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What we may gain with the sorting at MEB

What we may gain with the sorting at MEB. Presented by L. Bottura for the MEB Session 4 - Magnetic Requirements for Commissioning Divonnix, January 2006. Outline. Our mission statement Sorting in practice: the MB’s Macro-sorting Skimming/sifting the FQ Geometry classes Examples SSS’s

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What we may gain with the sorting at MEB

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  1. What we may gain with the sorting at MEB Presented by L. Bottura for the MEB Session 4 - Magnetic Requirements for Commissioning Divonnix, January 2006

  2. Outline • Our mission statement • Sorting in practice: the MB’s • Macro-sorting • Skimming/sifting the FQ • Geometry classes • Examples • SSS’s • Examples • The other magnets (DS/MS/IR) • Examples • Issues • Conclusions and perspective

  3. Mission statement • If all magnets performed to (beam) specifications, we could install any magnet anywhere • In reality, we are faced with magnets performing worse, as, or better than (production) specified, available as produced and requested as from installation schedule • Although a global sorting is out of the question, delays in the installation have provided an appropriate stock of magnets (e.g. in excess of 400 MB’s) • Mission: • Find suitable slots for the available magnets that perform better than specified, as specified or out-of-tolerance • Preserve and (if possible) optimize the machine performance • Include provisions to face day-to-day requirements (faults during processing the magnets) • Follow the planned installation schedule with a suitable flow of allocated magnets

  4. 580 MB’s have been assigned to a slot in the tunnel (nearly 1/2 of the LHC) A stock of ≈ 250 magnets is available for macro- and local-sorting Working mode was drastically modified at the end of 2004 to semi-automatic assignment by batches (see later) to match the demands of transport and installation teams Slot allocation for MB’s Semi-automatic assignment started as proposed by S. Fartoukh

  5. Based on proposals from S. Fartoukh and E. Todesco Macro-sorting for MB’s • Pre-select batches of 1 sector (154 MB’s + some 10…20 spares) among the available stock(1) that have: • The appropriate diode type (R/L) • A 50/50 split between corrector packages (A/B) • The same inner cable (01B and 01E show slight differences in b1 at injection and initial ramp) • Minimum b1 and b3 random (see next slides) • An appropriate split among golden/silver/mid-cell geometry (see next slides) • Random mixing of • Manufacturer (Alstom/Ansaldo/BNN) • Outer cable type (02B/02C/02D/02E/02G/02K) NOTE: (1) CM and CR magnets. Magnets with delivery/completion date within few weeks of allocation are also considered for pre-selection

  6. Courtesy of E. Todesco Skimming/sifting the FQ - 1/2 • Production b3 1.9 units (vs. 1.4 units target) Initial production with non-nominal shims Change of cross section Negative trend of b3 for Ansaldo magnets and Alstom magnets with non-nominal shims Xs1 Xs2 Xs3

  7. Skimming/sifting the FQ - 2/2 • Optimized choice can be used to select batches with b3 1.0 … 1.6 units Initial production with non-nominal shims and change of cross section Inner cable 01E Mixing of cross-section 2 and 3

  8. In one sector: not more than 46 (23+23) MC at least 10 (5+5) G Preferable (to allow sorting): At least 20 (10+10) G Not more than 20 (10+10) MC Based on a proposal from S. Fartoukh and J.B. Jeanneret Geometry classes - 1/3 mid-cell mid-cell Beam size silver silver silver silver

  9. Geometry classes - 2/3 • Morenon-silver magnets than allowed • A bit less golden magnets than desired Distribution of classes in allocated sectors Geometry of as-built MB’s

  10. Classes devised and defined by S. Fartoukh, J.B. Jeanneret and the WGA Geometry classes - 3/3 Golden-right Silver-left We can take advantage of the change of beam waist in the cell ! Silver-right Golden-left OK !

  11. The case of MB1148: Assigned to DS slot (geometry-critical) LBBLQ.8L1 based on anticipated geometry Unique type of interconnect (slot swapping not feasible) Central foot blocked at cryostating (WP02), producing mid-cell geometry Flanges out of tolerance (interconnect issue) Foot at the limit of the adjustment range Solution: installation shift x = 0.7 mm Courtesy of J.B. Jeanneret Example: MB geometry r-parameter of MB1148 as built V1 V2 r-parameter of MB1148 with installation shift V1 V2

  12. Algorithm devised by S. Fartoukh, discussed at FQWG Magnetic sorting • Local sorting on TF, b3, a2 to: • Insure that the CO can be corrected with < 30 % of the corrector strength • Minimize the driving terms of 3rd order resonance • Control the driving terms of of coupling resonance and vertical dispersion • Method: • No more than 3 MB’s with |b1| > 10 units in a raw • Form self-compensating sequences of MB’s to absorb |b1| > 15 units • Flip-flop pairing magnets with b3 above/below the <b3> • Pairing at  magnets with large or small b3 • Flip-flop pairing at 2 magnets with a2 above/below the <a2> • Pairing at /2 magnets with a2 above/below the <a2>

