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NASA NTRS1996

High Energy Density Matter for Rocket Propulsion

The objective of the High Energy Density Matter (HEDM) program is to identify, develop, and exploit high energy atomic and molecular systems as energetic sources for rocket propulsion applications. It is a high risk, high payoff program that incorporates both basic and applied research, experimental and theoretical efforts, and science and engineering efforts. The HEDM program is co-sponsored by the Air Force Office of Scientific Research (AFOSR) and the Phillips Laboratory (PURKS). It includes both in-house and contracted University/Industry efforts. Technology developed by the HEDM program offers the opportunity for significant breakthroughs in propulsion system capabilities over the current state-of-the-art. One area of great interest is the use of cryogenic solids to increase the density of the propellant and to act as a stable matrix for storage of energetic materials. No cryogenic solid propellant has ever been used in a rocket, and there remain engineering challenges to such a propellant. However, these solids would enable a wide class of highly energetic materials by providing an environment that is at very low temperatures and is a physical barrier to recombination or energy loss reactions. Previous to our experiments only hydrogen atoms had been isolated in solid hydrogen. To date we have succeeded in trapping B, Al, Li, N, and Mg atoms in solid H2. Small molecules, such as B2 and LiB, are also of interest. Current efforts involve the search for new energetic small molecules, increasing free radical concentrations up to 5 mole percent, and scale-up for propulsion testing.

Carrick, Patrick G.↗

NASA NTRS1993

Status of local oscillators for operating ultra-high resolution frequency discriminators as frequency standards

The operation of new improved frequency standards based on new ultra-high-resolution frequency discriminators requires high stability local, or 'flywheel' oscillators. We review the spectral density of phase fluctuations of existing flywheel oscillators and the related time domain frequency stability of new and proposed cryogenically cooled oscillators suitable for this application. Presently used devices include the quartz crystal oscillator, the room-temperature actively oscillating atomic hydrogen (H) maser, and the superconducting maser oscillator. Future devices include the cryogenic H-maser and other cryogenic devices using resonators of superconducting metal or solid crystalline sapphire. The relation of the phase spectral density of these devices to the characteristics of present and proposed frequency discriminators based on trapped cooled ions and cold atoms is discussed in terms of their operation as frequency standards.

Vessot, R. F. C.↗

DOE OSTI2021

Study of vacuum ultraviolet emission in helium and helium/nitrogen mixtures

Helium is frequently used as a working medium for the generation of plasmas and is capable of energetic photon emissions. These energetic photon emissions are often attributed to the formation of helium excimer and subsequent photon emission. When the plasma device is exposed to another gas, such as nitrogen, this energetic photon emission can cause photoionization and further ionization wave penetration into the additional gas. Often ignored are the helium resonance emissions that are assumed to be radiation trapped and therefore not pertinent to photoionization. Here, experimental evidence for the presence of helium atomic emission in a pulsed discharge at ten’s of Torr is shown. Simulations of a discharge in similar conditions agree with the experimental measurements. In this context, the role of atomic and molecular helium light emission on photoionization of molecular nitrogen in an ionization wave is studied using a kinetic modeling approach that accounts for radiation dynamics in a developing low-temperature plasma. Three different mixtures of helium at a total pressure of 250 Torr are studied in simulation. Photoionization of the nitrogen molecule by vacuum ultraviolet helium emission is used as the only seed source ahead of the ionization front. It is found that even though radiation trapped, the atomic helium emission lines are the significant source of photoionization of nitrogen. The significant effect of radiation trapped photon emission on ionization wave dynamics demonstrates the need to consider these radiation dynamics in plasma reactors where self-absorbed radiation is ignored.

