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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 649 records · Page 36
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Magnetic Measurement With Single Stretched Wire Method on SuperKEKB Final Focus Quadrupoles

Superconducting-final-focus-quadrupole magnet system (QCS) were installed on an interaction region (IR) of SuperKEKB on Feb. 2017. The QCS consists of eight quadrupole magnets and four compensation solenoids; these magnets are contained in the two cryostats and are installed into Belle II detector which generates a solenoid field of 1.5 T. We determined the quadrupole centers with respect to accelerator beam lines with a single stretched wire (SSW) method. Here the results of the magnetic measurement with SSW are presented.

43 PARTICLE ACCELERATORS↗
DOE OSTI2013

Interaction of energetic particles with waves in strongly inhomogeneous solar wind plasmas

Observations performed in the solar wind by different satellites show that electron beams accelerated in the low corona during solar flares can propagate up to distances around 1 AU, that Langmuir waves' packets can be clumped into spikes with peak amplitudes three orders of magnitude above the mean, and that the average level of density fluctuations can reach several percents. A Hamiltonian model is built describing the properties of Langmuir waves propagating in a plasma with random density fluctuations by the Zakharov's equations and the beam by means of particles moving self-consistently in the fields of the waves. Numerical simulations, performed using parameters relevant to solar type III conditions at 1 AU, show that when the average level of density fluctuations is sufficiently low, the beam relaxation and the wave excitation processes are very similar to those in a homogeneous plasma and can be described by the quasilinear equations of the weak turbulence theory. On the contrary, when the average level of density fluctuations overcomes some threshold depending on the ratio of the thermal velocity to the beam velocity, the plasma inhomogeneities crucially influence the characteristics of the Langmuir turbulence and the beam-plasma interaction.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

CHARACTERIZATION OF RADIATION DAMAGES TO POSITRON SOURCE MATERIALS

The secondary beam production target at future positron sources at the Continuous Electron Beam Accelerator Facility (CEBAF), the International Linear Collider (ILC) or the Future Circular Collider (FCC), features unprecedented mechanical and thermal stresses which may compromise sustainable and reliable operation. Candidate materials are required to possess high melting temperature together with excellent thermal conductivity, elasticity and radiation hardness properties. In order to substantiate the material choice for the CEBAF and ILC positron sources, the response of candidate materials such as titanium alloys, tungsten, and tantalum to electron beam irradiation was experimentally investigated. CEBAF and ILC expected operating conditions were mimicked using the 3.5 MeV electron beam of the MAMI facility injector. The material degradations were precisely analyzed via high energy X-ray diffraction at the HEMS beamline operated by the Helmholtz-Zentrum Hereon at the PETRA III synchrotron facility. This work reports the results of these measurements and their interpretation.

Lengler, T.↗
DOE OSTI2022

CEBAF Injector Model for KL Beam Conditions

The Jefferson Lab KL experiment will run at the Continuous Electron Beam Accelerator Facility with a much lower bunch repetition rate (7.80 or 15.59 MHz) than nominally used (249.5 or 499 MHz). While the proposed average current of 2.5 - 5.0 muA is relatively low compared to the maximum CEBAF current of approximately 180 muA, the corresponding bunch charge is atypically high for CEBAF injector operation. In this work, we investigated the evolution and transmission of low-rep-rate, high-bunch-charge (0.32 to 0.64 pC) beams through the CEBAF injector. Using the commercial software General Particle Tracer, we have simulated and analyzed the beam characteristics for both values of bunch charge. We performed these simulations with the existing injector using a 130 kV gun voltage. We have calculated and measured the transmission as a function of the photocathode laser spot size and pulse length. We report on the findings of these simulations and optimum parameters for operating the experiment.

Pokharel, Sunil↗
DOE OSTI2022

Photoemission characterization of N-polar III-nitride photocathodes as candidate bright electron beam sources for accelerator applications

We report on the growth and characterization of a new class of photocathode structures for use as electron sources to produce high brightness electron beams for accelerator applications. The sources are realized using III-nitride materials and are designed to leverage the strong polarization field, which is characteristic of this class of materials when grown in their wurtzite crystal structure, to produce a negative electron affinity condition without the use of Cs, possibly allowing these materials to be operated in radio frequency guns. A Quantum Efficiency (QE) of about 1×10−3 and an emitted electrons’ Mean Transverse Energy (MTE) of about 100 meV are measured at a wavelength of 265 nm. In a vacuum level of 3×10−10 Torr, the QE does not decrease after more than 24 h of continuous operation. The lowest MTE of about 50 meV is measured at 300 nm along with a QE of 1.5×10−5. Surface characterizations reveal a possible contribution to the MTE from surface morphology, calling for more detailed studies.

