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一种新的微波武器——Maser（激微波）介绍
这个是我在维基查阅激光词条无意中找到的~~~~~~~~~~~~~~~~~~~~~~~~~~
激微波
(
MASER，或者音译为
迈射）是
受激放大微波辐射（
Microwave Amplification by Stimulated Emission of Radiation）的头字母。它指通过受激辐射放大和必要的反馈，产生同一波宽、准直、相干的
微波的过程及仪器。
鉴于这玩意的国内中文方面的详细介绍几乎没有，在此将直接引用维基百科的英文介绍：
鉴于网上的大多数翻译不靠谱，要翻译的话，请自行~~~~~~~~~
+
From Wikipedia, the free encyclopedia.
For other uses, see
Maser (disambiguation).
A
maser is a device that produces
coherent
electromagnetic wavesthrough amplification by
stimulated emission. Historically, “maser” derives from the original, upper-case acronym
MASER, which stands for "
Microwave
Amplification by
Stimulated Emission of
Radiation". The lower-case usage arose from technological development having rendered the original denotation imprecise, because contemporary masers emit EM waves (
microwave and
radio frequencies) across a broader band of the
electromagnetic spectrum; thus, the
physicist
Charles H. Townes’s suggested usage of “
molecular” replacing “microwave”, for contemporary linguistic accuracy.
[1] In 1957, when the optical coherent oscillator was first developed, it was denominated
optical maser, but usually called
laser (Light Amplification by Stimulated Emission of Radiation), the acronym
Gordon Gould established in 1957.
History
The theoretical principles describing the operation of a maser was described by Nikolay Basov and Alexander Prokhorov from Lebedev Institute of Physics at an All-Union Conference on Radio-Spectroscopy held by USSR Academy of Sciences in May 1952.
The results were subsequently published in October 1954. A precursor of the maser was the first show boostedhydrogen device built and tested by physicists Theodor V. Ionescu and Vasile Mihu in 1946. Independently, Charles H. Townes, J. P. Gordon, and H. J. Zeiger built the first ammonia maser at Columbia University in 1953. The device used stimulated emission in a stream of energized ammonia molecules to produce amplification ofmicrowaves at a frequency of 24 gigahertz.
Townes later worked with Arthur L. Schawlow to describe the principle of the optical maser, or laser, whichTheodore H. Maiman first demonstrated in 1960. For their research in this field Townes, Basov, and Prokhorov were awarded the Nobel Prize in Physics in 1964.
Technology
The maser is based on the principle of stimulated emission proposed by Albert Einstein in 1917. When atoms have been induced into an excited energy state, they can amplify radiation at the proper frequency. By putting such an amplifying medium in a resonant cavity, feedback is created that can produce coherent radiation.
[blockquote][edit][/blockquote]Some common types of masers
Uses
Masers serve as high precision frequency references. These "atomic frequency standards" are one of the many forms of atomic clocks. They are also used as electronic amplifiers in radio telescopes. Masers are being developed as directed-energy weapons.
Hydrogen maser
Main article: Hydrogen maser
Today, the most important type of maser is the hydrogen maser which is currently used as an atomic frequency standard. Together with other types of atomic clocks, they constitute the "Temps Atomique International" or TAI. This is the international time scale, which is coordinated by the Bureau International des Poids et Mesures, or BIPM.
It was Norman Ramsey and his colleagues who first realized this device. Today's masers are identical to the original design. The maser oscillation relies on stimulated emission between two hyperfine levels of atomic hydrogen. Here is a brief description of how it works:
Astrophysical masers
Main article: Astrophysical maser
Maser-like stimulated emission also occurs in nature in interstellar space, and is frequently calledsuperradiant emission to distinguish it from laboratory masers. Such emission is observed from molecules such as water (H2O), hydroxyl radicals (OH), methanol (CH3OH), formaldehyde (CH2O), and silicon monoxide (SiO). Water molecules in star-forming regions can undergo a population inversion and emit radiation at 22 GHz, creating the brightest spectral line in the radio universe. Some water masers also emit radiation from a vibrational mode at 96 GHz.
Extremely powerful masers, associated with active galactic nuclei, are known as megamasers and are up to a million times more powerful than stellar masers.
Terminology
The meaning of the term maser has changed slightly since its introduction. Initially the acronym was universally given as "microwave amplification by stimulated emission of radiation," which described devices which emitted in the microwave region of the electromagnetic spectrum.
