Decay Events Research Articles

Development of a gating grid driver of TPC for exotic beam experiments

The Multi-purpose Time Projection Chamber (TPC) for nuclear AsTrophysical and Exotic beam experiments (MATE) is being upgraded for the decay and active target experiments at the Heavy Ion Research Facility in Lanzhou (HIRFL). We have developed a gating grid driver to control the transitions between the closed and open states of the gating grid of the MATE-TPC to detect interesting rare decay events from a large amount of implanted ions. The gating grid driver is mainly composed of a digital control unit and a high-voltage switch unit. The digital control unit responds to the external trigger and generates control signals for the operation of the high-voltage control part based on the presetting instruction. The high-voltage switch unit is connected to two negative high voltages with different values and changes the voltages of neighboring wires of the gating grid based on the request for closing or opening the gate. A 500 ns switching time of the gating grid driver has been achieved from the closed to open state. The duration of the open state can be adjusted from 1 µs to 99 ms based on the experimental requirements. This gating grid driver can be used in a particle detector with a high voltage bias of up to ± 3000 V.

Promoting High-Oxidation-State Metal Active Sites in a Hollow Ternary Metal Fluoride Nanoflake Array for Urea Electrolysis.

The adsorption ability of hydrogen, hydroxide, and oxygenic intermediates plays a crucial role in electrochemical water splitting. Electron-deficient metal-active sites can prompt electrocatalytic activity by improving the adsorption ability of intermediates. However, it remains a significant challenge to synthesize highly abundant and stable electron-deficient metal-active site electrocatalysts. Herein, we present a general approach to synthesizing a hollow ternary metal fluoride (FeCoNiF2) nanoflake array as an efficient and robust bifunctional electrocatalyst for the hydrogen evolution reaction (HER) and urea oxidation reaction (UOR). We find that the F anion withdraws electrons from the metal centers, inducing an electron-deficient metal center catalyst. The rationally designed hollow nanoflake array exhibits the overpotential of 30 mV for HER and 130 mV for UOR at a current density of 10 mA cm-2 and superior stability without decay events over 150 h at a large current density of up to 100 mA cm-2. Remarkably, the assembled urea electrolyzer using a bifunctional hollow FeCoNiF2 nanoflake array catalyst requires cell voltages of only 1.352 and 1.703 V to afford current densities of 10 and 100 mA cm-2, respectively, which are 116 mV less compared with that required for overall water splitting.

Analysis of Race and Ethnicity, Socioeconomic Factors, and Tooth Decay Among US Children