Cultrera, L. (ORCID:0000000235606059)↗
DOE OSTI2019

Precise and ultra-stable laser polarization control for polarized electron beam generation

Parity-violating scattering of helicity-flipping polarized electron beam has developed over the past decades into a key tool to study both the structure of electroweak interaction and the structure of nucleons. It has been used in the success of many nuclear physics programs such as HAPPEX in Jefferson Lab’s Continuous Electron Beam Accelerator Facility (CEBAF). The helicity-flipping polarized electrons are generated by using circular polarized laser whose polarization is flipped by a polarization controller. Raytum Photonics will develop a precise and ultra-stable circular laser polarization flipping system. This system uses our state-of-art transverse dual DKDP crystal modulator driven by our innovative digital voltage switching driver. It will help to achieve the objectives specified in the topic 29e to develop polarized electron beam sources with high flipping frequency (<2 kHz) and very small helicity-correlation changes in beam parameters. In Phase I, we developed the dual DKDP crystal modulator and the voltage switching driver. The performance of the modulator met almost all of the specifications proposed in Phase I proposal. We also built a bench top laser polarization flipping system and performed laser-table study in beam laboratory of physics department at University of Virginia and demonstrated the system’s potential to meet high precision for next generation parity-violating experiment such as MOLLER experiment.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

Beam emittance preservation using Gaussian density ramps in a beam-driven plasma wakefield accelerator

A current challenge that is facing the plasma wakefield accelerator (PWFA) community is transverse beam emittance preservation. This can be achieved by balancing the natural divergence of the beam against the strong focusing force provided by the PWFA plasma source in a scheme referred to as beam matching. One method to accomplish beam matching is through the gradual focusing of a beam with a plasma density ramp leading into the bulk plasma. Here, the beam dynamics in a Gaussian plasma density ramp are considered, and an empirical formula is identified that gives the ramp length and beam vacuum waist location needed to achieve near-perfect matching. The method uses only the beam vacuum waist beta function as an input. Numerical studies show that the Gaussian ramp focusing formula is robust for beta function demagnification factors spanning more than an order of magnitude with experimentally favourable tolerances for future PWFA research facilities. This article is part of the Theo Murphy meeting issue ‘Directions in particle beam-driven plasma wakefield acceleration’.

43 PARTICLE ACCELERATORS↗
NASA NTRS1982

Observations of gyrating ions in the foot of the nearly perpendicular bow shock

A beam of secondary ions which gyrate about the magnetic field have been detected by ISEE-1 satellite measurements of ion velocity distributions during a high Mach number bow shock crossing under nearly perpendicular conditions. The ions are encountered as the satellite enters the region ahead of the foot of the shock, and their behavior is that of solar wind ions reflected off the shock and then returned to it under the combined influence of magnetic field deflection and interplanetary electric field acceleration. Beam densities increase from 0.2 to 30% of the total plasma density as the main shock is approached, and the ion beam is not degraded through interaction with the counterstreaming solar wind upstream of the ramp. The gyrating ions provide strong dispersion in velocity space, and therefore constitute the first step in the process by which solar wind streaming energy is converted into the thermal energy of the ions at the bow shock.

Paschmann, G.↗
DOE OSTI2016

ION BEAM POLARIZATION DYNAMICS IN THE 8 GEV BOOSTER OF THE JLEIC PROJECT AT JLAB

In the Jefferson Lab’s Electron-Ion Collider (JLEIC) project, an injector of polarized ions into the collider ring is a superconducting 8 GeV booster. Both figure-8 and racetrack booster versions were considered. Our analysis showed that the figure-8 ring configuration allows one to preserve the polarization of any ion species during beam acceleration using only small longitudinal field with an integral less than 0.5 Tm. In the racetrack booster, to pre-serve the polarization of ions with the exception of deu-terons, it suffices to use a solenoidal Siberian snake with a maximum field integral of 30 Tm. To preserve deuteron polarization, we propose to use arc magnets for the race-track booster structure with a field ramp rate of the order of 1 T/s. We calculate deuteron and proton beam polari-zations in both the figure-8 and racetrack boosters includ-ing alignment errors of their magnetic elements using the Zgoubi code.

