Pressure In Vacuum Chamber Research Articles

Experimental evaluation of the influence of the diffuser inlet to nozzle exit cross sectional area ratio on pressure oscillation in a high-altitude test facility

The ratio of diffuser inlet to nozzle exit area (Ad/Ae) is one of the most important parameters in designing and evaluating the performance of a high-altitude test facility (HATF). Typically, at motor pressures near start or operating pressure of the diffuser, the vacuum chamber pressure oscillates at a high Ad/Ae, which may be dangerous for the HATF. In the present study, the effect of the Ad/Ae on the starting and breakdown performance of a second throat exhaust diffuser (STED) has been investigated experimentally using a HATF supplied by high-pressure cold air apparatus. Upon examining the overall performance of the diffuser, it is observed that with an increase in Ad/Ae, the oblique sealing shock wave at the diffuser inlet undergoes significant changes in location and strength. This leads to a further reduction of the flow total pressure and a stronger separation of the flow along the diffuser. Consequently, flow instability arises during starting or breakdown phases near the STED starting or operating pressure. By frequency analysis, it is observed that as Ad/Ae increases, the number of oscillatory modes of the vacuum chamber pressure increases and the dominant frequency of the oscillations in these transient situations becomes larger. Additionally, there is a significant decrease in nozzle pressure related to the onset of pressure oscillations. Furthermore, with an increase in Ad/Ae from 1.27 to 7.81, the minimum starting pressure and breakdown pressure of STED increase by 20.33% and 28.47%, respectively. Also, the hysteresis range in performance of STED vanishes at high Ad/Ae values.

Electron Beam Powder Bed Fusion of ATI C103TM Refractory Alloy

The study investigated the use of electron beam powder bed fusion (EB-PBF) to fabricate niobium ATI C103™ alloy articles for microstructural characterization and mechanical testing. The feedstock powder was consolidated into low-porosity articles, and both powder and sample chemistry were monitored. Oxygen uptake in the powder was limited to less than the ASTM B655/B655M (2018) specification limits for 7 uses. Manipulating vacuum chamber pressure showed stable hafnium content but decreasing titanium content with decreasing chamber pressure attributed to evaporation. AM samples were evaluated in the post-processed, as-fabricated, annealed, and hot isostatic pressing (HIP) condition with a maximum yield strength of 287 MPa, UTS of 375 MPa for the HIP, and maximum elongation of 32 pct for the annealed specimens, respectively. Mechanical properties are similar to typical wrought products, with a notable increase in yield strength after post-processing by HIP. The fracture behavior was driven by porosity in the as-fabricated specimens and grain boundary fracture after HIP.

Determining the effect of laboratory testing conditions on working parameters of the ST-25 hall thruster

The object of this study is the ST-25 Hall thruster with limited discharge power, no more than 200 W, designed by Flight Control LLC (Ukraine). The problem that was solved in the current paper was to determine the effect of residual gas pressure in vacuum chambers on the operating parameters of the Hall thruster. To solve this task, the operating parameters of the ST-25 thruster were determined, which was tested in three vacuum chambers with different sizes of residual pressure. As a result of the laboratory study into the operating parameters of the ST-25 thruster, the volt-ampere characteristics of the engine discharge at fixed values of the working gas (xenon) flow rate were obtained. The dependences of the engine thrust on the mass flow rate of the working gas at fixed values of the discharge voltage were derived. Based on the experimental data, the dependences of the specific impulse of the engine anode unit on the discharge voltage, as well as the dependence of efficiency of the engine anode unit on the discharge voltage were calculated. The studies showed that when the residual pressure in the vacuum chamber is reduced by 2–3 times, the operating parameters of the engine increase by 15–20 %. Such a reduction in residual pressure increases thrust by 25–40 %. Special feature of the results is the determination of threshold values of residual gas pressure in vacuum chambers during experimental studies, in which the operating parameters of the Hall thruster are similar to its operating parameters under space conditions. This work’s findings could be used in practice when conducting experimental studies of electric rocket engines, when it is necessary to estimate the operating parameters of Hall thrusters that will be obtained under actual space conditions

A Miniature Orthogonal Injection Ion Funnel (MO-IF) Providing Enhanced Performance for the Miniature Mass Spectrometer.

