Turbulence and noise –results 2000/2001

Turbulence and noise –results 2000/2001

VRF

Pk. Det

Pk. Det

BCT

08/2000Hardware noise improvements.1 PS batch, 48 bunches0.8*1012 total : 1.7 *1010 / bunch7.2 s before voltage riseMinimal reduction in peak detected signal.

Pk. Det

VRF

08/2000

4.0*1012 total : 8.3 *1010 / bunch

1.7%/s reduction in peak detectedsignal for slow decay plus instability

10/2001

1 PS batch, 72 bunches4.0*1012 total : 5.6 *1010 / bunch10.8 s before voltage rise 0.7% /s reduction in peak detectedsignal. Instability removed by coupled-bunch feedback which also introduces noise.Turbulence reduced.

Max. intensity restricted in 2001 by pressure rise due to electron cloud effect. Bunches shorter on the flat bottom.

Emittance growth during cycle 11/2001

Cycle 537. t = 22.8 4 batches injected, 1.64 * 1013 total, ~ 90% transmission At 450 GeV/c, 1.48 * 1013 total, 3.7 * 1012 / batch, 5.14* * 1010 / bunch.

Individual RF feed-back and feed-forward on each cavity.Coupled bunch feedback on main cavity pass-band, (two cavities)High voltage cycle, 6.7 MV, with 800 MHz on 650 kV.Noise introduced by coupled bunch feedback and 800 MHz system – to be improved!

After capture, 1200 ms 0.4 eVsEnd flat bottom 26 GeV (Pk detected 10% height) 0.48 eVsTop energy 1) from bunch length: HHFW 0.6 – 0.69 eVs Baseline 0.7-0.9 eVs

2) from peak detected cf analytic 0.67 eVs

Bunch rotation: Drop adiabatically from 6.8 MV to 650 kV. Jump to 6.8 MV (0.5 ms) (J.Tuckmantel)(Using fast counterphasing, T.Bohl) Can gain 40% in bunch length – deduced from peak detected.dp/p increases proportionally.

50 ms /div.

0.5 ms /div.

B train – cycle 537 -2001

start rise join of new parabola to old9800 ms

Peak in Bdot caused by adjustmentof injection energy. (E. Shaposhnikova,T. Bohl, G. Arduini)

Increase from 0.0198 T/s to 0.0296 T/sGives ~ 5% reduction in bucket area for 2 –3 MV

Capture loss should occur ~ 11125 ms or earlierObserved loss may come from peak in Bdot

Suggestion: re-calculate whole B slope or ar leastspread it over a > 4 times longer time-scale

BCT

Bdot

Variation in Bdot caused by errors insaturation tables?

Bdot varies 0.35 T/s 0.02 T/sEffect on bucket area greatest withmatched emittance cycle.0.6 eVs becomes 0.56 eVs at overshoot.Less important to correct but ...

16800 ms / 350 GeV