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LHC Luminosity upgrade s. L. Rossi Contribution from: A. Ballarino , Ed Ciapala , M. Karppinen , S. Fartouk , R. Ostojic, S. Russenschuck , L. Tavian, S. Weisz and all taskforce on LHC Lumi 2 nd CERN-MAC 26 April 2010.

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lhc luminosity upgrade s

LHC Luminosity upgrades

L. Rossi

Contribution from: A. Ballarino, Ed Ciapala, M. Karppinen, S. Fartouk, R. Ostojic, S. Russenschuck, L. Tavian, S. Weisz and alltaskforce on LHC Lumi

2nd CERN-MAC

26 April 2010

what has to be done to allow lhc to reliably reach design luminosity
What has to be done to allow LHC to reliably reach design luminosity?
  • Peak luminosity (1034): the triplet has been designed for the nominal  of 55 cm. Design luminosity will requires nominal intensity: collimation to handle 0.54 A, see talk later
  • There is margin “everywhere” : chromaticity, quench limit vs. heat deposition…
  • Damage level: 300-400 fb-1 (probably most critical is the nested orbit corrector magnet, more margin in the MQX…). Today this is expected not before 2020-2022.

LHC Lumi Up @ 2nd CERN-MAC

nominal luminosity caveats
Nominal luminosityCaveats
  • Long range beam-beam effects may turn to be a limit… opening the X-ing angle is a mitigation.
    • In this respect the – relatively small – aperture of the present triplet may already become a limitation.
    • Other ways to overcome this problem, if it appears before nominal luminosity (compensating wires…)
  • Collimation system.
    • Insufficient cleaning efficiency.
    • Insufficient compensation of impedance effect.
    • To compensate this shortfall, opening the collimators may be needed

LHC Lumi Up @ 2nd CERN-MAC

what needs to be done to allow lhc to reach ultimate luminosity
What needs to be done to allow LHC to reach ultimate luminosity
  • Ultimate peak luminosity (2.3 1034) should come from increase in intensity (0.86 A, in bunches of 1.7 1011 p)
  • However present triplet is limited to 1.7 1034mainly due to heat deposition from collision debris.
    • Is this a hard limit ?

LHC Lumi Up @ 2nd CERN-MAC

ultimate luminosity considerations to make it reliable
Ultimate luminosity: considerations to make it reliable
  • Larger aperture low beta quad is – most probably – necessary because previous limits may become hard:
    • Long range beam-beam
    • Collimator
    • Better shielding against radiation
  • Use of all installed cryogenic power per point side (500 W: today there is limitation of 300 W inside the triplet, first due to HX and then to longit. magnet conductance). The 300 W gives the limit L  1.7 1034 above mentioned.
  • Probably independent cooling of RF @ P4 is needed to re-establish full cooling power in IP5Left.
  • Displacements of Power Converter (and DFBs) of Inner Triplets to far distance, possibly on surface. Cold power based on Sc links needed.
  • All this makes that to reach, or to exploit reliably ultimate luminosity, the triplet - and IR region - must be upgraded.

LHC Lumi Up @ 2nd CERN-MAC

possible lhc lumi m lamont
Possible LHC lumi (M.Lamont)

LHC Lumi Up @ 2nd CERN-MAC

phase 1 assessment summary from taskforce @ lmc 10mar2010 1
Phase 1 assessment: summary fromtaskforce @ LMC-10Mar2010 - 1
  • Advantage of the Phase 1.
    • 1.2 to 1.35 better luminosity with present limitation (collimation and SPS).
    • Better shielding (factor 2.5) and use of all cryo-power installed. When all other bottle necks removed this will allow in principle to pass from 1.7 to 3 1034 in Lumi.
    • Opening to compensate possible shortfall of present LHC (see previous)
    • Separation of cryo-circuit between Arc and IT.