The sensitivity of the miniature mass spectrometer (mini-MS) is largely restricted by the ion transmission in rough vacuum region. Even though various "in-line" ion transfer devices have improved mini-MS sensitivity, the severe dynamic gas is still weakening the efficiency of ion transmission in this region. Inspired by the "off-axis" ion funnel design in the lab-scale mass spectrometers, a miniature orthogonal injection ion funnel (MO-IF) was developed in this study for the mini-MS with a continuous atmospheric pressure interface. Capable of directing injected ions by 90° and then transport them forward to the downstream skimmer, the MO-IF enabled the separation of ions from the dynamic gas flow jetted out of the inlet capillary. The key factors were optimized for the MO-IF, including the effects of RF amplitude, DC electric fields, and the position of the repeller. Under optimized conditions, the MO-IF minimized the negative effects of dynamic gas and improved the ion transmission efficiency by ∼2-fold in comparison with the in-line injection ion funnel. As a result, a lower limit of detection of 0.5 ng/mL were obtained with good linearity for hypaconitine. Additionally, the MO-IF further decreased the buffer gas pressure in the second vacuum chamber and improved the mass resolution by 1.1-1.5 times at different scan rates.

Bayesian optimization for stable properties amid processing fluctuations in sputter deposition

We introduce a Bayesian optimization approach to guide the sputter deposition of molybdenum thin films, aiming to achieve desired residual stress and sheet resistance while minimizing susceptibility to stochastic fluctuations during deposition. Thin films are pivotal in numerous technologies, including semiconductors and optical devices, where their properties are critical. Sputter deposition parameters, such as deposition power, vacuum chamber pressure, and working distance, influence physical properties like residual stress and resistance. Excessive stress and high resistance can impair device performance, necessitating the selection of optimal process parameters. Furthermore, these parameters should ensure the consistency and reliability of thin film properties, assisting in the reproducibility of the devices. However, exploring the multidimensional design space for process optimization is expensive. Bayesian optimization is ideal for optimizing inputs/parameters of general black-box functions without reliance on gradient information. We utilize Bayesian optimization to optimize deposition power and pressure using a custom-built objective function incorporating observed stress and resistance data. Additionally, we integrate prior knowledge of stress variation with pressure into the objective function to prioritize films least affected by stochastic variations. Our findings demonstrate that Bayesian optimization effectively explores the design space and identifies optimal parameter combinations meeting desired stress and resistance specifications.

Gas dynamics at starting and terminating phase of a supersonic exhaust diffuser with a conical nozzle

This research investigates the process of starting and breakdown of second throat diffuser during high-altitude test of conical nozzle with a high expansion ratio. The subscale experimental setup includes a conical nozzle with an expansion ratio of 53, plus a second throat diffuser with a contraction ratio of 1.85, using compressed air as the working fluid. Numerical simulation has been employed to identify the flow physics during the unsteady process of diffuser startup and breakdown. According to the results, the starting process is divided into three distinct stages. In the first stage, the exhausted flow from the nozzle enters the vacuum chamber, leading to an increase in vacuum chamber pressure. The second stage, corresponding to the period before full flow establishment in the conical nozzle, exhibits a relatively constant slope. In the final stage, associated with the transition from over-expanded to under-expanded states, the slope of the rate of evacuation development descends. Next, the vacuum degradation in termination process has been analyzed, and it has been found to include three stages: high slope, middle slope, and low slope. The flow physics during the start process, similar to the results observed in other conical nozzles, exhibits only a Mach reflection structure. However, during the termination process, the flow physics involve a combination of both structures, including Mach reflection and Cap Shock. The results indicate that during the start, an internal shock only interacts with the separation shock, and no special change occurs in the Mach reflection structure. In contrast, during the termination process, unlike what has been reported in previous studies on conical nozzles, the structure of cap shock waves and restricted shock separation patterns are also observed. Another distinction between the starting and termination processes is related to the pressure distribution in the diffuser wall. The wall pressure at the diffuser inlet during the termination process has been reported to be 90% higher than during the starting process.

