What Is a Vacuum Bell?

The meaning of vacuum refers to a gas state below a barometric pressure in a given space, which is a physical phenomenon. In "Void", sound cannot be transmitted because there is no medium, but the transmission of electromagnetic waves is not affected by vacuum. In fact, in vacuum technology, for the atmosphere, a part of the material inside a specific space is discharged, so that its pressure is less than a standard atmospheric pressure. We call this space a vacuum or vacuum state. Vacuum is often used as a unit of pressure for Pascal or Torr. In the natural environment, only outer space can be called the closest space to a vacuum.

In 1641, the Italian mathematician Torricelli filled a long tube with mercury, and then slowly inverted the nozzle in a mercury-filled basin. The end of the mercury column in the tube was 76 cm high. At this time, the mercury-free zone at the top of the glass tube is in a vacuum state. This experiment is called the "Tori split profit experiment", and the glass tube that completed the experiment is the "Tori split profit tube".

When Einstein used the theory of field theory to study the phenomenon of gravity, he had realized that there was nothing wrong with the idea of vacuum. He had proposed the idea that vacuum is a special state of gravity field. The first to give the vacuum a new physical content was PAM Dirac. In 1930, in order to get rid of the dilemma of the negative energy solution of the Dirac equation, Dirac proposed that vacuum is a sea of electrons filled with negative energy states.

Chinese name: vacuum
Category: Space state
Related disciplines: physical

Pressure: Less than one standard atmosphere
Experiment: Madburg Hemisphere Experiment
The basic principle: Vacuum is a physical concept, space is a mathematical concept

Vacuum History Allusion

In 1654, Mayor of Madenburg Otto von Glick showed the hemisphere experiment he designed to the Emperor in Regensburg. He made two red copper hemispheres with a diameter of 51 cm, with a layer of oil-soaked leather in the middle to make the two hemispheres completely fit. Then he used his home-made vacuum pump to evacuate the air from the ball. At this time, the two heavy copper hemispheres were closely integrated into one without any adhesive, which was very surprising. But the climax of Glick's experiment is just about to begin, in order to prove how tight and solid the combination of the two hemispheres is. The mayor pulled in 16 horses and split them into two teams. In a loud noise, the two hemispheres were pulled apart. This is the famous "Magdeburg hemispheres test" in the history of physics.

Vacuum vacuum classification

Many modern high-precision products are required at certain stages in the manufacturing process

Vacuum (2 photos)

It can be manufactured with different degrees of vacuum, such as semiconductors, hard disks, and lenses. The way to create vacuum in laboratories and factories is to use a pump to extract air in a confined space to achieve a certain degree of vacuum. According to the level of pressure in vacuum technology, we can distinguish:

Rough Vacuum 760 ~ 10 Torr

Medium Vacuum 10 ~ Torr

High Vacuum ~ Torr

Ultra-High Vacuum Torr or less

Definition of Vacuum Physics

Basic vacuum concepts

According to its etymology, it originally refers to the void, that is, a space with nothing. Vacuum in industry and vacuum science means that when the pressure in the container is lower than the atmospheric pressure, the part below the atmospheric pressure is called vacuum, and the pressure in the container is called absolute pressure; The space in a container with low atmospheric pressure is called vacuum. Industrial vacuum has a degree of difference: when there is no pressure in the container, that is, the absolute pressure is equal to zero, it is called full vacuum; the rest are called incomplete vacuum. The vacuum in Dirac's previous physical theory, such as special relativity, specifically refers to the state of space in which no matter exists, which corresponds to the complete vacuum in industry. According to the viewpoint of modern physical quantum field theory, the vacuum is not empty, which contains extremely rich physical content. Vacuum in special relativity and other theories is only an approximation when Planck's constant approaches zero.

Vacuum science

As far back as 1643, Italian physicist Torricelli discovered that the atmosphere and atmospheric pressure exist in vacuum and natural space. When he filled a long glass tube with one end closed with mercury and put it upside down in a mercury tank, he found that the mercury level in the tube dropped until it was 76 cm away from the mercury level outside the tube. Torricelli believes that the space on the mercury surface of the glass tube is a vacuum, and 76 cm of mercury is due to atmospheric pressure.

In 1650, Germany's Gelik made a piston vacuum pump.

