SEARCH · Engineering Papers

Results for “vacuum break”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9

All sources NASA NTRS DOE OSTI

NASA NTRS2014

High-Energy Pulsar Models: Developments and New Questions

The past few years have seen a major advance in observational knowledge of high-energy (HE) pulsars. The Fermi Large Area Telescope (LAT) and AGILE have increased the number of known gamma-ray pulsars by an order of magnitude, its members being divided roughly equally among millisecond pulsars (MSPs), young radio-loud pulsars, and young radio-quiet pulsars. Many new and diverse emission characteristics are being measured, while radio and X-ray follow-up observations increase the pulsar detection rate and enrich our multiwavelength picture of these extreme sources. The wealth of new data has provided impetus for further development and improvement of existing theoretical pulsar models. Geometric light curve (LC) modelling has uncovered three broad classes into which HE pulsars fall: those where the radio profile leads, is aligned with, or lags the gamma-ray profile. For example, the original MSP and original black widow system are members of the second class, requiring co-located emission regions and thereby breaking with traditional notions of radio emission origin. These models imply narrow accelerator gaps in the outer magnetosphere, indicating copious pair production even in MSP magnetospheres that were previously thought to be pair-starved. The increased quality and variety of the LCs necessitate construction of ever more sophisticated models. We will review progress in global magnetosphere solutions which specify a finite conductivity on field lines above the stellar surface, filling the gap between the standard vacuum and force-free (FF; plasma-filled) models. The possibility of deriving phase-resolved spectra for the brightest pulsars, coupled with the fact that the HE pulsar population is sizable enough to allow sampling of various pulsar geometries, will enable much more stringent testing of future radiation models. Reproduction of the observed phase-resolved behavior of this disparate group will be one of the next frontiers in pulsar science, impacting on our understanding of particle acceleration, emission, and magnetosphere geometry. One may now also study evolutionary trends of the measured or inferred quantities, and probe pulsar visibility and population properties such as radiation beam sizes of different pulsar classes, as well as the distribution of spin-down power, gamma-ray luminosity, conversion efficiency, spectral index, and cutoff energy across the population. Lastly, the recent detection of very-high-energy (VHE) pulsations from the Crab pulsar generated quite a few ideas to explain this emission, leading to an extension of standard models and possibly even a bridge between the physics of pulsars and pulsar wind nebulae (PWNe).

gamma rays:↗

DOE OSTI2021

Casimir Light in Dispersive Nanophotonics

Time-varying optical media, whose dielectric properties are actively modulated in time, introduce a host of novel effects in the classical propagation of light, and are of intense current interest. In the quantum domain, time-dependent media can be used to convert vacuum fluctuations (virtual photons) into pairs of real photons. Here, we refer to these processes broadly as “dynamical vacuum effects” (DVEs). Despite interest for their potential applications as sources of quantum light, DVEs are generally very weak, presenting many opportunities for enhancement through modern techniques in nanophotonics, such as using media which support excitations such as plasmon and phonon polaritons. Here, we present a theory of weakly modulated DVEs in arbitrary nanostructured, dispersive, and dissipative systems. A key element of our framework is the simultaneous incorporation of time-modulation and “dispersion” through time-translation-breaking linear response theory. As an example, we use our approach to propose a highly efficient scheme for generating entangled surface polaritons based on time-modulation of the optical phonon frequency of a polar insulator.

42 ENGINEERING↗

DOE OSTI2022

Semiclassics with ’t Hooft flux background for QCD with 2-index quarks

We study quantum chromodynamics including the two-index symmetric or anti-symmetric quark (QCD(Sym/ASym)) on small $\mathbb{R}^2$× T 2 with a suitable magnetic flux. We first discuss the ’t Hooft anomaly of these theories and claim that discrete chiral symmetry should be spontaneously broken completely to satisfy the anomaly matching condition. The T 2 compactification with the magnetic flux preserves the ’t Hooft anomaly, and the 2d effective theory is constrained by the same anomaly of 4d QCD(Sym/ASym). We demonstrate the spontaneous breakdown of chiral symmetry using the dilute gas of center vortices, which confirms the prediction of the ’t Hooft anomaly. We also find that each vacuum maintains the charge conjugation symmetry, and this gives affirmative support for the nonperturbative large-N orientifold equivalence between QCD(Sym/ASym) and $\mathcal{N}$ = 1 supersymmetric SU(N) Yang-Mills theory.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2020

