Beam Loss Monitors for Heavy Ion Operation

The performance of the LHC as a heavy-ion collider is expected to be limited by a variety of beam loss mechanisms that are non-existent, or substantially different, in the case of protons. Among these are ultra-peripheral interactions of the colliding beams and the collimation inefficiency. Loss patterns are different and require additional installations of beam loss monitors. Further, the relation between energy deposition in superconducting magnet coils and the loss monitor signals has to be reassessed for heavy ions in order to determine the thresholds for dumping beams

Accurate Coordinates and 2MASS Cross-IDs for (Almost) All Gliese Catalog Stars

We provide precise J2000, epoch 2000 coordinates and cross-identifications to sources in the 2MASS point source catalog for nearly all stars in the Gliese, Gliese and Jahreiss, and Woolley catalogs of nearby stars. The only Gliese objects where we were not successful are two Gliese sources that are actually QSOs, two proposed companions to brighter stars which we believe do not exist, four stars included in one of the catalogs but identified there as only optical companions, one probable plate flaw, and two stars which simply remain un-recovered. For the 4251 recovered stars, 2693 have coordinates based on Hipparcos positions, 1549 have coordinates based on 2MASS data, and 9 have positions from other astrometric sources. All positions have been calculated at epoch 2000 using proper motions from the literature, which are also given here.Comment: accepted to PASP, Full version of Table 1 available electronicall

Photoelectrochemical Behavior of Hierarchically Structured Si/WO_3 Core–Shell Tandem Photoanodes

WO_3 thin films have been deposited in a hierarchically structured core–shell morphology, with the cores consisting of an array of Si microwires and the shells consisting of a controlled morphology WO_3 layer. Porosity was introduced into the WO_3 outer shell by using a self-assembled microsphere colloidal crystal as a mask during the deposition of the WO_3 shell. Compared to conformal, unstructured WO_3 shells on Si microwires, the hierarchically structured core–shell photoanodes exhibited enhanced near-visible spectral response behavior, due to increased light absorption and reduced distances over which photogenerated carriers were collected. The use of structured substrates also improved the growth rate of microsphere-based colloidal crystals and suggests strategies for the use of colloidal materials in large-scale applications