Nuclear Astrophysics Experiments Research Articles

Overview of High-Performance Timing and Position-Sensitive MCP Detectors Utilizing Secondary Electron Emission for Mass Measurements of Exotic Nuclei at Nuclear Physics Facilities

Timing and/or position-sensitive MCP detectors, which detect secondary electrons (SEs) emitted from a conversion foil during ion passage, are widely utilized in nuclear physics and nuclear astrophysics experiments. This review covers high-performance timing and/or position-sensitive MCP detectors that use SE emission for mass measurements of exotic nuclei at nuclear physics facilities, along with their applications in new measurement schemes. The design, principles, performance, and applications of these detectors with different arrangements of electromagnetic fields are summarized. To achieve high precision and accuracy in mass measurements of exotic nuclei using time-of-flight (TOF) and/or position (imaging) measurement methods, such as high-resolution beam-line magnetic-rigidity time-of-flight (Bρ-TOF) and in-ring isochronous mass spectrometry (IMS), foil-MCP detectors with high position and timing resolution have been introduced and simulated. Beyond TOF mass measurements, these new detector systems are also described for use in heavy ion beam trajectory monitoring and momentum measurements for both beam-line and in-ring applications. Additionally, the use of position-sensitive timing foil-MCP detectors for Penning trap mass spectrometers and multi-reflection time-of-flight (MR-TOF) mass spectrometers is proposed and discussed to improve efficiency and enhance precision.

Physics at the Legnaro National Laboratories: present activities and future challenges

The Legnaro National Laboratories are one of the four INFN laboratories and they are mainly dedicated to experimental nuclear physics and astrophysics, within the field of nuclear structure and dynamics, where heavy ion induced reactions at medium-low energies are involved. Moreover, high level technologies for the construction of particle accelerators and experimental instruments and apparatuses are studied and developed. The laboratory is at present involved in the construction of the SPES facility, which concerns the development of a new research infrastructure devoted to the production of exotic beams for nuclear physics study and new radioisotopes for nuclear medical applications. The heart of SPES is an innovative cyclotron, B70, capable of providing high intensity proton beams (up to 750 μA) in the energy range between 35 and 70 MeV. A description of the present and future challenges at the Legnaro National Laboratory will be given.

KoBRA Wien filter for low-energy RI beam production and recoil separation

The Wien filter is one of the key components in ion optics to improve the mass separation performance. The KoBRA Wien filter will be installed at the low-energy beamline KoBRA of RAON in Korea. The specifications of the KoBRA Wien filter were determined based on the ion beams expected in the KoBRA beamline, especially, beam energies less than about 5 MeV/nucleon suitable for nuclear astrophysics experiments. The Wien filter is designed to have the maximum field intensities of 0.2 T for the magnetic field and 2.0 kV/mm for the electric field in the ±75(H)×±50(V)×2500(L)mm3 good-field region. Performance of the Wien filter was estimated by the ion optics calculations of the KoBRA beamline for 40Ar beams at 18.5 MeV/nucleon and 14O beams at 2.5 MeV/nucleon. The mass resolving powers are 42.65 and 517, respectively. Currently, the KoBRA Wien filter is being manufactured, and will perform a factory acceptance test.

Background gamma measurement for low energy astrophysical reaction at FRENA

The majority of astrophysical reactions have very low cross-sections (nanobarn to picobarn range) and significant error bars [1, 2]. Hence γ-ray background studies up to 3 MeV have been performed inside the Facility for Research in Experimental Nuclear Astrophysics (FRENA), Saha Institute of Nuclear Physics, Kolkata, India. A meticulous background calculation has been performed at different positions inside the accelerator hall and beam hall using two NaI(Tl) detectors [3]. An XPS measurement has been carried out to identify elements present in the FRENA wall concrete. Activity calculations done in [4] shows that neutrons produced by various experiments may combine with any nearby elements and form various radioactive isotopes with long half-lives, which may produce a γ-ray background .

Study for the long-lived gamma background due to neutron emitting calibration reactions

In this article, a detailed theoretical investigation has been done on the long-lived gamma background due to neutron emitting reactions. It mainly focused on the experiments that will be used to calibrate energy with the terminal voltage of an upcoming Facility for Research in Experimental Nuclear Astrophysics (FRENA). Many reactions like (p, n), (p, γ) have been utilized in various accelerator facilities around the globe for energy calibration purposes. Neutron emitting reactions like 7Li(p, n), 13C(p, n), 19F(p, n), 27Al(p, n), etc. have been very commonly used. For such reactions, a significant number of neutrons produced from such experiments can interact with surrounding elements like copper, tantalum, stainless steel (SS304 and SS316), concrete materials,etc. These interactions may create long-lived gamma activity in the vicinity of the accelerator and detection area. Background gammas from these radioactive isotopes can interfere with gamma measurements in future experiments. The present study has been done to investigate those possibilities of gamma background which may occur due to the calibration study by neutron emitting experiments. Here 7Li(p, n), 13C(p, n), 19F(p, n) and 27Al(p, n) reactions having neutron threshold energies 1.8803, 3.2355, 4.2351, 5.8036 MeV respectively are chosen keeping in mind the proton energy available at the facility.