ONE-DIMENSIONAL TRANSIENT MODEL OF FOOD PRODUCT TEMPERATURE AND WEIGHT LOSS EVOLUTION IN A VACUUM COOLER WITH MEMBRANE HUMIDIFICATION

A one-dimensional, transient model was developed to predict the temperature and weight loss evolution of a food product cooled using a vacuum cooling system with membrane humidification. The model included the following: (1) a sub-model based on the mass conservation of air and vapor inside the vacuum chamber; (2) a sub-model based on the coupled mass and heat transfer with inner vapor and heat generation; and (3) a sub-model based on the mass conservation of water vapor along the flow channels inside the humidifier. The vacuum chamber pressure was reduced from 1 atm to 2200 Pa using a vacuum pump with deflating speed of 500 m3/hr and condenser and membrane humidifier operating temperatures of 13°C and 60°C, respectively. A meat joint with a weight of 5.30 kg was cooled from an initial core temperature of 74°C to below 10°C. The conventional and modified models both cooled the food product to 10°C in 25 minutes. It was found out that increasing the chamber relative humidity reduced the surface water evaporation while the internal evaporation rate remained the same. Thus, the meat's moisture content, which was initially at 73.51%, was reduced to only 65.44%-an improvement from the conventional vacuum cooling system's 64.31%. This translated to product weight loss of only 10.98%, which represented significant progress compared to the conventional system's 12.51%. The simulation results indicated that employing humidification in a vacuum cooling system reduces the product total moisture loss while maintaining the rapid cooling rate.

Ground testing of Al-polyurethane shape memory polymer sail material under pulsed light exposure

This article presents a study on design and testing of space sails using Al-polyurethane Shape memory polymer. The properties of the polymer are simulated and tested in the design phase, and the results are compared with the fabricated sail, which is considered nominal. The efficiency of the polyurethane sail is found to be approximately 86.5%. The controllability of the sail is enhanced using a heating system that uses light rays to heat the polymer at specific control spots. The relative deflection at these spots causes a deviation in solar momentum, resulting in a controlled displacement of the sail. This control system is found to be 42% more efficient than conventional vane-type deflection systems. The paper also presents the fabrication of a ground testing apparatus designed to test the sail specimen in laboratory conditions. The apparatus is capable of producing a vacuum chamber pressure up to −400 mm/Hg and includes a magnetic levitation platform with strong permanent magnets to neglect local gravitational effects. The platform provides support for fixing the solar sail frame made from carbon fiber composite material. The testing apparatus consists of a 1000-W halogen light source with intensity ranges of approximately 200,000 lux. Sail material with a reflective surface is exposed to controlled luminance under vacuum conditions to measure the deflection of the sail. Deflection values are recorded by means of a resistance type strain gauge and strain indicator arrangement. Plotting deflections with time period gives the acceleration of the sail inside the test apparatus. A coolant chamber with a ceramic base is also provided to reduce temperature effects inside the vacuum chamber. In conclusion, this study presents a promising approach for the design and testing of solar sails using shape memory polymer and a ground testing apparatus. The results of this research can contribute to the development of more efficient and versatile solar sail technology for fuel-free aerospace propulsion.

Preparing CuO, Cu2O thin films at various argon gas by using reactive dc magnetron sputtering method

Copper oxide (Cu2O, CuO) has been formed by dc reactive magnetron sputtering method of glass substrates, whereas pure target of the solid copper was sputtered with a mixture of plasma for argon gas and oxygen gas which are used form these films. Under vacuum chamber pressure on 1.2×10-5 Pa, Ar was varying from 5 to 15 sccm while other deposition parameters were fixed. X-ray photoelectron spectroscopy, XRD diffractions system, Atomic Force Microscopy (AFM), hall effect measurement system, and UV–VIS spectrophotometer were used to calculate the characteristic of the deposited thin films. Thin film at 5 sccm has investigated n-type of CuO thin film with direct band gap of 1.8eV and p-type of Cu2O at 15 sccm with direct band gap of 2.7eV. The influence of changing the Ar on the electrical and the optical properties was investigated in this study, furthermore in this study approved that the reactive dc magnetron sputtering method is suitable to prepare two type of semiconductors by change only one condition.

