1. MEB 2004: the lessons learned presented by L. Bottura for the Magnet Evaluation Board Workshop CERNmonix XIV Thursday, January 20 th, 2005

2. Outline What is MEB ? Mandate, membership and mission The case of MB installation situation as of January 2004 and consequences of a blind installation scheme magnet classes, an installation algorithm and its implementation the final touches ? The other magnets SSS IR magnets all the rest Summary

3. The Magnet Evaluation Board is charged with: Assessment of the suitability of each magnet produced for the LHC accelerator, based mainly on the information from its Manufacturing and Test Folder Optimization of installation and tunnel location of the magnets in the LHC accelerator based on the magnet performance (principally powering, geometry and field quality issues) Requesting competent bodies (Groups and/or Working Groups), to study and produce recommendations on specific issues related to installation strategy The MEB has executive power within the scope of its mandate, and: reports directly to the LHC Project Leader informs the MARIC, and LTC Kick-off on May, 3rd, 2002 (P. Lebrun) Trail-blazing work from N. Siegel (chair), S. Fartoukh, D. Tommasini Now consists of 15 members from AT, AB and TS, L.Bottura (chair), M. Giovannozzi (scientific secretary), E. Delucinge (secretary)

4. 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 question, delays in the installation (see: the January theorem) have provided a comfortable stock of magnets (e.g. in excess of 400 MB’s) Mission: Find suitable slots for the available magnets that perform better as 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

5. The January theorem Statement:whatever the January of year YY, the first magnet should be installed in March YY Proof (by mathematical induction of first-kind): I.BASE clause (P(n 0 )): in January of year n 0 (with n 0 = 2004) the first magnet to be installed was planned for March of year n 0 II.RECURSION clause (P(n))  (P(n+1)): in January of year n+1 (with n = 2004, n+1 = 2005) the first magnet to be installed is planned for March of year n+1 QED Other theorems of the same class: 50 years to fusion: whatever the year Y, thermonuclear fusion power will be available in 50 years from Y

6. MB situation as of January 2004 all MB cold masses of 1 octant (type R) were delivered approximately only 1/2 octant cold tested (missing cold data) few slots pre-allocated under the pressure of launching tunnel preparation work in SMI-2 various performance concerns: dipoles geometry out of tolerance (10 to 20 % of production) cold mass shape and position unstable (shape changes by more than 1 mm measured in the body) coil cross section changes from the initial production (XS1, non-nominal shims) to the first iteration (XS2) to the present state (XS3) modified systematic multipoles electrical insulation, quench level, instrumentation (approximately 10 % of production needs re-test and/or re-work) other minor hardware faults (faulty T-sensors on 5 % of production) XS1  XS2XS2  XS3  b1 -10-5  b3 -2…-3

7. Geometry issues out-of-tolerance geometry after cold test, entailing a loss of mechanical aperture of about 1 mm in addition, an unstable geometry, to 1 mm level, would make re-alignment a risky guess-work, increasing uncertainties at operation spool piece positioning off MB axis causes feed- down during corrections b3 corrections with the spool piece off-center horizontally induces a tune change courtesy of E. Wildner Shape change ITP20 to WP08 ends at WP08 sagitta at WP08

8. Field quality issues  b 3 of ≈ 2 units @ 17 mm, as observed for sector 78, could have resulted in a loss of DA of ≈ 1  compensating large (up) and small (down) b 3 (tic-tac and flip-flop schemes) or  -pairing them (same b 3 in dipoles spaced by 2 arc cells) restores the DA close to the nominal 12  value from S. Fartoukh, EPAC 2004

9. MB variants and constraints hardware variants (LBARA.34R7) 4 dipole types (A/B spool piece, R/L diode) from industry MEB approval 17 types of interconnects, work performed at CERN, resulting in 12 combinations of type+interconnect for the arc, and 20 combinations for the DS 32 variants we need to consider (in addition) specific magnet features and non-conformities closed by project engineers with the statements “use as is” or “dealt at MEB” e.g. temperature sensor out of work, pipe positions out of specification

10. Geometry classes 4 classes, based on the variation of the beam size along the cell: mid-cell (maximum space where the beam size is minimum) silver (nominal tolerance revised for race-track) silver-right (MQ on the r.h.s., mid-cell on the l.h.s.) silver-left (MQ on the l.h.s., mid-cell on the r.h.s.) golden (reduced tolerance for DS cells) MQMB S to SL MCS to SR MQMB error silver mid-cell Last industry measurement Last WP08 measurement based on proposal from S. Fartoukh specifications after J.B. Jeanneret and the WGA

