Vacuum Part Research Articles

DNA irradiating system with 35-keV electron beam

This work aims to design the experimental system for investigating the effect of low energy electron irradiation on DNA by means of particle tracking and mechanical strength simulations. The electron beam produced with a DC accelerator having uniform kinetic energy of 35keV and the current of 10nA is used as a source of primary electrons. Two situations of DNA irradiation, in vacuo and in ambient, are studied. For both cases, the main objective is to choose appropriate materials to serve as the windows for the in vacuo sample cell and the vacuum window for ambient electron beam extraction. Silicon nitride with varied thickness has been proposed to be used as the electron exposing window for the sample cell and has been examined in Geant4 particle tracking simulation and SolidWorks mechanical strength test while titanium (Ti), beryllium (Be), and high-density polyethylene (HDPE) are considered to be used as the vacuum window and the properties are studied with the same method. The optimal materials are used to construct the system where electron beam is irradiated on a DNA sample. The interaction of electrons with the DNA and its damages is performed with the Geant4-DNA simulation. Based on our limiting conditions, it is found that the DNA double strand breaks can only be observed when the DNA sample is irradiated inside the vacuum part of the accelerator unit.

Wireless, Material-Integrated Sensors for Strain and Temperature Measurement in Glass Fibre Reinforced Composites.

Fiber reinforced plastics (FRP) offer huge potentials for energy efficient applications. Special care must be taken during both FRP fabrication and usage to ensure intended material properties and behavior. This paper presents a novel approach for the monitoring of the strain and temperature of glass fibre reinforced polymer (GFRP) materials in the context of both production process monitoring and structural health monitoring (SHM) applications. The sensor is designed to be integrated into GFRPs during the production process, and the sensor concept includes possibilities of automated placement during textile layup. To minimize sensor impact on GFRP integrity and to simplify vacuum setup and part handling, the sensor operates without the need for either wires or a battery. In the first sections of this work, sensor concept, design and prototype fabrication are presented. Subsequently, it is shown how the sensors can be used for flow front monitoring and cure estimation during GFRP production by measuring local resin temperature. The resulting specimens are then characterized regarding strain measurement capabilities, mechanical influence on the host component and overall system limitations. Average strain sensor accuracy is found to be ≤0.06 mm/m, while a maximum operation temperature of 126.9 °C and a maximum reading distance of 38 mm are measured. Based on a limited number of bending tests, no negative influence of sensor presence on breaking strength could be found. Possible applications include structural components, e.g., wind turbine blades or boat hulls.

Study of Quarkonium in QGP from Unquenched Lattice QCD

This paper discusses the charmonium and bottomonium correlators in the pseudoscalar channel and the corresponding spectral reconstruction on the lattice. The absence of a transport peak in the pseudoscalar channel spectral function allows for an easier study of the in-medium modification of bound states. However, extracting spectral information from Euclidean correlators is still a numerically ill-posed problem. To constrain the spectral reconstruction, we use an ansatz motivated from perturbation theory. The perturbative model spectral function has two main contributions: a thermal part around the threshold obtained from pNRQCD and the vacuum part well above the threshold. These two regions are matched continuously, and the model spectral function is obtained by introducing parameters that control the overall thermal shift of the peak and the overall amplitude. The lattice correlator data is computed using clover-improved Wilson valence fermions on large and fine gauge field configurations generated using N_f=2+1 flavors Highly Improved Staggered Quark action with physical strange quark mass m_s, and slightly heavy degenerate up and down quark masses m_l=m_s/5 that correspond to m_pi simeq 320 MeV. Our results obtained at T=220 MeV and T=251 MeV suggest that no resonance peaks are needed to describe the charmonium lattice data at these temperatures, while for bottomonium thermally broadened resonance peaks persists.

Fabrication and characterization of iodine photonic microcells for sub-Doppler spectroscopy applications.

We report on the development of all-fiber stand-alone iodine-filled photonic microcells demonstrating record absorption contrast at room temperature. The microcell's fiber is made of inhibited coupling guiding hollow-core photonic crystal fibers. The fiber-core loading with iodine was undertaken at 10-1-10-2mbar vapor pressure using what, to the best of our knowledge, is a novel gas-manifold based on metallic vacuum parts with ceramic coated inner surfaces for corrosion resistance. The fiber is then sealed on the tips and mounted on FC/APC connectors for better integration with standard fiber components. The stand-alone microcells display Doppler lines with contrasts up to 73% in the 633 nm wavelength range, and an off-resonance insertion loss between 3 to 4 dB. Sub-Doppler spectroscopy based on saturable absorption has been carried out to resolve the hyperfine structure of the P(33)6-3 lines at room temperature with a full-width at half maximum of 24 MHz on the b4 component with the help of lock-in amplification. Also, we demonstrate distinguishable hyperfine components on the R(39)6-3 line at room temperature without any recourse to signal-to-noise ratio amplification techniques.