Efficacy of inertial confinement fusion experiments in light ion fusion cross section measurement at nucleosynthesis relevant energies

Inertial confinement fusion (ICF) experiments create a unique laboratory environment in which thermonuclear fusion reactions occur within a plasma, with conditions comparable to stellar cores and the early universe. In contrast, accelerator-based measurements must compete with bound electron screening effects and beam stopping when measuring fusion cross sections at nucleosynthesis-relevant energies. Therefore, ICF experiments are a natural place to study nuclear reactions relevant to nuclear astrophysics. However, analysis of ICF-based measurements must address its own set of complicating factors. These include: the inherent range of reaction energies, spatial and temporal thermal temperature variation, and kinetic effects such as species separation. In this work we examine these phenomena and develop an analysis to quantify and, when possible, compensate for their effects on our inference. Error propagation in the analyses are studied using synthetic data combined with Markov Chain Monte Carlo (MCMC) machine learning. The novel inference techniques will aid in the extraction of valuable and accurate data from ICF-based nuclear astrophysics experiments.

Synthesis of solid mercury targets for nuclear astrophysics experiments

This paper describes several simple and cost-effective ways of making homogeneously thin solid mercury targets useful for nuclear astrophysics experiments at standard ambient temperature and pressure and in vacuum. The methods described here make use of mercury compounds such as mercury(II) acetate, mercury(II) oxide (yellow), mercury(II) chloride, mercury (II) nitrate monohydrate, and mercury(II) sulfide (red). Various methods like drop-casting, wet chemistry, electro-chemical deposition, amalgamation, and pelletization are described. Advantages and disadvantages of each method are described.

Challenges and Requirements in High-Precision Nuclear Astrophysics Experiments

In the 21th century astronomical observations, as well as astrophysical models, have become impressively precise. For a better understanding of the processes in stellar interiors, the nuclear physics of astrophysical relevance—known as nuclear astrophysics—must aim for similar precision, as such precision is not reached yet in many cases. This concerns both nuclear theory and experiment. In this paper, nuclear astrophysics experiments are put in focus. Through the example of various parameters playing a role in nuclear reaction studies, the difficulties of reaching high precision and the possible solutions are discussed.

Charge breeders: Development of diagnostic tools to probe the underlying physics.

Charge breeders were developed more than 20 years ago in the context of radioactive ion beam (RIB) production. The main goal is to boost the charge state of a singly charged RIB to a higher value matching the A/Q of a post-accelerator. In that way, the RIB produced at some tens of keV can efficiently be accelerated to energies in a range of few MeV/u up to several tens of MeV/u, which is of interest for nuclear structure and nuclear astrophysics experiments. Two families of charge breeders have been developed: one based on Electron Cyclotron Resonance Ion Sources (ECRISs) suitable for Continuous Wave (CW) operation and another built around Electron Beam Ion Sources (EBISs) used for pulsed post-accelerators. For many years, experimental studies have been carried out to enhance the charge breeding process and improve the extracted beam quality, i.e., purity, intensity, emittance, and time structure. The evolution of the charge breeders is also closely related to the emergence of new facilities delivering even more exotic beams. Diagnostic tools, such as Faraday cups, beam profile monitors, and emittance scanners, are mandatory to tune the machines and evaluate their performances. However, to go beyond that, a better understanding of plasma physics (in ECRIS) and electron-ion interactions (in EBIS), as well as the 1+ beam characteristics, for instance, energy spread transverse emittance, is needed. Therefore, simulation codes modeling the physics phenomena in both type of charge breeders were developed to support the understanding of experimental outputs and to gain insights into non-observable parameters. Nevertheless, more sophisticated diagnostic tools are required to improve the charge breeding performance and to extend the potential applications toward new RIB facilities. This Review will present the two kinds of charge breeders and their technical evolutions. It will review the diagnostic tools and simulation codes employed for operation and evaluation of the internal physics processes.