42 ENGINEERING↗

NASA NTRS2004

Performance of the PARCS Testbed Cesium Fountain Frequency Standard

A cesium fountain frequency standard has been developed as a ground testbed for the PARCS (Primary Atomic Reference Clock in Space) experiment, an experiment intended to fly on the International Space Station. We report on the performance of the fountain and describe some of the implementations motivated in large part by flight considerations, but of relevance for ground fountains. In particular, we report on a new technique for delivering cooling and trapping laser beams to the atom collection region, in which a given beam is recirculated three times effectively providing much more optical power than traditional configurations. Allan deviations down to 10 have been achieved with this method.

cesium↗

DOE OSTI2021

Franck-Condon Tuning of Optical Cycling Centers by Organic Functionalization

Laser induced electronic excitations that spontaneously emit photons and decay directly to the initial ground state (“optical cycling transitions”) are used in quantum information and precision measurement for state initialization and readout. To extend this primarily atomic technique to large, organic compounds, we theoretically investigate optical cycling of alkaline earth phenoxides and their functionalized derivatives. We find that optical cycle leakage due to wave function mismatch is low in these species, and can be further suppressed by using chemical substitution to boost the electron-withdrawing strength of the aromatic molecular ligand through resonance and induction effects. This provides a straightforward way to use chemical functional groups to construct optical cycling moieties for laser cooling, state preparation, and quantum measurement.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2026

Noninvasive mid-circuit measurement and reset on atomic qubits

Mid-circuit measurement and reset of subsets of qubits are crucial ingredients of quantum error correction and many quantum information applications. Measurement of atomic qubits is accomplished through resonant fluorescence, which typically disturbs neighboring atoms due to photon scattering. We propose and prototype a scheme for measurement and reset that provides both spatial and spectral isolation by using tightly focused laser beams and narrow atomic transitions. The unique advantage of this scheme is that all operations are applied exclusively to the read-out qubit, with little overhead and negligible disturbance to the other qubits of the same species. In this paper, we pave the way for noninvasive and high-fidelity mid-circuit measurement and demonstrate all key building blocks on a single trapped barium ion.

atomic systems↗

NASA NTRS1999

Proceedings of the 30th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting

This document is a compilation of technical papers presented at the 30th Annual Precise Time and Time Interval (PTTI) Systems and Applications Meeting held 1-3 December 1998 at the Hyatt Regency Hotel at Reston Town Center, Reston, Virginia. Papers are in the following categories: 1) Recent developments in rubidium, cesium, and hydrogen-based atomic frequency standards, and in trapped-ion and space clock technology; 2) National and international applications of PTTI technology with emphasis on GPS and GLONASS timing, atomic time scales, and telecommunications; 3) Applications of PTTI technology to evolving military navigation and communication systems; geodesy; aviation; and pulsars; and 4) Dissemination of precise time and frequency by means of GPS, geosynchronous communication satellites, computer networks, WAAS, and LORAN.

Breakiron, Lee A.↗

DOE OSTI2020

Effect of Confinement of SIA Cluster Diffusion by Impurities on Radiation Defect Accumulation due to 14MeV neutrons in Tungsten

Impurities acting as traps, reduce the self-interstitial atom (SIA) cluster mobility, thereby increasing recombination and in turn enhancing radiation-resistance of polycrystalline materials. However, at elevated temperatures, depending on SIA-trap (impurity) binding energy, SIA clusters may trap and detrap (detach) numerous times. In tungsten, SIA clusters of all sizes glide one-dimensionally (1D) along their Burgers vector direction. Hence, detrapped SIAs would retrace their path, confining their 1D-glide between traps. However, small SIA clusters can change the direction of their 1D-glide by overcoming a rotation barrier. In addition, impurities or solutes are known to reduce this barrier. A lower rotation barrier can result in detrapped SIA clusters that diffuse in a random 1D direction, effectively leading to 3D (net-3D) diffusion. Here we investigate the effect of two cases of SIA diffusion, namely confined-1D diffusion and net-3D diffusion, on the damage accumulation in polycrystalline tungsten under 14 MeV neutron irradiation using the object kinetic Monte Carlo method. Simulations were performed using cascade debris obtained from molecular dynamics simulations with primary knock-on atom (PKA) energies corresponding to 14 MeV neutrons. In the simulations with net-3D diffusion, SIA clusters of all sizes diffuse in a random 1D direction after the clusters detrap. While for the confined 1D diffusion case, SIA clusters larger than size 5 retain their original direction of 1D-glide. In both types of simulations, trapped vacancies are assumed to be permanently immobilized. Unexpectedly, the damage accumulation was lower with confined 1D diffusion than that with net-3D. We present a systematic comparison of the influence of the two cases of SIA diffusion on the radiation damage accumulation as a function of dose rate, detrapping barrier, and impurity concentration at 1025 K.

