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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


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


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

  • 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