The reconstruction of Ni and Rh (001) surfaces upon Carbon, Nitrogen, or Oxygen adsorption

Nickel and Rhodium (001) surfaces display a similar - as from STM images - clock reconstruction when half a monolayer of C/Ni, N/Ni or O/Rh is adsorbed; no reconstruction is observed instead for O/Ni. Adsorbate atoms sit at the center of the black squares of a chess-board, $c(2\times 2)$, pattern and two different reconstructions are actually compatible with the observed STM images - showing a $(2\times 2)p4g$ pattern - according to whether a rotation of the black or white squares occurs. We report on a first - principles study of the structure of X/Ni(001) and X/Rh(001) surfaces (X=C,N,O) at half a monolayer coverage, performed using density-functional theory. Our findings are in agreement with all available experimental information and shed new light on the mechanisms responsible for the reconstructions. We show that the same substrate may display different reconstructions - or no reconstruction - upon adsorption of different atomic species, depending on the relative importance of the chemical and steric factors which determine the reconstruction.Comment: 18 pages, 5 figure

A First Mass Production of Gas Electron Multipliers

We report on the manufacture of a first batch of approximately 2,000 Gas Electron Multipliers (GEMs) using 3M's fully automated roll to roll flexible circuit production line. This process allows low-cost, reproducible fabrication of a high volume of GEMs of dimensions up to 30$\times$30 cm$^{2}$. First tests indicate that the resulting GEMs have optimal properties as radiation detectors. Production techniques and preliminary measurements of GEM performance are described. This now demonstrated industrial capability should help further establish the prominence of micropattern gas detectors in accelerator based and non-accelerator particle physics, imaging and photodetection.Comment: 11 pages, 10 figures, to be submitted to Nucl. Instr. Meth.

Polarization Observables for Two-Pion Production off the Nucleon

We develop polarization observables for the processes $\gamma N\to\pi\pi N$ and $\pi N\to\pi\pi N$, using both a helicity and hybrid helicity-transversity basis. Such observables are crucial if processes that produce final states consisting of a spin-1/2 baryon and two pseudoscalar mesons are to be fully exploited for baryon spectroscopy. We derive relationships among the observables, as well as inequalities that they must satisfy. We also discuss the observables that must be measured in `complete' experiments, and briefly examine the prospects for measurement of some of these observables in the near future.Comment: 20 pages, using revtex

Summary of time requirements and potential improvements for Marine Recorder data entry.

The contract work has demonstrated that older data can be assessed and entered into the MR format. Older data has associated problems but is retrievable. The contract successfully imported all datasets as required. MNCR survey sheets fit well into the MR format. The data validation and verification process can be improved. A number of computerised short cuts can be suggested and the process made more intuitive. Such a move is vital if MR is to be adopted as a standard by the recording community both on a voluntary level and potentially by consultancies

Imaging Gaseous Detector based on Micro Processing Technology

The development of gaseous detectors has been exciting again since the appearance of a MicroStrip Gas Chamber(MSGC) in 1988, which is made using a micro-electronics technology. These days lots of variations of the advanced gaseous detectors are being intensively studied in the world. We have developed the two-dimensional MSGC having a 10 cm square detection area and the ultra fast readout system for a real time X-ray imaging. The MSGC was made using Multi-Chip Module (MCM) technology, and has a very thin substrate of 17 $\mu$m, lots of thin anodes and back strips both with 200 $\mu$m pitches. This enables us to get fast digital X-ray images with recording both the timing and an energy of each X-ray photon. In addition, an intermediate gas multiplier has been realized using a capillary plate having a conductive surface of a capillary. The MSGC combined with the conductive capillary plate can be steadily operated with a high gain under intense irradiation. Here we also report new approaches of X-ray crystal structure analyses using timing information obtained by the MSGC.Comment: 14 papges, 10 figures, to appear in the proceedings of Solid State Detectors for 21st Century (Nucl. Instru. and Meth. A

An exploratory qualitative study of values issues associated with training and practice in pluralistic counselling

Background: A pluralistic model of practice has become increasingly influential in recent years. A distinctive feature of this approach is its explicit grounding within a philosophical and moral perspective.Aim: The aim of this study was to investigate issues and challenges that pluralistic counsellors experience in relation to values dilemmas that arise in practice.Methodology: Twelve practitioners, of various experience levels, who identified as pluralistic counsellors, were invited to take part in semi-structured interviews. Transcripts were analysed using a method of thematic analysis.Findings: Participants viewed their personal values to be compatible with the values that they perceived pluralistic counselling to hold, and reported that they chose pluralism as a modality because they found a similarity between their personal values and the values of pluralistic counselling. Core values associated with pluralistic practice included the following: the importance of connection, ‘there is no one right way to be’, equality (not taking an expert role), honesty, and willingness to make use of research evidence. Participants also described value dilemmas, and their use of supervision in dealing with value issues.Implications: The implications of these findings for training, research and practice are discussed

Simulation study of electron drift and gas multiplication in Micro Pixel Chamber

The physical processes of charge collection and gas multiplication of a Micro Pixel Chamber (mu-PIC) were studied in detail using a three-dimensional simulation. The collection efficiencies of primary electrons and gas multiplication factors were calculated for several electrode structures. Based on those studies, we analyzed the optimization of the electrode structure of the mu-PIC, in order to obtain a high gas gain of more than 10^4 and a simultaneous suppression of discharges. Consequently, we found that these characteristics strongly depend on the substrate thickness and the anode diameter of the mu-PIC. In addition, a gas gain of 10^5 would be expected for a mu-PIC having a thick substrate of > 150um.Comment: 16 pages, 14 figures, Submitted to Nucl. Instr. Methods

Comparison of CDMS [100] and [111] oriented germanium detectors

The Cryogenic Dark Matter Search (CDMS) utilizes large mass, 3" diameter $\times$ 1" thick target masses as particle detectors. The target is instrumented with both phonon and ionization sensors and comparison of energy in each channel provides event-by-event classification of electron and nuclear recoils. Fiducial volume is determined by the ability to obtain good phonon and ionization signal at a particular location. Due to electronic band structure in germanium, electron mass is described by an anisotropic tensor with heavy mass aligned along the symmetry axis defined by the [111] Miller index (L valley), resulting in large lateral component to the transport. The spatial distribution of electrons varies significantly for detectors which have their longitudinal axis orientations described by either the [100] or [111] Miller indices. Electric fields with large fringing component at high detector radius also affect the spatial distribution of electrons and holes. Both effects are studied in a 3 dimensional Monte Carlo and the impact on fiducial volume is discussed.Comment: Low Temperature Detector 14 conference proceedings to be published in the Journal of Low Temperature Physic

Surface relaxation and ferromagnetism of Rh(001)

The significant discrepancy between first-principles calculations and experimental analyses for the relaxation of the (001) surface of rhodium has been a puzzle for some years. In this paper we present density functional theory calculations using the local-density approximation and the generalized gradient approximation of the exchange-correlation functional. We investigate the thermal expansion of the surface and the possibility of surface magnetism. The results throw light on several, hitherto overlooked, aspects of metal surfaces. We find, that, when the free energy is considered, density-functional theory provides results in good agreement with experiments.Comment: 6 pages, 4 figures, submitted to Phys. Rev. Lett. (April 28, 1996