Anatomy of $tthh$ physics at the HL-LHC

The t t h h production at colliders contains rich information on the nature of the Higgs boson. In this article, we systematically studied its physics at the high-luminosity Large Hadron Collider (HL-LHC), using exclusive channels with multiple ( ≥ 5 ) b -jets and one lepton ( 5 b 1 ℓ ), multiple ( ≥ 5 ) b -jets and opposite-sign dilepton ( 5 b 2 ℓ ), same-sign dilepton ( SS 2 ℓ ), multiple leptons (multi- ℓ ), and ditau resonance ( τ τ ). The scenarios analyzed include: (1) the t t h h production in Standard Model; (2) the t t h h production mediated by anomalous cubic Higgs self-coupling and t t h h contact interaction; (3) heavy Higgs ( H ) production with t t H → t t h h ; and (4) pair production of fermionic top partners ( T ) with T T → t t h h . To address the complication of event topologies and the mess of combinatorial backgrounds, a tool of boosted-decision-tree was applied in the analyses. The 5 b 1 ℓ and SS 2 ℓ analyses define the two most promising channels. For the nonresonant t t h h production, a combination of these exclusive analyses allows for its measurement in the SM with a statistical significance ~ 0.9 σ (with S / B > 1 % ), and may partially break the sensitivity degeneracy with respect to a varying cubic Higgs self-coupling, a difficulty usually thought to exist in gluon fusion di-Higgs analysis at HL-LHC. These sensitivities were also projected to future hadron colliders at 27 TeV and 100 TeV. For the resonant t t h h productions, the heavy Higgs boson in type II two-Higgs-doublet-model could be efficiently searched for between the mass thresholds 2 m h < m H < 2 m t and even beyond that, for relatively small tan β (vacuum alignment), while the fermionic top partners in composite Higgs models could be probed up to ~ 1.5 TeV and ~ 1.7 TeV , for Br ( T → t h ) = 25 % and 50%, respectively.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS1985

Superconducting magnet

Extensive computer based engineering design effort resulted in optimization of a superconducting magnet design with an average bulk current density of approximately 12KA/cm(2). Twisted, stranded 0.0045 inch diameter NbTi superconductor in a copper matrix was selected. Winding the coil from this bundle facilitated uniform winding of the small diameter wire. Test coils were wound using a first lot of the wire. The actual packing density was measured from these. Interwinding voltage break down tests on the test coils indicated the need for adjustment of the wire insulation on the lot of wire subsequently ordered for construction of the delivered superconducting magnet. Using the actual packing densities from the test coils, a final magnet design, with the required enhancement and field profile, was generated. All mechanical and thermal design parameters were then also fixed. The superconducting magnet was then fabricated and tested. The first test was made with the magnet immersed in liquid helium at 4.2K. The second test was conducted at 2K in vacuum. In the latter test, the magnet was conduction cooled from the mounting flange end.

Source record↗

NASA NTRS1992

Development of advanced seal verification

The purpose of this research is to develop a technique to monitor and insure seal integrity with a sensor that has no active elements to burn-out during a long duration activity, such as a leakage test or especially during a mission in space. The original concept proposed is that by implementing fiber optic sensors, changes in the integrity of a seal can be monitored in real time and at no time should the optical fiber sensor fail. The electrical components which provide optical excitation and detection through the fiber are not part of the seal; hence, if these electrical components fail, they can be easily changed without breaking the seal. The optical connections required for the concept to work does present a functional problem to work out. The utility of the optical fiber sensor for seal monitoring should be general enough that the degradation of a seal can be determined before catastrophic failure occurs and appropriate action taken. Two parallel efforts were performed in determining the feasibility of using optical fiber sensors for seal verification. In one study, research on interferometric measurements of the mechanical response of the optical fiber sensors to seal integrity was studied. In a second study, the implementation of the optical fiber to a typical vacuum chamber was implemented and feasibility studies on microbend experiments in the vacuum chamber were performed. Also, an attempt was made to quantify the amount of pressure actually being applied to the optical fiber using finite element analysis software by Algor.

