DT Yield Research Articles

A novel hybrid machine learning model for shopping trip estimation: A case study of Tehran, Iran

Online and offline shopping trips have a profound impact on various facets of urban life, including e-commerce, transportation systems, and sustainability. To assess the factors shaping consumers' decisions, we introduce a novel hybrid machine learning model that integrates the Gray Wolf Optimization (GWO) algorithm with a deep Convolutional Neural Network (CNN). This model is applied to predict shopping behavior based on a survey of 1000 active e-commerce users residing in areas 2 and 5 of Tehran. These individuals have made successful purchases through both online and offline services during the final 20 days of 2021. The GWO algorithm plays a pivotal role in selecting optimal features and hyperparameters for the deep Convolutional Neural Network, which is a powerful deep learning model for image recognition and classification. Notably, our model achieves an impressive accuracy of 97.81% while maintaining a MSE of 0.325, having identified seven out of ten key features as the most influential. To gage the effectiveness of our approach, we conduct a comparative analysis with alternative methods. The results unequivocally showcase the superiority of our proposed algorithm, which attains an accuracy of 97.81%. In contrast, other models such as CNN, LSTM, MLP, DT, and KNN yield accuracies of 95.63%, 94.04%, 90.12%, 86.49%, and 80.16%, respectively. This study offers valuable insights for transportation planners, e-commerce managers, and policymakers. Its primary objective is to assist them in formulating effective strategies aimed at reducing transportation costs, curbing pollutant emissions, mitigating urban traffic congestion, and enhancing user satisfaction all while fostering sustainable development.

First bromine doped cryogenic implosion at the National Ignition Facility

We report on the first experiment dedicated to the study of nuclear reactions on dopants in a cryogenic capsule at the National Ignition Facility (NIF). This was accomplished using bromine doping in the inner layers of the CH ablator of a capsule identical to that used in the NIF shot N140520. The capsule was doped with 3 × 1016 bromine atoms. The doped capsule shot, N170730, resulted in a DT yield that was 2.6 times lower than the undoped equivalent. The Radiochemical Analysis of Gaseous Samples (RAGS) system was used to collect and detect 79Kr atoms resulting from energetic deuteron and proton ion reactions on 79Br. RAGS was also used to detect 13N produced dominantly by knock-on deuteron reactions on the 12C in the ablator. High-energy reaction-in-flight neutrons were detected via the 209Bi(n,4n)206Bi reaction, using bismuth activation foils located 50 cm outside of the target capsule. The robustness of the RAGS signals suggests that the use of nuclear reactions on dopants as diagnostics is quite feasible.

A novel photomultiplier tube neutron time-of-flight detector.

A traditional neutron time-of-flight (nTOF) detector used in inertial confinement fusion consists of a scintillator coupled with a photomultiplier tube (PMT). The instrument response function (IRF) of such a detector is dominated by the scintillator-light decay. In DT implosions with neutron yield larger than 1013, a novel detector consisting of a microchannel-plate (MCP) photomultiplier tube in a housing without a scintillator (PMT nTOF) can be used to measure DT yield, ion temperature, and neutron velocity. Most of the neutron signals in PMT nTOF detectors are produced from neutron interaction with a PMT window. The direct interaction of neutrons with the MCP provides negligible contribution. The elimination of the scintillator removes the scintillator decay from the instrument response function and makes the IRF of the PMT nTOF detector faster, which makes the ion temperature and neutron velocity measurements more accurate. Three PMT nTOF detectors were deployed in the OMEGA laser system for the first time to diagnose inertial confinement fusion plasma. The design details, characteristics, and calibration results of these detectors in DT implosions on OMEGA are presented. Recommendations on the use of different PMTs for specific applications are provided.

