The Level 0 Trigger Decision Unit for the LHCb experiment

The Level 0 Decision Unit (L0DU) is one of the main components of the first trigger level (named level 0) of the LHCb experiment. This 16 layers custom board receives data from the calorimeter, muon and pile-up sub-triggers and computes the level 0 decision, reducing the rate from 40MHz to 1MHz. The processing is implemented in FPGA using a 40MHz synchronous pipelined architecture. The L0DU algorithm is fully configured via the Experiment Control System without any firmware reprogramming. An overall L0DU latency of less than 450ns has been achieved. The board was installed in the experimental area in April 2007 and since then has played a major role in the commissioning of the experiment

Generalized Sagnac Effect

Experiments were conducted to study light propagation in a light waveguide loop consisting of linearly and circularly moving segments. We found that any segment of the loop contributes to the total phase difference between two counterpropagating light beams in the loop. The contribution is proportional to a product of the moving velocity v and the projection of the segment length Deltal on the moving direction, Deltaphi=4pivDeltal/clambda. It is independent of the type of motion and the refractive index of waveguides. The finding includes the Sagnac effect of rotation as a special case and suggests a new fiber optic sensor for measuring linear motion with nanoscale sensitivity.Comment: 3 pages (including 3 figures

A New Method to Extract Piezoresistive Coefficients in Polysilicon Through Gauges Placed on a MEMS Membrane

AbstractThis paper presents a new method to evaluate piezoresistive coefficients of polysilicon in the case of N-doping but valid for other types. We measured and simulated the mechanical stress profile distribution along a bossed membrane using several gauges placed along the radial axis of round membranes. Pressure was applied to the membrane. The electromechanical characterizations of the MEMS membrane are in accordance with the simulations and allowed to extract piezoresistive coefficients of the heavily doped polysilicon

Individual and collective stock dynamics: intra-day seasonalities

We establish several new stylised facts concerning the intra-day seasonalities of stock dynamics. Beyond the well known U-shaped pattern of the volatility, we find that the average correlation between stocks increases throughout the day, leading to a smaller relative dispersion between stocks. Somewhat paradoxically, the kurtosis (a measure of volatility surprises) reaches a minimum at the open of the market, when the volatility is at its peak. We confirm that the dispersion kurtosis is a markedly decreasing function of the index return. This means that during large market swings, the idiosyncratic component of the stock dynamics becomes sub-dominant. In a nutshell, early hours of trading are dominated by idiosyncratic or sector specific effects with little surprises, whereas the influence of the market factor increases throughout the day, and surprises become more frequent.Comment: 9 pages, 7 figure

Coherent Diffraction Radiation experiment at CTF3—Simulation studies

A two-target model was developed for the simulations of Coherent Diffraction Radiation (CDR) phenomenon for the experiment at the CLIC Test Facility 3 (CTF3 at CERN). The model is based on a classical DR theory. The radiation distribution from the targets, as a function of the angle and the frequency, was calculated for the first and the second target separately in order to understand how the final radiation distribution from the two targets, working as a system, is formed. The final radiation distribution of destructive interference between the two targets was obtained as well. The distributions were calculated for the working parameters of both the CTF3 and the experimental setup and were used for a single-electron spectrum calculation, required for the bunch profile reconstruction

Modeling the martian atmosphere with the LMD global climate model

Introduction: For several years we have been developing a 3D Global Climate Model (GCM) for Mars derived from the models used on Earth for weather forecasting or climate changes studies [1]. The purpose of such a project is ambitious: we wish to build a 'Mars simulator' based only on physical equations, with no tailor-made forcing, but able to reproduce all the available observations of the Martian climate (temperatures, winds, but also clouds, dust, ices, chemical species, etc...). The GCM is constantly evolving, thanks to a contnuous collaboration between several teams based in France (LMD, SA), the UK (The Open University, University of Oxford) and Spain (Instituto de Astrofisica de Andalucia), and with the support of ESA and CNES. We are currently working on an improved version of the model. Several new parametrisation are included in the heart of the model (radiative transfer, surface and subsurface processes, dynamics) and the applications of the GCM are in contnuous development (Water, dust, CO2, radon cycles, photochemistry, thermosphere, ionosphere, etc...

2-Dust : a Dust Radiative Transfer Code for an Axisymmetric System

We have developed a general purpose dust radiative transfer code for an axisymmetric system, 2-Dust, motivated by the recent increasing availability of high-resolution images of circumstellar dust shells at various wavelengths. This code solves the equation of radiative transfer following the principle of long characteristic in a 2-D polar grid while considering a 3-D radiation field at each grid point. A solution is sought through an iterative scheme in which self-consistency of the solution is achieved by requiring a global luminosity constancy throughout the shell. The dust opacities are calculated through Mie theory from the given size distribution and optical properties of the dust grains. The main focus of the code is to obtain insights on (1) the global energetics of dust grains in the shell (2) the 2-D projected morphologies that are strongly dependent on the mixed effects of the axisymmetric dust distribution and inclination angle of the shell. Here, test models are presented with discussion of the results. The code can be supplied with a user-defined density distribution function, and thus, is applicable to a variety of dusty astronomical objects possessing the axisymmetric geometry.Comment: To be published in ApJ, April 2003 issue; 13 pages, 4 tables, 17 figures, 5-page appendix (no figures for the main text included in this preprint). For the complete preprint and code distribution, contact the author