Minutes of the 74th MTE meeting held on Thursday May 2nd 2013

Present :

M. Giovannozzi, M. Hourican, J.-M. Lacroix, S. Mataguez, M. Migliorati, S. Persichelli, B. Salvant.

Excused :

P. Demarest, R. Fernandez Ortega, S. Gilardoni, C. Hernalsteens.

 

1. The impedance contribution of the new dummy septum design has been studied in details. Main points and conclusions:

   • A line at about 112 MHz has been found, which is generated by the gap between the beam screen and the support table. This line was not found in the previous model because of an issue with the mesh generation. The best fix to this is the installation of sliding contacts. It has been decided to install sliding contacts of three sides of the supporting table.

   • The ferrites are no more needed. In any case, the estimated beam power deposited should be rather small (the value of 1.8 W represents only the contribution from the peak of the impedance. In case of need a proper integration should be performed).

   • The rise time of the instability in the most dangerous configuration, i.e., short bunches and close to the blade of the dummy septum is more than 150 ms (to be compared with the 6 ms to raise the slow bump prior to extraction).

   • Bench measurements are foreseen in September. The detailed schedule will be prepared by Mike.

   • Next steps:

     • Check whether additional sliding contacts on each side of the blade in the upper part can further improve the situation (Action: Serena).

     • Check the required pressure of the sliding contacts (Action: Benoit).

2. Progress of dummy septum: 

   • The integration has been verified and corrected. The nominal beam position has been used to locate the dummy septum position in the transverse plane.

   • The integration of the proposed shielding with the dummy septum is fine, as well as with the PS ring and the area close to SS15.

   • A proposal of schedule is presented: it should be verified by other experts.

   • Next steps:

   • The dimensions of the aperture for the passage of the downstream beam pipe should be reviewed and communicated to Raul (Action: Mike).

   • Some inconsistencies in the vertical dimension of the shielding have been found and will be communicated to Raul (Action: Massimo).

   • Feedback concerning the schedule presented by Mike from other experts should be gathered (Action: Massimo).