The multiyear work on the creation of a new plant for proton beam cooling by electrons for the accelerating complex COSY (Cooler synchrotron) at the Research Center in Julich, Germany, was completed at the Budker Institute of Nuclear Physics (INP) of the Siberian Branch of the Russian Academy of Sciences. With the service voltage of 2 mln V, the plant will make it possible to carry out this process at a record speed. This opens up new possibilities for conducting of unique experiments on scattering of polarized protons on internal targets, studies of nuclear forces and filling of the gaps in experimental data on the nucleon structure. Vasily Parkhomchuk, one of the developers of this method, director of the said institute and RAS Corresponding Member told Alexander Nadtochy, a correspondent of the Nauka v Sibiri (Science in Siberia) newspaper about this innovative technology.

He noted that the revolutionary idea of electron cooling of heavy particles belongs to Acad. Gersh Budker (1918-1977), founder of the INP. In 1965 he suggested that a "cold" electron bunch should be let through a "hot" proton beam having the same speed and lower temperature, and moving quickly in vacuum. In compliance with the Coulomb law (discovered by the French physicist Charles Coulomb in 1785), which describes interaction forces of electrical charges, the intensive heat exchange takes place between "hot" and "cold" particles, resulting in cooling and compression of heavy proton beams, which is required by the experimenter.

Needless to say that the Siberian method of collisional heat exchange is not the only one but it is very efficient.

The alternative stochastic method is rather complex: the hot particle "is tapped" with resistance from edges, making it oscillate with lower amplitude. The method is not quite convenient, as it requires observing each of them, not as a whole beam. It requires sophisticated tracking equipment, which makes the technology more expensive than that suggested by the INP specialists.

However, despite the apparent advantages the Budker innovative method had a long run to the consumer. Only seven years later, in 1972, at the laboratory headed by Academician Alexander Skrinsky, a group of young physicists under Nikolai Dikansky (Academician from 2011) decided to create, figuratively speaking, a refrigerator for protons. In March 1973, they designed a NAP-M antiproton accumulator, and in May of the next year they conducted the first experiments on beam cooling. It took them almost a year of hard work before they scored a success. According to Parkhomchuk, until then there were few people outside the INP who believed in him, as to realize his bold idea it was required to achieve a high precision of combining two bunches of charged particles moving at a near-light speed but the Siberian physicists managed to succeed.

In August 1974, American physicist Robert Wilson wrote to Budker: "...Your preliminary results in extinction of betatron oscillations of protons in interaction with electrons, i.e. proton cooling, are undoubtedly the most remarkable event among many considerable achievements of the INP. If your preliminary results turn out to be true, it will become one of the most substantial achievements in accelerator technology."

The words of the future Nobel Prize-winner (1978) turned out to be prophetic, as the results were really remarkable. Moreover, they excited the minds of scientists at other laboratories of the world. Parkhomchuk pointed out: "After the first successful experiments carried out at the INP, many research centers got down to check this method: the Americans-at the Fermi National Accelerator Laboratory, the Europeans-at the CERN*, the Japanese-at the High Energy Accelerator Research Organization (KEK), and since then electron cooling plants operate on many accelerators. The German experts visited the USSR to study this method and later on they built a good plant at the Heavy Ion Research Center (GSI) in Darmstadt. But they ordered another plant for their SIS-18 synchrotron at the INP, apparently deciding that the Siberian specialists understood peculiarities of electron cooling better than they did. This plant is operating successfully since 1989. By the way, when the INP delegation visited the GSI (2005), the plant cooled beams of ruthenium ions (Ruthenia is an ancient name of Rus), an element discovered in our country in 1844 by the German scientist and professor of the Kazan University Karl Klauss."

And only in 2002, when the method of electron cooling of heavy particles became predominant in the world, a group of developers (Acad. Alexander Skrinsky, RAS corresponding members Vasily Parkhomchuk, Nikolai Dikansky and Igor Meshkov, Dmitry Pestrikov, Dr. Sc. (Phys. & Math.), Rustam Salimov and Boris Sukhina Drs Sc. (Tech.)), was awarded the State Prize of the Russian Federation in the field of science and technology. Gersh Budker was awarded posthumously.

Today this method is well developed theoretically, studied and mastered. It became a perfect device for cooling of actually all elements of the Mendeleev period-

* CERN--European Organization for Nuclear Research (Switzerland).--Ed.

Science in Russia, No.4, 2012

ic system. Only in 1988-1992 nine electron refrigerators appeared at different research centers of the world. The INP holds a leading position among their manufacturers, and about 80 percent of such equipment is produced in Novosibirsk.

In recent years the INP specialists worked out a project of an electron cooling plant with electron-beam energy of 350 keV, easily modernized to 1.5 MeV. Based on the technologies developed and tried at the institute, the plant consists of solenoid, magnetic system of beam transportation, electron gun, collector and high-voltage feed block.

The Institute of Modern Physics (Lanzhou, China) got interested in this plant. It concluded a contract with the INP for production of two plants, which were manufactured and delivered to China in early 2000s.

It should be noted that the works of the Siberian physicists were used in the creation of the Large Hadron Collider*, a circular accelerator and accumulator of colliding proton beams, which was put into operation in 2009 at the CERN. The point is that the heavy particles circulating in such systems are too "hot" (with a wide range of kinetic energy of protons due to their transverse movement). Magnetic lenses localize their "spreading" at the expense of an increase of transverse oscillations. Budker's idea of electron cooling helped cope with this problem. In one of the linear sections, next to a proton beam, a cold bunch of electrons is "injected", which moves at about the same speed. For some time they intermix and move together, besides, protons are cooled owing to collisions with electrons, and then their routes again separate in the magnetic field.

The electronic refrigerator manufactured at the INP and installed on the LEIR low energy ion accumulator of the Large Hadron Collider, stressed Parkhomchuk, became a key element in the experiment, which made it possible in late 2010 to observe a new physical phenomenon, i.e. suppression of quark-gluon jets (matter emerging in the course of ion interaction).

Currently, a similar plant is being prepared for the Julich Research Center, which, apart from nuclear physics, studies problems of high-temperature plasma, controlled thermonuclear fusion and synchrotron radiation and carries out interdisciplinary research in public health, power engineering, environment and information technologies. The agreement on scientific-technical cooperation between the INP and the Julich Research Center was signed in May 2011. But the work on the first plant for the German partners started more than two years ago. The first "strength" tests of the plant, i.e. trial "injection" of an electron beam into its magnetic system, were conducted in November 2011. After the final experiments are over, the finished heavy-tonnage item will be dismantled and sent to Germany for electron cooling of intense proton beams on the COSY accumulator. According to Parkhomchuk, "connection of our plant to a good accelerator will turn it to a very good accelerator". Thus, it offers an opportunity to fill up some gaps in the modern theory of elementary particle physics.

* See: L. Smirnova, "The 21st Century Megaproject", Science in Russia, No. 5, 2009.--Ed

A. Nadtochy, The Electromagnetic Sonnet, "Nauka v Sibiri" newspaper, No. 5, 2012