J. Marteau

Large liquid-scintillator trackers for neutrino experiments

Results are given on tests of large particle trackers for the detection of neutrino interactions in long-baseline experiments. Module prototypes have been assembled using TiO2-doped polycarbonate panels. These were subdivided into cells of 1c m 2 cross section and 6 m length, lled with liquid scintillator. A wavelength-shifting bre inserted in each cell captured a part of the scintillation light emitted when a cell was traversed by an ionizing particle. Two different bre-readout systems have been tested: an optoelectronic chain comprising an image intensier and an Electron Bombarded CCD (EBCCD); and a hybrid photodiode (HPD). New, low-cost liquid scintillators have been investigated for applications in large underground detectors. Testbeam studies have been performed using a commercially available liquid scintillator. The number of detected photoelectrons for minimum-ionizing particles crossing a module at dierent distances from the bre readout end was 6 to 12 with the EBCCD chain and a mirror at the non-readout end; 4 to 10 with the HPD and no mirror. The light-attenuation lengths in the bres were 9:4 m with the EBCCD and 6:4 m with the HPD. The detector response to electron showers has also been measured. After 10 radiation lengths of lead, the transverse position of the incoming electron was determined with a precision of a few millimeters for electrons of 4 GeV, and with a precision of 1.5 2.0 cm for electrons of 1 GeV.

Auto-triggerable HPD sensors fully readout on ethernet: applications for high-energy physics and medical imaging

Abstract The OPERA project is dedicated to neutrino oscillation search in the CNGS neutrino beam from CERN to Gran Sasso (Experimental Proposal, CERN/SPSC 2000-028, SPSC/P318, LNGS P25/2000, July 10, 2000). The experiment is designed to characterize the interactions of ν τ resulting of the ν μ →ν τ oscillation. The main element of the detector is a brick 10.2 cm ×12.8 cm cross-section consisting of 56 emulsion sheets 100 μm wide, interleaved with 1 mm lead plates. These bricks are assembled in walls of ∼7 m side. A total of 72 walls is foreseen for the OPERA experiment with a total fiducial mass of 2 ktons . When a neutrino interaction occurs, the tracks of the charged particles are recorded in the emulsions with a high accuracy and the topology of the event is fully reconstructed with an automatic scanning of the emulsions. The role of the target tracker in OPERA is to locate the brick where the primary neutrino interaction occurs, to provide triggers and to make a coarser reconstruction of the events. It consists of two planes of scintillator strips located after a brick wall. The scintillation photons are collected by WLS fibers and read by a multi-pixels photodetector. We present results obtained with 61 pixels HPDs readout by auto-triggerable front-end electronics of the VA–TA series. We have also developed a new kind of acquisition system based on Ethernet, able to read the front-end electronics and deliver the data directly to the Ethernet network. The full readout chain from the scintillator to the DAQ has been tested with cosmics and with beams from the CERN PS. The acquisition scheme is being proposed for the OPERA DAQ system and can be implemented for medical applications with various photodetectors. A prototype of micro-Positron Emission Tomograph (microPET) is being build on this scheme in collaboration with other Rhone–Alpes Institutes.