Using a 2-shock 1D platform at NIF to measure the effect of convergence on mix and symmetry

We describe the use of a robust new 1-D like implosion platform at the National Ignition Facility [G. H. Miller et al., Opt. Eng. 43, 2841 (2004)] to study the effect of convergence on mix and shape. Previous experiments suggest that nuclear yields and ion temperature degrade with increased convergence [M. D. Cable et al., Phys. Rev. Lett. 73, 2316 (1994)] due to enhanced perturbation growth and mix, but little has been reported on the distortion of the shape with time. The 2-shock platform was developed [S. F. Khan et al., Phys. Plasmas 23, 042708 (2016)] to maintain a high degree of sphericity during the whole implosion phase and has a thick, uniformly doped (1% Si) plastic CH shell to minimize the effect of mixing due to hydrodynamic feed-through from the outer ablator surface. An inner layer of deuterated plastic (CD) and hydrogen-tritium (DT) gas fill allows for the measurement of DT neutrons produced by the mix between the gas and ablator. DD neutrons provide information about the hot, unmixed CD region. By changing the fill gas density while keeping the capsule diameter, ablator thickness, and Au hohlraum conditions fixed, the x-ray hot spot convergence ratio was varied from 14 to 22. We find that the atomic mix (DT yield) grows linearly as a function of convergence, but since Tion changes as well, it does not necessarily mean that the amount or extent of mix grows linearly as well. We also find the DD yield, which is a measurement of the shell heating, saturates above a certain convergence.

Testing a Cherenkov neutron time-of-flight detector on OMEGA.

A Cherenkov neutron time-of-flight (nTOF) detector developed and constructed at Lawrence Livermore National Laboratory was tested at 13 m from the target in a collimated line of sight (LOS) and at 5.3 m from the target in the open space inside the OMEGA Target Bay. Neutrons interacting with the quartz rod generate gammas, which through Compton scattering produce relativistic electrons that give rise to Cherenkov light. A photomultiplier tube (PMT) transferred the Cherenkov light into an amplified electrical signal. The Cherenkov nTOF detector consists of an 8-mm-diam, 25-cm quartz hexagonal prism coupled with a Hamamatsu gated PMT R5916U-52. The tests were performed with DT direct-drive implosions with cryogenic and room-temperature targets, producing a wide range of neutron yields and ion temperatures. The results of the tests and comparison with other nTOF detectors on OMEGA are presented. In the collimated LOS at 13 m from the target, the Cherenkov nTOF detector demonstrated good precision measurement in both the yield and ion temperature for DT yields above 3 × 1013.

Optimal biodiesel-additive synthesis under infrared excitation using pork bone supported-Sb catalyst: Engine performance and emission analyses

Glycerol (G) acetic acid (AA) esterification was conducted in an infrared irradiation (IRI) aided batch reactor for maximization of diacetin and triacetin yield (DT) using pork bone derived hydroxyapatite supported antimony (Sb) oxide catalyst. The catalyst possessed appreciable 40m2/g specific surface area; 4.5nm modal pore diameter and 0.0485cc/g pore volume with prominent Sb2O5 crystalline phase. Under derived optimal condition, 40% Sb precursor loading, 100°C reaction temperature and 6:1 AA:G mole ratio resulted maximum DT yield (88±1%). Notably, to achieve maximum DT yield (88±1%), conventionally heated batch reactor consumed 6 times more energy (reaction time 6h at 300J/s energy input rate) in comparison with IRI reactor (reaction time 2h at 150J/s energy input rate), indicating remarkable energy-efficiency of IRI. Additionally, synthesized product as additive to palm biodiesel evinced emission reduction by 50% and 20% for CO and HC respectively with 2 degrees depression in pour point.

Detailed high-resolution three-dimensional simulations of OMEGA separated reactants inertial confinement fusion experiments

We present results from the comparison of high-resolution three-dimensional (3D) simulations with data from the implosions of inertial confinement fusion capsules with separated reactants performed on the OMEGA laser facility. Each capsule, referred to as a “CD Mixcap,” is filled with tritium and has a polystyrene (CH) shell with a deuterated polystyrene (CD) layer whose burial depth is varied. In these implosions, fusion reactions between deuterium and tritium ions can occur only in the presence of atomic mix between the gas fill and shell material. The simulations feature accurate models for all known experimental asymmetries and do not employ any adjustable parameters to improve agreement with experimental data. Simulations are performed with the RAGE radiation-hydrodynamics code using an Implicit Large Eddy Simulation (ILES) strategy for the hydrodynamics. We obtain good agreement with the experimental data, including the DT/TT neutron yield ratios used to diagnose mix, for all burial depths of the deuterated shell layer. Additionally, simulations demonstrate good agreement with converged simulations employing explicit models for plasma diffusion and viscosity, suggesting that the implicit sub-grid model used in ILES is sufficient to model these processes in these experiments. In our simulations, mixing is driven by short-wavelength asymmetries and longer-wavelength features are responsible for developing flows that transport mixed material towards the center of the hot spot. Mix material transported by this process is responsible for most of the mix (DT) yield even for the capsule with a CD layer adjacent to the tritium fuel. Consistent with our previous results, mix does not play a significant role in TT neutron yield degradation; instead, this is dominated by the displacement of fuel from the center of the implosion due to the development of turbulent instabilities seeded by long-wavelength asymmetries. Through these processes, the long-wavelength asymmetries degrade TT yield more than the DT yield and thus bring DT/TT neutron yield ratios into agreement with experiment. Finally, we present a detailed comparison of the flows in 2D and 3D simulations.

Simulations of symcap and layered NIF experiments with top/bottom laser asymmetry to impose P1 drive on capsules

Integrated hohlraum/capsule post-shot simulation of the first full-scale cryogenic layered-DT experiment with top/bottom laser asymmetries of 8% is discussed. The imposed P1 Legendre mode drive on the capsule results in downward velocity of 85 ± 15 km/s as measured by neutron time of flight (NTOF) diagnostics and x-ray imagers, which is in excellent agreement with the calculated velocity of 87 km/s. The measured DT yield is approximately 30% less than the average of two comparable shots using the same 4 shock HiFoot pulse shape without drive asymmetry. The calculated DT yield of 5.0e15 is very close to the measured value of 4.86e15 for the shot with drive asymmetry, which implies that P1 effects dominate yield reduction. The neutron activation diagnostics (NADs) give clear indication of higher areal density in the direction of the north pole in excellent agreement with calculations. Integrated post-shot simulation of an earlier symcap (capsule with appropriate ablator thicknesses to act as a surrogate for an ignition capsule) experiment with laser asymmetries show that calculated neutron-wighted velocity is a strong function of capsule shape.

Development of the CD Symcap platform to study gas-shell mix in implosions at the National Ignition Facility

Surrogate implosions play an important role at the National Ignition Facility (NIF) for isolating aspects of the complex physical processes associated with fully integrated ignition experiments. The newly developed CD Symcap platform has been designed to study gas-shell mix in indirectly driven, pure T2-gas filled CH-shell implosions equipped with 4 μm thick CD layers. This configuration provides a direct nuclear signature of mix as the DT yield (above a characterized D contamination background) is produced by D from the CD layer in the shell, mixing into the T-gas core. The CD layer can be placed at different locations within the CH shell to probe the depth and extent of mix. CD layers placed flush with the gas-shell interface and recessed up to 8 μm have shown that most of the mix occurs at the inner-shell surface. In addition, time-gated x-ray images of the hotspot show large brightly radiating objects traversing through the hotspot around bang-time, which are likely chunks of CH/CD plastic. This platform is a powerful new capability at the NIF for understanding mix, one of the key performance issues for ignition experiments.

Design of a High-Foot High-Adiabat ICF Capsule for the National Ignition Facility

The National Ignition Campaign's [M. J. Edwards et al., Phys. Plasmas 20, 070501 (2013)] point design implosion has achieved DT neutron yields of 7.5×10(14) neutrons, inferred stagnation pressures of 103 Gbar, and inferred areal densities (ρR) of 0.90 g/cm2 (shot N111215), values that are lower than 1D expectations by factors of 10×, 3.3×, and 1.5×, respectively. In this Letter, we present the design basis for an inertial confinement fusion capsule using an alternate indirect-drive pulse shape that is less sensitive to issues that may be responsible for this lower than expected performance. This new implosion features a higher radiation temperature in the "foot" of the pulse, three-shock pulse shape resulting in an implosion that has less sensitivity to the predicted ionization state of carbon, modestly lower convergence ratio, and significantly lower ablation Rayleigh-Taylor instability growth than that of the NIC point design capsule. The trade-off with this new design is a higher fuel adiabat that limits both fuel compression and theoretical capsule yield. The purpose of designing this capsule is to recover a more ideal one-dimensional implosion that is in closer agreement to simulation predictions. Early experimental results support our assertions since as of this Letter, a high-foot implosion has obtained a record DT yield of 2.4×10(15) neutrons (within ∼70% of 1D simulation) with fuel ρR=0.84 g/cm2 and an estimated ∼1/3 of the yield coming from α-particle self-heating.