  13. Courtesy of S. Fartoukh Example: b1 local-sorting b1 distribution in sector 7-8 V1, MCBH strength at 7 TeV and residual CO error Gain: MCBH budget necessary for b1 correction limited to +/- 15 % of the available strength XS2 and XS3 magnets XS1 BNN magnets

  14. Effect of flip-flop pairing Effect of -pairing Courtesy of S. Fartoukh Example: b3 local-sorting b3 distribution in sector 7-8 3rd order resonance driving terms -paired flip-flop paired Gain: effective random b3 and driving terms reduced by a factor 3 XS3 magnets XS1 BNN magnets

  15. SSS come in many different types, with reduced sorting possibility Batch selection and qualification is performed in advance to cold test Pairing at /2 magnets with b2 above/below the <b2> (or pairing at 3/2, or flip-flop at , 2, issue with D-beating) 110/362 SSS (nearly 1/3 of the main ring) allocated to date Courtesy of M. Modena SSS allocation

  16. g r Specifications devised and defined by J.B. Jeanneret and WGA SSS geometry • The available aperture is tighter in the MQ’s, with no difference among cells • Specification based on D(H) quadrupole SSS58 • The present situation requires care (see next slide) to avoid aperture loss at the level of 0.5 to 1 mm SSS58

  17. The case of SSS95: Assigned to slot Q25R8 BPM support out-of-tolerance by 0.25 mm (cannot be corrected) Field angle 1.6 mrad (i.e. a2 = 32 units) Solution Installation shift and roll z=-0.1 mm, =-0.9 mrad Negligible aperture loss (of the order of 50 m, not critical because the quadrupole is F) Courtesy of E. Wildner, Y. Papaphilippou Example: SSS geometry r-parameter of SSS95 as built V1 V2 r-parameter of SSS95 with installation shift and roll V1 V2

  18. Courtesy of Y. Papaphilippou Example: SSS b2 sorting Total -beating (2 planes, 2 apertures) b2 distribution in sector 7-8 as from warm measurements Collars with permeability out of specification have large apparent deviation from the production average Gain: total beta-beating kept well within (factor 2 to 3) the allocated budget

  19. About 200 magnets: DS/MS (Q4…Q11) and IR (Q1…Q3, D1…D4) Correction dipoles for IP8,IP2 Discussed one-by-one, based on the specific requirements of the proposed slot (e.g. SSS607 in Q5L8) Allocated 6/114 DS/MS quadrupoles (< 10 %) 4/4 cold D1 6/8 D2 (the remaining 2 are preallocated) 5/24 IR quadrupoles (Q1/Q2 of IR8 R+L and Q3 or IR8 L) 3/6 warm compensation dipoles (IP8 spectrometer) In addition MQW pre-sorted based on b2 and geometry Maximum operating Current: 3453 A SSS607 training curve The other magnets

  20. The case of D1 at right of IP8 (D1L105) Pre-assignment based on field quality and geometry inferred from measurements taken on the cold mass skin Large deviations from straightness found in the cold bore x=1.7 mm, z=2.7 mm Critical n1 = 5.7  at collision vs. 7  target (with *=1 m) Solution: Installation shift x=-0.6 mm Marginal n1 = 6.3  at collision (with*=1 m, but this is an extreme case not used) Courtesy of M. Giovannozzi Example: D1 geometry D1L105 horizontal geometry D1L105 vertical geometry

  21. Replacement of magnets at installation Risk: we may lose the advantages of sorting MB batch selection, cold test planning and fiducialisation Risk: reduced flexibility as the production ends and the “sorting buffer” is depleted SSS installation vs. production Work: meeting the installation needs requires swift action (days) Quads in the DS and MS Work: documentation, automation, organization, as for MB’s and SSS’s IR magnets, most critical elements in the machine at collision Work: qualify cold D3/D4, Q1/Q2/Q3 Warm magnets Work: document, qualify, sort and assign to slot Assist the coordination work through anticipation Cold test planning Pre-assignment of MQ’s in the SSS Quench level in MQTL correctors Issues

  22. Results and perspective - 1/2 • So far we met our goals, and, when possible, we did better… • Maintaining the magnetic properties under control (using sorting and compensation on field quality) • Preserving the mechanical aperture (using sorting on geometric classes and installation shifts/rolls) • Negligible aperture loss in MQ’s, 0.1 mm (D) to 0.2 mm (F) • MB’s in the shadow of MQ’s • Optimizing the installation sequence to gain margin (limiting the corrector strength, resonance driving terms)

  23. Results and perspective - 2/2 • … but we are only half way (at most) • IR, MS and DS are in front of us (and there is work to be done to specify aperture targets and qualify magnets) • Changes of transport/installation scenarios and needs result in pressure on magnet delivery, we are in the middle of this process. The situation will escalate during 2006

  24. Acknowledgements ABP coordinators experts

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