Starting transient analysis of second throat exhaust diffuser in high-altitude test of a thrust optimized parabolic nozzle

This study presents a combined numerical and experimental investigation of the starting process of a second throat diffuser during ground testing of a thrust-optimized parabolic (TOP). In this investigation, compressed air has been utilized as the operating fluid in a subscale experimental setup. The study examines three scenarios with varying nozzle pressure profile, including two cases of start and one case of un-start. Additionally, this study employs numerical simulations to identify and analyze the physical phenomena that occur at each stage of the start and un-start processes in these cases. The results for the case started at a relatively low nozzle pressure profile (24.5 bar max) indicate that the vacuum generation process during high-altitude testing of TOP nozzles can be broken down into five stages. The first stage involves an increase in pressure within the vacuum chamber during the early moments of the starting process. In the second stage, vacuum generation occurs gradually as the nozzle operates under free shock separation (FSS). This is followed with the reappearance of small fluctuations in the vacuum chamber pressure due to transition from the FSS to restricted shock separation (RSS) flow pattern (third stage). The fourth stage begins with the predominance of the shock separation and recirculation (SSR) flow pattern inside the nozzle, resulting in gradual vacuum generation. This stage terminates upon transformation of the cap shock structure into a regular reflection structure. In the final stage of vacuum generation, the evacuation rate is almost half of the fourth stage. This is attributed to the establishment of expanded and under-expanded conditions, as well as the impingement of the nozzle outflow jet with the wall and the onset of start conditions. Next, the results of vacuum generation have been studied at higher nozzle pressures profile (34 bar max). The results indicate that increasing the nozzle pressure rate not only reduced the starting time by 23%, but also significantly reduced the pressure fluctuations in the evacuation process. In fact, at higher nozzle pressure, the third stage is almost eliminated. In the un-started case, where the nozzle pressure is lower than the minimum starting pressure, fluctuations occur in the vacuum chamber pressure due to the dynamics of the diffuser inlet recirculation bubble and the transition of the nozzle separation pattern from RSS to SSR and vice versa.

Rapid and Efficient Optimization Method for a Genetic Transformation System of Medicinal Plants Erigeron breviscapus.

Erigeron breviscapus is an important medicinal plant with high medicinal and economic value. It is currently the best natural biological drug for the treatment of obliterative cerebrovascular disease and the sequela of cerebral hemorrhage. Therefore, to solve the contradiction between supply and demand, the study of genetic transformation of E. breviscapus is essential for targeted breeding. However, establishing an efficient genetic transformation system is a lengthy process. In this study, we established a rapid and efficient optimized protocol for genetic transformation of E. breviscapus using the hybrid orthogonal method. The effect of different concentrations of selection pressure (Hygromycin B) on callus induction and the optimal pre-culture time of 7 days were demonstrated. The optimal transformation conditions were as follows: precipitant agents MgCl2 + PEG, target tissue distance 9 cm, helium pressure 650 psi, bombardment once, plasmid DNA concentration 1.0 μg·μL-1, and chamber vacuum pressure 27 mmHg. Integration of the desired genes was verified by amplifying 1.02 kb of htp gene from the T0 transgenic line. Genetic transformation of E. breviscapus was carried out by particle bombardment under the optimized conditions, and a stable transformation efficiency of 36.7% was achieved. This method will also contribute to improving the genetic transformation rate of other medicinal plants.

Research on a MEMS Microparticles Vacuum Chamber for Optical Levitation with a Built-In Vacuum Gauge

The vacuum chamber is an important part of microparticle optical levitation technology. The traditional vacuum chamber has a large volume and many peripheral components, which cannot meet the requirements of miniaturization and on-chip optical levitation technology. Therefore, this study proposes a novel microparticle vacuum chamber based on the micro-electro-mechanical system (MEMS) process. This MEMS microparticle vacuum chamber adopts a “glass-silicon-glass” three-layer vacuum bonding process, with a volume of only 15 mm × 12 mm × 1.2 mm, including particle chamber, cantilever resonator chamber, and getter chamber, which can encapsulate microparticles in a tiny vacuum environment and realize optical levitation of microparticles. At the same time, the air pressure in the micro vacuum chamber is monitored by the cantilever resonator, which can provide a miniaturized microparticle chamber with a more accurate vacuum environment for microparticle optical levitation. The research of this paper has significance for promoting the development of miniaturized optical levitation technology.