Workman, Gary L.↗

DOE OSTI2021

Gas-phase pyrolysis of trans 3-pentenenitrile: competition between direct and isomerization-mediated dissociation

The flash pyrolysis of trans 3-pentenenitrile (3-PN, CH 3 –$CH=CH$–CH 2 –CN) was studied by combining the results of VUV photoionization mass spectra with broadband microwave spectra recorded as a function of the temperature of the pyrolysis tube. The two separated functional groups (vinyl and nitrile) open up isomerization as an initial step in competition with unimolecular dissociation. Primary products were detected by keeping the 3-PN concentration low and limiting reaction times to the traversal time of the gas in the pyrolysis tube (~100 μs). The reaction is quenched and products are cooled by expansion into vacuum before interrogation over the 8–18 GHz region using chirped-pulse broadband methods. 118 nm VUV photoionization of the same reaction mixture provides a means of detecting all products with ionization potentials below 10.5 eV with minimal fragmentation. These results are combined with a detailed computational investigation of the C 5 H 7 N and related potential energy surfaces, leading to a consistent picture of the unimolecular decomposition of 3-PN. Loss of two H-atoms to form a 79 amu product is proven from its microwave transitions to contain trans-Z-2,4-pentadienenitrile, while no pyridine is observed. Methyl loss, HCN loss, and breaking the central C(2)–C(3) bond all occur following isomerization of the position of the double bond, thereby opening up low-energy pathways to these decomposition channels.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Enhanced Tensile and Tear Toughness Properties of Thin-Wall Vacuum-Assisted High-Pressure Die-Cast Aural-5 Alloy by Friction Stir Processing

Steadily rising demand for glider weight reduction has driven the development of vacuum-assisted high-pressure die-cast (HPDC) Al-alloys for automotive structural components. Aural-5 is a strontium-modified HPDC alloy utilizing manganese (Mn) to reduce die soldering, eliminating detrimental needle-shaped Fe-bearing ß-phase intermetallic and improving ductility. HPDC Aural-5 contains shrinkage porosity, dendrites with Al-Si eutectic colonies, externally solidified crystals (ESCs), shear-band structure, and large second-phase particulates. Porosity, ESCs and large second-phase particles work as crack initiation sites, negatively impacting tensile properties. In this study, friction stir processing (FSP) is employed for microstructural modification of a thin-walled HPDC Aural-5 by eliminating porosity and breaking down dendrites, second-phase particles, eutectic colonies, ESCs and shear-band structures to create wrought microstructure with homogenized particle distribution. Mechanical property characterization indicates ~30% and ~35% enhancement in yield strength and ductility and associated marked effects on ~69% improvement in tear toughness according to the ASTM B871 test.

Friction stir processing, Aural-5, Strength, Tear ↗

DOE OSTI2023

Electromagnetic response of disordered superconducting cavities

We present the results for the resonant frequency shift and quality factor of disordered niobium (Nb) superconducting radio-frequency cavities driven out of equilibrium by the resonant microwave field. The theory is based on the non-equilibrium theory of superconductivity for the current response to the electromagnetic field at the vacuum–metal interface. We are able to accurately predict the observed frequency shifts with a precision of order fractions of kHz over the full temperature range 0 < T ≤ T c , including the negative frequency shift anomalies that are observed very near T c . The origin of these anomalies is shown to be the competition between the normal metal skin depth and the London penetration depth, which diverges as T→T c ⁻. An analytical approximation to the full current response, valid for |T-Tc| $\ll$ Tc, accounts for the negative frequency shift near T c . The non-monotonic dependence of the quality factor on the quasiparticle scattering rate is related to the pair-breaking effect of disorder on the superfluid fraction and, thus, the London penetration depth.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS2000