A Cosmological Neuroscientific Definition of God

The main objective of this work was to produce a scientifically reasonable definition of God. The rationale was to generate a definition for filling a small part of the spiritual vacuum of the 21st century and thus initiate a new understanding of the Intelligence that permeates the cosmos with mystery, love, order, direction and morals. This resulted in the following definition: “God may be a-humanly incomprehensible-eternal cosmic existence, intimately related to the endlessness of space, to the nature of the deepest common substance of matter and energy, to this common substance’s unceasing motion responsible for time, and to the basic laws of their allness, letting love transform this allness to an ordered Multiverse with a Soul: the—scientifically approachable—Soul of Multiverse inspired to guard these laws and equip their order with direction and morals while imbuing the cosmos with the potential of lives evolving, at the right spatial and temporal distances, to embrace the sense of the divine, thus justifying the existence of God.” The likely neural circuitry for sensing God in the human brain was identified as a network for spiritual data flow across the conscious and subconscious layers of the association cortical cognitive system exchanging data with the prefrontal cortical Self-Ken and modulated by inputs from the emotional and motivational systems of the brain. To study this mental process, the design of a God-Experience Monitor was also developed: a comfortably wearable combination of EEG and audiovisual-recorders tailored to at least partially capture the individual experiences of God anytime and at the very “genius loci” of such experiences.

Efficient twin-field quantum key distribution with heralded single-photon source

Twin-field quantum key distribution (TF-QKD) can overcome the fundamental rate-loss limit in the point-to-point QKD without a quantum repeater, so as to realize key distribution over long distance. In general, weak coherent pulse (WCP) emitted from the attenuated laser is often used as the photon source for TF-QKD and its variants, however, the key generation rate and transmission distance may be restricted for TF-QKD protocols using this type of photon source as it contains a large proportion of vacuum part. Another candidate of photon source within reach of current technology is the heralded single-photon source (HSPS). In this paper, we propose two TF-QKD variants with HSPS and provide the analytical derivation of upper bounds of yields separately with active and passive decoy-state methods. Numerical simulations show that the active decoy-state TF-QKD with HSPS (referred to as Protocol (1) achieves higher secret key rate and tolerates more large transmission loss than the original TF-QKD with WCP source. However, since the active modulation of decoy intensities may leak additional information to the eavesdropper Eve, thus we extend the result of Protocol 1 and further propose a passive decoy-state TF-QKD with HSPS (referred to as Protocol (2). The simulation results demonstrate that the performance of Protocol 2 is close to the original active TF-QKD protocol, and its security and flexibility are further improved.

Annealing-Induced Structural Behavior of Mn Dopant Ions in Calcium Orthovanadate Ca3(VO4)2 Single Crystals.

The crystal and local structures of Czochralski-grown calcium orthovanadate (Ca3(VO4)2) single crystals doped with over-stoichiometric 0.05 wt % Mn2O3 (CVO:0.05Mn) and annealed under different conditions are studied by single-crystal conventional and synchrotron X-ray diffraction, X-ray absorption spectroscopy, and electron paramagnetic resonance for the first time. Bottom (annealing in air) and top (annealing in air and in vacuum) parts of the CVO:0.05Mn crystal differ in the manganese content (higher in the bottom part), formal charge (Mn4+ and Mn(3+δ)+, respectively), and color (orange bottom part; light orange and yellow top parts annealed in air and vacuum, respectively). Manganese ions are located in one (Ca3, distorted two-capped trigonal prism) of five crystallographic Ca sites and have octahedral coordination, which is consistent with crystal-chemical properties of transition-metal ions. The presence of vacancies in one of three V sites is revealed. Formal charge 5+ for vanadium ions is confirmed by X-ray photoelectron spectroscopy. Different colors of CVO:Mn crystals and different formal charges of manganese are explained depending on the growth and post-growth treatment conditions.

