New feature to check LSA precycle to ramp

Per Hagen (TE/MSC)FiDeL Team22.03.2011

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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

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Result (what it looks like)

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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

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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”

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Definitions

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RSD1.A12B1PRECYCLE

INJECTION

RAMPÂ

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Hyst Margin

• Precycle  (%) = Precycle  / Ramp  * 100

• Hyst margin @ injection = dI (A) with same sign for dI/dt (same branch)

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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)

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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%

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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)

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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

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RQTL10.R7B1 P+R

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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

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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

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RQTF.A12B2, fill 1606PRECYCLE

INJECTION

RAMP

SQUEEZE PHYSICS

tune corrdI = 3.5A

PRECYCLE

INJECTION

RAMP

SQUEEZE PHYSICS

tune corrdI = 3.5A

invertprecycle!

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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

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Zoom 0-10 A

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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

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RSD1.A12B1, fill 1623PRECYCLE

INJECTION

tune corrdI = 3.5A

PRECYCLE

RAMP

LUMI SCAN& DUMP

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RSD1.A12B1, fill 1623

chrom corrdI ~ -2A

RAMP

SQUEEZE

Small dI corrections, few 100 mA

FLAT-TOP

chrom corrdI ~ +15A

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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)

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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)

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RCS.A12B1, fill 1623PRECYCLE

INJECTION

dI ~ 2.7.5Aduring snapback

RAMP

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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

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RCD.A12B1, fill 1623PRECYCLE

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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)

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ROF.A12B1, fill 1623DEGAUSS PRECYCLE

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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 exceeds field error• Suggestion: Switch the off the RCO circuits after a de-Gauss

• Local correctors in inner triplets not yet used (so not discussed!)