Simulated Space Environmental Testing on Thin Films

An exploratory program has been conducted, to irradiate some mature commercial and some experimental polymer films with radiation simulating certain Earth orbits, and to obtain data about the response of each test film's reflective and tensile properties. Protocols to conduct optimized tests were considered and developed to a "prototype" level during this program. Fifteen polymer film specimens were arranged on a specially designed test fixture. The fixture featured controlled exposure areas, and protected the ends of the samples for later gripping in tensile tests. The fixture featured controlled exposure areas, and protected the ends of the samples for later gripping in tensile tests. The fixture containing the films was installed in a clean vacuum chamber where protons, electrons and solar ultraviolet (UV) radiation could simultaneously irradiate the specimens. Near realtime UV rates were used, whereas proton and electron rates were accelerated appreciably to simulate 5 years in orbit during a two month test. Periodically, the spectral reflectance of each film was measured in situ. After the end of the irradiation, final reflectance measurements were made in situ, and solar absorptance values were derived for each specimen. These samples were then measured in air for thermal emittance and for tensile strength. Most specimens withstood the irradiation intact, but with reduced reflectance (increased solar absorptance). Thermal emittance changed slightly in several materials, as did their tensile strength and elongation at break. Conclusions are drawn about the performance of the films. Simulated testing to an expected 5 year dose of electrons and protons consistent with those expected at L2 and 0.98 AU orbits and 100 equivalent solar hours exposure.

Russell, Dennis A.↗

DOE OSTI2020

Tensor supercurrent in QCD

An external Abelian magnetic field excites in the QCD vacuum a tensor super current that represents the tensor polarization of the chiral condensate. This tensor supercurrent can be deduced from the chiral lagrangian in the presence of anoma lies; a similar tensor supercurrent emerges in rotating systems at finite chemical potential. We discuss the microscopic origin of this supercurrent and argue that it screens the instanton-anti-instanton $I\overline I$ molecules in the QCD vacuum, similarly to the vector supercurrent screening Abrikosov vortices in a superconductor. A number of possible experimental manifestations of the tensor supercurrent are discussed: i) spin alignment of axial-vector and vector mesons in heavy ion collisions; ii) tensor charge of the nucleon; iii) transversity of quark distributions in polarized nucleons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2020

On the breaking of Casimir scaling in jet quenching

Abstract We study the breaking of Casimir scaling, $$C_F/C_A$$ C F / C A , due to the evolution of jets in a hot and extended medium. By using JEWEL, a medium modified Monte Carlo event generator validated for a wide set of observables, we are able to study separately the development of quark and gluon-initiated jets produced back-to-back with a $$Z-$$ Z - boson. Focusing on the $$p_T$$ p T distribution, we conclude first that the colour charge ratio is constant but larger than Casimir scaling for high $$p_T$$ p T jets. In addition, our results seem to indicate that the medium induced cascade is more similar between quarks and gluons, thus driving the overall medium shower scaling away from the vacuum expectation. Finally, we compare our results to another Monte Carlo generator and observe the same scaling violation.