ImportanceWhile large oral health disparities remain by race and ethnicity among children, the associations of race, ethnicity, and mediating factors with oral health outcomes are poorly characterized. Identifying the pathways that explain these disparities would be critical to inform policies to effectively reduce them.ObjectiveTo measure racial and ethnic disparities in the risk of developing tooth decay and quantify relative contributions of factors mediating the observed disparities among US children.Design, Setting, and ParticipantsThis retrospective cohort study used electronic health records of US children from 2014 to 2020 to measure racial and ethnic disparities in the risk of tooth decay. Elastic net regularization was used to select variables to be included in the model among medical conditions, dental procedure types, and individual- and community-level socioeconomic factors. Data were analyzed from January 9 to April 28, 2023.ExposuresRace and ethnicity of children.Main Outcomes and MeasuresThe main outcome was diagnosis of tooth decay in either deciduous or permanent teeth, defined as at least 1 decayed, filled, or missing tooth due to caries. An Anderson-Gill model, a time-to-event model for recurrent tooth decay events with time-varying covariates, stratified by age groups (0-5, 6-10, and 11-18 years) was estimated. A nonlinear multiple additive regression tree–based mediation analysis quantified the relative contributions of factors underlying the observed racial and ethnic disparities.ResultsAmong 61 083 children and adolescents aged 0 to 18 years at baseline (mean [SD] age, 9.9 [4.6] years; 30 773 [50.4%] female), 2654 Black individuals (4.3%), 11 213 Hispanic individuals (18.4%), 42 815 White individuals (70.1%), and 4401 individuals who identified as another race (eg, American Indian, Asian, and Hawaiian and Pacific Islander) (7.2%) were identified. Larger racial and ethnic disparities were observed among children aged 0 to 5 years compared with other age groups (Hispanic children: adjusted hazard ratio [aHR], 1.47; 95% CI, 1.40-1.54; Black children: aHR, 1.30; 95% CI, 1.19-1.42; other race children: aHR, 1.39; 95% CI, 1.29-1.49), compared with White children. For children aged 6 to 10 years, higher risk of tooth decay was observed for Black children (aHR, 1.09; 95% CI, 1.01-1.19) and Hispanic children (aHR, 1.12; 95% CI, 1.07-1.18) compared with White children. For adolescents aged 11 to 18 years, a higher risk of tooth decay was observed only in Black adolescents (aHR, 1.17; 95% CI, 1.06-1.30). A mediation analysis revealed that the association of race and ethnicity with time to first tooth decay became negligible, except for Hispanic and children of other race aged 0 to 5 years, suggesting that mediators explained most of the observed disparities. Insurance type explained the largest proportion of the disparity, ranging from 23.4% (95% CI, 19.8%-30.2%) to 78.9% (95% CI, 59.0%-114.1%), followed by dental procedures (receipt of topical fluoride and restorative procedures) and community-level factors (education attainment and Area Deprivation Index).ConclusionsIn this retrospective cohort study, large proportions of disparities in time to first tooth decay associated with race and ethnicity were explained by insurance type and dental procedure types among children and adolescents. These findings can be applied to develop targeted strategies to reduce oral health disparities.

A graphical user interface for calculating the arterial input function during dynamic positron emission tomography

Purpose. Dynamic positron emission tomography (dPET) requires the acquisition of the arterial input function (AIF), conventionally obtained via invasive arterial blood sampling. To obtain the AIF non-invasively, our group developed and combined two novel solutions consisting of (1) a detector, placed on a patient’s wrist during the PET scans to measure the radiation leaving the wrist and (2) a Geant4-based Monte Carlo simulation software. The simulations require patient-specific wrist geometry. The aim of this study was to develop a graphical user interface (GUI) allowing the user to import 2D ultrasound scans of a patient’s wrist, and measure the wrist features needed to calculate the AIF. Methods. The GUI elements were implemented using Qt5 and VTK-8.2.0. The user imports a patient’s wrist ultrasound scans, measures the radial artery and veins’ surface and depth to model a wrist phantom, then specifies the radioactive source used during the dPET scan. The phantom, the source, and the number of decay events are imported into the Geant4-based Monte Carlo software to run a simulation. In this study, 100 million decays of 18F and 68Ga were simulated in a wrist phantom designed based on an ultrasound scan. The detector’s efficiency was calculated and the results were analyzed using a clinical data processing algorithm developed in a previous study. Results. The detector’s total efficiency decreased by 3.5% for 18F and by 51.7% for 68Ga when using a phantom based on ultrasound scans compared to a generic wrist phantom. Similarly, the data processing algorithm’s accuracy decreased when using the patient-specific phantom, giving errors greater than 1.0% for both radioisotopes. Conclusions. This toolkit enables the user to run Geant4-based Monte Carlo simulations for dPET detector development applications using a patient-specific wrist phantom. Leading to a more precise simulation of the developed detector during dPET and the calculation of a personalized AIF.

New results from the DANSS experiment

We present new results from the DANSS experiment on the searches for sterile neutrinos. They are based on approximately 5 million inverse beta decay events collected at 10.9, 11.9 and 12.9[Formula: see text]m from the reactor core of the 3.1[Formula: see text]GW Kalinin Nuclear Power Plant in Russia. We do not see any statistically significant sign for the [Formula: see text] oscillations. The exclusion area in the [Formula: see text], [Formula: see text] parameter space goes up to [Formula: see text] in the most sensitive region. Plans for DANSS upgrade are presented. This upgrade should allow DANSS to test Neutrino-4 claim of observation of sterile neutrinos.

