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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2026

Optical stochastic cooling at Fermilab’s IOTA ring

Stochastic cooling (SC) constitutes one of the greatest conceptual and technological achievements in particle beam cooling. Numerous SC systems have been built in the microwave regime and used to extend the science reach of accelerator facilities worldwide. The ability to sense and correct the particle ensemble using high-bandwidth feedback systems is at the core of the concept. Here, we describe the first realization of SC at optical frequencies and bandwidths. The demonstration was recently carried out at Fermilab’s integrable optics test accelerator (IOTA) storage ring using the transit-time method of optical stochastic cooling (OSC) and achieved an integrated system bandwidth of approximately 20 THz, which is more than 2000 times that of conventional SC systems. This demonstration establishes the foundation for more advanced OSC experiments with high-gain amplification, currently underway at Fermilab, and the eventual application of OSC to colliders and other accelerator facilities.

Jarvis, Jonathan D. [Fermilab]↗
NASA NTRS1986

Electromagnetic instabilities driven by cool heavy ion beams

The effects of the mass and density of cool, heavy ion beams on the linear and nonlinear characteristics of right-hand resonant and nonresonant electromagnetic ion beam instabilities are analyzed. The magnetic helicity and Alfven speed for a computer simulated complete linear dispersion equation for electromagnetic instabilities are examined. The data reveal that the maximum growth rate of the resonant mode and the threshold velocity of the nonresonant mode decrease with beam mass; however, the maximum growth rate of the nonresonant mode and the threshold velocity of the resonant mode are independent of the beam mass. The role reversal of the instabilities which occur when a heavy ion beam is the more dense component is studied. The nonlinear behavior of the instabilities is described; variations in the magnetic field fluctuation levels and the beam mass dependence are investigated. It is observed that at low beam density the magnetic field fluctuation level increases with beam mass and at higher beam density the fluctuation level correlates with the core mass. The instability data are applied to observations of Venus and the Comet Giacobini-Zinner.

Winske, D.↗
DOE OSTI2021

Design of a compact, cryogen-free superconducting solenoid for the electron lens of the Fermilab Integrable Optics Test Accelerator (IOTA)

The proposed electron lens for Fermilab's Integrable Optics Test Accelerator (IOTA) will broaden its capabilities by enabling new research in nonlinear integrable optics, space-charge compensation, proton beam cooling, and more. The electron lens is based on a 5–10 keV, 1–2 A electron beam, shaped using a 0.7 m long, 0.8 T solenoidal magnetic field. A cryogen-free superconducting solenoid has been designed to provide this solenoidal field, taking into consideration the constraints on space, utilities, and infrastructure in the IOTA experimental hall. The solenoid is made of copper stabilized niobium-titanium conductor, conduction-cooled using 4 K closed-cycle cryocoolers. This paper describes the overall design of the solenoid encompassing its mechanical construction, current leads optimization, cryogenic thermal modeling that provides estimates of cooldown time and static/dynamic heat loads, and quench analysis.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

Demonstration of Electron Cooling using a Pulsed Beam from an Electrostatic Electron Cooler

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings in cases where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics *. We show the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate the detrimental effect of timing jitter as predicted by theory and simulations. Compared to actual RF-based coolers, the simplicity and flexibility of our setup will facilitate further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering.

Bruker, M. W.↗
DOE OSTI2021

Demonstration of Electron Cooling using a Pulsed Beam from an Electrostatic Electron Cooler

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings in cases where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics *. We show the effect of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrate the detrimental effect of timing jitter as predicted by theory and simulations. Compared to actual RF-based coolers, the simplicity and flexibility of our setup will facilitate further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering.

Bruker, M. W.↗
NASA NTRS1990

The status of cesium beam frequency standards

There has been a lot of progress in cesium beam frequency standards in the last few years some of which will be reported here. Optical pumping is being pursued actively in a number of laboratories. Optically slowed and cooled beams have been demonstrated as well as traps for cold neutral atoms. The microwave cavity performance with regard to local phase shift at the beam holes was improved by use of carefully designed and built ring structures for the cavity ends. Work is being done on improvements in electronics with some emphasis on use of digital circuitry and microprocessors. The frequency pulling due to microwave Delta M = +/- 1 transitions (Ramsey pulling) was analyzed and shown to be important. Status of cesium beam frequency standards in some of the laboratories as well as some of the commercial work is discussed. Optical pumping and detection are discussed.