In 1654, he conducted the famous Heidelberg hemisphere test in Heidelberg: a vacuum pump was used to vacuum two two 14-inch (35.5 cm) copper hemispheres together, and then two groups of eight horses were used. The horse pulled the copper ball in the opposite direction and failed to separate the two hemispheres. This famous experiment proved once again that there is an atmosphere in space and that the atmosphere is under tremendous pressure. To commemorate Torricelli's major scientific discoveries and contributions, the vacuum pressure unit used in the past was named after him.

In the mid to late 19th century, the success of the British Industrial Revolution promoted the development of productivity and scientific experiments, and also promoted the development of vacuum technology.

In 1850 and 1865, mercury column vacuum pumps and mercury drop vacuum pumps were invented, and developed into incandescent bulbs (1879), cathode ray tubes (1879), dewars (1893), and compression vacuum gauges (1874). For the first time, the application of a compression vacuum gauge made it possible to measure low pressures.

At the beginning of the 20th century, the emergence of vacuum tubes promoted the development of vacuum technology to high vacuum.

Gas ballast vacuum pumps, oil diffusion pumps, and cold cathode ionization meters were invented from 1935 to 1937. These results and the Pirani vacuum gauge made in 1906 are still commonly used in most vacuum systems today.

After 1940, the application of vacuum expanded to nuclear research (cyclotron and isotope separation, etc.), vacuum metallurgy, vacuum coating and freeze-drying. Vacuum technology began to become an independent discipline. During the Second World War, the need for atomic physics experiments and the need for high-quality electrical vacuum devices for communications further promoted the development of vacuum technology.

Fundamental

Vacuum is a concept in physics, which initially reflects the state of nothingness, similar to "none". In the 20th century, PAM Dirac put forward the concept of the so-called quantum vacuum, that is, vacuum is not empty, but is always transformed by virtual particles and physical particles, but the whole is a macroscopic total that does not show physical properties to the outside. Vacuum is a sea of energy, an objective existence that is constantly oscillating and filled with huge energy; space is just a mathematical concept, and it reflects the concepts of the attributes of motion and geometric size. That is to say, space and vacuum are a mathematical concept and a physical concept. The properties of a vacuum do need to be described using space, but that is just a mathematical expression, a parameter introduced for the sake of research, not that the nature of a vacuum depends on space.

Vacuum recognition process

Human understanding of vacuum has undergone several fundamental changes and iterations. The atomic theory of Democritus in ancient Greece believed that all matter is composed of atoms, and outside the atom is void. In the 17th century, R. Descartes proposed the etheric vortex theory, thinking that the space is full of ether and used to explain the movement of the planets. Soon I. Newton established Newton's mechanics based on the three laws of motion and the law of universal gravitation, which successfully solved the problem of planets orbiting the sun. Gravity is considered to act at a distance and does not require the sun as a transmission medium, thus negating the ether theory. The volatility of light was discovered in the 19th century. It was believed that the propagation of waves must depend on the medium. In particular, the volatility of electromagnetic fields was later discovered. Etherism re-emerged. No matter when and where in the universe, any object is full of ether, light and Electromagnetic waves are interpreted as mechanical vibrations of the ether. Later, although there was a change in concept, the light and electromagnetic waves were regarded as the vibration of the electromagnetic field, but the ether still retained some absolute properties, which could be regarded as an absolute still reference frame describing the movement of all things. At the end of the 19th century and the beginning of the 20th century, all kinds of experiments that attempted to detect the speed of the earth's movement relative to the ether failed. A. Einstein established the special theory of relativity, which once again denied the existence of this absolute static ether. Later, when Einstein used the theory of field theory to study the phenomenon of gravity, he realized that the vacuum concept of nothingness is problematic. He once proposed that vacuum is a special state of the gravitational field .

Vacuum circuit breaker The first to give the vacuum a new physical content was PAM Dirac. In 1930, in order to get rid of the dilemma of the negative energy solution of the Dirac equation, Dirac proposed that vacuum is a sea of electrons filled with negative energy states. When the electrons in the negative energy state have absorbed enough energy to transition to the positive energy state and become ordinary electrons, the observable holes can be left in the sea of electrons, that is, the positrons. From the perspective of the energy of the system, this situation is higher than the vacuum state of the sea of electrons only, so the vacuum is the lowest energy state. From the perspective of modern quantum field theory, each particle corresponds to a kind of quantum field, and the particle is the corresponding field quantized field quantum. When a particle exists in space, it indicates that the quantum field is in an excited state; otherwise, when a particle does not exist, it means that the field is in the ground state. Therefore, a vacuum is a state in which no field quantum is excited, or a vacuum is the ground state of a quantum field system.

