Chemical etching of sapphire

The results on etching of sapphire substrates with different orientation are discussed. High temperature etching in hydrogen stream and etching in the mixture of H₃PO₄ and H₂SO₄ were used in experiments. The relation of etching rates for different sapphire orientations were established in both cases. The conditions of nonselective etching were determined.     

The Growth Kinetics and Surface Morphology of GaN Epitaxial Layers on Sapphire

The growth kinetics of GaN on Sapphire was analyed on the base of some experimental data such as: the growth rate temperature depandence, on the base of some experimental data such as: the growth rate temperature dependence, the grwoth rate dependence on the gas flow velocity, the growth rate depandence on the crystallographic and spatial orientation of the substrate. The limiting stage of the epitaxy process was established at different growth conditions. The morphology of GaN epitaxial layers obtained at these conditions is described.     

Determination of the composition and content of pulsed cluster beams from time-of-flight mass spectra of cluster fragments

The properties of a superconducting flux quantum bit (qubit) in the quasidispersive mode, where the frequency of a probe signal is lower than the qubit excitation frequency but is close to it, have been experimentally studied. It has been shown that all parameters of the qubit inductively coupled to a coplanar resonator can be determined at the single-frequency excitation from the analysis of the frequency responses of the transmission of the probe signal at the output of this resonator. Under the additional excitation of the qubit by the signal at the second harmonic of the cavity, resonance dips have been observed because of resonance between the probe signal and induced Rabi splitting. It has been shown that the positions of these dips are in good agreement with the parameters of the qubit that are obtained by analyzing the amplitude–frequency response within the width of the fundamental resonance frequency.     

Selective excitation of vibrational states by shaping of light-induced potentials

In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays. As an example, selective population transfer is demonstrated for a three-state model of the sodium dimer.     

A monopole mass filter with a hyperbolic V-shaped electrode

In this article we compare the classical monopole mass filter of von Zahn and the monopole mass filter with a hyperbolic V-shaped electrode. The experimental results and those of computer simulation for both mass spectrometers are presented. We show that the replacement of a conventional 90 degrees V-shaped electrode by an electrode with a hyperbolic profile substantially improves the peak shape of any given mass, and increases the mass resolution by a factor of 3-4 and the abundance sensitivity by a factor of 100. The potential of high analytical performance combined with electroforming techniques for electrode manufacture indicate future practical uses of such instruments. Copyright 1999 John Wiley & Sons, Ltd.     

A three body approach to study the structural properties of 2-n halo nuclei and the search for Efimov states

The discovery of neutron rich isotopes of the lightest elements on the neutron drip line exhibiting a halo structure has opened up new vistas in research activities. The novel structural features associated with the halo phenomena have been the subject for extensive theoretical and experimental investigations in recent times. In this talk, I propose to present a broad overview of the recent developments in this field, bringing out the striking features which show that a large number oflight nuclei near the neutron drip line are characterized by a clear separation between a ‘normal’ core nucleus and a loosely bound low density veil of neutrons. Specifically, the two neutron halos offer a natural premises, from a theoretical standpoint, to employ three body techniques for studying their detailed structural properties. A considerable part of the talk will be devoted to report and highlight the results on a number of light halo nuclei such as ¹¹Li, ¹¹Be, ¹⁹B and ²²C on which we have been carrying out investigations employing a simple but realistic three body model. These three body systems which have been termed as ‘Borromean’ (i.e while three body systems are bound, the corresponding binary subsystems on the other hand are unbound) are characterized by large spacial extension and very low separation energy of the neutron. They are, therefore, ideally suited for exploring the possibility of the existence of Efimov states in two neutron halo nuclei. We have recently carried out the three body analyses to predict the possibility of the occurrence of such states on which experimental work at various laboratories is underway.     

Low-frequency Raman scattering in a polycrystalline C60 film: The role of orientational disorder

Low-frequency Raman scattering in the orientationally disordered phase of a polycrystalline C₆₀ film is investigated. By analogy with disordered media (glasses), the low-frequency Raman spectra are interpreted in terms of light scattering by localized vibrational states.     

The superconducting magnet system with a cryocooler for the ion source Decris-SC

A superconducting magnet system (SMS) for the multicharged ion source DECRIS-SC was designed and manufactured at the Joint Institute for Nuclear Research. Successful tests of the SMS were conducted in late 2003 and early 2004. The peculiarities of this system are stipulated by the use of a cryocooler 1 W in power for the cryostating of the magnet and also by the special configuration of the magnetic field demanded for the source of ions. Four coils ensure the induction of a magnetic field on the axes of the source of up to 3 T (the stopper ratio of ～6), which considerably extends the possibilities of the ion source from the point of view of producing intense highly charged ion beams. The problem of compensating the large forces of interaction between the coils and surrounding iron yoke in this magnet has been successfully solved, and a reliable suspension of the magnet in a cryostat realized. To compound the windings, which work in vacuum at indirect cryostating, prepreg (thermosetting fiberglass fabric impregnated with epoxide) is used. A new technology of superconducting magnet protection has been applied with the help of sectionalized windings, using passive elements of protection based on “cold” diodes and resistances. A new technology of active protection has also been applied, with normal zone detectors and heaters.