Enhanced light signal for the suppression of pile-up events in Mo-based bolometers for the 0nu beta beta decay search.

Random coincidences of events could be one of the main sources of background in the search for neutrino-less double-beta decay of ^{100}Mo with macro-bolometers, due to their modest time resolution. Scintillating bolometers as those based on Li_2MoO_4 crystals and employed in the CROSS and CUPID experiments can eventually exploit the coincident fast signal detected in a light detector to reduce this background. However, the scintillation provides a modest signal-to-noise ratio, making difficult a pile-up pulse-shape recognition and rejection at timescales shorter than a few ms. Neganov–Trofimov–Luke assisted light detectors (NTL-LDs) offer the possibility to effectively increase the signal-to-noise ratio, preserving a fast time-response, and enhance the capability of pile-up rejection via pulse shape analysis. In this article we present: (a) an experimental work performed with a Li_2MoO_4 scintillating bolometer, studied in the framework of the CROSS experiment, and utilizing a NTL-LD; (b) a simulation method to reproduce, synthetically, randomly coincident two-neutrino double-beta decay events; (c) a new analysis method based on a pulse-shape discrimination algorithm capable of providing high pile-up rejection efficiencies. We finally show how the NTL-LDs offer a balanced solution between performance and complexity to reach background index sim 10^{-4} counts/keV/kg/year with 280 g Li_2MoO_4 (^{100}Mo enriched) bolometers at 3034 keV, the Q_{beta beta } of the double-beta decay, and target the goal of a next generation experiment like CUPID.

Investigate the potential of using reactor anti-neutrinos for nuclear safeguards in Vietnam

One of the most abundant man-made sources of low energy (few~MeVs) neutrinos, reactor neutrino, is not only useful for studying neutrino properties, but it is also used in practical applications. In this study, we investigate the potential of using reactor neutrino detectors for nuclear safeguards in Vietnam, specifically at the Dalat Nuclear Reactor, a future research facility, and presumably commercial reactors with 500~kW, 10~MW, and 1000~MW thermal powers, respectively. We compute the rate of observed inverted beta decay events, as well as the statistical significance of extracting isotope composition under the practical assumptions of detector mass, detection efficiency, and background level. We find that a 1-ton detector mass can allow us to detect the reactor's on-off transition state from a few hours to a few days, depending on the standoff distance and reactor thermal power. We investigate how background and energy resolution affect the precision of the extracted weapon-usable \(^{239}\)Pu isotope. We conclude that in order to distinguish the 10% variation of the \(^{239}\)Pu in the 10~MW thermal power reactor, a 1-ton detector placed 50~m away must achieve 1% background level. Increasing the statistics by using a 10x larger detector or placing it \(\sqrt{10}\) times closer to the reactor alleviates the requirement of the background level to 10%.

Segmented silicon-based solid-state detector with thin dead layer for superheavy element research

Silicon-based solid-state detectors (SSDs) are crucial for investigating the properties of superheavy elements (SHEs), since they measure the energy of SHEs and charged particles that are emitted as successive decay events of the SHEs. We have developed a segmented SSD for SHE studies using the new gas-filled recoil ion separators (GARIS-II and GARIS-III) at RIKEN. It is based on a back-illuminated Si PIN photodiode in which the irradiation is through the N+ layer. The detector is introduced as a side one for the GARIS focal plane detection system. To investigate the characteristics of the SSD, 241Am α particles were irradiated by automatically moving and rotating the α source for each segmented portion of the SSD. A Monte Carlo simulation was also performed to estimate the dead layer thickness of the segmented SSD.