Modern knowledge about vacuum is no longer philosophical speculation, but can be tested by experiments. Many phenomena need to be explained by modern concepts of vacuum. For example, the Lamb shift of the hydrogen atom energy level and the abnormal magnetic moment of electrons have been experimentally confirmed with a very high accuracy. The effect of vacuum polarization has been confirmed with high accuracy; The emergence of a large number of particles is also a good proof. The understanding of vacuum is still in the initial stage of exploration. Physicists are still exploring issues such as vacuum spontaneous breaking and vacuum phase transition, which will definitely promote the further development of physics.

Vacuum meaning characteristics

In vacuum science, the meaning of vacuum refers to the state of a gas below a barometric pressure in a given space. This thin gas state is often referred to as a vacuum condition. Compared with the state of the atmosphere on which human beings live, this particular vacuum state has the following basic characteristics: (1) The gas pressure in a vacuum state is lower than one atmosphere, so various vacuums on the surface of the earth In a container, it will be subject to atmospheric pressure, and the magnitude of the pressure difference is determined by the pressure difference between the inside and outside of the container. Since an atmospheric pressure acting on the surface of the earth is about 101325 N / m ^ 2, when the pressure in the container is very small, the atmospheric pressure that the container can bear can reach one atmosphere.

(2) Due to the thinness of the gas under vacuum , the number of gas molecules per unit volume, that is, the molecular density of the gas is less than the density of the gas molecules at atmospheric pressure. Therefore, the number of collisions between molecules, between molecules and other particles (such as electrons, ions, etc.) and between molecules and various surfaces (such as vessel walls) is relatively reduced, which increases the molecular free path of the gas.

Overview of Vacuum Technology

vacuum technique A technique in which the pressure of a gas is lower than the atmospheric pressure on the ground.

Vacuum refers to a thin gas space with a pressure much lower than 101.325 kilopascals (kPa) (that is, 1 atmosphere). In vacuum technology, in addition to the pressure unit Pa of the International System of Units, Torr is often used as the unit of vacuum. 1 Torr is equal to the pressure generated by 1 mm of Hg, which is 1Torr = 133.3224Pa.

According to the difference in gas pressure, the vacuum range is usually divided into: low vacuum 1 × 105 1 × 102Pa, medium vacuum 1 × 102 ~ 1 × 10-1Pa, high vacuum 1 × 10-1 1 × 10-5Pa, Ultra high vacuum 1 × 10-5 1 × 10-9 Pa, extremely high vacuum 1 × 10-9Pa or less.

Vacuum technology includes the acquisition, measurement, and application of vacuum.

Piston pumps, rotary vane pumps, etc. change the volume of the pump body through continuous movement of the piston or rotary vane, and discharge the gas to obtain a vacuum. The diffusion pump uses high-speed moving air to remove the gas molecules that have diffused into the pump body. In addition, there are cryogenic pumps that use low-temperature surfaces to condense or freeze the gas, such as liquid helium condensate pumps; adsorption pumps that use the gettering effect of getter materials such as activated carbon, and so on.

A gauge that measures the degree of vacuum, that is, the pressure of a thin gas, is called a vacuum gauge or vacuum gauge. Can be divided into two types of absolute vacuum gauge and relative vacuum gauge. The former directly determines the size of the air pressure through the physical quantity measured by itself, such as a U-shaped tube, a film gauge, a McLaugh vacuum gauge (using Boyle's law), a thermocouple vacuum gauge, etc .; Measure air pressure, such as ionization vacuum gauge, Pirani vacuum gauge, damping vacuum gauge, etc.

The pressure difference between the vacuum and the ground atmosphere can be used to transport fluids and dust. With the small density of gas molecules in the vacuum, various electric vacuum devices such as electric light sources, electronic tubes, etc. can be manufactured. The vacuum environment is conducive to the welding and smelting of certain metals, the fractionation and purification of certain low melting metals such as Mg, Li, Zn, etc., and the reduction of oxides of certain active metals such as Ca, Li, Cs, etc. Low-temperature dehydration at ~ 10-1Pa) and vacuum drying have been successfully used to concentrate foods, milk powder, and manufacture plasma. Isotopic separation, processing of large-scale integrated circuits, and coatings also need to be performed in a vacuum environment. In scientific research, such as surface physics experiments, various accelerators, fusion reactions, and space environment simulations are inseparable from vacuum.

