Mechanical stabilisation of CLIC quadrupoles to the sub nanometre
by Kurt Artoos (CERN)
A CLIC Main Beam Quad prototype on two stabilisation actuators.
Image credit: CERN
In order to reach the luminosity of 2.1034 cm-2m-1 in CLIC, the cross section of the colliding particle beams at the interaction point will be in the order of the nanometre. Quadrupole magnets are used as focusing elements to keep the beam size small along the full accelerator length and to focus the beams to the collision point
Mechanical vibrations transmitted to the quadrupoles will however create small dynamic displacements of the magnets, resulting in a gradual increase of the beam size along the accelerator and jitter of the beam at the interaction point.
Vibration stabilisation systems were developed and successfully tested both at CERN and at LAPP Annecy under EuCARD WP9 framework. The level of vibrations of the quadrupoles is decreased by the systems to values smaller than a nanometre. The calculated gain in luminosity obtained by this vibration reduction is significant. The magnets are placed on vibration isolating supports based on piezo-electrical actuators that will reduce the vibrations measured by seismometers placed on the ground and on the magnet. The same actuating support makes it also possible to make very precise adjustments to the magnet. A precision of a quarter of a nanometre was already demonstrated on a prototype.
During 2013, new full scale prototypes will be constructed in order to move from a laboratory set-up to an accelerator component, integrated with other technical systems. Improved vibrations sensors are being developed.