Accumulation and recovery of lattice damage, tungs↗

NASA NTRS1992

Dual-Ion-Trap Frequency Standards With Overlapping Cycles

Proposed scheme for enhancing performances of atomic frequency-standard apparatuses calls for two or more ion traps per apparatus interrogated in alternation by radio-frequency pulses. Provides nearly constant feedback gain, thereby providing nearly constant corrections for fluctuations in frequency of local oscillator. Degradation of performance by fluctuations in local oscillators reduced.

Dick, G. John↗

NASA NTRS2010

Suppressing Loss of Ions in an Atomic Clock

An improvement has been made in the design of a compact, highly stable mercury- ion clock to suppress a loss of ions as they are transferred between the quadrupole and higher multipole ion traps. Such clocks are being developed for use aboard spacecraft for navigation and planetary radio science. The modification is also applicable to ion clocks operating on Earth: indeed, the success of the modification has been demonstrated in construction and operation of a terrestrial breadboard prototype of the compact, highly stable mercury-ion clock. Selected aspects of the breadboard prototype at different stages of development were described in previous NASA Tech Briefs articles. The following background information is reviewed from previous articles: In this clock as in some prior ion clocks, mercury ions are shuttled between two ion traps, one a 16- pole linear radio-frequency trap, while the other is a quadrupole radio-frequency trap. In the quadrupole trap, ions are tightly confined and optical state selection from a 202Hg lamp is carried out. In the 16-pole trap, the ions are more loosely confined and atomic transitions are interrogated by use of a microwave beam at approximately 40.507 GHz. The trapping of ions effectively eliminates the frequency pulling that would otherwise be caused by collisions between clock atoms and the wall of a gas cell. The shuttling of the ions between the two traps enables separation of the state-selection process from the clock microwave-resonance process, so that each of these processes can be optimized independently of the other. This is similar to the operation of an atomic beam clock, except that with ions the beam can be halted and reversed as ions are shuttled back and forth between the two traps. When the two traps are driven at the same radio frequency, the strength of confinement can be reduced near the junction between the two traps, depending upon the relative phase of the RF voltage used to operate each of the two traps, and can cause loss of ions during each transit between the traps and thereby cause loss of the 40.507-GHz ion-clock resonance signal. The essence of the modification is to drive the two traps at different frequencies typically between 1.5 and 2 MHz for the quadrupole trap and a frequency a few hundred kHz higher for the 16- pole trap. A frequency difference of a few hundred kHz ensures that the ion motion caused by the trapping electric fields is small relative to the diameter of the traps. Unlike in the case in which both traps are driven at the same frequency, the trapping electric fields near the junction are not zero at all times; instead, the regions of low electric field near the junction open and close at the difference frequency. An additional benefit of making the 16-pole trap operate at higher frequency is that the strength or depth of the multipole trap can be increased independent of the quadrupole ion trap.

Prestage, John↗

NASA NTRS1990

State of the art and future directions for the atomic hydrogen maser

The present status of technology development for atomic hydrogen masers (H-masers) is reviewed. The limitations to frequency stability and accuracy are discussed with emphasis on the problems associated with cavity resonator instability and the lack of reproducibility and stability of the storage volume wall coating frequency shift. New types of coating developed in the Soviet Union and better, cavity resonator materials, are expected to make possible frequency at the 10(exp -16) level at 10(exp 4) sec. Better control of systematic effects should extend the long-term stability to levels better than 10(exp -15) for intervals beyond one day. Present use of H-masers as flywheel oscillators in timekeeping systems is discussed as is the outlook for the future cryogenic and room temperature H-masers as flywheel oscillators to operate very high resolution frequency discriminators based on the newly evolving technology of trapped and cooled ions and atoms.