Vacuum physical properties

This refers to the space in which no physical particles exist, but the space in which nothing exists does not exist. And suppose you chase away all the gas in a space, you will find that there are still elementary particles that appear and disappear in a vacuum from time to time , and nothing is created . The physical vacuum is actually a sea of energy that fluctuates constantly . When the energy reaches the peak , the energy is converted into a pair of elementary and negative elementary particles . When the energy reaches the trough, the pair of elementary and negative elementary particles are annihilated to each other and converted into energy.

Vacuum has the following properties:

1. Nothing is empty. If there are no particles in the vacuum, we will accurately measure the field (0) and the changing curvature (0) of the field. However, the Heisenberg uncertainty principle indicates that we cannot accurately measure a pair of conjugate quantities at the same time, Can be "empty", not "none". Therefore, in a vacuum, particles are constantly generated in the form of virtual particles and virtual anti-particle pairs, and they annihilate each other. In the process, the total energy remains unchanged.

2. The vacuum has polarity. So vacuum is asymmetric. But this asymmetry is relatively local and symmetrical in the relative whole. Such cyclic nesting constitutes this property of vacuum.

3. Each part of the vacuum has the whole nature of the vacuum. Big and small are relative. Time is also relative to space. Time cannot exist independently of specific space.

Vacuum practical application

Life applications

Vacuum packaging of puffed food can prevent food spoilage and prolong food storage time;

Vacuum bulb to prevent the filament from being oxidized and prolong the service life.

Industrial production

Industrial vacuum refers to a gas space with a pressure lower than a standard atmospheric pressure, and refers to a thin gas state. It can be divided into high vacuum, medium vacuum, and low vacuum. The vast space between the earth and the planet is a vacuum. Vacuum is usually obtained with a special air extractor. Its gas thinness is measured with a vacuum gauge, and we have been able to obtain a high vacuum of 0.00000 00001 atm using molecular and diffuser extractors. Vacuum has great applications in science and technology, electric vacuum instruments, electronic tubes and other electronic instruments.

	Vacuum area support (Torr)	Pressure range) Pa (Pa)
Low vacuum	760 ~ 10	101325 ~ 1333
Medium vacuum	10 ~ 10-3	1333 ~ 1.33 × 10-1
High vacuum	10-3 ~ 10-8	1.33 × 10-1 ~ 10-6
Ultra-high vacuum	10-8 ~ 10-12	10-6 ~ 10-10
Very high vacuum	<10-12	<10-10

Positron electron collider

The role of the positron collider is far more than just a pair of positrons colliding to generate photons and energy. A pair of photons can also collide to produce a pair of positrons and negative protons. The collision makes the collision where it is. That part of the vacuum can be excited to a high-energy state, which can produce more various elementary particles, which serve to study the origin and composition of the universe.

Vacuum research applications

The vacuum and microgravity environment provided by spacecraft orbital flight is a treasure trove, providing people with scientific experiments and production process conditions that are difficult to obtain on the ground, conducting scientific experiments that are difficult to perform on the ground, producing materials that are difficult to produce on the ground, industrial Products and drugs.

Life and biological science experiments are performed in a high vacuum and microgravity environment. There will be no organic contamination, mixing or measurement errors, and experimental microorganisms such as bacteria will not spread everywhere, which is very safe. Under zero-gravity or micro-gravity conditions, containerless smelting can be performed, which will not contain any impurities, and high-quality alloys can be obtained; metals or non-metals with different specific gravity can be uniformly mixed to obtain new alloy materials; it can overcome Defects such as subcooled undulations and high densities in ground processing have grown semiconductor materials such as high-quality, large-diameter single crystal gallium arsenide; and can produce ball industrial products such as ball bearings with 100% roundness. On the ground, Due to the influence of gravity, ball bearings and the like are not always truly spherical.

