Properties Of Vacuum Research Articles

Effect of activation temperature on photon-stimulated desorption from Ti-Zr-V coated copper chambers

Non-evaporable getter (NEG) films featuring distributed pumping properties and low photon-stimulated desorption (PSD) are widely utilized in particle accelerators, especially in diffraction limited storage rings (DLSR) with compact design. Activation is a requisite operation to sustain the pumping capacity of NEG films. Meanwhile, the vacuum properties of NEG films vary with activation temperature. In this work, the dependence of the PSD from NEG films is evaluated with the activation temperature. The columnar Ti-Zr-V films were deposited on the inner surface of the copper vacuum chamber by DC magnetron sputtering. The effect of activation temperature ranging from 150 to 200 °C and nitrogen venting on the PSD of Ti-Zr-V films was investigated. The results indicate that with elevating the activation temperature, the initial PSD yield of the Ti-Zr-V coated chamber consistently declines. Furthermore, the initial desorption of Ti-Zr-V films after nitrogen venting is between that of the non-activated state and the activated state.

Effects of Cu Coating Addition on Mechanical Properties of Vacuum Brazed Joints

In this study, a copper brazing filler metal coating is fabricated on a 304 stainless steel (304SS) substrate using an electroplating technique. The effect of using electroplated copper brazing filler metal coatings compared to pure copper foil of the same thickness for vacuum brazing of stainless steel joints is investigated. The microstructure and microhardness of the brazed joints are characterized using X‐ray diffraction (XRD), scanning electron microscopy (SEM), and a Vickers hardness tester. The shear strength of the brazed joints is measured using an INSTRON 5869 universal testing machine. The results indicate that the electroplated Cu coating is dense, predominantly with a single cubic phase, with a few copper particles aggregating on the surface. Under electroplating conditions of 20 mA cm−2 for 1 h, the coating thickness was 56 μm. The shear strength of the brazed joint with this coating reached a maximum of 333.7 MPa, which is higher than that of a brazed joint with a 60 μm thick copper foil, which exhibits a shear strength of 303.2 MPa. The shear strength of the brazed joints shows an initial increase followed by a decrease as current density and electroplating time increase. This study provides significant technical support for brazing complex shapes or precision components. It suggests a method to simplify the brazing process, reduce production costs, and enhance the strength of brazed joints.

Exploring Antifungic Properties of Low Vacuum Dealloyed Recycled Brass Nanoporous Powder

Abstract Fungal infections pose a significant health concern globally, due to the evermore common resistance to classical antifungal therapies. One possible way to overcome this tendency is to use new pathways offered by the nanotechnology. In this respect it has been studied the possibility of utilizing recycled waste in the form of brass machining chips that are transformed into micron-porous copper (particles) by vacuum dealloying. In a subsequent step it was evidenced the potential antifungal properties. To manufacture the samples powder metallurgy was combined with vacuum dealloying, and a complex characterization to study the possible utilization of these powders at a laboratory level. The machined precursor powders were low vacuum dealloyed (P∼10-1 torr) at 500 ˚C, 550 ˚C, 600 ˚C and 650 ˚C, and the dealloying time was set between 1-4 hours. The porous particles were characterized by SEM-EDS analysis. The antifungal property was evaluated by exposing the samples on a medium of Potato Dextrose Agar (PDA) previously contaminated with a solution of Aspergillus Niger spores. The growth of fungi was analysed daily up to seven days using optical microscopy.

Full QCD with milder topological freezing

We simulate Nf = 2 + 1 QCD at the physical point combining open and periodic boundary conditions in a parallel tempering framework, following the original proposal by M. Hasenbusch for 2d CPN−1 models, which has been recently implemented and widely employed in 4d SU(N) pure Yang-Mills theories too. We show that using this algorithm it is possible to achieve a sizable reduction of the auto-correlation time of the topological charge in dynamical fermions simulations both at zero and finite temperature, allowing to avoid topology freezing down to lattice spacings as fine as a ∼ 0.02 fm. Therefore, this implementation of the Parallel Tempering on Boundary Conditions algorithm has the potential to substantially push forward the investigation of the QCD vacuum properties by means of lattice simulations.

