High-resolution tracking using large capillary bundles filled with liquid scintillator

We have developed large high-resolution tracking detectors based on glass capillaries filled with organic liquid scintillator of high refractive index. These liquid-core scintillating optical fibres act simultaneously as detectors of charged particles and as image guides. Track images projected onto the readout end of a capillary bundle are visualized by an optoelectronic chain consisting of a set of image-intensifier tubes followed by a photosensitive CCD or by an EBCCD camera. Two prototype detectors, each composed of \hbox{$\approx 10^6$} capillaries with \hbox{20$-$25 $\mu$m} diameter and \hbox{0.9$-$1.8 m} length, have been tested, and a spatial resolution of the order of \hbox{20$-$40 $\mu$m} has been attained. A high scintillation efficiency and a large light-attenuation length, in excess of 3 m, was achieved through special purification of the liquid scintillator. Along the tracks of minimum-ionizing particles, the hit densities obtained were $\sim$ 8 hits/mm at the readout window, and \hbox{$\sim$ 3 hits/mm} at $\sim$~1~m away. The level of radiation resistance of the prototype detectors is at least an order of magnitude higher than that of other tracking devices of comparable performance.