排序方式: 共有23条查询结果,搜索用时 15 毫秒
11.
Thogersen E.N. Shohet J.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1996,24(6):1394-1398
Numerical calculations based on Shaing's L-H transition theory in stellarators and performed by Dahi et al. determine viscosity as a function of ion flow speed in the interchangeable module stellarator (IMS). The calculations predict local maximums in viscosity at flows corresponding to Mach numbers -2 and -10, but not elsewhere. The local peaks manifest themselves as jumps in flow speed, and as regions of high radial electric field (Er) shear. By inducting flows swept between Mach numbers ±5, an electron injection biasing probe revealed a jump at -2, but none at +2, in agreement with the numerical results. A series of flow profiles at constant bias confirmed this result. Altogether, these data agree well with the numerical calculations and provide support for Shaing's L-H transition model as applied to stellarators 相似文献
12.
M. Piper J. L. Shohet J. H. Booske K. H. Chew L. Zhang P. Sandstrom J. Jacobs 《Plasma Chemistry and Plasma Processing》1996,16(1):141-152
Plasma source ion implantation (PSII) is a technique for modifying stafaces that places the object to he modified directly into a plasma and then negatively pulse biases the object so as to implant positive ions. If the voltage is high enough, X-rays can he generated by electrons that are also accelerated by the pulse. This work describes techniques for imaging and characterizing the X-rays A pinhole camera was used to image the X-rays being emitted as electrons collided with surfaces in the chamber. The images show that X-rays are generated at the chamber walls and near the target. The time dependence of these X-rays during each pulse was examined using a PIN diode X-ray detector. Then, using another X-ray sensor and pulseheight analyzer, the spectra of the emitted X-rays was determined. The object is to relate the X-ray intensity and spectrum to the temporal and spatial values of the implantation dose so that it may he used as a process monitor and a control sensor. 相似文献
13.
Polypropylene fabrics samples were surface functionalized under Ar and O2 RF plasma conditions. Survey and high resolution photoelectron spectroscopy and attenuated total reflectance FTIR comparative
evaluation of virgin and plasma treated substrat surfaces, and their pentafluorophenyl hydrazine-derivatized correspondents,
indicate that both Ar and O2-discharge treated PP surfaces undergo intense oxidation. C=O, O−C=O, and C−O linkages were identified on both inert and reactive
gas plasma exposed surfaces. It was found that the relative surface atomic concentrations and the relative ratios of newly
created functionalities are controlled by the external plasma parameters (RF power and treatment time). The oxidation of Ar-plasma
treated surfaces has been related toex situ post plasma mechanisms. Dynamic contact angle measurements from unmodified and plasma exposed substrates demonstrated the
presence of increased surface polarity, and its dependence on plasma parameters. AFM evaluations of plasma treated samples
indicate the presence of rough surface morphologies.
Paper based on the results presented during the workshop of the Engineering Research Center for Plasma-Aided Manufacturing
held in Madison, Wisconsin, in Spring 1996. 相似文献
14.
Sarfaty M. Baum C. Breun R. Hershkowitz N. Shohet J. L. Nagpal K. Vincent T. L. Khargonekar P. P. 《Plasmas and Polymers》1997,2(4):229-244
An in situ single point two-color laser interferometer is used to monitor in real-time the thickness of thin transparent films during processing. The instantaneous change of film thickness is determined by comparing the measured laser reflection interference to that calculated by a model. The etch or deposition rates of the film are determined within 1–2 seconds. The film thickness is also determined in real-time from the phase difference of the reflected laser intensity between the two laser colors. Use of two-color laser interferometry improves the accuracy of the calculated etch or growth rates of the film considerably. Moreover, the two colors provide a clear distinction between film etching and deposition, which may often occur during the same process, and can not be determined by a single color interferometer. The uniformity of the film's etch or deposition rates across the substrate is monitored by an in situ full-wafer image interferometer. The combined use of these two sensors provide instantaneous information of the film thickness, etch or growth rates, as well as time averaged uniformity of the process rates. This diagnostic setup is very useful for process development and monitoring, which is also suitable for manufacturing environment, and can be used for real-time process control. 相似文献
15.