Thermodynamics and Decay of de Sitter Vacuum

We discuss the consequences of the unique symmetry of de Sitter spacetime. This symmetry leads to the specific thermodynamic properties of the de Sitter vacuum, which produces a thermal bath for matter. de Sitter spacetime is invariant under the modified translations, r→r−eHta, where H is the Hubble parameter. For H→0, this symmetry corresponds to the conventional invariance of Minkowski spacetime under translations r→r−a. Due to this symmetry, all the comoving observers at any point of the de Sitter space perceive the de Sitter environment as the thermal bath with temperature T=H/π, which is twice as large as the Gibbons–Hawking temperature of the cosmological horizon. This temperature does not violate de Sitter symmetry and, thus, does not require the preferred reference frame, as distinct from the thermal state of matter, which violates de Sitter symmetry. This leads to the heat exchange between gravity and matter and to the instability of the de Sitter state towards the creation of matter, its further heating, and finally the decay of the de Sitter state. The temperature T=H/π determines different processes in the de Sitter environment that are not possible in the Minkowski vacuum, such as the process of ionization of an atom in the de Sitter environment. This temperature also determines the local entropy of the de Sitter vacuum state, and this allows us to calculate the total entropy of the volume inside the cosmological horizon. The result reproduces the Gibbons–Hawking area law, which is attributed to the cosmological horizon, Shor=4πKA, where K=1/(16πG). This supports the holographic properties of the cosmological event horizon. We extend the consideration of the local thermodynamics of the de Sitter state using the f(R) gravity. In this thermodynamics, the Ricci scalar curvature R and the effective gravitational coupling K are thermodynamically conjugate variables. The holographic connection between the bulk entropy of the Hubble volume and the surface entropy of the cosmological horizon remains the same but with the gravitational coupling K=df/dR. Such a connection takes place only in the 3+1 spacetime, where there is a special symmetry due to which the variables K and R have the same dimensionality. We also consider the lessons from de Sitter symmetry for the thermodynamics of black and white holes.

Kaon structure in the nuclear medium within the light front approach

We study the properties of the charged kaon in symmetric nuclear matter using a Bethe-Salpeter amplitude to model the quark-antiquark bound state, which is well constrained by previous studies of its vacuum properties. The electromagnetic form factor, charge radius, decay constant, and the light-front valence component probability are investigated in symmetric nuclear matter. In order to describe the constituent up and antistrange quarks in nuclear matter, we adopt the “quark-meson coupling (QMC) model,” which has been widely applied to various hadronic and nuclear phenomena in the nuclear medium. Published by the American Physical Society 2024

Quark Clusters, QCD Vacuum and the Cosmological 7Li, Dark Matter and Dark Energy Problems

We propose a non-exotic electromagnetic solution (within the standard model of particle physics) to the cosmological 7Li problem based upon a narrow 2 MeV photo-emission line from the decay of light glueballs (LGBs). These LGBs form within color superconducting quark clusters (SQCs), which are tens of Fermi in size, in the radiation-dominated post-BBN epoch. The mono-chromatic line from the LGB→γ+γ decay reduces Big Bang nucleosynthesis (BBN) 7Be by 2/3 without affecting other abundances or the cosmic microwave background (CMB) physics, provided the combined mass of the SQCs is greater than the total baryonic mass in the universe. Following the LGB emission, the in-SQC Quantum ChromoDynamics (QCD) vacuum becomes unstable and “leaks” (via quantum tunneling) into the external space-time (trivial) vacuum, inducing a decoupling of SQCs from hadrons. In seeking a solution to the 7Li problem, we uncovered a solution that also addresses the Dark Energy (DE) and dark matter (DM) problem, making these critical problems intertwined in our model. Being colorless, charge-neutral, optically thin, and transparent to hadrons, SQCs interact only gravitationally, making them a viable cold DM (CDM) candidate. The leakage (i.e., quantum tunneling) of the in-SQC QCD vacuum to the trivial vacuum offers an explanation of DE in our model and allows for a cosmology that evolves into a ΛCDM universe at a low redshift with a possible resolution of the Hubble tension. Our model distinguishes itself by proposing that the QCD vacuum within SQCs possesses the ability to tunnel into the exterior trivial vacuum, resulting in the generation of DE. This implies the possibility that DM and hadrons might represent distinct phases of quark matter within the framework of QCD, characterized by different vacuum properties. We discuss SQC formation in heavy-ion collision experiments at moderate temperatures and the possibility of detection of MeV photons from the LGB→γ+γ decay.

Exploring the quantum vacuum via ultraintense laser-induced refraction of light

The rapid progress of ultraintense laser technology provides a novel route to explore the quantum vacuum effect in the laboratory. Here, we propose using oblique collisions between an ultraintense pump laser and an x-ray probe laser to experimentally identify the quantum vacuum effect, where the change of the refraction properties including the refraction angle of the probe laser is taken as a detectable signature. The theoretical basis of the proposed scheme are analyzed in details, where a reasonable estimation of the scheme is given. To verify the proposed scheme, a series of two-dimensional particle-in-cell (PIC) simulations, with the vacuum polarization effect self-consistently taken into account, are carried out.

