Use of internal probes for diagnostics of pulse plasma

The paper describes the use of internal magnetic and electric probes for determination of the plasma parameters in the rail accelerator. Suitability of the electric probe is verified by comparison of the floating potential and plasma potential. The intrinsic magnetic field in the cluster, axial component of the electric field, current density and density of electrones in the cluster were measured by these two probes. On the base of obtained results the degree of ionisation and average value of the intrinsic magnetic field were determined.     

Use of perturbing probes for plasma-jet diagnostics

The experience gained in using an array of cylindrical Langmuir probes as a perturbing body for plasma-jet diagnostics is described. The plasma potential on a part of the probe is determined from the ion-scattering minimum at that part. The potential values thus obtained are compared with the results of an analysis of the probe characteristics. The conditions for applicability of the method are discussed. A density marker is created by applying a voltage pulse with a duration of 30 ns to the probes, and time-of-flight probing of the plasma jet is performed. Zh. Tekh. Fiz. 67, 24–27 (July 1997)     

A pulse stacker for time-resolved laser plasma diagnostics

A passive splitter array is described which allows time-resolved plasma diagnostic measurements to be performed on a single shot basis. The advantage of this stacker is that it has high efficiency, is simple, easy to adjust, and can be inserted into an optical beam path without disturbance to alignment.     

Magnetic-probe diagnostics for railgun plasma armatures

The author assesses the strengths and weaknesses of the various magnetic-probe techniques currently in use and provides recommendations for future improvements in magnetic probe diagnostics for plasma-armature railguns. Analytic approximations for the dependence of the probe signal on probe location and railgun geometry are presented. Rail current and armature current probes are compared and contrasted with respect to resolution and accuracy. Further improvements in measurement accuracy are predicted for close-spaced magnetic-probe arrays     

Transient calorimetric diagnostics for plasma processing

We present a detailed study of the Gaussian laser propagation through a dielectric system composed by two right angle prisms. We investigate the transition between the spatial coherence limit, which exhibits wave-like properties and for which the resonance phenomenon can be seen, and the decoherence limit, which exhibits particle-like properties and for which the multiple diffusion occurs. We also analyze the tunneling at critical angles. In our numerical analysis, we shall use BK7 and Fused Silica prisms and a Gaussian He-Ne laser with a wavelength of 632.8 nm and beam waists of 2 mm and 200 μm.     

In-situ diagnostics for plasma surface processing

A survey is given of in-situ diagnostics of plasma and surface for application in plasma etching and deposition. Especially those diagnostics that increase the fundamental understanding of the elementary processes occurring both within the plasma and at the surface are highlighted. In general, diagnostics are performed to determine the value of a physical parameter. This value is fed into models of plasma or surface, and in that way the understanding of the process is enhanced. In the paper first the most interesting physical parameters are defined. Subsequently the diagnostic techniques currently available to determine those parameters are reviewed.     

Nonlinear optical techniques for plasma diagnostics

The application of various nonlinear optical laser spectroscopic techniques to plasma diagnostics are reported. The techniques discussed in this paper are two-photon laser induced fluorescence spectroscopy, double-resonant four-wave mixing, coherent anti-Stokes Raman-scattering (CARS), and a combination of emission spectroscopy and CARS. They are applied to measurements of atomic hydrogen densities, molecular temperature, chemical composition, electric field distributions, and vibrational population distribution. The basic principles are described and important aspects of the methods are discussed in context with application to various kinds of discharges at low and elevated pressures     

Nonlinear optical effects for plasma diagnostics

Experimental investigations show that the 1/f noise intensityC and the contact resistanceR can be used to analyse contacts. The simply prepared contacts are fritted by discharging a capacitor, resulting in a multi-spot contact. A model relatesC andR to a number of contact spotsk with radiusa. More impulse-frittings at increasing energies decreaseC andR, thus enhancing the values ofk anda. From experimentalC vsR plots two regions are determined for GaAs: A fritting (a=constant) and A+B fritting (a∝k). Calculated values ofk are in good agreement with the number of peaks or pits formed by etching the semiconductor surface. From experimentalC vsW orR vsW curves, withW the cumulative impulse-fritting energy, the conclusion can be made thatka ³ is proportional toW.     

Measuring the parameters of pulsed plasma flows by means of magnetic probes

The electron temperature and plasma concentration generated in a pulsed plasma accelerator are determined experimentally. The peculiarities of generation and acceleration of current sheets in the interelectrode space of the pulsed plasma accelerator are investigated.     

Stripline probes for nuclear magnetic resonance

A novel route towards chip integrated NMR analysis is evaluated. The basic element in the design is a stripline RF 'coil' which can be defined in a single layer lithographic process and which is fully scalable to smaller dimensions. The sensitivity of such a planar structure can be superior to that of a conventional 3D helix. The basic properties, such as RF field strength, homogeneity and susceptibility broadening are discussed in detail. Secondary effects related to the thermal characteristics are discussed in simplified models. Preliminary NMR tests of basic solid and liquid samples measured at 600 MHz confirm the central findings of the design study. It is concluded that the stripline structure can be a valuable addition to the NMR toolbox; it combines high sensitivity with low susceptibility broadening and high power handling capabilities in a simple scalable design.     