Cutler, Leonard S.↗
DOE OSTI2022

A compact cold-atom interferometer with a high data-rate grating magneto-optical trap and a photonic-integrated-circuit-compatible laser system

Abstract The extreme miniaturization of a cold-atom interferometer accelerometer requires the development of novel technologies and architectures for the interferometer subsystems. Here, we describe several component technologies and a laser system architecture to enable a path to such miniaturization. We developed a custom, compact titanium vacuum package containing a microfabricated grating chip for a tetrahedral grating magneto-optical trap (GMOT) using a single cooling beam. In addition, we designed a multi-channel photonic-integrated-circuit-compatible laser system implemented with a single seed laser and single sideband modulators in a time-multiplexed manner, reducing the number of optical channels connected to the sensor head. In a compact sensor head containing the vacuum package, sub-Doppler cooling in the GMOT produces 15 μK temperatures, and the GMOT can operate at a 20 Hz data rate. We validated the atomic coherence with Ramsey interferometry using microwave spectroscopy, then demonstrated a light-pulse atom interferometer in a gravimeter configuration for a 10 Hz measurement data rate and T = 0–4.5 ms interrogation time, resulting in Δ g / g = 2.0 × 10 −6 . This work represents a significant step towards deployable cold-atom inertial sensors under large amplitude motional dynamics.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2023

Theory of photoemission from cathodes with disordered surfaces

Linear-accelerator-based applications like x-ray free electron lasers, ultrafast electron diffraction, electron beam cooling, and energy recovery linacs use photoemission-based cathodes in photoinjectors for electron sources. Most of these photocathodes are typically grown as polycrystalline materials with disordered surfaces. In order to understand the mechanism of photoemission from such cathodes and completely exploit their photoemissive properties, it is important to develop a photoemission formalism that properly describes the subtleties of these cathodes. Here, the Dowell–Schmerge (D–S) model often used to describe the properties of such cathodes gives the correct trends for photoemission properties like the quantum efficiency (QE) and the mean transverse energy (MTE) for metals; however, it is based on several unphysical assumptions. In the present work, we use Spicer’s three-step photoemission formalism to develop a photoemission model that results in the same trends for QE and MTE as the D–S model without the need for any unphysical assumptions and is applicable to defective thin-film semiconductor cathodes along with metal cathodes. As an example, we apply our model to Cs 3 Sb thin films and show that their near-threshold QE and MTE performance is largely explained by the exponentially decaying defect density of states near the valence band maximum.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

Spin-dependent scattering of sub-GeV dark matter: Models and constraints

We calculate the scattering rate of sub-GeV dark matter in solid-state targets for spin-dependent dark matter–nucleon interactions. For dark matter particles with mass below 100 MeV, the scattering occurs predominantly through incoherent phonon production. For dark matter heavier than 100 MeV, we match onto the nuclear recoil calculation. To compare the sensitivity of future direct detection experiments with existing constraints, we consider three models with interactions that are mediated by spin-0 or spin-1 particles. This allows us to derive bounds on the cross section from searches for the mediating particle, including bounds from stellar cooling, beam dump experiments, meson factories, and dark matter self-interactions. The existing bounds are very stringent, though for 𝑚 𝜒 ≳100 MeV there is parameter space, which may be accessible with direct detection, depending on the exposure and background rates.

Gori, Stefania [University of California, Santa Cr↗
DOE OSTI2022

Gold-gold luminosity increase in RHIC for a beam energy scan with colliding beam energies extending below the nominal injection energy

The Beam Energy Scan phase II (BES-II), performed in the Relativistic Heavy Ion Collider (RHIC) from 2019 to 2021, explored the phase transition between quark-gluon plasma and hadronic gas. BES-II exceeded the goal of a fourfold increase in the average luminosity over that achieved during Beam Energy Scan phase I (BES-I), at five gold beam energies: 9.8, 7.3, 5.75, 4.59, and 3.85 GeV / nucleon. This was accomplished by addressing several beam dynamics effects, including intrabeam scattering, beam-beam, space charge, beam instability, and field errors induced by superconducting magnet persistent currents. Some of these effects are especially detrimental at low energies. BES-II achievements are presented, and the measures taken to improve RHIC performance are described. These measures span the whole RHIC complex, including ion beam sources, injectors, beam lifetime improvements in RHIC, and operation with the world’s first bunched beam Low Energy RHIC electron Cooler (LEReC).

43 PARTICLE ACCELERATORS↗
DOE OSTI2024

Preliminary Transverse Shielding Analysis for the 1010-C RF Building

EIC is planning to construct a new building on the outer ring berm at 10 o’clock which will provide RF power to cryogenically-cooled beam line components in the electron and hadron storage rings. The distance of the building from the RHIC Tunnel and the amount of soil shielding required are the focus of this report. Siting the building closer to the RHIC Tunnel is desirable from an RF operations viewpoint since the waveguide runs and RF power losses will be minimized, but this may require the use of higher density shield materials, e.g., concrete, in addition to soil shielding. The radiological source terms are the prompt radiation hazards from the Hadron Storage Ring (HSR) and Electron Storage Ring (ESR) beam losses in the 10 o’clock sector and the lateral dose rates propagated through the shields. See Figure 1 below.

