Download or read book A Fast Reciprocating Langmuir Probe for the DIII D Divertor written by and published by . This book was released on 1996 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new reciprocating Langmuir probe has been used to measure density and temperature profiles, ion flow, and potential fluctuation levels from the lower divertor floor up to the X-point on the DIII-D tokamak. This probe is designed to make fast (2 kHz swept, 20 kHz Mach, 500 kHz Vfloat) measurements with 2 mm spatial resolution in the region where the largest gradients on the plasma open flux tubes are found and therefore provide the best benchmarks for SOL and divertor numerical models. Profiles are constructed using the 300 ms time history of the probe measurements during the 25 cm reciprocating stroke. Both single and double null plasmas can be measured and compared with a 20 Hz divertor Thomson scattering system. The probe head is constructed of four different kinds of graphite to optimize the electrical and thermal characteristics. Electrically insulated pyrolytic graphite rings act as a heat shield to absorb the plasma heat flux on the probe shaft and are mounted on a carbon/carbon composite core for mechanical strength. The Langmuir probe sampling tips are made of a linear carbon fiber composite. The mechanical, electrical, data acquisition and power supply systems design will be described. Initial measurements will also be presented.

Download or read book Plasma Diagnostics for the DIII D Divertor Upgrade written by and published by . This book was released on 1990 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: The DIII-D tokamak is being upgraded to allow for divertor biasing, baffling, and pumping experiments. This paper gives an overview of the new diagnostics added to DIII-D as part of this Advanced Divertor Program. They include tile current monitors, fast reciprocating Langmuir probes, a fixed probe array in the divertor, fast neutral pressure gauges, and H{sub {alpha}} measurements with TV cameras and fiber optics coupled to a high resolution spectrometer. 9 refs.

Download or read book Reciprocating and Fixed Probe Measurements of N sub E and T sub E in the DIII D Divertor written by and published by . This book was released on 1996 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes divertor density and temperature measurements using both a new reciprocating Langmuir probe (XPT-RCP) which plunges vertically above the divertor floor up to the X-point height and swept, single, Langmuir probes fixed horizontally across the divertor floor. These types of measurements are important for testing models of the SOL and divertor which then are used to design plasma facing components in reactor size tokamaks. This paper presents an overview of the new divertor probe measurements and how they compare with the new divertor Thomson scattering system. The fast time response of the probe measurements allows detailed study of ELMs.

Download or read book Langmuir Probe in Theory and Practice written by Evgeny V. Shun'ko and published by Universal-Publishers. This book was released on 2009 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: From flat-panel televisions to thermonuclear fusion for energy production, plasmas currently have numerous and wide applications in sciences and industry. A diversity of plasma diagnostics is available to physicists and engineers to measure and control plasma parameters. Among them, the Langmuir probe is the most inexpensive and most popular instrument and method. The Langmuir probe is a small electrode which is submerged in plasma in order to measure the probe current-voltage characteristic. The same characteristic is processed further to derive the electron and ion concentration, the electron distribution function, and the plasma potential at the probe location. Langmuir probe diagnostics afford rapid measurements of the electron distribution function and plasma potential at a good time resolution, 10-8 seconds in a wide range of plasma densities 10+3 - 10+14 cm-3, and the electron energy from the room temperature to hundreds of electron-volts - qualities which are essential for researchers. In view of these facts, Langmuir probe diagnostics are applied very frequently to measuring plasma parameters. This book will be useful in teaching plasma diagnostics to undergraduate and graduate students in plasma physics courses. And it will also serve as a practical reference manual for physicists and engineers working in the growing area of plasma physics. The reader of this book will learn what kind of plasma parameters the Langmuir probe can measure, how to develop the probe diagnostics for specific cases, and how the probe data obtained should be processed to deduce reliable plasma parameters. In this book, the reader can find not only the basic physics information important to understanding the principles of probe operation, but also how the "real" probe disturbs plasma, and how it is possible to reconstruct undisturbed plasma parameters with available probe data.

