R. Joshi

Direct electron heating experiment on the Aditya tokamak using fast waves in the ion cyclotron resonance frequency range

Second harmonic heating experiments using fast waves are carried out on the Aditya tokamak in the ion cyclotron resonance frequency (ICRF) range with the help of a 200?kW, 20?40?MHz RF heating system, which is developed indigenously. Significant direct electron heating is observed in a hydrogen plasma. The rise in electron temperature is prompt with the application of RF power and the increment in electron temperature increases linearly with RF power. A corresponding increase in plasma beta and hence an increase in stored diamagnetic energy are also observed in the presence of RF power. The low-Z impurity radiation and electron density do not increase significantly with RF power. The direct electron heating by fast wave in Aditya is also predicted by the ion cyclotron resonance heating code TORIC.

Improving methane yield and quality via co-digestion of cow dung mixed with food waste

Methane (CH4) production and quality were enhanced by the co-digestion of cow dung and food waste (FW) mixed with organic fraction of municipal solid waste (OFMSW) under optimized conditions in bench and semi continuous-scale mode for a period of 30u202fdays. A bacterium capable of high yield of CH4 was enriched and isolated by employing activated sewage sludge as the inoculums. The thirteen bacterial isolates were identified through morphological and biochemical tests. Gas chromatography was used to analyze the chemical compositions of the generated biogas. CH4 yields were significantly higher during co-digestion of Run II (7.59u202fL) than Run I (3.7u202fL). Therefore, the co-digestion of FW with OFMSW and Run II was observed to be a competent method for biogas conversion from organic waste resources.

Polycyclic Aromatic Hydrocarbons from Petroleum Oil Industry Activities: Effect on Human Health and Their Biodegradation

Nowadays pollution control and abatement are critical issues faced by environmental scientists due to rapid industrialization. Petroleum industry is one of the major industries which release hydrocarbon pollutants in environment. Polycyclic aromatic hydrocarbons (PAHs) are the priority pollutants which are released into the environment by exploration activities of petroleum industries. The indiscriminate accumulation of petroleum hydrocarbon pollutants can be hazardous to the human life and aquatic biota. Due to toxicity of these pollutants, establishing efficient and environment-friendly method to degrade and detoxify these pollutants is an important research challenge. Various physiochemical methods are applied all over the world to remediate of petroleum hydrocarbon pollutants. Bioremediation technique has been developed for treatment of crude oil pollutants using biological agents like bacteria, fungi, algae, and plants. Applications of certain microorganisms have gained importance in the field of applied environmental microbiology. The application of microbes to degrade pollutants is getting attention due to its environmental and economic benefits. They can be used to change bioavailability and toxicity of petroleum hydrocarbons present in polluted soil and aqueous environment. This paper explores hydrocarbons present in petroleum crude. The effect of petroleum hydrocarbon pollutants on human health and environment is also discussed. This chapter also explains microbial degradation of these pollutants.

Direct Electron Heating Observed by Fast Waves in ICRF Range on a Low-Density Low Temperature Tokamak ADITYA

Fast wave electron heating experiments are carried out on Aditya tokamak [Ru2009=u20090.75u2009m, au2009=u20090.25m,Btu2009=u20090.75T,ne∼1–3E13/cc,Te∼250eV] with the help of indigenously developed 200 kW, 20–40 MHz RF heating system. Significant direct electron heating is observed by fast waves in hydrogen plasma with prompt rise in electron temperature with application of RF power and it increases linearly with RF power. A corresponding increase in plasma beta and hence increase in stored diamagnetic energy is also observed in presence of RF. We observe an improvement of energy confinement time from 2–4msec during ohmic heating phase to 3‐6msec in RF heating phase. This improvement is within the ohmic confinement regime for the present experiments. The impurity radiation and electron density do not escalate significantly with RF power. The direct electron heating by fast wave in Aditya is also predicted by ion cyclotron resonance heating code TORIC.

Automatic impedance matching network for ICRH-RF experiments on SST-1

Ion Cyclotron Resonance Heating (ICRH) is a promising heating method for a fusion device due to its localized power deposition profile, a direct ion heating at high density, and established technology for high power RF generation and transmission low cost. For the same reason 1.5-Megawatt ICRH system is developed indigenously for steady state super-conducting tokamak (SST-1). Since plasma-loading impedance is generally small as compared to the characteristic impedance of the transmission system, a significant amount of power will be reflected from the antenna back towards the generator giving very high reflections to SWR which can damage the high power RF tube. Hence matching network is used to match the total transmission line system to the antenna impedance so that the RF generator sees a matched load and can operate at high efficiency. In the ICRH system, coarse matching network and the on-line automatic matching network designed for the impedance matching of the system to transfer maximum power to the tokamak plasma during 1000 seconds operation. The plasma impedance varies in time on milliseconds scale and hence on-line impedance matching has to match the impedance on a faster scale to avoid the reflections as well as to transfer maximum power to the plasma for heating. There are two transmission lines connected with Hybrid coupler sourced by RF Generator (RF Power) 45.6 MHz frequency. Automatic matching network is connected with each transmission line, which offers on-line fine matching along with coarse matching system connected with transmission line. The matching system includes stubs, phase shifters and the automatic matching system consists of motorized vacuum variable capacitors connected to 9 transmission line. The method includes the detection of reflected power in transmission line with the help of probes, give a right signal to VME based data acquisition and control system to do calculations and generate the signal to vary the capacitance of motorized vacuum variable capacitors within few milliseconds with the help of the controller of the motor of the variable capacitor. Initially automatic matching system was tested with individual transmission lines and then both the lines were matched simultaneously. In order to deliver power to both the lines from a single RF generator, hybrid coupler was used which also protects RF generator from reflections. Here we present the details of the on-line matching system and its testing results. The significant result is that we could match the variable load impedance with the generator impedance within 40-50 milliseconds with d1600 count of motor controller program.