Journal Club presentation LHC optics commissioning: A journey - - PowerPoint PPT Presentation

Journal Club presentation

LHC optics commissioning: A journey towards 1% optics control Helena Pikhartova June 27, 2018

Summary of article

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Beta beating

✽ Maximum relative deviation of the β function with respect to the model ✽ Traditionally not required to be very precise ✽ LHC is the first high energy collider with tight design tolerances on

• ptics errors to guarantee the machine protection during operation

with beam Beta beating for some other machines:

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β∗ waist

✽ In 2015 it was discovered that there was a systematic offset of the β∗ waists in both IP1 and IP5 resulting in an increase of the β∗ causing about 5% luminosity loss

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Orbit drift

✽ Without varying any parameters, orbit will change through hours of

• peration

✽ Need to have feedback on orbit drift and correct

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Beam Position Monitors

✽ BPMs are used to measure the turn-by-turn data of betatron

• scillations, which are excited adiabatically by an AC dipole

✽ 11 BPMs installed to measure phase advance between each other and calculate β at their location ✽

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K-modulation

✽ K-modulation is a method for measuring beta functions at locations

• f individually powered quadrupoles

✽ Changing the strength of a quadruple results in a tune change → tune change is proportional to the change of strength and the beta function at the location of the quadrupole ✽ If the tune change can be measured accurately, the beta function can be calculated from the change in quadrupole strength

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Conclusion

By the end of 2016: ✽ β∗ = 0.4 m (better than design value) at 6.5 TeV ✽ Smallest beta beating ✽ Optics control 1% ✽ Luminosity leveling due to detector pileup and cryogenic power limits done by varying β∗ during run 2017 and beyond: ✽ β∗ = 0.3 m at 7 TeV ✽ Keeping up good optics control

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The end of presentation

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Discussion

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