muon background

(Y.Namito) It consists of 6 cylinders (iron or lead) with $0.6 \phi \times 120$m in each. For NLC, it consists of 4 spoilers as a tunnel filler of $3 \times 3 \times 9$m³.

Muon transformation is significantly sensitive to a detailed geometry of tunnel. Radioactivity must be studied inside/outside the tunnel. Optimization of the collimation method is necessary by using the two methods.