Kondratenko, A. M.↗
DOE OSTI2016

The JLab TMD Program at 6 GeV and 11 GeV

The precise mapping of the nucleon’s transverse momentum dependent parton distributions (TMDs) in the valence quark region has emerged as one of the flagship physics programs of the recently upgraded Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab (JLab). The TMDs describe the three-dimensional, spin-correlated densities of quarks and gluons in the nucleon in momentum space, and are accessible experimentally through detailed studies of the Semi-Inclusive Deep Inelastic Scattering (SIDIS) process, N ( e ; e 0 h ) X . The already unrivaled intensity, polarization and duty factor performance of CEBAF will combine with the dramatic expansion of its kinematic reach embodied by the recent near-doubling of the maximum beam energy to enable the first fully differential precision measurements of SIDIS structure functions in the valence region. In this paper, I will review the existing and forthcoming SIDIS results from the 6 GeV era of CEBAF operations and present an overview of the planned JLab SIDIS program at 11 GeV beam energy

Puckett, Andrew J.↗
DOE OSTI2011

MULTISLICE SIMULATION OF TRANSMISSION ELECTRON MICROSCOPY IMAGING OF HELIUM BUBBLES IN IRON

The objective of this task is to establish the size correlation between transmission electron microscopy (TEM) imaged helium (He) bubbles and the actual bubbles in an iron (Fe) matrix. SUMMARY The results of this simulation study show that the size of TEM imaged He bubbles, represented by the inner diameter of the first dark Fresnel ring under defocused condition (Din), deviated from the actual bubble size (Do). Din was found to be larger than Do when imaged with a highly incoherent electron beam, but smaller than Do if the beam is coherent. The deviation of Din from Do increases with increasing defocus. On the other hand, the electron beam accelerating voltage, bubble size, bubble position, and TEM sample thickness do not significantly affect the value of D0/Do. This study also suggests that He bubbles can be differentiated from argon (Ar) bubbles by differences in Fresnel contrast.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Meson Spectroscopy At Jlab At 12 Gev

The 12 GeV upgrade to the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab will enable a new generation of experiments in hadronic nuclear physics, seeking to address fundamental questions in our understanding of QCD. The existence of exotic states, suggested by both quark models and lattice calculations, would allow gluonic degrees of freedom to be explored, and may help explain the role played by gluons in the QCD interaction. This article will review the meson spectroscopy program being planned at the lab following the 12 GeV upgrade, utilising real and quasi-real photon beams in two of the lab's four experimental halls, whose distinct capabilities will enable an extensive set of spectroscopy experiments to be performed at the same facility.

Fegan, Stuart↗
DOE OSTI2015

Exploration of multi-fold symmetry element-loaded superconducting radio frequency structure for reliable acceleration of low- & medium-beta ion species

Reliable acceleration of low- to medium-beta proton or heavy ion species is needed for future high-current superconducting radio frequency (SRF) accelerators. Due to the high-Q nature of an SRF resonator, it is sensitive to many factors such as electron loading (from either the accelerated beam or from parasitic field emitted electrons), mechanical vibration, and liquid helium bath pressure fluctuation etc. To increase the stability against those factors, a mechanically strong and stable RF structure is desirable. Guided by this consideration, multi-fold symmetry element-loaded SRF structures (MFSEL), cylindrical tanks with multiple (n>=3) rod-shaped radial elements, are being explored. The top goal of its optimization is to improve mechanical stability. A natural consequence of this structure is a lowered ratio of the peak surface electromagnetic field to the acceleration gradient as compared to the traditional spoke cavity. A disadvantage of this new structure is an increased size for a fixed resonant frequency and optimal beta. This paper describes the optimization of the electro-magnetic (EM) design and preliminary mechanical analysis for such structures.

43 PARTICLE ACCELERATORS↗
DOE OSTI2017

The large-area hybrid-optics RICH detector for the CLAS12 spectrometer

A large area ring-imaging Cherenkov detector has been designed to provide clean hadron identification capability in the momentum range from 3 GeV/c to 8 GeV/c for the CLAS12 experiments at the upgraded 12 GeV continuous electron beam accelerator facility of Jefferson Lab to study the 3D nucleon structure in the yet poorly explored valence region by deep-inelastic scattering, and to perform precision measurements in hadronization and hadron spectroscopy. The adopted solution foresees a novel hybrid optics design based on an aerogel radiator, composite mirrors and densely packed and highly segmented photon detectors. Cherenkov light will either be imaged directly (forward tracks) or after two mirror reflections (large angle tracks). Finally, the preliminary results of individual detector component tests and of the prototype performance at test-beams are reported here.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1996

Petabyte Class Storage at Jefferson Lab (CEBAF)

