Development of high resolution and radiation hard electromagnetic calorimeter for the DVCS experiment

The electromagnetic calorimeter for the Deeply virtual Compton Scattering (DVCS) experiment requires high energy resolution and radiation hardness. The calorimeter for the experiment will be assembled using 1080 PbWO4 crystals supported by a carbon fiber structure. In order to achieve an energy resolution of ~ 1.3 % for 7 GeV gamma-rays, the thickness of the carbon structure was decided to be 0.5 mm based on Geant4 Monte-Carlo simulation. The detector will be operated in a harsh radiation environment (~ 5 Gy/hr), which will induce a severe decrease of the PbWO4 light transmission. For this reason, an optical bleaching method, based on the use of blue LEDs and quartz optical fiber will be used to regularly recover the crystals. For the radiation hard crystals, we found that the damage from 30 Gy of ionizing irradiation can be recovered by 2 hours of optical bleaching with 1 mm and 800 m diameter fibers. In this communication, we will present the current status of the detector R&D and construction, as well as simulation results of its performance

New scintillator materials for nuclear physics applications: an in-beam test at ALTO

International audienceA number of new instruments for particle and gamma detection have been built or are under development as part of the equipment of the new radioactive ion facilities that are under construction in Europe, as PARIS for SPIRAL2 at GANIL or CALIFA for FAIR at GSI. In this framework we are interested in studying new developed scintillators with advanced detection properties for application in nuclear physics. As a matter of fact in these latest years there is a renewed interest, in the chemistry and material science community, to search for new luminescent materials as real alternatives to LaBr3:Ce. Some new proposed scintillators, deserving close attention due to their promising detection features, have already been grown in cm3 scale samples, and thus in volumes suitable for our interest.In this communication we will report on the outcomes of the test in-beam at the ALTO (Accélérateur Lineaire et Tandem à Orsay) facility of several new scintillators, with both crystalline and transparent ceramic structure. In particular we studied the response of CeBr3, SrI2:Eu, CLYC and GYGAG:Ce, under high energy gamma irradiation produced in the nuclear reaction between the proton beam and light nuclei targets. Reactions induced by energetic protons on light targets lead to the emission of high-energy photons. In an in-beam campaign we can thus measure the scintillators energy resolution, light production and detection efficiency over a wide range of monochromatic gamma energies, up to 20 MeV, otherwise not available with standard radioactive sources

Differentiation of mouse plasmocytomas in vitro, two phenotypically stabilized variants of the same cell.

Mouse myelomas from Balb/c and C3H mice were established in tissue culture for more than 200 passages. When allowed to attach to a surface, they differentiated into two stabilized forms, one of which was fibroblast-shaped, grew without contact inhibition, and could be transplanted back to mice. The other had the morphology of epithelial cells, showed contact inhibition, and was not transplantable back to mice. For one strain (MOPC 173) it was demonstrated that both types of cells synthesize molecules with idiotypic determinants of the original myeloma protein. The relationship between the host cells and a leukemia-type virus present in the original tumor cells has been studied during different stages of cellular differentiation

Carbon wire chamber at sub-atmospheric pressure

International audiencePresent in many experiments, wire and drift chambers have been used in a large variety of shapes and configurations during the last decades. Nevertheless, their readout elements has not evolved much: tungsten, sometimes gold-plated or aluminum, wires. By taking advantage of the developments in the manufacture of conducting carbon fiber, we could obtain interesting improvements for wire detectors. In this article, we present recent tests and simulations using carbon fibers to readout signal in place of traditional tungsten wires. Unlike metallic wires, their low weight guaranties a reduced quantity of material in the active area

The CLAS12 Central Neutron Detector

The Central Neutron Detector is a scintillator barrel that was designed to detect 0.2-1 GeV neutrons at lab polar angles from 40 to 120 in the CLAS12 spectrometer in Hall B at Jefferson Laboratory. The design is based on three radial layers of paddles read out at the upstream end of the barrel by photomultipliers tubes. Neighboring paddles in each layer are coupled together at the downstream end of the barrel by “U-turn” light guides. The components of this detector are presented and the performance of the detector with the first beam data taken by CLAS12 is reported

The central neutron detector for CLAS12

The Central Neutron Detector, a recently constructed scintillator barrel which is used in CLAS12 at Jefferson Lab to detect 0.2–1 GeV neutrons at backwards angles, is here described. The motivations and R&D tests leading to its final design, based on three radial layers of coupled paddles with one-side light readout by photomultipliers plus “U-turn” lightguides on the other side, are outlined. The performance of the detector, evaluated from cosmic-ray tests and simulations, which satisfies the physics requirements, is reported

The 3He long-counter TETRA at the ALTO ISOL facility

International audienceA new ββ-decay station (BEDO) has been installed behind the PARRNe mass separator operated on-line at the electron-driven ALTO ISOL facility. The station is equipped with a movable tape collector allowing the creation of the radioactive sources of interest at the very center of a modular detection system. The mechanical structure was designed to host various assemblies of detectors in compact geometry. We report here the first on-line use of this system equipped with the 4π 3He neutron counter TETRA built at JINR Dubna associated with HPGe and plastic 4π β detectors. The single neutron detection efficiency achieved is 53(2)% measured using the 252Cf source. For β-delayed neutron measurements the neutron detection efficiency was derived from the comparison of gated γ-spectra. The on-line commissioning of the TETRA setup was performed with laser-ionized gallium beams. β and neutron events were recorded as a function of time. From these data we report P1n(82Ga)=22(2)% and T1/2T1/2(82Ga)=0.604(11) s in good agreement with values available in the literature. The new detection system will be used in other experiments aimed at investigations of β-decay properties of neutron-rich isotopes produced at ALTO