Surface Morphology and Optical and Electrophysical Properties of La0.4Ba0.6CoO3 Films Obtained by Laser Deposition

Nanostructured thin films on a silicon substrate were obtained by high-frequency repetitively pulsed (f ~ 10–15 kHz) laser action with a wavelength of 1.064 μm and a power density q = 54 MW/cm2 on La0.4Ba0.6CoO3 ceramics at a vacuum chamber pressure p = 2.2 Pa. The morphology of the obtained films was studied using atomic-force microscopy. Features of transmission spectra in the visible, near-, and mid-IR regions were revealed. The electrophysical properties of the La0.4Ba0.6CoO3 structure were analyzed.

An improved mathematical model bidirectional coupling of heat-water and mechanics during vacuum pre-cooling

Vacuum pre-cooling is a multi-physics process coupling heat transfer, water transport, and shrinkage, the stresses caused by water evaporation and temperature variation in food interact with its deformation. However, the developed models usually assume that the shrinkage of food is insignificant so that it is ignored, which is inconsistent with the actual vacuum pre-cooling process and makes the simulation results inaccurate. Taking strawberry as an example, a multiphase porous media model with heat-water and mechanics (HWM) bi-directional coupling was developed for food vacuum pre-cooling. The accuracy of the HWM model was verified by comparing the heat-water (HW) model without considering shrinkage and the experiments. The results show that the development of the evaporation front predicted by the HWM model is more sensitive to the vacuum chamber pressure change compared with the HW model. The maximum average relative errors corresponding to the temperature and shrinkage of the HWM model are 0.27% and 6.95%, respectively, which are better than the HW model. In addition, the edge gradient effect that occurs in the middle stage of vacuum pre-cooling was observed. When the vacuum chamber pressure approached the lowest point, the evaporation region rapidly developed toward the core. The increase of evaporation driving force and the decrease of boundary moisture caused drastic temperature and shrinkage changes on the product surface. The model developed in this paper considering shrinkage provides technical support to optimize the vacuum pre-cooling process and improve product quality.

An environmental monitoring network for quantum gas experiments and devices

Quantum technology is approaching a level of maturity, recently demonstrated in space-borne experiments and in-field measurements, which would allow for adoption by non-specialist users. Parallel advancements made in microprocessor-based electronics and database software can be combined to create robust, versatile and modular experimental monitoring systems. Here, we describe a monitoring network used across a number of cold atom laboratories with a shared laser system. The ability to diagnose malfunction, unexpected or unintended behavior and passively collect data for key experimental parameters, such as vacuum chamber pressure, laser beam power, or resistances of important conductors, significantly reduces debugging time. This allows for efficient control over a number of experiments and remote control when access is limited.

气吸式排种器的气流场特性试验研究

The vacuum seed metering device absorbs seeds by using the negative pressure generated by vacuum air flow. Therefore, it is of great significance to study the variation law of pyrolysis gas flow field to improve its seed metering performance. In this paper, the common disc and composite disc were selected as the research objects and tested on the indoor test-bed. The negative pressure was measured by U-type barometer, and the effects of fan speed, suction hole size, seed hole structure and air chamber thickness on the air flow field were studied. Firstly, the influence of fan rotation frequency on vacuum chamber negative pressure is studied, and the variation law of negative pressure in vacuum chamber and fan port of common disc and composite disc under the same frequency is compared. Secondly, the suction holes in the vacuum chamber were numbered, the negative pressure distribution of the suction holes was measured, and the influence of the number and diameter of the suction holes on the negative pressure of the vacuum chamber was studied. Finally, the negative pressure was measured at the distance of 0 to 10 mm from the suction hole to study the effect of seed hole structure on the air flow field. Moreover, increase the additional thickness of the vacuum chamber from 0 to 40 mm to study the influence of the chamber thickness on the distribution of the gas flow field. This paper makes a comprehensive experimental analysis on the influencing factors of air flow field of air suction seed metering device, necessary for future design of air suction seed metering device.

