Feb 20 th 2003 Pierre Bauer1 - Tevatron RunII Meeting REPORT ON INVESTIGATION OF POSSIBLE MAGNET RELATED ISSUES IN THE TEVATRON G. Annala, P. Bauer, R. Cargagno, J. DiMarco, N. Gelfand, H. Glass, R. Hanft, D. Harding, R. Kephart, M. Lamm, A. Makulski, M. Martens, T. Peterson, P. Schlabach, D. Still, C. Sylvester, M. Tartaglia, J. Tompkins, G. Velev, M. Xiao Also many thanks to L. Bottura (CERN), H.D. Brueck and B. Holzer (DESY), G.L. Sabbi (LBNL), A. Tollestrup and V. Shiltsev for their ideas, opinions, suggestions and help!

Feb 20 th 2003 Pierre Bauer2 - Tevatron RunII Meeting 1)Tevatron Dipole Magnets – an Overview 2)Measurement of Dynamic Effects in Tevatron Dipoles 3)Discussion of Possible Magnet Issues in the Tevatron INTRODUCTION D. Finley et al. 1987

Feb 20 th 2003 Pierre Bauer3 - Tevatron RunII Meeting I TEVATRON DIPOLE MAGNETS 1)Dipole Models 2)Production Magnetic Measurement Data 3)Field Profiles

Feb 20 th 2003 Pierre Bauer4 - Tevatron RunII Meeting THE TEVATRON DIPOLE MODELS - BODY Bore field at injection (T)0.66 Bore field at collision (T)4.3 Magnetic length (m)6.116 Average x) b 2 * in body (x B 0 )14.4 xx) Sigma x) b 2 * distr.in body (x B 0 )3.1 Pole angle var.for 1  in b 2 * (  )0.15 Azim.coil position var.for 1  (  m)100 Saturation effect (% of b 2 * inj.)+1.9 Stray-field (mT)? * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) x) Data are from production measurements (more details later). xx)Tevatron dipoles have strongly differing b2 in body and ends, that, on average compensate when integrated over the magnet length !

Feb 20 th 2003 Pierre Bauer5 - Tevatron RunII Meeting THE TEVATRON DIPOLE MODELS - END * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) Length of end (arbitrary) (cm)50 Type of end: compact Length of non-yoked end-section (cm)~12 Average dipole field end/body ratio0.86 Length (arbitrary) (cm)50 Average x) b 2 * in end (units of B 0 )-115 Sigma x) b 2 * in end (units of B 0 )? x) Data derived from production measurements (more details later).

Feb 20 th 2003 Pierre Bauer6 - Tevatron RunII Meeting FIELD PROFILE IN END Results of the calculations presented here are not for the “average” end.

Feb 20 th 2003 Pierre Bauer7 - Tevatron RunII Meeting MAGNETIC MEASUREMENT ARCHIVE DATA* * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) J. Tompkins / R. Hanft

Feb 20 th 2003 Pierre Bauer8 - Tevatron RunII Meeting THE TEVATRON DIPOLE NORMAL MULTIPOLES* * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) Calculated from “Up-down-average” of archived production magnetic measurements for approx. all magnets installed. J. Tompkins / R. Hanft Down-stream positionUp-stream positionBody position

Feb 20 th 2003 Pierre Bauer9 - Tevatron RunII Meeting THE TEVATRON DIPOLE SKEW MULTIPOLES* * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) J. Tompkins / R. Hanft Calculated from “Up-down-average” of archived production magnetic measurements for approx. all magnets installed. Down-stream positionUp-stream positionBody position

Feb 20 th 2003 Pierre Bauer10 - Tevatron RunII Meeting AVERAGE FIELD PROFILES IN DIPOLE CALCUL- ATED FROM TABUL- ATED (Geometric) MULTI- POLES J. Tompkins 2002

