementations, NDA has only been applied to isotropic scattering problems. In this paper, we will extend this methodology to anisotropic scattering. This initial work on anisotropic scattering will focus on the 1-D multi-group neutron transport equation. This summary focuses on a fixed-source problem, but the extension to criticality problems is straight-forward via NDA-NCA. Within this paper, we have described a method for extending Nonlinear Diffusion Acceleration to solve problems with anisotropic scattering. We demonstrated that a consistent low-order system, resembling the low-order system from, could be constructed. We demonstrated that the NDA method performed exceptionally in the presence of anisotropic scattering. NDA reduced the number of iterations required to meet the convergence tolerance by a factor of 500 over source iteration for a one fixed-source problem and by 3.5-50 x for the Henyey-Greenstein problems. This method is equally well-suited for eigenvalue problems. The NDA method allows us to transition the eigenvalue iteration to the low-order domain.

61 RADIATION PROTECTION AND DOSIMETRY↗