Measured Decay Rates Research Articles

Selection of the averaging time for the interrupted noise method of measuring reverberation time

The author wrote the requirements for the selection of the averaging time for the interrupted noise method of measuring reverberation time in the international standard ISO 354:1985 "Acoustics-Measurement of sound absorption in a reverberation room". When this standard was revised to become ISO 354:2003, the evaluation range used to measure the reverberation time was changed from 30 dB to 20 dB. Because the working group which revised the standard did not know the reasons for the averaging time requirements, they incorrectly changed them to supposedly take account of the change to the evaluation range. The purpose of this paper is to give the reasons for the averaging time requirements so that they are corrected and not incorrectly changed again. It is necessary that the averaging time is not so large that information is discarded and so that, in the case of exponential averaging devices, the measured decay rate is not biased by the decay rate of the exponential averaging device. On the other hand, it is desirable that the averaging time be as large as possible so that the ensemble standard deviation of the measured reverberation times is as small as possible.

Effectiveness of do-it-yourself air cleaners in reducing exposure to respiratory aerosols in US classrooms: A longitudinal study of public schools

Poor indoor air quality (IAQ) harms student health and cognitive performance. Air filtration serves to reduce concentrations of particles in indoor environments. We have characterized the performance of Do-It-Yourself air filtration units in primary and secondary public schools in Arizona and Connecticut during the 2022-23 school year. We monitored indoor air quality in 53 classrooms across 5 schools in two states over a six-month period. Measurements of decay rates of aerosol particles smaller than 2.5 μm emitted into classrooms during periods with and without the air cleaners allowed for determination of the effective air changes per hour (ACHe) and apparent clean air delivery rate (CADR). We found an average Clean Air Delivery Rate (CADR) of 239 ft3min-1 (range of 101–355 ft3min-1) across a diverse sample of geographic locations and building types, including naturally and mechanically ventilated learning environments. We observed a 43.3 % reduction in PM2.5 concentrations and 30.6 % reduction in PM10 concentrations in mechanically ventilated classrooms. This study suggests that the addition of a DIY air filtration unit effectively improves indoor particle control in school classrooms across a diverse sample of geographic locations and building types.

Enhancement of dual zero phonon line emissions in nanodiamonds using quasiperiodic photonic structures.

Color centers in nanodiamonds (NDs) have been largely explored by coupling to a photonic structured matrix (PSM) to amplify visible range emission features, enhancing their use in quantum technologies. Here, we study the emission enhancement of dual near-infrared zero phonon line (ZPL) emission from silicon-boron (SiB) and silicon-vacancy (SiV-) centers in NDs using a spontaneously emerged low index-contrast quasiperiodic PSM, having micron-scale air pores. An intensity enhancement factor of 6.15 for SiV- and 7.8 for SiB ZPLs is attained for the PSM sample compared to a control sample. We find Purcell enhancement of 2.77 times for the PSM sample using spatial-dependent decay rate measurements, supported by localized field intensity confinement in the sample. Such cavity-like emission enhancement and lifetime reduction are enabled by an in-plane order-disorder scattering in the PSM sample substantiated by pump-dependent emission measurements. The results put forward a facile approach to tailor the near-infrared dual ZPL emission from NDs using nanophotonic structures.

Measurement of the decay of laser-driven linear plasma wakefields.

We present measurements of the temporal decay rate of one-dimensional (1D), linear Langmuir waves excited by an ultrashort laser pulse. Langmuir waves with relative amplitudes of approximately 6% were driven by 1.7J, 50fs laser pulses in hydrogen and deuterium plasmas of density n_{e0}=8.4×10^{17}cm^{-3}. The wakefield lifetimes were measured to be τ_{wf}^{H_{2}}=(9±2) ps and τ_{wf}^{D_{2}}=(16±8) ps, respectively, for hydrogen and deuterium. The experimental results were found to be in good agreement with 2D particle-in-cell simulations. In addition to being of fundamental interest, these results are particularly relevant to the development of laser wakefield accelerators and wakefield acceleration schemes using multiple pulses, such as multipulse laser wakefield accelerators.

