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New feature to check LSA precycle to ramp

New feature to check LSA precycle to ramp. Per Hagen (TE/MSC) FiDeL Team 22.03.2011. Problem. So far I have been doing checks of LSA settings w. r. t. FIDEL equations check of current w. r. t. power converter constraints

demetrius-martinez
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New feature to check LSA precycle to ramp

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  1. New feature to check LSA precycle to ramp Per Hagen (TE/MSC) FiDeL Team22.03.2011

  2. Problem • So far I have been doing checks of • LSA settings w. r. t. FIDEL equations • check of current w. r. t. power converter constraints • One thing that has not been checked is that the pre-cycle is reasonable w. r. t. the ramp • For this reason I developed a macro to characterize the precycles and ramp • I have used it on the LHC 2011 settings • GOAL: Precycle the magnets REASONABLY before the LHC bunch train

  3. Result (what it looks like)

  4. Characterisation • Look at |Imax|pre-cycle / |Imin|ramp if we excite magnet enough in the precycle • No of periods in precycle (0 = no precycle) • Want to know how many amps we have been on the same branch @ start of ramp given by: • dI/dt for end_of_precycle, start_of_ramp, and “in-between” • “in-between” = if I end_of_precycle <> I start_of_ramp an extra “ramp” takes place

  5. Further analysis • The P2R tool can be used to search for circuits with potential mismatch precycle and ramp • But further deeper analysis needed “case by case” • The following slides summaries the situation, based upon my assumptions which are stated • I use red, orange and green colour as tokens for “bad”, “questionable” and “good”

  6. Definitions • Precycle  (%) = Precycle  / Ramp  * 100 • Hyst margin @ injection = dI (A) with same sign for dI/dt (same branch)

  7. Magnets with unipolar power converter (1) • MQ : Hyst margin @ injection > 336 or 367 A, Precycle  > 100% • MQXA + MQXB : Hyst margin @ injection > 200 A, Precycle  75% or 83% • MB: Hyst margin @ injection > 600 A, Precycle  > 100% • MBRB + MBRC + MBRS + MBX: Hyst margin @ injection > 145 A, Precycle  77%to 100% • MBXW: Hyst margin @ injection = 25 A, Precycle  > 100% • MBW: Hyst margin @ injection = 1 A, Precycle  > 100% • Known issue that power converter cannot go lower than 40 A • The RESMAG component is this current region is small and should be reproducible • Assumed under control of orbit feedback (no issue)

  8. Magnets with unipolar power converter (2) • MBAW + MBLW + MBWMD + MBXWH + MBXWS + MBXWT • These are the spectrometers and “bump” compensators • Ramp to high field (outside hysteresis) prior to injection • Have a constant field during ramp and physics (so variable deflection!) • No hysteresis issues • MQWA: Hyst margin @ injection = 15 or 17 A, Precycle  > 100% • The RESMAG component is this current region is small and included in FIDEL • Assumed under control after 2010 commissioning (no issue) • MQY + MQM/C/L: Hyst margin @ injection = 34 A to 150 A, Precycle  > 100% 8

  9. Magnets with bipolar power converter (1) • MCB H/V, MCBC H/V, MCBW H/V, MCBY H/V, MCBX H/V • Hyst margin @ injection >= 0 A, Precycle  > 100% • Orbit correctors steered by orbit feedback in real-time • Some cross 0 A (change sign) during operation • Linear FiDeL model (no hysteresis) • Hysteresis in MCBX seems noticeable during lumi scans • Accept as is (cannot improve) • MQTLH: Hyst margin @ injection > 200 A, Precycle  > 100% • Magnets used as Q6 in cleaning regions at 4.5 K • No hysteresis in FiDeL model • Hysteresis at I inj = 14 to 15 A around 10 units (no issue) • MQWB: Hyst margin @ injection > 570 A, Precycle  > 100% • The RESMAG component is this current region is big and included in FIDEL • Assumed under control after 2010 commissioning (no issue) 9 9

  10. Magnets with bipolar power converter (2) • MQTLI: Hyst margin @ injection = 0 A to 310 A, Precycle  > 100% • Hysteresis at 10 A around 100 units • No hysteresis in FiDeL model • Some operate as low as 0.2 A at injection • Always located next to a much stronger MQ (“in the shadow”) • Has it own optics functions (K-values) • Some MQTL11 circuits cross 0 A during squeeze • Use FiDeL model as is (cannot improve due to squeeze) • The circuits having the wrong “current sign” in the precycle could be corrected to improve reproducibility 10 10 10

  11. Magnets with bipolar power converter (3) • MQT general • Hysteresis at 5 A around 200 units • No hysteresis in FiDeL model • MQT12 and MQT13 : Hyst margin @ injection = 0 A to 314 A, Precycle  > 125% • Some operate as low as 0.3 A at injection, 2 circuits with a few mA • Always located next to a much stronger MQ (“in the shadow”) • Has it own optics functions (K-values) • Many cross 0 A at least once during squeeze • Use FiDeL model as is (cannot improve due to squeeze) • The circuits having the wrong “current sign” in the precycle could be changed to improve reproducibility

  12. Magnets with bipolar power converter (4) • MQT in RQTF and RQTD circuits ( F/D x 8 sectors x 2 beams) • Serve 2 purposes: trim tune and correct known MB b2 • Correctors steered by tune feedback in real-time • Hyst margin @ injection > 4 A, Precycle  > 300% • |I|min = 3.7 A and |I| ave = 6.3 A at injection, considering ONLY MB b2 • Current for MB b2 correction much stronger than trim of tune (TIMBER) • Use FiDeL model as is (hysteresis reduced during ramp) • The circuits having the wrong “current sign” in the precycle could be corrected to improve reproducibility 12

  13. Magnets with bipolar power converter (5) • MS (F/D x “1 & 2” x 8 arcs x two beams = 64 circuits) • Chromaticity: Correct natural Q’ of +85 and define desired one (~ +4 to +10) • Hysteresis ~ 4.5% @ 10 A • RSD operate from 8.3 A (injection) to 83 A (end of ramp) • RSF operate from 5.5 A (injection) to 46 A (end of ramp) • Hyst margin 196 A, Precycle  > 200% • DCMAG hysteresis recently added to FiDeL model Zoom 0-10 A

  14. Magnets with bipolar power converter (6) • The MS circuits are believed to be on the correct hysteresis branch after pre-cycle and until end of ramp. • The Q’ corrections after flat-top might change the hysteresis branch, but the effect will be from 0.5% to 1% due to the stronger currents

  15. Magnets with bipolar power converter (7) • MQS ( 8 arcs + 8 “L” of IP + 8 “R” of IP = 24 circuits) • Serve 2 purposes: reduce linear coupling and correct known MB a2 • Correctors steered by coupling feedback in real-time • Hyst margin @ injection from 0 A to 380 A, Precycle  > 500% • Current for MB a2 correction stronger than trim of tune (TIMBER) • Many circuits cross 0 A during ramp • Use FiDeL model as is (cannot improve) • Use precycle as is (cannot improve) • MSS (8 arcs x two beams = 16 circuits) • Corrects MB a3 • Hysteresis ~ 4.5% @ 10 A • Circuits operate from 0.2 A (injection) to 10 A (end of ramp) • Hyst margin 0 A for 14 circuits, 48 A for 2, Precycle  > 4000% • Corrects small effect (no need for improving) 15 15

  16. Magnets with bipolar power converter (8) • MCS • Correct known MB b3 (undesired chromaticity) • Hysteresis 1.5% @ 20 A • Hyst margin @ injection from 300 A to 380 A, Precycle  > 600% • Warning: dI/dt changes sign during snapback (probably OK) • Warning: Cross 0 during ramp! • FiDeL model without hysteresis (cannot improve)

  17. Magnets with bipolar power converter (9) • MCD • Correct known MB b5 • Hysteresis 1% @ 10 A • But operates with |I| > 100 A @ injection (insignificant hysteresis) • Most of the circuits cross 0 A during ramp • FiDeL model without hysteresis (cannot improve) • Precycle OK as is

  18. Magnets with bipolar power converter (10) • MO • Reduce beam emittance growth during long physics run by adding decoherence (Landau damping) • The MO must have 0-field during injection so a special de-Gauss precycle is used to minimize the remanent field • dI/dt does not change during ramp (so no cross of 0A) • FiDeL model without hysteresis (correct with de-Gauss precycle)

  19. Magnets with bipolar power converter (11) • MCO • Correct known MB b4 which is a small systematic effect • No precycle because nested and MCD is outside (cross-talk) • Hysteresis > 40% @ 6 A (extrapolated) • Operates @ injection from 0.5 A to 5.5 A • Warning: Precycle cannot be well defined! • Warning: Hysteresis exceedsfielderror • Suggestion: Switch the off the RCO circuits after a de-Gauss • Local correctors in inner triplets not yet used (so not discussed!)

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