Copper activation deuterium-tritium neutron yield measurements at the National Ignition Facility

A DT neutron yield diagnostic based on the reactions, (63)Cu(n,2n)(62)Cu(β(+)) and (65)Cu(n,2n)( 64) Cu(β(+)), has been fielded at the National Ignition Facility (NIF). The induced copper activity is measured using a NaI γ-γ coincidence system. Uncertainties in the 14-MeV DT yield measurements are on the order of 7% to 8%. In addition to measuring yield, the ratio of activities induced in two, well-separated copper samples are used to measure the relative anisotropy of the fuel ρR to uncertainties as low as 5%.

Deuterium–tritium neutron yield measurements with the 4.5 m neutron-time-of-flight detectors at NIF

The first several campaigns of laser fusion experiments at the National Ignition Facility (NIF) included a family of high-sensitivity scintillator∕photodetector neutron-time-of-flight (nTOF) detectors for measuring deuterium-deuterium (DD) and DT neutron yields. The detectors provided consistent neutron yield (Y(n)) measurements from below 10(9) (DD) to nearly 10(15) (DT). The detectors initially demonstrated detector-to-detector Y(n) precisions better than 5%, but lacked in situ absolute calibrations. Recent experiments at NIF now have provided in situ DT yield calibration data that establish the absolute sensitivity of the 4.5 m differential tissue harmonic imaging (DTHI) detector with an accuracy of ± 10% and precision of ± 1%. The 4.5 m nTOF calibration measurements also have helped to establish improved detector impulse response functions and data analysis methods, which have contributed to improving the accuracy of the Y(n) measurements. These advances have also helped to extend the usefulness of nTOF measurements of ion temperature and downscattered neutron ratio (neutron yield 10-12 MeV divided by yield 13-15 MeV) with other nTOF detectors.

Evidence for Stratification of Deuterium-Tritium Fuel in Inertial Confinement Fusion Implosions

Measurements of the D(d,p)T (dd) and T(t,2n)(4)He (tt) reaction yields have been compared with those of the D(t,n)(4)He (dt) reaction yield, using deuterium-tritium gas-filled inertial confinement fusion capsule implosions. In these experiments, carried out on the OMEGA laser, absolute spectral measurements of dd protons and tt neutrons were obtained. From these measurements, it was concluded that the dd yield is anomalously low and the tt yield is anomalously high relative to the dt yield, an observation that we conjecture to be caused by a stratification of the fuel in the implosion core. This effect may be present in ignition experiments planned on the National Ignition Facility.

Design of High-Neutron-Yield, Polar-drive targets for diagnostic activation experiments on the NIF

Polar-drive (PD) target implosions have been designed for neutron diagnostic development on the NIF. These experiments use thin, room-temperature glass shells filled with low pressures of DT. Initial target implosions on the NIF will produce DT yields in the range of a few 1014 neutrons. The predicted yields are consistent with earlier data (1014 neutrons at 30 kJ) and recent PD scoping experiments performed on OMEGA. The experiments will use existing x-ray-drive phase plates with judicious repointing and defocusing to drive the implosions as uniformly as possible. These implosions have been modeled with three codes: LILAC, to optimize the 1-D design; SAGE, to optimize the pointing uniformity; and DRACO, to predict the yield from 2-D implosion simulations. Current simulation results indicate that the required yields will be obtained using up to 200-kJ UV light formed into a 1500-ps Gaussian pulse. Large-diameter glass shells (∼1500-μm OD) are under development and fabrication at General Atomics. As tritium and environmental conditions evolve, similar target designs, with larger diameters and higher laser energies, are expected to produce thermonuclear yields approaching 1016 neutrons.

