|
|
BIW Working group : Multibunch
last modified
08-01-2008 09:54
BIW Working group : Multibunch
|
Multibunch
Working
group
|
 |
| Chairman : J Byrd
ESRF
correspondents : J Jacob and K Clugnet
|
| 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
|
