1. The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. Do we have enough aperture? R. De Maria, M. Fitterer Thanks to G. Arduini, S. Fartoukh, C. Garion, M. Giovannozzi

2. HL-LHC new magnets extends: the β* reach in IR1 and IR5 to increase virtual luminosity, allow high β in in the crab cavities to reduce the required voltage. Outline: Triplet and D1, TAXS apertures TAXN, D2-Q4-Q5 apertures 2 Introduction and outline

3. 1.Optics defines nominal orbit and beam sizes. 2.Geometry of the vacuum region (e.g. beam screens inner dimensions with tolerances are provided). 3.Operational tolerances on the beam size are added to the beam size. 4.Alignment and fiducialization tolerances are subtracted from available aperture. 5.The difference in unit of beam sigma is calculated and compared with the protected aperture offered by the collimations systems 3 Aperture margins ingredients

4. Beam tolerances have been defined by: taking into account LHC Run I (positive) experience adding safety margins based on possible unknowns. For collimation: magnet protected by TCT: ≥12 σ magnet not protect by TCT: ≥20 σ or possibly less if dedicated studies are performed. 4 Beam tolerances and collimation apertures Beam ToleranceLHC Design HL-LHC Inj./Coll. Emittance [µm] (normalization only) 3.753.5/3.5 β-beating [%]2010/20 Orbit error [mm]44/2 Spurious Disp. [%]27.314/10 Energy error [10 -3 ]86/2 Target aperture [σ]8.49/12(20) R. Bruce et al. Fiducialization and ground motion (e.g. 0.6 mm in the triplets) margins taken based on LHC values (J. Jeanneret, LHC rep. 1007).

5. Round optics is the HL-LHC nominal scenario β* x,y =15 cm 5 Optics Scenarios Using β* x,y =15 cm and β* x,y =30 cm/7.5 cm or 30 cm/7.5 cm for reference. Flat optics β* x ≠ β* y a back-up scenario: reduce the crossing angle and allow smaller β* in one plane. IR5B1

6. Round optics is the HL-LHC nominal scenario β* x,y =15 cm 6 Optics Scenarios Using β* x,y =15 cm and β* x,y =30 cm/7.5 cm or 30 cm/7.5 cm for reference. Flat optics β* x ≠ β* y a back-up scenario: reduce the crossing angle (in particular with LRBB) and allow smaller β* in one plane. IR5B1

7. Aperture Overview: Round optics 12 σ beam envelops and orbit shifted on aperture centers.

8. Aperture Overview: Flat optics 12 σ beam envelops and orbit shifted on aperture centers.

9. Octagonal beam screens for triplets/D1 with Tungsten shielding have been designed. Tolerances will be given with prototyping experiences. 9 Triplet area aperture Triplet beam screens, C. Garion shielding cooling Alignment tolerances r [mm] h [mm] v [mm] TAXS2.00.5 Triplets0.61.0 BPMs2.500 D10.61.0 ElementH,V gap [mm] 45° gap [mm] Q1102 Q2-Q3-CP122114 D1122114 Nominal values without tolerances.

10. 10 Q1 Apertures 12 σ beam envelopes for the elements of the same type Tolerances around beam positions Round optics Flat optics

11. 11 Q2 Apertures 12 σ envelopes with beam margins do not fit in the triplet aperture. Beam screen tolerances not included. Round optics (2 mm sep.) Flat optics (0.75 mm sep.)

12. 12 Q3 Apertures 12 σ envelopes with beam margins do not fit in the triplet aperture. Beam screen tolerances not included. Round optics (2 mm sep.) Flat optics (0.75 mm sep.)

13. 13 D1 Apertures 12 σ envelopes with beam margins barely fit in the triplet aperture. Beam screen tolerances not included. Round optics (2 mm sep.) Flat optics (0.75 mm sep.)

14. TAXS round aperture pass from 60 mm to 54 mm. Experiments asked smallest possible TAXS aperture that does not compromise performances for protection reasons. Studies proving that there are failure scenarios that would protect thanks to the smaller apertures are still on-going. Assumed alignment tolerances to be confirmed. 14 TAXS Alignment tolerancesw r [mm] h [mm] v [mm] TAXS2.00.5

15. 15 TAXS Apertures 12 σ envelopes with beam margins barely fit for round optics and does not fit for flat optics. TAXS mechanical tolerances not included. In case experiments requires a shift in the IP, the TAXS aperture should be increased accordingly. Round optics (2 mm sep.) Flat optics (0.75 mm sep.)

16. β functions in D2-Q4-Q5 are constrained by ATS phase advances. The range is defined by the triplet gradients and layout (new layout smaller range). Larger pre-squeeze β* or ATS2 optics (S. Fartoukh) can relax the constraints. 16 D2-Q4-Q5 Optics Within the range the β can be optimized for only one among: Crab cavity voltage (e.g. HLLHCV1.1) TAN-D2-Q4 Aperture LRBB compensator β aspect ratio (if requested)

17. Crossing angle design places a role in D2 aperture: Using more strength in Q4/Q5 correctors reduces overall orbit corrector strength, but introduce orbit in D2 and TAXN. If orbit correction is needed for crab cavity alignment worst case aperture scenarios should be taken. 17 D2-Q4-Q5 Orbit offset slope M. Fitterer

18. New D2-Q4 octagonal beam screens have been designed, no tolerances given yet. Q5 beam screens (MQY) oriented for collision optics aperture optimizations. 18 D2-Q4-Q5 Aperture Aligment tolerances r [mm] h [mm] v [mm] D20.841.361 Q4/Q50.841.260.6 J. Jeanneret, LHC rep 1007 D2 Q4 C. Garion

19. 19 TAXN Aperture 12 σ envelopes with beam margins fit in the TAXN aperture by design (aperture separation from 145 mm to 154 mm). Tight constraints for flat optics. Round optics (2 mm sep.) Flat optics (0.75 mm sep.) Aperture to be re-optimized for new optics and validated with energy deposition studies. M. Fitterer

20. 20 D2 Aperture 12 σ envelopes with beam margins fit in the D2 aperture. Tighter constraints for flat optics. Orbit optimized for aperture (up to few mm separation more in worst case scenarios). Round optics (2 mm sep.) Flat optics (0.75 mm sep.)

21. 21 Q4 and MCBYY Apertures 12 σ envelopes with beam margins well fit. Round optics Flat optics

22. 22 Q5 Apertures 20 σ envelopes with beam margins well fit for round, barely for flat. Round optics left Flat optics Round optics right

23. 23 Q6 Apertures Round optics left Flat optics Round optics right 20 σ envelopes with beam margins well fit for round, barely for flat.

24. 24 Aperture summaries Round [σ] Flat [σ] Target [σ] Comments [σ] TAXS12.0511.1012no IP shift Q115.8114.2712reduced sep. for flat Q2-Q311.5611.3812reduced sep. for flat D112.2411.8712reduced sep. for flat TAXN14.7212.0812Ok D217.5513.9912ok with TCT5 Q4 & co21.5517.1212ok with TCT5 (to be studied w/o) Q526.9419.0920to be studied (likely ok) Q625.9218.3220to be studied (likely ok) No mechanical tolerances for new apertures yet (aperture will reduce). With new layout and optics TAXS to D1 about 5% aperture reduction. Status for HL-LHCV1.1

25. Aperture in the triplets are tight for nominal β*: Improve beam control to reduce beam margins, Improve cleaning strategies and impedance to reduce collimator gaps, Reduce mechanical tolerances, Increase nominal β*. Final results pending mechanical tolerances for triplet beam screen. BPM not modelled yet (no prob in principle). 25 Conclusion and outlook

26. Aperture in the TAXN-D2-Q4 is comfortable for nominal β* with TCT 5: waiting new optics for confirmations, good outlook, margins helps in machine availability and reliability, optics variants for crab voltage or wires can use the margins. Aperture in Q5-Q6 in the arc should be verified by collimations study to check if 20 σ is too strict. TAXS reduced aperture pending justification, aperture review needed. TAXN aperture definition pending new layout and optics. Final results pending mechanical tolerances for all new beam screens, TAXS and TAXN. 26 Conclusion and outlook