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PS Figure of 8 - What do we need Pole Face Windings for ? : - Sextupolar components of PFWf & PFWd are used to correct PS chromaticity - But their quadrupolar component act on machine tune- Tune is then corrected/adjusted by the Figure of 8- Where do the problems come from ? : - Proper chromaticity and tune settings for high intensity beam require high current in the Figure of 8 (up to 1600 A) - Thereforerms current in the Figure of 8 reaches max admissible values with . increasing number of high energy / high intensity cycles. longer flat-tops for RF gymnastics
Supercycles PS pour le remplissage de LHC (Supercycles de 21.6 s) Supercycle SPS/LHC ZERO EASTC AD EASTB EASTB Peut varier suivant l’opération [3] 21.6 s (18 basic periods) SPS/LHC EASTC AD EASTB [4] Le LHC est rempli en 4.3 mn, avec la succession de 12 supercycles suivante : [3] [3] [4] [3] [3] [4] [3] [3] [4] [3] [3] [3]
Courant rms dans la Boucle en huit pendant les remplissages de LHC I rmspendant le Supercycle SPS/LHC Zero EASTC AD EASTB EASTB Supercycle [3] 505 [A] Hypothèses :User I rmsEAST 340 AAD 690 ALHC 572 A SPS/LHC EASTC AD EASTB [4] 545 [A] 21.6 s 12 Supercycles pour remplir le LHC (4.3 mn)Succession des Supercycles : [3] [3] [4] [3] [3] [4] [3] [3] [4] [3] [3] [3] 515 [A]
Figure of 8 rms Current- Requirements for present SPS MDs & future LHC filling - Present SPS MDs LHC fillingscheme or During SPS MDs or LHC fillings, with 4 LHC cycles, AD and East cycles are exclusive (*) from G. Métral PS/OP
Figure of 8 rms current for LHC filling- rms current on AD cycle reduced down to 575 A(*) - (*) may even be reduced down to 550 A (G. Métral PS/OP)
Figure of 8 rms current for LHC filling- rms current on AD cycle reduced further down to 550 A -- LHC double batch cycles squeezed down to 2.4 s, with reduced rms current - The supercycle length cannot be reduced by more than 2 basic periods (*) from G. Métral PS/OP
PS Figure of 8 Requirements and Limitations - Summary : Actions to be taken- 1. Reduce rms current on AD cycle : - copy of LHC cycles setting being done - flat-top shortening by suppression of stacking mode RF gymnastics Goal : going from 690 down to 550 A 2. Provide rms current checks : - rms current evaluation tool, for any supercycle being done - warning signal before tripping on rms current measurement 4. If LHC can be reduced down to 2.4 s : - reduce rms current to minimum (640 A ?) - do not expect full gain on supercycle length (max 2.4 s)5. Devote MD time to interlock adjustments and checks with expected future supercycles