Performance limitations of the present LHC and LHC

  • Slides: 48
Download presentation
Performance limitations of the present LHC and LHC luminosity upgrade paths triplet magnets F.

Performance limitations of the present LHC and LHC luminosity upgrade paths triplet magnets F. Ruggiero CERN BBLR CARE-HHH-AMT WAMDO Workshop, CERN, 3– 6 April 2006

Outline • • Beam-beam limit and nominal LHC performance Luminosity optimization and operational margins

Outline • • Beam-beam limit and nominal LHC performance Luminosity optimization and operational margins LHC upgrade paths and beam induced heat loads Catalog of beam performance limitations • IR aperture: flat beams and quad re-alignment • Magnet quench limits • Collimation, impedance, and beam intensity • Electron cloud effects • Feedback systems and emittance preservation F. Ruggiero CERN Performance limitations of the present LHC

Beam-Beam tune spread for round beams tune shift from head-on collisions (primary IP’s) tune

Beam-Beam tune spread for round beams tune shift from head-on collisions (primary IP’s) tune shift from long-range collisions npar parasitic collisions around each IP increases for closer bunches or reduced crossing angle limit on x. HO limits Nb/(g ) relative beam-beam separation for full crossing angle qc x. HO / IP SPS Tevatron (pbar) RHIC LHC (nominal) 0. 005 0. 01 -0. 02 0. 0034 high-lumi in IP 1 and IP 5 (ATLAS and CMS), halo collisions in IP 2 (ALICE) and low-lumi in IP 8 (LHC-b) F. Ruggiero CERN no. of IP’s 3 2 4 3 DQbb total 0. 015 0. 02 -0. 04 ~0. 008 ~0. 01 conservative value for total tune spread based on SPS collider experience Performance limitations of the present LHC

Beam-Beam tune footprints Tune footprints corresponding to betatron amplitudes extending from 0 to 6

Beam-Beam tune footprints Tune footprints corresponding to betatron amplitudes extending from 0 to 6 s for LHC nominal (red-dotted), ultimate (greendashed), and “large Piwinski parameter” configuration (blue-solid) with alternating H-V crossing only in IP 1 and IP 5. F. Ruggiero CERN Performance limitations of the present LHC

LHC working points in collision The beam-beam tune footprint has to be accommodated in

LHC working points in collision The beam-beam tune footprint has to be accommodated in between low-order betatron resonances to avoid diffusion and bad lifetime. More resonance-free space near the coupling resonance good coupling compensation may allow DQbb~0. 015 F. Ruggiero CERN Performance limitations of the present LHC

Luminosity optimization transverse beam size at IP normalized emittance peak luminosity for head-on collisions

Luminosity optimization transverse beam size at IP normalized emittance peak luminosity for head-on collisions round beams, short Gaussian bunches • • • Nb/en beam brightness head-on beam-beam space-charge in the injectors transfer dilution • • I = nbfrev. Nb total beam current long range beam-beam collective instabilities synchrotron radiation stored beam energy Collisions with full crossing angle qc reduce luminosity by a geometric factor F maximum luminosity below beam-beam limit ⇒ short bunches and minimum crossing angle (baseline scheme) H-V crossings in two IP’s ⇒ no linear tune shift due to long range total linear bb tune shift also reduced by F F. Ruggiero CERN Performance limitations of the present LHC

Minimum crossing angle Beam-Beam Long-Range collisions: • perturb motion at large betatron amplitudes, where

Minimum crossing angle Beam-Beam Long-Range collisions: • perturb motion at large betatron amplitudes, where particles come close to opposing beam • cause ‘diffusive’ (or dynamic) aperture, high background, poor beam lifetime • increasing problem for SPS, Tevatron, LHC, i. e. , for operation with larger # of bunches dynamic aperture caused by npar parasitic collisions around two IP’s angular beam divergence at IP F. Ruggiero CERN higher beam intensities or smaller b* require larger crossing angles to preserve dynamic aperture and shorter bunches to avoid geometric luminosity loss baseline scaling: c~1/√b* , z~b* Performance limitations of the present LHC

