The Highly Isotopic Enriched (99.9%), High‐Pure 28Si Single Crystal

We report on the growth of 99,9 % enriched ²⁸Si, dislocation free monocrystals (111‐ and 100‐orientated) with nearly 10 g weight and less than 10¹⁵ foreign atoms/cm³.     

Towards 0.99999 28Si

A new approach for producing high-purity silicon with isotopic enrichment of ²⁸Si isotope is reported. The methods of centrifugal enrichment were modified to obtain the initial gaseous silicon tetrafluoride with a record-breaking enrichment of 0.99999664(11) with respect to ²⁸Si. The effective conversion of silicon tetrafluoride into elementary silicon with minimal isotopic dilution was achieved in an electron cyclotron resonance discharge plasma, sustained by gyrotron microwave radiation with a frequency of 24 GHz. We have experimentally demonstrated the deposition of the layers of microcrystalline ²⁸Si with enrichment of 0.999986 ± 0.000003, which is the best result at the present time.     

Deep inelastic scattering with tagged photons at HERA

We calculate cross-sections for neutral current deep inelastic scattering at HERA with photon tagging. Both, the exact lowest-order cross-section and a leading logarithmic approximation of next-order corrections are calculated. The latter amounts to less than 20% in a large kinematical range. The integrations are performed numerically but without relying on Monte Carlo methods.     

The Bohm criterion and boundary conditions for a multicomponentsystem

In the asymptotic limit λ_D→O (small Debye length) the boundary layer problem of a plasma is split up into the separate problems of a: quasineutral presheath and a collision free planar sheath. The formation of a stationary sheath requires that the ions fulfil a sheath condition (“Bohm criterion”). In this paper, the boundary layer problem of a multicomponent system is investigated. Both in the frames of a hydrodynamic and of a kinetic theory, a generalized sheath condition is derived accounting for various ion components and arbitrary electron- and ion distributions. It is shown that the sheath condition is usually fulfilled marginally (in the equality form) and provides a boundary condition for the plasma analysis     

PECVD growth of crystalline silicon from its tetrafluoride

The process of plasma chemical deposition of silicon from inductively coupled plasma of the mixture of high‐purity SiF₄ and H₂ sustained by RF discharge at 13.56 MHz in amount sufficient for subsequent growth of crystal by Czochralski method was investigated. The structure and impurity content of the produced layers as well as of the grown crystal have been studied (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Multi-crystalline silicon as active medium for terahertz intracenter lasers

Stimulated emission at terahertz frequencies has been obtained from multi-crystalline silicon doped by phosphor under optical excitation by a mid-infrared laser. The silicon samples consist of grains with a characteristic size distribution in the range from 50 to 500 μm. The maximum operation temperature of the laser made from multi-crystalline silicon is 6 K less than that of monocrystalline lasers and the maximum output power is three times less while its laser threshold is only slightly higher and the emission frequency is the same. These effects are attributed to internal strain and enhanced phonon scattering induced by grain boundaries.     

Deep inelastic muon scattering as a test of gauge theories

Different asymmetries in polarized lepton scattering are shown to be remarkably dependent on the valence quark and lepton multiplet structure in currently discussed gauge theories. Therefore deep inelastic muon experiments at SPS energies can contribute significantly to the investigation of neutral currents.     

Study on low-energy positron polarimetry

A polarised positron source has been proposed for the design of the international linear collider (ILC). In order to optimise the positron beam, a measurement of its degree of polarisation close to the positron creation point is desired. In this contribution, methods for determining the positron polarisation at low energies are reviewed. A newly developed polarisation extension to GEANT4 will provide the basis for further polarimeter investigations.