The principle and concept of stimulated emission has since been extended to more devices and frequencies. Thus the original acronym is sometimes modified, as suggested by Charles H. Townes,[1] to "molecular amplification by stimulated emission of radiation." Some have asserted that Townes's efforts to extend the acronym in this way were primarily motivated by the desire to increase the importance of his invention, and his reputation in the scientific community.[3]
When the laser was developed, Townes and Schawlow and their colleagues at Bell Labs pushed the use of the termoptical maser, but this was largely abandoned in favor of laser, coined by their rival Gordon Gould.[4] In modern usage, devices that emit in the X-ray through infrared portions of the spectrum are typically calledlasers, and devices that emit in the microwave region and below are commonly called masers, regardless of whether they emit microwaves or other frequencies.
Gould originally proposed distinct names for devices that emit in each portion of the spectrum, includinggrasers (gamma ray lasers), xasers (x-ray lasers), uvasers (ultraviolet lasers), lasers (visible lasers),irasers (infrared lasers), masers (microwave masers), and rasers (RF masers). Most of these terms never caught on, however, and all have now become (apart from in science fiction) obsolete except for maser and laser.
In the early 1960s JPL developed a Maser to provide ultra low noise amplification of S band signals received from deep space probes. This Maser used refrigerated Hydrogen to chill the amplifier to four degrees Kelvin. Amplification was achieved by exciting a ruby comb with a 12 GHz Klystron. In the early days it took days to chill [and remove impurities from] the Hydrogen lines. Refrigeration was two stage with a large Linde unit on the ground and a crosshead compressor within the antenna; final injection was at 3000psi through a six thou inch [micrometer adjustable] entry to the chamber. The whole system noise temperature looking at cold sky [2.7K] was 17 degrees K. This gave such a low noise figure that the Mariner 64 Spacecraft could send pictures of Mars back to Earth even though the spacecraft transmitter was only 15 Watts and the signal received was -169 dbm
![200px-Hmaser.svg.png]()
![260px-Hydrogen_maser.gif]()
![maser-.gif]()
![maser_h2.jpg]()
摘自：XXXXXXXXXXXXXXXXXXXXXXX/wiki/Maser [i]
[/b]
激微波
鉴于这玩意的国内中文方面的详细介绍几乎没有，在此将直接引用维基百科的英文介绍：
鉴于网上的大多数翻译不靠谱，要翻译的话，请自行~~~~~~~~~
+
From Wikipedia, the free encyclopedia.
For other uses, see
A
History
The theoretical principles describing the operation of a maser was described by Nikolay Basov and Alexander Prokhorov from Lebedev Institute of Physics at an All-Union Conference on Radio-Spectroscopy held by USSR Academy of Sciences in May 1952.
The results were subsequently published in October 1954. A precursor of the maser was the first show boostedhydrogen device built and tested by physicists Theodor V. Ionescu and Vasile Mihu in 1946. Independently, Charles H. Townes, J. P. Gordon, and H. J. Zeiger built the first ammonia maser at Columbia University in 1953. The device used stimulated emission in a stream of energized ammonia molecules to produce amplification ofmicrowaves at a frequency of 24 gigahertz.
Townes later worked with Arthur L. Schawlow to describe the principle of the optical maser, or laser, whichTheodore H. Maiman first demonstrated in 1960. For their research in this field Townes, Basov, and Prokhorov were awarded the Nobel Prize in Physics in 1964.
Technology
The maser is based on the principle of stimulated emission proposed by Albert Einstein in 1917. When atoms have been induced into an excited energy state, they can amplify radiation at the proper frequency. By putting such an amplifying medium in a resonant cavity, feedback is created that can produce coherent radiation.
[blockquote][edit][/blockquote]Some common types of masers
- Atomic beam masers
- Ammonia maserFree electron maserHydrogen maser
- Rubidium maser
- Ruby maserWhispering-gallery modes iron-sapphire maser
Uses
Masers serve as high precision frequency references. These "atomic frequency standards" are one of the many forms of atomic clocks. They are also used as electronic amplifiers in radio telescopes. Masers are being developed as directed-energy weapons.
Hydrogen maser
Main article: Hydrogen maser
Today, the most important type of maser is the hydrogen maser which is currently used as an atomic frequency standard. Together with other types of atomic clocks, they constitute the "Temps Atomique International" or TAI. This is the international time scale, which is coordinated by the Bureau International des Poids et Mesures, or BIPM.