Ion-optical developments tailored for experiments with the Super-FRS at FAIR

The future Super-FRS separator-spectrometer at FAIR will provide rare-isotope beams for key experiments in nuclear structure, astrophysics and nuclear reactions. The Super-FRS will use large-aperture magnets, which is important for the acceptance of nuclear reaction products with a large transverse and longitudinal emittance. In the standard ion-optical separator mode, magnetic rigidity analysis in combination with atomic energy-loss will be performed for clean isotopic spatial separation, once in the Pre-Separator and second in the Main-Separator. New ion-optical developments, prepared for different categories of experiments, are presented in this article. The operating modes described in the early publications of the project are updated in the first part of the paper. In the second part, special ion-optical modes mainly for the experiments of the Super-FRS Experiment Collaboration are discussed. This collaboration is the succession of the FRS Collaboration which has concentrated on separator-spectrometer experiments with the present facility at GSI since 1990.

Stable beam experiments in wide energy ranges serving low energy nuclear astrophysics

In experimental nuclear astrophysics it is common knowledge that reaction cross sections must be measured in the astrophysically relevant, low energy ranges or at least as close to them as possible. In most of the cases, however, it is impossible to reach such low energies. The reactions must therefore be studied at higher energies and the cross sections must be extrapolated to lower ones. In this paper the importance of cross section measurements in wide energy ranges are emphasized and a few examples are shown from the areas of hydrogen burning processes and heavy element nucleosynthesis.

Recent Progress of the Trojan Horse Method and Its Application

The Trojan Horse Method(THM) is an important indirect method in experimental nuclear astrophysics. The S(E) factor of a two-body reaction in Gammow energy range related to astrophysics can be extracted from an appropriate three-body reaction measurement above the Coulomb barrier, under the quasi-free reaction condition. The method can overcome the difficulties caused by the Coulomb barrier suppression and the electron screening effect in direct measurement. While no extrapolation is needed, the method can also avoid the uncertainty in the extrapolation process. THM has a wide application in the experimental nuclear astrophysical study, low-energy fusion data measurement, neutron-induced reaction, electron screening effect and other important research fields. After a short introduction of the THM, this paper will focus on some of the most important experimental results in nuclear astrophysics measured by THM recently and the prospect of its future applications. The following key reactions will mainly be discussed: the indirect measurement of the key neutron source reaction \begin{document}$ ^{{\rm{13}}}{\rm{C(\alpha ,n}}{{\rm{)}}^{{\rm{16}}}}{\rm{O}}$\end{document} in the s-process of AGB stars, the indirect measurement of the nuclear reaction related to the fluorine abundance anomaly in AGB stars, as well as the recent hot spot, the indirect measurement results of the carbon burning reaction in medium or massive stars.

Measurement and simulation of gamma-ray background in a low energy accelerator facility

The γ-ray background in the indoor environment has been measured up to 3 MeV to evaluate the feasibility of studying low cross-section (nanobarn to picobarn range) astrophysical reactions at the Facility for Research in Experimental Nuclear Astrophysics (FRENA), Saha Institute of Nuclear Physics, Kolkata. An n-type coaxial HPGe detector with 20% relative efficiency has been placed at different locations in the accelerator and beam halls for the measurement. The measured activity has been compared with that at two laboratories (with standard brick walls) with and without passive and active radiation shieldings. As the halls at FRENA are well shielded by concrete, the contribution of the shielding in indoor γ-ray background has been delineated by simulation using a 4π-geometry model.

Numerical simulations on laser absorption enhancement in hybrid metallo-dielectric nanostructured targets for future nuclear astrophysics experiments

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.

Constraining nuclear properties in Mo94 via a Nb93(p,γ)Mo94 total cross section measurement

Background: The nucleosynthesis of the group of neutron-deficient $p$ nuclei remains an unsolved puzzle in nuclear astrophysics. Among these nuclei, $^{94}\mathrm{Mo}$ is one of the most abundant and is notoriously underproduced in theoretical network calculations. In these networks, the respective cross sections and reaction rates play a crucial role. Since many reactions of astrophysical relevance are not accessible in the laboratory, a global and robust theoretical framework is required to provide reliable predictions.Purpose: Extending the experimental database on the one hand and direct or indirect studies of the respective nuclear physics properties on the other hand are the key tasks of experimental nuclear astrophysics. For this purpose, total cross sections of the $^{93}\mathrm{Nb}(p,\ensuremath{\gamma})^{94}\mathrm{Mo}$ reaction have been measured at proton energies between 2.0 and 5.0 MeV.Methods: In-beam $\ensuremath{\gamma}$-ray spectroscopy has been utilized to measure total cross sections. In general, the total cross sections depend strongly on the $\ensuremath{\gamma}$-ray decay widths in $^{94}\mathrm{Mo}$, which are derived from the $\ensuremath{\gamma}$-ray strength function and the nuclear level density. In our analysis we use a Bayesian optimization analysis to disentangle the effects of the $\ensuremath{\gamma}$-ray strength function and the nuclear level density in $^{94}\mathrm{Mo}$.Results: The total cross-section results reveal a significant discrepancy with respect to formerly published values. We propose parametrizations for the nuclear level density in $^{94}\mathrm{Mo}$ based on the microscopic level densities from Hartree-Fock-Bogoliubov calculations. Moreover, we present $\ensuremath{\gamma}$-ray strength functions for the $E1$ and $M1$ mode in $^{94}\mathrm{Mo}$ that reveal a low-energy enhancement for $M1$ radiation and agree nicely with previous results.Conclusions: A model-independent approach to study $E1$ and $M1$ strength functions has been presented. In general, radiative capture cross sections are a well-suited tool to constrain the reaction rates in reaction networks but also provide insight into the statistical $\ensuremath{\gamma}$-decay behavior of atomic nuclei.

