Thin pole tips

Fig. 8.1 (a) Schematic illustration ol thin film head with a helical coil at the main pole tip. (b) Dependence of field distribution on coil recession height, h [2]. 1999 IEEE... 

Patterson s friend Edward D. Goldberg at the Scripps Institution of Oceanography in La Jolla, California, had tipped him off that one of the best records of the world s climate is embedded in thin layers of glacial ice at high altitudes or near the poles. Snow, dust, and fog deposit chemicals from the atmosphere onto the ice, where they remain undisturbed for thousands of years. As Patterson quickly realized, Only the quiescent ice sheets in the arid, perpetually frozen polar regions of the Earth provide annual layers of precipitation that are undisturbed by percolation and mechanical mixing, that are relatively free of dusts and salts, and also are thin enough to be accessible even when centuries old. ... 

A switching electrode having nanometer dimensions leads to profound difference in poling of fe thin films and fe bulk crystals. In the case of fe thin films with a thickness of about 100 nm, a voltage application between the bottom electrode and an afm tip of 50-100 nm radius forms a quasi-homogeneous electric field. Such a distribution implies a conventional polarization reversal setup as in the case of uniform switching electrodes applied to polar faces of a fe sample. 

To form the array a 70 /un thick poled sheet (5x0.6 mm) of PZT is bonded between two metallized polymer sheets. The PZT is sliced into the 64 elements by diamond-cutting, the cut just penetrating the bottom polymer layer so allowing the whole to be wrapped around the catheter tip. The outer polymer film, about 20 /nn thick, serves as a 2/4 acoustic matching layers and also carries the thin copper tracks to electrically address each element. 

We discover another element when we walk out into the lightning field water skims the surface in patches, turning the earth to bog. We hunt for a missing element fire. I see the first sign of it a thin jag of lightning threads into the tip of a steel pole to my right. 

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