Download or read book Divertor Sheath Power Studies in DIII D Using Fixed Langmuir Probes and 3 D Modeling of Tile Heat Flows written by and published by . This book was released on 2013 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Experimental Simulation of a Gaseous Divertor written by Gennady Fiksel and published by . This book was released on 1991 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 692 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurements of Flows in the DIII D Divertor by Mach Probes written by and published by . This book was released on 1998 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt: First measurements of Mach number of background plasma in the DIII-D divertor are presented in conjunction with temperature T{sub e} and density n{sub e} using a fast scanning probe array. To validate the probe measurements, the authors compared the T{sub e}, n{sub e} and J{sub sat} data to Thomson scattering data and find good overall agreement in attached discharges and some discrepancy for T{sub e} and n{sub e} in detached discharges. The discrepancy is mostly due to the effect of large fluctuations present during detached plasmas on the probe characteristic; the particle flux is accurately measured in every case. A composite 2-D map of measured flows is presented for an ELMing H-mode discharge and they focus on some of the details. They have also documented the temperature, density and Mach number in the private flux region of the divertor and the vicinity of the X-point, which are important transition regions that have been little studied or modeled. Background parallel plasma flows and electric fields in the divertor region show a complex structure.

Download or read book Nuclear Fusion written by and published by . This book was released on 2003-10 with total page 948 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book 16th IEEE NPSS Symposium Fusion Engineering written by and published by . This book was released on 1995 with total page 900 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Chemical Abstracts written by and published by . This book was released on 1991 with total page 2682 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Government Reports Announcements Index written by and published by . This book was released on 1995 with total page 564 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Divertor Heat and Particle Flux Due to ELMs in DIII D and ASDEX Upgrade written by and published by . This book was released on 1996 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt: The authors characterize the divertor target plate heat and particle fluxes that occur due to Edge-Localized-Modes (ELMs) during H-mode in DIII-D and ASDEX-Upgrade. During steady-state ELMing H-mode the fraction of main plasma stored energy lost with each ELM varies from 6% to 2% as input power increases above the H-mode power threshold. The ELM energy is deposited near the strikepoints on the divertor target plates in a fast time scale of ≤ 1 ms. The spatial profile of the ELM heat pulse is flatter and broader, up to about a factor of 2, than that of the heat flux between ELMs. On ASDEX-Upgrade the inboard strike-point receives the greatest fraction, ≥ 75%, of ELM divertor heat flux, while on DIII-D the in/out split is nearly equal. The toroidal asymmetry of the heat pulse has produced a peaking factor on DIII-D of no more than 1.5. The particle flux, as measured by Langmuir probes, has also been found to be localized near the divertor strike-points. The increased particle flux during ELMs is a significant fraction of the total time-integrated divertor plate particle flux.

Download or read book An Evaluation of Kinetic Effects in the DIII D Divertor written by and published by . This book was released on 1998 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Under certain conditions, high temperature electrons diffusing across the separatrix near the midplane can propagate to the divertor without collision and produce a high energy tail in the electron distribution function near the separatrix. The authors evaluate a kinetic criterion along the field using measurements from divertor Thomson scattering and compare temperature measurements from target plate Langmuir probes to estimate the magnitude of the high energy tail. A Fokker-Planck kinetic model, which includes electron-electron, electron-ion, electron-neutral, and charge exchange interactions is used to estimate the size of the high energy tail. For the cases considered, the authors found less than 1% of non-thermal particles near the target plate at typical densities and power levels for the DIII-D scrape-off layer plasma. ELMs violate the kinetic criterion.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1990 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Erosion and Deposition of Metals and Carbon in the DIII D Divertor written by and published by . This book was released on 1995 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: Net erosion rates at the outer strike point of the DIII-D divertor plasma were measured for several materials during quiescent H-mode operation with deuterium plasmas. Materials examined include graphite, beryllium, tungsten, vanadium and molybdenum. For graphite, net erosion rates up to 4 nm/sec were found. Erosion rates for the metals were much smaller than for carbon. Ion fluxes from Langmuir probe measurements were used to predict gross erosion by sputtering. Measured net erosion was much smaller than predicted gross erosion. Transport of metal atoms by the plasma across the divertor surface was also examined. Light atoms were transported farther than heavy atoms as predicted by impurity transport models.