Vessot, Robert F. C.↗

NASA NTRS1990

Energetic neutral atoms: Imaging the magnetospheric ring current

Magnetospheric imaging is a new discipline whose goal is to make pictures of the energetic particle populations trapped in the magnetic field of Earth (or any other planet). This project demonstrated the technical feasibility and scientific validity of magnetospheric imaging using energetic neutral atoms (ENA) with the publication and quantitative analysis of the first ENA images ever obtained from space. ENA's are produced when singly-charged energetic (approximately 100 keV) trapped ions make an atomic collision with the neutral hydrogen atoms which boil of the top of the Earth's atmosphere. These hydrogen atoms suffuse the entire trapping volume of the magnetosphere. The energetic ion steals the electron from the atmospheric hydrogen, so the energetic ion is transformed into an energetic neutral atom with a velocity of several thousands of kilometers/second. Moreover, the new-born ENA preserves the velocity that the trapped ion had at the time of the collision. Consequently, any population of energetic ions emits ENA's.

Roelof, Edmond C.↗

DOE OSTI2026

Hyperfine spectroscopy and laser cooling of the fermionic isotopes 47 Ti and 49 Ti

Here, we report on magneto-optical trapping of the two fermionic isotopes of atomic titanium, 47 Ti and 49 Ti . Unlike the even mass-number isotopes, which were recently laser cooled, 47 Ti and 49 Ti have nonzero nuclear spins and, consequently, their atomic levels are split by hyperfine structure. Combining and comparing theoretical calculations and atomic beam-spectroscopy measurements, we determine the hyperfine structures and isotope shifts of the 3⁢𝑑 2 ⁢4⁢𝑠 2 𝑎 3 ⁢𝐹 4 → 3⁢𝑑 2 ⁢( 3 𝑃)⁢4⁢𝑠⁢4⁢𝑝⁢( 3 𝑃 𝑜 ) 𝑦 5 ⁢𝐷$^o_4$ optical-pumping transition at optical wavelength 391 nm and the 3⁢𝑑 3 ⁢(4𝐹)⁢4⁢𝑠 𝑎 5 ⁢𝐹 5 → 3⁢𝑑 3 ⁢( 4 𝐹)⁢4⁢𝑝 𝑦 5 ⁢𝐺$^𝑜_6$ laser-cooling transition at wavelength 498 nm. With this information, we produce magneto-optical traps of both 47 Ti and 49 Ti by applying two additional tones of light to repump atoms to the maximum-spin states on the laser-cooling transition. Directly loading from the atomic flux of a titanium sublimation pump, we produce 47 Ti and 49 Ti traps with 731(190) and 1142(240) atoms, and with lifetimes of 330⁢(15) and 310⁢(8)⁢ ms, respectively.

atomic spectra↗

DOE OSTI2025

Spin squeezing in an ensemble of nitrogen–vacancy centres in diamond

Spin-squeezed states provide a seminal example of how the structure of quantum mechanical correlations can be controlled to produce metrologically useful entanglement. These squeezed states have been demonstrated in a wide variety of quantum systems ranging from atoms in optical cavities to trapped ion crystals. By contrast, despite their numerous advantages as practical sensors, spin ensembles in solid-state materials have yet to be controlled with sufficient precision to generate targeted entanglement such as spin squeezing. Here we report the experimental demonstration of spin squeezing in a solid-state spin system. Our experiments are performed on a strongly interacting ensemble of nitrogen–vacancy colour centres in diamond at room temperature, and squeezing (−0.50 ± 0.13 dB) below the noise of uncorrelated spins is generated by the native magnetic dipole–dipole interaction between nitrogen–vacancy centres. To generate and detect squeezing in a solid-state spin system, we overcome several challenges. First, we develop an approach, using interaction-enabled noise spectroscopy, to characterize the quantum projection noise in our system without directly resolving the spin probability distribution. Second, noting that the random positioning of spin defects severely limits the generation of spin squeezing, we implement a pair of strategies aimed at isolating the dynamics of a relatively ordered sub-ensemble of nitrogen–vacancy centres. Furthermore, our results open the door to entanglement-enhanced metrology using macroscopic ensembles of optically active spins in solids.

Atomic and molecular physics↗

NASA NTRS1987

Atomic frequency standards for ultra-high-frequency stability

The general features of the Hg-199(+) trapped-ion frequency standard are outlined and compared to other atomic frequency standards, especially the hydrogen maser. The points discussed are those which make the trapped Hg-199(+) standard attractive: high line Q, reduced sensitivity to external magnetic fields, and simplicity of state selection, among others.