Space pharmacy is an important aspect of the use of vacuum and microgravity environments. For pharmaceuticals on the ground, due to the gravity of the earth, the culture will precipitate, and the microorganisms in the precipitate will die due to lack of oxygen; if the oxygen is stirred, the formed low-pressure small bubbles will damage the cells; if an antifoaming agent is added, It will reduce the solubility of oxygen, hinder the reproduction of microorganisms, and form a vicious cycle. In the microgravity environment, the culture liquid contains a large number of air bubbles, and it will not precipitate, and the microorganisms can obtain oxygen at any time, and the growth rate is more than twice as fast as the ground. Can produce many drugs with high efficiency and high purity, such as epidermal growth hormone for treating burns, erythropoietin for treating anemia, immune serum for preventing and treating viral infection, trypsin inhibitor for treating emphysema, urokinase for treating thrombosis, treatment Anti-hemolytic factor of hemophilia 8. There are more than 40 kinds of beta cells for treating diabetes and interferon for treating cancer. The main pharmaceutical method is electrophoresis, which accurately separates mixtures of different components into different components under the action of a DC electric field. The first generation of its equipment is a static electrophoresis instrument, and the second generation is a continuous flow electrophoresis instrument.

system

The structural material of the vacuum system is the material constituting the main body of the vacuum system, which separates the vacuum system from the atmosphere and withstands atmospheric pressure. Such materials are mainly a variety of metallic and non-metallic materials, including seal gasket materials at removable connections.

In cold traps, there is always a more or less part of the oil vapor flowing back into the high vacuum end. The pressure they build at the diffuser pump port is sometimes much higher than the saturated oil vapor pressure at the pump wall temperature. This not only affects the ultimate pressure of the vacuum system, but also causes pollution to the pumped container, so the oil return rate is the main evaluation index of the diffusion pump system.

Vacuum packaging Vacuum packaging puts food in the packaging bag, extracts the air in the packaging bag, and reaches the predetermined vacuum degree, and then completes the sealing process. Vacuum inflation packaging puts food into the packaging bag. After the air in the packaging bag has reached a predetermined vacuum degree, it is filled with nitrogen or other mixed gas, and then the sealing process is completed.

The main role of vacuum packaging is to remove oxygen to help prevent food spoilage. The principle is relatively simple. The food mold decay is mainly caused by the activities of microorganisms, and most microorganisms (such as molds and yeasts) need oxygen to survive. Vacuum packaging uses this principle to remove the oxygen in the packaging bag and food cells, so that the microorganisms lose their living environment.

measuring

Most of the sensors for vacuum measurement use ionization gauges, and they are most widely used in the medium range vacuum range. Commonly used ionization vacuum gauges use analog circuits to control the emission current and calculate it as a fixed number. This will cause some disadvantages, such as deviations in current due to external interference or aging of components; or control loops. The drift in the measurement results in instability, which results in a large measurement error. In order to eliminate this kind of bad phenomenon, we apply modern control theoryPID and Fuzzy control. The digital circuit is used to control the transmit current. Both 16-bit high-resolution A / D and D / A are used in the control loop. Participation in calculation allows a certain range of variation of the emission current. This not only improves the measurement accuracy, but also expands the range in their linear region.

Basic standard

GB 4982 4983-85 Vacuum quick release flange

GB 4982-85 clamp type vacuum quick release flange

GB 4983-85 tightening type vacuum quick release flange

GB 6071.1 6071.3-85 ultra high vacuum flange

GB 6071.1-85 ultra high vacuum flange structure

GB 6071.2-85 ultra high vacuum flange size

GB 6071.3-85 copper gasket for ultra-high vacuum flange

GB / T 3163-93 Vacuum technical terms

GB / T 3164-93 Graphic symbols for vacuum technology systems

GB / T 6070-1995 vacuum flange

GB / T 16709-1996 Vacuum technology pipe fitting assembly dimensions

JB 1090 1092-91 vacuum dynamic seal type and size

JB 1090-91 Type and size of rubber seal for J type vacuum

Type and size of JB 1091-91 JO type skeleton type rubber seal ring for vacuum

JB 1092-91 O type vacuum rubber seal ring type and size

JB 5278.1 5278.3-91 Copper wire sealable bakeable vacuum flange

JB 5278.1-91 copper wire sealable bakeable vacuum flange connection type

JB 5278.2-91 copper wire sealable bakeable vacuum flange flange structure size

JB 5278.3-91 copper wire sealable vacuum flange copper wire seal ring structure size

JB / T 7673-95 vacuum equipment model compilation method

JB / T 8105.1 8105.2-1999 vacuum gauge pipe joint

JB / T 8105.1-1999 rubber sealed vacuum gauge pipe joint

JB / T 8105.2-1999 metal sealed vacuum gauge pipe joint