Vladimir Litvinenko, APEX Workshop 11/02/20006 IBS suppression lattice Mei Bai, Joanne Beebe-Wang, Peter Cameron, Roger Connolly, Angelika Drees, Alexei

Vladimir Litvinenko, APEX Workshop 11/02/20006

IBS suppression lattice

Mei Bai, Joanne Beebe-Wang, Peter Cameron, Roger Connolly,Angelika Drees, Alexei Fedotov, Wolfram Fischer, George Ganetis,

Vladimir Litvinenko, Nikolay Malitsky, Aljosa Marusic, Christoph Montag, George Parzen, Fulvia Pilat, Vadim Ptitsyn, Thomas

Roser,Todd Satogata, Steve Tepikian, Dejan Trbojevic, Nick Tsoupas, Jie Wei


Content• What is IBS suppression lattice?• What are potential gains from IBS

suppression lattice?• What did we tested?• What should we test?• Conclusions


Motivation•Increase the Au-x Luminosity Life-time

•Reduces Back-ground•Simplify requirements on Electron Cooling


Transverse IBS in RHICThe main contribution to the transverse IBS in RHIC come from the arcs, most of which comprised of FODO cells

€

dεxds

= H s( ) ⋅ dδE2

ds; H s( ) = γ xDx

2 + 2α xDxDx′ + β xDx′2

€

dδE2

ds∝ Nσ sσ r

2σ r'; Hmod s( ) =

H s( )β y (1+α x

2) + β x (1+α y2)


Relative transverse IBS rate in RHICPresent operatingpoint

Qx

Qy

NOTE: Qx.y are tune advances per one FODO cell


Reduction of the IBS rate, i.e. increase of the luminosity lifetime

Qx/cell

IBS(0.22)/ IBS(Qx)

Present operatingpoint

NOTE: Qx are tune advances per FODO cell

Qy = (0.9 or 1 or 1.1) Qy

90o 108o72o 126o 144o


Transverse IBS in RHIC for test lattice


Test lattice for IBS suppression

S.Tepikian


S. Tepikian


Transverse IBS in RHIC for test lattice

A.Fedotov


S. Tepikian


Cu101 Ramp Editor Settings

T. Satogata


Cu101 Beam Experiment, RampingVladimir, Steve, Al, Vadim, Nikolay, Mei, NickL, Roger, Dejan,

Rob, …

T. Satogata


Cu101 Beam Study Ramp Items Circulated beam easily in both rings , injection retuned

Injection emittance is beautiful (6-7 mm mrad), optics okay Four ramps, using only blue ring (yellow q89 PS not swapped)

Two ramps with Cu101, slow factors 2 and 3, still excursions and quench protection trips on q6 power supplies Two ramps with Cu102, to lower energy (=91.4), slow factor 1

Ramp tuning is mainly orbits/tunes, though coupling is an issue Tunes/chroms in Cu101 now match well with model at injection

Chroms within 2-3 units, tunes within 0.03-0.04 Orbit/coupling corrected at injection, propagation up ramp not

good Dispersions re-measured in both rings at injection, looks okay Transition never really explored, timing was always wrong and

should be dead-reckoned for next study

T. Satogata


S. TepikianWent to 31 GeV test


S. Tepikian


S. Tepikian



???


S. Tepikian

31 GeV test


S. Tepikian

er


Hardware Limitations• Power supplies, leads and quenching • Current distribution limitations - H & V strings, the

tree of shunting PS…• Sextupole strength • Growth of t and strength of t quads • Matching with desirable * - Not needed for the

test• Dynamic aperture• Effects on coupling compensations scheme,

diagnostics using specific tune advances, etc….


Latest simulations IBS calculation based on exact Martini’s

model for dedicated experiment on IBS suppression (RHIC run-7):

Au ions, 100 GeV/nex=15 p mm mrad (95% normalized)ey=10 p mm mrad (95% normalized)

RF: 300kV, h=360 to avoid loss from the bucket

Several bunch intensitiesA.Fedotov


Simulations: Bunch with intensity N=1e9, red – standard run-7 lattice; blue – 92 deg. phase advance lattice with the same RF voltage; green – 92 deg. lattice with voltage adjusted to have initial bunch length as for run-7 lattice.

A.Fedotov


Suggestion for the experiment1. Due to possible fluctuation in IPM

measurements, for convincing comparison of various lattices recording of emittance growth over the period of 2 hours or more is desired.

2. Experiment conditions for IBS suppressed lattice should be the same as for typical dedicated IBS experiment: 6 bunches, two for each of 3 different intensities.

3. Higher intensities per bunch are preferred.

A.Fedotov


Conclusions• Already developed lattice (92o) promises to

reduce transverse IBS by 1/3rd • Good injection and reasonable ramp to 31 GeV

(cross the t) had been tested• IBS tests at 31 GeV were indecisive and

confusing• Examine possibility of further increase in the

phase advance with present hardware• Two hours measurements: both the base-line and

IBS suppression lattice are desirable• Requires tests of power supplies before the Run 7• Using both the yellow and the blue is very desirable


Go over the IBS

Documents

Vladimir Litvinenko, APEX Workshop 11/02/20006 IBS suppression lattice Mei Bai, Joanne Beebe-Wang, Peter Cameron, Roger Connolly, Angelika Drees, Alexei