Effect of annealing temperature on the structural and optical properties of vacuum evaporated Cu13Se52Bi35 thin films

Thermal evaporation technique was used to prepare Cu13Se52Bi35 thin films. The asdeposited and annealed samples were investigated by using the X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical transmission and reflection. The XRD showed that the as-deposited film is crystalline in nature, and the crystalline size of samples increased with increasing the annealing temperature. SEM images showed that the morphology of the sample changes with the annealing temperature. The direct transition of the optical band gap (Eg) of Cu13Se52Bi35 films was observed and the values of Eg decreased with increasing the annealing temperature. Other optical parameters were also investigated.

Design and experimental research of UHV flanges for the Hefei Advanced Light Facility

The Hefei Advanced Light Facility (HALF) is a diffrac-tion-limited storage ring (DLSR) light source based on the compact multi-bend achromat (MBA) lattice. There-fore, the gaps between those focusing magnets are small. The commonly used ConFlat® flange, with a large axis dimension, is not suitable for the compact lattice in HALF. In this work, a stainless steel tapered flange fas-tened by a chain clamp has been designed for its smaller axis dimension. Two types of sealing structures are used, which are knife-edge and spring-energized metal C-ring structures, respectively. The copper gaskets with and without silver coating are used for knife-edge flange, respectively. Besides, the spring-energized metal C-ring is manufactured by SUS 304 with a tin layer of 50 μm. These flanges and chain clamps were made of SUS 304, and their vacuum properties were tested. The results indi-cate that these UHV flanges can meet the demands for the vacuum system of HALF.

Study on the vacuum properties of laser-etched oxygen-free copper

The performance of operating particle accelerators has been seriously affected by the electron cloud (e-cloud) effect. The secondary electron emission (SEE) and the e-cloud can be effectively suppressed through laser-etching the inner surface of the vacuum chamber. Oxygen-free copper (OFC) has become the first choice for the vacuum chambers of modern accelerators due to its high electric and thermal conductivity and effective radiation shielding property. It is necessary to study the vacuum properties of the laser-etched OFC for the application in the particle accelerators. In this paper, the photon stimulated desorption (PSD) yield and the outgassing rate of the laser-etched OFC were measured. The results show that the laser-etched OFC presents lower PSD yield compared to the untreated OFC, while the outgassing rates of the laser-etched and unetched samples are similar.

Role of vacuum annealing on the structural, optical properties and Dc conductivity of titanium (IV) phthalocyanine dichloride thin films

The present work elucidates the significant alterations in several physical characteristics of thermally evaporated TiPcCl2 thin films resulting from vacuum annealing at 373 and 473 K. The structure, surface morphologies, and molecular structure of TiPcCl2 thin films were studied using x-ray Diffraction (XRD), Transmission Electron Microscope (TEM), Field-Emission Scanning Electron Microscope (FESEM), and Fourier Transform Infrared (FT-IR). Results confirmed nanostructure attributes of as-deposited and annealed films, as well as the phase transition in TiPcCl2 was observed during annealing. The optical constants of as-deposited and annealed films in the wavelength range of 200–2500 nm were determined using spectrophotometric techniques. The indirect optical energy gap was observed to diminish with increasing annealing temperature due to enhanced crystallinity of thin films. Using the single oscillator model, the dispersion of the refractive index at normal dispersion was investigated. The third-order nonlinear susceptibility, χ(3), the nonlinear refractive index n2 and the nonlinear absorption coefficient, βc, were calculated and then discussed for both the as-deposited and annealed films. The electrical conductivity of TiPcCl2 exhibited increased as the temperature increased, suggesting its characteristic as a conventional organic semiconductor. The parameters of Mott’s model were obtained and discussed under low-temperature conditions afterward. Conclusions derived from this research indicate that the unique properties of vacuum annealing TiPcCl2 have great promise for future use in optoelectronic systems.