Topologies of ^{76}Ge double-beta decay events and calibration procedure biases

The analysis of the time profile of electrical signals produced by energy depositions in germanium detectors allows discrimination of events with different topologies. This is especially relevant for experiments searching for the neutrinoless double beta decay of ^{76}Ge to distinguish the sought-after signal from other background sources. The standard calibration procedures used to tune the selection criteria for double-beta decay events use a ^{228}Th source, because it provides samples of signal-like events. These samples exhibit energy spatial distributions with subtle different topologies compared to neutrinoless double-beta decay events. In this work, we will characterize these topological differences and, with the support of a ^{56}Co source, evaluate biases and precision of calibration techniques which use such event samples. Our results will be particularly relevant for future experiments in which a solid estimation of the efficiency is required.

Simulation and test of the SLEGS TOF spectrometer at SSRF

The Shanghai laser electron gamma source (SLEGS) is a powerful tool for exploring photonuclear physics, such as giant dipole resonance (GDR) and pygmy dipole resonance, which are the main mechanisms of collective nuclear motion. The goal of the SLEGS neutron time-of-flight (TOF) spectrometer is to measure GDR and specific nuclear structures in the energy region above the neutron threshold. The SLEGS TOF spectrometer was designed to hold 20 sets of EJ301 and {hbox {LaBr}_{3}} detectors. Geant4 was used to simulate the efficiency of each detector and the entire spectrometer, which provides a reference for the selection of detectors and layout of the SLEGS TOF spectrometer. Under the events of ^{208}hbox {Pb}, implementations of coincidence and time-of-flight technology for complex experiments are available; thus, gamma and neutron decay events can be separated. The performance of SLEGS TOF spectrometer was systematically evaluated using offline experiments, in which the time resolution reached approximately 0.9 ns.

Testing MSW effect in supernova explosion with neutrino event rates

Flavor transition mechanisms of supernova (SN) neutrinos during their propagation deserve a close scrutiny. We present a method to verify Mikheyev-Smirnov-Wolfenstein (MSW) effect during the propagation of SN neutrinos from the SN core to the Earth. The non-MSW scenarios to be distinguished from the MSW one are the incoherent flavor transition probability for neutrino propagation in the vacuum and the flavor equalization induced by fast flavor conversions. Our approach involves studying the time evolution of neutrino event rates in liquid argon, liquid scintillation, and water Cherenkov detectors. The liquid argon detector is sensitive to ${\ensuremath{\nu}}_{e}$ flux while liquid scintillation and water Cherenkov detectors can measure ${\overline{\ensuremath{\nu}}}_{e}$ flux through inverse $\ensuremath{\beta}$ decay process. The flux of ${\ensuremath{\nu}}_{e}$ (${\overline{\ensuremath{\nu}}}_{e}$) is a linear combination of ${\ensuremath{\nu}}_{e}$ (${\overline{\ensuremath{\nu}}}_{e}$) and ${\ensuremath{\nu}}_{\ensuremath{\mu},\ensuremath{\tau}}$ (${\overline{\ensuremath{\nu}}}_{\ensuremath{\mu},\ensuremath{\tau}}$) fluxes from the source with the weighting of each component dictated by the flavor transition mechanism. Using currently available simulations for SN neutrino emissions, the time evolution of ${\ensuremath{\nu}}_{e}\text{Ar}$ and ${\overline{\ensuremath{\nu}}}_{e}$ inverse $\ensuremath{\beta}$ decay event rates and the corresponding cumulative event fractions are calculated up to $t=100\text{ }\text{ }\mathrm{ms}$ in DUNE, JUNO, and Hyper-Kamiokande detectors, respectively. It is shown that the area under the cumulative time distribution curve from $t=0$ to $t=100\text{ }\text{ }\mathrm{ms}$ in each detector and their ratio can be used to discriminate different flavor transition scenarios of SN neutrinos.