Ambient humidity, the overlooked influencer of radioactivity measurements

When verifying the validity of the exponential-decay law through 137 precise decay rate measurement series at various nuclear laboratories, minor violations have been observed in the shape of annual cycles in the residuals with different amplitudes and phase shifts. The timing and amplitude of these deviations have been compared with local weather data and it appears that ambient humidity is highly correlated with the observed instabilities in these radioactivity measurements. In fact, when compensating the residuals for a linear relationship with absolute humidity in air, most of the annual cycles are no longer statistically significant. As a result, the validity of the exponential-decay law can now be demonstrated with even higher fidelity.

Frequency Tunable, Cavity-Enhanced Single Erbium Quantum Emitter in the Telecom Band.

Single quantum emitters embedded in solid-state hosts are an ideal platform for realizing quantum information processors and quantum network nodes. Among the currently investigated candidates, Er^{3+} ions are particularly appealing due to their 1.5 μm optical transition in the telecom band as well as their long spin coherence times. However, the long lifetimes of the excited state-generally in excess of 1ms-along with the inhomogeneous broadening of the optical transition result in significant challenges. Photon emission rates are prohibitively small, and different emitters generally create photons with distinct spectra, thereby preventing multiphoton interference-a requirement for building large-scale, multinode quantum networks. Here we solve this challenge by demonstrating for the first time linear Stark tuning of the emission frequency of a single Er^{3+} ion. Our ions are embedded in a lithium niobate crystal and couple evanescently to a silicon nanophotonic crystal cavity that provides a strong increase of the measured decay rate. By applying an electric field along the crystal c axis, we achieve a Stark tuning greater than the ion's linewidth without changing the single-photon emission statistics of the ion. These results are a key step towards rare earth ion-based quantum networks.

Final Results of GERDA on the Two-Neutrino Double-β Decay Half-Life of ^{76}Ge.

We present the measurement of the two-neutrino double-β decay rate of ^{76}Ge performed with the GERDA Phase II experiment. With a subset of the entire GERDA exposure, 11.8kg yr, the half-life of the process has been determined: T_{1/2}^{2ν}=(2.022±0.018_{stat}±0.038_{syst})×10^{21} yr. This is the most precise determination of the ^{76}Ge two-neutrino double-β decay half-life and one of the most precise measurements of a double-β decay process. The relevant nuclear matrix element can be extracted: M_{eff}^{2ν}=(0.101±0.001).

Validation of a railway rolling noise model on a system with slab track and resilient wheels

This study investigates rolling noise emissions using an analytical model of the Seattle Sound Transit Light Rail system developed using Train Noise Expert (TNE) software. Measurements of track frequency response, decay rate, rail and wheel roughness were used to determine model input parameters. Wheel modal test results were used to characterize the wheels. Wayside noise and track vibration measurements during revenue service train passbys were used to experimentally validate the model. The average difference between measured and predicted overall passby LAeq noise at a position immediately adjacent to the track was 0.1 dBA (average from four scenarios, i.e. two surface track sites with two train types). Inspection of the predicted versus measured noise spectra indicates the model does not exactly match the measured spectrum in every frequency band, however the correlation with overall spectrum shape is good in the frequency bands that contribute most to the overall A-weighted level. It is concluded that the model provides an accurate representation of the most relevant physical rolling noise factors and is reliable with resilient wheels and light rail vehicles on ballast and slab track.

Two-dimensional reconstruction of filament temperatures and densities with the thermal helium beam at ASDEX Upgrade

In the scrape-off layer (SOL) of fusion plasmas, radial particle and energy transport is mainly carried by plasma filaments. The plasma parameters of such filaments can be measured by the thermal helium beam diagnostic (THB). By means of an extended collisional radiative model (CRM) used for the evaluation of the diagnostic data, the light intensity response of neutral helium transitions from filaments is studied, which depends on the parameters of the filament and the background. The electron density of the filament is found to be the dominant parameter impacting the line intensities. By applying a numerical reconstruction algorithm based on the CRM, electron temperatures and densities as well as the sizes of experimentally measured filaments are obtained. This method allows for the first time measurements of the temporal decay rates of filament density and temperature in the co-moving frame of the filament and its radial propagation velocity.

