Because of the practical importance of sputtering, numerous theories and computer simulations are used for predicting many aspects of the sputtering process. Unfortunately, many of the calculated sputtering results are untested by experiment. Until recently, most sputtering experiments required either very high ion fluences or the detection of only minor constituents of the sputtered flux, i.e., ions. These techniques may miss the subtleties involved in the sputtering process. High-detection-efficiency mass spectrometry, coupled with the laser ionization of neutral atoms, allows the detection of the major sputtered species with very low incident ion fluences. The depth-of-origin of sputtered atoms is one example of an important but poorly understood aspect of the sputtering process. By following the sputtering yield of a substrate atom with various coverages of an adsorbed overlayer, the depth of origin of sputtered atoms has been determined. Our results indicate that two-thirds of the sputtered flux originates in the topmost atomic layer. The ion-dose dependence of sputtering yields has long been assumed to be quite minor for low- to-moderate primary ion fluences. We have observed a two-fold decrease in the sputtering yield of the Ru(0001) surface for very low primary ion fluences. Data analysis results in a cross section …

The CC Cryostat was moved to the cleanroom for the installation of modules: Work will continue on the top of the Cryostat with the help of platforms attached to both sides of the Cryostat. It was desired to access this platform from a nearby balcony via a walkway or 'spacewalk'. The spacewalk was to attach to the substructure of the east fold-down platform and across the balcony to some kind of staircase structure. The final design was a free standing stair frame and a rectangular box platform with handrails which hooks onto the stair frame and the substructure of the platform. A sketch of the cleanroom and spacewalk are included following this report. Since the spacewalk structure had to be hand assembled once on the balcony. the material chosen was stock 6061-T6 aluminum. This aluminum combines high-strength (35 ksi yield) and light weight. A 1-1/2-inch aluminum bar across the staircase provides the structure for the walkway platform to hook onto. No-skid pads are placed on the channel stairs and the surface of the walkway platform to assure sure footing. The level of the walkway platform lies approximately 10-inch below the surface of the fold-down platform. thus requiring users to step …