We present the concept and design of a liquid scintillator detector for a l
ong-baseline neutrino oscillation experiment. Neutrinos interact in 2.5 cm
thick steel plates alternating with 2.0 cm thick planes of liquid scintilla
tor. The scintillator is contained in multicell PVC extrusions containing i
ndividual 2 cm x 3 cm cells up to 8 m long. Readout of the scintillation li
ght is via wavelength-shifting fibers which transport light to pixellated p
hotodetectors at one end of the cells. (C) 2001 Elsevier Science B.V. All r
ights reserved.