An observer's perspective of the Unruh and Hawking effects—Using coherent signals to extract information from a black hole

The Unruh effect is one of the first calculations that explain what one would see when transiting between an inertial reference frame in its quantum field vacuum state and a non-inertial (specifically, uniformly accelerating) reference frame. The inertial reference frame's vacuum state would not correspond to the vacuum state of the non-inertial frame. The observer in the non-inertial frame would see radiation, with a corresponding Bose distribution and a temperature proportional to the acceleration. In this paper, I compute the response of this non-inertial observer to a single frequency mode in the inertial frame and deduce that, indeed, the cumulative distribution (over the observer's proper time) of frequencies observed by the accelerating observer would be the Bose distribution with a temperature proportional to the acceleration. The conclusion is that the Unruh effect (and the related Hawking effect) is generic, in that it would appear with any incoming incoherent state and the Bose distribution is obtained as a consequence of the non-inertial frame's motion, rather than some special property of the quantum vacuum. As a consequence of the analysis of a coherent set of signals, I show how to extract information from the spectrum that an accelerated observer would see (as well as from the radiation from a black hole).

Projectile Motion in Special Theory of Relativity: Re-Investigation and New Dynamical Properties in Vacuum

The projectile motion (PP) in a vacuum is re-examined in this paper, taking into account the relativistic mass in special relativity (SR). In the literature, the mass of the projectile was considered as a constant during motion. However, the mass of a projectile varies with velocity according to Einstein’s famous equation m=m01−v2/c2, where m0 is the rest mass of the projectile and c is the speed of light. The governing system consists of two-coupled nonlinear ordinary differential equations (NODEs) with prescribed initial conditions. An analytical approach is suggested to treat the current model. Explicit formulas are determined for the main characteristics of the relativistic projectile (RP) such as time of flight, time of maximum height, range, maximum height, and the trajectory. The relativistic results reduce to the corresponding ones of the non-relativistic projectile (NRP) in Newtonian mechanics, when the initial velocity is not comparable to c. It is revealed that the mass of the RP varies during the motion and an analytic formula for the instantaneous mass in terms of time is derived. Also, it is declared that the angle of maximum range of the RP depends on the launching velocity, i.e., unlike the NRP in which the angle of maximum range is always π/4. In addition, this angle lies in a certain interval [π/4,π/6) for any given initial velocity (<c). The obtained results are discussed and interpreted. Comparisons with a similar problem in the literature are performed and the differences in results are explained.

Collisional Broadening within a Hadronic Transport Approach

We explore the emergence of the collisional broadening of hadrons under the influence of different media using the hadronic transport approach SMASH (Simulating Many Accelerated Strongly interacting Hadrons), which employs vacuum properties and contains no a priori information about in-medium effects. In this context, we define collisional broadening as a decrease in the lifetime of hadrons, and it arises from an interplay between the cross-sections for inelastic processes and the available phase space. We quantify this effect for various hadron species, in both a thermal gas in equilibrium and in nuclear collisions. Furthermore, we distinguish the individual contribution of each process and verify the medium response to different vacuum assumptions; we see that the decay width that depends on the resonance mass leads to a larger broadening than a mass-independent scenario.

Effect of initial grain size on the microstructure and mechanical properties of vacuum solution treated Ti–6Al–4V alloy

Ti–6Al–4V alloy warm rolled sheets with different initial grain sizes were obtained by warm rolling with different reduction rates. In order to improve its strength-ductility matching, it was treated by vacuum solution treatment (ST). By means of OM, SEM, EBSD, TEM, EPMA and XRD, the effects of different initial grain sizes of warm rolled sheet on the microstructure and mechanical properties of vacuum ST. The findings indicate that the initial grain sizes significantly influence the grain size, morphological distribution, and mechanical properties following vacuum ST. By warm rolling 60% combined with subsequent solution treatment (ST-60%), the grain size of the primary α phase (αp) and the β transformed (βt) structure is minimized, predominantly fine and equiaxed, with a dense distribution. This results in an optimal strength-ductility balance, with ultimate tensile strength, yield strength, and total elongation measuring 1283 MPa, 1194 MPa, and 10.5%, respectively. The volume fraction, grain size, morphological distribution, and the acicular alpha phase (αs) of αp and βt structure are among the factors influencing their mechanical properties. Furthermore, the solution strengthening of Aluminum (Al) in αp during the ST significantly increases the nano-hardness of αs compared to βt structure. This disparity leads to a plastic strain distribution between αp and βt structure, activating a substantial amount of Geometrically Necessary Dislocations (GND) near the βt/αp interface. This provides additional Hetero-Deformation-Induced (HDI) strengthening, thereby maintaining high strength and good ductility.