Refined electromagnetic analysis of W7-X thermal insulation during fast plasma current decay event

During the second operation phase of the most advanced stellarator Wendelstein 7-X (W7-X) in 2018, a fast plasma current decay event was observed with the time constant of ∼1 ms. The event is much more rapid than the design phase assumptions: 100 kA and 2.7 MA plasma current decay with the time constants of 140 and 50 ms for toroidal and diamagnetic currents, respectively. As a result, significantly higher eddy currents are expected to be induced in some of the W7-X components. The comprehensive campaign of electromagnetic (EM) analyses has been launched in order to identify the necessity of proper reinforcement of critical in-vessel diagnostics or lowering the plasma currents for future operation. One of the critical W7-X system found is the complex thermal insulation (TI).The TI is located in the cryostat to separate cryogenically cooled magnet system and warm vessels. The system consists of actively cooled thermal radiation panels and port tubes, multi-layer insulations, supports and clamps. The TI panels and tubes form the main frame of TI covering the plasma vessel (PV) and ports, respectively. Preliminary EM analysis with few panels and tubes indicates that the EM forces are increased by about 7 times due to the newly postulated faster plasma current decay event in comparison with original design loads. To obtain more accurate results, an elaborated EM model has been created, which includes the excitation coils for toroidal and diamagnetic plasma currents, superconducting coils, TI panels and tubes, the PV and ports.The paper introduces at first the TI structure, continues with the field and eddy current accuracy studies and the lessons learned for the modelling accuracy improvement in ANSYS®. Then the EM analysis results of different plasma current decay scenarios are presented and discussed. Finally, the EM forces for static and transient mechanical analyses are chosen and extracted for further mechanical analyses.

Spectroscopy along flerovium decay chains. III. Details on experiment, analysis, Cn282 , and spontaneous fission branches

Flerovium isotopes (element Z=114) were produced in the fusion-evaporation reactions Ca48+Pu242,244 and studied with an upgraded TASISpec decay station placed in the focal plane of the gas-filled separator TASCA at the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt, Germany. Twenty-nine flerovium decay chains were identified by means of correlated implantation, α decay, and spontaneous fission events. Data analysis aspects and statistical assessments, primarily based on measured rates of various events, which laid the foundation for the comprehensive spectroscopic information on the flerovium decay chains, are presented in detail. Various decay scenarios of an excited state observed in Cn282 are examined in depth with the help of Geant4 simulations and assessed by predictions of beyond mean-field calculations including triaxial shape degrees of freedom. Previous, revised, and newly derived fission probabilities of even-even superheavy nuclei are compared with various theoretical predictions.Received 12 April 2022Revised 19 December 2022Accepted 4 January 2023DOI:https://doi.org/10.1103/PhysRevC.107.024301Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by Bibsam.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasAlpha decayFissionNuclear structure & decaysNuclear Physics

Evolution of the ionic polarization in multiple sequential ionization: General equations and an illustrative example

Modern free-electron lasers generate a highly intense polarized radiation which initiates a sequence of ionization and decay events. Their probability depends on the polarization of each involved state as a function of time. Its complete account is limited by the fact that a state can be formed in various ways. Here we present an equivalent of rate equations for population that completely accounts for polarization of radiation formulated in terms of statistical tensors. To illustrate our approach we theoretically consider the sequential photoionization of krypton by an intense extreme ultraviolet femtosecond pulse for photon energies below the $3d$-shell excitation threshold. The calculations of the ion yields, photoelectron spectra, and ionic polarization for various photon fluences are presented and the role of the polarization is discussed.

Search for hyperon ΔS=ΔQ violating decay Ξ0→Σ−e+νe

Using a data sample of $(1.0087\pm0.0044)\times10^{10}$ $J/\psi$ decay events collected with the BESIII detector at the center-of-mass energy of $\sqrt{s}=3.097$ GeV, we present a search for the hyperon semileptonic decay $\Xi^{0}\to\Sigma^{-}e^{+}\nu_{e}$ which violates the $\Delta S=\Delta Q$ rule. No significant signal is observed, and the upper limit on the branching fraction $\mathcal{B}(\Xi^{0}\to\Sigma^{-}e^{+}\nu_{e})$ is determined to be $1.6\times10^{-4}$ at the 90% confidence level. This result improves the previous upper limit result by about one order of magnitude.

