LIU-SPS Open C-core MKE Extraction ReviewDiscussion and concluding remarks

Jan Uythoven & Carlo Zannini20 March 2013

Jan Uythoven, LIU-SPS Open C-core MKE Extraction Kicker Review

20 March 2013

IntroductionBrennan Goddard

• Medium Term Plan 2013 should contain ‘final’ LIU project definition

• Decision to be made by October

• Decide on baseline upgrades, including MKE which has shown limitations in the past

• Is the present system adequate for future beams?

• If not, is the open C-kicker to be further explored?

Performance of existing MKEGlen Vanbavinckhove

• HL-LHC factor 2.2 larger bunch intensities for 25 ns and 50 ns spacing• Large reduction in Re Z due to serigraphy. Resonance – peak at 45 MHz – can be reduced by

staggering the lines ?? Total power will stay the same• Gain about a factor 2 in kicker temperature by serigraphy.

• For HL beams we would reach about 75 degr measured (70 degr is IL), during scrubbing run 25 ns.

• For 50 ns beams gain about factor 3. With HL beams also about 75 degr. • Scaling squared w. bunch intensity confirmed. Bunch length important variation -> Q20 (longer

bunches) or Q26 optics. Conservative so far.• With HL beams serigraphed, same power deposited as now with no serigraphed.

• Issue now during srcubbing. Not normal operation. Gain bunch length Q20.

• 25 ns better than 50 ns• Other kickers also possible limits:

• MKP-L: double temperature rise than MKE serigraphed. Expect 150 degrees ferrite HL beams

• MKD-V: similar to MKE serigraphed. No serigraphy[hy foreseen. Expect 128 degr. ferrites.

• MKQH: worse than MKE non-serigraphed, similar to serigraphed. Worry is damage not tune measurement? Foreseen to put serigraphy.

• Other improvements MKE

• Chilled water and dark coated tank could significantly help

Kicker Impedance ModelCarlo Zannini

• Conceptual design implemented beam in and beam out

• Portion of ferrite not screened by the ‘box’ (S2) varied

• Will have gap between ‘box’ and ferrite (Mike)• When the beam is out, the impedance can be neglected. • No serigraphy assumed in simulations• When the beam is out, peaks shifted to higher frequencies• Higher impedance when beam is in – of course

• Transverse impedance significantly increases relative to present

• Longitudinal a shift but not an increase, shift to higher frequency• Power loss estimate, including beam in opening for 1 second

• With LIU parameters factor 10 lower than present MKE with present beams: Heating of the kicker not an issue!

• Confirm statement from Glen LIU – present operation

Effect of kicker impedance on beam – longitudinalElena Chapochnikova

• Present kickers

• Synchrotron frequency shift with: present serigraphed MKEs OK following beam measurements, similar to 2001.

• MKE compared to all kicker, Im part about 1/5 of all kickers: OK

• Minimum threshold of coupled bunch instability at flat top – loss of Landau damping. 48 MHz peak in impedance not very nice, improvement to be studied

• Open C-kicker

• Beam out: very low

• Beam in: 3x higher ImZ/n and 3 times higher Re/z for complete system, at flat top, which is the most critical time, beam in only 100 ms. Long instability growth time > 1ms, damped by large dfs/fs.

• SPS BQM can decide not to extract 50 ms before extraction if not stable, but might not be able to measure.

• With Q20 and double RF, at the limit for high intensity beams.• Prefer present MKEs above the open C non serigraphed• Study option of serigraphing open C

Effect of kicker impedance on beam – TransverseBenoit Salvant

• Results are preliminary – needs more serious studies…• Beam out: small impedance. Thresholds for instabilities will increase at

injection, good news• Beam in: larger vertical impedance, by 30 %, moved to higher

frequencies, peaks at low frequencies

• However, beam is stiffer at higher energy: gain factor 17…

• Injection remains more critical: factor 2 (really last minute) 3 / 6.5 / 8 / 17 worse at injection depending on assumed beam parameters. Further checks required.

• TMCI should not be an issue, not with present nor future system (Elena)

• Positive to go to open C MKE (preliminary), not expect to introduce a new limit

Feasibility of C-core SystemGlen Vanbavinckhove

• Layout of kickers, bumps and trajectories for Q26 and Q20 optics• Bump of 78 mm

• using four correctors presently installed, for both LSS4 / LSS6

• Strength to be increased of 43 % / 30 %. Above present current limit. Magnets to be replaced by MPSH type.

• Larger aperture quads required at QF.41610 and QF.61610• To check if the orbit can be measured with present system for such a

large bump -> BPM system to be replaced• Dispersion matching and TPSG clearance to be studied• Apertures for slow extracted should be OK

Possible New MKE kicker systemMike Barnes

• Presently two types: MKE-S and MKE-L, water cooled, all but one serigraphed. Parameter list.

• Rise-time limited LSS4 only for CNGS beams: stopped

• Future limit on rise time 6 us only• Future MKE. About 4 – 5 m length instead of present 8 m. One generator driving all magnets

about 1.5 us rise time. Stay 10 Ohms, resistively terminated.

• Each magnet faster because of reduction of magnet inductance. Stay below 1 us if individual generators

• Magnet simulations – conducting box should not touch the ferrite. Legs of the box (S2 from Carlo) can be relatively small…

• Field homogeneity OK – could possibly reduce depth of the magnet, which would reduce the bump height. Noses on ferrite preferred.

• Return busbar preferred behind the box. • MKE tank not centred around circulating beam to allow for bumped beam

• Bellows?• Cooling improvements can be applied to present system: SIGNIFICANT

• Chilled water: gain up to 19 degrees

• Emissivity of tank, 15 – 25 % of power radiated out of the tank. Radioactive..

• Different ferrites with higher Tc

Concluding remarks

A big Thank You to:• The Speakers for doing all the hard work• Brennan and Malika to get this all going• Julia for the great organisation