Feb 20 th 2003 Pierre Bauer11 - Tevatron RunII Meeting II DYNAMIC EFFECTS IN TEVATRON DIPOLES 1)Introduction to Dynamic Effects 2)Historical Review of Tevatron Magnet Measurements 3)Some Recent Results

Feb 20 th 2003 Pierre Bauer12 - Tevatron RunII Meeting DYNAMIC EFFECTS -BASICS P. Schlabach MP drift at constant coil current & SB to the hysteresis loop at the ramp- start. Drift & SB in all ”hysteretic” multipoles -powering history dependent. 1-2u ~15 A / 15 mT/ 7 GeV back porch time current injection porch flat top reset pre-cycle:

Feb 20 th 2003 Pierre Bauer13 - Tevatron RunII Meeting DYNAMIC EFFECTS IN TEVATRON DIPOLES – QUALITATIVE MODEL Current distribution is not uniform in the cables and changes as a function of time, generating a time-variable, -B-B +B+B alternating field along the Strands. L. Bottura/CERN 2002

Feb 20 th 2003 Pierre Bauer14 - Tevatron RunII Meeting DYNAMIC EFFECTS IN TEVATRON DIPOLES – PREVIOUS STUDIES YRMAGNETCOMMENT 87AA1001 (1m)discovery of drift 88/89RL1001 (1m)discovery of snapback 88/89TB447, TB223, TB271, TC1194, TB338, TC537, TC1200 remnant field in full length dipoles, drift found also in other mps 92TB353, TB1220, TB1207, TB492, TB862 first full length magnet measurements 96TC1052, TB504back-porch, flattop energy 02/03TC1220, TB834, TB438, TC269 tune and coupling drift, b2 compensation

Feb 20 th 2003 Pierre Bauer15 - Tevatron RunII Meeting MAGNETIC MEASUREMENTS AT MTF MTF today has 7 test-stands to perform magnetic measurement of Fermilab magnets, superconducting IR quads for LHC, high field (Nb3Sn) magnets.

Feb 20 th 2003 Pierre Bauer16 - Tevatron RunII Meeting 87 - DISCOVERY D. Finley et al. 1987

Feb 20 th 2003 Pierre Bauer17 - Tevatron RunII Meeting 88 - MEASUREMENTS Magnet Meas. – RL 1001 R. Hanft et al. 1988

Feb 20 th 2003 Pierre Bauer18 - Tevatron RunII Meeting 92-MEASUREMENTS D. Herrup et al. 1992

Feb 20 th 2003 Pierre Bauer19 - Tevatron RunII Meeting 96-MEASUREMENTS J. Annala et al. 1996

Feb 20 th 2003 Pierre Bauer20 - Tevatron RunII Meeting MAGNETIC MEASUREMENTS – 02/03 J. Tompkins / G. Velev / R. Hanft

Feb 20 th 2003 Pierre Bauer21 - Tevatron RunII Meeting III Discussion of Possible Magnet Issues in the Tevatron 1)Temperature Variations 2)Tune and Coupling Drift 3)Main Field Drift 4)Analysis of the b2-Compensation in the Tevatron

Feb 20 th 2003 Pierre Bauer22 - Tevatron RunII Meeting QUANTITATIVE ESTIMATE OF DRIFTING SKEW AND NORMAL QUADS b1 drift needed in dipole to explain tune drift: a1 drift needed in dipole to explain coupling drift:  b1/  a1 = ~0.1 u in dipole to explain tune/coupling drift

Feb 20 th 2003 Pierre Bauer23 - Tevatron RunII Meeting DRIFTING a1 AND b1 IN DIPOLES? possible sources of 1u of a1 (up-down asym) & b1(left-right asym): However, all the above explains GEOMETRIC a1/b1! The only mechanism that we found to explain HYSTERETIC a1 is: up-down difference in superconductor properties (e.g. Jc)! b1 drift maybe main field decay in quads? 0.2mm0.1mm0.05mm 0.03°0.015°0.012°0.006° 0.1mm0.2mm coil roll (“cryostat- instability”) – has been addressed! “smart- bolting” should have taken care of most of these!

