Massimo GiovannozziChamonix XV, January Electrical circuits required for the minimum workable LHC during commissioning and first two years of operation M. Giovannozzi Summary:  Introduction  Magnetic circuits: commissioning  Magnetic circuits: first two years of operation  RF circuits  Conclusions and outlook Acknowledgements: H. Burkardt, S. Fartoukh, E. Métral, F. Ruggiero, R. Saban, E. Shaposhnikova, E. Todesco, J. Tuckmantel

Massimo GiovannozziChamonix XV, January Aim: identify circuits (magnetic and RF) that are critical for the commissioning. In general it can be stated that low-order correctors are mandatory from day 1, while higher- order correctors can be delayed to a later stage. Of course, the relevance of a circuit is also a function of the beam conditions. Inspiring presentation made by O. Brüning at the 17 th LHCOP meeting. Introduction

Massimo GiovannozziChamonix XV, January From Roger’s talk

Massimo GiovannozziChamonix XV, January Trajectory- orbit From Roger’s talk Optics: tune, chromaticity RF on

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - I Orbit correctors: Arc correctors (in SSS) Insertion correctors (in special SSS, used also for crossing scheme, and near warm quadrupoles) All orbit correctors are needed from day 1

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - II Optics correctors: Tune correction Coupling correction Optics in the insertions MQT: trim quadrupoles in SSS (Q14-Q21 L/R) MQTL: long trim quadrupoles used in special SSS (Q11) to trim the insertion optics and in Q6 in IR3 and IR7 MQS: skew quadrupoles in SSS for coupling correction (Q23, Q27 L/R) All MQT and MQTL correctors are needed from day 1

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - III Coupling correction Pre-requisite for tune setting Estimate of C - without correction (S. Fartoukh 31. LCC, O. Brüning – Chamonix 2003) -> using 9901 error table for MBs The estimate did not change drastically using data from MB production. Therefore, all MQS correctors are needed from day 1

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - IV Sextupolar correctors Spool pieces: all MBs are equipped with sextupolar correctors (MCS) Contribution to chromaticity from b 3 error in MBs Correction of dynamic effects: decay and snap back Remark: 1 unit of b3 -> 45 units of Q’ Remark: specifications are (S. Fartoukh O. Brüning LHC PR 501) Q’=2±1, Q’ x =Q’ y New specs given by O. Brüning (see MAC presentation December 2004), but not substantially different Spool pieces are needed from day 1 Sector Average b 3 in MB at injection [10 -4 ] Average b 3 in MB at injection [10 -4 ] Rms b 3 in MB at injection [10 -4 ] Rms b 3 in MB at injection [10 -4 ]V1V2V1V Courtesy S. Fartoukh, MEB-107 presentation Courtesy L. Bottura

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - V Sextupolar correctors All SSS are equipped with chromaticity sextupoles (MS) Natural chromaticity is Q’ x =-93, Q’ y =-87 Correction of natural chromaticity is essential for tune measurement (decoherence)! Chromaticity sextupoles are needed from day 1 Four skew sextupoles are installed in each arc (MSS) Specification (S. Fartoukh O. Brüning LHC PR 501) based on bound on Q’’ (a 3 has no impact on dynamic aperture) a 3 (sys)=0 a 3 (sys)=0 a 3 (ran)=0.7 a 3 (ran)=0.7 a 3 (unc)=1.5 a 3 (unc)=1.5 a3(sys)= – inj a3(ran)= inj a3(sys)= coll a3(ran)= coll Courtesy E. Todesco Skew sextupoles might not be needed from day 1

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - VI Octupolar correctors Spool pieces: MBs type A are equipped with octupolar correctors (MCDO) Specification (S. Fartoukh O. Brüning LHC PR 501) based on bound on Q’’ and anharmonicity (b4 has an impact on dynamic aperture) b4(sys)=±0.2 b4(sys)=±0.2 b4(ran)=0.5 b4(ran)=0.5 b4(unc)=0.4 b4(unc)=0.4 MB-intrinsic b4 is fine. The main source of b4 comes from feed-down from MCD. Feed-down effects are nearly on specification. Remark tracking studies showed that without MCO the minimum dynamic aperture drops from 11.2  to 9.6  (see M. Hayes LHC PR 522). b4(sys)= – inj b4(ran)= inj b4(sys)= coll b4(ran)= coll Courtesy E. Todesco