Crop Mineral Nutrient and Yield Responses to Aphids or Barley Yellow Dwarf Virus in Spring Wheat and Oat

Root system biomass reductions caused by aphid feeding or aphid‐transmitted viral disease may affect root system function in spring wheat (Triticum aestivum L.) or oat (Avena sativa L.). A 2‐yr field experiment was conducted to determine how leaf mineral nutrients (N, P, K, Ca, Mg, Zn, Fe, Mn, and Cu), chlorophyll (chl), and agronomic traits (leaf area index [LAI], leaf area plant−1, midday differential canopy temperature deviation from control [dT], yield, and yield components) responded to crop stress imposed by aphid feeding (greenbugs [GB], Schizaphis graminum Rondani; Russian wheat aphids [RWA], Diuraphis noxia Mordvilko; bird cherry‐oat aphids [BCOA], Rhopalosiphum padi L.) or by an aphid‐vectored virus (barley yellow dwarf virus, Luteovirus, PAV strain [BYDV]). Leaf chl, N, Ca, and Mg concentrations (measured at the boot development stage) were about 25% less in BYDV‐infected than control treatments. Grain yield deviation from control (dY) was most negative for BYDV treatment (−2164.5 kg ha−1) and least negative for GB treatment (−745.5 kg ha−1), with RWA (−900.6 kg ha−1) and BCOA (−789 kg ha−1) treatments having intermediate effects. Mineral nutrients (N, K, Mg, and Mn) and chl were significantly correlated (Canonical r = 0.94, p < 0.0001) with agronomic traits (LAI, dT, leaf area, and grain yield), and explained 62.1% of the variation in agronomic traits. Thus, leaf concentrations of certain chemical constituents of cereal plants are highly correlative to agronomic traits important in cereal plant responses to stress caused by aphid‐feeding damage or aphid‐vectored disease.

Carbon activation diagnostic for tertiary neutron measurements

The yield of tertiary neutrons with energies greater than 20 MeV has been proposed to determine the high ρR of inertial confinement fusion targets. The activation of carbon is a valuable measurement technique because of its high reaction threshold, the availability of high-purity samples, and relatively low cost. The C12(n,2n)11C reaction has a Q value of 18.7 MeV, well above the 14.1 MeV primary DT neutron energy. The isotope C11 decays with a half-life of 20.3 min and emits a positron, resulting in the production of two back-to-back, 511 keV gamma rays upon annihilation. The positron decay of C11 is nearly identical to the copper decay used in the activation measurements of 14.1 MeV primary DT yields; therefore, the present copper activation gamma-detection system can be used to detect the tertiary-produced carbon activation. Because the tertiary neutron yield is more than six orders of magnitude lower than primary neutron yield, the carbon activation diagnostic requires ultrapure carbon samples, free from any positron-emitting contamination. In recent years we have developed carbon purification, packaging, and handling procedures that minimize the contamination signal to a level low enough to use carbon activation for tertiary neutron measurements in direct-drive implosion experiments with DT cryogenic targets on OMEGA. Experimental results of contamination measurements in carbon samples performed on high-neutron-yield shots on OMEGA in 2001–2002 will be presented. A concept for implementing a carbon activation system on the National Ignition Facility (NIF) will be discussed.