Feb 20 th 2003 Pierre Bauer24 - Tevatron RunII Meeting DRIFTING a1 AND b1 IN DIPOLES? Feed-down from b2 due to misalignment of dips & T:SD is most likely cause (see M. Martens talk) of most of the tune and coupling drifts; Is there drifting Production goal: zero geometric a1 and b1. TC0269 clearly shows a hysteretic and a drifting skew quadrupole: a1, b1 in the magnets? R. Hanft / G. Velev This, however, does not exclude hysteretic b2:

Feb 20 th 2003 Pierre Bauer25 - Tevatron RunII Meeting DRIFTING MAIN FIELD? ~0.5 units of main field drift in quads could explain Tev tune drift. Measuring main field decay with rotating coils is difficult, NMR is preferred technology. HERA and LHC observe dipole field drift at const excitation (note: issues related to longitudinal field variations); also: low-beta quad effects were checked (running tune drift experiments with low-beta off) – see M. Martens et al. L. Bottura et al / CERN

Feb 20 th 2003 Pierre Bauer26 - Tevatron RunII Meeting b2 DRIFT & SB FIT USED IN TEVATRON current b2 drift&SB correction was derived from magnetic measurement campaign of 96: snapback: drift: J. Annala

Feb 20 th 2003 Pierre Bauer27 - Tevatron RunII Meeting b2 DRIFT & SB FIT: CURRENT VS 96 There were, however, small modifications made to improve machine performance:

Feb 20 th 2003 Pierre Bauer28 - Tevatron RunII Meeting COMPARISON b2 FIT VS MAGNET MEASUREMENT The (relative) agreement with magnet TC 1052 is very good at t>1 min, especially for flat-top times>10 min (standard flat-top in Tev pre-cycle is 20 min).

Feb 20 th 2003 Pierre Bauer29 - Tevatron RunII Meeting b2 DRIFT&SB in RECENT MEASUREMENTS MAGNETDrift after 30 min (units) SB time (sec) TC TC TB TC TEV-fit1.256 Drift amplitude at injection (after a 30 min injection porch) and SB time after a standard pre-cycle (20 min flat-top, 1 min back-porch) as recently measured in different magnets and as calculated with Tevatron b2 compensation fit. G. Velev  t SB TC0269

Feb 20 th 2003 Pierre Bauer30 - Tevatron RunII Meeting DRIFT STARTING VALUE VARIATION b2 at start of drift is ~-1 unit to allow matching of fit with data at times t>1min + additional history dependent contribution of ~ u). Hysteretic loop is believed to be invariable, that is un- affected by powering history and (within the range of interest) more or less independent of ramp-rate. G. Velev Artifact of longitudinal field variations?

Feb 20 th 2003 Pierre Bauer31 - Tevatron RunII Meeting EXPLORING DIFFERENT SB FITS Exploring different fit algorithms for snap back: Exponential vs. polynomial fit of snap-back. Advantages of the exponential fit: 1)Less sensitive to variations in snap- back time 2)More in tune with physics (see 2 strand models) 3)Better fit? G. Velev

Feb 20 th 2003 Pierre Bauer32 - Tevatron RunII Meeting EFFECT OF DRIFT DURATION G. Velev Physics argument: the further the drift the longer the snapback time. Beam and magnet measurements show a ~constant snapback time independent of the porch duration  parabolic ramp!! Varying the injection porch time between 30 and 120 min TC0269 Drift compensation algorithm was formulated on the basis of 15 min measurements.