Various LHC upgrade options parameter symbol [unit] number of bunches protons per bunch nb

Various LHC upgrade options parameter symbol [unit] number of bunches protons per bunch nb Nb [1011] tsep [ns] I [A] n [µm] bunch spacing average beam current normalized emittance longitudinal profile full crossing angle Piwinski parameter peak luminosity lifetime L [1034 cm-2 s-1] t. L [h] events per crossing luminous region length F. Ruggiero lum [mm] CERN ultimate 2808 1. 15 2808 1. 7 25 0. 58 25 0. 86 3. 75 Gaussian z [cm] b* [m] c [µrad] c z/(2 *) rms bunch length ß* at IP 1&IP 5 nominal 7. 55 0. 55 shorter bunch 5616 longer bunch 936 1. 7 12. 5 6. 0 75 1. 72 3. 75 1. 0 3. 75 Gaussian 7. 55 3. 78 flat 14. 4 285 0. 64 0. 50 315 0. 25 445 0. 25 430 0. 75 2. 8 1. 0 15. 5 2. 3 11. 2 9. 2 6. 5 8. 9 4. 5 19 44 88 510 44. 9 42. 8 21. 8 36. 2 Performance limitations of the present LHC

Heat loads per beam aperture for various LHC upgrade options parameter symbol [unit] nominal

Heat loads per beam aperture for various LHC upgrade options parameter symbol [unit] nominal ultimate protons per bunch spacing Nb [1011] tsep [ns] I [A] 1. 15 25 1. 7 25 average beam current longitudinal profile 0. 58 Gaussian z [cm] rms bunch length Average electron-cloud 7. 55 shorter bunch 1. 7 longer bunch 6. 0 12. 5 1. 72 75 1. 0 0. 86 Gaussian 7. 55 3. 78 flat 14. 4 1. 07 (0. 44) 1. 04 (0. 59) 13. 34 (7. 85) 0. 26 (0. 26) Synchrotron radiation heat P [W /m] g load at 4. 6– 20 K 0. 17 0. 25 0. 50 0. 29 Image currents power at PW [W /m] 0. 15 0. 33 1. 87 0. 96 Pgas [W /m] 0. 038 (0. 38) 0. 056 (0. 56) 0. 113 (1. 13) 0. 066 (0. 66) heat load at 4. 6– 20 K in the arc for R =50% and dmax=1. 4 (in parentheses for dmax=1. 3) Pecloud [W /m] load at 4. 6– 20 K Beam-gas scattering heat load at 1. 9 K for 100 -h beam lifetime (in parentheses for a 10 -h lifetime). It is assumed that elastic scattering (~40% of the total cross section) leads to local losses. F. Ruggiero CERN Performance limitations of the present LHC

LHC performance limitations from IR optics constraints • The triplet aperture is completely filled

LHC performance limitations from IR optics constraints • The triplet aperture is completely filled for nominal LHC conditions • However there are two ways to better use the available aperture with “minimal” modifications: • Flat beams • IR quadrupole re-alignment F. Ruggiero CERN Performance limitations of the present LHC

Luminosity with Flat Beams Flat beams means aspect ratio r ≠ 1 at the

Luminosity with Flat Beams Flat beams means aspect ratio r ≠ 1 at the IP: The X-ing plane is always the plane where the beam size is largest at the IP (i. e. smallest at the triplet): • • To gain aperture in the triplet (smaller X-ing angle and better matching of beam aspect ratio to beam-screen shape) To gain luminosity (geometric loss factor closer to unity) F. Ruggiero CERN Performance limitations of the present LHC

Flat beams • • • Interesting approach, flat beams may increase luminosity by ~20

Flat beams • • • Interesting approach, flat beams may increase luminosity by ~20 -30% with reduced crossing angle Symmetric doublets studied by J. Johnstone (FNAL) require separate magnetic channels, i. e. dipole-first, Crab cavities or special quads Tune footprints are broader than for round beams, since there is only partial compensation of parasitic beam-beam encounters by the H/V crossing scheme. More work needed to evaluate nonlinear resonance excitation. Probably requires BB Long Range compensation Recently S. Fartoukh has found an interesting flat beam solution with anti-symmetric LHC baseline triplets F. Ruggiero CERN Performance limitations of the present LHC

Beam aspect ratio vs triplet aperture beam screen orientation for H/V scheme Effect of

Beam aspect ratio vs triplet aperture beam screen orientation for H/V scheme Effect of decreasing the beam aspect ratio at the IP (and increasing the vert. X-angle) Effect of increasing the beam aspect ratio at the IP (and decreasing the vert. X-angle) ⇒ Find the optimum matching between beam-screen and beam aspect ratio CERN F. Ruggiero Performance limitations of the present LHC

Pushing the LHC luminosity by 10 -20% [cm] by* [cm] c [mrad] n 1

Pushing the LHC luminosity by 10 -20% [cm] by* [cm] c [mrad] n 1 at triplet geometric lumi loss [%] L/Lnom 55 55 285 ~7 83. 9 1. 00 110 27. 5 201 ~7 95. 1 1. 13 Flat r=1. 6, b*=55 cm 88 34. 4 225 ~7. 5 92. 7 1. 10 Flat r~1. 7, b* 51 cm 88 30 225 ~7 92. 7 1. 18 Case Nominal r=1, b*=55 cm Flat r=2, b*=55 cm bx* All these cases are allowed by the nominal LHC hardware: layout, power supply, optics anti-symmetry, beam screen orientation in the triplets (only changing the present H/V scheme into V/H scheme) F. Ruggiero CERN Performance limitations of the present LHC

IR quadrupole re-alignment (R. Tomàs) • • • Aperture gain of up to 6

IR quadrupole re-alignment (R. Tomàs) • • • Aperture gain of up to 6 mm by Q 2 re-alignment Find optimum for aperture and/or energy deposition Present orbit correctors may not be strong enough F. Ruggiero CERN Performance limitations of the present LHC

Magnet quench levels follow-up of CARE-HHH-AMT workshop (P. Pugnat) Review of past estimates for

Magnet quench levels follow-up of CARE-HHH-AMT workshop (P. Pugnat) Review of past estimates for LHC dipoles (D. Leroy) • Continuous losses: 10 m. W/cm 3 or 0. 4 W/m of cable produces T < 0. 2 K with the insulation selected for MBs ~107 p/s at 7 Te. V • Transient losses: enthalpy margin 1 m. J/cm 3 from insulated conductor and 35 m. J/cm 3 from LHe (if tloss > 8 ms) LHC & Magnet Operation (R. Schmidt & S. Fartoukh) • During the ramp, quench margins of MB’s & MQ’ decrease significantly • During the squeeze the margin of some quadrupoles in experimental insertions could decrease. Quench Levels and Transient Beam Losses at HERA (K. Wittenburg) • Empirical approach: • adiabatic approximation for quench level: 2. 1 m. J/cm 3 for DTcs = 0. 8 K • cooling & MPZ concept taken as safety margins, • x 16 the threshold in p/s for continuous loss rate (from Tevatron) • Experiences & Lessons: • Quenches occurred at about a factor 5 below expectation • BLM’s cannot protect againstantaneous losses F. Ruggiero CERN Performance limitations of the present LHC

Insertion Magnets and Beam Heat Loads Conclusions for LHC IR magnets • Heat loads

Insertion Magnets and Beam Heat Loads Conclusions for LHC IR magnets • Heat loads associated to pp collisions are considerable in the experimental insertions, in particular in the low-beta triplets. • Thermal properties of the coils of both types of low-beta quadrupoles were experimentally studied, and confirm a safety factor of 3 with respect to expected heat load for nominal luminosity. • MQM and MQY quadrupoles have insulation schemes analogous to the MB. Similar thermal properties could be expected, but have not been experimentally verified. • Magnets operating at 4. 5 K are expected to have higher quench limits for transient losses, but lower for continuous losses than at 1. 9 K. R. Ostojic, AT/MEL 17

