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The Alpha Magnetic Spectrometer (AMS) is a particle physics experiment for use on the International Space Station (ISS). At the heart of the detector will be a large superconducting magnet cooled to a temperature of 1.8 K by 2500 litres of superfluid helium. The magnet and cryogenic system are currently under construction by Space Cryomagnetics Ltd of Culham, England. This paper describes the cryogenic system for the magnet, designed for the unusual challenges of operating a superconducting system in space. Results from experiments demonstrating some of the new techniques and devices developed for the magnet cryogenics are also presented.

We have measured the magnetoresistance of metallic polyacetylene at temperatures T between 4.2 K and 0.3 K and in fields B up to 3.4 Tesla both parallel and perpendicular to the average current flow. We found an exclusively positive magnetoresistance scaling in low fields as B2/T 2 for T< I K and as B2/T 3 for T> 2 K. At high doping levels the magnetoresistance is small and saturates in high fields at low temperatures. These results are independent of the particular geometry used and will be discussed in terms of the magnetic field effect on the hopping conductivity.One of the intriguing properties of polyacetylene is its virtually metallic electrical conductivity when doped with suitable acceptors like iodine. In spite of a wealth of information that has been obtained about this fascinating organic conductor I a detailed understanding of the electrical transport mechanism is still lacking, mostly because of the complicated morphology and the inhomogeneities associated with it.In our present work we have measured the conductivity of iodine-doped polyacetylene (CHIy) x in the temperature range between 4.2 K and 0.33 K. We mostly studied samples having large iodine concentrations (0.15~y~0.32), i.e. the metallic regime. Magnetic fields up to 3.4 Tesla were employed in both longitudinal and transverse geometries, including the Corbino arrangement. In all of our samples we found a positive magnetoreslstance (MR) becoming very large at low temperatures. The more conducting samples had a smaller MR which saturated at low temperatures, irrespective of the particular geometry. Our results are thus different from those obtained earlier by Kwak et al. 2 and Gould et al. 3 on AsF 5 doped (CH) x and by RSss et el. 4 who find a negative MR at 4.2 K in very metallic samples. Obviously, the detailed form and even the sign of the MR depends on how metallic the samples are prepared.We used samples which were polymerized either according to Luttinger 5 or Shirakawa 6. Treating a 0.6 mm thick layer of Luttinger catalyst solution containing l mg cobalt nitrate and 3 mg sodium boronhydride per ml ethanol at -78°C with acetylene gas results in a sponge llke red polymer layer that was washed twice with ethanol and dried under vacuum. The resuiting shiny film was about 40 ~m thick and weighed 3 mg/cm 2. Alternatively, the wall of a 20 cm long round bottomed, evacuated flask of 5 cm diameter was wettet at -78°C with a degassed Shirakawa catalyst solution containing 3.0 ml aluminiumtriethyl and 1.9 ml titanium tetrabutoxide in 20 ml toluene, aged for one hour. Allowing acetylene gas to flow immediately into the flask, a film was formed, which, after removal of the unreacted catalyst solution, was washed 15 times with dry pentane and then dried. The resulting film was 80 ~m thick and weighed 2 mg/cm 2. Both types of samples were stored under vacuum on dry ice. Doping was performed by repeatedly exposing the samples to iodine vapor and consecutive vacuum pumping at room temperature. Iodine content of the samples was determined by weighing ...

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The 8m coating unit for the VLT mirrors is designed for the deposition of high reflective, homogeneous aluminium coatings. For the process of the film deposition the sputter technology is utilised. The design of the following major subsystems is completed : the vacuum vessel and the vacuum generation system, the thin film deposition equipment and the glow discharge cleaning device, the substrate support and rotation system as well as the supporting framework and the auxiliary equipment. Manufacturing of the Coating Unit has started. The pre-assembly and testing activities, which will take place prior to the shipment to the site, are defined. This paper describes the design features and the major performance requirements of the 8m coating unit. The performance of the sputter source design has been verified in a qualification test. The deposition rate, the film thickness and reflectance, as well as the film purity have been measured. The test set-up and the results of the qualification tests of the selected magnetron type are presented and discussed. SPIE Vol. 2871 / 137 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/16/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx