Bunch coherence in parametric X-ray radiation

The amplitude of Parametric X-ray radiation emitted coherently by a bunch of electrons crossing a crystal (CPXR) is calculated. When the bunch density is modulated with a longitudinal period close to the X-ray wavelenght, constructive many-electron interferences enhance the intensity by Nb * |F(K)|^2, where Nb is the number of electrons in the bunch, F(K) the bunch form factor and K a specified wave vector. CPXR can be used to test the microbunching in a X-ray free-electron laser.Comment: 6 pages, no figure. Presented at NATO Advanced Research Workshop on Electron-Photon Interaction in Dense Media (Nor Hamberd, Armenia, 25-29 June, 2001

Charge Asymmetry in 1-1000 GeV Electromagnetic Showers and Possibility of Its Measurementnt

For the high energy electromagnetic showers the thickness dependence of a) the development of electron and positron components, b) the difference between the secondary electron and positron numbers, c) the charge asymmetry of high energy electromagnetic showers, as well as d) the spectral distributions of the components at the shower maxima for various energies of primary particle energies,1 - 1000 GeV were investigated employing GEANT Monte Carlo simulation package. Using these simulation results it is discussed the possibility of observation and study of the charge asymmetry with the help of a magnetic spectrometer which is important for the current and future experiments on the detection of radiowaves produced by high energy neutrinos.Comment: TEX file and 4 figure

Gamma Ray Cherenkov-Transition Radiation

The production of gamma-ray Cherenkov-transition radiation (GCTR) by charged particles in the photon energy region 0.8 - 2 MeV is studied theoretically using the results of the recent discovery that in the above mentioned region the dielectric constant or the refraction index of some materials is greater than 1 due to Delbruck scattering on Coulomb field of nuclei. Using the results of the carried out numerical calculations, the possibility of observing GCTR and some of its applications are discussed

Recent and future high energy experiments on QED nonlinear effects

A short review of the experiments on photon elastic scattering and splitting on Coulomb field of nuclei as well as on multiphoton Compton scattering and Breit-Wheeler pair production in strong electromagnetic field is given. Possible new QED nonlinear experiments are discussed

Use of single carbon nanotubes and graphene in particle detectors and beam monitors

After a short review of some physical properties of single carbon nanotubes and graphene layers it is discussed the possibility of construction of new beam particle monitors (BPM), ionization and proportional counters and time projection chambers (TPC). It is shown that in spite of the tested laser and wire BMPs the proposed single nanotube BPMs can provide better measurement of the profile of future electron-positron colliders with very high beam density. The use of single nanotubes as anode wires in proportional counters allows their operation at lower electric fields and to construct multiwire proportional counters (MPC) with better space resolution. It is proposed to construct TPCs using nanotubes and graphene ribbons based on the sharp variation of graphene electrical conduction under the influence of electrostatic potential resulting from the charge deposited by the ionizing particles