LHC Lumi Up @ 2nd CERN-MAC

phase 1 assessment summary from taskforce @ lmc 10mar2010 2a
Phase 1 assessment: summary fromtaskforce @ LMC-10Mar2010 - 2a
  • Disadvantage of the Phase 1.
    • Optics much more rigid;
      • requires special scheme. Aberration sat the limit of LHC correction capability. Longer magnets (same technology) does not help.
      • 30 cm  is more difficult than 55 cm of the present LHC. Better solution found with  = 40 cm offering a 3 sigma margin per beam (which was part of the initial goal) but only 1.2 gain in lumi over nominal. Today we are limited by a single element. IR upgrade will use all the margins in the whole ring.
    • To change this:
      • modification in MS positions and replacement of a few magnets,
      • additional IR collimators to catch higher losses in IR matching section (lower aperture due to higher beta* in the not-changed magnets
      • Use ultimate strength in the sextupoles, NEW powering scheme of MQT corrector families.
    • Logistics is hard: The logistic for ancillary equipment is hard.
      • A solution NOT fully satisfactory has been found for IP1; more difficult for IP5.
      • A real long term solution devised (see S. Weisz in Chamonix and SC links by A. Ballarino). This solution should be integrated in a more global study for radiation protection of electronics

LHC Lumi Up @ 2nd CERN-MAC

phase 1 assessment summary from taskforce @ lmc 10mar2010 2b
Phase 1 assessment: summary fromtaskforce @ LMC-10Mar2010 - 2b
  • Disadvantage of the Phase 1
    • The use of the same refrigerator for RF and Arc-IT in 4-5 makes 5L (CMS) weaker in term of cryo-power for high luminosity.
    • The new schedule of LHC: we will not be at nominal before 2014-15 at the very best, and the 300-400 fb-1 are foreseen well beyond 2020.
    • Because of past and future delay (splice consolidation) the IT phase 1 cannot be installed anyway before 2016/17.
    • 1 year optimistic installation time + needed time for a new commissioning of the machine
    • The fairly long stop, and the relatively low gain factor: 2 at max, 1.2 at min) require 2.5 to 5 years just to catch up. Then other long stops will be required for L > 2-3 1034.

LHC Lumi Up @ 2nd CERN-MAC

phase 1 assessment summary from taskforce @ lmc 10mar2010 3
Phase 1 assessment: summary fromtaskforce @ LMC-10Mar2010 – 3
  • Recommendation about Phase 1
    • Stop the phase 1 project
    • Keep going on the R&D of Phase 1 that is necessary because of long lead time development;
    • Decision in 2013/2014, after LHC behaviour near nominal will be known, the best technology for upgrade. We can’t start construction before half 2013. Decision in 2014 to have it by 2018-2020.
    • Put the IT upgrade in a global pictures, preceded by all consolidation or improvement needed to make it most effective and compatible with other equipment.

LHC Lumi Up @ 2nd CERN-MAC

what needs to be done for 5 6x10 34 ultimate intensity 0 86 a is assumed
What needs to be done for 5-6x1034ultimate intensity - 0.86 A - is assumed
  • Improve some correctors
    • Commissioning @ 600-650 A the lattice sextupoles
    • New MQT corrector scheme using existing spare 600 A bus bars
  • Re-commissioning DS quads at higher gradient
  • Review MSs
    • Change of New Q5/Q4 (larger aperture), with new stronger corrector orbit, displacements of few magnets
    • Larger aperture D2
  • (may be other actions, more quads in points 6 and 7)
  • Displacement of Power Converters & DFBs at least of Inner Triplets but also of OTHER equipment on surface by means of SC links.
  • Cryo-plant for RF in point 4 : 5-7 kW @ 4.5 K

