摘要:

AbstractThis paper discusses Langmuir probe arrays as a diagnostic tool for the investigation of low‐frequency plasma turbulence. A particular appealing application is the investigation of drift wave turbulence. In a magnetized plasma experiment with cylindrical geometry, drift waves are destabilized and different states are established ranging from stability to fully developed turbulence. The chief diagnostic tool is an azimuthal probe array consisting of 64 probes with fully parallel data acquisition. This provides spatio‐temporal fluctuation data (‘wave’ fields) of the density, the floating potential, or both. As an example for the analysis of the data, autoregressive spectral estimation is performed. To study the dynamics in direction parallel to the magnetic field, fluctuation data is recorded by an axial probe array consisting of 16 Langmuir probes. This data yields valuable insight into coupling phenomena parallel and perpendicular to the magneti

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380115

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA poloidally oriented electrical probe array immersed into the plasma edge providing spatially and temporally resolved information of the plasma density and potential is used to study plasma edge turbulence at the CASTOR tokamak (R= 0.4m, a= 0.085m). A model of ‘eddies’ formulated in [1] is experimentally proved by means of the mutual correlation between fluctuations of the plasma density and potential. Scans over principal plasma parameters (plasma currentIp, plasma densityneand toroidal magnetic fieldBt) were performed and three different modes (three qualitatively different structures of fluctuations) were observed. The statistics of the fluctuation‐induced flux were studied. A parameter virtually independent of the discharge conditions was found, its nature has not been explaine

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380116

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractMeasurements of the plasma parameters in the PSI‐1 linear device, using a radially moving Langmuir double probe, are presented. The interpretation of the asymmetric I‐U‐characteristics is based on slight differences of the areas, plasma densities, electron temperatures, and plasma potentials of the two tips. These inhomogenities are explained by an aberration effect of the probe path with respect to the axis of the plasma c

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380117

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe transient behaviour of Langmuir probes in a magnetized plasma is investigated by applying short current pulses with Fourier components up to a few MHz to the edge plasma of the W7‐AS stellarator.The current – voltage characteristic and the impedance of the flux tube, extending from the probe tip was measured by using a kind of a pin‐plate‐probe. The results are compared with theoretical models.In a further step, the pin‐plate‐probe and a 15‐pin probe array were connected along a field line in order to investigate the propagation of the induced perturbation.From the results it is likely, that a damped Alfvén‐wave is excited, the propagation of which can be described with the model

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380118

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe radial profile of the electrostatic Reynolds stress has been measured in the plasma boundary region of the TJ‐IU torsatron using multiple Langmuir electrodes. The experimental set‐up consists of an arrangement of 6 Langmuir probes radially and poloidally separated. The spatial orientation of the Langmuir probe array provides a measurement of radial (Ẽr) and poloidal (Ẽθ)electric field fluctuations in a plasma volume smaller than the typical correlation volume of fluctuations.The measured Reynolds stress (proportional to ẼrẼθ)shows a radial variation around the velocity shear location, suggesting that such mechanism can drive poloidal flows in the edge region of the TJ

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380119

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThe time‐domain triple‐probe (TDTP) method has been developed for measurement of turbulent plasma. Rather than implementing the triple‐probe states over a three probe array, the TDTP method cycles each of two Langmuir probes through all triple‐probe states. Provided the turbulence is bandlimited, fast cycling and large probe impedance allow the establishment of probe‐plasma equilibrium for each triple‐probe state, and time resolved measurement of floating potential, ion saturation current, and “return potential” at each of the two probes. A total of six measurements are combined with a system of six equations to solve for six plasma variables; electron temperature, electron number density, and plasma potential at each of the two probes. Successful implementation of the TDTP method in the edge plasma and scrape‐off layer of TEXT‐U measures significant electron temperature fluctuations with poloidal correlation statistics similar to those of floating potential and ion saturation current fluctuations. Electron number density and electron temperature fluctuations are in phase indicating electron pressure fluctuations are important on both sides of the v

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380120

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractWe conducted a set of experiments on the TEXT‐U tokamak using two Langmuir probe arrays separated by 12 m located on or near the same magnetic flux tube. The magnetic flux tube location is determined by driving one set of probes with a single frequency wave and measuring the waves at the downstream location. The driven wave propagates as a shear‐Alfvén wave. From the combination of the driven waves and the location of peak correlation of background turbulence we are able to estimate an averagek‖ for the background turbulence. The high coherence (>0.6) of the background turbulence signals from probes separated by 12 m suggests that most of the power in edge turbulence is contained in long structures (>18 m) in the parallel dir

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380121

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractWe present a novel design for an indirectly heatable Langmuir probe which combines several advantages. Special attention was directed to the insulator material of the probe. It is shown that coating of the probe collector can be removed by sufficient heating for two types of probes, one made of ceramic the other one of glass.

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380122

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractAim of this study is to measure edge plasma parameters in a tokamak using electrical probes with temporal resolution better than 1 ms. It was found that the characteristics are strongly affected by plasma fluctuations and their interpretation might be even impossible. To avoid this problem, the single Langmuir probe is modified and a so called double‐pin‐plate probe is designed: the probe consists from a plate biased by a harmonic voltage and oriented perpendicularly to the magnetic field lines. Simultaneously, the two small pins monitor the ion saturation current and floating potential in front of the plate. We demonstrate that, using such configuration, the “noise” in the I‐V characteristics is reduced. Consequently, the precision of the probe measurements improves sign

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380123

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractMethods to determine the ion cross field flow in a magnetized plasma are analyzed and a novel probe head for such measurements is proposed. First experimental results are discussed.

ISSN:0863-1042    

DOI:10.1002/ctpp.19980380124

出版商:WILEY‐VCH Verlag    

年代:1998

数据来源: WILEY