Simulation and evaluation of a new PET system based on liquid xenon as detection medium

présenté par J.P. CussoneauDue to its intrinsic physical properties, high density and atomic number, fast scintillation, high scintillation light yield and low ionization potential, liquid xenon is an excellent medium for the tracking and the accurate energy measurement of γ-rays in the MeV energy domain. The use of liquid xenon associated to a micro gap structure device[1] to measure 511 keV γ-rays in PET system is under investigation at Subatech. A Geant3 simulation of a full PET design made of lXe-TPC modules has been developed and the first estimations of the performances from a realistic detector are very promising: good overall sensitivity to 511 keV γ's (~ 93% for a 9 cm lXe module), good three-dimensional spatial resolution (250 µm FWHM, for first interaction vertex localization). The measurement of the 3 coordinates of the interaction vertices and the energy loss associated allow to reconstruct the correct Compton sequence of correlated annihilation γ-rays. Hence the capability to identify the first interaction vertex leads to major progresses in PET imaging: a parallax free PET tomograph with high detection sensitivity and spatial resolution. Moreover, such lXe-PET camera have an excellent rejection power on scattered events in 3D reconstruction mode

High-accuracy optical measurement of flatness for large objects

A high-accuracy non-contact optomechanical system has been designed for measuring the surface profile of relatively flat and large objects. The experimental set-up consists of a motorized gantry, a rangefinder, a CCD chip and a laser diode. This set-up permits discrete measurements to be performed on objects with a maximum plane surface area of 2.6 × 0.5 m2 along both the X and Y axes. Experiments were carried out on carbon sandwich panels. An uncertainty of ±8 µm has been obtained on flat and smooth surfaces; a ±30 µm uncertainty has been determined for a rough carbon sandwich panel

A new algorithm for large surfaces profiling by fringe projection

7 pagesA method for profiling surface objects based on the fringe projection method and a phase shifting algorithm is described. The application of this method to large surfaces is problematic since the calibration step requires the use of a reference plane as large as the object. A new algorithm based on least-squares method has also been developed to bypass this calibration step, and so the use of a reference plane. First experimental results on a carbon panel and on a parabolic aerial are presented to show the validity of the proposed algorithm. Accuracy of 1mm has been obtained for an object of 1m and 20 cm long, while sensitivity has been proved to be of the order of 100 m

First results on a sensor bio-inspired by electric fish

This article presents the first results of a work which aims at designing an active sensor inspired by the electric fish. Its interest is its potential for robotics underwater navigation and exploration tasks in conditions where vision and sonar would meet difficulty. It could also be used as a complementary omnidirectional, short range sense to vision and sonar. Combined with a well defined engine geometry, this sensor can be modeled analytically. In this article, we focus on a particular measurement mode where one electrode of the sensor acts as a current emitter and the others as current receivers. In spite of the high sensitivity required by electric sense, the first results show that we can obtain a detection range of the order of the sensor length, which suggests that this sensor principle could be used in future for robotics obstacle avoidance

Sensor model for the navigation of underwater vehicles by the electric sense

International audienceWe present an analytical model of a sensor for the navigation of underwater vehicles by the electric sense. This model is inspired from the electroreception structure of the electric fish. In our model, that we call the poly-spherical model (PSM), the sensor is composed of n spherical electrodes. Some electrodes play the role of current-emitters whereas others play the role of current-receivers. By imposing values of the electrical potential on each electrode we create an electric field in the vicinity of the sensor. The region where the electric field is created is considered as the bubble of perception of the sensor. Each object that enters this bubble is electrically polarized and creates in return a perturbation. This perturbation induces a variation of the measured current by the sensor. The model is tested on objects for which the expression of the polarizability is known. A unique off-line calibration of the poly-spherical model permits to predict the measured current of a real immersed sensor in an aquarium. Comparisons in a basic scene between the predicted current given by the poly-spherical model and the measured current given by our test bed show a very good agreement, which confirms the interest of using such fast analytical models for the purpose of navigation

Une plateforme pour l'analyse de matériaux par faisceaux d'ions à ARRONAX : Etude de l'effet d'humidité sur les échantillons

International audienceQuantification of soil pollution with method based on X-ray detection like X-Ray Fluorescence(XRF) suffers of multiple bias (moisture, surface state) especially when it's used for insituanalysis using portable-XRF. In order to study the effect of moisture on the results of ananalysis performed using X-Ray, we have performed studies using high energy PIXE/PIGE atthe ARRONAX. Samples were made of sand of different type. High energy PIXE/PIGE allowsus to avoid bias from surface state and to focus on moisture effect. It also allows to assessthe chemical composition of the sample. Results show a different behavior for each elementpresent in volcanic sand.</p

A proposal for a high performance γ\gamma-camera based on liquid Xenon converter and gaseous photomultiplier for PET

présenté par D. Ther

Coupled hologrammes

peer reviewedAmélioration des performances de composants optiques holographiques par couplage

Mesure de masse volumique de matériaux par rayons X pour le génie civil

International audienceThis study shows the feasibility of measuring the density of a material with an X-ray generator. X-rays are detected in transmission, with a shielded and collimated scintillator. The first measurements were made with homogeneous limestone and aluminium plates. An algorithm has also been developed to determine from the detected photons, the density of the material. The density was resolved with a good accuracy (<5%). The chemical composition was also determined but with lower accuracy (10%).</p

A double-laser diode onboard sensor for velocity measurements

In this paper, we validate the feasibility of an onboard velocity sensor using the self-mixing effect. Roughness of the target surface, wet target surface, noncontrolled changes of incident angle, and speed vector vertical components have been considered during this development. A first prototype has been designed with an automotive application so to illustrate this feasibility. This low-cost and low-clutter prototype presents an interesting basic performance (/spl sigma//spl ap/0.22%). In order to improve the accuracy as well as the robustness of the system, a double-laser diode sensor has then been tested successfully (/spl sigma//spl ap/0.038%) by removing the influence of the pitching and the pumping effects