Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors (open access)

Liquid phase epitaxial growth and characterization of germanium far infrared blocked impurity band detectors

Germanium Blocked Impurity Band (BIB) detectors require a high purity blocking layer (< 10{sup 13} cm{sup -3}) approximately 1 mm thick grown on a heavily doped active layer ({approx} 10{sup 16} cm{sup -3}) approximately 20 mm thick. Epilayers were grown using liquid phase epitaxy (LPE) of germanium out of lead solution. The effects of the crystallographic orientation of the germanium substrate on LPE growth modes were explored. Growth was studied on substrates oriented by Laue x-ray diffraction between 0.02{sup o} and 10{sup o} from the {l_brace}111{r_brace} toward the {l_brace}100{r_brace}. Terrace growth was observed, with increasing terrace height for larger misorientation angles. It was found that the purity of the blocking layer was limited by the presence of phosphorus in the lead solvent. Unintentionally doped Ge layers contained {approx}10{sup 15} cm{sup -3} phosphorus as determined by Hall effect measurements and Photothermal Ionization Spectroscopy (PTIS). Lead purification by vacuum distillation and dilution reduced the phosphorus concentration in the layers to {approx} 10{sup 14} cm{sup -3} but further reduction was not observed with successive distillation runs. The graphite distillation and growth components as an additional phosphorus source cannot be ruled out. Antimony ({approx}10{sup 16} cm{sup -3}) was used as a dopant for the …
Date: May 12, 2001
Creator: Bandaru, Jordana
Object Type: Thesis or Dissertation
System: The UNT Digital Library
Laser Profile Measurements of an H Beam. (open access)

Laser Profile Measurements of an H Beam.

A non-intercepting beam profile monitor for H{sup {minus}} beams is being developed at Brookhaven National Lab. An H{sup {minus}} ion has a first ionization potential of 0.75eV. Electrons can be removed from an H{sup {minus}} beam by passing light from a near-infrared laser through it. Experiments have been performed on the BNL linac to measure the transverse profile of a 750keV beam by using a Nd:YAG laser to photoneutralize narrow slices of the beam. The laser beam is scanned across the ion beam neutralizing the portion of the beam struck by the laser. The electrons are removed from the ion beam and the beam current notch is measured.
Date: May 12, 2001
Creator: Connolly, R.; Cameron, P.; Cupolo, J.; Grau, M.; Kesselman, M.; Liaw, C. J. et al.
Object Type: Article
System: The UNT Digital Library
Superconducting solenoids for muon-cooling in the neutrino factory (open access)

Superconducting solenoids for muon-cooling in the neutrino factory

The cooling channel for a neutrino factory consists of a series of alternating field solenoidal cells. The first section of the bunching cooling channel consists of 41 cells that are 2.75-m long. The second section of the cooling channel consists of 44 cells that are 1.65-m long. Each cell consists of a single large solenoid with an average diameter of 1.5 m and a pair of flux reversal solenoids that have an average diameter of 0.7 to 0.9 meters. The magnetic induction on axis reaches a peak value of about 5 T at the end of the second section of the cooling channel. The peak on axis field gradients in flux reversal section approaches 33 T/m. This report describes the two types of superconducting solenoid magnet sections for the muon-cooling channel of the proposed neutrino factory.
Date: May 12, 2001
Creator: Green, M. A.; Miller, J. R. & Prestemon, S.
Object Type: Article
System: The UNT Digital Library
The plasticity of human breast carcinoma cells is more than epithelial to mesenchymal conversion (open access)

The plasticity of human breast carcinoma cells is more than epithelial to mesenchymal conversion

The human breast comprises three lineages: the luminal epithelial lineage, the myoepithelial lineage, and the mesenchymal lineage. It has been widely accepted that human breast neoplasia pertains only to the luminal epithelial lineage. In recent years, however, evidence has accumulated that neoplastic breast epithelial cells may be substantially more plastic in their differentiation repertoire than previously anticipated. Thus, along with an increasing availability of markers for the myoepithelial lineage, at least a partial differentiation towards this lineage is being revealed frequently. It has also become clear that conversions towards the mesenchymal lineage actually occur, referred to as epithelial to mesenchymal transitions. Indeed, some of the so-called myofibroblasts surrounding the tumor may indeed have an epithelial origin rather than a mesenchymal origin. Because myoepithelial cells, epithelial to mesenchymal transition-derived cells, genuine stromal cells and myofibroblasts share common markers, we now need to define a more ambitious set of markers to distinguish these cell types in the microenvironment of the tumors. This is necessary because the different microenvironments may confer different clinical outcomes. The aim of this commentary is to describe some of the inherent complexities in defining cellular phenotypes in the microenvironment of breast cancer and to expand wherever possible on …
Date: May 12, 2001
Creator: Petersen, Ole William; Nielsen, Helga Lind; Gudjonsson, Thorarinn; Villadsen, René Ronnov-Jessen, Lone & Bissell, Mina J.
Object Type: Article
System: The UNT Digital Library