This paper describes the feasibility study result for a variable optical attenuator (VOA) realized by a new concept of self-assembled polysilicon structures and a continuously position-controllable curved beam actuator based on surface micromachining technology. The self-assembly mechanism includes a residual stress induced curved beam which lifts up the reflective mirror shutter first. This self-assembled reflective pop-up shutter is locked and fixed on a curved polysilicon beam actuator which is connected with a polysilicon frame clamped on the substrate. Secondly, a set of polysilicon scratch drive actuators drives the frame, curved beam actuator and shutter moving forward and sliding into the space between the two ends of the input and output fiber ports. The optical attenuation range of the proposed VOA is determined by the vertical position of the self-assembled reflective shutter which is controlled depending on the applied voltage value. This new VOA has demonstrated continuous attenuation capability and wide attenuation range. This device demonstrates 70 dB attenuation range and less than 1 dB insertion loss.

New excitation channels for the explanation of the strong emission of Li-like and Be-like satellite transitions in numerous picosecond and subpicosecond laser-produced plasma experiments are proposed. 'Blue Li-like satellites' of the He-like resonance line W are predicted. Corresponding spectral simulations exploiting new calculated atomic data for these mechanisms are in rather good agreement with experimental single-shot spectra of plasma produced at the intensities up to 10 18 W cm −2 and recorded by means of a high-resolution spherically bent mica crystal technique.The analysis of the soft x-ray emission of highly charged ions from picosecond and subpicosecond laser-produced plasmas has to deal with extremely transient and non-Maxwellian plasmas (Cobble 1995). Unfortunately, due to the subpicosecond time scales, direct temporal experimental information is often insufficient or absent. So far, most of the analysis only concerns the emission of the He-like resonance line W = 1s 2 -1s2p 1 P 1 , intercombination line Y = 1 s 2 -1s2p 3 P 1 and its Li-like satellites 1s 2 2x-1s2x2y. However, our present pslaser experiments exploiting the recently developed high-resolution technique of spherically bent mica crystals (Bryunetkin et al 1992, Faenov et al 1994 show the importance of numerous higher-order satellite transitions and excitation channels from Be-and Li-like ions which have not been investigated so far.The experiments were carried out with the CPA Nd-glass picosecond laser at the Max-Born Institute (Kalashnikov et al 1994b) and nanosecond Nd-glass laser at VNIIFTRI. The ps-laser pulse has an energy up to 1 J, duration of 1.5-2 ps and an ASE contrast of 4 × 10 9 (ps-laser (2) in the following). An improvement of the contrast to 10 10 and a steepening of the rising pulse front was realized with a nonlinear absorber cell in the output beam (ps-laser (1) in the following). The influence of the contrast on the dynamics of the laser-plasma interaction has been described elsewhere (Kalashnikov et al 1994a). The laser beam was focused with an aspherical lens f/2 (f = 123 mm) on the surface of a massive magnesium target. The focal spot diameter was about 5 µm so that an incident laser intensity of up to

Cluster production in 340 GeV/c pion-emubion interactions, using the method of rapidity-gap correlations, has been studied. The particles are found to be more strongly correlated in the forward region of the rapidity space. The size of clusters does not depend on the target size. The rapidity width and maximum rapidity-gap length distributions are also studied.

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Volume recombination of C 4+ and e − into C 3+ is observed for the first time in detached divertor plasmas with an X-point MARFE. The recombination zone is located around the X-point, and the electron temperature and density are evaluated to be 6.3 eV and 7.8 × 10 20 m −3 , respectively. In this zone, the volume recombination flux is larger by two orders of magnitude than the ionization flux of C 3+ . However, the radiation power due to the recombination process is only 2% of the total radiation power, measured by a bolometer. In contrast, the radiation power due to the excitation process from the ground state of C 3+ by electron collision dominates the total radiation power.