2.The connecting of neighbour tetrahedran with common vertexangle forms M—O layer(M=Al,Si),and the connection of neighbour octahedran with common edge or plane forms Al—O layer.
6.The structure and pertormance of vertex chamber of BESⅡ are described. It covers 95%×4π of solid angle with the spatial resolution of σ r? ≈100μm and σ z ≈2mm respectively.