It was Norman Ramsey and his colleagues who first realized this device. Today's masers are identical to the original design. The maser oscillation relies on stimulated emission between two hyperfine levels of atomic hydrogen. Here is a brief description of how it works:
- First, a beam of atomic hydrogen is produced. This is done by submitting the gas at low pressure to an RF discharge (see the picture on this page).
- The next step is "state selection"—in order to get some stimulated emission, it is necessary to create a population inversion of the atoms. This is done in a way that is very similar to the famous Stern-Gerlach experiment. After passing through an aperture and a magnetic field, many of the atoms in the beam are left in the upper energy level of the lasing transition. From this state, the atoms can decay to the lower state and emit some microwave radiation.
- A high quality factor microwave cavity confines the microwaves and reinjects them repeatedly into the atom beam. The stimulated emission amplifies the microwaves on each pass through the beam. This combination of amplificationand feedback is what defines all oscillators. The resonant frequency of the microwave cavity is exactly tuned to the hyperfine structure of hydrogen: 1420 405 751.768 Hz.
- A small fraction of the signal in the microwave cavity is coupled into a coaxial cable and then sent to a coherent receiver.
- The microwave signal coming out of the maser is very weak (a few pW). The frequency of the signal is fixed and extremely stable. The coherent receiver is used to amplify the signal and change the frequency. This is done using a series of phase-locked loops and a high performance quartz oscillator.
Astrophysical masers
Main article: Astrophysical maser
Maser-like stimulated emission also occurs in nature in interstellar space, and is frequently calledsuperradiant emission to distinguish it from laboratory masers. Such emission is observed from molecules such as water (H2O), hydroxyl radicals (OH), methanol (CH3OH), formaldehyde (CH2O), and silicon monoxide (SiO). Water molecules in star-forming regions can undergo a population inversion and emit radiation at 22 GHz, creating the brightest spectral line in the radio universe. Some water masers also emit radiation from a vibrational mode at 96 GHz.
Extremely powerful masers, associated with active galactic nuclei, are known as megamasers and are up to a million times more powerful than stellar masers.
Terminology
The meaning of the term maser has changed slightly since its introduction. Initially the acronym was universally given as "microwave amplification by stimulated emission of radiation," which described devices which emitted in the microwave region of the electromagnetic spectrum.
The principle and concept of stimulated emission has since been extended to more devices and frequencies. Thus the original acronym is sometimes modified, as suggested by Charles H. Townes,[1] to "molecular amplification by stimulated emission of radiation." Some have asserted that Townes's efforts to extend the acronym in this way were primarily motivated by the desire to increase the importance of his invention, and his reputation in the scientific community.[3]
When the laser was developed, Townes and Schawlow and their colleagues at Bell Labs pushed the use of the termoptical maser, but this was largely abandoned in favor of laser, coined by their rival Gordon Gould.[4] In modern usage, devices that emit in the X-ray through infrared portions of the spectrum are typically calledlasers, and devices that emit in the microwave region and below are commonly called masers, regardless of whether they emit microwaves or other frequencies.
Gould originally proposed distinct names for devices that emit in each portion of the spectrum, includinggrasers (gamma ray lasers), xasers (x-ray lasers), uvasers (ultraviolet lasers), lasers (visible lasers),irasers (infrared lasers), masers (microwave masers), and rasers (RF masers). Most of these terms never caught on, however, and all have now become (apart from in science fiction) obsolete except for maser and laser.
In the early 1960s JPL developed a Maser to provide ultra low noise amplification of S band signals received from deep space probes. This Maser used refrigerated Hydrogen to chill the amplifier to four degrees Kelvin. Amplification was achieved by exciting a ruby comb with a 12 GHz Klystron. In the early days it took days to chill [and remove impurities from] the Hydrogen lines. Refrigeration was two stage with a large Linde unit on the ground and a crosshead compressor within the antenna; final injection was at 3000psi through a six thou inch [micrometer adjustable] entry to the chamber. The whole system noise temperature looking at cold sky [2.7K] was 17 degrees K. This gave such a low noise figure that the Mariner 64 Spacecraft could send pictures of Mars back to Earth even though the spacecraft transmitter was only 15 Watts and the signal received was -169 dbm
摘自：XXXXXXXXXXXXXXXXXXXXXXX/wiki/Maser [i]
[/b]
