1. Considerations on laser-p+ beam merging for AWAKE@CERN CB, BG, PM

2. Some info/issues/questions Minimum distance of mirror to IP is about 20 m, maximum distance is about 50 m Laser beam size as a function of S from plasma cell (done) – can change by altering the laser  * at the plasma cell centre Additional tolerances for position adjustment, stability etc. should be small (maybe ~1 mm) Entrance window between p+ and laser vacuum can be separated from the p+ beamline and away from the turning mirror Co-linearity is assumed between laser and p+ beam (could be angled to help with merging but would then need more powerful laser – keep as ‘2 nd choice’ option) Volume of the turning mirror and positioning system will need maybe 50 cm longitudinal free space in the lattice (Also of note: we should update the beam loss estimates to include instruments, commissioning, setting up and accident cases)

3. First ideas: resuse p+ beamline switch between TT40 and TT41 Rotate everything 90 degrees to make vertical bend In TT40, 8x MBSG magnets needed (3.0 m, ½ MBB length) Total ‘merging bend’ length is 40 m (inside the quads). Too long

4. Combine merging and bends and triplet... Separate vertical bends for RP considerations QD Basic ideas MBA/B? MBB? QF Laser QF MBA? QD Triplet

5. Sagitta in MBB chambers With 2.1 T we have already a 25 mm offset at the exit of one MBB, 100 mm after two MBB, so at maximum only two MBA/B magnets possible (by offsetting the axis)

6. First attempt at merging region layout* Use 3.0 m quadrupoles, 6.3 m MBA/B, 0.5 m inter-magnet drifts, and 1.0 m drift for turning mirror All quadrupoles centred on p+ beam axis 0.6 degree total bend (need 3 more MBA/Bs for 2 degrees) 22 m from mirror to exist of last triplet quad... Turning mirror *upside down and back to front

7. P+ beam Laser beam ~40 mm ~30 mm In Central triplet QD

8. In MBA ~30 mm ~100 mm

9. At turning mirror ~30 mm ~110 mm

10. Next steps Optics with such a triplet! – Required spot size – Drift distance to plasma cell entrance – Beam envelopes, apertures – Element strengths Add real laser envelope function and determine beam sizes along the line Will certainly need some iteration(s)

11. Other possibilities MBS type magnets – no H apertue limit for laser beam Problem is that only one spare exists – but anyway will need to design and build new ones for the switch from TT60!

12. MBS(G) magnets used to switch between beamlines – open C-core

13. MBS magnet cross-section 56 mm

14. MQA quadrupoles? If needed, more aperture vertically Also coil window between 190 and 300 mm, so passage at about 220 mm comfortable – easier than QTL in terms of merging angle. Horizontal gap between coils about 50 mm (45 inside chamber)