Factor 30 Pulse Compression by Hybrid Multipass Multiplate Spectral Broadening

As ultrafast laser technology advances towards ever higher peak and average powers, generating sub-50 fs pulses from laser architectures that exhibit best power-scaling capabilities remains a major challenge. Here, we present a very compact and highly robust method to compress 1.24 ps pulses to 39 fs by means of only a single spectral broadening stage which neither requires vacuum parts nor custom-made optics. Our approach is based on the hybridization of the multiplate continuum and the multipass cell spectral broadening techniques. Their combination leads to significantly higher spectral broadening factors in bulk material than what has been reported from either method alone. Moreover, our approach efficiently suppresses adverse features of single-pass bulk spectral broadening. We use a burst-mode Yb:YAG laser emitting pulses with 80 MW peak power that are enhanced to more than 1 GW after postcompression. With only 0.19% rms pulse-to-pulse energy fluctuations, the technique exhibits excellent stability. Furthermore, we have measured state-of-the-art spectral-spatial homogeneity and good beam quality of M 2 = 1.2 up to a spectral broadening factor of 30. Due to the method’s simplicity, compactness, and scalability, it is highly attractive for turning a picosecond laser into an ultrafast light source that generates pulses of only a few tens of femtoseconds duration.

In vacuum dynamic and static tests of a thrust balance for electric propulsion with hysteresis analysis and behaviour prediction with transfer function

This work describes the advances on the development of a thrust-stand for electric propulsion application with a focus on the constraints of the two-stage pulsed plasma thruster (TS-PPT) being developed at INPE at the Electric Propulsion Laboratory (LPEL) of the Laboratory of Combustion and Propulsion (LABCP). While previous work on this instrument focused on basic development in atmospheric pressure the present effort presents the development undertaken to elevate the TRL of the device to allow it to operate in vacuum—the environment where actual electric thrusters operate and are tested. To cater for INPE’s TS-PPT specification, standard masses summing 1.2 kg were used while the electrostatic calibration device (ECD) was set to produce 31 μNs. A detailed hysteresis analysis was carried out at the target TS-PPT specification together with a transfer function that aimed at extrapolating and predicting the behaviour of the instrument. In addition, this work shows the development of a new magnetic damper for the instrument that reduces the waiting time between tests. A new calibration at the TS-PPT specification points were undertaken in vacuum since previous calibration were made for atmospheric pressure and did not include the specific points of interest for the TS-PPT. Furthermore, previous calibration procedures were verified to ensure they would apply to the vacuum conditions and to account for the substitution of some thrust stand previously incompatible vacuum parts and also to account for the addition of the new magnetic damper and other unforeseen conditions caused by the vacuum environment.

Magneto-vortical effect in strong magnetic field

We develop covariant chiral kinetic theory with Landau level basis. We use it to investigate a magnetized plasma with a transverse electric field and a steady vorticity as perturbations. After taking into account vacuum shift in the latter case, we find the resulting current and stress tensor in both cases can be matched consistently with constitutive equations of magnetohydrodynamics. We find the solution in the vorticity case contains both shifts in temperature and chemical potential as well as excitations of the lowest Landau level states. The solution gives rise to an vector charge density and axial current density. The vacuum parts coming from both shifts and excitations agree with previous studies and the medium parts coming entirely from excitations leads to a new contribution to vector charge and axial current density consistent with standard chiral vortical effect.

Comparative study of heat transfer enhancement using different fins in semi-circular absorber tube for large-aperture trough solar concentrator

An improved evacuated absorber tube (AT) design consisting of a semi-circular tube is proposed for large-aperture parabolic trough concentrator. The absorber tube also contains a flat-plate radiation shield in the vacuum part of the tube in the glass cover. To enhance the heat transfer in the AT, different fins geometries added to the bottom of the AT were analyzed here. Compared to an AT without fins, the thermal efficiency of the tube could be increased from 75.7% to 76.9% with a short and thick fin and to 77.3% with a long and thin fin in the flow velocity range of 0.4–1.5 m/s. The long and thin finned AT shows better enhancement of heat transfer, but the heat transfer performance factor also accounting for frictional losses is higher for short and thick fin. Simultaneously, increasing the number of long and thin fins in the AT would not improve much the heat transfer performance.

Matter, Dark Matter and Quartic Potential Generated by Unstable Confinement of Quarks

The Standard Model for particle physics is here extended by making a non-equilibrium filling of the empty vacuum after the start of Big Bang. The process is described as an unstable binding of massless quarks to massless antiquarks. When the filled part of vacuum condenses, the system becomes stabilized, quarks acquire mass and become confined and a quartic potential is induced, which hence need not be introduced ad hoc. The coupling and scale parameters in this potential have become asymmetric microscopic functions of the quark and antiquark densities. The so obtained dynamics can explain how the matter-antimatter asymmetry in the Universe and dark matter emerged. Quantum corrections are included and the model then gives ordinary matter, dark matter and dark energy contents at correct orders of magnitude.