Apolinário, Liliana↗

DOE OSTI2023

New Theories for Neutrino Masses and Dark Matter

The main goal of the project is to investigate new theories for neutrino masses and dark matter, and understand their testability in different experiments. The PI proposed several mechanisms for neutrino masses in the context of B-L theories, left-right symmetric theories, supersymmetric theories and grand unified theories. The PI would like to investigate new ways to understand the origin of neutrino masses where the seesaw scale is in the multi-TeV region. One can have a multi-TeV seesaw scale in scenarios where the same symmetry relevant for neutrino masses defines the dark matter relic density, or in the minimal supersymmetric theory based on local B-L. In these theories one can have new ways to understand the testability of the origin of neutrino masses at colliders and low energy experiments. In these theories one predicts the possibility to observe lepton number violating signatures at the LHC, one can predict large contributions to lepton number violating processes such as mu to e conversion, neutrinoless double beta decay experiments and others. The nature of the dark matter in the Universe is one of the most important problems in cosmology. Two of the most popular candidates are the Axions and the Weakly Interacting Massive Particles (WIMPs). The PI would like to investigate the implications of a new electroweak theta term similar to the QCD vacuum angle but in the SU(2) gauge sector of the SM which is physical if the baryon and lepton numbers are broken symmetries. We will investigate the implications of having a new electroweak theta term dark matter portal, the implications for baryogenesis and understand the constraints coming from different experiments such as the searches for electric dipole moments and axion experiments. The implications of having the electroweak theta term in theories with different sources of baryon and lepton number violation will be investigated. WIMPs are perhaps the most appealing candidates for many reasons. The PI would like to investigate the properties of WIMPs in different gauge theories, study the implications of the cosmological bounds on the WIMPs relic density for the symmetry breaking scale in models for new physics. The PI would like to investigate in great detail the predictions for gamma lines, neutrino lines and other striking signatures which can be present in these theories. These studies can have a profound impact in the testability of different theories for physics beyond the Standard Model.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2022

Muon $$\mathbf {g-2}$$, neutralino dark matter and stau NLSP

Abstract We explore the implications of resolving the muon $$g-2$$ g - 2 anomaly in a $$SU(4)_c \times SU(2)_L \times SU(2)_R$$ S U ( 4 ) c × S U ( 2 ) L × S U ( 2 ) R model, where the soft supersymmetry breaking scalar and gaugino masses break the left-right (LR) symmetry. A 2 $$\sigma $$ σ resolution of the anomaly requires relatively light sleptons, chargino and LSP neutralino. The stau turns out to be the NLSP of mass $$m_{\tilde{\tau }}\lesssim 400$$ m τ ~ ≲ 400 GeV, and the sleptons from the first two families can be as heavy as about 800 GeV. The chargino is also required to be lighter than about 600 GeV to accommodate the muon $$g-2$$ g - 2 solutions consistent with the dark matter relic density constraint. The dominant right-handed nature of the light slepton states suppress the sensitivity of possible signals which can be probed in Run3 experiments at the LHC. We also discuss the impact of accommodating the Higgs boson mass and the vacuum stability of the scalar potential for these solutions. Although a light stau can be compatible with the stability of the scalar potential, the Higgs boson mass constraint has a strong impact on the solutions with $$\tan \beta $$ tan β bounded from above, namely $$\tan \beta \lesssim 20$$ tan β ≲ 20 . The Higgsinos are heavier than about 4 TeV, and the LSP neutralino has the correct relic density if it is Bino-like. We identify stau–neutralino coannihilation as the dominant mechanism for realizing the desired dark matter relic density, with sneutrino–neutralino coannihiliation playing a minor role. These bino-like dark matter solutions can yield a spin-independent scattering cross-section on the order of $$10^{-13}$$ 10 - 13 pb which hopefully, can be expected to be tested in the near future.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

NASA NTRSDate not supplied

NavCube3-mini Lunar GNSS Receiver

This paper describes development and testing of NASA Goddard Space Flight Center’s new NavCube3-mini (NC3m) spaceborne, weak-signal GNSS receiver, which targets all Earth orbit regimes with special focus on lunar applications. NC3m derives from the ground-breaking Magnetospheric Multiscale (MMS) mission Navigator GPS receiver. The MMS-Navigator (launched 2015) holds a Guinness World Record for highest altitude GPS fix and is currently in a highly elliptic orbit with a 29 Earth radii apogee, nearly half lunar distance. NC3m has reduced size, weight, and power compared to the MMS-Navigator, making it suitable for smallsat applications, and adds multi-frequency and multi-GNSS capabilities, among other improvements. A NC3m engineering test unit was subjected to and successfully completed a comprehensive Technology Readiness Level 6 (system/subsystem model or prototype demonstration in a relevant environment) testing campaign in the second half of 2022. This involved high-fidelity simulations in LEO, GEO, and lunar regimes and full environmental testing, including vibration, thermal vacuum, and electromagnetic compatibility. An overview of the NC3m receiver, the test setup, and a sample of results is presented. The results include predicted performance at high-altitude and in the lunar regime.

