摘要:

Some recent results from CERN-experiments are described. The paper discusses the emission of radiation from GeV electrons and positrons traversing thin Si and Ge crystals. The special features of radiation emission and pair production in the multi GeV region is discussed. Dramatic energy losses are found for well aligned electrons. The combined process of radiation emission and pair production result in shower formation which along crystalline directions is strongly enhanced—leading to radiation lengths that are (20–50) times shorter than those for amorphous materials. Strong crystalline fields might turn out to be the best way to extract TeV-beams from coming accelerators and to determine accurately the origin of GeV-TeV gamma rays from the universe.

ISSN:1042-0150    

DOI:10.1080/10420159308225477

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The experimental results of the development of electromagnetic showers induced by 28 GeV electrons in aligned tungsten crystals with thicknesses 0.07,0.3,1.0mm are presented. At this energy of electrons the “constant strong field” effect starts to show and the development of showers in aligned crystals is distinguished from the one in an amorphous substance.

ISSN:1042-0150    

DOI:10.1080/10420159308225478

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Known processes in the interaction of an energetic beam of particles with an aligned crystal are reviewed briefly. The use of energy-momentum dispersion diagrams facilitated their descriptions and helped identify new interesting processes for further studies.

ISSN:1042-0150    

DOI:10.1080/10420159308225479

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The photo reflectance spectrum in a single quantum well structure was investigated theoretically. Numerical results are presented for 100 Å and 300 Å GaAs wells.

ISSN:1042-0150    

DOI:10.1080/10420159308225480

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A theory is considered which allows to describe the influence of radiation and inelastic collisions on the internal quantum mechanical state of a projectile in a solid. As a particular consequence of this theory the elimination of infrared catastrophe is presented.

ISSN:1042-0150    

DOI:10.1080/10420159308225481

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Earlier published theoretical models for MeV electrons are generalized in this paper. Different theoretical predictions for planar channeling and accompanying electromagnetic radiation in thick crystals are presented. A comparative analysis of theoretical and experimental spectra of photon radiation is given. Thickness dependences of channeling quantum state populations, radiation line broadening and photon flux intensities are obtained. The existence of planar electron channeling at 54 MeV in a silicon single crystal with a thickness of several millimetres is shown.

ISSN:1042-0150    

DOI:10.1080/10420159308225482

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Radiation spectra of high-energy electrons incident at small angles relative to crystallographic planes of a CdS crystal are theoretically obtained. A comparison of calculations with the earlier experimental data is carried out taking into account the photon multiplicity.

ISSN:1042-0150    

DOI:10.1080/10420159308225483

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Recent progress in the evaluation of higher-order corrections to the continuum-model description of channeling radiation from MeV electrons is discussed. The most important corrections are found from thermal scattering, and to second order in a time-dependent perturbation expansion, a ‘phonon Lamb shift’ is obtained, caused by emission and absorption of virtual phonons. It turns out that the third-order thermal correction must be included since it contains a shift which is of the same magnitude or larger. The possible significance of the second-order level shifts due to electronic excitations is also considered.

ISSN:1042-0150    

DOI:10.1080/10420159308225484

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The influence of multiple scattering on the electron channeling radiation line widths has been determined by solution of a Bethe-Salpeter-equation. a good agreement with experimental data of (110) planar channeling in silicon was found.

ISSN:1042-0150    

DOI:10.1080/10420159308225485

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Channeling radiation has been used for excitation of the 15.1 MeV resonance gamma level of a12C nucleus. Multiplicity effects occuring during radiation emission from (100) silicon crystal at 900 MeV electron incidence were considered.

ISSN:1042-0150    

DOI:10.1080/10420159308225486

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor