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Issues Concerning Different Beam Lines Integration

Issues Concerning Different Beam Lines Integration. C. Bracco, E. Gschwendtner, B. Goddard, M. Meddahi, A. Petrenko, F. Velotti Acknowledgements: WP3 and WP4 members, P. Muggli and A. Caldwell. Outlines. Introduction Layout and optics Laser integration in p+ beam line Chicane

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Issues Concerning Different Beam Lines Integration

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  1. Issues Concerning Different Beam Lines Integration C. Bracco, E. Gschwendtner, B. Goddard, M. Meddahi, A. Petrenko, F. Velotti Acknowledgements: WP3 and WP4 members, P. Muggli and A. Caldwell

  2. Outlines • Introduction • Layout and optics • Laser integration in p+ beam line • Chicane • Clearance for laser tuning mirror • Sector window and emittance blowup • e- beam integration in p+ beam line • Constraints and assumptions • What can be achieved and what cannot be achieved  proposal • Beam envelopes in the common line • Diagnostics in the common line • Conclusions

  3. Reminder Three beams into the game! Phase 1 (2016): protons + laser beam  prove SMI Phase 2 (2017): protons + laser + electron beam  probe acceleration 7.16 %

  4. Proton Beam Line Optics Minor modification of the beam line (last ~80 m) and re-use of existing components (magnets, diagnostics, power supplies, etc.) • Fulfill experiment optics requirements: • Round beam with a beam size @ plasma cell entrance 1 s = 200 ± 20 mm • Achieved: 1 s = 202 mm • Laser integration in the proton beam line

  5. Proton Beam Envelope and Aperture • Beam Envelope • 400 GeV • 6 sigma beam envelope • 10% beta beating • 3.5 mm mrad normalised emittance • 0.1% Dp/p • 1 mm * (b/bmax)1/2 trajectory error • Aperture: • Pole distance • 2 mm vacuum chamber thickness • 3 mm mechanical tolerance • 75% quadrupole aperture (good field region) • 100% dipole aperture • Laser(pessimistic assumption): • 5 sigma Gaussian envelope

  6. Proton and Laser Beam Plasma cell Laser Proton Not real bottleneck

  7. Proton and Laser Beam Plasma cell Laser Proton Not real bottleneck ± 8 mm ± ~8.5 mm (it must be > 5 mm!) ± 6 mm

  8. Sector Window • Need for a sector window to separate SPS and AWAKE vacuum: • SPS protection in case of any accident (Rb leakage from plasma cell, Be window at the end of the line breaking) • Separate vacuum: possible running with 1e-6 mbar instead of 1e-8 in AWAKE experimental area? • Drowback: emittance blowup induced by the window • Identify the best location (upstream of laser mirror!): • Small betas to reduce emittance blow up (no problem related to energy deposition at the window is expected due to the low beam intensity) Line modification by • Ideal location from point of view of optics and emittanceblowup but: • It falls in the part of the line which is not planned to be modified (re-cabling needed) • It is in between two MBGs, 80 mm long bellow: difficult integration! (bx increases by 50% upstream of the MBG) bx, by [m] bx bx = 49 m by = 43.6 s [m]

  9. Sector Window QTLD: S_centre= 783.07 L_iron = 3.0 m L_tot = 3.3 m K1 =-1.46582e-02 QTSD: S_centre= 780.21 L_iron = 1.5 m L_tot = 1.8 m K1 = -1.46582e-02 • Need for a sector window to separate SPS and AWAKE vacuum: • SPS protection in case of any accident (Rb leakage from plasma cell, Be window at the end of the line breaking) • Separate vacuum: possible running with 1e-6 mbar instead of 1e-8 in AWAKE experimental area? • Drowback: emittance blowup induced by the window • Identify the best location (upstream of laser mirror!): • Small betas to reduce emittance blow up (no problem related to energy deposition at the window is expected due to the low beam intensity) Laser mirror: S_centre= 780.21 QTSD QTLD bx, by [m] • Good location for optics BUT right upstream of the mirror: Secondary Showers!!! bx = 94.3 m by = 94.3 m s [m]

  10. Sector Window QTLD: S_centre= 783.07 L_iron = 3.0 m L_tot = 3.3 m K1 =-1.46582e-02 QTSD: S_centre= 780.21 L_iron = 1.5 m L_tot = 1.8 m K1 = -1.46582e-02 • Need for a sector window to separate SPS and AWAKE vacuum: • SPS protection in case of any accident (Rb leakage from plasma cell, Be window at the end of the line breaking) • Separate vacuum: possible running with 1e-6 mbar instead of 1e-8 in AWAKE experimental area? • Drowback: emittance blowup induced by the window • Identify the best location (upstream of laser mirror!): • Small betas to reduce emittance blow up (no problem related to energy deposition at the window is expected due to the low beam intensity) Laser mirror: S_centre= 780.21 QTSD QTLD bx, by [m] • Chosen location! • bx = 49.0 m • by = 138. 6 m (less critical for mirror…) • QTLD mitigating downstream showers (tbc by FLUKA simulations) bx = 94.3 m by = 94.3 m s [m]

  11. Maximum Allowed Emittance Blow up • Proposed window geometry: 3 mm amorphous graphite (1.55 g/cm3) • At mirror: × 2 emittance blow up still acceptable (> 5mm margin)  at plasma cell entrance: 3 s beam = 850 mm mrad (without dispersion)  no margin for pointing and angular adjustments (not possible to focus further than 4.5 m due to aperture constraints)  target: emittance blowup = 50%, FLUKA studies ongoing! Nominal emittance

  12. Proton and Electron Beam • Common beam line last 4.4 m before plasma cell • Electron beam parameters (F.M. Velotti’s talk): • 15 MeV • 2 mm mrad transverse normalised emittance • 0.5% momentum spread • Same tolerances as for proton beam to evaluate beam envelope C. Magnier, F. Galleazzi

