Update of layout of electron beam line and

Update of layout of electron beam line and vapour source L. Verra, R. Ramjiawan AWAKE Run 2 Meeting, CERN Thursday 26 th March 2020

Overview • We (P. Muggli, L. Verra, F. Velotti, R. Ramjiawan) had a meeting to discuss how best to approach studying the layout of the electron line particularly with regards to the vacuum window placement. • It would be good to have a cohesive approach for this, plans for these studies are outlined in this presentation.

1) membrane positioned further upstream. Great simplification of the design of the gap area Si. N membrane vacuum e- be a m Rb vapor B p+ beam laser beam SM’or x laser beam LBDP ~m ACC’or

1) membrane positioned further upstream. If the foil is positioned where an imaging waist is, the emittance growth is negligible. e. g. for a 1: 1 imaging, β = 5. 1 mm (matched beam for npe = 7 E 14 cm-3) εN_in [mm mrad] σw [μm] ΔεN Δβ 2 5. 6 <1/1000 5 8. 9 “ “ 10 13 “ “ 15 15 “ “ 20 18 “ “ Easier or more difficult to transport with a 1: 1 imaging? (The increase on emittance and decrease on beta is below 1% up to 10: 1 imaging)

Current beamline design • The current beamline design does not have one singular imaging waist for both x and y together and so I will look into this next. • I will study designs with e. g. 2: 1, 3: 1, 4: 1 etc. imaging.

1: 1 imaging •

Modelling the window within beamline design • Have added a simple (MCS) model of the foil/vacuum window into the beamline model, so we can study the beamline + window using (PTC) tracking. Possible vacuum window placement • We can then look at different positions/widths of the vacuum window with full tracking of non-linear effects, and can optimise the beamline with the foil already included. Rebecca Ramjiawan

2) vacuum window right before injection Vacuum window + movable laser beam dump to protect the window injection point e. B p+ • very difficult to engineer • more invasive on beam optics x hv

Upper limit: waist is downstream the foil Lower limit: βout < βin βout = 9. 5 mm for npe = 2 E 14 cm-3 ε 0 = 20 mm mrad εin = 2 mm mrad βout = 5. 1 mm for npe = 7 E 14 cm-3 εout= 11 mm mrad εin = 2 mm mrad

Also the waist position is affected: it moves upstream βout = 9. 5 mm for npe = 2 E 14 cm-3 βin = 5. 1 mm for npe = 7 E 14 cm-3 εout = 20 mm mrad εin = 2 mm mrad εout = 11 mm mrad εin = 2 mm mrad

Conclusions: We have two possible solutions to solve one part of the injection puzzle: 1. The membrane is positioned upstream where an imaging waist is (need to adjust the beamline design accordingly) 2. We use two foils right before the injection: once we fix thickness and material, we can univocally determine the necessary incoming parameters