-
Can you explain in detail the applications of ultra-high vacuum (UHV)?
Ultra-High Vacuum (UHV) refers to an extremely low-pressure environment, typically below 1×10^-7 Pascals and can reach down to less than 1×10^-10 Pascals. In such conditions, only a very small number of molecules exist per cubic centimeter, making UHV crucial for various scientific research and technological applications. Here are some key applications of UHV:Surface Science: Experiments conducted under UHV greatly reduce the risk of surface contamination and oxidation since there are virtually no residual gas molecules to react with the sample surfaces. This makes UHV ideal for studying the physical and chemical properties of material surfaces, including adsorption, desorption processes, and catalysis.Thin Film Growth Technologies: Techniques like Molecular Beam Epitaxy (MBE) and Atomic Layer Deposition (ALD) require extremely pure environments to ensure the quality and uniformity of the thin films produced. UHV conditions prevent the introduction of impurities, thus guaranteeing the
View -
How is vacuum categorized? (Rough vacuum, Medium vacuum, High vacuum, Ultra-high vacuum, Extreme high vacuum).
Vacuum can be classified into five categories based on their pressure range, which reflects the number of gas molecules per unit area:Rough Vacuum: This ranges from atmospheric pressure (around 101325 Pascals) to approximately 2.7×10^-2 Pascals. It's the easiest level of vacuum to achieve and is commonly seen in household appliances like vacuum cleaners.Medium Vacuum: The pressure here lies between roughly 2.7×10^-2 Pascals and 1×10^-4 Pascals. This level of vacuum is often used in some industrial processes.High Vacuum: In this category, the pressure falls within 1×10^-4 Pascals to 1×10^-7 Pascals. At this level, only several million molecules exist per cubic centimeter, suitable for processes like coating.Ultra-High Vacuum (UHV): This ranges from 1×10^-7 Pascals down to less than 1×10^-10 Pascals. Such a high degree of vacuum is crucial for experiments in surface science.Extreme High Vacuum: Generally refers to pressures below 1×10^-10 Pascals, representing extreme conditions used in
View -
What is the basic principle of vacuum extraction
The principle of vacuum extraction primarily hinges on the theories of gas kinetics and thermodynamics within physics. The essence lies in reducing the number of gas molecules within a closed system through various methods, thereby lowering the system's pressure below standard atmospheric pressure (approximately 101.325 kPa), resulting in a "vacuum" state.Key approaches to achieve this include:Mechanical Action: The most common method involves using a vacuum pump. Vacuum pumps remove gases from a space through different mechanisms. For instance, rotary vane pumps capture gases mechanically and compress them before releasing them into the atmosphere outside the pump; turbomolecular pumps rely on high-speed rotating rotors colliding with gas molecules, directing them towards the exhaust.Diffusion and Adsorption: In high or ultra-high vacuum systems, getter materials may be employed to further reduce residual gas pressure. These materials effectively adsorb gas molecules, further decreasi
View -
The Working Principle of Vacuum Pumps
A vacuum pump is a critical device designed to remove gas molecules from a sealed space, thereby reducing the internal pressure and creating or maintaining a vacuum environment. These pumps are widely used in scientific research, semiconductor manufacturing, thin-film coating, freeze-drying, medical equipment, aerospace, and many other fields. Depending on their operating methods and the vacuum levels they achieve, vacuum pumps come in various types, each based on distinct working principles. Below is an overview of the fundamental mechanisms of several common types.Mechanical Vacuum Pumps (e.g., Rotary Vane Pump, Scroll Pump)These pumps belong to the category of positive displacement pumps, which operate by mechanically changing the volume of a chamber to draw in and expel gas.Take the widely used rotary vane pump as an example: Inside the pump housing, an eccentric rotor equipped with sliding vanes rotates. As the rotor turns, centrifugal force and springs push the vanes against the
View -
Common Vacuum Measurement Units and Their Conversion
Common units for measuring vacuum levels include Pascal (Pa), millibar (mbar), Torr, and standard atmosphere (atm). Here are the conversion relationships between these units:Pascal (Pa)is the SI unit for pressure.1 Pa = 0.00750062 Torr1 Pa = 0.01 mbar1 Pa = 9.86923×10^-6 atmMillibar (mbar)is another commonly used engineering unit, especially in meteorology.1 mbar = 100 Pa1 mbar = 0.750062 Torr1 mbar = 9.86923×10^-4 atmTorris named after the Italian physicist Evangelista Torricelli and is primarily used to describe low pressures.1 Torr = 133.322 Pa1 Torr = 1.33322 mbar1 Torr = 1/760 atmStandard Atmosphere (atm)is defined as the average atmospheric pressure at sea level at 0°C.1 atm = 101325 Pa1 atm = 1013.25 mbar1 atm = 760 TorrThese conversion factors allow you to switch between different units depending on your application. For example, Pascals might be more common in scientific research, while millibars or Torr may be encountered more frequently in industrial applications. Standard a
View -
What is a vacuum, and how is vacuum level defined
Avacuumis a space where the pressure is lower than the standard atmospheric pressure (101.325 kPa or 101 kPa), meaning it contains fewer gas molecules than the surrounding atmosphere.Thevacuum level(or degree of vacuum) measures how much lower the pressure is compared to atmospheric pressure. It is defined as:Vacuum Level = Atmospheric Pressure – Absolute PressureThis value is always positive and indicates how close the space is to a perfect vacuum. For example, a vacuum of “-75 kPa” or “90% vacuum” means the pressure inside is 75 kPa below atmospheric pressure or 10% of atmospheric pressure remaining, respectively.
