1. HL-LHC optics S. Fartoukh, CERN-BE-ABP  Performance goal & basic ingredients  Optics & beam parameters  Optics limitations & the Achromatic Telescopic Squeezing (ATS) scheme  HL-LHC optics using the ATS  The preliminary HL-LHC shopping list  Conclusions 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting1

2. Performance goal & basic ingredients   L = 3000 fb -1 from  2022-2023 to  2035  250 fb -1 / year (estimated to 150 days of operation)   eff  40% machine efficiency required running at a levelled luminosity of L lev = 5 × 10 34  Long fill required (  10h including decay) compared to average turn around (estimated to  5h for LHC) to push  eff  Ingredients: 1. Higher current (× 1.5  × 1.9) first for beam life time. 2. Smaller emittance (÷1.25  ÷1.5) for “virtual luminosity”. 3. Smaller  * (÷4  ÷12) for “virtual luminosity”. 4. Crab-cavity (or flat optics with shorter bunch length) for “virtual luminosity”. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting2 Ideal case, F. Zimmerman

3. Baseline Optics & Beam Parameters 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting3 LHC nominalHL-LHC 25 ns HL-LHC 50 ns # Bunches2808 1404 p/bunch [10 11 ]1.15 (0.58A)2.2 (1.11 A)3.5 (0.88 A)  x,y  [  m] 3.752.53.0  L [eV.s] 2.5  z [cm] 7.5   p/p [10 -3 ] 0.1   [cm] 5515 X-angle [  rad]285 (9.5  )590 (12.5  )590 (11.4  ) Lumi loss factor0.840.300.33 Peak lumi [10 34 ]1.07.28.3 Virtual lumi [10 34 ] (with hour-glass effect) 1.221.723.1 T leveling [h] @ 5E34n/a8.97.3 #Pile up @5E3425123247  Prepare variants for the HL-LHC optics with even smaller   and/or flat optics (back-up in the absence of crab-cavity)  25 ns is the baseline, 50 ns is a back-up (e.g. for e-cloud).  Full agreement not yet reached with the LHC Injector Upgrade project (e.g. 3  m offered instead of 2.5  m emittance for the 25 ns case, but 2.2E11 bunch charge possibly reachable!)  Heavily relies on crab-cavity with a bare minimum of  10 MV / beam/ IR side. Latest HL-LHC beam parameters worked out by O. Brüning

4. Optics parameters“Baseline-HL”“Stretched-HL” Injection @ 450 GeV  * [m] 5.5 Full Xangle [  rad] 490 Half-parallel separation [mm]22 Collision round @ 7 TeV (X-angle set to 12.5  at 2.5  m emittance)  * [m] 0.150.10 Full Xangle [  rad] 590720 Collision flat @ 7 TeV (crossing in the plane of biggest  *, set to 16.5  at 2.5  m emittance)  * [m] (aspect ratio of 4 found optimal for aperture) 0.30/0.0750.20/0.05 Full Xangle [  rad] 550670  All these optics are now available in the latest optics & layout version of the HL-LHC: SLHCV3.1b (150 T/m-140 mm Nb3Sn IT) 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting4 Optics Parameters (baseline & variants)

5. A small digression: Why more than 10  for the X-angle  ? 25 ns, 10  475  rad  50 ns, 10  520  rad  25 ns, 590  rad (12.5  )50 ns, 590  rad (11.4  )  Tune footprint at 6  with 21 LR’s per IP side (longer IT), HO at IP1 and IP5,  *=15 cm and beam parameters (higher bunch charge) given in the previous table 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting5

6.  100’000 turns DA simulation results vs. X-angle confirming the “pathological tune footprint” (25 ns beam parameters,  *=15 cm, only sextupoles, LR and HO, no crab- crossing no field imperfection) Preliminary results from S. White 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting6

7. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting7 Optics Limitations & the ATS scheme (1/2)  Lowering  * needs magnets of larger aperture, but also new hardware or sophistication (crab-cavity, flat optics,...) to mitigate the luminosity loss due to the Piwinsky angle.  How to produce this  * ??? This is the aim of the ATS scheme which solves many optics limitations coming from the overall LHC ring. 1. Optics matchability to the arcs: – Some IR quads going to 0 T/m, others to max. field (200T/m). – Simply the matching section becomes too short at some point. 2. Correctability of the chromatic aberrations induced, not only Q’, but also Q’’, Q’’’,…, and off-momentum  -beating: – limitations from the arc sextupole strength (<600A).... Otherwise  * would be limited to 30 (25) cm with the NbTi (Nb3Sn) technology and indeed 120 mm would be optimum for the IT aperture !!!

