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Electrical conduction in potassium boro-vanadate iron glass

Tue, 01 Feb 2005 00:00:00 GMT

Title: Electrical conduction in potassium boro-vanadate iron glass Authors: Panchal, Harshvadan R; Kanchan, Dinesh K Abstract: The conduction mechanism of xK₂O:(100-x-y)[(1+n)V₂O₅:B₂O₃ where x = 0,5,10,15, 20, y = 5, 7.5, 10, 12.5 and 15 and n = 0.2 to 1 in step of 0.2 had been explained on the basis of Mott's theory. The de conductivity of the present glass system was measured in the temperature range 315-435 K for all the different glass compositions. The decrease of conductivity and increase in activation energy had been observed with the increase of Fe₂O₃ concentration. Estimated small polaron radius is found to be smaller than the atomic site spacing (V-V spacing) and greater than the radius of iron on which the electron is localized. The present glass system shows a semiconducting adiabatic hopping due to a small polaron. Page(s): 137-141

Development of a large area telescopic detector system for elastic and transfer reaction angular distribution measurements

Mon, 01 Aug 2005 00:00:00 GMT

Title: Development of a large area telescopic detector system for elastic and transfer reaction angular distribution measurements Authors: Kalita, K; Jhingan, A; Barua, S; Das, J J; Varughese, T; Sugathan, P; Madhavan, N; Nath, S; Verma, S; Singh, R Abstract: A large area telescopic detector set-up (ΔE-E) has been developed for elastic scattering and transfer reaction measurements involving low intensity radioactive ion beam (RIB) at Nuclear Science Centre (NSC), New Delhi. The detector system consists of a transmission type gas ionization chamber (ΔE-E) with axial field geometry followed by E-two-two-dimensional position sensitive silicon detectors (2D-PSSD) placed side by side (50 mm × 50 mm each) for the residual-energy measurements. The gas ionization chamber (IC) gives the energy loss of the particles for Z-identification whereas the silicon detectors give their energy as well as the position. The responses of the IC with alpha and fission sources, and of the entire detector system with ⁷Be beam are presented which demonstrate the overall performance. Page(s): 567-572

Effect of metallic substitution on the optical, mechanical and photoconducting properties of L-arginium diphosphate single crystals

Wed, 01 Jun 2005 00:00:00 GMT

Title: Effect of metallic substitution on the optical, mechanical and photoconducting properties of L-arginium diphosphate single crystals Authors: Pragasam, A Joseph Ami; Selvakumar, S; Madhavan, J; Anand, D Prem; Sagayaraj, P Abstract: L-arginium diphosphate (LADP) is one of the important analogs of LAP crystal. LADP has excellent optical, thermal and mechanical properties, which make it a potential candidate for photonics device fabrication. The present work deals with the growth and characterization of metal (Cu²⁺ and Mg²⁺) substituted single crystals of LADP. The grown crystals are subjected to single crystal XRD, AAS, FTIR, DRS spectra and microhardness studies. Microhardness studies indicate that the presence of dopant has enhanced the hardness of the material. The photoconductivity study reveals the positive photoconducting nature of both pure and doped crystals. Page(s): 463-468

Adaptive optics and its applications

Wed, 01 Jun 2005 00:00:00 GMT

Title: Adaptive optics and its applications Authors: Mohan, D; Mishra, S K; Saha, S K Abstract: The adaptive optics (AO) system combines technologies that enable corrections in real time for the deleterious effects of the atmosphere allowing terrestrial telescopes to achieve their near diffraction-limit. Such a system introduces controllable counter wavefront distortions, which both spatially and temporally follow that of the atmosphere. AO system has advantages over post-detection image restoration techniques that are limited by noise and recovers near diffraction-limited images and improves the point source sensitivity. This system may become standard tool for the new generation large optical imaging systems. Development of such a technique was made possible due to the significant improvements in technological innovation over the past few decades. After a brief introduction on the deleterious effects of the atmosphere on the image, this article discusses in detail about required components in order to develop the AO system and its applications in various fields, particularly in observational astronomy. Page(s): 399-414