Analysis of Impacts of Window Opening Behavior on Indoor Air Pollutants in Residential Dorms through Deep Neural Network

People spend more than 90% of their time in buildings. The highly stochastic behavior of occupants can alter the pollutants concentration in an indoor space. Many studies have reiterated that window opening is one of the best methods to reduce indoor pollutant concentration. In this study, we analyzed the influence of window opening behavior on indoor pollution parameters (CO2 and TVOC) in 16 student dorms in Syracuse, NY. The duration of the study encompasses all major seasons of a whole year. We found that the window opening behavior of the living room is triggered by the increased concentration of indoor pollutants. The impact of the window opening on the dilution of the concentration of the indoor pollutants is analyzed using the air exchange rates. We found that the average infiltration air exchange rate is 0.32 h-1 and the average air exchange rate during the window opening is 2.20 h-1. The exchange rates are different in different homes; infiltration ACH range from 0.31 - 0.83 h-1, and window opening ACH range from 0.46 - 3.86 h-1. The mean indoor CO2 concentration for all homes ranges between 458 - 715 ppm, and the mean TVOC concentration is 268 - 1786 ppb. The average error in the loss rate calculated from the mass-balance model and the blower door test is 2.51%. We made a Deep Neural Network model predict the concentration of CO2 in the indoor space based on the window's state. The DNN model has an RMSE of 7 ppm and a MAPE of 6.66%. The DNN predicts that the exposure during decay events at the window opening is 80.31% lower than during closed state decay.

From a one-mode to a multi-mode understanding of conical intersection mediated ultrafast organic photochemical reactions.

Over the last few decades, conical intersections (CoIns) have grown from theoretical curiosities into common mechanistic features of photochemical reactions, whose function is to funnel electronically excited molecules back to their ground state in regions where the potential energy surfaces (PESs) of two electronic states become degenerate. Analogous to transition states in thermal chemistry, CoIns appear as transient structures providing a kinetic bottleneck along a reaction coordinate. However, such a bottleneck is not associated with the probability of crossing an energy barrier but rather with an excited state decay probability along a full "line" of transient structures connected by non-reactive modes, the intersection space (IS). This article will review our understanding of the factors controlling CoIn mediated ultrafast photochemical reactions, taking a physical organic chemist approach by discussing a number of case studies for small organic molecules and photoactive proteins. Such discussion will be carried out by first introducing the "standard" one-mode model based on Landau-Zener (LZ) theory to describe a reactive excited state decay event intercepting, locally, a single CoIn along a single direction, and then by providing a modern perspective based on the effects of the phase matching of multiple modes on the same local event, thus redefining and expanding the description of the excited state reaction coordinate. The direct proportionality between the slope (or velocity) along one mode and decay probability at a single CoIn is a widely applied fundamental principle that follows from the LZ model, yet it fails to provide a complete understanding of photochemical reactions whose local reaction coordinate changes along the IS. We show that in these situations, in particular by focussing on rhodopsin double bond photoisomerization, it is mandatory to consider additional molecular modes and their phase relationship approaching the IS, hence providing a key mechanistic principle of ultrafast photochemistry based on the phase matching of those modes. We anticipate that this qualitative mechanistic principle should be considered in the rational design of any ultrafast excited state process, impacting various fields of research ranging from photobiology to light-driven molecular devices.

Citizen participation through volunteered geographic information as equipment for a smart city to monitor urban decay

One of the issues brought on by rapid urbanization is the loss of livability owing to poor waste management, a lack of resources, air pollution, traffic congestion, and outdated buildings and public infrastructure. The idea of a smart city has arisen as one of the potential solutions to this concern. In this study, we havedemonstrated how citizen science helpsimmenselyto the growth of a smart city by crowdsourcing data about urban decay. Tehran, the capital of Iran, which is home to the history of many people's social lives, has begun losing some of its vitality. Municipalities have plans for dealing with urban decline and revival, but we indicate that volunteered geographic information (VGI) would be more effective in turning such ideas into practice. According to our research, there are three different types of organizations active in urban renewal: municipalities, civil and urban planning agencies, and organizations that support tourism and cultural heritage. As a result, we provided a system design that outlines the duties that each institution has in relation to urban renewal. In addition, we suggested a service broker with the capacity to publish VGI in order to offer interoperability related to geographic data and services based on spatial data infrastructure (SDI). Beyond that, various types of urban decay, necessary management procedures, the sequence of information in system components, and the volunteer's behavior confrontingthe system were all specified in the form of an object-oriented design. A prototype system based on state-of-the-art in open-source technologies was developed to test our hypothesis. The VGI system enabled us to monitor urban decay events in real time using the management dashboard. We have shown that volunteers can distinguish between urban declines and typical instances like a binary classifier in the quality control method proposed in this study. Performance was 90% based on the findings of the quality control. A running VGI system would start beneficenceafter 3months and make a profit of 150% after a year, based on our estimates.

