FREE ELECTRON LASERS

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Скачать бесплатно! Научная работа на тему FREE ELECTRON LASERS. Аудитория: ученые, педагоги, деятели науки, работники образования, студенты (18-50). Minsk, Belarus. Research paper. Agreement.

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Опубликовано в библиотеке: 2021-08-29
Источник: Science in Russia, №4, 2010, C.53-54

Since its invention in the 1960s the laser came to be called "a device seeking after solvable problems". Today it is used in different and at times unexpected fields, namely, from vision correction and control of transport vehicles to space flights and thermonuclear fusion. Nevertheless, scientists are developing novel quantum generator types. One of them, a free electron laser, has been developed at the Budker Institute of Nuclear Physics of the RAS Siberian Branch (Novosibirsk)*. Academician Gennady Kulipanov, Deputy Director of this Institute and one of the project managers, told Vasily Yanchilin, a Poisk newspaper correspondent, about the laser's design and its fields of application.

 

He says man is using a whole spectrum of electromagnetic waves in his activity, that is from hard gamma radiation to radio frequencies. The millimeter and submil-limeter regions remained a blind spot for a long time. Nobel Prizewinners Academicians Alexander Prokhorov and Vitaly Ginzburg had been studying this promising field long before lasers were invented. Prokhorov investigated coherent synchrotron radiation at the Lebedev Physical Institute of the national Academy of Sciences back in the 1950s. In 1947 Ginzburg published a paper on generation of millimeter radiation by using electron beams and periodic deflecting structures. These materials served as a basis for an undulator (from the Latin unda, or wave) he invented, a device where fields are created to make an electron beam vary in a certain mode. In so doing, Ginzburg came close to the idea of creation of a free-electron laser with the undulator as its main component. This idea was implemented by researchers of the Institute of Nuclear Physics, who started the first stage of an innovative setup under the direction of Nikolai Vino-kurov, Dr. Sc. (Phys. & Math.) at the Siberian Center of Photochemical Research of the Siberian Branch of the Russian Academy of Sciences in 2003.

 

This setup has a lot of advantages. A conventional laser has a fixed (or variable within fairly narrow limits) wavelength of radiation. When an engineer uses such a laser, he has to adjust to this spectrum, which restricts both the area of research and the choice of facilities. As to the free electron laser, it can change the emitted light frequency over a wide range due to the capability of correcting the parameters of an electron beam moving along the tortuous trajectory in the undulator. The large sizes of such setups that cannot be used as a desk device are their only disadvantage. For example, the laser developed in Novosibirsk and operated within the 120-200 micron wavelength range occupies more than 100 m2, and its power is 500 W. There is no other source of coherent submillime-ter radiation like that elsewhere in the world.

 

From the very beginning specialists were all set to develop a powerful apparatus. For this purpose they had to calculate and design not just a particle accelerator but a device capable of energy recuperation, or the recuperator. For example, a trolley operates on a similar principle, i.e. it consumes electric power when moving uphill and recuperates it when moving downhill. The same

 

 

See: V. Parmon, "Controlled Conversions", Science in Russia, No. 5, 2007.-Ed.

 
стр. 53

 

approach allows, on one hand, achieving a radiation maximum at low power consumption and, on the other, reducing the radiation hazard, that is the personnel can enter the lab premises immediately after the electron gun has been switched off.

 

The recuperator of the Siberian Center of Photochemical Research is double-turn, i.e. each particle performs two turns within. The generated radiation is directed by a special optical path to experimental stations, six in number. Other Novosibirsk institutions also took part in this project, among them the Institute of Scientific Instrument-Making, the Institute of Semiconductors, and the Institute of Solid State Chemistry.

 

According to Acad. Kulipanov, physicists are the main users of coherent submillimeter radiation. Today 10 research teams are involved with this problem, not at the Siberian Branch of the Russian Academy of Sciences alone. Colleagues of Moscow State University are also conducting experiments on surface waves in the millimeter range.

 

Free electron laser is requisite to biologists. The fact is that microwave radiation, as if it were a knife, cuts hydrogen bonds of living objects, for example, DNA, but does not destroy them. The laser effect on cells is also of interest. According to one hypothesis, the inner clock of elementary units of the organism operates just in this spectral range.

 

The Novosibirsk scientists concern themselves also with such a "trendy" direction as research in metamaterials, i.e. artificial composites possessing a negative refractive index and quite unusual properties. They become invisible under the action of radiation within a certain range of frequencies. Such materials are already well studied in the radio spectrum. Next, the microwave range is to be explored. The Laboratory of Physics and Technology involved with three-dimensional nanostructures at the Institute of Semiconductor Physics of the Siberian Branch of the Russian Academy of Sciences offers interesting conceptual designs in this area.

 

Chemists and specialists in mineralogy, aerodynamics and atmospherical optics, who work at this setup, are also in for new discoveries. In a word, by creating a powerful free electron laser the Budker Institute of Nuclear Physics has opened up new avenues in research.

 

V. Yanchilin, Freedom to Electrons!, "Poisk", February 19, 2010

 

Prepared by Marina KHALIZEVA

 

 


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© V. Yanchilin () Источник: Science in Russia, №4, 2010, C.53-54

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