Plasma heating due to X-B mode conversion in a cylindrical ECR plasma system

Extra Ordinary (X) mode conversion to Bernstein wave near Upper Hybrid Resonance (UHR) layer plays an important role in plasma heating through cyclotron resonance. Wave generation at UHR and parametric decay at high power has been observed during Electron Cyclotron Resonance (ECR) heating experiments in toroidal magnetic fusion devices. A small linear system with ECR and UHR layer within the system has been used to conduct experiments on X-B conversion and parametric decay process as a function of system parameters. Direct probing {\em in situ} is conducted and plasma heating is evidenced by soft x-ray emission measurement. Experiments are performed with hydrogen plasma produced with 160-800 W microwave power at 2.45 GHz of operating frequency at $10^{-3}$ mbar pressure. The axial magnetic field required for ECR is such that the resonant surface (B = 875 G) is situated at the geometrical axis of the plasma system. Experimental results will be presented in the paper.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

Optimal error estimates of a mixed finite element method for\ud parabolic integro-differential equations with non smooth initial data

In this article, a new mixed method is proposed and analyzed for parabolic integro-differential equations (PIDE) with nonsmooth initial data. Compared to mixed methods for PIDE, the present method does not bank on a reformulation using a resolvent operator. Based on energy arguments and without using parabolic type duality technique, optimal L2-error estimates are derived for semidiscrete approximations, when the initial data is in L2. Due to the presence of the integral term, it is, further, observed that estimate in dual of H(div)-space plays a role in our error analysis. Moreover, the proposed analysis follows the spirit of the proof technique used for deriving optimal error estimates of finite element approximations to PIDE with smooth data and therefore, it unifies both the theories, i.e., one for smooth data and other for nonsmooth data. Finally, the proposed analysis can be easily extended to other mixed method for PIDE with rough initial data and provides an improved result

Species structure and diversity in Achanakmar-Amarkantak Biosphere reserve, Central India

The present study was aimed at quantifying the species structure and diversity in Achanakmar- Amarkantak Biosphere Reserve. Four sites characterized by varying vegetation attributes and representative of the region were selected. One-hectare, permanent plot was established on each of the site and enumeration was car-ried out by stratified random sampling techinique. The forest sites are characterized by poor species composition. A sum of 2440 trees representing 23 species and 17 families were encountered. Tree, sapling and seedling density (stems ha-1) ranged between 260 - 810, 7500 - 35000 and 25000 - 67500, respectively while the basal cover (m2 ha- 1) ranged between 9.96 - 41.6, 0.86 - 5.07 and 0.28 - 0.96, respectively. Species diversity was highest on the dense site and low on medium site. Beta diversity was highest on degraded site. The presence of a large number of seed-lings indicates the great potential source for future sustainable regeneration, provided by appropriate management regime to protect the forest from degradation and conserve the biodiversity

Growth, Characterization, Vortex Pinning and Vortex Flow Properties of Single Crystals of Iron Chalcogenide Superconductor FeCr0.02_{0.02}Se

We report the growth and characterization of single crystals of iron chalcogenide superconductor FeCr$_{0.02}$Se. There is an enhancement of the superconducting transition temperature (T$_{\rm c}$) as compared to the T$_{\rm c}$ of the single crystals of the parent compound Fe$_{1+x}$Se by about 25%. The superconducting parameters such as the critical fields, coherence length, penetration depth and the Ginzburg-Landau parameter have been estimated for these single crystals. Analysis of the critical current data suggests a fluctuation in electronic mean free path induced ($\delta l$) pinning mechanism in this material. Thermally activated transport across the superconducting transition in the presence of external magnetic fields suggests a crossover from a single vortex pinning regime at low fields to a collective flux creep regime at higher magnetic fields. The nature of charge carriers in the normal state estimated from the Hall effect and thermal transport measurements could provide crucial information on the mechanism of superconductivity in Fe-based materials.Comment: 2 additional figures, additional discussion on nature of charge carrier

Understory vegetation in natural and plantation forest ecosystem of Sarguja (C.G.), India

Understory vegetation serves a special role in maintaining the structure and function of forest ecosystem as they strongly influence regeneration, seedling establishment, growth, nutrient cycling and thus the dynamics of the whole forest ecosystem. The present investigation is aimed to study the composition, structure and diversity of understory vegetation in natural forests and teak plantation of Sarguja forest division of Chhattisgarh. A total of 23 species comprising 5 shrubs and 18 herbs were recorded in natural forest while in teak plantation 3 shrub and 20 herb species were found. In natural forest a total of 4500 shrubs/ha and 8,32,000 herbs/ha were recorded while in plantation site it was 5500 shrubs/ha and 6,96,000 herbs/ha, respectively. In shrub layer the value of species diversity was 1.10 for teak plantation and 2.20 for natural forest. Simpson index was 0.23 for natural forest and 0.57 for teak plantation. The Margalef’s index of richness varied from 0.23-0.48, least in plantation site and peak in natural forest, Equitability index varied from 1.00 to 1.37, lowest in plantation site and higher in plantation site and ? diversity was 1.20 in natural forest and 2.00 in plantation site. In case of herb layer the value of Shannon index, species richness and equitability values were higher in teak plantation while the Simpsons index and beta diversity were found more in natural forest