On-axis injection simulations
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Transcript of On-axis injection simulations
On-axis injection simulations
A. 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, σr = 0.3 mm, εn = 2 mm·mrad
27% of injected beam is capturedThese electronswill be captured
Distance from laser pulse
On-axis injection of electron beam (15 MeV, 2 mm*mrad) into the proton-driven SMI wake-fields
On-axis injection of electron beam (15 MeV, 2 mm*mrad) into the proton-driven SMI wake-fields
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
On-axis injection of initially parallel 15 MeV electron beam into the SMI wake-fields (first 1 meter)
Individual injection trajectories for some electrons along 1 m of plasma:
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?
On-axis injection of narrow initially parallel electron beam into the SMI wake-fields (first 1 meter)
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.
4
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
Baseline proton beam after 10 m plasma:
Proton distribution in the interacting part of the beam (s<0):
Electron & proton beam envelopes after plasma:
Laser beam size?
Plasma exit
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)