Calibration of the JET neutron activation system for DT operation

The neutron activation system at JET is a pneumatic transfer system capable of positioning activation samples close to the plasma. Its primary purpose is to provide a calibration for the time-dependent neutron yield monitors (fission chambers and solid state detectors). Various activation reactions with different high energy thresholds were used including Fe56(n,p) Mn56, Al27(n,α) 24Na, 93Nb(n,2n) 92mNb, and Si28(n,p) 28Al reactions. The silicon reaction, with its short half life (2.25 min), provides a prompt determination of the 14 MeV DT yield. The neutron induced γ-ray activity of the Si samples was measured using three sodium iodide scintillators, while two high purity germanium detectors were used for other foils. It was necessary to use a range of sample masses and different counting geometries in order to cover the wide range of neutron yields (1015–1019 neutrons) while avoiding excessive count rates in the detectors. The absolute full energy peak efficiency calibration of the detectors was measured taking into account the source-detector geometry, the self-attenuation of the samples and cross-talk effects. An error analysis of the neutron yield measurement was performed including uncertainties in efficiency calibration, neutron transport calculations, cross sections, and counting statistics. Cross calibrations between the different irradiation ends were carried out in DD and DT (with 1% and 10% tritium content) discharges. The effect of the plasma vertical displacement was also experimentally studied. An agreement within 10% was found between the 14 MeV neutron yields measured from Si, Fe, Al, Nb samples in DT discharges.

Design of an electronic charged particle spectrometer to measure 〈ρ𝓡〉 on inertial fusion experiments

The design and fabrication of a new diagnostic that measures the energy spectra of charged particles from targets on the Omega Upgrade are actively underway. Using seven 512×512 charge coupled devices (CCDs) and a 7.5 kG permanent magnet, this instrument will uniquely determine particle identities and measure particle energies from 1 MeV up to the maximum charged particle energies of interest for ρR measurements (10.6 MeV knock-on tritons, 12.5 MeV knock-on deuterons and 30.8 MeV tertiary protons). The resolution of the diagnostic will be better than 5%. We have tested the response of SITe back-illuminated CCDs to 1.2–13.6 MeV protons from our Cockcroft–Walton accelerator and to alpha particles from an Am241 source, and the results agree extremely well with predictions. With its high density picture elements, each CCD has 105 single-hit detectors. In the case of a low DT yield of 109 neutrons, about 100 knock-on charged particles will be detected when the spectrometer aperture is 60 cm from the implosion. Measurements of ρR up to 150 mg/cm2 can be obtained from knock-on D and T spectra, and values up to 300 mg/cm2 can be determined from secondary proton spectra. The sensitivity of the CCDs to 14 and 2.5 MeV neutrons has been experimentally determined using our Cockcroft–Walton accelerator source and indicates that by incorporating neutron shielding, the signal to neutron noise ratio at a yield of 1011 will be better than 100:1. In the development phases of this program, we plan to utilize CR-39 track detectors concurrently with the CCDs.

Effect of rotational quantum states ( J=0, 1) on the tunneling reaction H 2+T→H+HT in xenon—hydrogen mixtures at 77 K

The effect of rotational quantum states ( J=0, 1) on the tunneling reaction H 2+T→H+HT in solid Xe-H 2-D 2 mixtures has been studied at 77 K. When T atoms are produced by a 6Li(n, α)T reaction in xenon—hydrogen (1 mol%) mixtures, most recoil T atoms are thermalized before encountering the solute hydrogen at 1 mol% and react with H 2 and D 2 by tunneling to produce HT and DT. The ratio of HT to DT yields, [HT]/[DT], in the Xe- p-H 2 ( J=0)-D 2 mixtures is larger than the [HT]/[DT] ratio in Xe- n-H 2-D 2 mixtures, where n-H 2 consists of 75% o-H 2 ( J=1) and 25% p-H 2. The ratio of the rate constant for the tunneling reaction H 2( J=0) + T→H+HT to that for the tunneling reaction H 2( J=1) +T → H+HT, i.e. k(H 2( J=0)+T)/ k(H 2( J=1)+T), was estimated as 4±2 from HT yields.

Recoil tritium reaction in solid hydrogen at ultralow temperatures

Reactions of recoil T atoms were studied in solid H 2 -D 2 mixtures at 4.2 K. The fraction of HT in the sum of HT and DT yields, [HT]/([HT]+[DT]), is roughly equal to the mole fraction of H 2 in the H 2 -D 2 mixtures. These yields were compared with the yields of H atoms produced by γ-radiolysis of the H 2 -D 2 mixtures at 4.2 K. From the comparison, it was concluded that formation of HT could not be due to combination of thermalized T atoms with hydrogen atoms from γ-radiolysis of solid hydrogen during reactor irradiation but must be due to hydrogen atom abstraction by recoil T atoms from H 2 and D 2