  START, a high-efficiency and low-noise scintillation detector for ionizing
particles, was developed for the purpose of creating a high-granular system for
triggering cosmic muons. Scintillation light in START is detected by MRS APDs
(Avalanche Photo-Diodes with Metal-Resistance-Semiconductor structure),
operated in the Geiger mode, which have 1 mm^2 sensitive areas. START is
assembled from a 15 x 15 x 1 cm^3 scintillating plastic plate, two MRS APDs and
two pieces of wavelength-shifting optical fiber stacked in circular coils
inside the plastic. The front-end electronic card is mounted directly on the
detector. Tests with START have confirmed its operational consistency, over 99%
efficiency of MIP registration and good homogeneity. START demonstrates a low
intrinsic noise of about 10^{-2} Hz. If these detectors are to be
mass-produced, the cost of a mosaic array of STARTs is estimated at a moderate
level of 2-3 kUSD/m^2.