Sample chamber for synchrotron based in-situ X-ray diffraction experiments under electric fields and temperatures between 100 K and 1250 K.

Many scientific questions require X-ray experiments conducted at varying temperatures, sometimes combined with the application of electric fields. Here, a customized sample chamber developed for beamlines P23 and P24 of PETRA III at DESY to suit these demands is presented. The chamber body consists mainly of standard vacuum parts housing the heater/cooler assembly supplying a temperature range of 100 K to 1250 K and an xyz manipulator holding an electric contact needle for electric measurements at both high voltage and low current. The chamber is closed by an exchangeable hemispherical dome offering all degrees of freedom for single-crystal experiments within one hemisphere of solid angle. The currently available dome materials (PC, PS, PEEK polymers) differ in their absorption and scattering characteristics, with PEEK providing the best overall performance. The article further describes heating and cooling capabilities, electric characteristics, and plans for future upgrades of the chamber. Examples of applications are discussed.

Electron-positron annihilation into two photons in an intense plane-wave field

The process of electron-positron annihilation into two photons in the presence of an intense classical plane wave of an arbitrary shape is investigated analytically by employing light-cone quantization and by taking into account the effects of the plane wave exactly. We introduce a general description of second-order 2-to-2 scattering processes in a plane-wave background field, indicating the necessity of considering the localization of the colliding particles and achieving that by means of wave packets. We define a local cross section in the background field, which generalizes the vacuum cross section and which, though not being directly an observable, allows for a comparison between the results in the plane wave and in vacuum without relying on the shape of the incoming wave packets. Two possible cascade or two-step channels have been identified in the annihilation process and an alternative way of representing the two-step and one-step contributions via a "virtuality" integral has been found. Finally, we compute the total local cross section to leading order in the coupling between the electron-positron field and the quantized photon field, excluding the interference between the two leading-order diagrams arising from the exchange of the two final photons, and express it in a relatively compact form. In contrast to processes in a background field initiated by a single particle, the pair annihilation into two photons, in fact, also occurs in vacuum. Our result naturally embeds the vacuum part and reduces to the vacuum expression, known in the literature, in the case of a vanishing laser field.

Worldline master formulas for the dressed electron propagator. Part I. Off-shell amplitudes

In the first-quantised worldline approach to quantum field theory, a long-standing problem has been to extend this formalism to amplitudes involving open fermion lines while maintaining the efficiency of the well-tested closed-loop case. In the present series of papers, we develop a suitable formalism for the case of quantum electrodynamics in vacuum (part one and two) and in a constant external electromagnetic field (part three), based on second-order fermions and the symbol map. We derive this formalism from standard field theory, but also give an alternative derivation intrinsic to the worldline theory. In this first part, we use it to obtain a Bern-Kosower type master formula for the fermion propagator, dressed with N photons, in terms of the “N -photon kernel,” where off-shell this kernel appears also in “subleading” terms involving only N − 1 of the N photons. Although the parameter integrals generated by the master formula are equivalent to the usual Feynman diagrams, they are quite different since the use of the inverse symbol map avoids the appearance of long products of Dirac matrices. As a test we use the N = 2 case for a recalculation of the one-loop fermion self energy, in D dimensions and arbitrary covariant gauge, reproducing the known result. We find that significant simplification can be achieved in this calculation by choosing an unusual momentum-dependent gauge parameter.

Constructing and Testing a Vacuum Frying for Salacca Fruit Using a Reused Vacuum Pump

Fruit chips are the result of the processing of horticultural produce that does not use high temperatures. The abundance of agricultural products in Indonesia and still not many agricultural product processing technology make the fruit frying business a good prospect. On the one hand, processing fruit chips with hight water content characteristics require a special frying technology called low temperature and pressure. On the other hand, this equipment is still not widely developed or even owned by small and medium enterprises. Therefore, this study aims to design and test a vacuum fryer for salacca. The vacuum method used is to use a vacuum pump recycled from the vacuum part of the cooling unit. The parameters observed were the effective capacity of the equipment, water content, and organoleptic test. The research results showed that the equipment's effective capacity was 0.26 kg/hr with 1.63% (w.b.) water content.

