First Astronomical Light with TIMMI2, ESO's 2nd-Generation Thermal Infrared Multimode Instrument at the La Silla 3.6-m Telescope
TIMMI, featuring a 64 × 64 gallium doped silicon array and mostly ger-manium refractive optics inside a solid-nitrogen/liquid-helium dewar, was in constant use until its decommission-ing in 1999 (cf. Stecklum et al. 1999). By then, the development of detectors had progressed so rapidly, that the instrument no longer appeared competitive. In fact, in 1993 ESO joined a consortium of French institutes to develop, based on the array used e.g. in TIMMI, a next-generation device (cf. e.g. Lucas et al. 1994). Already the format of this device (128 × 192 pixel) suggested that it would be desirable to build a new camera, rather than trying to use the new device in the existing setup. Even larger arrays were announced by US suppliers. To that end ESO had developed some basic ideas for the optics of a next-generation instrument for the La Silla 3.6-m telescope (cf. Käufl & De-labre, 1994). As a result of the La Silla 2000 questionnaire (see Anderson 1994) in The Messenger 78, ESO received a proposal from the A s t r o p h y s i k a l i s c h e s Institut und Sternwarte of the Friedrich-S c h i l l e r-Universität (FSU) in Jena, Germany, to build TIMMI2. This proposal , reflecting ESO's optical concept, was based on a modern cryostat cooled by a Closed Cycle Expansion Cooler Machine and was also featuring a polarimetric option (not available in TIMMI). Personnel cost and capital investments could largely be covered by funds raised by the Institute in Jena. The PI in Jena was Hans-Georg Reimann. After some negotiations , a Memorandum of Understanding was signed and the work began in early 1996. The design sketch of ESO (see above) was first transformed into a FEM 1 certified conceptual design, both for the optics and mechanics, by the company Jena-Optronik GmbH. Based on this work, the final design and the detail design of the instrument were done at the physics department of the FSU. To the extent that this was feasible, all mechanical parts were manufactured in the workshops of the FSU. In the course of the project, the group at the FSU could enlist a team from the Sternwarte der Universität Wien f o r
A sky-noise measurement and its implication for ground-based infrared astronomy in the 10μm atmospheric window
A spectral analysis of the fluctuations of the infrared sky radiance at λ ≈ 10μm was made at the ESO-site of La Silla in Northern Chile. The data are compared to literature. The consequences of the results on infrared observing for future large telescopes are discussed: our data suggest that in order to achieve background noise limited performance in the 10μm atmospheric window chopping with frequencies of ≈8 Hz and amplitudes of ≈10 arcsec is mandatory.
In-House Industrial Production of the Superconducting Conductor for the 43 T Hybrid Magnet of LNCMI-Grenoble
The hybrid magnet being built at LNCMI-Grenoble is based on the combination of resistive inserts, made up of Bitter and polyhelix coils, with a large bore superconducting outsert. It will produce, in the first step, an overall continuous magnetic field of 43 T in a 34 mm warm bore aperture. The superconducting coil will provide a nominal magnetic field of 8.5 T in a 1.1 m cold bore diameter. It relies on the novel development of an Nb-Ti/Cu Rutherford Cable On Conduit Conductor (RCOCC) cooled down to 1.8 K by a bath of superfluid helium pressurized at 1200 mbar. After a brief reminder of the specificity of hybrid magnets, namely the strong electromechanical coupling between resistive and superconducting coils, the main requirements of the RCOCC for efficient and reliable magnet operation are given. The test and validation phases prior to the industrial production of the RCOCC are reported, including the trial production of the ½ hard-drawn (H02 cold-worked) Cu-Ag 0.05% hollow stabilizer in continuous lengths of 325 m. The novelty of the RCOCC development concerns the assembly and the induction soft-soldering of the Rutherford cable on the Cu-Ag hollow stabilizer allowing a strict control of the interstrand contact resistance. Studies, developments, and the integration of the industrial production line at LNCMI-Grenoble are presented together with the result of the production of all RCOCC unit lengths.