Charged-particle tracking with high spatial and temporal resolution using capillary arrays filled with liquid scintillator

We developed a new technique that allows the trajectories of ionizing particles to be imaged with very high spatial and temporal resolution. This technique, developed for future experiments in high-energy physics, may also be applied in other field. Central to the technique is a detector consisting of a bundle of thin, glass capillaries filled with a liquid scintillator of high refractive index. These liquid-core scintillating fibers act simultaneously as a detector of charged particles and as an image guide. Track images seen at the readout end of the capillary bundle are amplified by an optoelectronic chain consisting of a set of image-intensifier tubes and read by a photosensitive CCD camera. We report here on results obtained with detector prototypes. A spatial resolution of 6-14 micrometers , dependent on image magnification prior to readout, has been obtained with 16 micrometers capillaries. The high scintillation efficiency of the liquid scintillator used and a large light attenuation length-- approximately 3 m for 20 micrometers capillaries--result in hit densities along the track of a minimum-ionizing particle of 8.5 mm$^{-1}$ and 3.5 mm$^{-1}$ at distances from the readout window of approximately 2 cm and approximately 1 m respectively. The radiation resistance of the detector is an order of magnitude greater than that of other types of tracking device of comparable performance. To complement the detector we have been developing a new readout system based around a gateable vacuum image pipeline (VIP) and an electron- bombarded CCD camera. These increase the spatial and temporal resolution obtained with detector and render it particlarly attractive as a microvertex detector for the observation of short-lived particles in high-energy physics experiments performed with evelated interaction rates.