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Difference between even- and odd-numbered cycles in the predictability of solar activity and prediction of the amplitude of cycle 25
摘要： It was shown previously that the sunspot number (SSN) at a point 3 years before the minimum is well correlated with the maximum SSN of the succeeding cycle, and a better correlation is obtained when the maximum SSN is replaced by the average SSN over a cycle for which the average SSN is calculated by dividing cycles at a point 3 years before the minimum (Yoshida and Yamagishi, 2010; Yoshida and Sayre, 2012). Following these findings, we demonstrate in this paper that the correlation between the SSN 3 years before the minimum and the amplitude of the coming cycle differs significantly between even-numbered and odd-numbered cycles: the correlation is much better for even-numbered cycles. Further, it is shown that the amplitude of even-numbered cycles is strongly correlated with that of the succeeding odd-numbered cycles, while the correlation between amplitudes of odd-numbered cycles and those of succeeding even-numbered cycles is very poor. Using the excellent correlations, we estimate the maximum SSN of the current cycle 24 at 81.3 and predict the maximum SSN of cycle 25 to be 115.4 ± 11.9. It is of note, however, that a peak of the SSN has been observed in February 2012 and the peak value 66.9 is considerably smaller than the estimated maximum SSN of cycle 24. We conjecture that the second higher peak of the SSN may appear.
关键词： and astronomy (general or miscellaneous),Solar physics,astrophysics
更新于2025-09-23 15:22:29
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Time Projection Chamber (TPC) detectors for nuclear astrophysics studies with gamma beams
摘要： Gamma-Beams at the HI??S facility in the USA and anticipated at the ELI-NP facility, now constructed in Romania, present unique new opportunities to advance research in nuclear astrophysics; not the least of which is resolving open questions in oxygen formation during stellar helium burning via a precise measurement of the12C(??, ??) reaction. Time projection chamber (TPC) detectors operating with low pressure gas (as an active target) are ideally suited for such studies. We review the progress of the current research program and plans for the future at the HI??S facility with the optical readout TPC (O-TPC) and the development of an electronic readout TPC for the ELI-NP facility (ELITPC).
关键词： Gamma-beams,Time Projection Chamber,Optical readout,Stellar helium burning,Nuclear astrophysics,Electronic readout
更新于2025-09-23 15:22:29
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Numerical simulations on laser absorption enhancement in hybrid metallo-dielectric nanostructured targets for future nuclear astrophysics experiments
摘要： The linear electromagnetic interaction between innovative hybrid metallo-dielectric nanostructured targets and laser in visible and IR range is investigated through numerical simulations. The obtained results rely on the optimization of a target based on metallic nanowires (NWs) to enhance light absorption in the visible range of the electromagnetic spectrum. The NWs are grown within the ordered nanoholes of an alumina substrate, thus, forming a plasmonic lattice with triangular symmetry. The remaining volume of the nanoholes on top of the NWs is sealed with a transparent layer of aluminum oxide that is suitable to be chemically modified for containing about 25% of deuterium atoms. The study presented here is carried out within the framework of a scientific program named PLANETA (Plasmonic Laser Absorption on Nano-Engineered Targets) aiming at investigating new laser–matter interaction schemes in the ns domain and for nuclear fusion purposes, involving especially the D–D reaction.
关键词： D–D reaction,metallo-dielectric nanostructured targets,nuclear astrophysics,laser absorption,plasmonic lattice
更新于2025-09-23 15:21:01
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Rays via Single-Shot Laser-Electron Interaction
摘要： Generation of circularly polarized (CP) and linearly polarized (LP) γ rays via the single-shot interaction of an ultraintense laser pulse with a spin-polarized counterpropagating ultrarelativistic electron beam has been investigated in nonlinear Compton scattering in the quantum radiation-dominated regime. For the process simulation, a Monte Carlo method is developed which employs the electron-spin-resolved probabilities for polarized photon emissions. We show efficient ways for the transfer of the electron polarization to the high-energy photon polarization. In particular, multi-GeV CP (LP) γ rays with polarization of up to about 95% can be generated by a longitudinally (transversely) spin-polarized electron beam, with a photon flux meeting the requirements of recent proposals for the vacuum birefringence measurement in ultrastrong laser fields. Such high-energy, high-brilliance, high-polarization γ rays are also beneficial for other applications in high-energy physics, and laboratory astrophysics.
关键词： nonlinear Compton scattering,electron-spin-resolved probabilities,high-energy physics,Monte Carlo method,circularly polarized γ rays,vacuum birefringence,quantum radiation-dominated regime,laboratory astrophysics,linearly polarized γ rays
更新于2025-09-23 15:19:57
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Modeling radiative-shocks created by lasera??cluster interactions
摘要： Radiative-shocks induced by laser–cluster interactions are modeled using radiation-hydrodynamic simulations. A good agreement—in both shock velocity and density pro?les—is obtained between experiment and simulations, indicating that non-local thermodynamic equilibrium (NLTE) radiative effects are important in the experimental regime examined, particularly at early times ((cid:2)30 ns) due to the elevated temperatures ((cid:3)35 eV). The enhanced NLTE radiative emission causes the shock to be reduced in amplitude, increased in width, and reduced in propagation velocity, while the amplitude of the radiative precursor is increased. As the density and temperature conditions are relatively modest, this potentially has important implications for the scalings that are used in laboratory–astrophysics to transform between laboratory and astrophysical scales, which do not hold for non-LTE systems.