Texas Active Target (TexAT) detector for experiments with rare isotope beams

The TexAT (Texas Active Target) detector is a new active-target time projection chamber (TPC) that was built at the Cyclotron Institute Texas A&M University. The detector is designed to be of general use for nuclear structure and nuclear astrophysics experiments with rare isotope beams. TexAT combines a highly segmented Time Projection Chamber (TPC) with two layers of solid state detectors. It provides high efficiency and flexibility for experiments with low intensity exotic beams, allowing for the 3D track reconstruction of the incoming and outgoing particles involved in nuclear reactions and decays.

Underground Nuclear Astrophysics: pushing direct measurements toward the Gamow window

The aim of experimental nuclear astrophysics is to provide information on the nuclear processes involved in astrophysical scenarios at the relevant energy range. However, the measurement of the cross section of nuclear reactions at low energies present formidable difficulties due to the very low reaction rates often overwhelmed by the background. Several approaches have been proposed and exploited to overcome such severe obstacles: in such frame, the idea to install a low energy - high intensity ion accelerator deep underground, to gain high luminosity while reducing the cosmic ray background, brought more than 25 years ago, to the pilot LUNA experiment. LUNA stands for Laboratory for Underground Nuclear Astrophysics: in the cave under the Gran Sasso mountain (in Italy) first a 50 kV and then a 400 kV single-ended accelerator for protons and alphas were deployed and produced plenty of data mainly on reactions of the H-burning phase in stars. Recently, similar facilities have been installed and/or proposed in other underground laboratories in US and China. LUNA as well is going to make a big step forward, with a new machine in the MV range which will be able to provide intense beams of protons, alphas and carbon ions. The rationale of underground nuclear astrophysics will be presented together with the last updates on the ongoing research programs.

Silicon Carbide detectors: a concrete perspective for nuclear-astrophysics experiments

Silicon Carbide, also known as carborundum, is one of the most interesting materials for the production of detection systems. This contribution presents an overview of the results of SiCILIA activities, an R&D totally funded by INFN. Detector manufacturing and the generalperformance are discussed.

Experiments with low energy ion beam transport into toroidal magnetic fields

Abstract The stellarator-type storage ring for accumulation of multi-Ampere proton, and other intense ion beams with energies in the range of 100 A k e V to 1 A M e V is designed at Goethe university, Frankfurt am Main. The first proposal for beam confinement with high transversal momentum acceptance was presented in EPAC2006. This ring is typically suited for experiments in plasma physics and nuclear astrophysics. The accumulator ring with a closed longitudinal magnetic field is foreseen with a flux density up to 6 − 8 T . For demonstration, experiments were carried out with two toroidal segments operated at room temperature. The beam transport experiments in toroidal magnetic fields were first described in EPAC2008 within the framework of a proposed low energy ion storage ring. The test setup aims at developing a ring injection system with two beam lines representing the main beam line and the injection line. The primary beam line for the experiments was installed and successfully commissioned in 2009. A special diagnostics probe for “in situ” ion beam detection was installed. This modular technique allows online diagnostics of the ion beam along the beam path. In this paper, we present new results on beam transport experiments, with single segment and coupled configuration. The measurements are shown to be in agreement with the numerical model.

Simulation of heat transfer and dissipation in targets used in nuclear astrophysics experiments

This work presents a time-dependent numerical calculation of heat generation and dissipation in targets used in high ion-beam current nuclear astrophysics experiments. The simulation is beneficial for choosing the thickness of targets, maximum ion-beam current and design set-up for cooling of such targets. It is found that for a very thin target (27Al(p,p),12C(p,p)) heat generation inside target is relatively low and a fair amount of high current (few μA) can be used without any melting issue. But in case of thick targets (27Al(p,γ),12C(p,γ)) cooling became essential for the survival of reaction target.