The structure of a composite photon-electron spectrometer based on NaI(Tl) crystals and plastic scintillators is described. A spectrometer calibration under a beam of secondary electrons with an energy of 50-150 MeV is described. At a work-load of N similar to 10(3) Hz the energy resolution is sigma/E = 0.03E(-0.25), and the time resolution is similar to 8 nsec.

The channeling of ultrahigh energy positrons both in bent and straight crystals can serve as an effective source of hard photons. The presence in the channel of the strong inhomogeneous electrical field gives rise to a number of interesting peculiarities of the motion of the channeling particles. The radiative separation of particles depending on spin orientation with respect to the plane of motion and radiative polarization can make it possible to obtain by means of bent crystals a positron beam with a degree of polarization about 10 to 20%. Because of availability of the ultrahigh energy positron beams such experiments can be carried out nowadays.

Slow extraction system of the Synchrotron “Pakhra” contains two pulsed septum magnets. They are located inside the synchrotron vacuum chamber. Both the soft and the hard septum magnets have similar mechanical construction. They consist of four magnetic blocks split by three copper brackets. The dimensions of the magnetic gap are 1.2 cm height and 3.6 cm width. The soft septum thickness is 0.1 cm. The septum is cooled indirectly by the copper brackets. The fringing field is less than 2% of the field in the core gap. To generate the maximum field of 0.08 T in an one-turn winding 800 A current is required. The second septum is water cooled and it is 0.5 cm thick. The field strength of this magnet can be raised up to 0.4 T at 4000 A. The septa are fed by current pulsers. The leading edge of the pulses is 1 msec and their flat peaks range from 2 msec to 3 msec. Repetition rate is 50 Hz

The radiation of electrons in magnets with linear gaps is investigated. Typical spatial distribution of the magnetic field is discussed. The characteristic parametrization of this distribution is given. The law of the electron motion in such a field and the form of the electromagnetic field pulses arising at this motion is considered. The domain of the radiation generation is investigated. It is shown that in inhomogeneous edge field the radiation pulses are formed in the region with appreciable longitudinal dimension. Results of the numerical calculation of the angular and spectral distributions are given and the comparison with experimental data is carried out. Due to their higher intensity in the more longer wavelength spectral region in comparison with the standard synchrotron radiation from bending magnet this radiation can be useful in solving a number of applied problems.

The method and the code described have been used for calculations of the closed orbit in the Pakchra synchrotron. It was found that for determining the closed orbit to an accuracy of 10/sup -2/ cm only two or three iteration steps are needed. The code used includes several orbit correction algorithms. It enables calculations for real magnet lattices including various corrections.<>

The phase trajectories close to the parametric resonance and to the nonlinear resonances of third and fourth order, which play an important role in cyclic accelerator particle dynamics, are investigated. The problem is reduced to the construction of phase trajectories that are third- or fourth-order curves and the determination of the mode of motion in the vicinity of the resonance. The phase trajectory build-up is performed using Klein's perturbation method.<>

The review sets forth the main results of theoretical and experimental studies of the radiation emitted by relativistic charged particles in undulators. The physical basis of the action of undulators is described. The main properties of undulator radiation and their relation to the trajectory of the particles in the undulator are discussed. Quantitative relations are given for the spectral, angular, and polarization characteristics of the radiation by an individual particle. The influence of the electron-beam parameters on the properties of the radiation are considered. The relation between the size of the diaphragm and the spectral characteristics of the radiation selected by it is analyzed. Some fundamental aspects and the results of recent experiments on generation of coherent undulator radiation are presented, including radiation from free electron lasers. Various types and features of undulators are described, and also characteristics of existing sources of undulator radiation in synchrotrons and storage rings. Several methods of experimental investigation and results obtained therein are discussed.

This article presents results of a study of the dynamics of the electron-beam cross section in the ''Pakhra'' synchrotron with electron acceleration to 670 MeV. The observed dependence of the rms amplitudes of vertical oscillations on time in one acceleration cycle is in good agreement with radiation-damping theory. The time dependence of the horizontal beam dimension is in satisfactory agreement with theory, assuming that the initial dimension is dependent only on synchrotron oscillations.

The characteristics of particle radiation in different undulators are qualitatively compared. Features peculiar to particle radiation in crystals (natural undulators) are discussed. The effects of particle energy and initial entry conditions on particle oscillation frequency are considered. The effect of radiation friction and multiple scattering on the radiation parameters is investigated. The accuracy of a description of channelled electron emission by means of the averaged potential is checked. A criterion is suggested for checking the applicability of classic electrodynamics to a particle radiating in a crystal.

An undulatory character of the motion of charged particles is realized in magnetic undulators, at channeling in crystals, in the field of electromagnetic waves and in some other cases. In these systems the spectral-angular and polarization properties of radiation are characterized by common features. In the present work results of an experimental study of properties of the undulator radiation in the optical wavelength range are reported. Relation between the radiation wavelength and the angle of observation has been studied. Azimuth distribution of radiation at a fixed wavelength for various electron energies has been measured. Spectra of the undulator radiation have been obtained. Collimation effect upon the radiation spectra has been analysed. Experiments proved the possibility of separation of a narrow spectral range of undulator radiation by collimation. All experimental results are in a good agreement with the theoretical predictions.

Том 128, вып. 1 УСПЕХИ ФИЗИЧЕСКИХ НАУК СОВЕЩАНИЯ И КОНФЕРЕНЦИИ 621.384.612(048)НАУЧНАЯ СЕССИЯ ОТДЕЛЕНИЯ ОБЩЕЙ ФИЗИКИ И АСТРОНОМИИ АКАДЕМИИ НАУК СССР (29-30 ноября 1978 г.) 29 и 30 ноября 1978 г. в Физическом институте имени П. Н. Лебедева АН СССР состоялась совместная научная сессия Отделения общей физики и астрономии и Отделения ядерной физики АН СССР.На сессии были заслушаны доклады: 13. ΙΟ.Μ. К а г а н.Когерентное возбуждение изомерных состояний ядер в кристалле синхротронным излучением.4. Α. Η. Α ρ τ е м ь е в, В. А. К а б а н н и к, Ю. Н. К а з а к о в, Г. Н. К улипанов, Е.А.Мелешко, В.В.Скляревский, А. Н. С к ρ и н с к и й, Е. П. С τ е π а н о в, В. Б. X л е с τ о в, А. И. Ч е ч и н.Эксперимент по возбуждению мёссбауэровского уровня 57 Fe с помощью синхротронного излучения.5. М. А. Мокульский.Применение синхротронного излучения для рентгеновских дифракционных исследований биополимеров.6. А. А. В а з и н а.Исследования динамики структурных превращений в биомолекулярных системах методами скоростной дифрактометрии с использованием синхротронного излучения.7. В. В. Μ и χ а й л и н.Синхротронное излучение в спектроскопии твердого тела.8. С. П.Капица.Источники синхротронного излучения в настоящем и будущем.Ниже публикуется краткое содержание пяти докладов.