8. A new injection optics (  /2 FODO lattice  new integer tunes) A squeeze in 2 steps 1) An “almost” standard squeeze, the Pre-squeeze:  acting on the matching quads of IR1 and IR5,  with new matching constraints on the left/right IR phase  till reaching some limits (sextupoles, matching quadrupoles). 2) A further reduction of  *, the Squeeze:  acting on IR2/8 for squeezing IR1 and IR4/6 for IR5,  inducing  -beating bumps in sectors 81/12/45/56 to boost the sextupole efficiency at constant strength. S. Fartoukh, CM18/HiLumi-LHC meeting807/05/2012 Optics Limitations & the ATS scheme (2/2)

9. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting9 Injection optics  * = 5.5 m at IP1 and IP5 (150 T/m IT gradient) HL-LHC optics using the ATS (1/8)

10. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting10 Pre-squeezed optics  * = 40 cm at IP1 and IP5 (150 T/m IT gradient) HL-LHC optics using the ATS (2/8)

11. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting11 Round Squeezed optics  * = 10 cm at IP1 and IP5 (150 T/m IT gradient) HL-LHC optics using the ATS (3/8)

12. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting12 Flat Squeezed optics  * = 20/5 cm at IP1 and IP5 (150 T/m IT gradient) HL-LHC optics using the ATS (4/8)  max = 55 km a factor of 12 above nominal!

13. Why does it work? The magic lies in the choice of the betatron phases.. Zoom in arc45: Pre-Squeeze to  * = 40/40 cm (round optics)   y   between strong SD’s (every other FODO cells)  y (Q11  IP ) = 1.25×  y with  y ~ 1/2 tan -1 (  min /  max )  arc ×  * ) V  cst  x   between strong SF’s (every other FODOcells)  x (Q10  IP ) = 0.75×  x with  x ~ - 1/2 tan -1 (  min /  max )  arc ×  * ) H  cst IR4 (RF insertion) IR5 (CMS insertion)   /2 phase in the arc cells   /2 on the left/right side of the IR  2 sextupole families per plane but only one used for triplet correction 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting13

14. Why does it work? The magic lies in the choice of the betatron phases.. Zoom in arc45: Squeeze to  * = 10/10 cm (round optics)   y   between strong SD’s (every other FODO cells)  y (Q11  IP ) = 1.25×  y with  y ~ 1/2 tan -1 (  min /  max )  arc ×  * ) V  cst  x   between strong SF’s (every other FODOcells)  x (Q10  IP ) = 0.75×  x with  x ~ - 1/2 tan -1 (  min /  max )  arc ×  * ) H  cst IR4 (RF insertion) IR5 (CMS insertion) 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting14

15. Why does it work? The magic lies in the choice of the betatron phases.. Zoom in arc45: Squeeze to  * = 20/5 cm (flat optics)   y   between strong SD’s (every other FODO cells)  y (Q11  IP ) = 1.25×  y with  y ~ 1/2 tan -1 (  min /  max )  arc ×  * ) V  cst  x   between strong SF’s (every other FODOcells)  x (Q10  IP ) = 0.75×  x with  x ~ - 1/2 tan -1 (  min /  max )  arc ×  * ) H  cst IR4 (RF insertion) IR5 (CMS insertion) 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting15

16. 16 Simulating the ATS in the existing LHC (IT @ 205 T/m) to deliver  * = 10 cm at IP1&5 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting Beam size [mm] and dispersion (IR4  IR6) at 3.5 TeV (for  =3.5 mm) IR4 IR5 IR6 Chromatic Montague functions over the full ring (off-momentum  -beating) Tunes vs.  p

17. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting17 The new crossing bump is closed at D2 before the crab-cavity, but requires 1. strong 2-in-1 orbit corrector at D2 in the X-plane: 105 mm, 7 Tm 2. strong single bore orbit corrector on the nIP side of Q3: 140-150 mm, 4-5 Tm HL-LHC optics using the ATS (5/8) Standard crossing scheme (closing at Q6) New crossing scheme (closing at D2) Idea from R. de Maria

18. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting18 An additional functionality of the ATS optics:  Correcting the huge spurious dispersion induced by the X-angle HL-LHC optics using the ATS (6/8) Up to 15-20 m of spurious dispersion in the IT @  *=10 cm! Correction to less than 1m via modest orbit bumps in the arcs CMS LHCb ATLAS Alice Closed orbit H & V Dispersion

19. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting19 Mechanical aperture: the largest is the better (“ 1 mm much more valuable than 1 T/m”) HL-LHC optics using the ATS (7/8)  Two cases showed: 140 mm IT/D1 with  * = 15 cm and 150 mm IT/D1 with  * = 10 cm  Brute aperture, i.e. with no budget for CO, spurious dispersion,  -beating,...  No beam-screen assumed in the IT/D1 but very thick cold bore (  10 mm) for shielding  New TAS, TAN, D2, Q4, Q5 (see later for the first aperture specification) Target of 14  at 7 TeV extrapolated at constant collimator & protection settings (in mm) from the present operation @ 4TeV. Target of 11.5  assuming new hardware (1-2  less might even be OK... being worked out in WP5): BPM at collimator (R. Assmann, R. Bruce, S. Redaelli et al.) and/or more robust TCTH ( for IT protection against asynchronous dump). Courtesy, R. De Maria

20. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting20 Dynamic aperture  see talk by Y. Cai on Tuesday afternoon ...the good field region is as important as the available aperture... “good” means IT harmonics of a few 10 -5 at 7 TeV to be compatible with the  * range of HL-LHC! HL-LHC optics using the ATS (8/8) In this respect, we should first convince ourselves that the Nb3Sn technology is the right choice for HL-LHC.  demonstrate rapidly that the 0.5-1 unit FQ level (at 2/3 of the aperture) is within reach at 7 TeV, with good hope for further improvement (keeping in mind that the requirements at 450 GeV are much less stringent, e.g. 20-30 units of b6 at Rr=50 mm).  keep in mind the  0.5 TeV uncertainty for the final energy of the LHC within which the FQ (e.g. b6) shall ideally not deviate by more than 0.1-0.2 unit w.r.t. 0.

21. 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting21 The preliminary HL-LHC shopping list 1. HW re-commissioning & modifications needed for the ATS - Re-commission at 600A the 16 SD families of sectors 81/12/45/56 - equip the 4 Q10’s of IR1/5 with an arc MSCB (sextupole + orbit corrector) instead of MCBC - replace Q5 in IR6 (MQY type, 3.2 m ×160 T/m) by a longer magnet (MQYL, e.g. 4.8 m ×160 T/m) 2. The main shopping list for LSS1 and LSS5 (corrector not included) EquipmentAperture [mm]Separation [mm] (for 2-in-1)Performance (T/m, T.m, MV,...) TAS60n/a IT140  150 (w/o beam- screen but shielding) n/a150 T/m  100 T/m D1140  150 (more might be needed for beam-screen) n/a35 T.m  40 T.m (depending on IT length, i.e. on IT gradient) TAN41/37 (elliptical) 145n/a D210518635 T.m  40 T.m Crab-cavity8019410 MV per beam, per IR side (+2.5MV to be fully compatible with  *=10cm) Q490194500 T/m×m Q570194750 T/m×m

22. ATS experiments at the LHC, S. Fartoukh et al. at IPAC’12 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting22 Conclusions  Work already very well-advanced, but as usual devil is in the details.  The field quality of the IT looks extremely challenging to fully profit from the large IT aperture (and from the ATS)  The crab-cavity voltage shall be pushed as much as we can if one hopes to fully profit from  * = 15 cm, if not 10 cm. ... and first ATS machine experiments cannot be more encouraging! After a single shift, a factor of only 2 was missing to demonstrate the HL-LHC  * !

23. ... Reserve 07/05/2012S. Fartoukh, CM18/HiLumi-LHC meeting23

24. 07/05/2012 S. Fartoukh, CM18/HiLumi-LHC meeting 24 What would happen for a “standard squeeze” to  * = 30 cm (120 T/m triplet) ? Sextupole powering scheme and gradients (beam1) at 7 TeV vs.  * Transition @  *=1.5 m 550A - 550A  *=30 cm  550A!  *=30 cm Q5/Q6 close to 0! Matching section (MS) 160 T/m

25. S. Fartoukh, CM18/HiLumi-LHC meeting25  Only 25% of the RS circuits participates to the chromatic correction during the pre-squeeze 10 cm  * < 40 cm During the telescopic part, the chromatic correction is achieved by the  -beating!  * > 40 cm 07/05/2012 Typical settings [A] at 3.5 TeV for the sextupole families (Beam1) testing the ATS in the LHC  All sextupole then kept ~ constant during the squeeze: THERE IS NO CHROMATIC LIMIT!