  13. Constraints and Assumptions • Plasma cell: 40 mm Ø, 10 m long • Two common 40 mm Ø ultra-fast valves (38 mm inner Ø) • Proton beam envelope (6s) at plasma entrance: ±2.5 mm • Electron beam envelope (6s) at plasma entrance: ±11.4 mm (3s is ± 6.3 mm). We keep 6s to allow for margin in emittance (equivalent to 3s and×4 bigger emittance 8 mm mrad) • Metallic screen between two beams • Inside plasma cell: 15 mm minimum distance between proton beam axis and plasma cell walls/ metallic screen • “Enough” clearance between two beams

  14. Proton and Electron Beam 10 m 40 mm 40 mm ~1-2 mrad divergence induced by the plasma  filling the full valve opening at the exit of the cell  p+ beam should be centered wrt plasma cell

  15. Proton and Electron Beam 10 m 40 mm 40 mm ~1-2 mrad divergence induced by the plasma  filling the full valve opening at the exit of the cell  p+ beam should be centered wrt plasma cell Space for e-beam needed + shielding  p+ beam has to be off-centered wrt entrance valve (7.6 mm distance from wall and screen) bigger cell

  16. Proton and Electron Beam 10 m 40 mm 40 mm ~52 mm ~1-2 mrad divergence induced by the plasma  filling the full valve opening at the exit of the cell  p+ beam should be centered wrt plasma cell Space for e-beam needed + shielding  p+ beam has to be off-centered wrt entrance valve (7.6 mm distance from wall and screen) bigger cell

  17. Constraints and Assumptions • Plasma cell: 40 mm Ø, 10 m long ✔  52 mm Ø • Two common 40 mm Ø ultra-fast valves (38 mm inner Ø) ✔ • Proton beam envelope (6s) at plasma entrance: ±2.5 mm ✔ • Electron beam envelope (6s) at plasma entrance: ±11.4 mm (3s is ± 6.3 mm). We keep 6s to allow for margin in emittance (equivalent to 3s and×4 bigger emittance 8 mm mrad) ✔ • Metallic screen between two beams ✔ • Inside plasma cell: 15 mm minimum distance between proton beam axis and plasma cell walls/ metallic screen ✔ • “Enough” clearance between two beams ✔

  18. Daring Proposal….. 10 m ~80 mm 40 mm 40 mm 20 mm 40 mm 30 mm • Advantages: • Fulfill all beam requirements • Separate vacuum chambers for p+ and e- beam

  19. Daring Proposal….. 10 m ~80 mm 40 mm 40 mm 20 mm 40 mm 30 mm • Drawbacks: • Bigger plasma cell  more difficult keep T and runiform • An additional ultra-fast valve  costly • Manufacturing?

  20. Daring Proposal….. 10 m ~80 mm 40 mm 40 mm 20 mm 40 mm 30 mm • Challenges: • Very small distance between e- and p+ vacuum chambers  enough room for diagnostics? • Larger aperture of dipoles around plasma cell + stronger fields (tbs)

  21. Beam Envelopes in the Line Plasma cell entrance 40 mm 30 mm 40 mm

  22. Beam Envelopes in the Line Last QD 40 mm 40 mm 30 mm 30 mm 40 mm 40 mm

  23. Beam Envelopes in the Line Last QF 40 mm 40 mm 40 mm 60 mm 30 mm 30 mm 30 mm 40 mm 40 mm 40 mm

  24. Beam Envelopes in the Line Second last MBV 60 mm 40 mm 40 mm 60 mm 40 mm 40 mm 60 mm 30 mm 30 mm 30 mm 30 mm 40 mm 40 mm 40 mm

  25. Beam Envelopes in the Line Final e-beam diagnostics 60 mm 40 mm 40 mm 60 mm 40 mm 40 mm 60 mm 30 mm 30 mm 30 mm 30 mm 40 mm 40 mm 40 mm

  26. e- Beam Diagnostics in Common Line • One pickup BPM at each quadrupole (also current for measurements) • Two additional pickup BPMs at the end of the line to be used during full run  need for a measurements • 1 m drift from plasma cell entrance to avoid Rbcondensating on pickups! • Avoid common vacuum chamber with p+ beam (3e11 p+) mask weak e-beam current (1.25e9 e-) Plasma cell MBH MBV MQ MBV MQ MQ MQ 1m drift BPMs Minimum full aperture @ BPM = 31 mm (6s), 17 mm (3s)

  27. Conclusions 1/2 • Issues and challenges related to integration and coexistence of p+, e- and laser beams have been presented • Laser integration with p+ beam: • Enough clearance (>5mm between beam envelopes) has to be granted for housing the laser tuning mirror. Ok for nominal 3.5 mm mrad emittance with defined chicane. • Effect of emittance blowup induced by sector window under study  define optimum location and design  preserve experiment requirements plus pointing and angular accuracy to insure coaxiality with laser beam (common diagnostics).

  28. Conclusions 2/2 • e- beam integration with p+ beam: • Many constraints have to be fulfilled: plasma cell size, ultra-fast valves size, metallic screen between beams, minimum distance between p+ and walls/screen in plasma cell…. • 6s beam envelope is considered for the e- beam using the nominal RF gun parameters (TDR) • Not possible to fulfill all constraints  proposal: • Twice bigger plasma cell (more difficult to keep T and r uniform) • Two separate valves for e- and p+ beam at the entrance of plasma cell (more expensive) • A minimum offset of 4 cm between the two beam and separate vacuum chambers  separate diagnostics • Somemargin in case of emittance, energy and momentum spread different from nominal parameters.

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