Maleki, L.↗

DOE OSTI2023

Deuterium supersaturated surface layer in tungsten: ion energy dependence

Abstract Properties of deuterium (D) supersaturated surface layers (DSSLs) formed in tungsten (W), such as thickness, internal microstructures, and D retention, are experimentally investigated as a function of the incident ion energy, E i . W samples were exposed to D plasmas in the PISCES-A linear plasma device in a range of E i ∼ 45–175 eV, while other plasma exposure parameters were fixed: sample temperature, T s , ∼423 K, ion flux, Γ i , ∼1.2 × 10 21 m −2 s −1 , and fluence, Φ i , ∼3.0 × 10 24 m −2 . High-resolution, cross-sectional, transmission electron microscopy observations confirm that (1) a DSSL forms even at the lowest E i ∼ 45 eV, (2) the DSSL thickness, Δ t DSSL , is found to decrease with decreasing E i from ∼11–12 nm at E i ∼ 175 eV to ∼5–6 nm at ∼45 eV, and to agree with approximately the maximum implantation depth calculated using SDTrimSP, and (3) high-density D nanobubbles with a diameter of ∼1 nm or less exist inside the DSSL, which is deemed to validate a theory-predicted vacancy stabilization process due to trapping of a solute D atom(s). Utilizing a D areal density of ∼4.2 × 10 19 m −2 in the first 14 nm from the surface at E i ∼ 75 eV from nuclear reaction analysis and the measured E i dependence of Δ t DSSL , our previous laser-induced breakdown spectroscopy data is updated: both dynamic and static D retention increase with decreasing E i , and the D/W atomic fraction during plasma exposure reaches ∼0.3 at E i ∼ 45 eV. A possible DSSL formation mechanism is proposed.

Physics↗

DOE OSTI2026

Hybrid Oscillator-Qubit Quantum Processors: Instruction Set Architectures, Abstract Machine Models, and Applications

This tutorial offers a pedagogical guide to hybrid quantum processors that integrate discrete-variable (DV) qubits and continuous-variable (CV) oscillators. Aimed at computer scientists, engineers, and physicists, it provides an overview of the experimental, algorithmic, and architectural aspects of this novel and rapidly developing hardware model. Experimental realizations of this model include superconducting, trapped-ion, and neutral-atom platforms. By combining DV and CV components, hybrid oscillator-qubit processors enable a powerful new paradigm that offers complementary strengths for quantum control, error correction, computation, and simulation. Working toward the goal of a full-stack system connecting applications to CV-DV hardware, we define and formulate abstract machine models and instruction set architectures. These essential abstractions enable codesign of hardware and software, and resource estimation for exploring the potential of current and future hardware for computational and simulation tasks. Using these abstractions, we present both new and existing examples that illustrate the benefits of hybrid CV-DV processors relative to traditional DV-only hardware in computation as well as quantum simulation of physical models. Examples include algorithms for transferring states between DV and CV systems, performing the quantum Fourier transform, and simulation of lattice gauge theories. Relative to qubit-only hardware, the bosonic degrees of freedom natively available in hybrid architectures can substantially reduce the circuit complexity of simulations for physical models containing bosons. A key technique is the extension of quantum signal processing ideas to CV-DV systems. This work is intended to serve as a timely and comprehensive guide to this relatively unexplored yet promising approach to quantum computation and to provide a road map to guide future development.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2021

Trapping interlayer excitons in van der Waals heterostructures by potential arrays

Transition metal dichalcogenide heterostructures can host interlayer excitons (IXs), which consist of electrons and holes spatially separated in different layers. IXs possess permanent dipoles and have proven to offer a wealth of novel physics. Here we develop a discrete, random-walk model which includes annihilation and repulsion interactions among IXs. Using this model, we simulate the trapping of IXs in traps of different depths, densities, and shapes. Our results show that dipole-dipole interactions play an important role in regulating IX trapping. The effects of dipole interactions can be mitigated with small, deep traps which are realizable with atomic defects and moire potentials.

2-dimensional systems↗