关键词： non-local thermodynamic equilibrium,laboratory–astrophysics,radiation-hydrodynamic simulations,radiative-shocks,laser–cluster interactions
更新于2025-09-23 15:19:57
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Experimental Observation of Ion–Ion Acoustic Instability Associated with Collisionless Shocks in Laser-produced Plasmas
摘要： We report experimental evidence of ion–ion acoustic instability in laser-produced astrophysically relevant plasma. Irradiation of a copper foil with a short (2 ps) intense (1017 W cm?2) laser pulse generates dense hot plasma, whose expansion into the rare?ed preplasma generates the electrostatic collisionless shock. A shock-re?ected ion beam penetrates through the shock upstream excites the ion–ion acoustic instability. The shock oscillation electric ?eld and the instability ?lamentary modulation are monitored by proton radiography. Particle-in-cell and particle-tracing simulations reproduce the experimental observation.
关键词： Laboratory astrophysics,collisionless shocks,laser-produced plasmas,ion–ion acoustic instability
更新于2025-09-19 17:13:59
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[IEEE 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Sydney, Australia (2018.11.10-2018.11.17)] 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC) - Development of Sealed Tube Microchannel Plate Detectors with Cross Strip Readouts
摘要： Cross strip readout anodes provide a novel high spatial resolution image encoding system for microchannel plate sensors. We have developed cross strip readouts with metal & ceramic layers for 50 mm format sealed tubes based on the “Planacon” concept. These have next generation atomic layer deposited microchannel plates for amplification and selected photocathodes covering the UV and optical regimes. These devices will be relevant for the next generation of moderate and large NASA astrophysics instruments that are baselining 50 mm to 200 mm format detectors. The critical elements of the sensors are high QE, high spatial resolution and large event rate limits, with long lifetimes. Our photocathode work includes customization of bialkali semitransparent cathodes with response from 120 nm to 320 nm and a sharp 360 nm cutoff. Opaque alkali halide photocathodes on the atomic layer deposited microchannel plates have shown high quantum efficiencies (50% @ 115 nm) and could be used simultaneously with bialkali photocathodes. The atomic layer deposited microchannel plates have borosilicate substrates which are robust and can be be produced in large formats (20 × 20 cm) with high open area ratios (~73%). These MCPs have very low intrinsic background (<0.06 events/sec/cm2), high gain, and very good lifetime stability. With the cross strip readout and encoding electronics we achieve high spatial resolutions (<20 μm FWHM) over both 50 mm and 100 mm formats at event rates exceeding 5 MHz, providing a powerful baseline for future NASA UV/optical instruments.
关键词： photocathodes,atomic layer deposited microchannel plates,Cross strip readout,UV and optical regimes,microchannel plate sensors,NASA astrophysics instruments
更新于2025-09-16 10:30:52
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Nuclear Astrophysics with Lasers
摘要： A systematic program of investigations of nuclear reactions in laser-produced plasmas is addressed. Such reactions provide an important diagnostic tool for probing the dynamics and thermodynamics in the plasma and understanding laser ion acceleration and neutron production mechanisms. The goal will be to reach the level of knowledge that allows the measurement of fundamental nuclear cross-sections at low and high particle densities. The quantitative measurement of fusion probabilities in hot and dense plasmas will contribute significantly to our comprehension of stellar composition and evolution and will provide important information for development of fusion energy production and applications such as medical isotope production and compact neutron source development. All of these are some of the main goals of the European Extreme Light Infrastructure (ELI), the Shanghai Superintense Ultrafast Laser Facility, and the Station of Extreme Light in China and similar projects in other countries.
关键词： Fusion Reactions,Nuclear Astrophysics,Lasers,Cross-sections,Plasma
更新于2025-09-16 10:30:52
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Design and fabrication of gas cell targets for laboratory astrophysics experiments on the Orion high-power laser facility
摘要： This paper describes the design and fabrication of a range of ‘gas cell’ microtargets produced by the Target Fabrication Group in the Central Laser Facility (CLF) for academic access experiments on the Orion laser facility at the Atomic Weapons Establishment (AWE). The experiments were carried out by an academic consortium led by Imperial College London. The underlying target methodology was an evolution of a range of targets used for experiments on radiative shocks and involved the fabrication of a precision machined cell containing a number of apertures for interaction foils or diagnostic windows. The interior of the cell was gas-?lled before laser irradiation. This paper details the assembly processes, thin ?lm requirements and micro-machining processes needed to produce the targets. Also described is the implementation of a gas-?ll system to produce targets that are ?lled to a pressure of 0.1–1 bar. The paper discusses the challenges that are posed by such a target.
关键词： microtargets,astrophysics
更新于2025-09-11 14:15:04
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The Analysis of Starlight (Two Centuries of Astronomical Spectroscopy) || The interpretation of stellar spectra and the birth of astrophysics
摘要： The interpretation of stellar spectra and the birth of astrophysics. At the end of the nineteenth century the two main branches of stellar spectroscopy were spectral classification and radial-velocity measurements. The latter department was still in its relative infancy, but classification, thanks mainly to the energy of Pickering at Harvard, was a major activity. Classification had become closely related to theories of stellar evolution and these two aspects could hardly be disentangled in, for example, the classification devised by Lockyer [1], which involved first rising and then falling temperatures of stars over their life cycles, and which had some theoretical support from the work of Jonathan Homer Lane (1819–80) and August Ritter on the gravitational collapse of gaseous spheres.
关键词： stellar evolution,spectral classification,stellar spectra,astrophysics,radial-velocity measurements
更新于2025-09-10 09:29:36