Estimate of Quench Limits Example of Results for transient losses (Available for all LHC

Estimate of Quench Limits Example of Results for transient losses (Available for all LHC magnet types) Enthalpy (m. Joule/cm 3) Magnet type MB MB MQ MQMC MQML MQM MQML MQY Cable type Type-1 Type-2 Type-3 Type-4 Type-7 Type-4 Type-5 Type-6 Op-T (K) 1. 9 1. 9 4. 5 < 0. 1 ms Slow perturbation (no insulation) > 100 ms 1. 54 1. 45 4. 24 1. 51 2. 41 2. 89 3. 80 56. 55 56. 41 70. 53 49. 97 9. 87 12. 15 15. 31 Fast perturbation from A. Siemko et al. , CERN LTC 19 October 2005 F. Ruggiero CERN Performance limitations of the present LHC

Efficiency of the Cleaning System n The LHC Cleaning System should allow to run

Efficiency of the Cleaning System n The LHC Cleaning System should allow to run the machine close to the quench limit of the super-conducting magnets for the specified lifetime: Allowed intensity Quench threshold (7. 6 × 106 p/m/s @ 7 Te. V) Cleaning inefficiency = Number of escaping p (>10 s) Number of impacting p (6 s) Beam lifetime (e. g. 0. 2 h minimum) Dilution Length (50 m) => SIMPLIFIED DEFINITION OF QUENCH LIMIT ! => Major role of the quench limit on maximum intensity of the machine ! G. Robert-Demolaize

Maximum allowed intensity n To achieve LHC design intensity, we require the following local

Maximum allowed intensity n To achieve LHC design intensity, we require the following local cleaning inefficiencies: (assuming simplified quench limits). => used as input for quench limits in loss maps! G. Robert-Demolaize

Phase 1 – Injection & Early Physics G. Robert-Demolaize

Phase 1 – Injection & Early Physics G. Robert-Demolaize

Phase 2 – Collision Optics G. Robert-Demolaize

Phase 2 – Collision Optics G. Robert-Demolaize

Overall System Status 7 Te. V • Status Chamonix 2005: Up to 5 times

Overall System Status 7 Te. V • Status Chamonix 2005: Up to 5 times above quench limit at various locations in experimental insertions… S. Redaelli et al, Chamonix 2005 LHC Collimation Team 0. 2 h lifetime. Perfect cleaning & beam set-up. 23

Latest 7 Te. V Results with Collimation Full LHC System • Understand LHC collimation

Latest 7 Te. V Results with Collimation Full LHC System • Understand LHC collimation system better and better… Black thin lines: Blue lines: Red lines: Collimators SC aperture Warm aperture Fixed successfully all quench problems around the ring (tertiary collimators), except basic system limitation downstream of IR 7! (Convert blue spikes into black spikes) 7 Te. V, 0. 2 h lifetime, perfect cleaning&beam LHC Collimation Team Compatible with expected limitation from impedance (~50%). Improve with phase 2! 24

prototype LHC collimator installed in the SPS (R. Assmann) 25 Frank Zimmermann, GSI Meeting

prototype LHC collimator installed in the SPS (R. Assmann) 25 Frank Zimmermann, GSI Meeting 31. 03. 2006

Collimator-Induced Tune Change (Changing Collimator Gap) Gap: 2. 1 51 mm M. Gasior, R.

