On-axis injection simulations

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On-axis injection simulations A.Petrenko, K. Lotov, 10/04/2014 AWAKE collaboration meeting at CERN

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On-axis injection simulations. Petrenko , K. Lotov, 10 / 04 /2014 AWAKE collaboration meeting at CERN. On-axis injection of electron beam (15 MeV, 2 mm* mrad ) into the proton-driven SMI wake-fields. Injected electron beam:15 MeV, σ r = 0.3 mm, ε n = 2 mm·mrad - PowerPoint PPT Presentation

Transcript of On-axis injection simulations

Page 1: On-axis injection simulations

On-axis injection simulations

A. Petrenko, K. Lotov, 10/04/2014

AWAKE collaboration meeting at CERN

Page 2: On-axis injection simulations

On-axis injection of electron beam (15 MeV, 2 mm*mrad) into the proton-driven SMI wake-fields

Injected electron beam:15 MeV, σr = 0.3 mm, εn = 2 mm·mrad

27% of injected beam is capturedThese electronswill be captured

Distance from laser pulse

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On-axis injection of electron beam (15 MeV, 2 mm*mrad) into the proton-driven SMI wake-fields

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On-axis injection of electron beam (15 MeV, 2 mm*mrad) into the proton-driven SMI wake-fields

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On-axis injection of initially parallel 15 MeV electron beam into the SMI wake-fields (first 1 meter)

This artificial rectangular electron beaminitially has zero angular spread

In order to minimize nose this first meter of injectionis simulated here using the fliud mode of LCODE

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On-axis injection of initially parallel 15 MeV electron beam into the SMI wake-fields (first 1 meter)

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Individual injection trajectories for some electrons along 1 m of plasma:

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On-axis injection of narrow initially parallel electron beam into the SMI wake-fields (first 1 meter)

Does it make sense to inject very narrowelectron beam in order to get low emittance?

Will the electrons always stay near the axisduring the capture process?

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On-axis injection of narrow initially parallel electron beam into the SMI wake-fields (first 1 meter)

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Typical electron beam distributions after 10 m plasma:

Injected electron beam: (15 MeV)σr = 0.3 mm, εn = 2 mm·mrad,bunch length = 2.7 mm (uniform).

27% of injected beam is acceleratedIf initial Ne = 109 then final Ne = 3·108.

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Typical electron beam distributions after 10 m plasma:

Estimate of final e-beamemittance:

εn ~ (0.1 mm)*(2 mrad)*γ == 0.1*2*1300 MeV/0.5 MeV == 500 mm·mrad >> initial εn

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Baseline proton beam after 10 m plasma:

Proton distribution in the interacting part of the beam (s<0):

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Electron & proton beam envelopes after plasma:

Laser beam size?

Plasma exit

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Conclusions• On-axis injection of 15-20 MeV e-beam should be the primary option.

In the case of baseline 2 mm*mrad e-beam capture efficiency is 30 %, energy gain is 1-2 GeV (If initial Ne = 109 then final Ne = 3·108).

• Injected electron beam should be focused to σr = 0.2--0.5 mm.• Wakefield focusing/defocusing quickly (over first 20-50 cm) gives

large transverse angles (5-10 mrad) to captured electrons. Therefore on-axis injection is not sensitive to e-beam emittance. Electron beams with 20-30 mm*mrad emittance could also be injected with 10-15% capture efficiency.

• Typical angular spread in the accelerated beam is ±2 mrad (if spectrometer screen is 3 m downstream plasma section => transverse beam size = ±6 mm)