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Neutrons are also produced at a rate of 106n/train by the pairs which interact with the pole tips of the final quads, where 0.13 neutron is produced per 1 GeV energy deposit. For NLC, the VTX has $3 \times 10^{-3}$ n/cm2/train corresponding to 107 n/cm2/year. Since a tolerable neutron yield is $3 \times 10^9$ n/cm2, they cause no serious problem.

However, neutron yields from the beam dump must be problem because of the huge energy deposit there. Without an efficient neutron absorber, the detector is seriously damaged. The detailed design is needed for the extraction line through the beam dump, so-called dump line.

Toshiaki Tauchi