Collimator-Induced Tune Change (Changing Collimator Gap) Gap: 2. 1 51 mm M. Gasior, R. Jones et al SPS tune depends on collimator gap! Expected tune change observed within factor 2! Impedance estimates are strongly confirmed by experiment! F. Zimmermann et al R. Assmann 26

generalized formula: combine correct frequency dependence of Burov-Lebedev with nonlinear dependence on transverse coordinates

generalized formula: combine correct frequency dependence of Burov-Lebedev with nonlinear dependence on transverse coordinates from Piwinski, assuming that the two dependencies remain factorized new generalized formula Frank Zimmermann: nearly perfect agreement! measurement 27 Frank Zimmermann, GSI Meeting 31. 03. 2006

LHC graphite collimators • • One may think that the classical “thick-wall” formula applies

LHC graphite collimators • • One may think that the classical “thick-wall” formula applies also for 2 cm thick graphite collimators about 2 mm away from the beam In fact it is not The resistive impedance is ~ 2 orders of magnitude lower at ~ 8 k. Hz! Usual regime: F. Ruggiero New regime: CERN Performance limitations of the present LHC

LHC stability diagram (maximum octupole strength) and collective tune shift for the most unstable

LHC stability diagram (maximum octupole strength) and collective tune shift for the most unstable coupled-bunch mode at 7 Te. V (E. Metral, 2004) All the machine with Cu coated (5 μm) collimators All the machine Without collimators (TCDQ+RW+BB) F. Ruggiero CERN Performance limitations of the present LHC

Stability diagrams (vertical plane) LHC at 7 Te. V Phase 2 collimators: ~70% of

Stability diagrams (vertical plane) LHC at 7 Te. V Phase 2 collimators: ~70% of the nominal LHC intensity can be stabilized using Landau octupoles at zero chromaticity Mode 0 Mode 1 Mode 2 Mode 3 Elias Métral, RLC meeting, 03/02/06 30

Machine Protection and Collimation challenges • Magnet quench limits need to be experimentally validated

Machine Protection and Collimation challenges • Magnet quench limits need to be experimentally validated Fresca test facility and LHC sector test • Beam Loss Monitors need proper calibration for efficient machine protection LHC sector test • Learn how to set-up routinely a complicated three-stage collimation system control beta-beating at ~10% level • Phase-2 collimation system is not compatible with nominal LHC intensity at 7 Te. V, if we want to stabilize the beams using Landau octupoles at zero chromaticity: • • use low-noise transverse feedback and chromaticity to stabilize the beams? octupoles are “passive” and more reliable ideal to push machine performance and reduce experimental background levels active feedback may increase emittance and reduce luminosity investigate crystal assisted collimation and/or develop new lowimpedance collimators (e. g. , longitudinally segmented or incorporating Cu stripes to carry low-frequency image currents? ) F. Ruggiero CERN Performance limitations of the present LHC

LHC strategy against Electron Cloud 1) warm sections (20% of circumference) coated by Ti.

LHC strategy against Electron Cloud 1) warm sections (20% of circumference) coated by Ti. Zr. V getter developed at CERN; low secondary emission; if cloud occurs, ionization by electrons (high cross section ~400 Mbarn) aids in pumping & pressure will even improve 2) outer wall of beam screen (at 4 -20 K, inside 1. 9 -K cold bore will have a sawtooth surface (30 mm over 500 mm) to reduce photon reflectivity to ~2% so that photoelectrons are only emitted from outer wall & confined by dipole field 3) pumping slots in beam screen are shielded to prevent electron impact on cold magnet bore unique vacuum sys 4) rely on surface conditioning (‘scrubbing’); commissioning strategy; as a last resort doubling or tripling 32 bunch spacing suppresses e-cloud heat load Frank Zimmermann, LHC Electron Cloud, GSI Meeting 30. 03. 2006

arc heat load vs. intensity, 25 ns spacing, ‘best’ model R=0. 5 ECLOUD simulation

arc heat load vs. intensity, 25 ns spacing, ‘best’ model R=0. 5 ECLOUD simulation dmax=1. 7 dmax=1. 5 BS cooling capacity injection dmax=1. 3 -1. 4 suffices Frank Zimmermann, LHC Electron Cloud, GSI Meeting 30. 03. 2006 low luminosity high luminosity dmax=1. 1 calculation for 1 train computational challenge!33 higher heat load for quadrupoles in 2 nd train under study