Large‐Scale Fabrication of Surface Ion Traps on a 300 mm Glass Wafer

Herein, a large‐scale fabrication of radio frequency (RF) surface ion traps on a 300 mm glass wafer using a standard foundry process is reported. Established wafer‐level packaging process of electroplated Cu with Au finish is used to fabricate the surface electrodes directly on the glass wafer substrate. A trap is tested by loading it with laser‐cooled 88Sr+ ions. The trap shows a stable operation with RF amplitudes in the range of 100–250 V at 33 MHz frequency. The ion lifetime is on the order of 30 min with laser cooling with a vacuum chamber pressure of ≈5 × 10−11 mbar. These results demonstrate the potential of large‐size foundry glass substrates to realize scalable and integratable trapped ion‐based quantum devices.

Experimental investigations of thermal properties of icy lunar regolith and their influence on phase change interface movement

Heat and mass transfers occurring on surface and within subsurface of extraterrestrial bodies during natural and future industrial heating processes require knowledge of thermal properties of porous dry and icy materials. This paper investigates thermal properties of icy lunar regolith with various water ice contents and their influence on phase change interface movement. A series of experiments has been employed to simulate borehole heating of icy regolith samples under low vacuum (0.1–1.5 ​Torr) and very low temperatures (>93 ​K) using JSC-1A regolith analogs prepared as “mud-pies” with water contents from 0 to 15 ​wt%. Cylindrical samples were heated via cartridge heater located in the center of the samples. Real-time measurements of temperatures in an array of points and vacuum chamber pressures were recorded. To decipher thermal properties data in this inverse heat equation problem, a 3D finite element method modelling has been used to simulate the behaviour of both the samples and the vacuum chamber. The results provided rough matches with expected thermal properties and the model was used in determination of phase change interface movement in the samples. These results could be applicable to research on properties and composition of other rocky and icy extraterrestrial objects or design of water ice prospecting instruments. Most importantly they should improve our understanding of processes applied in extraterrestrial water mining and visualize engineering challenges of these processes.

Pressure Effects on Stopping Power of Alpha Particles in Argon Gas

This paper aims to evaluate the range and stopping power of alpha particles in argon gas at different pressure of 0 to 1 bar, using the alpha radiation energy. The results show that the energy of the passed alpha particles has been decreased with increasing pressure in a small vacuum chamber. It is also observed that the amount of alpha particles reaching the detector follows a decreasing behavior as the distance increases. Experimental, SRIM and theoretical results for range and stopping power are closely in a good agreement. The errors in the measured range and stopping power data results from random. Only random errors have been considered in the present analysis and were estimated from pressure measurements and the uncertainty of the gas temperature.

Development of control systems on vacuum evaporators with 50 l capacity to reduce honey water content accordance to sni 01-3545-2004

Riau still has many protected forests and nature reserves. One of the wealth of protected debt is the forest’s Honey. One of the weaknesses of forest honey is the high water content in honey. The permissible water content in honey is 22% based on SNI 01-3545-2004. This paper presents a vacuum evaporator of control system design as a tool for reducing the water content in Honey. The control system design is made such that the honey temperature in the evaporation process is no more than 40°C. There are three quantities that are controlled in this process, namely vacuum chamber pressure, temperature and screw rotation. Temperature control system and pressure control system use close loop system, while the control system for screw rotation uses open loop system. The three main components of this control system are the VE 115N vacuum pump, the stirring screw motor with 1 HP power, 2 heaters with 250 watts of power each, Temperature Control (Eliwell IC901 thermostat and thermistor sensor), 35x25 panel box. To meet the quality of honey, the control system is set with a maximum temperature of heating water 40°C and vacuum pressure at 7.4 kPa and screw rotation at 60 rpm