LHC Lumi Up @ 2nd CERN-MAC

the main ingredient of the upgrade in addition to beam intensity
The main ingredient of the upgrade(in addition to beam intensity)
  • High Gradient Quads, with Bpeak 13-15 T. Higher field quadrupoles translate in higher gradient/shorter length or larger aperture/same length or a mix . US-LARP engaged to produce proof by 2013. Construction is 1 year more than Nb-Ti : by 2018 is a prudent assumption.  as small as 22 cm are possible with a factor 2.5in luminosity by itself, if coupled with a mechanism to compensate the geometrical reduction. If a new way of correcting chromatic aberration could be found,  as small as 10-12 cm can be eventually envisaged.
  • Crab Cavities: this is the best candidate for exploiting small  (for  around nominal only +15%). However it should be underlined that today Crab Cavities are not validated for LHC , not even conceptually: the issue of machine protection should be addressed with priority.
      • Global Scheme. 1 cavity in IP4, Proof on LHC, good for 1 X-ing.
      • Semi-global; it may work!(JP Koutchouck)
      • Local scheme; 1 cavity per IP side. Maybe local doglegs needed.
    • Early Separation Scheme could be an alternative (or a complement)
  • New Cryoplantsin IP1 & IP5: for power AND to make independent Arc- IR:2.8 kW @ 1.8 K scales as 5.2 kW @ 2 K (for 1 set of cold compressor)

LHC Lumi Up @ 2nd CERN-MAC

hf nb 3 sn quad

200 T/m

Note: LQS01 & TQS02

use same strand design

(RRP 54/61)

4.5 K

~3 K

1.9 K

HF Nb3Sn Quad
  • Nb3Sn is becoming a reality (first LQ long -3.6 m – quad 90 mm)
  • This year we expect a second LQ and a 1 m long - 120 mm aperture model
  • In 3 years: 4-6 m long magnet, 120 mm ap., G=180-200 T/m

LHC Lumi Up @ 2nd CERN-MAC

crab cavities
Crab Cavities

qc

Elliptical 800 MHz not far from being designed. Require 400 mm beam-beam

400 MHz small cavity under conceptual study, they can (?) fit in 194 mm beam-beam. Required for final solution

Ref. : F. Zimmermann, Ed Ciapala

LHC Lumi Up @ 2nd CERN-MAC

early separation scheme possible alternative complement
Early separation schemepossible alternative/complement

Nb3Sn at 8.5 T to have margin for heat deposition

13 m from IP

Integration difficult but not impossible

Leveling very easy…

Ref. :

JP Koutchouk and G. Sterbini

LHC Lumi Up @ 2nd CERN-MAC

lumi plane 1 st the near term actions in addition to collimation or inj up
LumiPlane 1st : the near term actions(in addition to collimation or Inj. Up)
  • Studies and R&D to prepare the upgrades
    • Pursuing of the needed R&D initiated in Phase 1. Finished in 2 years at maximum.
      • 2 m long models of the Nb-Ti quads MQXC (2 y)
      • 1 prototype of nested corrector (rad-hard resin) (2y)
      • Complete study short cable MgB2 for Cold Powering (< 1 y)
    • Matching sections and correctors improvements.
    • Pursuing a vigorous R&D on High Field/Gradient magnets
    • Launch Crab Cavity R&D, with test at SPS and finalized to insert a 800 MHz cavity in IP4 as validation test on the 2014/15 horizon.
  • Cryoplants : first Point 4 for RF (on 2014/15 horizon) and then for the High luminosity triplets.
  • New SC links for removal of Power Converter from tunnel (surface, possibly). Decision on 2011 based on 200 m cable tested partly in vertical; installation on the 2014/16 horizon.

LHC Lumi Up @ 2nd CERN-MAC

lumi plane 2 nd constructive projects for 2018 is 2020 more realistic
Lumi Plane 2nd : constructive projects For 2018: is 2020 more realistic ?
  • New Triplet and IR region. In 2013/14 decision on technology and of lay-out with all possible equipments. In the plan we assume that a strong US-LARP continue (and even reinforced).
    • Either Nb3Sn if available before 2018 (not later than 2020). New cryo-plant s at 2K or even at 4.5 K.
    • OrNb-Ti as fall-back solution (cryo-plant at 1.8 K)
  • Crab Cavity (yes or notin 2014, too) ready on the same time scale of 2018. However, they could be installed later if infrastructure is prepared with the triplets.
    • Early Separation scheme (today in shadow of crab, but…)
  • New DS dipole ( twin, 11 T – 11 m) to make room for the cryo-collimators. Available from 2015 (for points 2,7, 1, 5: we assume that for point 3 we are late and we need to displacemagnets).
  • New cryo-plants for IP1 – IP5, decision among: 1.8 K, 2.0 K, 4.5 K see above.