is “scrubbing” needed in LHC? v still lacking experimental data, e. g. , on

is “scrubbing” needed in LHC? v still lacking experimental data, e. g. , on emax(q) uncertainty in heat load prediction of factor ~2 v also incomplete understanding of scrubbing (COLDEX data vs. prediction, RHIC, DAFNE) v if dmax~1. 3 reached in commissioning, no scrubbing is needed for heat load and fast instabilities v pressure should be ok too according to N. Hilleret v one concern: long-term emittance growth and poor lifetime (observed in SPS after scrubbing) v we still believe we need to prepare a scrubbing strategy in case it turns out to be necessary to go to dmax~1. 3 (e. g. , tailor train spacings & train lengths at nominal bunch intensity) 34 Frank Zimmermann, LHC Electron Cloud, GSI Meeting 30. 03. 2006

Instabilities & emittance growth caused by the electron cloud 1) Multi-bunch instability – not

Instabilities & emittance growth caused by the electron cloud 1) Multi-bunch instability – not expected to be a problem can be cured by the feedback system 2) single-bunch instability – threshold electron cloud density r 0~4 x 1011 m-3 at injection in the LHC 3) incoherent emittance growth 4) new understanding! (CERN-GSI collaboration) 2 mechanisms: Ø periodic crossing of resonance due to e- tune shift and synchrotron motion (similar to halo generation from space charge) Ø periodic crossing of linearly unstable region due to synchrotron motion and strong focusing from electron cloud in certain regions, e. g. , in dipoles F. Ruggiero CERN Performance limitations of the present LHC

Resonance Trapping (G. Franchetti, GSI) The same resonance trapping mechanism can explain slow emittance

Resonance Trapping (G. Franchetti, GSI) The same resonance trapping mechanism can explain slow emittance growth and beam losses observed with space charge in the PS (left) and with electron cloud in the SPS (below) Particles with large synchrotron amplitudes reach larger and larger betatron amplitudes and are lost bunch shortening Particle losses are enhanced by chromaticity F. Ruggiero CERN Performance limitations of the present LHC

single-bunch “TMC” instability fast e growth above e- density threshold; slower e growth below

single-bunch “TMC” instability fast e growth above e- density threshold; slower e growth below “Transverse Mode Coupling Instability (TMCI)” for e- cloud (r > rthresh) re = 3 x 1011 m-3 Long term emittance growth (r < rthresh) re = 2 x 1011 m-3 E. Benedetto Frank Zimmermann, LHC Electron Cloud, GSI Meeting 30. 03. 2006 re = 1 x 1011 m-3 LHC, Q’=0, 37 at injection

Electron density vs LHC beam intensity Challenge: how to go from dmax~1. 7 to

Electron density vs LHC beam intensity Challenge: how to go from dmax~1. 7 to 1. 3? Scrubbing should be done at nominal Nb (stripes) R=0. 5 ECLOUD simulation dmax=1. 7 dmax=1. 5 dmax=1. 3 dmax=1. 1 F. Ruggiero CERN typical “TMCI” instability threshold calculation for 1 bunch train Performance limitations of the present LHC

ξx=0. 15 ξy=0. 1 bunch intensity (au) Qx=26. 135 Qy=26. 185 rms bunch length

ξx=0. 15 ξy=0. 1 bunch intensity (au) Qx=26. 135 Qy=26. 185 rms bunch length (ns) LHC bunch train at injection in the SPS VRF ~ 3 MV dampers on coupling: 0. 008 time (min) Evolution of bunch length and bunch population for the first and the last bunch in an LHC bunch train of 72 bunches. SPS measurements with electron cloud in Aug 2004. Courtesy G. Rumolo, G. Arduini, and F. Roncarolo. F. Ruggiero CERN Performance limitations of the present LHC