Dahi H. Talmadge J.N. Shohet J.L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(6):1738-1744
A numerical code is developed to study the effect of ion density and temperature (as well as ion pressure and temperature gradients) on the amplitude of the local maxima of the poloidal viscosity with respect to the poloidal Mach number using the model developed by Shaing (1993). The sum of the poloidal viscosity and ion-neutral collisions is determined from the dependence of the plasma radial current on the radial electric field in a biased electrode experiment. The experimental results in the interchangeable module stellarator agree qualitatively with the predictions of the numerical calculation regarding the effects of variation of ion density and temperature on viscosity 相似文献
16.
The relative fluorine-atomic concentrations and the abundance of CFx functionalities from CF4- and C6F6-RF-plasma treated polypropylene (PP) film surfaces were evaluated. Survey and high resolution (HR) ESCA data indicate that
intense surface fluorination can be carried out, from both fluorine precursors, under relatively low power and treatment time
conditions. However, it was found that the stability (under open laboratory conditions and under various solvent and temperature
environments) of plasma implanted fluorine based groups significantly depend on the nature of plasma gases involved. Simulation
of plasma induced molecular fragmentation, at different electron energy MS conditions, indicates the presence of a much higher
fluorine atom concentration from a CF4-plasma in comparison to a C6F6-plasma. It is suggested that fluorine atom mediated fragmentation of macromolecular backbones is probably responsible for
the erosion of plasma fluorinated surfaces, rather than thermal motion induced burying processes. 相似文献
17.
J. L. Shohet W. L. Phillips A. R. T. Lefkow J. W. Taylor C. Bonham J. T. Brenna 《Plasma Chemistry and Plasma Processing》1989,9(2):207-215
A plasma source has been designed so as to inject plasma directly into a Fourier transform mass spectrometer analysis cell. The source is a small radio-frequency cavity in which gas is ionized with RF. The source is coupled to the analysis cell through a small orifice. Argon irons from an argon plasma produced in the source have been injected, trapped and heated (excited), and detected in the analysis cell. 相似文献
18.
Hamann J. R. Hatch A. J. Shohet J. L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1974,2(4):241-249
Observations have been made of an rf multiple-ring discharge which is a variant of the well-known single-ring rf discharge described by J. J. Thomson. A set of discretely-located plasma rings (typically 2 to 5 in number) forms coaxially in the central portion of a cylindrical quartz tube on the axis of a cylindrical cavity excited in the TE011 mode. The rings fit closely inside the inner periphery of the quartz tube at pressures ranging from a few Torr to atmospheric, have a minor diameter of order 1/10 the tube diameter, and are spaced at intervals nearly equal to the tube diameter. Excitation of the degenerate companion TM111 mode results in asymmetrical tilting of the rings. Gas flow through the discharge tube results in a continuous unidirectional axial motion of the rings with new rings being abruptly formed toward the input end of the tube and contracting and vanishing abruptly as they move toward the exit end. A theory is developed which accounts for the observed phenomena. 相似文献
19.
O'Doherty R. J. Probert P. H. Shohet J. L. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(2):172-179
The 3-dimensional trajectories of a single, charged particle within the fields of a resonant microwave cavity and a DC magnetic mirror were computed. The RF fields were due to the TM011 mode of a cylindrical cavity which produces a closed, 3-dimensional, axisymmetric containment region in the center of the cavity. The mirror field was produced by current carrying rings at the ends of the cylinder. The combined fields were able to contain particles which would escape the RF containment well alone. Similarly, the loss cone angles at the ends of the mirror were decreased, a result noted by Gray [1] for a mirror simulated by parabolic magnetic fields aided by a 1-dimensional RF containment well. 相似文献
20.
Golovato S. N. Shohet J. L. Tataronis J. A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1977,5(2):95-105
A helical wave launching structure is analyzed to determine the spectrum of Alfvén waves that it can excite. Using an ideal MHD plasma model, the effectiveness of this helical coil for producing Alfvén wave heating in the Proto-Cleo stellarator is investigated. It is found that significant energy absorption should occur. The amount of absorption and the frequency range over which it is greatest are dependent on the shape of the radial profiles of the confining magnetic field and the plasma density. 相似文献