LHC Lumi Up @ 2nd CERN-MAC

11 t 11 m twin dipole for ds
11 T – 11 m Twin Dipole for DS

Shift in the magnet position requires to make room for collimators (red squares).

Alternative option based on stronger and shorter magnets (blue rectangles).

LHC Lumi Up @ 2nd CERN-MAC

comments
Comments
  • Solid plane aimed to  5 1034Lpeak AND yearLdt  150 fb-1 from 2020. Studies under way to devise scenario with higher lumi.
  • Accounting with no overheads-contingency.
  • US contribution to NIT phase 1 for D1 (5 cold masses) and cold Powering is 30 M$ in US accounting including overheads and contingency.
    • D1 : 30 FTE + 5 M$ approx. in CERN accounting, might be maintained (to be confirmed by June). This figure has been added to cost of the New inner triplet to have the total cost.
    • Cold Power : 20 FTE + 3 M$ approx. in CERN accounting. This is not worth to continue because will depend strongly on the actual scenario and lay-out of the upgrade (decision in 2014).
  • US and J are certainly a big part in a possible contribution for the IR: one can base, for a High Gradient Inner triplet, that they can deliver as in-kind, the magnets (more than half of the hardware cost) or part of it.
  • For the Nb3Sn Triplets the resources indicates the total needed. A program is already going on, so the additional money in 2010-13 is only a fraction of what is reported. CEA/CNRS is already committed for 4.5 MCHF + 2.8 FTE and its contribution might be increased of further 2-4 MCHF + 10-15 FTE, using the phase 1 resources.
  • US and J can (should!) contribute to Crab cavities. Discussions just started (see today LARP meeting, where a possible Doe program is being discussed).
  • Japan can also contribute to in-kind-contribution for Cryogenic upgrade.

LHC Lumi Up @ 2nd CERN-MAC

appendix preliminary shopping list
Appendix: (preliminary) shopping-list
  • The chromatic limit gives the dimension of the LHC Upgrade (b*, IT aperture, aperture of the matching section quad):

a) At least 650A needed in the defocusing lattice sextupoles (for b*=20 cm).

 Sextupole limits to be clearly identified and 32 PC’s (600A) to be upgraded (changed).

b) The correction of the off-momentum b-beating (and Q’’) requires prescribed

betatron phase advances from mid-arc to mid-arc and on the left/right side of the low-b insertions.

 Additional IR tunability needed and effectively obtained by re-cabling the arc tune shift quads (2 families instead of 1 per beam per plane and per sector).

  • The Matching Section (MS) aperture limitations pushed to the edge the quadrupole gradients of the low-b insertions (either to low field or max. field):

Q5/Q6 0 T/m, Q7  200 T/m, some standalone MQT’s (@Q12 & Q13)  120 T/m

a) Remove aperture bottle-neck in the MS (& TAN)

 Q5 assembly:MQY (70 mm) instead of MQM (56 mm) and MCBY type orbit corrector

 Q4 assembly:New 2-1 quadrupole type for Q4 (presently MQY) with ~ 85 mm coil aperture and new type (stronger) orbit correctors (presently MCBY).

 D2: New D2 (presently 80 mm coil ID but “only” 69 mm cold bore ID) with ~ 85 mm coil aperture 2-1 dipoles.

 New TAN (aperture to be defined depending on the D1-D2 distance).

b) Readjust the MS layout (new azimuthal position for Q4 and Q5, Q6 a priori OK) to the length of the new IT to avoid pathological behavior (low gradient) at low b*.

 Typically moving Q4/Q5 towards the arcs by 15 m/10 m if the new IT is ~15 m longer.

c) Re-commission the Dispersion Suppressor quadrupoles of IR1 and IR5 at higher current, in particular Q7

 6KA (220 T/m @ 7TeV) as already done in SM18 but not in the tunnel (or new stronger Q7 if the above measurements are found to be insufficient.)

Courtesy of S. Fartouk

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