Sensor Simulation and position calibration for the CMS pixel detector

In this paper a detailed simulation of irradiated pixel sensors was used to investigate the effects of radiation damage on charge sharing and position determination. The simulation implements a model of radiation damage by including two defect levels with opposite charge states and trapping of charge carriers. We show that charge sharing functions extracted from the simulation can be parameterized as a function of the inter-pixel position and used to improve the position determination. For sensors irradiated to Phi=5.9x10^14 n/cm^2 a position resolution below 15 um can be achieved after calibration.Comment: Presented at the 14th Int. Workshop on Vertex Detectors (Vertex 2005), November 7-11 2005, Chuzenji Lake, Nikko, Japan. 4 pages, 1 figur

Statistical Uncertainties in Temperature Diagnostics for Hot Coronal Plasma Using the ASCA SIS

Statistical uncertainties in determining the temperatures of hot (0.5 keV to 10 keV) coronal plasmas are investigated. The statistical precision of various spectral temperature diagnostics is established by analyzing synthetic ASCA Solid-state Imaging Spectrometer (SIS) CCD spectra. The diagnostics considered are the ratio of hydrogen-like to helium-like line complexes of $Z\ge14$ elements, line-free portions of the continuum, and the entire spectrum. While fits to the entire spectrum yield the highest statistical precision, it is argued that fits to the line-free continuum are less susceptible to atomic data uncertainties but lead to a modest increase in statistical uncertainty over full spectral fits. Temperatures deduced from line ratios can have similar accuracy but only over a narrow range of temperatures. Convenient estimates of statistical accuracies for the various temperature diagnostics are provided which may be used in planning ASCA SIS observations.Comment: postscript file of 8 pages+3 figures; 4 files tarred, compressed and uuencoded. To appear in the Astrophysical Journal Letters; contents copyright 1994 American Astronomical Societ

Cataphoresis in rotating electric fields

A new method of making cataphoresis measurements on colloid particles has been developed and tested. The method makes use of a rotating electric field which causes the particles to move in circles. In this way it is easily possible to test the effect of variable speed of the particle on the distribution of the diffuse electric double layer surrounding it. The results obtained indicate that this effect is negligible. Furthermore, it has been discovered that the mobility of the small particles (below 10^-4 cm in diameter) fluctuates widely and this is made very evident to the eye by the fluctuations in the circular paths of the particles. The fluctuations are quite violent with particles as small as 10^-6 cm in diameter. Considerable study of these variations has been made as well as an attempt to explain them qualitatively

Voltage controlling mechanisms in low resistivity silicon solar cells: A unified approach

An experimental technique capable of resolving the dark saturation current into its base and emitter components is used as the basis of an analysis in which the voltage limiting mechanisms were determined for a variety of high voltage, low resistivity silicon solar cells. The cells studied include the University of Florida hi-low emitter cell, the NASA and the COMSAT multi-step diffused cells, the Spire Corporation ion-implanted emitter cell, and the University of New South Wales MINMIS and MINP cells. The results proved to be, in general, at variance with prior expectations. Most surprising was the finding that the MINP and the MINMIS voltage improvements are due, to a considerable extent, to a previously unrecognized optimization of the base component of the saturation current. This result is substantiated by an independent analysis of the material used to fabricate these devices

Direct Determination of the Kinetics of Oxygen Diffusion to the Photocytes of a Bioluminescent Elaterid Larva, Measurement of Gas- and Aqueous-Phase Diffusional Barriers and Modelling of Oxygen Supply

We describe the development and use of a direct kinetic technique to determine the time taken for oxygen to diffuse from the external environment into the light-producing cells (photocytes) in the prothorax of bioluminescent larvae of Pyrearinus termitilluminans. This was achieved by measuring the time course of the pseudoflash induced through sequential anoxia followed by normoxia. We have also determined the separate times taken for this oxygen diffusion in gaseous and tissue (predominantly aqueous) phases by using helium and nitrogen as the carrier gas. Of the total time taken for diffusion, that in the gas phase required 613+/-136 ms (mean +/- s.e. m., N=5) whilst that in the aqueous phase required 1313+/-187 ms. These values imply pathlengths of diffusion in the gaseous and aqueous phases of 4.80x10(-)(3)+/-0.53x10(-)(3) and 8. 89x10(-)(5)+/-0.61x10(-)(5 )m, respectively. In addition, the pathlength of gas-phase diffusion was used to derive a parameter relating to the tortuosity of the tracheal system. These values, together with those obtained upon bioluminescent oxygen consumption, have been used to model oxygen supply to the photocyte. From these studies, it would also appear that the modulation of tracheolar fluid levels might be a significant mechanism of control of tissue oxygen levels in at least some insects

Comparative performance of diffused junction indium phosphide solar cells

A comparison is made between indium phosphide solar cells whose p-n junctions were processed by open tube capped diffusion, and closed tube uncapped diffusion, of sulfur into Czochralski grown p-type substrates. Air mass zero, total area, efficiencies ranged from 10 to 14.2 percent, the latter value attributed to cells processed by capped diffusion. The radiation resistance of these latter cells was slightly better, under 1 MeV electron irradiation. However, rather than being process dependent, the difference in radiation resistance could be attributed to the effects of increased base dopant concentration. In agreement with previous results, both cells exhibited radiation resistance superior to that of gallium arsenide. The lowest temperature dependency of maximum power was exhibited by the cells prepared by open tube capped diffusion. Contrary to previous results, no correlation was found between open circuit voltage and the temperature dependency of Pmax. It was concluded that additional process optimization was necessary before concluding that one process was better than another

Lattice-dynamics of a Disordered solid-solid Interface

Generic properties of elastic phonon transport at a disordered interface are studied. The results show that phonon transmittance is a strong function of frequency and the disorder correlation length. At frequencies lower than the van Hove singularity the transmittance at a given frequency increases as the correlation length decreases. At low frequencies, this is reflected by different power-laws for phonon conductance across correlated and uncorrelated disordered interfaces which are in approximate agreement with perturbation theory of an elastic continuum. These results can be understood in terms of simple mosaic and two-colour models of the interface.Comment: 17 pages, 5 figures, submitted to PR

Mekong Basin Focal Project: Synthesis report

The Mekong Basin Focal Project aims were to assess water use, water productivity and water poverty in the basin, and analyse the opportunities and risks of change in water management that influences water poverty. The main issue facing the Lower Mekong is not water availability (except for seasonally in certain areas such as northeast Thailand) but the impact of changed flows (which may result from dam or irrigation development or climate change) on ecology, fish production, access to water and food security. Poverty is generally decreasing in the Mekong, but the poorer people are not sharing in the improvements. Water governance and sharing of benefits is a key challenge for the Mekong

Prelude to the Anthropocene: Two new North American Land Mammal Ages (NALMAs)

Human impacts have left and are leaving distinctive imprints in the geological record. Here we show that in North America, the human-caused changes evident in the mammalian fossil record since c. 14,000 years ago are as pronounced as earlier faunal changes that subdivide Cenozoic epochs into the North American Land Mammal Ages (NALMAs). Accordingly, we define two new North American Land Mammal Ages, the Santarosean and the Saintagustinean, which subdivide Holocene time and complete a biochronologic system that has proven extremely useful in dating terrestrial deposits and in revealing major features of faunal change through the past 66 million years. The new NALMAs highlight human-induced changes to the Earth system, and inform the debate on whether or not defining an Anthropocene epoch is justified, and if so, when it began