View -
Understanding the Relationship Between Pressure, Gas Load, and Pumping Speed in Vacuum Systems
In vacuum systems, the simple equationQ = P × Sis used to explain almost every design challenge. Gas load (Q), pressure (P), and pumping speed (S) are the three variables whose balance determines how well a vacuum system performs.1. How to Reach a Lower Pressure (P)?Reaching a lower pressure is often the hardest part of vacuum work. Once you understand that pressure depends on the balance between the system’s gas load (Q) and the available pumping speed (S), the task becomes clearer.Below are the key concepts in more detail.2. Understanding Pressure (P)Pressure (P) is the force per unit area exerted by gas molecules colliding with a surface.To reduce pressure (P):Increase pumping speed (S), and/orDecrease gas load (Q).3. Understanding Pumping Speed (S)Pumping speed (S) is the volumetric rate at which a pump removes gas from the chamber.To reduce pressure (P):Increase pumping speed (S), and/orUse larger-diameter and/or shorter lines between pump and chamber.4. Understanding Gas Load (Q)
View -
Vacuum Generation Methods in Semiconductor Manufacturing Equipment
Introduction to VacuumVacuum refers to a space devoid of any matter or with extremely thin gas, typically defined as a state where the pressure is below one standard atmosphere (101325 Pa). It plays a pivotal role in semiconductor manufacturing by providing environments essential for various processes.Applications of Vacuum in Semiconductor EquipmentWafer/Reticle Handling: Utilizes vacuum to securely hold wafers and reticles during processing.Creating Reaction Conditions: Vacuum conditions are crucial for reducing impurities and ensuring high purity and structural integrity of materials used in semiconductor devices.Specific Applications:Crystal Growth Equipment: For instance, in the production of single-crystal silicon using the Czochralski method, a low-oxygen vacuum environment minimizes impurity incorporation, enhancing crystal quality.Compound Semiconductor Growth: Precise control over stoichiometry during growth under vacuum ensures optimal electrical performance of compound semi
View -
Common calculation formulas for vacuum physics and vacuum
1. Boyle's Law: When the temperature remains constant, the relationship between gas pressure P and volume V is P · V=constant, that is, P1/P2=V2/V1.2. Gay Lussac's law: When the pressure P is constant, the volume V of the gas is proportional to the absolute temperature T, such as V1/V2=T1/T2=constant. For every 1 ℃ increase (or decrease), the volume changes by 1/273 times.3. Charlie's Law: In the case of a constant volume V, the gas pressure P is proportional to T, that is, P1/P2=T1/T2. A temperature change of 1 ℃ results in a corresponding increase or decrease of 1/273 in pressure.4. Average free path: λ=5 × 10-3/P (cm) describes the average free path of gas molecules.5. Pumping speed calculation: S=dv/dt (liters/second) or S=Q/P, where Q is flow rate, P is pressure, V is volume, and t is time.6. Conductivity formula: C=Q/(P2-P1) (liters/second) represents the ability of fluid to pass through a pipeline.7. Vacuum pumping time: t=8V/S, empirical formula, used to estimate the pumping ti
View -
What is the degree of vacuum considered as vacuum
In engineering and technical contexts, a space is considered under vacuum as soon as its absolute pressure is below standard atmospheric pressure (101 325 Pa or 1 atm).
View
Wiki
