Multibunch

Working group

  
 
Presentations Chairman's conclusions
 
 
Monday 13th March Conclusions Day 1
Round Table (5 mins per represented lab.): Conclusions Day 2
1.   ALS (J Byrd) 9.    DAFNE (A Drago)  
2.   SPEAR (C Limborg) 10.  PEP II (J Fox)  
3.   BESSY II (S Khan) 11.  Elettra (M Svandrlik)  
4.   SPring-8 (H Ego) 12.  SRS (P McIntosh)  
5.   ANKA (D Einfeld) 13.  DIAMOND (M Dikes)  
6.   Photon Factory (M Isawa) 14.  CERN (F Pedersen)  
7.   DELTA (D Nölle) 15.  PLS (JY Huang)
8.   MAX I, II, III (Å Andersson) 16.  ESRF (J Jacob)
Discussion: "A Gap in the Filling" à suppression of ion instabilities, control of LCBI’s or required for specific experiments.  

 
SPring-8 (H Ego):  Suppression of coupled bunch instabilities in the SPring-8 Storage Ring.

 

  
Resistive Wall Instability and Ion instabilities:
  • ESRF (JL Revol): Measurements at the ESRF, suppressed by means of positive chromaticity, Observation of Side-bands around 5 f0 in uniform filling.
  • Elettra (C Bocchetta): Use of harmonic sextupoles to detune the sidebands around 4f0 , (90% fill).
  • PLS (J Y Huang & YH Chin): Ion experiments, 5 f0 sidebands move by changing ez, strong for uniform filling.
  • SPring-8 (T Nakamura): Landau damping of resistive wall instability by chromaticity modulation at fs .
  
BESSY, (P Kuske):  Observation of longitudinal instabilities at BESSY I: non-linear saturation effects, RF phase modulation at 3fs  
ELETTRA, (M Svandrlik):  HOM control at Elettra: HOM tuners and temperature control, some deliberate HOM excitation for improved lifetime, development of transverse feedback system  
PEP II, (J. Fox): Oscillation by ± 0.2° already saturates the feedback system,  
ALS, (J. Byrd): also feedback saturation for oscillation > 0.1 tL .  
   
Tuesday 14th March  
KEK - PF (M Isawa): Linear model for a special multibunch filling and data processing allowing single bunch experiments.  
 

Higher Harmonic Cavities:

  • NSLS - VUV (N Towne): Beam response for variable Vharm : low & high current measurements, saw tooth instability in over-stretched mode.
  • Discussion: phase transients also with SC cavities = function of R/Q
  • MAX Lab (M Georgsson): Presentation of latest achievements: Full Landau damping of HOM without additional energy spread. Basically, no gap in the filling.
  • ALS (J Byrd): Presentation of ALS harmonic cavities, strong phase transients lead to reduced bunch lengthening at head and tail of bunch trains.
  • Elettra, SLS, CEA (M Svandrlik): Collaboration project for a passive Superconducting harmonic cavity (cryostat 1.1 m long).
  • Super ACO (Å Andersson): Active 5th harmonic system operated at optimum bunch lengthening with full Landau damping of LCBI’s.
  • ESRF (J Jacob): Theoretical prediction of lowered LCBI thresholds for the ESRF (reduced fs overbalances Landau damping).
  • KEK (YH Chin): Suggestion of experiments to check effective threshold variations for LCBI’s with harmonic cavities on various machines. Example of calculations for LEP: TMCI threshold variation by only ± 20% depending on machine impedance model. See hadron accelerators: no dramatic stability improvement if using barrier buckets.
  • CERN (F Pedersen): Single bunch intensity threshold for energy widening should increase with harmonic RF system. Confirmation of phase transient dependence on R/Q.

 

  
Multibunch Feedback Systems
  • ELETTRA/SLS (D Bulfone)
  • Bessy II (S Khan): Results with digital bunch-by-bunch longitudinal feedback system / Slac design.
  • Bessy II (T Knuth): Status of the analog bunch-by-bunch feedback / similar to ALS TFB design.
  • SLAC / PEP II (J Fox): High beam intensity limitations from RF front-end noise re-injected on the beam.

 

  
   
   

Proceedings

Last update : 19/07/00