Pulse radar reflectometry for fusion plasma diagnostics

A basic principle of pulse radar reflectometry is considered in this paper. A numerical analysis is performed in order to study errors appearing due to the expansion of a microwave pulse reflected from the plasma.A block diagram of the basic pulse radar scheme and its overall performance is presented. The first experimental results obtained on T11-M tokamak are discussed.An improved pulse radar scheme with cross-detection is considered. The results of bench test experiments and future applications of this scheme are discussed.     

Giant pulsed molecular laser for plasma diagnostics

Report on the 5th All-Union Conference on High-Temperature Plasmas (June 18–22, 1990, Minsk).     

Energy dispersive X-ray spectroscopy for ECR plasma diagnostics

Electron-ion bremsstrahlung spectra down to 4 keV emitted from plasmas of the 7.25 GHz electron cyclotron resonance (ECR) ion source of the Forschungszentrum Rossendorf and of the 14.5 GHz ECR ion source of the Technische Universität (TU) Dresden were de-convoluted using a newly developed integration method. In the approximation of isotropy in velocity space this method yields the exact electron energy distribution function. The high energetic electrons are clearly separated into two Boltzmann distributed populations. Their densities and temperatures could be estimated. Higher frequencies of the microwave can increase the hot and warm electron densities by orders of magnitude. First results are obtained for the behaviour of this populations belonging to the mixture (argon — oxygen). Gas mixing increases the densities of these populations. The influence of the electron energy distribution function on X-ray line intensities is discussed.     

Schlieren method and its application for plasma diagnostics

In recent years experiments were done with the application of the schlieren method for measuring electronic and atomic density gradients in plasma. The method proved to be useful. The aim of this paper is to point out the advantages of this rarely used optical method. The principle, characteristic and application of the mentioned method in plasma physics are described.     

A multifrequency gyrotron for plasma heating and diagnostics

Gyrotrons are regarded as a necessary component of any modern fusion machine. They are presently used primarily to heat the electron component of the plasma. However, gyrotrons can be utilized also to drive the current, to stabilize MHD modes, to measure the ion temperature by means of the collective Thomson scattering, to mention just a view plasma diagnostic purposes. In this work we present a design of a multifrequency gyrotron, i.e., a gyrotron which generates RF power simultaneously at several frequencies and discuss possible applications of such tubes.     

Strong interacting probes for quark gluon plasma

We discuss hadronic signals for quark gluon plasma formation in relativistic nuclear collisions utilizing a non-equilibrium model for hadronisation of the plasma state. In particular, we find that several (non-)strange antibaryon to baryon ratios may serve as a signal for a baryon-rich plasma state. The? toη ratio turns out to be not a direct signal for plasma formation due to its dependence on details of the collision dynamics and hadronisation mechanism. Finally we argue that the η′ to η ratio might be useful as a “gluonometer” in measuring the gluonic content of the matter formed in the initial stage of the collision process.     

Local magnetic probes of superconductors

Investigations of the magnetic properties of high temperature superconductors (HTSs) have revealed the existence of striking new vortex phenomena due, in part, to their strong crystalline anisotropy, very short coherence lengths and the much larger thermal energies available at high temperatures. Some of these phenomena, for example vortex lattice 'melting', pose serious problems for technological applications of the most anisotropic HTS materials and a fuller understanding of them is of considerable importance. The most direct information regarding vortex structures and dynamics is obtained through local measurement of the magnetic field within or at the surface of a superconducting sample. A detailed review of such local magnetic probes is presented here including Lorentz microscopy, magnetic force microscopy, Bitter decoration, scanning Hall probe microscopy, magneto-optical imaging, and scanning superconducting quantum interference device microscopy. In each case the principles underpinning the technique are described together with the factors that limit the magnetic field and the spatial and temporal resolution. A range of examples will be given, emphasizing applications in the area of HTSs. In addition the ways in which the existing techniques can be expected to develop over the next few years will be discussed and new approaches that seem likely to be successful described.     

Quasistationary magnetic field generated in a plasma by a whistler-mode radio pulse

It has been shown experimentally that a quasistationary magnetic field is generated in a weakly collisional magnetized plasma by a spatially nonuniform high-frequency whistler-mode field. The sources of the quasistationary magnetic field are nonlinear currents generated due to the longitudinal and transverse components of the ponderomotive force, acting on charged particles in the spatially localized high-frequency pump field. The dynamics of the excited magnetic fields has been analyzed. It was found that the settling time of the quasistationary magnetic field is determined by the switching-on time of the high-frequency field and the propagation of pulsed current and magnetic fields from the region of their generation occurs with the velocity of low-frequency whistler waves.