Inclusion of hydrodynamic properties of bathing waters is critical in selecting faecal indicators to assess public health impacts of faecal contamination

The EU Bathing Water Directive (BWD) requires member states to assess bathing water quality according to the levels of faecal indicator bacteria (FIB) in designated bathing areas. However, this criterion has two significant limitations given that the BWD does not; (i) account for differences in hydrodynamic properties of bathing waters and, (ii) assumes that all faecal pathogens decay equally in aquatic environments. This study simulated sewage discharge events in three hypothetical aquatic environments characterised by different advection and dispersion parameters in the solute transport equation. Temporal changes in the downstream concentration of six faecal indicators were determined in simulations that utilised measured decay rates of each faecal indicator from a programme of controlled microcosm experiments in fresh and seawater environments. The results showed that the decay rates of faecal indicators are not a critical parameter in advection dominant water bodies, such as in fast-flowing rivers. Therefore, faecal indicator selection is less important in such systems and for these, FIB remains the most cost-effective faecal indicator to monitor the public health impacts of faecal contamination. In contrast, consideration of faecal indicator decay is important when assessing dispersion and advection/dispersion dominant systems, which would pertain to transitional (estuarine) and coastal waterbodies. Results suggest that the inclusion of viral indicators, such as crAssphage and PMMoV, could improve the reliability of water quality modelling and minimise the risk of waterborne illnesses from faecal contamination.

Comparison of Viral Production and Decay Rates at the Surface and Bottom of the Euphotic Zone in the Summertime in the Southern East China Sea

Viral dynamics are the result of the balance between the rates of viral production and decay. Here, we have carried out independent measurements of viral production and decay rates in different depths of the southern East China Sea in summer (August and October 2021). In this study, the prevalence of viral abundance at the surface waters (14.2~27.6 × 105 viruses mL−1) was significantly higher than the bottom of the euphotic zone (2.9~12.6 × 105 viruses mL−1). As for viruses to bacteria ratio (VBR) values, we found a wide variability both at the surface (1.4 to 3.2) and bottom of the euphotic zone (2.1 to 16.2). The results of our study showed that at all stations examined, in the southern East China Sea, the values of gross viral production (GVP) were significantly higher in the sunlit surfaces compared to the bottom of the euphotic zone. In particular, our analysis indicates that no significant viral decay rates (VD) were observed in some regions at the bottom of the euphotic zone. Here, we also provide a budget for viral abundance and net viral production in different regions in the southern East China Sea. The GVP or VD is not applicable in our case to explain VBR is high at bottom of the euphotic zone. The mechanisms underlying VBR uncoupling, viral production, and viral loss in marine systems are still being investigated.

Track Decay Rate (TDR) Measurement Method for Reactive Damping by Tuned Mass Damper (TMD)

TDR measures the rate of vibration decay along rail in dB/m. Higher TDR leads to lower noise radiation. However, new railways are often having low TDR due to the use of resilient fasteners (to provide vibration isolation between rail and supporting structure for ground borne noise concerns), which leads to high noise radiation. Rail damper is used to increase TDR (thus reduces railway noise), where TMD is an efficient damping mechanism dissipating the vibration energy of the rail. TMD provides reactive damping force, maximised after a few cycles of oscillations. TMD force is stronger with continuous excitation than impulse excitation. For convenient purposes in the industry, TDR measurements are primarily conducted by impulse method, which do not allow sufficient time to include reactive TMD force. Therefore, impulse excitation TDR is smaller than continuous excitation TDR. Continuous excitation TDR is considered to reflect more of the real case of wheel/rail interaction excitation during train running. Besides, TDR in terms of time decay in dB/s is an alternative approach for evaluating noise performance of the rail. This paper presents TDR measurement results under different conditions, e.g., impulse excitation against continuous excitation; freely supported short rail (~6m), short rail (~6m) with resilient fastener support as well as site measurements in continuous welded rails.