Remarks on propagating waves in non-linear vacuum electrodynamics

Using the quadratic expansion in the photon fields of Euler–Heisenberg (EH) non-linear electrodynamics (NLED) Lagrangian model we study relevant vacuum properties in a scenario involving the propagation of a photon probe in the presence of a background constant and static magnetic field, mathbf{B_e}. We compute the gauge invariant, symmetric and conserved energy–momentum tensor (EMT) and angular momentum tensor (AMT) for arbitrary magnetic field strength using the Hilbert method under the soft-photon approximation. We discuss how the presence of magneto-electric terms in the EH Lagrangian is a source of anisotropy, induce the non-zero trace in the EMT and leads to differences between EMT calculated by the Hilbert or Noether method. From the Hilbert EMT we analyze some quantities of interest such as the energy density, pressures, Poynting vector, and angular momentum vector, comparing and discussing the differences with respect to the improved Noether method. The magnetized vacuum properties are also studied showing that a photon effective magnetic moment can be defined for different polarization modes. The calculations are done in terms of derivatives of the two scalar invariants of electrodynamics, hence, extension to other NLED Lagrangian is straightforward. We discuss further physical implications and experimental strategies to test magnetization, photon pressure, and effective magnetic moment.

Vacuum polarization induced by a cosmic string and a brane in AdS spacetime

In this paper we investigate the vacuum polarization effects associated to a charged quantum massive scalar field on a (D+1)-dimensional anti-de Sitter background induced by a magnetic-flux-carrying cosmic string in the braneworld model context. We consider the brane parallel to the anti-de Sitter boundary and the cosmic string orthogonal to them. Moreover, we assume that the field obeys the Robin boundary condition on the brane. Because the brane divides the space into two regions with different properties of the quantum vacuum, we calculate the vacuum expectation value (VEV) of the field squared and the energy–momentum tensor (EMT) in each region. To develop these analyses, we have constructed the positive frequency Wightman function for both regions. The latter is decomposed in a part associated with the anti-de Sitter bulk in the presence of a cosmic string only, and the other part induced by the brane. The vacuum polarization effects associated with the higher-dimensional anti-de Sitter bulk in the presence of cosmic string have been developed in the literature, and here we are mainly interested in the effects induced by the brane. We show that the VEVs of the field squared and the components of the EMT induced by the cosmic string are finite on the brane. Explicitly, we compare these observables with the corresponding ones induced by the brane only, and show that near the brane the contribution induced by the latter is larger than the one induced by the string; however, for points distant from the brane the situation is reversed. Moreover, some asymptotic expressions for the VEV of the field squared and EMT are provided for specific limiting cases of the physical parameters of the model. Also, an application of our results is given for a cosmic string in the Z_2-symmetric Randall–Sundrum braneworld model with a single brane.

Effect of Brazing Fillet on the Microstructure and Mechanical Properties of Vacuum Brazing Stainless Steel Joints

The enhancement mechanism of the fillet on brazing joints is of great significance for vacuum brazing technology. Although a lot of research on the enhancement mechanism of the fillet has been carried out, some key components of a comprehensive systematic enhancement mechanism for brazing fillets have yet to be established. In this paper, the enhancement mechanism for brazing fillets of SS304/pure copper brazing joints was studied by both experimental and numerical simulations. The SEM and tensile experiments were used to characterize the microstructure and shear strength of the brazing joints. The results show that the brazing joints, using 60 µm thick pure copper filler metal, exhibit a good microstructure in the brazing seam; however, its mechanical properties are lower than those found in specimens with a thickness of 90 µm. The fracture behaviors of brazing joints were also investigated, the fracture of the brazing seam was a fracture of mode II due to shear stress, while the fracture of the brazing fillet was caused by a combination of tensile stress and shear stress (mode I and mode II).

The Machine Learning Methods in Non-Destructive Testing of Dynamic Properties of Vacuum Insulated Glazing Type Composite Panels.

The VIG (Vacuum Insulated Glazing) unit, composite glazing in which the space between glass panes is filled with vacuum, is one of the most advanced technologies. The key elements of the construction of VIG plates are the support pillars. Therefore, an important issue is the analysis of their mechanical properties, such as Young's modulus and their variability over a long period of time. Machine learning (ML) methods are undergoing tremendous development these days. Among the many different techniques included in AI, neural networks (NN) and extreme gradient boosting (XGB) algorithms deserve special attention. In this study, to train selected methods of machine learning, numerical data developed in the VIG plate modelling process using Abaqus program were used. The test method proposed in this article is based on the VIG plate subjected to forced vibrations of specific frequencies and then the reading of the dynamic response of the composite plate. Such collected and pre-developed experimental data were used to obtain the mechanical parameters of the steel elements located inside the analysed vacuum glazing. In the future, the proposed research methods can be used to analyse the mechanical properties of other types of composite panels.