Large liquid-scintillator trackers for neutrino experiments

Abstract

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 TiO 2 -doped polycarbonate panels. These were subdivided into cells of ∼ 1 cm 2 cross section and 6 m length, filled with liquid scintillator. A wavelength-shifting fibre inserted in each cell captured a part of the scintillation light emitted when a cell was traversed by an ionizing particle. Two different fibre-readout systems have been tested: an optoelectronic chain comprising an image intensifier 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 different distances from the fibre 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 fibres 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.

Strip detectors for a portal monitor application

“…This effect of strip dimensions on fiber light output was investigated using liquid scintillators and WLS fibers. This decrease of light output as strip width increases is well reproduced by a Monte-Carlo simulation and was measured using three different cell sizes W s (11, 22 and 33 mm) [33]. On the other hand the amount of light produced is proportional to the thickness of the scintillator H s crossed.…”