Strong nonuniformities of plasma production are expected in capacitive discharges if the excitation wavelength becomes comparable to the reactor size (standing-wave effect) and/or if the plasma skin depth becomes comparable to the plate separation (skin effect) [M. A. Lieberman et al., Plasma Sources Sci. Technol. 11, 283 (2002)]. Ion flux uniformity measurements were carried out in a large-area square (40 cm×40 cm) capacitive discharge driven at frequencies between 13.56 MHz and 81.36 MHz in argon gas at 150 mTorr. At 13.56 MHz, the ion flux was uniform to ±5%. At 60 MHz (and above) and at low rf power, the standing-wave effect was seen (maximum of the ion flux at the center), in good quantitative agreement with theory. At higher rf power, maxima of the ion flux were observed at the edges, due either to the skin effect or to other edge effects.

Facial displays are an important form of social communication in nonhuman primates. Clues to the information conveyed by faces are the temporal and spatial characteristics of ocular viewing patterns to facial images. The present study compares viewing patterns of four rhesus monkeys (Macaca mulatta) to a set of 1- and 3-sec video segments of conspecific facial displays, which included open-mouth threat, lip-smack, yawn, fear-grimace, and neutral profile. Both static and dynamic video images were used. Static human faces displaying open-mouth threat, smile, and neutral gestures were also presented. Eye position was recorded with a surgically implanted eye-coil. The relative perceptual salience of the eyes, the midface, and the mouth across different expressive gestures was determined by analyzing the number of eye movements associated with each feature during static and dynamic presentations. The results indicate that motion does not significantly affect the viewing patterns to expressive facial displays, and when given a choice, monkeys spend a relatively large amount of time inspecting the face, especially the eyes, as opposed to areas surrounding the face. The expressive nature of the facial display also affected viewing patterns in that threatening and fear-related displays evoked a pattern of viewing that differed from that recorded during the presentation of submissive-related facial displays. From these results we conclude that (1) the most important determinant of the visual inspection patterns of faces is the constellation of physiognomic features and their configuration, but not facial motion, (2) the eyes are generally the most salient facial feature, and (3) the agonistic or affiliative dimension of an expressive facial display can be delineated on the basis of viewing patterns.

Suppression of the standing wave effect in high frequency capacitive discharges using a shaped electrode and a dielectric lens: Self-consistent approach

The standing wave effect causes nonuniform plasma excitation in high frequencies capacitive discharges when the electrode size is not considerably smaller than the excitation wavelength. A shaped electrode was proposed by Sansonnens and Schmitt [Appl. Phys. Lett. 82, 182 (2003)] to suppress this unwanted effect. The shape of the electrode was calculated in the vacuum approximation (no plasma was present between the electrodes), and was found to be Gaussian. The authors postulated that the presence of plasma would not significantly modify the solution. However, it was shown [Chabert et al., Phys. Plasmas 11, 1775 (2004)] using a self-consistent nonlinear transmission line model that the presence of plasma significantly shortens the wavelength for a system composed of two parallel plate electrodes. It was therefore legitimate to expect the optimized shape of the electrode and lens to be different when a plasma is present. Here it is shown that to suppress the standing wave effect the current flowing in the electrodes must be proportional to the discharge radius. This condition is independent of the medium present between the plates and indeed requires a Gaussian electrode.

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between 30 and 60 ttm and anode strips between 3 andHeld lines of one cell of the microstrip gas cltamber. The surface resistivity affects the gain drift which is essentially in a sequence of alternating thin conductive differing mainly for their surface resistivity (10*0-101394). multiwire chambers, ata much smaller scale L2. lt consists Three kinds of glass have been used as substrate ago in an attempt to reproduce the field structure of 125 tim anode pitch has been also successfully tested.The microstrip gas chamber was introduced sometime 10ttm, at a 200 ttm pitch (see fig.2). A detector having a 1. STRUCTU RE OF T1·lE DETECI` OR mixtures have been performed. device a good candidate for tracking at high luminosity colliders. Tests of survivability and of operation of the detector with fast gas minimum ionizing particles of 30 ttm mas, a two track resolution of 250 tim and a high rate capability (above 2-10cms) make the 7 '2'1 successfully tested. A gas gain of 104 and an energy resolution of 11% fwhm at 6 KeV have been measured. A localization accuracy for devices in the detection of X-rays and charged particles. Detectors with 3, 5 and 10 ttm anode widths and 125 or 200 pm pitch have beenWe describe the operating principles of the microstrip gas chamber and the main results of measurements realized with several prototype CSEM, Ncuchatcl, Switzerland A.Pc¤·ct.