ABSTRACT
We have developed a technique for preparation of cross-sectional transmission electron microscopy samples of reacted and unreacted Nb/Al multilayer thin films on sapphire substrates. The choice of substrate was found to be extremely important. Sapphire sputters more slowly than Nb and Nb-compounds and therefore makes it possible to obtain the electron transparent regions in the thin films rather than in the substrate. However, the brittle nature of the sapphire restricts the types of thinning techniques that can be used, requiring extensive ion thinning as a final stage.
Subject(s)
Aluminum Oxide , Aluminum , Microscopy, Electron/methods , Niobium , SiliconABSTRACT
A prototype switching system has been developed which can switch 20 kA at 230 V furnished by low-voltage dc generators at the National Magnet Laboratory. The energy is used to generate quasistatic magnetic fields in liquid-nitrogen-cooled copper coils for times approaching 1 s. The present arrangement is limited to fields up to 40 T. The silicon-controlled rectifier switching system, protective devices, circuit operation, and magnet structures are discussed.