Feb 20 th 2003 Pierre Bauer33 - Tevatron RunII Meeting BEAM & MAGNET b2 STUDIES COMBINED There, the reconstructed b2 loop is compared to recent beam- based b2 measurements and recent magnet measurements. The magnet measurements are clearly “off” the average. This, however, is consistent with the production variations of the “width” of the loop (see error bars). Issue: single magnet vs. average of all magnets! M. Martens / M. Xiao

Feb 20 th 2003 Pierre Bauer34 - Tevatron RunII Meeting CONCLUSIONS AND OUTLOOK Increase measurement sample - more drifts and snapbacks More data on possible a1, b1 drifts in Tev dipoles Collaboration with Cern – improvement of understanding of dynamic effects in magnets Test a quadrupole for main field drift Elimination of pre-cycle? Continue to support Tevatron operation Expect further report from G. Velev on magnetic measurements soon.. No show-stopper found! Not conclusive regarding main field and a1/b1 drifts b2 compensation OK except for minor details

Feb 20 th 2003 Pierre Bauer35 - Tevatron RunII Meeting MISCELLANEOUS SLIDES

Feb 20 th 2003 Pierre Bauer36 - Tevatron RunII Meeting TEV DIPOLE – TEMPERATURE PROFILE 22 g/sec Linear heat load: ~10 W/dipole  ~25 mK / longitudinal magnet  T Issues: 1)stratification of two-phase 2)poor heat exchange betw. in/out single- phase flow  ~ 100 mK  T across coil bottom/top T. Peterson et al. 1997

Feb 20 th 2003 Pierre Bauer37 - Tevatron RunII Meeting THE TEVATRON DIPOLE – CRYO-SYSTEM J. Theilacker/A. Klebaner Heat load: 10 W/dipole  250 mK  T along magnet string), “day-to-day” temperature variations less than 50 mK. Average temperature ~ 3.9 K

Feb 20 th 2003 Pierre Bauer38 - Tevatron RunII Meeting b6, b8 & b10 PROFILES IN END* * magnetic multipoles quoted at 1 inch (=2/3 of bore radius) Note: The end multipole distribution presented here is not that of the average Tevatron dipole as defined from the production magnetic measurements. It is, however, within ~1  of the average, and therefore a realistic end.

Feb 20 th 2003 Pierre Bauer39 - Tevatron RunII Meeting AVERAGE FIELD PROFILES IN DIPOLE BODY CALCUL- ATED FROM TABUL- ATED MULTI- POLES J. Tompkins 2002

Feb 20 th 2003 Pierre Bauer40 - Tevatron RunII Meeting AVERAGE FIELD PROFILES IN DIPOLE END CALCUL- ATED FROM TABUL- ATED MULTI- POLES J. Tompkins 2002

Feb 20 th 2003 Pierre Bauer41 - Tevatron RunII Meeting TEV b2 ANALYSIS SUMMARY We can use our knowledge of the magnet properties to reconstruct approximately the “average” hysteresis loop. The loop shown here was reconstructed from the archive data and recent magnet measurements. Besides some minor issues regarding the details of the b2 compensation we found no “smoking gun”.

Feb 20 th 2003 Pierre Bauer42 - Tevatron RunII Meeting MAGNETIC FIELDS - NOMENCLATURE The following conventions are used here for the multipole expansion of the magnetic field: Complex formulation of cross-sectional fields  B y +iB x is analytical outside conductor  expansion in a Taylor series  multipole coefficients e.g. – if only b 2  0, that is a pure sextupole field:

Feb 20 th 2003 Pierre Bauer43 - Tevatron RunII Meeting TEVATRON STRING DipolesQuadsSpools Number FD Tevatron Dipole F Tevatron Quadrupole Tevatron Quad corrector Tevatron Sextupole corrector Tevatron Beam Position Monitor T:QF T:SF Horz BPM T:QD T:SD Vert BPM (There are 772 Tevatron dipoles) Courtesy - M. Martens

Feb 20 th 2003 Pierre Bauer44 - Tevatron RunII Meeting MAGNETIC MEASUREMENTS - 2