Evolution of a dust void in a radio-frequency plasma sheath

The onset and growth of a dust void are investigated in a radio-frequency (rf) sheath of a capacitively coupled argon plasma. A circularly symmetric void emerges and grows with increasing rf power and pressure in the central region of the dust cloud levitating in the sheath. Experimental measurements of the void diameter are compared with the predictions of a simple phenomenological theory, based on a balance of forces on dust grains.     

Laser-particulate interactions in a dusty RF plasma

The interaction of particulates formed in an argon RF discharge containing 1-5% CCl₂F₂ admixture with a pulsed infrared laser (Nd:YAG, intensity ~10⁹ W m^-2, pulse duration ~10^-4 s) has been studied in situ. The white light emitted during this process has been monitored as a function of time and wavelength using a fast photo diode and an optical multichannel analyser. The spectra have been fitted with blackbody curves with a standard deviation of 5%. A spectral temperature of about 3500 K has been obtained for various plasma conditions and attributed to the decomposition temperature of the particulate material. A model based on laser heating, internal heat conduction and chemical decomposition is compared with the experimental results. This model predicts the time constants for heating and decomposition of the particulates and explains the dependence of the measured emission intensity on the laser intensity     

Dynamic effects of the power-conversion module in a reciprocating engine

The forced response characteristics of piston, connecting rod and their assembly, henceforth called power-conversion module, is studied subjecting a forced response model of such a module to combustion characteristics in order to investigate clattering noise characteristics brought with compression ignition excitation. Existing research either focused on the piston or the connecting rod solely. As demonstrated by the modal analysis of the whole power-conversion module, it is revealed that the natural frequencies of the entire module dominate the noise-characteristics of clattering noise even when using a linear model. A subsequent parametric study applying different combustion characteristics with different pressure rise rates, but similar peak pressures on the modal-model of the power-conversion module delivered novel insights into the root cause of clattering noise characteristics. Moreover, the approach delivers an amended understanding of disturbing noises occurring in knock control systems of internal combustion engines. The reason for empirically elaborated limits of the maximum cylinder pressure rise rate to achieve smooth engine acoustics, published first in the late 1920s, was revealed.     

Micro‐Disperse Particles in Plasmas: From Disturbing Side Effects to New Applications

The research effort in the area of dusty plasmas initially aimed at avoiding particle formation and controlling the contamination level in industrial reactors. Nowadays, dusty plasmas have grown into a vast field and new applications of plasma‐processed dust particles are emerging. There is demand for particles with special properties, and for particle‐seeded composite materials. Low‐pressure plasmas offer a unique possibility of confinement, control and fine tailoring of particle properties. The role of plasma technology in treatment and surface modification of powder grains is reviewed and illustrated with examples. The interaction between plasma and injected micro‐disperse powder particles can also be used as a diagnostic tool for the study of plasma surface processes.     

Imaging and post-processing of laser-induced fluorescence from NO in a diesel engine

Received: 11 July 1996/Revised version: 12 November 1996     

Effects of crystal shape on the energy levels of zero-dimensional PbS quantum dots

Nanometer-size PbS quantum dots have been made by electrodeposition on a Au(111) substrate. The deposited nanocrystals have a flattened cubic shape. We probed the single-electron energy-level spectrum of individual quantum dots by scanning tunneling spectroscopy and found that it deviates strongly from that of spherical PbS quantum dots. The measured energy-level spectrum is successfully explained by considering strong confinement in a flattened cubic box.     

Microparticles in a collisional Rf plasma sheath under hypergravity conditions as probes for the electric field strength and the particle charge

We used microparticles under hypergravity conditions, induced by a centrifuge, in order to measure nonintrusively and spatially resolved the electric field strength as well as the particle charge in the collisional rf plasma sheath. The measured electric field strengths demonstrate good agreement with the literature, while the particle charge shows decreasing values towards the electrode. We demonstrate that it is indeed possible to measure these important quantities without changing or disturbing the plasma.