Simulation of a novel, non-invasive radiation detector to measure the arterial input function for dynamic positron emission tomography.

Dynamic positron emission tomography (dPET) is a nuclear medicine imaging technique providing functional images for organs of interest with applications in oncology, cardiology, and drug discovery. This technique requires the acquisition of the time-course arterial plasma activity concentration, called the arterial input function (AIF), which is conventionally acquired via arterial bloodsampling. The aim of this study was to (A) optimize the geometry for a novel and cost efficient non-invasive detector called NID designed to measure the AIF for dPET scans through Monte Carlo simulations and (B) develop a clinical data analysis chain to successfully separate the arterial component of a simulated AIF signal from the venouscomponent. The NID was optimized by using an in-house Geant4-based software package. The sensitive volume of the NID consists of a band of 10 cm long and 1mm in diameter scintillating fibers placed over a wrist phantom. The phantom was simulated as a cylinder, 10 cm long and 6.413 cm in diameter comprised of polyethylene with two holes placed through it to simulate the patient's radial artery and vein. This phantom design was chosen to match the wrist phantom used in our previous proof of concept work. Two geometries were simulated with different arrangements of scintillating fibers. The first design used a single layer of 64 fibers. The second used two layers, an inner layer with 29 fibers and an outer layer with 30 fibers. Four positron emitting radioisotopes were simulated: 18 F, 11 C, 15 O, and 68 Ga with 100 million simulated decay events per run. The total and intrinsic efficiencies of both designs were calculated as well as the full width half maximum (FWHM) of the signal. In addition, contribution by the annihilation photons versus positrons to the signal was investigated. The results obtained from the two simulated detector models were compared. A clinical data analysis chain using an expectation maximization maximum likelihood algorithm was tested. This analysis chain will be used to separate arterial counts from the totalsignal. The second NID design with two layers of scintillating fibers had a higher efficiency for all simulations with a maximum increase of 17% total efficiency for 11 C simulation. All simulations had a significant annihilation photon contribution. The signal for 18 F and 11 C was almost entirely due to photons. The clinical data analysis chain was within 1% of the true value for 434 out of 440 trials. Further experimental studies to validate these simulations will berequired. The design of the NID was optimized and its efficiency increased through Monte Carlo simulations. A clinical data analysis chain was successfully developed to separate the arterial component of an AIF signal from the venous component. The simulations show that the NID can be used to accurately measure the AIF non-invasively for dPETscans.

Status of the NEXT experiment.

NEXT is an international experimental program aiming at the detection of 0\U0001d708ββ decay in 136Xe using a high-pressure gaseous xenon electroluminescent TPC. The technique allows for superb energy resolution, 1% FWHM at Q ββ , and topological discrimination based on the unique signature that a double electron produces in a gaseous medium. With ∼0.5 m in each dimension, NEXT-White (NEW) has been operating underground since 2016 at the Laboratorio Subterráneo de Canfranc (LSC), using xenon enriched to 90% 136Xe. Its purpose is to validate all aspects of the technology on a large scale and demonstrate its performance on 2\U0001d708ββ decay events. NEXT-100 will replace NEW and construction will start during 2021. It will deploy ∼97 kg of enriched xenon and demonstrate sensitivity to 0\U0001d708ββ decay half-lives on the scale of 1025 yr.