1 / 15

Smaller (vertical) beta function Long bunch spacing

Wi =Length_element/ Length_section Wi=0 if ion is unstable. Both growth rate and tune-shift are small if there is a. Smaller (vertical) beta function Long bunch spacing. Peak growth rate of FII for CO+. Pwiggler= 2.0nTorr ; Plong_straight = 0.1nTorr P_arc= 0.5nTorr.

quentin-branch
Télécharger la présentation

Smaller (vertical) beta function Long bunch spacing

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Wi =Length_element/ Length_section Wi=0 if ion is unstable Both growth rate and tune-shift are small if there is a • Smaller (vertical) beta function • Long bunch spacing

  2. Peak growth rate of FII for CO+ Pwiggler=2.0nTorr; Plong_straight=0.1nTorr P_arc=0.5nTorr Growth time is less than 1 turn! Peak growth rate of FII for H+ The growth time is 100 times longer than CO+!! (H+ has small cross section and it is likely unstable after several damping time) 17km ring has a longer growth time Shorter average growth time • TESLA; DAS; MCH; OTW; OCS; BRU;PPA

  3. Tune-shift H+ CO+ The Tune shift caused by CO+ is 30~100 times larger than H+!!

  4. Ion yield Aluminium Copper H+ is dominant component!

  5. Incoherent vertical tune shift-strongly optics dependent Larger tune shift • OTW; DAS; TESLA; MCH; PPA; BRU; OCS • OCS has the longest ARC • OTW has the shortest ARC and small beta at ARC! • DAS, MCH and TESLA has a long bunch spacing!! (ion is Not easy to be trapped)

  6. A smaller beta function help in two aspects! OTW OCS

  7. ATF Nbunch=20, P=10nTorr, 20% is CO+ Radiation damping time 30ms Close to the experiment Tune shift is very small

  8. PLS • Ions are not trapped at some location with the equilibrium emittance, especially in Wiggler • Long straight section PLS(P=5nTorr) • Energy 2.0GeV • Lsep=2ns • x=12.1nm • y=0.12nm • N=1.1681010 • Nbunch=180 • rad=16ms ILC P=5nTorr • Energy 5.0GeV • Lsep=4~20ns • x=0.5nm • y=0.002nm • N=21010 • Nbunch=2820 >100s scaling>21s Calculation (don’t know the optics) 0.9 ms for 100% CO+ 5ms for 100% H+

  9. B-factories KEKB(P=1nTorr) • Energy 8.0GeV • Lsep=2.4m • x=24nm • y=0.4nm • N=5.61010 • Nbunch=1389 • feedback=0.5ms PEPII(P=1nTorr) • Energy 8.0GeV • Lsep=1.26m • x=50nm • y=1nm • N=4.61010 • Nbunch=1732 • cal=0.23ms • Qcal=0.008 scaling_ILC>1s There is no FII observed in usual operation of B-factories except at the beginning of the operation after long shutdown (suppressed by Feedback?) ILC has a faster FII than B-factories

  10. Gaps T Stable Zone with gap (linear model) tgap • Long term motion of ions are likely unstable; (multi-turn trapping is difficult) Trapping time(0.1MHz for 6km ring)

  11. Decay of ion-cloud during the train-gap The decay time of ion-cloud is about 1 times of the ion oscillation period: Wiggler section need a short gap Light ion need a short gap. Gap in KEKB HER: 69.38m(230ns) Gap in PEPII HER: 40m(130ns) (Tco+=110ns; TH+=30ns)

  12. Co+ oscillation period TESLA OCS Damping ring is different from B-factories & Light source The required gap varies with time!

  13. Gap effect on stable zone (OCS) Gap=8 bunch spacing=49.2ns Trapping location varies with time

  14. Summary • The instability/tune shift is dominated by CO+ if it is more than 10% in the vacuum • 17km rings has longer growth time (factor 5~10 better than 6km and 3km rings) • Scaling with the present machines is NOT easy! The shorter growth time is around 100 s (scale with PLS) • Feedback is certainly necessary • Necessary gap is around 1.2 times of ion oscillation period (PEPII). It varies with the time (emittance) and Optics. We need to define the necessary gap for a certain time.

  15. Conclusion • Both DAS and TESLA have longer growth time and small tune shift • Feedback is necessary • Necessary gap is about 1 period of ion oscillation period. 17km ring need a longer train gap Peak growth rate of FII and tune shift with CO+

More Related