11. Field quality classes 4 classes, based on measured field quality vs. specifications: Green (use anywhere, direct and blind installation) e.g. |b1| ≤ 9.8, |a1| ≤ 9.8, |a2| ≤ 0.9, |b3| ≤ 3 at FT Yellow 0-1  (good candidates for direct installation provided the actual running average is checked within bounds) e.g. 9.8 < |b1| ≤ 14.5, 9.8 < |a1| ≤ 14.5, 0.9 < |a2| ≤ 1.9, 3 < |b3| ≤ 4.8 at FT Red 1-3  (require that the running average is within bounds and/or compensation by sorting) e.g. 14.5 < |b1| ≤ 30.5, 14.5 < |a1| ≤ 30.5, 1.9 < |a2| ≤ 5.7, 4.8 < |b3| ≤ 8.4 at FT Blue (marginalization and sorting in any case before a slot is assigned) e.g. 30.5 < |b1|, 30.5 < |a1|, 5.7 < |a2|, 8.4 < |b3| at FT following the definition of S. Fartoukh

12. Quench classes 3 and 1/2 classes, based on training and electrical characteristics: Golden (bonus magnets, do not detrain ? preferably use in hot regions) N ramp (9 T)  3 and[electrically sound] Silver-plus (nearly as good as golden magnets ? preferably use in hot regions) N ramp (9 T) > 3 and N ramp (8.75 T)  2and[electrically sound] Silver (normal magnets) N ramp (9 T)  9 and N ramp (8.4 T)  2 during first test or N ramp (9 T)  9 and N ramp (8.4 T)  1 after thermal cycleand[electrically sound] or N ramp (9 T)  9 and N ramp (8.6 T)  2 after thermal cycle Reserve (bound to train/detrain, preferably use in shielded regions) training as defined for G, S+, S, but shows detraining, or high splice resistance or deviation from nominal cable margin at 4.5 K NOTE: this is a working hypothesis, as at present: the relation between test training and detraining is not formally established hot locations are identified based on general reasoning on aperture following the definition of A. Siemko, P. Pugnat and E. Floch

13. Installation algorithm - 1/2 Logic: form pairs of magnets that compensate deviations of field errors from average in the sector (compensated by the correctors) to minimise the effect of the rms exception rules (by priority): satisfy hardware type constraints (diode, spool) no more than 1 magnet with defective T-sensor per cell, in locations that can be accepted by cryo-control power-R magnets in mid-cell locations geo-MC, geo-SL, geo-SR magnets (with out-of-tolerance geometry) in suitable locations in arc cells (mid-cell, right or left of a MQ) geo-G magnets in DS cells power-G and power-S+ magnets in priority to DS (power-S otherwise) not more than 3 magnets in a cell with out-of-tolerance b1 and/or a1 courtesy of S. Fartoukh, presented and discussed at FQWG and MEB References:Proc. of LHC Workshop Chamonix-XIII, pp.148-158, 2004 Proc. of EPAC 2004, pp 176-179, 2004

14. Tools MTF hardware description, equipment data, non- conformity reports, ID card (TS/CSE) data base links and viewers geometry viewer (AT/MAS) magnetic viewer (AT/MTM) status pages cryodipole coordination page (Dipcoor) installation sequence (MTF and TS/IC) MEB hardware report as a compact summary of properties for a magnet sequence (MTF)

15. Sector 78 as of December 2004 5 more dipoles

16. Lessons from 78 A set of working and adapted tools required about 1 year to be defined, implemented and trimmed, learning what is important on the way. This investment pays off today, and the same system will be used for the arc SSS’s. This time was also needed to speak the same language in the magnet evaluation. In spite of a very heterogeneous and difficult mix of properties and performances in the initial production aperture is expected to be maintained vs. possible 1.4 mm loss (because of the  1 mm out-of-tolerance on the geometry and the  1 mm instability) in the ideal case of perfect IR, DS and MS, the DA is expected to be at 11 to 11.5  (close to target) vs. possible 1  loss (caused by large spread of geometric b 3 ) random b2 in SSS partially compensated to maintain the  -beat budget within spec (7 to 8 %), see later on SSS Completing a sector after an allocation in batches (typically 10) is increasingly difficult (drop-outs, leftovers, availability issues). A different working mode will be adopted for the coming sectors

17. The 2 coming years for MB’s Allocation on following sectors will take place in batches of 154 magnets (and about 20 spares to cover drop-outs and problem cases). The batch is pre-selected from the stock of  350 CM’s available at CERN For sector 81 (see LHC PN 358) we take the magnets with highest b3 (limiting factor), inner cable type 01B, with enough (  35) golden geometry magnets. The b3 spread is decreased from 1.5 to about 1 units @ 17 mm pairing continues to build margin, should it be needed at a later stage All information relevant for slot allocation is collected in a summary table that is obtained as on-line report in MTF We now check the flexibility of this approach vs. the practical demands of installation, and adapt as necessary. sector 81 descends in March 2005 - prepare work in SMI-2 starting from end of January 30 magnets (slots) by end of January 40 magnets/month on average thereafter allocate following sectors, as the installation rate demands (ramp to steady-state by Spring 2005) IDEA: identify joker magnets that can be used in case of problems originating or discovered after SMI-2 preparation work Complementary activity: feed-back loop in SMI-2, adjustments and special tests as demanded, definition of the installation WP and installation shifts