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - VII Octupolar correctors Lattice octupoles: all SSS not equipped with MQT or MQS are equipped with a Landau octupole (MO) -> 168 per ring Not used at injection Used to stabilise the beams at top energy (before starting beam collisions). Under the beam conditions of the initial commissioning they should not be used However, the beam brightness is the relevant parameter (e.g. TOTEM, see E. Métral and A. Vérdier LHC PN 345) MCO might not be needed from day 1. MO are not needed from day 1, but…

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - VIII Decapolar correctors Spool pieces: MBs type A are equipped with decapolar correctors (MCDO) Specification (S. Fartoukh O. Brüning LHC PR 501) based on bound on Q’’’ and chromo-geometric detuning (b5 has an impact on dynamic aperture) Courtesy E. Todesco

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - IX A possible solution for MCO and MCD correctors would be to suppress them only in few arcs (see M. Hayes LHC PR 522). To be checked with the latest version of the LHC layout

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - X Spectrometer compensator magnets (IP2 and IP8) Since the first physics run, the spectrometers of ALICE and LHC-b will be on. Hence the three warm magnets/IP used to compensate the bump should be available from day 1

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - XI Nonlinear corrector package in the triplet quadrupoles No impact on machine performance if beta* > 1 m Not needed from day 1, but maybe MQSX and MCSX in IP2

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - XII Experimental solenoids They will not be ramped Effect negligible at top energy (see J.-P. Koutchouk et al. SL ) At injection C - ~ 5×10 -3 for the CMS solenoid (H. Burkhardt, LOC meeting) MQSX could be used to correct the coupling from solenoids -> work in progress (H. Burkhardt et al.) Vertical crossing angle in IP2 Change of polarity in spectrometer will change a2 generated from feed-down of b3. a2 correction with MQSX not possible for both beams and with MQS not effective MCSX could be used to correct the b3

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - XIII RF system (see T. Linnecar Chamonix 2005 for RF failures) Independent for each ring Two modules of 4 cavities each. Each cavity delivers 2 MV Nominal conditions: 8 MV at injection and 16 MV at top energy

Massimo GiovannozziChamonix XV, January Stage 1: initial commissioning - XIV 8 MV at injection leaves margin for beam loading from nominal beam For reduced beam intensity one might think of using only 8 MV throughout the whole cycle -> only one module would be used However: it would be wise to capture with full voltage (16 MV) during stage 1 to have maximum longitudinal acceptance (e.g. energy errors between SPS/LHC) No spare would be available and commissioned in case of problems Hence, all modules should be available from day 1

Massimo GiovannozziChamonix XV, January Stages 2 and 3 Beam conditions will approach the nominal ones. All the corrector circuits will be needed to ensure the performance No staging seems possible

Massimo GiovannozziChamonix XV, January Conclusions - I Stage 1: Circuits mandatory for day 1: Orbit correctors MQTs, MQTLs, MQS MCS, MS Spectrometer compensators All RF modules Circuits required for day 2(!): MCD (decapoles) MCO (octupoles) MQSX MCSX in IP2 MO Circuits not required for day 1: MSS Nonlinear correctors in the triplet quadrupoles Stages 2 and 3: Put in operation all the circuits still missing

Massimo GiovannozziChamonix XV, January Conclusions - II Some additional details are needed for evaluating the (beneficial) impact of reducing the number of circuits required in the various stages of LHC commissioning, namely What is the time required for the hardware commissioning of the circuits not required for day 1? Is it possible to perform the hardware commissioning in case it is found that they are actually needed? In this case what would be the time required to commission the circuits?