One-piece mushroom keratoplasty outcomes

To clinically evaluate the results of one-piece mushroom-shaped keratoplasty. A total of 10 patients (10 eyes) were enrolled, all having corneal perforations and deep stromal opacities with involvement of Descemet's membrane. For transplantation, hypothermic preserved donor corneas with mean endothelial cell density of 2896±327 cells per 1 mm2 were used. Surgical technique. Recipient tissues as well as the graft were cut with the Moria trephine. For that, the 8.5-mm blade was replaced by a 6.5-mm one and vice versa, respectively, with attention paid not to violate the vacuum while making the cuts. Transparent cornea engraftment was achieved in all patients. Best corrected visual acuity averaged 0.55±0.22. Spherical component of refraction varied from -4.25 to +2.75 diopters. Mean corneal astigmatism was 3.35±1.73 diopters. At 6 months after surgery, the mean endothelial cell density was 2355±336 cells/mm2, at 1 year - 2141±304 cells/mm2. One-piece mushroom keratoplasty is an effective surgical treatment of corneal perforations and deep stromal opacities with involvement of Descemet's membrane that ensures a high rate of transparent corneal engraftment. The use of the Moria vacuum trephine in combination with blades of different diameters and secure fixation of the vacuum part of the trephine eliminate the risk of the 'mushroom stem' decentration relative to its 'head'.

Dimensional characteristics of Ti-6Al-4V thin-walled parts prepared by wire-based multi-laser additive manufacturing in vacuum

Purpose A wire-based additive manufacturing system works with high manufacturing efficiency and low dimensional precision. The purpose of this paper is to study the dimensional characteristics of Ti-6Al-4V thin-walled parts with wire-based multi-laser additive manufacturing in vacuum. Design/methodology/approach Wire-based multi-laser additive manufacturing was carried out to understand the effect brought from different parameters. The Ti-6Al-4V thin-walled parts were formed by different height increments, power inputs and inter-layer cooling times in vacuum. Findings The result shows that, with the number of layers increment, the layer width of thin-walled part increases gradually in the beginning and stabilizes soon afterward. Height increment, laser power and inter-layer cooling time could affect the energy input to the deposited bead and heat accumulation of thin-walled part. The layer width decreases, while the height increment increases. The increment of laser power could increase the layer width. And, the increment of inter-layer cooling time (more than 5 s) has little effect on the layer width. Originality/value The heat dissipation mode of thin-walled parts in vacuum and the influence of different parameters on layer width are explained in this paper. It provides a reference for further understanding and controlling dimension precision of Ti-6Al-4V thin-walled part with wire-based multi-laser additive manufacturing in vacuum. At the same time, it provides a reference for researches of dimensional characteristics in the additive manufacturing industry.

General structure of the neutral ρ meson self-energy and its spectral properties in a hot and dense magnetized medium

The one loop self energy of the neutral $\rho$ meson is obtained for the effective $\rho\pi\pi$ and $\rho NN$ interaction at finite temperature and density in the presence of a constant background magnetic field of arbitrary strength. In our approach, the eB-dependent vacuum part of the self energy is extracted by means of dimensional regularization where the ultraviolet divergences corresponding to the pure vacuum self energy manifest as the pole singularities of gamma as well as Hurwitz zeta functions. This improved regularization procedure consistently reproduces the expected results in the vanishing magnetic field limit and can be used quite generally in other self energy calculations dealing with arbitrary magnetic field strength. In presence of the external magnetic field, the general Lorentz structure for the in-medium vector boson self energy is derived which can also be implemented in case of the gauge bosons such as photons and gluons. It has been shown that with vanishing perpendicular momentum of the external particle, essentially two form factors are sufficient to describe the self energy completely. Consequently, two distinct modes are observed in the study of the effective mass, dispersion relations and the spectral function of $\rho^0$ where one of the modes possesses two fold degeneracy. For large baryonic chemical potential, it is observed that the critical magnetic field required to block the $\rho^0\rightarrow\pi^+\pi^-$ decay channel increases significantly with temperature. However, in case of smaller values reaching down to vanishing chemical potential, the critical field follows the opposite trend.

Development of Removable Hollow Cathode Discharge Apparatus for Sputtering Solid Metals

A hollow cathode discharge cell has been developed for a variety of sample phases. To make the experimental apparatus compact, we have adopted DC discharge, and the discharge cell was inexpensively constructed for replacement with commercially available vacuum parts. The most distinctive attribute of the developed cell is the double structure of the cathodes. The occurrence of sputtering resulted in the metal atom in gas phase. With Ar buffer gas, the favorable condition of laser absorption spectroscopy for the gas phase sample was investigated.