electron cloud build up in the fcc heb update on simulation results

Electron cloud build up in the FCC HEBUpdate on simulation results

L. Mether, G. Iadarola, G. Rumolo

Electron cloud meeting 2

FCC High Energy Booster (HEB)

27.6.2014

• Envisaged additional injector, accelerating beam from SPS to FCC

• To be housed in current LHC or future FCC tunnel

• We study electron cloud build up in the FCC-tunnel HEB using PyECLOUD

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Electron cloud simulations

27.6.2014

• We investigate the effect of beam pipe aperture and bunch spacing on the formation of e-cloud in HEB

• Focus on arc dipoles, with beam at injection energy, 450 GeV

• Consider circular beam pipe, scanning over aperture radiiof 1.0 - 3.75 cm

• Corresponding parameters:• Transverse emittances εx ,εy : 2.5 µm

• Beta functions βx ,βy : 67, 71 m

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Electron cloud simulations

27.6.2014

• Since most machine details unknown, consider simple scenario: • Uniform initial distribution of seed electrons, no other primary

electron production• Single uniform bunch train

• Study 3 different bunch spacings• Bunch intensities scaled to keep average current constant

50 2 * 1011 325

25 1 * 1011 650

5 2 * 1010 1000

Bunch spacing [ns] Intensity [ppb] Train length [b]

5ns train shorter, results scaled accordingly

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Simulation results

27.6.2014

Heat load as function of radius, 50 ns beam

Heat load increases monotonically with R

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Simulation results

27.6.2014

Heat load as function of radius, 25 ns beam

Heat load decreases for large R

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Simulation results

27.6.2014

Heat load as function of radius, 5 ns beam

Heat load decreases with growing R, but oscillates

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Simulation results

27.6.2014

Heat load as function of SEY, 50 ns beam

Heat load increases monotonically with R

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Simulation results

27.6.2014

Heat load as function of SEY, 25 ns beam

Heat load decreases for large R

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Simulation results

27.6.2014

Heat load as function of SEY, 5 ns beam

Heat load decreases with growing R, but rises non-linearly

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Simulation results - electron energy spectrum

27.6.2014

• Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve

• For larger radius, peak closer to maximum SEY, δmax

50 ns

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Simulation results - electron energy spectrum

27.6.2014

• Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve

50 ns

• For larger radius, peak closer to maximum SEY, δmax

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Simulation results - electron energy spectrum

27.6.2014

• Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve

50 ns

• For larger radius, peak closer to maximum SEY, δmax

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Simulation results - electron energy spectrum

27.6.2014

• Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve

50 ns

• For larger radius, peak closer to maximum SEY, δmax

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Simulation results - electron energy spectrum

27.6.2014

• Peak energy of electrons impacting on the chamber wall, lies in the emitter region of SEY curve

50 ns

• For larger radius, peak closer to maximum SEY, δmax

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Simulation results - electron energy spectrum

27.6.2014

25 ns

• Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve

• For larger radii, the peak moves towards lower energies, outside of the emitter region

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Simulation results - electron energy spectrum

27.6.2014

25 ns

• Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve

• For larger radii, the peak moves towards lower energies, outside of the emitter region

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Simulation results - electron energy spectrum

27.6.2014

25 ns

• Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve

• For larger radii, the peak moves towards lower energies, outside of the emitter region

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Simulation results - electron energy spectrum

27.6.2014

25 ns

• Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve

• For larger radii, the peak moves towards lower energies, outside of the emitter region

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Simulation results - electron energy spectrum

27.6.2014

25 ns

• Peak energy of electrons impacting on the chamber wall, still lies mainly in the emitter region of SEY curve

• For larger radii, the peak moves towards lower energies, outside of the emitter region

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

Electron cloud meeting 3030

Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

Electron cloud meeting 3131

Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

• For 5 ns beam, no clear energy peak

• Electrons interact with several bunches before reaching chamber wall

• Behavior very radius dependent in non-monotonic fashion

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Simulation results - electron energy spectrum

27.6.2014

5 ns

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Summary & conclusions

27.6.2014

• Electron cloud formation in the FCC HEB has been studied, varying chamber radius and bunch spacing• 50 ns beam

• Larger radii produce more e-cloud, peak electron energy resides around δmax

• 25 ns beam • e-cloud production grows with R until SEY-dependent

threshold, where peak e-energy moves into absorber part of δ(E) curve

• Cloud production then decreases as R grows further• 5 ns beam

• Electrons interact with multiple successive bunches before hitting chamber wall more complex behavior

• General trend is more e-cloud for smaller radii• For SEY ~ 1.2-1.5 very non-linear behavior