43 PARTICLE ACCELERATORS↗
NASA NTRS1990

Theoretical study of the spectroscopy of Al2

The present study of the singlet and triplet states of Al2 below about 30,000/cm at the multireference configuration-interaction level attempts to identify and characterize the band systems in both the singlet and triplet manifolds. The spectroscopy of Al2 can be understood in terms of an X 3Pi(u) ground state. Calculations suggest that the assignments of the E and F systems recently noted in a jet-cooled beam are correct, although remaining differences between theoretical and experimental spectroscopic constants and radiative lifetimes preclude a definitive assignment.

Langhoff, Stephen R.↗
DOE OSTI2024

Suspended waveguides on membrane and needle structures towards photonic atom trap integrated platforms

An atom trap integrated platform (ATIP) comprises a substrate, a membrane, and a suspended waveguide. The substrate has an opening formed therein. The membrane extends across a portion of the substrate opening. The suspended waveguide is formed on the membrane such that the suspended waveguide extends from a first edge of the substrate to a second edge. A magneto-optical trap (MOT) is formed around the suspended waveguide by emitting a plurality of cooling beams and a repump through the substrate opening. Evanescent fields are established above the suspended waveguide by coupling two trapping beams through the suspended waveguide, which trapping beams are red-detuned and blue-detuned with respect to the resonant optical transition of the atoms. By forming the MOT within the evanescent fields, an evanescent field optical trap (EFOT) is formed.

Lee, Jongmin↗
DOE OSTI2021

Photoinjector Generation of High-Charge Magnetized Beams for Electron-Cooling Applications

The recently announced Electron-Ion Collider (EIC), to be built at Brookhaven National Laboratory, will collide high-energy ion-beams and electron beams to pursue nuclear physics research on quark-gluon plasma's. The facility performances (luminosity) would be improved if the ion-beam emittance degradation is mitigated via a phase-space-cooling technique. One potential cooling method uses a bright electron beam to cool the ion beams. The cooling rate for this electron-cooling method depends on the transverse emittance of the cooling electron beam and could benefit from using a beam with significant canonical angular momentum dubbed as a magnetized beam. This research focuses on simulation and experimental generation and characterization of high charge magnetized electron beams with parameters comparable to those required for electron cooling at an electron-ion collider. The experiment uses the 50-MeV photo-injector available at the Fermilab Accelerator Science and Technology (FAST) Facility. The measurements are benchmarked against simulations.

43 PARTICLE ACCELERATORS↗
DOE OSTI2022

Electron Cooling Experiment for Proton Beams with Intense Space-Charge in IOTA

Electron cooling as a method of creating intense ion beams has a practical upper limit when it comes to the peak phase space density of ion beams which can be achieved in practice. We describe a new experiment to study electron cooling of 2.5 MeV protons at the intensity limit using the Integrable Optics Test Accelerator (IOTA), which is a storage ring dedicated to beam physics research at Fermilab. This system will enable the study of magnetized electron cooling of a proton beam with transverse incoherent tune shifts approaching -0.5 due to the presence of intense space-charge forces. We present an overview of the hardware design, simulations and specific experiments planned for this project.

43 PARTICLE ACCELERATORS↗
DOE OSTI2021

ELECTRON COOLING USING A PULSED AND DITHERING BEAM FROM AN ELECTROSTATIC ELECTRON COOLER

Electron cooling continues to be an invaluable technique to reduce and maintain the emittance in hadron storage rings such as the EIC and EICC where stochastic cooling is inefficient and radiative cooling is negligible. Extending the energy range of electron coolers beyond what is feasible with the conventional, electrostatic approach necessitates the use of RF fields for acceleration and, thus, a bunched electron beam. To experimentally investigate how the relative time structure of the two beams affects the cooling properties, we have set up a pulsed-beam cooling device by adding a synchronized pulsing circuit to the conventional electron source of the CSRm cooler at Institute of Modern Physics. Using both constant and modulated synchronization between electron pulses and ion bunches, we have measured the effects of the electron bunch length and longitudinal ion focusing strength on the temporal evolution of the longitudinal and transverse ion beam profile and demonstrated the detrimental effect of timing jitter as predicted by space-charge theory and simulations. Our experiment suggests a need for further investigations of specific aspects of bunched cooling such as synchro-betatron coupling and phase dithering effects when using short electron bunches to cool longer ion bunches. However, given the comparatively long IBS lifetime of higher-energy proton storage rings like the EIC, slow dithering could potentially provide an option to save cost on the electron cooler linac.

Wang, Haipeng↗