High Resolution RPC's for Large TOF Systems

Here we report on a particular type of RPC that presents up to 99% efficiency for minimum ionizing particles and a very sharp time resolution, below 50 ps sigma in the most optimized conditions. Our 9 cm2 cells, made with glass and metal electrodes that form accurately spaced gaps of a few hundred micrometers, are operated at atmospheric pressure in non-flammable gases and can be economically produced in large quantities, opening perspectives for the construction of large area time of flight systems.Comment: 10 pages, 8 figure

The Role of Volunteered Geographic Information towards 3D Property Cadastral Systems (2): A Purpose Driven Web Application

VGI has not proved to be readily suitable to replace well-established accurate methods and technologies such as those of full standard cadastral surveys. Even so, VGI potentialities as relevant source of geospatial data have been widely acknowledged. As such, some authors have defended that VGI may in fact play an important role such as at a local cadastral jurisdiction level towards local spatial data infrastructures. As far as property cadastre is concerned, the full extent 3D complexity inside a property is in many instances only known to their occupants, thus making crowd sourcing perhaps the only economically feasible approach for its capture. While the crowd cannot be expected to conduct a full cadastral survey, it may be possible to ask them to indicate at least the location of complex 3D situations and thus to facilitate local authorities’ understanding of the extent of some cadastral issues. As such, it was argued in our previous work that geoinformation from the crowd might in fact be taken into account as an interim step before a full surveyed 3D cadastre is eventually achieved. As such, possible room for VGI in the context of 3D cadastre was discussed, and a hierarchical framework of levels of data acquisition to be used at local cadastral jurisdiction level was proposed. Such framework is revisited in this paper.Given context above, this paper focuses primarily on two aspects. Firstly, to review technical requirements of the official cadastral process in Portugal in order to identify which sorts of cadastral data are likely to be acquirable/not acquirable through VGI. Secondly, to design and to implement the prototype of a web-based application (IGV3Dcad) envisaged for general public usage to flag different land and property ownership situations. Having information about the extent of the 2D/3D issue is also fundamental to making a decision as to whether a 3D cadastral approach is actually needed and hence to further invest resources in even more expensive 3D survey

Optical Relative Calibration and Stability Monitoring for the Auger Fluorescence Detector

The stability of the fluorescence telescopes of the Pierre Auger Observatory is monitored with the optical relative calibration setup. Optical fibers distribute light pulses to three different diffuser groups within the optical system. The total charge per pulse is measured for each pixel and compared with reference calibration measurements. This allows monitoring the short and long term stability with respect of the relative timing between pixels and the relative gain for each pixel. The designs of the LED calibration unit (LCU) and of the Xenon flash lamp used for relative calibration, are described and their capabilities to monitor the stability of the telescope performances are studied. We report the analysis of relative calibration data recorded during 2004. Fluctuations in the relative calibration constants provide a measure of the stability of the FD.Comment: 4 pp. To appear in the proceedings of 29th International Cosmic Ray Conference (ICRC 2005), Pune, India, 3-11 Aug 200

Study and optimization of RPCs for high rate applications

Due to the low cost, good time resolution and the properties of RPCs with respect to electronics damage protection, they are chosen for many large experiments. These detectors are reliable and stable in their operation with counting rates up to kHz/cm2. The aim of this work is to understand the fundamental rate limits of RPCs in order to find an efficient way for their optimization and hence, extend their applications. Several types of materials have been used and operational parameters have been optimized in this work comprising simulations and experiment. High efficiency, excellent position resolution, low noise and high rate capability is demonstrated. These type of RPCs open new avenues in several applications, for example in crystallography, biology and medicine

MARTA: A high-energy cosmic-ray detector concept with high-accuracy muon measurement

A new concept for the direct measurement of muons in air showers is presented. The concept is based on resistive plate chambers (RPCs), which can directly measure muons with very good space and time resolution. The muon detector is shielded by placing it under another detector able to absorb and measure the electromagnetic component of the showers such as a water-Cherenkov detector, commonly used in air shower arrays. The combination of the two detectors in a single, compact detector unit provides a unique measurement that opens rich possibilities in the study of air showers.Comment: 11 page

The ground state of the Lithium atom in strong magnetic fields

The ground and some excited states of the Li atom in external uniform magnetic fields are calculated by means of our 2D mesh Hartree-Fock method for field strengths ranging from zero up to 2.35 10^8 T. With increasing field strength the ground state undergoes two transitions involving three different electronic configurations: for weak fields the ground state configuration arises from the field-free 1s^22s configuration, for intermediate fields from the 1s^22p_{-1} configuration and in high fields the 1s2p_{-1}3d_{-2} electronic configuration is responsible for the properties of the atom. The transition field strengths are determined. Calculations on the ground state of the Li+ ion allow us to describe the field-dependent ionization energy of the Li atom. Some general arguments on the ground states of multi-electron atoms in strong magnetic fields are provided.Comment: 11 pages, 6 figures, submitted to Physical Review

A large area timing RPC prototype for ion collisions in the HADES spectrometer

We present a resistive plate chamber (RPC) prototype for time-of-flight measurements over large areas and at high occupancies, minimizing the inter-channel cross-talk.http://www.sciencedirect.com/science/article/B6TJM-4D75GPD-9/1/a6fe40c114a867a0f98e2fec0f13350

A four gap glass RPC time-of-flight array with 90 ps time resolution

In this work we describe the performance of a prototype developped in the context of the ALICE team-of-flight R&D system. The detector module consists of a 32-channel array of 3 x 3 cm2 glass-RPC cells, each of which has four accurately spaced gaps of 0.3. mm thickness arranged as a pair of double-gap resistive plate chambers. Operated with a non-flammable gas mixture at atmospheric pressure, the system achieved a time resolution of 90 ps at 90% efficiency with good uniformity and moderate crosstalk. This result shows the feasibility of large-area, high resolution time-of-flight systems based on RPCs at affordable cost