NavCube3↗

DOE OSTI2021

Overview of the fusion nuclear science facility, a credible break-in step on the path to fusion energy

The Fusion Nuclear Science Facility (FNSF) is examined here as part of a two step program from ITER to commercial power plants. This first step is considered mandatory to establish the materials and component database in the real fusion in-service environment before proceeding to larger electricity producing facilities. The FNSF can be shown to make tremendous advances beyond ITER, toward a power plant, particularly in plasma duration and fusion nuclear environment. A moderate FNSF is studied in detail, which does not generate net electricity, but does reach the power plant blanket operating temperatures. The full poloidal Dual Coolant Lead Lithium (DCLL) blanket is chosen, with alternates being the Helium Cooled Lead Lithium (HCLL) and Helium Cooled Ceramic Breeder/Pebble Bed (HCCB/PB). Several power plant relevant choices are made in order to follow the philosophy of targeted technologies. Any fusion core component must be qualified by fusion relevant neutron testing and highly integrated non-nuclear testing before it can be installed on the FNSF in order to avoid the high probability of constant failures in a plasma-vacuum system. A range of missions for the FNSF, or any fusion nuclear facility on the path toward fusion power plants, are established and characterized by several metrics. A conservative physics strategy is pursued to accommodate the transition to ultra-long plasma pulses, and parameters are chosen to represent the power plant regime to the extent possible. An operating space is identified, and from this, one point is chosen for further detailed analysis, with R = 4.8 m, a = 1.2 m, IP = 7.9 MA, BT = 7.5 T, βN Gr = 0.9, fBS = 0.52, q95 = 6.0, H98 ∼1.0, and Q = 4.0. The operating space is shown to be robust to parameter variations. A program is established for the FNSF to show how the missions for the facility are met, with a He/H, a DD and 5 DT phases. The facility requires ∼25 years to complete its DT operation, including 7.8 years of neutron production, and the remaining spent on inspections and maintenance. The DD phase is critical to establish the ultra-long plasma pulse lengths. The blanket testing strategy is examined, and shows that many sectors have penetrations for heating and current drive (H/CD), diagnostics, or Test Blanket Modules (TBMs). The hot cell is a critical facility element in order for the FNSF to perform its function of developing the in-service material and component database. The pre-FNSF R&D is laid out in terms of priority topics, with the FNSF phases driving the time-lines for R&D completion. A series of detailed technical assessments of the FNSF operating point are reported in this issue, showing the credibility of such a step, and more detailed emphasis on R&D items to pursue. These include nuclear analysis, thermo-mechanics and thermal-hydraulics, liquid metal thermal hydraulics, transient thermo-mechanics, tritium analysis, maintenance assessment, magnet specification and analysis, materials assessments, core and scrape-off layer (SOL)/divertor plasma examinations.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS2008

