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Aumon, S.

Paper Title Page
TUPD049 Transverse Mode Coupling Instability Measurements at Transition Crossing in the CERN PS 2036
 
  • S. Aumon
    EPFL, Lausanne
  • S. Aumon, M. Delrieux, P. Freyermuth, S.S. Gilardoni, E. Métral, G. Rumolo, B. Salvant, R.R. Steerenberg
    CERN, Geneva
  
 

Tran­si­tion cross­ing in the CERN PS is crit­i­cal for the sta­bil­i­ty of high in­ten­si­ty beams, even with the use of a sec­ond order gamma jump scheme. The in­tense sin­gle bunch beam used for the neu­tron Time-of-Flight fa­cil­i­ty (n-ToF) needs a con­trolled lon­gi­tu­di­nal emit­tance blowup at flat bot­tom to pre­vent a fast sin­gle-bunch ver­ti­cal in­sta­bil­i­ty from de­vel­op­ing near tran­si­tion. This in­sta­bil­i­ty is be­lieved to be of Trans­verse Mode Cou­pling (TMCI) type. A se­ries of mea­sure­ments taken through­out 2008 and 2009 aim at using this TMCI ob­served on the ToF beam at tran­si­tion, as a tool for es­ti­mat­ing the trans­verse glob­al impedance of the PS. For this pur­pose, we com­pare the mea­sure­ment re­sults with the pre­dic­tions of the HEAD­TAIL code and find the match­ing pa­ram­e­ters. This pro­ce­dure also al­lows a bet­ter un­der­stand­ing of the dif­fer­ent mech­a­nisms in­volved and can sug­gest how to im­prove the gamma jump scheme for a pos­si­ble in­ten­si­ty up­grade of the n-ToF beam.

  
WEPEB042 Optimization of the Position of the Radial Loop Pickups in the CERN PS 2782
 
  • S. Aumon
    EPFL, Lausanne
  • S. Aumon, H. Damerau, S.S. Gilardoni
    CERN, Geneva
  
 

A part of the beam loss­es at tran­si­tion cross­ing of high in­ten­si­ty beams in the CERN PS have been at­tribut­ed to an ex­cur­sion of the closed orbit. The orbit jump oc­curs si­mul­ta­ne­ous­ly with the jump of the tran­si­tion en­er­gy trig­gered by pulsed quadrupoles. In­ves­ti­ga­tions showed that the po­si­tion of the pick­ups used for the ra­di­al loop sys­tem was not op­ti­mized with re­spect to the dis­per­sion change caused by the fast change of the tran­si­tion en­er­gy. Thanks to new elec­tron­ics of the orbit mea­sure­ment sys­tem, turn-by-turn orbit data could be record­ed around tran­si­tion cross­ing. Their anal­y­sis, to­geth­er with cal­cu­la­tions of the trans­verse op­tics, al­lowed de­ter­min­ing a new choice of pick­up po­si­tions for the ra­di­al loop. In com­par­i­son to the pre­vi­ous pick­up con­fig­u­ra­tion, the new con­fig­u­ra­tion im­proves the mean ra­di­al po­si­tion not only dur­ing tran­si­tion cross­ing, but all along the ac­cel­er­a­tion cycle.

  
WEPEB042 Optimization of the Position of the Radial Loop Pickups in the CERN PS 2782
 
  • S. Aumon
    EPFL, Lausanne
  • S. Aumon, H. Damerau, S.S. Gilardoni
    CERN, Geneva
  
 

A part of the beam loss­es at tran­si­tion cross­ing of high in­ten­si­ty beams in the CERN PS have been at­tribut­ed to an ex­cur­sion of the closed orbit. The orbit jump oc­curs si­mul­ta­ne­ous­ly with the jump of the tran­si­tion en­er­gy trig­gered by pulsed quadrupoles. In­ves­ti­ga­tions showed that the po­si­tion of the pick­ups used for the ra­di­al loop sys­tem was not op­ti­mized with re­spect to the dis­per­sion change caused by the fast change of the tran­si­tion en­er­gy. Thanks to new elec­tron­ics of the orbit mea­sure­ment sys­tem, turn-by-turn orbit data could be record­ed around tran­si­tion cross­ing. Their anal­y­sis, to­geth­er with cal­cu­la­tions of the trans­verse op­tics, al­lowed de­ter­min­ing a new choice of pick­up po­si­tions for the ra­di­al loop. In com­par­i­son to the pre­vi­ous pick­up con­fig­u­ra­tion, the new con­fig­u­ra­tion im­proves the mean ra­di­al po­si­tion not only dur­ing tran­si­tion cross­ing, but all along the ac­cel­er­a­tion cycle.