How to mount and dismount the VAX Module 1 during maintenance
This animation shows how to mount and dismount the VAX Module 1 during maintenance.
The robot is to double actuate the internal mechanism in order to reach and seize the bellows. In the next step, a chain clamp has to be open to untighten the connection. Then, the chain clamp is pivoted back. Now, when the bellows are untightened, it can be compressed. Pivoting and compressing aim to gain some space before the final step which concerns the shifting of vacuum components inside Module 1. This final move liberates the connection between Module 1 and the adjacent chamber.
The maintenance procedure of Module 3 is the same as for Module 1, which is ready for removal and transport. (Video: CERN)
How to mount and dismount the VAX Module 2 during maintenance
This animation shows how to mount and dismount the VAX Module 2 during maintenance.
The robot is to double actuate the internal mechanism in order to reach and seize the bellow. In the next step, a chain clamp has to be open to untighten the connection. Then, the chain clamp is pivoted back. Now, when the bellows are untightened, it can be compressed. In the last step, the Module has to be disconnected from the services. The procedure is the same as for Module 1, only the size of connections differs. Firstly, a chain clamp is open to untighten the connection. Later, a dedicated mechanism inside Module 2 compresses the vacuum components to liberate the connection.
Module 2 is ready for removal and transport. (Video: CERN)
Suppression of a beam instability by bringing the beams into collision more quickly
If the two counter-rotating beams are separated by a transverse offset between one and two rms beam sizes for too long a time, an impedance-induced beam instability can develop due to a loss of transverse Landau damping. (Image: CERN)
Mode-coupling instability of colliding beams suppressed by the hourglass effect
The strong focalization of the beam at the interaction points leads to a deformation of the beam profile due to the hourglass effect, which suppresses the mode-coupling instability between beam-beam and impedance through Landau damping => Please note that the hourglass effect (seen on the right picture) has been amplified to see it more clearly BUT the stabilising effect was observed with the correct HL-LHC parameters. (Image: CERN)