Search

We present a design study of PIXSIC, a new β+ radiosensitive microprobe implantable in rodent brain dedicated to in vivo and autonomous measurements of local time activity curves of beta radiotracers in a small (a few mm³) volume of brain tissue. This project follows the initial β microprobe previously developed at IMNC, which has been validated in several neurobiological experiments. This first prototype has been extensively used on anesthetized animals, but presents some critical limits for utilization on awake and freely moving animals. Consequently, we propose to develop a wireless setup that can be worn by an animal without constraints upon its movements. To that aim, we have chosen a Silicon-based detector, highly β sensitive, which allows for the development of a compact pixellated probe (typically 600 x 200 x 1000 µm³), read out with miniaturized wireless electronics. Using Monte-Carlo simulations, we show that high resistive Silicon pixels are appropriate for this purpose, assuming that the pixel dimensions are adapted to our specific signals. More precisely, a tradeoff has to be found between the sensitivity to β+ particles and to the 511 keV γ background resulting from annihilations of β+ with electrons. We demonstrate that pixels with maximized surface and minimized thickness can lead to an optimization of their β+ sensitivity with a relative transparency to the annihilation background. [ABSTRACT FROM AUTHOR]

Results obtained using a hybrid pixel photon-counting detector in powder diffraction experiments are presented. The detector works at room temperature and its dynamic response ranges from 0.01 photons pixel−1 s−1 up to 106 photons pixel−1 s−1. The pixel sizes are 0.33 mm × 0.33 mm for a total area of 68 mm × 68 mm. On recording high-resolution diffraction patterns of powders, a reduction of the experimental time by more than a factor of 20 is obtained without loss of data quality. The example of an X-zeolite shows that such detectors can be used for very demanding anomalous experiments. In situ experiments of quenching liquid oxides show that frames of 0.01 s can be achieved for studying such processes. [ABSTRACT FROM AUTHOR]

Currently available 2D detectors do not make full use of the high flux and high brilliance of third generation synchrotron sources. The XPAD prototype, using active pixels, has been developed to fulfill the needs of materials science scattering experiments. At the time, its prototype is build of eight modules of eight chips. The threshold calibration of ≈ 4 10´ pixels is discussed. Applications to powder diffraction or SAXS experiments prove that it allows to record high quality data. [ABSTRACT FROM AUTHOR]

Presents results obtained from a prototype photon counting detector with large dynamic range. Pixel size; Dynamic response range; Energy resolution; Small-angle X-ray scattering (SAXS) and diffraction patterns.

Deals with a study which investigated the use of several detector planes made from chemical vapir deposition (CVD) diamond strip sensors for charged particle tracking. Information on CVD diamond strip detectors; Telescope experimental set-up in the beam; Beam test results.

Focuses on the development of a pixel detector for X-ray crystallography. Special features of the X-ray detector; Advantages and disadvantages of pixel versus charge-coupled devices; Characteristics and test results of an electronic chip for a pixel detector.

In working out a realistic long-term scenario for the operational conditions for the innermost silicon layers, it is usually assumed that the upper safe margin for the reverse-bias voltage is around 200 V. Lifetime of the detectors, and consequently total cost of the tracker are directly related to this value. Using pixel test structures, manufactured by CSEM in the same technology as DELPHI pixel detectors, we performed a study of maximum tolerable bias voltages on nonirradiated detectors, and on detectors which have received different fluences of pions, protons and neutrons. A special test was also done with detectors, continuously irradiated on a testbench with a Sr source, at a rate about 13 krad/h. [ABSTRACT FROM AUTHOR]

Direct photon production has been studied by an experiment performed with the NA3 spectrometer at CERN, using incident negative and positive beams at 200 GeV/c interacting with an isoscalar Carbon target. Two different triggers have been used; one of them requires the photon conversion. The experiment is sensitive to direct photons produced with 3.0≦ P≦6 GeV/c and center-of-mass rapidity −0.4≦ y≦1.2. Inclusive cross sections are given for incident π and protons, and compared with second order QCD predictions; finally an estimation of the gluon structure function of the nucleon is given. [ABSTRACT FROM AUTHOR]

A sensitive search has been done for the production of new long-lived and penetrating particles by 300 GeV/c negative pions. No new state -decaying into at least two charged known particles -has been detected with mass above 1 GeV/c and lifetime in the range 5·10 s to 5·10s. We give upper limits on production cross sections, and consequences on the existence of heavy 'axion-like' particles, heavy neutrinos and supersymmetric particles. In particular, this experiment excludes the existence of light gluinos with lifetime in the range 5·10 to 10s: this closes the last 'window of opportunity' for gluinos with M<2 GeV/c and lifetime measurable in particle physics experiments. [ABSTRACT FROM AUTHOR]

We have measured the inclusive cross-section for π production at large transverse momentum by 200 GeV/c positive and negative hadron beams on Carbon targets (2.9< P<6 GeV/c; −0.4< y<1.2). We used the NA3 spectrometer at the CERN SPS. [ABSTRACT FROM AUTHOR]

We present the analysis of ∼30,000 high mass dimuons ( M>4.5 GeV/c) produced in 400 GeV/c proton-platinum interactions. A determination of the K-factor is given for different values of x and M, and its variations are compared to QCD predictions. The proton structure functions derived from these events are compared to the values obtained in deep inelastic lepton scattering. [ABSTRACT FROM AUTHOR]

A detailed study of J/ ψ hadronic production has been performed in a high statistics experiment (more than 1.5 10 J/ ψ observed in their dimuon decay mode). Data have been taken with incident π, K, p, on hydrogen and platinum targets, at 150, 200 and 280 GeV/c. We find from the observed nuclear dependance of the cross sections, that about 18% of the J/ ψ are produced diffractively. Using known structure functions of the quarks in the nucleon and in the pion, we derive estimations for the gluon structure functions. [ABSTRACT FROM AUTHOR]

We have studied high statistics samples of dimuon events (∼35,000) produced from π on platinum target in the mass interval 4.2≦ M≦8.5 GeV at 150, 200 and 280 GeV/c. The π structure function is obtained by a fit of dσ/ dx dx to π and π data. At 200 GeV, the simultaneous use of π and π data allows a separate determination of the valence and sea structure functions of the π. Furthermore, the 150 and 280 GeV data allow an accurate determination of the shape of the valence structure function and give an estimate of its evolution between Q=25 and 50 GeV. [ABSTRACT FROM AUTHOR]

From π interactions at 150 GeV/c on a heavy target, we present the final analysis of the dimuon decay angular distribution in the mass interval 4.5-8.5 GeV/c. Results are presented and discussed in various reference frames and are also given in terms of the density matrix elements. Finally the possible contribution of higher-twist effects at large x is discussed; we find that our data are not compatible with higher twist contributions as proposed by the Berger and Brodsky Model. [ABSTRACT FROM AUTHOR]

Chemical Vapor Deposition (CVD) diamond has been discussed extensively as an alternative sensor material for use very close to the interaction region of the LHC and other machines where extreme radiation conditions exist. During the last seven years the RD42 collaboration has developed diamond detectors and tested them with LHC electronics towards the end of creating a device usable by experiments. The most recent results of this work are presented. Recently, a new form of CVD diamond has been developed: single crystal CVD diamond which resolves many of the issues associated with poly-crystalline CVD material. The first tests of this material are also presented. [ABSTRACT FROM AUTHOR]

Presents a study which constructed a large surface semiconductor photon counting pixel detector. Creation of the first prototypes of the X-ray pixel detector; Electronic chip results; Prototype test results.