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FIELD QUALITY IN D2

CERN, 11 th June 2013 HiLumi , WP2 meeting. FIELD QUALITY IN D2. E. Todesco CERN, Geneva, Switzerland This estimate relies on the work presented by R. Gupta in Napa valley HiLumi meeting https:// indico.fnal.gov/conferenceDisplay.py?confId=6164. DESIGN OPTIONS.

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FIELD QUALITY IN D2

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  1. CERN, 11th June 2013 HiLumi, WP2 meeting FIELD QUALITY IN D2 E. Todesco CERN, Geneva, Switzerland This estimate relies on the workpresented by R. Gupta in Napa valleyHiLumi meeting https://indico.fnal.gov/conferenceDisplay.py?confId=6164

  2. DESIGN OPTIONS • Coilwidth: either 10 mm RHIC likecoil, or 15 mm LHC likecoil • One layer sinceweneedspace • Margin on loadline 20% minumum • So one has two options • LHC cable, 20% margin, 5 T operationalfield (7-m-long) • Smallercable or largermargin, 3.5 T operationalfield • as today, 10-m-long • Largerfield, worsefieldquality • Worse, but perhaps acceptable • First question: do weneed the additional 3 m ?

  3. DESIGN CHALLENGES • Large aperture, fixed distance betweenbeams, large cross-talk • Signs of evenmultipoles • B2 have opposite signs in the ap • B1 have the samesign • b2 have opposite sign

  4. ALLOWED MULTIPOLES • General framework : optimizationathighfield • Allowedmultipoles: strong saturation effect, to becompensatedwithgeometric • 140 units of b3, 20 units of b5 (5 T), reduced by a factor 2.5 at 3.5 T • I assume that the correction canbedonewith 20% error, soresidual 30 units and 4 units, probablyverypessimist

  5. ALLOWED MULTIPOLES • Random part • Allowedmultipoles: strong saturation effect, to becompensatedwithgeometric • 140 units of b3, 20 units of b5 (5 T), reduced by a factor 2.5 at 3.5 T • I assume a spread of 3-5% of the saturation effect, so • 5 units of b3, 1 unit of b5 • So spread of saturation dominates over spread of geometric (new situation) • Magneticshimmingcould help to reduce the spread of one multipole

  6. Quadrupole • General framework : the magnet has a very large quadrupole component due to two-in-one cross-talk • One could cure athighfieldwithasymmetriccoils, but I don’tthinkthisisneeded – reproducibleeffect • So I justgiveyou the numbers … 100 unitsat 5 T, 40 at 3.5 T • Also in this case a factor 2.5 gainedloweringfieldfrom 5 to 3.5 T • Random part – also in this case 5% of saturation, so 5 units

  7. OCtUPOLE • General framework : the magnetalso has a very large octupole component due to two-in-one cross-talk • This isbad and not soeasy to correct • The numbers: 40 unitsat 5 T, 15 at 3.5 T • Also in this case a faactor 2.5 gainedloweringfieldfrom 5 to 3.5 T • Random part – also in this case 5% of saturation, so2 units

  8. FIELD QUALITY GUESS

  9. FIELD QUALITY GUESS

  10. CONCLUSIONS • I provided the worst case of fieldquality • Weneed to know what to optimize • Is b2 a problem ? • Is b4 to bereduced ? – thiscanbedonewithironshaping • Hard to reduceboth b2 and b4 … • If the b3 and b5 are too large, weshould go to longer magnet • Real estimate of the possiblity of controlling saturation and itsspreadis not easy to judge • Goingfrom 5 T to 3.5 T (and from 7 m to 10 m) one gains a factor 2.4 in criticalmultipoles, bothsystematic and random

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