Yerevan Physics Institute has an electron synchrotron (ARUS) with energy of up to 6 GeV, which was put in operation in 1967.
Despite of numerous carried out or planned researches in the USA (Cambridge – 5 GeV, Cornel – 9 GeV, SLAC – 20 GeV), in Germany (DESY – 6 GeV), in England (NINA – 4 GeV) at that time, physicists of YerPhI succeeded to receive a number of important results, allowed to promote in understanding of hadron and nuclei structure and fundamental properties of elementary particles interaction.
During 1970-1991 years the Yerevan synchrotron operated productively and many scientific results have been obtained in the energies range up to 4,5 GeV, including: the study of hadronic properties of photons in reaction of π- meson photoproduction on nuclei, structures of nucleon resonances in multi-polarization experiments, structure and characteristics of a nuclear matter, study of properties of X-ray transition radiation and radiation of relativistic electrons at channeling in monocrystals etc ( see Appendix 1).
In 1980, academician H.Vartapetian ( Deputy Director of YerPhI in 1974-1993) with group of his colleagues has been awarded by State prize of Arm. SSR for outstanding contribution and remarkable scientific results obtained at YerPhI’s synchrotron. .
The YerPhI experimental physics program included following researches: study of
· properties and structures of baryons ( nucleons and nucleon resonances)
· few nucleon systems properties
· excited nuclear systems properties
· nuclear matter in short distance
electron interaction with crystals
and methodical studies
Since 1991 because of an energy crisis in Armenia the accelerator has been stopped. However, its maintenance continues till now and short- time experiments are periodically performed.
The reputation of the Institute as the nuclear-physics and accelerator center during the most difficult years of 1991-1996 let us to preserve and even develop international collaborations with scientific centers of USA, Germany, Switzerland and elsewhere, what, in particular, play the essential role in getting different grants.
Brief summary of scientific results for period 1970-1991
The main achievements of the YerPhI in high energy experimental particle and nuclear physics obtained on Yerevan synchrotron for period 1970-1991 years:
The electromagnetic radius of proton and deuteron were measured using the 4.5 GeV electron elastic scattering, that showed proper coincidence with most precise measurements and supplemented world data bases [1,2].
From the measurements of single π-meson photoproduction on nuclei in the wide energy range it was shown that simplest version of vector dominance model (VMD) is unable to describe hadronic properties of photons .
To check the quark structure of η – meson the total cross section of η – meson – nucleon interaction was determined from the measurements of incoherent η – photoproduction on nuclei .
A quasi-monochromatic photon beams with 0.5-2.0 GeV peak energy and record degree of polarization was obtained at YerPhI. This fact presently provides the priority of the YerPhI in the research of spin correlations in photoproduction on nucleons and nuclei .
In the π- and η –meson photoproduction on nucleon the structure of nucleon resonances in multipolarized experiments (beam, target and recoil nucleon polarization) was investigated. These data together with other results allowed to determine electromagnetic constants of nucleon resonances and check the predictions of quark models [6-11].
The nucleon properties in nuclei was studied in the inclusive (e,e') and exclusive (e,e'p) scattering measurements [12,13].
The structure of deuteron and quasideuteron was studied in polarization and multipolarization experiments of photodesintegration [14,15].
In the studies of high energy (up to about hundreds MeV) photo- and electro-excitation of nuclei (with further fragmentation) it was shown possible production of very heated clusters as a radiation sources of the nuclear fragments [17-21].
The new intensive radiation of relativistic electrons was observed at channeling regime in the monocrystals, which can be useful for fundamental and applied research. The anoter new type of extremely monochromatic (δω/ω ≈10-3) radiation – so called parametric X-radiation (PXR)- was obtained and studied in various conditions [22,23].
The phenomenon and properties of X-ray transition radiation, which was predicted in theory at YerPhI, were systematically studied. These results are well known and are used worldwide for ultrarelativistic particle detection [24-27].
Various modifications of scintillator, gaseous, porous and other type detectors were developed and used in the experiments on photo- and electro-production[28,29].
As an achievement we can mention the experiment, that had been performed in our underground laboratory together with ITEP (Moscow), in which the first observation of two-neutrino double beta decay of 76Ge was made, and the most stringent limit (for that time) on half-life of neutrinoless double beta-decay in this germanium isotope was set. It allowed us to estimate the lowest upper limit for Majorana mass of neutrino .