The NAOS visible wave front sensor
This paper describes the Visible Wave Front Sensor (visible WFS) for the VLT Nasmith Adaptive Optics system (NAOS). This Shack-Hartman-based wave front sensor instrument includes within a continuous flow liquid nitrogen cryostat: - a low noise fast readout CCD camera controlled by the ESO new generation CCD controller FIERA. The readout noise of this system is 3 e- at 50 kilopixel/sec/port, and is only limited by the CCD intrinsic noise. FIERA proposes remotely controlled readout modes with optional binning, windowing and flexible integration time. - two remotely exchangeable micro-lens arrays focusing the analyzed wave front directly on the CCD sensitive surface. The wave front sensor includes also its own atmospheric dispersion compensator. Due to the continuous rotation of the NAOS adapter, the mechanical stiffness of the visible wave front sensor must be very high not to disturb the loop operation (no more than 0.1 μm of lenslet array displacement compared to the CCD location over a 30° rotation angle of the instrument). The following simulations and tests are described: - simulation results providing an estimation of the NAOS maximum operating magnitude - camera optimization - mechanical stiffness measurements.
CONICA: the high-resolution near-infrared camera for the ESO VLT
A high resolution near IR camera (CONICA) for the firs VLT unit is under development, which will provide diffraction limited spatial resolution being combined with the adaptive optics system NAOS. CONICA serves as a multi-mode instrument for the wavelength region between 1.0 and 5.0 micrometers , offering broad band, narrow band or Fabry Perot direct imaging capabilities, polarimetric modes using Wollaston prism or wire grid analyzers and long slit spectroscopy up to a spectral resolution of about 1000 per two pixel. We presented a first concept of CONICA in 1995. In the mean time, large parts of the instrument have been manufactured, the cryostat and the adapter have been finished and first cryogenic test have been performed. This paper describes the actual design and status of development of CONICA focusing on those aspects which have not been described in detail before or the design of which have been changed in the mean time.
Long Ceramic Beam Tubes for Accelerator Magnets
The ceramic beam tubes for the fast and abort kickers and the bucker and pinger magnets used at Fermilab must meet a number of exacting requirements. The tubes must be long and sufficiently straight so as not to limit magnet design. They must have wall strength capable of withstanding the atmospheric and mechanical forces encountered during construction and operation. Vacuum tight ceramic to stainless steel transitions must be of reasonable cost; they must also withstand high temperature processing and remain vacuum tight to the 10/sup -9/ Torr range. To remove the possibility of static charge buildup each tube must have a surface coating of indium oxide applied to the inner wall. This thin coating is difficult to achieve and requires the most careful attention to detail. The methods used at Fermilab to achieve these goals are presented in this paper.