Tokamak density limit disruptions are studied by tomographically analysing soft X-ray emission data using a modified circular harmonic reconstruction technique. Both minor and major disruptions are associated with the presence of dominant m = lin = 1 and m = 2in = 1 soft X-ray emissivity perturbations leading to the penetration of a cold bubble-like plasma volume to the centre. The role of mode coupling between the various emission components is examined and the observed behaviour is compared with the results of recent theoretical models.
Spring-type magnetostrictive actuator (STMA)1 and platform for adaptive tilt correction in astronomy and high-power technological lasers is discussed. STMA is one of the most promising types of macroactuators for large ground and space-based adaptive optics. By means of STMA it is possible to realize precision displacements in ranges up to 50–100 μm with an accuracy of positioning 0.1 μm and enforcement up to 1000N in a real time scale (1–10 ms). Experimentally investigated static and dynamic characteristics of STMA are discussed in comparison with that of piezoceramical actuators. Real-time two-coordinate mirror positioning system for precise optical engineering is proposed and investigated. The dynamic range of corrected tilts is up to 3°10−3 rad with sensitivity 10−6 rad and frequency range up to 40 Hz. High efficiency for correction of tilts induced by atmosphere turbulence is demonstrated.
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