Fill and dump measurement of the neutron lifetime using an asymmetric magneto-gravitational trap

The past two decades have yielded several new measurements and reanalysis of older measurements of the neutron lifetime. These have led to a 4.4 standard deviation discrepancy between the most precise measurements of the neutron decay rate producing protons in cold neutron beams and the most precise lifetime measured in neutron storage experiments. Measurements using different techniques are important for investigating whether there are unidentified systematic effects in any of the measurements. In this paper we report a new measurement using the Los Alamos asymmetric magneto-gravitational trap where the surviving neutrons are counted external to the trap using the fill and dump method. The new measurement gives a free neutron lifetime of τn=876.3(2.4)stat(0.8)syst. Although this measurement is not as precise, it is in statistical agreement with previous results using in situ counting in the same apparatus.Received 6 May 2022Accepted 17 November 2022DOI:https://doi.org/10.1103/PhysRevC.106.065506©2022 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasBeta decayLifetimes & widthsParticle decaysPhysical SystemsNeutronsNuclear PhysicsParticles & Fields

The First Direct Measurement of Gravitational Potential Decay Rate at Cosmological Scales and Improved Dark Energy Constraint

The integrated Sachs–Wolfe (ISW) effect probes the decay rate (DR) of large-scale gravitational potential and therefore provides a unique constraint on dark energy (DE). However, its constraining power is degraded by the ISW measurement, which relies on cross-correlating with the large-scale structure (LSS) and suffers from uncertainties in galaxy bias and matter clustering. In combination with lensing-LSS cross correlation, DR can be isolated in a way free of uncertainties in galaxy bias and matter clustering. We applied this proposal to the combination of the Data Release 8 galaxy catalog of DESI imaging surveys and Planck cosmic microwave background maps. We achieved the first DR measurement, with a total significance of 3.2σ. We verified the measurements at three redshift bins ([0.2, 0.4), [0.4, 0.6), [0.6, 0.8]), with two LSS tracers (the “low-density points” and the conventional galaxy positions). Despite its relatively low signal-to-noise ratio, the addition of DR significantly improves dark energy constraints, over Sloan Digital Sky Survey baryon acoustic oscillation (BAO) data alone or Pantheon supernovae (SNe) compilation alone. For flat wCDM cosmology, the improvement in the precision of Ω m is a factor of 1.8 over BAO and 1.5 over SNe. For the DE equation of state w, the improvement factor is 1.3 over BAO and 1.4 over SNe. These improvements demonstrate DR as a useful cosmological probe, and therefore we advocate its usage in future cosmological analysis.

On the Numerical Determination of the Density and Energy Spatial Distributions relevant for in-Plasma β-Decay Emission Estimation

Aim of the PANDORA (Plasmas for Astrophysics, Nuclear Decays Observation and Radiation for Archeometry) project is the in-plasma measurements of decay rates of beta radionuclides as a function of the ionization stage. In this view, a precise calculation of plasma electrons density and energy is mandatory, being responsible for ions’ creations and their spatial distribution following plasma neutrality. This paper describes the results of the INFN simulation tools applied for the first time to the PANDORA plasma, including electromagnetic calculations and electrons’ dynamics within the so-called self-consistent loop. The distribution of the various electrons’ population will be shown, with special attention to the warm component on which depends the obtained ions’ charge state distribution. The strict relation of the results with the evaluation of the in-plasma nuclear decays will be also explained.

Air humidity and annual oscillations in 90Sr/90Y and 60Co decay rate measurements

Parkhomov published decay rate measurements of 90Sr/90Y and 60Co beta decay sources with Geiger–Müller counters which showed annual cyclic deviations with less than 0.2% amplitude from a purely exponential slope. He investigated instrument instability induced by environmental parameters, yet did not find a clear coincidence with local temperature, atmospheric pressure, and relative humidity. Parkhomov hypothesised that gravitationally-focussed ‘slow’ cosmic neutrinos influenced beta decay. In the current work, environmental conditions in the Moscow area at the time of the experiment are presented. There appears to be a resemblance of the shape of the annual 90Sr/90Y decay rate anomalies with the inverse of the absolute air humidity, albeit with an apparent time shift of 0.05–0.15 year. Humidity may have influenced the range of beta particles in air, as well as geometric and electronic properties of the detection set-up, however causality could not be unambiguously demonstrated. The instabilities in the 60Co data were more difficult to correlate with environmental data, except for some similarities with temperature and external dew point.