 • • • Tentative Conclusions Some “safety nets” in the original LHC conceptual

• • • Tentative Conclusions Some “safety nets” in the original LHC conceptual design (low-impedance, stabilization by octupoles, full triplet aperture without beam screens) have been sacrificed to guarantee a more robust collimation system and a safer IR vacuum behaviour Machine downtime caused by magnet quenches may be initially frequent, until collimation and machine protection are fully mastered A shorter machine turnaround time implies reliable tables of quench levels, BLM calibrations, and a dynamic optics control (reference magnets) Emittance control will be challenging and may require crystal assisted collimation and/or new lownoise feedback systems. A longitudinal feedback may enable shorter bunches and reduce geometric luminosity loss for lower b*. F. Ruggiero CERN Performance limitations of the present LHC

Tentative Conclusions (continued) • • Reaching nominal LHC performance is challenging Some uncertainties remain

Tentative Conclusions (continued) • • Reaching nominal LHC performance is challenging Some uncertainties remain in connection with electron cloud effects and vacuum behaviour of the cold arcs: exceeding nominal beam current may be impossible or take several years operation with 75 ns bunch spacing would reduce e-cloud & long range beam-beam effects and maximize luminosity Operation with flat beams can help relaxing IR aperture constraints and/or increasing luminosity A re-alignment of the IR quads would further relax aperture constraints, increase luminosity, and minimize energy deposition in the magnet coils. This option should be considered also for the IR upgrade. F. Ruggiero CERN Performance limitations of the present LHC

Tentative Conclusions for the LHC IR Upgrade • • • We do need triplet

Tentative Conclusions for the LHC IR Upgrade • • • We do need triplet spares and thus a back-up or intermediate IR upgrade option based on Nb. Ti magnet technology. What is its luminosity reach? A vigorous R&D programme on Nb 3 Sn magnets should start at CERN asap, complementary to the US-LARP programme, to reach an LHC luminosity of ~1035 after 2015 Alternative IR layouts (quadrupole-first, dipolefirst, D 0, flat beams, Crab cavities) will be rated in terms of technological and operational risks/advantages by the end of 2006 F. Ruggiero CERN Performance limitations of the present LHC

Additional Slides F. Ruggiero CERN Performance limitations of the present LHC

Additional Slides F. Ruggiero CERN Performance limitations of the present LHC

HERA operational experience HERA: Ring of 6. 3 km - 422 sc main dipoles

HERA operational experience HERA: Ring of 6. 3 km - 422 sc main dipoles - 224 sc main quads - 400 sc correction quads - 200 sc correction dipoles From K. Wittenburg F. Ruggiero CERN Performance limitations of the present LHC

Heat load in the Low-b Triplet N. Mokhov et al, LHC Project Report 633

Heat load in the Low-b Triplet N. Mokhov et al, LHC Project Report 633 F. Ruggiero CERN Peak power density: 0. 45 m. W/g Performance limitations of the present LHC

Trapped modes for tertiary LHC collimator chambers (A. Grudiev, 2006) F. Ruggiero CERN Performance

Trapped modes for tertiary LHC collimator chambers (A. Grudiev, 2006) F. Ruggiero CERN Performance limitations of the present LHC

Vertical growth rate of head-tail modes in the LHC as a function of chromaticity

Vertical growth rate of head-tail modes in the LHC as a function of chromaticity at injection energy, for ~3000 bunches of nominal intensity At injection head-tail modes with growth rates up to about 4 sec-1 are stabilized by lattice nonlinearities (assuming an amplitude detuning of 0. 002 at 6 sigma). The rigid mode m=0 has to be stabilized by the transverse feedback. F. Ruggiero CERN 8 th ICFA Seminar, Daegu, Korea 29/09/2005

Stability diagrams (vertical plane) LHC at 7 Te. V Phase 1 collimators: ~50% of

Stability diagrams (vertical plane) LHC at 7 Te. V Phase 1 collimators: ~50% of the nominal LHC intensity can be stabilized using Landau octupoles at zero chromaticity Mode 0 Mode 1 Mode 2 Mode 3 F. Ruggiero CERN Performance limitations of the present LHC