Lunar Dust and Lunar Simulant Activation and Monitoring

Prior to returning to the moon, understanding the effects of lunar dust on both human physiology and mechanical equipment is a pressing concern, as problems related to lunar dust during the Apollo missions have been well documented (J.R. Gaier, The Effects of Lunar Dust on EVA Systems During the Apollo Missions. 2005, NASA-Glenn Research Center. p. 65). While efforts were made to remove the dust before reentering the lunar module, via brushing of the suits or vacuuming, a significant amount of dust was returned to the spacecraft, causing various problems. For instance, astronaut Harrison Schmitt complained of hay fever effects caused by the dust, and the abrasive nature of the material was found to cause problems with various joints and seals of the spacecraft and suits. It is clear that, in order to avoid potential health and performance problems while on the lunar surface, the reactive properties of lunar dust must be quenched. It is likely that soil on the lunar surface is in an activated form, i.e. capable of producing oxygen-based radicals in a humidified air environment, due to constant exposure to meteorite impacts, UV radiation, and elements of the solar wind. An activated silica surface serves as a good example. An oxygen-based radical species arises from the breaking of Si-OSi bonds. This system is comparable to that expected for the lunar dust system due to the large amounts of agglutinic glass and silicate vapor deposits present in lunar soil. Unfortunately, exposure to the Earth s atmosphere has passivated the active species on lunar dust, leading to efforts to reactivate the dust in order to understand the true effects that will be experienced by astronauts and equipment on the moon. Electron spin resonance (ESR) spectroscopy is commonly used for the study of radical species, and has been used previously to study silicon- and oxygen-based radicals, as well as the hydroxyl radicals produced by these species in solution (V. Vallyathan, et al., Am. Rev. Respir. Dis. 138 (1988) 1213-1219). The size and cost of these instruments makes them unattractive for the monitoring of lunar dust activity. A more suitable technique is based on the change in fluorescence of a molecule upon reaction with a hydroxyl radical (or other radical species). Fluorescence instruments are much less costly and bulky than ESR spectrometers, and small fluorescence sensors for space missions have already been developed (F. Gao, et al., J. Biomed. Opt. 10 (2005) 054005). For the current fluorescence studies, the terephthalate molecule has been chosen for monitoring the production of hydroxyl radicals in solution. As shown in Scheme 1, the reaction between the non-fluorescent terephthalate molecule and a hydroxyl radical produces the highly-fluorescent 2-hydroxyterephthalate molecule.

Wallace, W. T.↗

DOE OSTI2024

Extracting the femtometer structure of strange baryons using the vacuum polarization effect

Abstract One of the fundamental goals of particle physics is to gain a microscopic understanding of the strong interaction. Electromagnetic form factors quantify the structure of hadrons in terms of charge and magnetization distributions. While the nucleon structure has been investigated extensively, data on hyperons are still scarce. It has recently been demonstrated that electron-positron annihilations into hyperon-antihyperon pairs provide a powerful tool to investigate their inner structure. We present a method useful for hyperon-antihyperon pairs of different types which exploits the cross section enhancement due to the effect of vacuum polarization at theJ/ψresonance. Using the 10 billionJ/ψevents collected with the BESIII detector, this allows a precise determination of the hyperon structure function. The result is essentially a precise snapshot of the$$\bar{\Lambda }{\Sigma }^{0}\,(\Lambda {\bar{\Sigma }}^{0})$$ Λ ¯ Σ 0 ( Λ Σ ¯ 0 ) transition process, encoded in the transition form factor ratio and phase. Their values are measured to beR = 0.860 ± 0.029(stat.) ± 0.015(syst.),$$\Delta {\Phi }_{\bar{\Lambda }{\Sigma }^{0}}=(1.011\pm 0.094({{\rm{stat.}}})\pm 0.010({{\rm{syst.}}}))\,{{\rm{r}}}ad$$ Δ Φ Λ ¯ Σ 0 = ( 1.011 ± 0.094 ( stat. ) ± 0.010 ( syst. ) ) r a d and$$\Delta {\Phi }_{\Lambda {\bar{\Sigma }}^{0}}=(2.128\pm 0.094({{\rm{stat.}}})\pm 0.010({{\rm{syst.}}}))\,{{\rm{r}}}ad$$ Δ Φ Λ Σ ¯ 0 = ( 2.128 ± 0.094 ( stat. ) ± 0.010 ( syst. ) ) r a d . Furthermore, charge-parity (CP) breaking is investigated in this reaction and found to be consistent with CP symmetry.

Science & Technology - Other Topics↗