Microstructural coarsening in dense binary systems

The kinetics of microstructural evolution driven by phase coarsening (Ostwald ripening) in a binary, two-phase system were studied systematically at ultra high volume fractions of the dispersed phase. Three-dimensional phase-field simulations and theoretical analysis are compared. Late-stage microstructure evolution at ultra high volume fractions (VV>0.9) are reported here. One interesting finding is that the scaling exponents, m, for the kinetics of phase coarsening at ultra high volume fractions take values in the range 2<m<3, depending on the precise volume fraction of the dispersed phase, when varied over the narrow range 0.9<VV<1. This result is confirmed by a comparative study of simulated microstructures and measurements of interfacial energy decay rates with theoretical coarsening analysis. Scaled particle-size distributions derived from simulations at ultra high volume fractions agree neither with Wagner’s 3D particle-size distribution for interface-reaction controlled phase coarsening, nor with Lifshitz and Slyozov’s particle-size distribution for diffusion-controlled phase coarsening. The research reported substantiates that the kinetics of microstructure evolution at ultra high volume fractions, approaching true grain growth, exhibits a varying blend of both interface reaction-controlled and volume diffusion-controlled phase coarsening.

Fermi polarons at finite temperature: Spectral function and rf spectroscopy

We present a systematic study of a mobile impurity immersed in a three-dimensional Fermi sea of fermions at finite temperature, by using the standard non-self-consistent many-body $T$-matrix theory that is equivalent to a finite-temperature variational approach with the inclusion of one-particle-hole excitation. The impurity spectral function is determined in the real-frequency domain, avoiding any potential errors due to the numerical analytic continuation in previous $T$-matrix calculations and the small spectral broadening parameter used in variational calculations. In the weak-coupling limit, we find that the quasiparticle decay rate of both attractive and repulsive polarons does not increase significantly with increasing temperature, and therefore Fermi polarons may remain well-defined far above Fermi degeneracy. In contrast, near the unitary limit with strong coupling, the decay rate of Fermi polarons rapidly increase and the quasiparticle picture breaks down close to the Fermi temperature. We analyze in detail the recent ejection and injection radio-frequency (rf) spectroscopy measurements, performed at Massachusetts Institute of Technology (MIT) and at European Laboratory for Non-Linear Spectroscopy (LENS), respectively. We show that the momentum average of the spectral function, which is necessary to account for the observed rf-spectroscopy, has a sizable contribution to the width of the quasiparticle peak in spectroscopy. As a result, the measured decay rate of Fermi polarons could be significantly larger than the calculated quasiparticle decay rate at zero momentum. By take this crucial contribution into account, we find that there is a reasonable agreement between theory and experiment for the lifetime of Fermi polarons in the strong-coupling regime, as long as they remain well-defined.

M_{b} at m_{H}: The Running Bottom Quark Mass and the Higgs Boson.

We present a new measurement of the bottom quark mass in the MS[over ¯] scheme at the renormalization scale of the Higgs boson mass from measurements of Higgs boson decay rates at the LHC: m_{b}(m_{H})=2.60_{-0.31}^{+0.36} GeV. The measurement has a negligible theory uncertainty and excellent prospects to improve at the HL-LHC and a future Higgs factory. Confronting this result and m_{b}(m_{b}) from low-energy measurements and m_{b}(m_{Z}) from Z-pole data, with the prediction of the scale evolution of the renormalization group equations, we find strong evidence for the "running" of the bottom quark mass.

Generation of stripe-like vortex flow by noncollinear waves on the water surface

We have studied experimentally the generation of vortex flow by gravity waves with a frequency of 2.34Hz excited on the water surface at an angle 2θ=arctan(3/4)≈36∘ to each other. The resulting horizontal surface flow has a stripe-like spatial structure. The width of the stripes L=π/(2ksinθ) is determined by the wave vector k of the surface waves and the angle between them, and the length of the stripes is limited by the system size. It was found that the vertical vorticity Ω of the current on the fluid surface is proportional to the product of wave amplitudes, but its value is much higher than the value corresponding to the Stokes drift and it continues to grow with time even after the wave motion reaches a stationary regime. We demonstrate that the measured dependence Ω(t) can be described within the recently developed model that takes into account the Eulerian contribution to the generated vortex flow and the effect of surface contamination. This model contains a free parameter that describes the elastic properties of the contaminated surface, and we also show that the found value of this parameter is in reasonable agreement with the measured decay rate of surface waves.