18. MB approval rate 1000 magnets in 18 months: ≈ 50 magnets/month

19. The arc SSS’s The many hardware variants (60 arc SSS types, depending on magnetic, electric and cryogenic function) are finalized in industry at the moment of assembly in a cold mass. A sorting, as done for MB’s, is not possible The main issue is the random b2. Limited b2 pairing of SSS’s (using slot equivalence for some 1/2 of the SSS types) is possible, and has been done in sector 78 (A. Lombardi)  b2  15 units vs. 10 units specified reduced to an effective  b2 effective  5 … 10 units through pairing, bringing the expected  -beat from SSS random b2 within budget As from end of January we proceed to sector 81 with high priority Approval tools and specifications not yet final ! finalize race-trackization of the geometric tolerances (WGA) automatic ID cards production from data-bases confirm 10 slots/month (provisional) as of January complementary activity: verify shapes as measured in 908, define optimal installation shifts

20. Cryomagnets for IR (US-LHC) MEB examines magnets prior to shipment, try to identify any no-go issue before the magnets are at CERN magnets are already approved by acceptance boards at US-Labs and US-LHC project management discussion on suitability for ring installation and operation (FQWG, WGA, EEWG may be asked to give recommendation) data transfer to CERN databases is a mandatory step before approval for shipment ID card provided by US-LHC, pre- filled with acceptance data summary Status: four D1’s (BNL) and six D2’s (BNL) are approved (all D2 allocated) (M. Giovannozzi) approval of 3 D2’s: March 2005 approval of D3’s and D4’s: June 2005 discussion on triplet (Q1, Q2 and Q3 (FNAL)) after shipment to approve installation based on the final geometry (re- measured at CERN): start March 2005 The MTF work is reduced to the minimum necessary for installation and operation no detailed breakdown of production data from J or US The IR magnets work is presently not on a critical path few magnets can be treated as the need arises

21. MS’s and DS’s quadrupoles The plan is to install the first IR, MS and DS at point 8 between July and August 2005 Today, 3 magnets have been cold tested in SM-18, one measured magnetically in 2004, production and testing will ramp-up in 2005 These magnets are complex assemblies, very small series The tools developed for MB and SSS require adjustment to produce efficiently the respective ID cards (work for 2005) sorting of completed Q4…Q7 is not possible because the number of units/variant is small some limited sorting can be done on Q4…Q7 before completion of the cold mass, based on warm data (and cold data from B4) for completed Q8, Q9 and Q10 some sorting is feasible We need to define a rationale for slot allocation and adopt a working mode adapted to the demand, anticipate the discussion geometry performance (including correctors) field quality (other constraints)

22. Warm magnets Total of 154 magnets, do not forget them ! The issues for warm magnets are clearly different from superconducting magnets (where we allocated most of our efforts so far) pole geometry alignment field strength, direction and field homogeneity Critical elements: MBXW for installation, MQW for sorting in Q4/Q5 assemblies sorting of magnets/vacuum pipes to maximise aperture Work required define alignment (mechanical, references) (WGA) present results on a magnet-by-magnet basis (geometry, magnetic) define and approve slots

23. Summary The MB activity for sector 78 has shown that it is possible to preserve projected performance (mechanical and dynamic aperture), and optimize the machine (build margin now for later needs) This requires commitment and continuous interaction between the members (and their teams) involved in magnet manufacturing, testing, installation and beam physics The MEB has acted in this direction, working as a decision body for slot allocation, as well as a bridge between hardware characteristics and beam requests The activities in 2005 will focus on mass allocation (MB’s and SSS’s) define and implement a suitable working mode for magnets in small series (MS and DS quads, warm magnets)

24. Acknowledgements MembersAlternate Members Luca Bottura (Chairman) Massimo Giovannozzi (Secretary, ABP-IR, MS and DS SS) Stephane Fartoukh (ABP-MB)Oliver Bruening Alessandra Lombardi (ABP-SSS) Karl-Hubert Mess (Electrical Engineering)Ranko Ostojic Ranko Ostojic (IR, SSSS)Karl-Hubert Mess Dominique Missiaen (Survey) Suitbert Ramberger (Resistive Magnets)Willi Kalbreier Michele Modena (SSS)Vittorio Parma Stephane Sanfilippo (Field) Elena Wildner (Geometry)Walter Scandale Jean Bernard Jeanneret (Aperture) Frank Schmidt (ABP-IR)Oliver Bruening Andrzej Siemko (Quench and Protection)Pierre Pugnat Davide Tommasini (MB)Theodor Tortschanoff