Development of an Anger camera in Lanthanum Bromide for gamma-ray space astronomy in the MeV range

International audienceLanthanum bromide is a very promising scintillator material for the next generation of g-ray telescopes. We present in this paper first g-ray imaging results obtained by coupling a LaBr3 crystal with a position-sensitive 8×8 multianode photomultiplier tube to form a simple Anger camera module. The readout of the 64 signals is carried out with the most recent evolution of the MultiAnode ReadOut Chip (MAROC) which was initially designed for the luminometer of the ATLAS detector. Measured charge distributions are compared with detailed GEANT4 simulations that include the tracking of the optical photons produced in the scintillation crystal. The depth of interaction (d.o.i.) of 662-keV g-rays inside the crystal is derived from the charge distributions using an artificial neural network. We obtain for an irradiation at detector centre a mean standard deviation of the d.o.i. of 1.69 mm. Such a position-sensitive g-ray detector can form an innovative building block for a future space calorimete

The CPLEAR detector at CERN

The CPLEAR collaboration has constructed a detector at CERN for an extensive programme of CP-, T- and CPT-symmetry studies using ${\rm K}^0$ and $\bar{\rm K}^0$ produced by the annihilation of $\bar{\rm p}$'s in a hydrogen gas target. The ${\rm K}^0$ and $\bar{\rm K}^0$ are identified by their companion products of the annihilation ${\rm K}^{\pm} \pi^{\mp}$ which are tracked with multiwire proportional chambers, drift chambers and streamer tubes. Particle identification is carried out with a liquid Cherenkov detector for fast separation of pions and kaons and with scintillators which allow the measurement of time of flight and energy loss. Photons are measured with a lead/gas sampling electromagnetic calorimeter. The required antiproton annihilation modes are selected by fast online processors using the tracking chamber and particle identification information. All the detectors are mounted in a 0.44 T uniform field of an axial solenoid of diameter 2 m and length 3.6 m to form a magnetic spectrometer capable of full on-line reconstruction and selection of events. The design, operating parameters and performance of the sub-detectors are described.

On-line dialysis with HPLC for the automated preparation and analysis of amino acids, sugars and organic acids in grape juice and wines

A reproducible and high throughput technique is described for on-line clean-up and routine analysis of small molecules such as amino acids, sugars and organic acids in grape juice and wines. A fully automated sample processor (ASTED) provides an efficient way of preparing and cleaning-up raw liquid food samples. Following the usual preparation steps like dilution, addition of internal standards, mixing and derivatization, an on-line dialysis procedure is performed before HPLC analysis, to remove macromolecular and microparticulate interferents resulting from complex matrices. Eighteen amino acids, six organic acids, two sugars, ethanol and glycerol have been determined using two methods. Analytical data are provided both for a grape juice and a red wine

Specific photoaffinity labelling of a ferripyoverdin outer membrane receptor of Pseudomonas aeruginosa.

In order to identify and characterize the receptors involved in pyoverdin-mediated iron transport in Pseudomonas aeruginosa ATCC 15692, a photoactivatable siderophore has been synthesized. In the dark, this probe is stable and is able to promote iron transport at the same rate as the native pyoverdin. Under irradiation at 312 nm, the molecule is photodecomposed and a clear inhibition of the iron transport is observed. With the radioactive form of this photoactivatable probe, we were able to visualize on a SDS-PAGE gel a labelled protein of approximately 90 kDa molecular mass, which is very likely the FpvA receptor or a yet unknown pyoverdin receptor

Development of a 3D-Imaging Calorimeter in Lanthanum Bromide for Gamma-Ray Space Astronomy

International audienceGamma-ray astronomy, in the energy range from 0.1 up to 100 MeV, holds many understudied questions connected with stellar nucleosynthesis, the Sun, neutron stars and black holes. To access the physics behind, a significant increase in instrumental sensitivity, compared to previous missions, e.g. NASA/CGRO and ESA/INTEGRAL, is needed. One of the promising concepts is an Advanced Compton telescope. It has good discovery potential and is able to avoid problems like high background in the MeV energy band. Under the project of creating a prototype of such instrument, we study cerium-doped lantanum(III) bromide (LaBr3:Ce) inorganic scintillator. Its internal qualities, especially good energy resolution and radiation tolerance, make it a smart choice for the calorimeter part of a future spaceborne telescope. At CSNSM Orsay, we have created a new detection module from 5x5 cm2 area and 1 cm thick LaBr3:Ce crystal scintillator coupled to 64 channel multi-anode photomultiplier and read out by the ASIC MAROC, used previously for the luminometer of the ATLAS detector (CERN). Characterization, thorough measurements with various radioactive sources, as well as, single photoelectron detection have been done. Furthermore, we made a comparison with the detailed GEANT4 based simulation including tracking of the optical photons. Finally, we have studied the 3D reconstruction of the first interaction point of incident gamma-ray, utilizing a neural network algorithm. This spatial position resolution plays a crucial part in the future implementations and together with the other measured properties makes our detector module very interesting for the next generation of space telescopes operating in the MeV range