1. Off-momentum tail scraping for passive abort gap cleaning (MD 444) D. Mirarchi, R. Bruce, S. Redaelli On behalf of the LHC Collimation Team LHC Study Working Group, 14 th July 2015

2. Motivation Main goals and possible gains for the machine:  Study the possibility to establish a passive AG cleaning (throughout the whole cycle)  Sharing of losses between IR3 and IR7 Main experimental steps II.Once steady conditions are achieved, the jaws is opened in one step Lifetime of warm magnets in the two insertions Tests were performed as End of Fill MD the 16 th December 2012, at 4 TeV and 25 ns spacing: Demonstrated that similar level of AG population obtained with active method can be achieved Loss sharing between the two IRs can be obtained with predicted collimator settings Measured off-momentum tail population Measured AG re-population rate I.IR3-TCP jaws on the negative off-momentum side closed in steps while keeping IR7-TCP still the bottleneck for particles in the bucket Main goal of this MD: reproduce with present machine parameters such results to possibly deploy new IR3 settings (CERN-ACC-NOTE-2014-0061, 6 th LBOC in 2013) 14/07/15LSWG, Daniele Mirarchi2

3. MD request 14/07/15 Time required: 8h (2x4h) Species: Protons Category: End of Fill MD Beam: Both Beam energies:  Flat top Optics:  Nominal Only changes of IR3-TCPs settings are required Parallel studies are not possible Detailed procedures and collimator settings ready  Bunch length: 1  Bunch intensity (10 11 ppb): 1.1  Number of bunches: up to several trains  Transverse emittance (μm): 3.75 Beam Parameters: Example of active/passive AG cleaning Example of loss sharing between IR3-IR7

4. Improved off-momentum loss maps (MD 275) D. Mirarchi, S. Redaelli, B. Salvachua, G. Valentino P. Baudrenghien, M. Jaussi, H. Timko On behalf of the LHC Collimation Team and RF Team LHC Study Working Group, 14 th July 2015

5. Motivation Main goals and possible gains for the machine:  Reduce at least by a factor two the number of fill needed for off-momentum LM at 6.5 TeV Main experimental steps I.Longitudinal blow-up induced through RF noise II.Frequency shift adequate to evaluate beam loss in IR3-DS, but without losing the beam III.Back to nominal frequency, and then shift on the opposite sign Good results achieved during the commissioning using manual method (requires presence of experts) Smaller RF freq. shift needed than used now Transversally wider bunches in IR3 (high dispersion) Consistent results obtained w.r.t. std. method Java application in preparation to automatically use gentle method in operation, without presence of experts Main goal of the MD: final test of software developed to use gentle method in operation η(B2)=5.5e-4 η(B1)=1.5e-3 η(B2)=5.1e-4 η(B1)=1.7e-3 Standard Gentle

6. MD request 14/07/15LSWG, Daniele Mirarchi Time required: 12h Species: Protons Category: Normal MD Beam: Both Beam energies:  Flat top Optics:  Top energy  Squeezed Only cavities HV and RF frequency change is required Parallel studies are not possible Detailed procedures and collimator settings ready  Bunch length: 1  Bunch intensity (10 11 ppb): 1.1  Number of bunches: 3  Transverse emittance (μm): 3.75 Beam Parameters: Standard Gentle

7. Crystal Collimation (MD 333) D. Mirarchi, S. Redaelli, W. Scandale On behalf of the LHC Collimation Team and UA9 Collaboration LHC Study Working Group, 14 th July 2015

8. Motivation 14/07/15LSWG, Daniele Mirarchi8 Future LHC upgrades may demand for improved cleaning performance Different advanced collimation concepts are under study: Crystal collimation represents a promising option to improve cleaning performance (factor ~ 10 better a top energy) and reduce impedance (less IR7 collimators in place) Promising results have been obtained in the SPS:  Feasibility studies in the LHC itself are mandatory before relying on this approach for future upgrades Main goals of first tests in the LHC: 2)Perform angular scan to find crystal channeling at 450 GeV. (also at 6.5 TeV if enough time) Two crystals (H&V planes) have been installed during LS1 in the IR7 (Beam 1) 1)Verify with LHC beam if the installed hardware (crystals and goniometers) are adequate and fulfil the required specs (critical check to decide on potential upgrades at the end of 2015) Strong reduction of off-momentum leakage observed when in channeling w.r.t. amorphous orientation Piezo goniometer (LHC style) successfully tested during last MD in the SPS 3)Perform betatron loss maps with ADT for direct comparison with present system.

9. MD request 14/07/15LSWG, Daniele Mirarchi9 Time required: 16h (or 2x8h) Species: Protons Category: Normal MD Beam: Beam 1 Beam energies:  Injection  Flat top (if tests at inj. fast enough) Optics: Nominal Only changes of collimator settings are required Parallel studies could be performed in Beam 2. (Crystals installed only in Beam 1) Detailed procedures and collimator settings ready  Bunch length: 1  Bunch intensity (10 11 ppb): 0.5  Number of bunches: several  Transverse emittance (μm): 3.75 Beam Parameters: Standard Crystal Expected performance at 6.5 TeV

10. Backup 14/07/15LSWG, Daniele Mirarchi10

11. Backup MD 333 Simulation tools fully benchmarked, and SPS data successfully reproduced: Off-momentum leakage on 1 st dispersive peakOff-momentum leakage on 2 nd dispersive peak Reductions: Measurement = 8.3 ± 2.0 Simulation = 9.1 ± 0.1 Reductions: Measurement = 18.1 ± 2.8 Simulation = 20.1 ± 1.5 14/07/15LSWG, Daniele Mirarchi11

12. 14/07/15LSWG, Daniele Mirarchi12 Backup MD 333 Expected performance during first tests in the LHC: StandardCrystal CH AM

13. Backup MD 333 Piezo goniometer successfully tested during last MD in the SPS (7 th July 2015) Angular scan performed with angular speed of 0.5μrad/s Average angular stability < 0.3μrad. Improvements expected after intervention during next TS. Beam instability

14. Active halo control (MD 312) R. Bruce, S. Redaelli On behalf of the LHC Collimation Team LHC Study Working Group, 14 th July 2015

15. 15 MD 312: Active halo control Could possibly be done in parallel with crystal MD on other beam (with ADT). In Run 1: Seen loss spikes and beam dumps during orbit jitter, when beam is scraped on the primary collimators. Potential issue in Run II and HL-LHC. P ossible mitigation: halo cleaning with hollow electron lens, under consideration for HL-LHC Alternatives using existing hardware: ADT excitation or tune ripple to excite the halo without perturbing the core ( https://espace.cern.ch/lhc-machine-committee/ Presentations/1/lmc_197/HL_LHC_halo_RBruce.pptx ) This MD: first investigation of feasibility at injection in “easy” conditions, increase tune spread with octupoles Procedure: Inject, measure halo, excite, re-measure To measure halo: use collimator scans (destructive) or wire scanner with high gain – Setup time ideally needed beforehand. Working halo measurement could be very good also for other purposes / MDs Collimation team in collaboration with O. Bruning, B. Dehning, R. de Maria, M. Giovannozzi, M. Fitterer, W. Hofle, T. Pieloni, G. Stancari, H. Thiesen, D. Valuch