PS Impedance Meeting

Minutes April 3rd, 2009

Present:  Mike Barnes, Fritz Caspers, Simone Gilardoni, Elias Métral, Nicolas Mounet, Benoit Salvant. 

   Agenda

 

- Discussion on the observations by Heiko of new longitudinal instabilities in the PS in 2008

          
        

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    Minutes

• Please refer to Heiko's talk at the APC...err....MSWG (slides)
   
• These new couple bunch instabilities could be linked to the MKE kickers installed during the shutdown 2007-2008
   
• Wire measurements and theory expect a longitudinal increase due to these kickers of about 2 Ohm, i.e. 10% of the total broadband impedance of the PS (20 Ohm). Therefore, this increase was predicted to have little consequences on the thresholds for longitudinal instabilities (see EPAC06 paper).
   
• However the small resonances measured at low frequency on the kickers may be a cause of the observed coupled bunch instability. Action: Elias will find the measured kicker data, and with the help of Elena Shaposhnikova (who did a similar study for the SPS) and the rest of the team, he will model the measured resonances by resonators and assess by simulation or theory whether these resonances can lead to the coupled bunch instabilities.
   

• Precisions from Mike after the meeting:

  "
  Following this mornings discussions, I talked with Luc Sermeus. Luc tells me:

  1) The kicker magnets, for MTE, were installed during Dec 2007 and January 2008;

  2) The kicker magnets on which impedance measurements were made were "before modification" for MTE;

  3) The kicker magnets on which impedance measurements were made had a "bricolage" representing the transition pieces.

  4) Impedance measurements were made with cables connected on the input and a short circuit on the output (i.e. as per used during operation for MTE).

  "
   

• Zoom and fit of the measured resonances at low frequencies (Elias's slides)

   

.

AOB

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