By 1997, the Thomas Jefferson National Accelerator Facility will collect over one Terabyte of raw information per day of Accelerator operation from three concurrently operating Experimental Halls. When post-processing is included, roughly 250 TB of raw and formatted experimental data will be generated each year. By the year 2000, a total of one Petabyte will be stored on-line. Critical to the experimental program at Jefferson Lab (JLab) is the networking and computational capability to collect, store, retrieve, and reconstruct data on this scale. The design criteria include support of a raw data stream of 10-12 MB/second from Experimental Hall B, which will operate the CEBAF (Continuous Electron Beam Accelerator Facility) Large Acceptance Spectrometer (CLAS). Keeping up with this data stream implies design strategies that provide storage guarantees during accelerator operation, minimize the number of times data is buffered allow seamless access to specific data sets for the researcher, synchronize data retrievals with the scheduling of postprocessing calculations on the data reconstruction CPU farms, as well as support the site capability to perform data reconstruction and reduction at the same overall rate at which new data is being collected. The current implementation employs state-of-the-art StorageTek Redwood tape drives and robotics library integrated with the Open Storage Manager (OSM) Hierarchical Storage Management software (Computer Associates, International), the use of Fibre Channel RAID disks dual-ported between Sun Microsystems SMP servers, and a network-based interface to a 10,000 SPECint92 data processing CPU farm. Issues of efficiency, scalability, and manageability will become critical to meet the year 2000 requirements for a Petabyte of near-line storage interfaced to over 30,000 SPECint92 of data processing power.

Chambers, Rita↗
DOE OSTI2015

Transportation of high-current ion and electron beams in the accelerator drift gap in the presence of an additional electron background

The dynamics of a high-current ion beam propagating in the drift gap of a linear induction accelerator with collective focusing is studied using 3D numerical simulations in the framework of the full system of the Vlasov–Maxwell equations (code KARAT). The ion beam is neutralized by a comoving electron beam in the current density and, partially, in space charge, since the velocities of electrons and ions differ substantially. The dynamics of the high-current ion beam is investigated for different versions of additional neutralization of its space charge. It is established that, for a given configuration of the magnetic field and in the presence of a specially programmed injection of additional electrons from the boundary opposite to the ion injection boundary, the angular divergence of the ion beam almost vanishes, whereas the current of the ion beam at the exit from the accelerator drift gap changes insignificantly and the beam remains almost monoenergetic.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2024

Radial Variations in Solar Type III Radio Bursts

Type III radio bursts are generated by electron beams accelerated at reconnection sites in the corona. This study, utilizing data from the Parker Solar Probe's first 17 encounters, closely examines these bursts down to 13 solar radii. A focal point of our analysis is the near-radial alignment (within 5°) of the Parker Solar Probe, STEREO-A, and Wind spacecraft relative to the Sun. This alignment, facilitating simultaneous observations of 52 and 27 bursts by STEREO-A and Wind respectively, allows for a detailed differentiation of radial and longitudinal burst variations. Our observations reveal no significant radial variations in electron beam speeds, radio fluxes, or exponential decay times for events below 50 solar radii. In contrast, closer to the Sun we noted a decrease in beam speeds and radio fluxes. This suggests potential effects of radio beaming or alterations in radio source sizes in this region. Importantly, our results underscore the necessity of considering spacecraft distance in multispacecraft observations for accurate radio burst analysis. A critical threshold of 50 solar radii emerges, beyond which beaming effects and changes in beam speeds and radio fluxes become significant. Furthermore, the consistent decay times across varying radial distances point toward a stable trend extending from 13 solar radii into the inner heliosphere. Our statistical results provide valuable insights into the propagation mechanisms of type III radio bursts, particularly highlighting the role of scattering near the radio source when the frequency aligns with the local electron plasma frequency.

Vratislav Krupar↗
DOE OSTI2017

Resonance Control System for the CEBAF Separator Upgrade

Abstract The Continuous Electron Beam Accelerator Facility (CEBAF) energy upgrade from 6 GeV to 12 GeV includes the installation of four new 748.5 MHz normal conducting deflecting cavities in the 5th pass extraction region. The RF system employs two digital LLRF systems controlling four normal conducting cavities in a vector sum setting. Cavity tune information of the individual cavities is obtained using a multiplexing scheme of the forward and reflected RF signals. Water skids equipped with heaters and valves are used to control resonance. A new FPGA-based hardware and EPICS-based predictive control algorithm has been developed to support reliable operation of the beam extraction process. This paper presents the architecture design of the existing hardware and software as well as a plan to develop a model predictive control system.

Plawski, Tomasz↗