Design of a Rotatable Copper Collimator for the LHC Phase II Collimation Upgrade

The Phase II upgrade to the LHC collimation system calls for complementing the robust Phase I graphite collimators with high Z, low impedance Phase II collimators. The design for the collimation upgrade has not been finalized. One option is to use metallic rotatable collimators and this design will be discussed here. The Phase II collimators must be robust in various operating conditions and accident scenarios. Design issues include: 1) Collimator jaw deflection and sagitta due to heating must be small when operated in the steady state condition, 2) Collimator jaws must withstand transitory periods of high beam impaction with no permanent damage, 3) Jaws must recover from accident scenario where up to 8 full intensity beam pulses impact on the jaw surface and 4) The beam impedance contribution due to the collimators must be small to minimize coherent beam instabilities.