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The differential cross section in the transverse momentum Q and a total cross section of (31 ± 4) mb for the coherent dissociation of a 3-A-GeV/c 7 Li nucleus through the 3 H+ 4 He channel have been measured on emulsion nuclei. The observed Q dependence of the cross section is explained by the predominant supposition of the nuclear diffraction patterns on light (C, N, O) and heavy (Br, Ag) emulsion nuclei. The contributions to the cross section from nuclear diffraction (Q ≤ 400 MeV/c) and Coulomb (Q ≤ 50 MeV/c) dissociations are calculated to be 40.7 and 4 mb, respectively. The properties of the nuclei and mechanisms of the reactions induced by the Coulomb and nuclear interactions in nucleus-nucleus collisions have been studied for more than five decades [1-4]. These investigations have been recently expanded to the relativistic energy range [5-8].It is known that the nuclear diffraction mechanism of the reactions at low momentum transfers Q (similar to optical diffraction), which was predicted as early as the 1950s [9][10][11][12], becomes significant at energies of about hundreds of MeVs and higher along with the Coulomb interaction. Diffraction is characterized by the observed oscillations of the cross sections for the elastic scattering of particles and nuclei, dσ/dQ, with the main maximum at small angles ϑ λ/R, where λ is the de Broglie wavelength of the incident particle and R is the radius of the nuclear interaction region. It is also known [12] that the diffraction mechanism can induce the coherent dissociation of the incident nucleus (without the excitation of the target nucleus) and the production of particles. The dissociation of the 12 C nucleus into three α particles was observed at relativistic energies [13,14]. However, the direct observation of the diffraction pattern with the counter technique (measurement of dσ/dQ) in the nuclear dissociation remains a sufficiently complex problem. The energy spectra of the charged particles at given angles [15,16] are normally used in such experiments.Among numerous reactions accompanying the collisions of relativistic nuclei (multifragmentation, meson production), we take a comparatively simple channel of coherent (elastic) dissociation of the 7 Li nucleus (λ 0.01 fm), which corresponds to the twocluster structure of the 7 Li nucleus and is convenient for the application of the developed theoretical approaches to the description of such reactions.The cross section dσ/dQ for the elastic dissociation of the 7 Li nucleus is measured in the experiment in order to analyze the diffraction pattern of the process and to determine the contribution from the electromagnetic dissociation. According to previous nuclear emulsion measurements [8], the chosen reaction is characterized by very small nucleus emission angles and correspondingly low values Q ≤ 0.45 GeV/c; under these conditions, the simultaneous manifestation of the Coulomb and nuclear diffraction mechanisms of the process can be expected [5]. The Q regions of the contributions from the Coulomb and nuclear intera...

In a track nuclear photoemulsion exposed to a beamof 7 Li nuclei accelerated to a momentum of 3 GeV/c per nucleon at the synchrophasotron of the Joint Institute for Nuclear Research (JINR, Dubna), 13 events in which 7 Li nuclei interacting with protons break up into 3 H and 4 He fragments were detected among 3730 inelastic-interaction events. For this fragmentation channel, the cross section was found to be 8±2 mb. The average value of the fragment total transverse momentum was 214±5 MeV/c. This value exceedsmarkedly the average value of the transverse-momentumtransfer in the coherent dissociation of 7 Li nuclei on track-emulsion nuclei (166 ± 5 MeV/c). The recoilproton transverse momentum was on average 98% of the total proton momentum. The longitudinalmomentum distribution of protons was characterized by a variance of 16 MeV/c and a mean value of 37 ± 2 MeV/c.

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Lebedev Physical Institute electron synchrotron to the maximum energy up to 1.3 GeV is under operation since the mid of seventieth. It is weak focusing machine consisting of four 90-degree sectors with the radii 4 m and four straight sections between them. The microtron with the energy 7 MeV and pulse current 50 mA is used for injection into the main accelerator. The average intensity of the synchrotron is 0.1 µA, repetition rate being equal to 50 Hz. Extracted electron beam and bremsstrahlung photons are used for the experiments in the field of nuclear and elementary particles physics. The most remarkable achievement at this machine is the discovery of creation and decay of η-mesic nuclei arising from reaction of photon of energy 1 GeV with carbon nuclei, having been made at the end of 90th. Up to now computer was not used for synchrotron parameters monitoring and control. We expect that automation might improve significantly the main parameters of the accelerator as well as much better time dependent stability of the electron energy and intensity. The paper is the extraction from conception design of accelerator automation project. We plan to use the concept and experience acquired during development of the Lebedev Physical Institute Radiation Complex. The basis of this concept is the flexible computer interface at the level of executable that allows build any desirable representation of acquired data as well as controls to affect the accelerator systems. Necessary upgrade of the existing computer code will be undertaken to meet additional requirements of distributed control and measurements.