Stabilization of Nanometre-Size Particle Beams in the Final Focus System of the Compact LInear Collider (CLIC)

The Compact LInear Collider (CLIC) study at the European Organization for Nuclear Research (CERN) is developing the design of a 3 TeV e+ e- linear collider. The discovery reach of this machine depends on obtaining a luminosity of 1035 cm_2s_1, which will be done by colliding beams with transverse spot sizes in the nanometre range ≈ 60 × 0:7 nm2). Tolerances on fast mechanical stability of the focusing quadrupoles reach the 0.2 nm level. The serious concern of magnet stabilization for future linear colliders has been addressed by building a CERN test stand on magnet stability, bringing together state-of-the-art stabilization technology, latest equipment for vibration measurements and realistic magnet prototypes. For the first time an accelerator magnet was successfully stabilized to the sub-nanometre level, reducing its vibrations level by one order of magnitude with respect to the supporting ground. The best measurements indicate transverse RMS vibration amplitudes (above 4 Hz) of (0.79+0.08) nm horizontally and (0.43+0.04) nm vertically, maintained to a maximum of less than (1.47+0.15) nm and (1.00+0.10) nm, respectively, over a period of several days. Detailed simulations of time-dependent luminosity, which use a model for magnet displacements based on measured vibration spectra, show that approximately 70% of the CLIC goal luminosity can be achieved with the demonstrated performance in the CERN test stand. This indicates the basic feasibility of colliding a nometre-size beams in CLIC.